INVITED ARTICLE
Surgical Treatment of Hypertrophic Cardiomyopathy Sameh M. Said, MD, and Hartzell V. Schaff, MD Hypertrophic cardiomyopathy (HCM) is a unique primary myocardial disease characterized by unexplained left ventricular hypertrophy in absence of another etiology. One of the key features is the presence of systolic anterior motion of the anterior leaflet of the mitral valve which causes left ventricular outflow tract obstruction with various degrees of mitral valve regurgitation. Surgical septal myectomy is the preferred treatment of choice if medical treatment is unsuccessful or intolerable. We summarize in this review the available treatment options for HCM. Semin Thoracic Surg 25:300–309 I 2014 Elsevier Inc. All rights reserved. Keywords: hypertrophic cardiomyopathy, septal myectomy, apical myectomy
INTRODUCTION Hypertrophic cardiomyopathy (HCM), previously known as idiopathic hypertrophic subaortic stenosis, is a unique primary myocardial disease characterized by unexplained left ventricular hypertrophy, that is, hypertrophy in the absence of another etiology such as aortic valve stenosis or systemic arterial hypertension. HCM is associated with a variety of presentations that range from being asymptomatic to sudden cardiac death. The main morphologic variants are the basal, midventricular, apical, and diffuse types (Fig. 1). The key pathophysiology in obstructive HCM is systolic anterior motion (SAM) of the anterior leaflet of the mitral valve, which causes left ventricular outflow tract (LVOT) obstruction and may lead to various degrees of mitral valve regurgitation, which further adds to the symptomatology. Medical treatment is the first-line therapy for symptomatic patients with LVOT obstruction1; however extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable.2 In this review, we summarize the current surgical treatment and outcomes of septal myectomy in HCM.
Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, Rochester, Minnesota Address reprint requests to Hartzell V. Schaff, MD, Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail: [email protected]
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HISTORICAL BACKGROUND The first pathologic case reports by Brock and Teare in 1958 drew attention to HCM as a clinical entity with significant morbidity and mortality. Early surgical experience with HCM began with relief of LVOT obstruction through simple incision in the bulging basal septum that can be deepened further with the surgeon0 s finger (myotomy) or an actual muscle excision under direct vision (myectomy).3 The description of a limited transaortic septal myectomy given by Cleland et al in 1958 is considered the first surgical procedure for obstructive HCM.4 In 1960, Morrow and Brockenbrough5 performed a transaortic myotomy or myectomy, which became known as the “Morrow operation.” Historically, mitral valve replacement was the main technique to eliminate SAM; however, with adequate septal myectomy, SAM-mediated mitral regurgitation is eliminated and the mitral valve can be preserved in almost all circumstances. The indication for mitral valve replacement is now limited to those few patients with intrinsic mitral valve disease not amenable to repair (eg, rheumatic mitral stenosis and regurgitation). The traditional surgical approach for basal HCM is the transaortic approach, but occasionally this approach is not suitable for the midventricular or apical variants and remains a bit of a challenge when the aortic annulus is small. CURRENT INDICATIONS FOR SEPTAL MYECTOMY The standard indications for septal myectomy are symptoms refractory to medical treatment 1043-0679/$-see front matter ª 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.semtcvs.2014.01.001
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Figure 1. (A) A normal heart and the different morphologic types of hypertrophic cardiomyopathy: (B) basal, (C) midventricular, and (D) apical. © 2012 Wiley Periodicals, Inc.
combined with severe LVOT obstruction with resting gradient of more than 30 mm Hg; however, the current indications have expanded recently to
include symptomatic patients with low resting outflow gradients and latent obstruction. Further, our experience suggests that a subgroup of patients
Figure 2. A hockey-stick aortotomy is made and carried down toward the middle of the noncoronary sinus (dashed line). The aortotomy is carried to within 1.0 cm of the aortic annulus. This incision is made slightly closer to the sinotubular ridge than is usual for aortic valve replacement. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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Figure 3. A standard No. 10 scalpel blade is used for incision in the septum that begins just to the right of the nadir of the right aortic sinus and extends leftward toward the mitral valve. Any incision made at the base of the ventricular septum more rightward than the nadir of the right cusp would injure the membranous septum and conduction tissue and result in complete heart block. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
with favorable septal anatomy have especially favorable outcomes and might be considered for operation without a prolonged trial of medical treatment.6
EXTENDED LEFT VENTRICULAR SEPTAL MYECTOMY Extended left ventricular septal myectomy is the standard treatment for symptomatic patients with
Figure 4. The area of septal excision is completed with the scissors flush against the posterior free wall (white dotted line). It is then deepened and lengthened toward the apex of the heart (incision 2 in the inset) being certain to excise hypertrophied septum beyond endocardial scar at the midventricular level. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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Figure 5. The completed myectomy usually extends from the subaortic level to the midventricular level, opposite to the base of the anterior papillary muscle of the mitral valve to eliminate any left ventricular outflow gradient. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
obstructive HCM; however, there is a definite learning curve with this procedure to avoid the major technical complications such as complete heart block, ventricular septal defect, or injury to the aortic or mitral valves or both. The method we employ has evolved over the last 3 decades and differs from the classic Morrow myectomy. Our technique has been described previously.7 An important principle with the transaortic myectomy is adequate exposure of the subaortic septum through an oblique hockey-stick–shaped aortotomy that is made slightly closer to the sinotubular ridge than used for standard aortic valve replacement (Fig. 2). The first incision in the interventricular septum begins just to the right of the nadir of the right aortic sinus and is made upward and then leftward over to the anterior leaflet of the mitral valve (Fig. 3). Scissors are then used to complete excision of this initial portion of myocardium (Fig. 4). The area of septal excision is then deepened and lengthened toward the apex of the heart, being certain to excise the hypertrophied septum beyond the endocardial scar (Fig. 5). The main differences between our extended septal myectomy and the classic Morrow myectomy are the width and distal extent of the myectomy. We prefer a wider initial septal excision that extends leftward to the anterior mitral leaflet; this improves exposure within the ventricle. Septal excision is then extended apically in the ventricle beyond the endocardial scar and would, in most patients, reach the level of the papillary muscle. With the extended myectomy, the
wider excision of muscle in the immediate subaortic area improves exposure of the distal extent of the hypertrophied septum, and the excision extends up to 5 cm from the aortic valve. Lesser myectomy shifts the level of obstruction further down into the ventricle and symptoms may persist. With adequate septal myectomy and elimination of SAM, outflow tract obstruction and associated mitral regurgitation are relieved. In our experience, subaortic obstruction due to SAM can always be relieved by adequate transaortic septal myectomy, and treatment with alternate methods such as mitral valve replacement, transmitral myectomy, and mitral leaflet shortening is not necessary. MIDVENTRICULAR VARIANT Midventricular obstruction is less common than subaortic obstruction, and there has been confusion regarding the importance of gradients in producing symptoms. By definition, the level of obstruction is in the midventricle, which is difficult to address through the transaortic approach. Midventricular obstruction has a different pathophysiologic mechanism and, in fact, may have a worse prognosis than other variants of HCM. The obstruction is caused by systolic narrowing of the midventricle because of apposition between the septum and the papillary muscles. Secondary mitral regurgitation is uncommon. Preoperatively, the key echocardiographic feature in establishing the diagnosis is a midcavitary
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY gradient in the absence of SAM of the mitral valve. In addition, there is an open apical chamber, and obstruction at the midcavity does not produce complete systolic obliteration of the cavity. In many patients, the decision for myectomy in those with midventricular obstruction is made difficult because of uncertainty whether symptoms of dyspnea and angina are related to the midcavitary gradient or diastolic dysfunction caused by left ventricular hypertrophy. As is true for subaortic myectomy for obstructive HCM, a complete myectomy is important to relieve midventricular muscular obstruction. The transapical approach is preferred for relief of midventricular obstruction, and some patients have both subaortic obstruction due to basal septal hypertrophy and SAM as well as midventricular obstruction. For patients with obstruction at both levels, we would use both the transaortic and the transapical incisions. Commonly, an endocardial scar is seen on the septum in the area of apposition with the papillary muscles. APICAL MYECTOMY Apical HCM is a unique variant of HCM in which ventricular hypertrophy is localized mainly at the
apex and distal ventricle. Severe degrees of apical hypertrophy can produce a small left ventricular cavity and symptoms of low cardiac output due to diastolic dysfunction. The key features are small left ventricular cavity and the absence of SAM. Treatment options in highly symptomatic patients are very limited and the only other alternative to heart transplantation is a ventricular enlargement procedure, which can be achieved through an apical myectomy. The procedure to augment left ventricular cavity size is performed through a transapical approach and has been described previously. The main principle is to identify the left anterior descending coronary artery, which serves as the surgical landmark for the apical incision, and then a small apical ventriculotomy is made parallel and lateral to it (Fig. 6). Myectomy is begun along the septum with care to avoid injury to the mitral valve apparatus (Fig. 7). Additional muscular resection along the free wall can be performed, and in some patients, the anterolateral and posteromedial papillary muscles can be shaved to further improve diastolic filling. In apical HCM, the hypertrophied muscle usually obliterates the left ventricular apex, and papillary muscles are displaced apically. The resection removes the mass of the myocardium occupying the left ventricular apex,
Figure 6. The left anterior descending coronary artery (LAD) is identified, and an apical ventriculotomy is made lateral to it. This incision is located over the apical dimple (*) when one is present (apical pouch), and it should be situated far enough to the left of the LAD to allow secure closure of the ventricle without compromising the vessel. LV, left ventricle. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) 304
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Figure 7. Myectomy is performed removing septal muscle using a No. 10-blade knife and scissors with the aid of small Volkmann retractors. The main focus of the procedure is on the ventricular septum with limited shaving done on the LV free wall (dashed line in the inset). It is important to avoid excessive myectomy adjacent to the ventriculotomy. LV, left ventricle. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
Figure 8. Adequate augmentation of the left ventricular cavity can be achieved with adequate myectomy. Final inspection is performed to ensure there has been no injury to the mitral valve or its subvalvular components. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY thus augmentation of the left ventricular cavity is achieved (Fig. 8). CONCOMITANT MITRAL VALVE SURGERY Concomitant structural mitral valve abnormalities in the setting of HCM require special attention. In our experience, mitral valve replacement is reserved for patients with intrinsic leaflet abnormalities that cannot be repaired. Mitral valve repair techniques need to be modified when concomitant myectomy is performed. Our approaches for mitral valve repair include resection of the posterior leaflet in the presence of leaflet prolapse or ruptured chord and use of artificial chordae for unsupported anterior leaflet abnormalities. The use of posterior flexible posterior annuloplasty band is individualized and if a band is to be used, we generally select 1 size larger so as to minimize the potential development of SAM after the repair. We previously detailed 32 patients with obstructive HCM and intrinsic mitral valve disease who underwent concomitant septal myectomy and mitral valve repair or replacement. Among the 28 patients who required mitral valvuloplasty, 10 (36%) had leaflet resection, 6 (21%) had repair with an edge-to-edge stitch, and 8 (29%) had leaflet plication; the remaining patients had annuloplasty alone. An annuloplasty ring/band was
used in 19 (68%) and commissural annuloplasty in 2 (7%) patients. At late follow-up, LVOT gradient and SAM resolved in all patients.8 ALTERNATIVE APPROACHES TO TRANSAORTIC SEPTAL MYECTOMY Mobilization of the Fibrous Trigones This technique was described by Yacoub et al and is based on the role played by both the right and left fibrous trigones in the functional anatomy of the normal and diseased LVOT. The authors proposed that LVOT obstruction is due to the presence of a complete fibromuscular ring in the LVOT connecting both fibrous trigones together and this needs to be excised completely with adequate mobilization of both trigones to completely relieve the LVOT obstruction whether it is dynamic or fixed or both.9 Exposure is obtained through an aortotomy. The aortic valve is inspected and any commisural fusion is divided; next the subaortic area is inspected and any subaortic membrane is removed. A vertical incision is made in the septum starting just below the right and middle thirds of the base of the right coronary cusp and extending deep into the ventricle to the level of anterior papillary muscle of the mitral valve. A fibromuscular wedge of tissue is then
Figure 9. This figure demonstrates an example of an accessory papillary muscle that arises from the ventricular septum and is attached to the side of the anterior leaflet. This accessory muscle is excised in its entirety. The fibrous attachments to the side of the leaflet are cut and the papillary muscle is amputated at its base and removed (dotted line). Importantly, chordal attachments to the leading edge of the anterior leaflet are preserved. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY excised toward the left fibrous trigone. The left trigone is then mobilized by extending the incision laterally to open the hinge mechanism between the septum and the subaortic curtain. Any bridging tissue between the mitral leaflet and the septum is also excised. The right fibrous trigone is also mobilized by excision of the wedge of abnormal tissue in the angle between the membranous septum and subaortic curtain. We have no experience with this procedure in patients with obstructive HCM but have used similar methods in patients with congenital subaortic obstruction with membranous and varying degrees of muscular obstruction. Transmitral Myectomy A left atrial approach to septal myectomy has been described as an alternative to the standard transaortic procedure.10 Our experience with this method is limited to the pediatric population as the transaortic approach may be challenging in the presence of small aortic valve annulus. An added advantage for the left atrial approach is the ability to address concomitant mitral valve abnormalities and myectomy through a single incision. ADJUNCTS TO SEPTAL MYECTOMY Papillary Muscle Abnormalities Abnormalities of the mitral valve apparatus can exist in some patients with HCM, and may contribute to persistent LVOT gradient if they are not recognized and treated at the time of initial myectomy.11 Anomalous papillary muscle insertion into the anterior mitral leaflet is a well-recognized entity, and its diagnosis is not infrequently missed on preoperative echocardiography. Management of the anomalous papillary muscle depends on its insertion into the mitral leaflet. If it is attached to the free edge of the leaflet, we tend to leave it as a resection in this situation may compromise the competency of the mitral valve, however; if it inserts into the body of the anterior leaflet, it can be excised safely (Fig. 9). Surgical Treatment of Atrial Fibrillation Patients with HCM are at increased risk of atrial fibrillation (AF) because of the long-standing increase in the left ventricular end-diastolic and left atrial pressures. Our current strategy is to perform concomitant AF surgery, primarily pulmonary vein isolation, with septal myectomy for most patients who have AF preoperatively. Early results have demonstrated the feasibility of such an approach with no added risk and improved maintenance of
sinus rhythm.12 The choice of type of maze procedure to be performed is controversial. In general, pulmonary vein isolation is more suitable for those with paroxysmal AF, but for patients who are highly symptomatic with AF and have continuous AF with severely enlarged left atria, we prefer the biatrial Cox maze III (cut and sew) procedure. ALCOHOL SEPTAL ABLATION Septal Ablation vs Septal Myectomy Although septal myectomy is considered the treatment of choice for patients with an obstructive variant of HCM who require septal reduction, alcohol septal ablation (infarction) has emerged as an alternative to surgery.13 Alcohol septal ablation can decrease the LVOT gradient and improve symptoms, but comparative studies tend to support septal myectomy for better long-term symptom relief. When a myectomy is performed in experienced centers, the procedure success rate is higher and the complication rate is lower.14 In a review of 138 patients who underwent alcohol septal ablation at Mayo Clinic between 1998 and 2006, mortality and morbidity of this procedure were higher than that of an age- and gender-matched population who underwent septal myectomy.15 Septal myectomy in patients aged 65 years or younger also had significantly better survival, free of death and severe symptoms (P ¼ 0.01). Patients who might be good candidates for septal reduction by alcohol ablation primarily include older patients with favorable coronary anatomy and associated clinical conditions that would preclude safe operation. Alcohol septal ablation seems ill advised in certain subsets of patients with HCM including young patients, those with severe (diffuse) or relatively thin septal thickness, and very high LVOT gradient. Other major advantages of septal myectomy over alcohol septal ablation are the immediate reduction of the LVOT gradient16 and the possibility of addressing other abnormalities of the outflow tract, especially abnormalities of the mitral valve and anomalous papillary muscles that can also contribute to dynamic outflow tract obstruction. The fact that up to 10% of patients with the presumptive diagnosis of obstructive HCM referred to specialized centers have fixed subaortic obstruction and would not be expected to respond to alcohol septal ablation is often overlooked. Septal Myectomy After Alcohol Septal Ablation An increasing number of patients may present with recurrent symptoms secondary to persistent
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY outflow tract obstruction following septal artery ablation that may require reintervention, and 2 points deserve comment.17 First, alcohol septal infarction frequently results in a right bundle branch block, and left bundle branch block often follows septal myectomy. So when septal myectomy is performed after unsuccessful alcohol ablation, permanent pacing is required in a high percentage of patients. A second consideration is patient survival. Among 40 patients who underwent myectomy following alcohol septal ablation, early mortality and perioperative morbidity greater than expected for patients having septal myectomy as a primary procedure.18 RECURRENT OBSTRUCTION AFTER SEPTAL MYECTOMY A small group of patients experience recurrence of their symptoms and LVOT obstruction after previous septal myectomy. In our experience, this occurs most often because of incomplete myectomy at the initial operation rather than recurrent muscle growth. Recurrent obstruction due to muscle regrowth is a potential problem in patients with congenital subaortic obstruction (membranous or tunnel subaortic obstruction or both), but in these patients the subaortic obstruction is fixed and not related to SAM of the mitral valve. Our experience with redo myectomy now includes more than 50 patients. We have identified the following mechanisms for recurrence of left ventricular outflow tract obstruction (LVOTO): limited initial myectomy, septal hypertrophy at the midventricular level, and the pre-existence of an anomalous papillary muscle.19 From our experience, repeat septal myectomy is safe and feasible and should be offered to symptomatic patients with dynamic outflow tract obstruction. LATENT OBSTRUCTION Patients with HCM may be symptomatic in the presence of low resting LVOT gradients, and the clinical dilemma is whether symptoms are due to diastolic dysfunction or a labile outflow tract gradient. The key feature is to evaluate the LVOT gradient at rest and with the use of provocative maneuvers such as exercise testing, Valsalva, or amyl nitrite inhalation during Doppler echocardiography. To better understand the role of septal myectomy in patients with low resting gradients, we reviewed our experience with 249 patients with latent obstruction (gradient o30 mm Hg at rest) but with evidence of severe LVOTO when provoked by Valsalva maneuver or amyl nitrite inhalation. This group was compared with those who had severe resting gradients (430 mm Hg) and underwent septal myectomy during the same
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time period. Early mortality was similarly low (1%) and long-term survival was comparable to that of an agematched population.20 Most importantly, patients with latent obstruction had similar functional improvement after myectomy as those with high resting gradients. We believe, therefore, that in patients with labile obstruction and low resting gradients, symptoms may often be related to a latent form of obstruction rather than diastolic dysfunction, and septal myectomy should be considered. MAYO CLINIC EXPERIENCE More than 2200 patients have had septal myectomy for HCM at the Mayo Clinic. Risk of hospital death after isolated septal myectomy for obstructive HCM is o1% and is similar to the risk of operation for elective mitral valve repair. Complications, such as complete heart block requiring permanent pacemaker and iatrogenic ventricular septal perforation, are uncommon (2%), although partial or complete left bundle branch block is a frequent finding on the postoperative ECG. Usually, this is not associated with adverse sequelae, but if the patient has complete right bundle branch block preoperatively, the left bundle branch block after myectomy increases the risk of complete heart block and the need for permanent pacing. This is particularly important in patients who have had alcohol septal ablation preoperatively, which leads to right bundle branch block in up to 60% of patients.21 Relief of LVOT obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM. Approximately 90% of severely symptomatic patients have improvement of at least 2 function classes, and relief of outflow gradients by myectomy is equally effective in improving limitations because of dyspnea, angina, or syncope.22 Importantly, symptomatic benefit of myectomy is related directly to reduction in the basal outflow tract obstruction, mitral regurgitation, and improvement in left ventricular systolic and enddiastolic pressures (in more than 90% of patients), which in turn may also favorably influence myocardial ischemia. Relief of the gradient may decrease left atrial size and the subsequent risk of developing AF. Importantly, the late survival of HCM patients who have had septal myectomy is equivalent to an agematched population and the risk of appropriate implantable cardioverter defibrillator (ICD) discharges decreases significantly after abolishment of the gradient. We have used the transapical approach in a total of 115 patients with midventricular and apical variants of HCM between 1993 and 2012. All patients with midventricular obstruction (n ¼ 55)
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1. Gersh BJ, Maron BJ, Bonow RO, et al: 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. American College of Cardiology Foundation/American Heart Association Task Force on Practice; American Association for Thoracic Surgery; American Society of Echocardiography; American Society of Nuclear Cardiology; Heart Failure Society of America; Heart Rhythm Society; Society for Cardiovascular Angiography and Interventions; Society of Thoracic Surgeons. J Thorac Cardiovasc Surg 142(6):e153-e203, 2011 2. Nishimura RA, Giuliani ER, Brandenburg RO, et al: Hypertrophic cardiomyopathy. In: Giuliani ER, Gersh BJ, McGoon MD, Hayes DL, Schaff HV, editors. Myocardial Disease: Mayo Clinic Practice of Cardiology, 3rd ed. St. Louis, MO: Mosby-Year Book; 1996. p. 689-711, 1996 [Chapter 20] 3. Kirklin JW, Ellis Jr FH: Surgical relief of diffuse subvalvular aortic stenosis. Circulation 24: 739-742, 1961 4. Goodwin JF, Hollman A, Cleland WP, et al: Obstructive cardiomyopathy simulating aortic stenosis. Br Heart J 22:403-414, 1960 5. Morrow AG, Brockenbrough EC: Surgical treatment of idiopathic hypertrophic subaortic stenosis: Technique and hemodynamic results of subaortic ventriculomyotomy. Ann Surg 154:181-189, 1961 6. Said SM, Dearani JA, Ommen SR, et al: Surgical treatment of hypertrophic cardiomyopathy. Expert Rev Cardiovasc Ther 11(5):617-627, 2013 7. Schaff HV, Said SM: Transaortic extended septal myectomy for hypertrophic cardiomyopathy. Oper Tech Thorac Cardiovasc Surg 17 (4):238-250, 2012
akinesis, but this is relatively small and does not lead to significant systolic dysfunction. Indeed, in patients with apical HCM, the apex is obliterated with muscle and does not contribute to left ventricle stroke volume.23
8. Wan CK, Dearani JA, Sundt 3rd TM, et al: What is the best surgical treatment for obstructive hypertrophic cardiomyopathy and degenerative mitral regurgitation? Ann Thorac Surg 88(3): 727-731, 2009 [discussion 731-2] 9. Yacoub M, Onuzo O, Riedel B, et al: Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction. J Thorac Cardiovasc Surg 117(1):126-132, 1999 [discussion 32-3] 10. Matsuda H, Nomura F, Kadoba K, et al: Transatrial and transmitral approach for left ventricular myectomy and mitral valve plication for diffuse-type hypertrophic obstructive cardiomyopathy: A novel approach. J Thorac Cardiovasc Surg 112(1):195-196, 1996 11. Klues HG, Roberts WC, Maron BJ: Anomalous insertion of papillary muscle directly into anterior mitral leaflet in hypertrophic cardiomyopathy; Significance in producing left ventricular outflow tract obstruction. Circulation 84:1188-1197, 1991 12. Chen MS, McCarthy PM, Lever HM, et al: Effectiveness of atrial fibrillation surgery in patients with hypertrophic cardiomyopathy. Am J Cardiol 93(3):373-375, 2004 13. Lakkis NM, Nagueh SF, Dunn JK, et al: Nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy: One-year follow-up. J Am Coll Cardiol 36(3):852-855, 2000 14. Maron BJ: Controversies in cardiovascular medicine. Surgical myectomy remains the primary treatment option for severely symptomatic patients with obstructive hypertrophic cardiomyopathy. Circulation 116(2):196-206, 2007 15. Sorajja P, Valeti U, Nishimura RA, et al: Outcome of alcohol septal ablation for obstructive hypertrophic cardiomyopathy. Circulation 118 (2):131-139, 2008
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16. Maron BJ: Commentary and re-appraisal: Surgical septal myectomy vs. alcohol ablation: After a decade of controversy and mismatch between clinical practice and guidelines. Prog Cardiovasc Dis 54(6):523-528, 2012 17. Chang SM, Lakkis NM, Franklin J, et al: Predictors of outcome after alcohol septal ablation therapy in patients with hypertrophic obstructive cardiomyopathy. Circulation 109 (7):824-827, 2004 18. ElBardissi AW, Dearani JA, Nishimura RA, et al: Septal myectomy after previous septal artery ablation in hypertrophic cardiomyopathy. Mayo Clin Proc 82(12):1516-1522, 2007 19. Minakata K, Dearani JA, Schaff HV, et al: Mechanisms for recurrent left ventricular outflow tract obstruction after septal myectomy for obstructive hypertrophic cardiomyopathy. Ann Thorac Surg 80(3):851-856, 2005 20. Schaff HV, Dearani JA, Ommen SR, et al: Expanding the indications for septal myectomy in patients with hypertrophic cardiomyopathy: Results of operation in patients with latent obstruction. J Thorac Cardiovasc Surg 143(2): 303-309, 2012 [Epub 2011 Dec 10] 21. McCann GP, Van Dockum WG, Beek AM, et al: Extent of myocardial infarction and reverse remodeling assessed by cardiac magnetic resonance in patients with and without right bundle branch block following alcohol septal ablation for obstructive hypertrophic cardiomyopathy. Am J Cardiol 99:563-567, 2007 22. McCully RB, Nishimura RA, Tajik AJ, et al: Extent of clinical improvement after surgical treatment of hypertrophic obstructive cardiomyopathy. Circulation 467-471 23. Said SM, Schaff HV, Abel MD, et al: Transapical approach for apical myectomy and relief of midventricular obstruction in hypertrophic cardiomyopathy. J Card Surg 27(4):443-448, 2012 [Epub 2012 May 29]
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Surgical Treatment of Hypertrophic Cardiomyopathy Sameh M. Said, MD, and Hartzell V. Schaff, MD Hypertrophic cardiomyopathy (HCM) is a unique primary myocardial disease characterized by unexplained left ventricular hypertrophy in absence of another etiology. One of the key features is the presence of systolic anterior motion of the anterior leaflet of the mitral valve which causes left ventricular outflow tract obstruction with various degrees of mitral valve regurgitation. Surgical septal myectomy is the preferred treatment of choice if medical treatment is unsuccessful or intolerable. We summarize in this review the available treatment options for HCM. Semin Thoracic Surg 25:300–309 I 2014 Elsevier Inc. All rights reserved. Keywords: hypertrophic cardiomyopathy, septal myectomy, apical myectomy
INTRODUCTION Hypertrophic cardiomyopathy (HCM), previously known as idiopathic hypertrophic subaortic stenosis, is a unique primary myocardial disease characterized by unexplained left ventricular hypertrophy, that is, hypertrophy in the absence of another etiology such as aortic valve stenosis or systemic arterial hypertension. HCM is associated with a variety of presentations that range from being asymptomatic to sudden cardiac death. The main morphologic variants are the basal, midventricular, apical, and diffuse types (Fig. 1). The key pathophysiology in obstructive HCM is systolic anterior motion (SAM) of the anterior leaflet of the mitral valve, which causes left ventricular outflow tract (LVOT) obstruction and may lead to various degrees of mitral valve regurgitation, which further adds to the symptomatology. Medical treatment is the first-line therapy for symptomatic patients with LVOT obstruction1; however extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable.2 In this review, we summarize the current surgical treatment and outcomes of septal myectomy in HCM.
Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, Rochester, Minnesota Address reprint requests to Hartzell V. Schaff, MD, Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail: [email protected]
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HISTORICAL BACKGROUND The first pathologic case reports by Brock and Teare in 1958 drew attention to HCM as a clinical entity with significant morbidity and mortality. Early surgical experience with HCM began with relief of LVOT obstruction through simple incision in the bulging basal septum that can be deepened further with the surgeon0 s finger (myotomy) or an actual muscle excision under direct vision (myectomy).3 The description of a limited transaortic septal myectomy given by Cleland et al in 1958 is considered the first surgical procedure for obstructive HCM.4 In 1960, Morrow and Brockenbrough5 performed a transaortic myotomy or myectomy, which became known as the “Morrow operation.” Historically, mitral valve replacement was the main technique to eliminate SAM; however, with adequate septal myectomy, SAM-mediated mitral regurgitation is eliminated and the mitral valve can be preserved in almost all circumstances. The indication for mitral valve replacement is now limited to those few patients with intrinsic mitral valve disease not amenable to repair (eg, rheumatic mitral stenosis and regurgitation). The traditional surgical approach for basal HCM is the transaortic approach, but occasionally this approach is not suitable for the midventricular or apical variants and remains a bit of a challenge when the aortic annulus is small. CURRENT INDICATIONS FOR SEPTAL MYECTOMY The standard indications for septal myectomy are symptoms refractory to medical treatment 1043-0679/$-see front matter ª 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.semtcvs.2014.01.001
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Figure 1. (A) A normal heart and the different morphologic types of hypertrophic cardiomyopathy: (B) basal, (C) midventricular, and (D) apical. © 2012 Wiley Periodicals, Inc.
combined with severe LVOT obstruction with resting gradient of more than 30 mm Hg; however, the current indications have expanded recently to
include symptomatic patients with low resting outflow gradients and latent obstruction. Further, our experience suggests that a subgroup of patients
Figure 2. A hockey-stick aortotomy is made and carried down toward the middle of the noncoronary sinus (dashed line). The aortotomy is carried to within 1.0 cm of the aortic annulus. This incision is made slightly closer to the sinotubular ridge than is usual for aortic valve replacement. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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Figure 3. A standard No. 10 scalpel blade is used for incision in the septum that begins just to the right of the nadir of the right aortic sinus and extends leftward toward the mitral valve. Any incision made at the base of the ventricular septum more rightward than the nadir of the right cusp would injure the membranous septum and conduction tissue and result in complete heart block. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
with favorable septal anatomy have especially favorable outcomes and might be considered for operation without a prolonged trial of medical treatment.6
EXTENDED LEFT VENTRICULAR SEPTAL MYECTOMY Extended left ventricular septal myectomy is the standard treatment for symptomatic patients with
Figure 4. The area of septal excision is completed with the scissors flush against the posterior free wall (white dotted line). It is then deepened and lengthened toward the apex of the heart (incision 2 in the inset) being certain to excise hypertrophied septum beyond endocardial scar at the midventricular level. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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Figure 5. The completed myectomy usually extends from the subaortic level to the midventricular level, opposite to the base of the anterior papillary muscle of the mitral valve to eliminate any left ventricular outflow gradient. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
obstructive HCM; however, there is a definite learning curve with this procedure to avoid the major technical complications such as complete heart block, ventricular septal defect, or injury to the aortic or mitral valves or both. The method we employ has evolved over the last 3 decades and differs from the classic Morrow myectomy. Our technique has been described previously.7 An important principle with the transaortic myectomy is adequate exposure of the subaortic septum through an oblique hockey-stick–shaped aortotomy that is made slightly closer to the sinotubular ridge than used for standard aortic valve replacement (Fig. 2). The first incision in the interventricular septum begins just to the right of the nadir of the right aortic sinus and is made upward and then leftward over to the anterior leaflet of the mitral valve (Fig. 3). Scissors are then used to complete excision of this initial portion of myocardium (Fig. 4). The area of septal excision is then deepened and lengthened toward the apex of the heart, being certain to excise the hypertrophied septum beyond the endocardial scar (Fig. 5). The main differences between our extended septal myectomy and the classic Morrow myectomy are the width and distal extent of the myectomy. We prefer a wider initial septal excision that extends leftward to the anterior mitral leaflet; this improves exposure within the ventricle. Septal excision is then extended apically in the ventricle beyond the endocardial scar and would, in most patients, reach the level of the papillary muscle. With the extended myectomy, the
wider excision of muscle in the immediate subaortic area improves exposure of the distal extent of the hypertrophied septum, and the excision extends up to 5 cm from the aortic valve. Lesser myectomy shifts the level of obstruction further down into the ventricle and symptoms may persist. With adequate septal myectomy and elimination of SAM, outflow tract obstruction and associated mitral regurgitation are relieved. In our experience, subaortic obstruction due to SAM can always be relieved by adequate transaortic septal myectomy, and treatment with alternate methods such as mitral valve replacement, transmitral myectomy, and mitral leaflet shortening is not necessary. MIDVENTRICULAR VARIANT Midventricular obstruction is less common than subaortic obstruction, and there has been confusion regarding the importance of gradients in producing symptoms. By definition, the level of obstruction is in the midventricle, which is difficult to address through the transaortic approach. Midventricular obstruction has a different pathophysiologic mechanism and, in fact, may have a worse prognosis than other variants of HCM. The obstruction is caused by systolic narrowing of the midventricle because of apposition between the septum and the papillary muscles. Secondary mitral regurgitation is uncommon. Preoperatively, the key echocardiographic feature in establishing the diagnosis is a midcavitary
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY gradient in the absence of SAM of the mitral valve. In addition, there is an open apical chamber, and obstruction at the midcavity does not produce complete systolic obliteration of the cavity. In many patients, the decision for myectomy in those with midventricular obstruction is made difficult because of uncertainty whether symptoms of dyspnea and angina are related to the midcavitary gradient or diastolic dysfunction caused by left ventricular hypertrophy. As is true for subaortic myectomy for obstructive HCM, a complete myectomy is important to relieve midventricular muscular obstruction. The transapical approach is preferred for relief of midventricular obstruction, and some patients have both subaortic obstruction due to basal septal hypertrophy and SAM as well as midventricular obstruction. For patients with obstruction at both levels, we would use both the transaortic and the transapical incisions. Commonly, an endocardial scar is seen on the septum in the area of apposition with the papillary muscles. APICAL MYECTOMY Apical HCM is a unique variant of HCM in which ventricular hypertrophy is localized mainly at the
apex and distal ventricle. Severe degrees of apical hypertrophy can produce a small left ventricular cavity and symptoms of low cardiac output due to diastolic dysfunction. The key features are small left ventricular cavity and the absence of SAM. Treatment options in highly symptomatic patients are very limited and the only other alternative to heart transplantation is a ventricular enlargement procedure, which can be achieved through an apical myectomy. The procedure to augment left ventricular cavity size is performed through a transapical approach and has been described previously. The main principle is to identify the left anterior descending coronary artery, which serves as the surgical landmark for the apical incision, and then a small apical ventriculotomy is made parallel and lateral to it (Fig. 6). Myectomy is begun along the septum with care to avoid injury to the mitral valve apparatus (Fig. 7). Additional muscular resection along the free wall can be performed, and in some patients, the anterolateral and posteromedial papillary muscles can be shaved to further improve diastolic filling. In apical HCM, the hypertrophied muscle usually obliterates the left ventricular apex, and papillary muscles are displaced apically. The resection removes the mass of the myocardium occupying the left ventricular apex,
Figure 6. The left anterior descending coronary artery (LAD) is identified, and an apical ventriculotomy is made lateral to it. This incision is located over the apical dimple (*) when one is present (apical pouch), and it should be situated far enough to the left of the LAD to allow secure closure of the ventricle without compromising the vessel. LV, left ventricle. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) 304
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Figure 7. Myectomy is performed removing septal muscle using a No. 10-blade knife and scissors with the aid of small Volkmann retractors. The main focus of the procedure is on the ventricular septum with limited shaving done on the LV free wall (dashed line in the inset). It is important to avoid excessive myectomy adjacent to the ventriculotomy. LV, left ventricle. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
Figure 8. Adequate augmentation of the left ventricular cavity can be achieved with adequate myectomy. Final inspection is performed to ensure there has been no injury to the mitral valve or its subvalvular components. (Reprinted with permission from Elsevier.) (Color version of figure is available online at http://www.semthorcardiovascsurg.com.)
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY thus augmentation of the left ventricular cavity is achieved (Fig. 8). CONCOMITANT MITRAL VALVE SURGERY Concomitant structural mitral valve abnormalities in the setting of HCM require special attention. In our experience, mitral valve replacement is reserved for patients with intrinsic leaflet abnormalities that cannot be repaired. Mitral valve repair techniques need to be modified when concomitant myectomy is performed. Our approaches for mitral valve repair include resection of the posterior leaflet in the presence of leaflet prolapse or ruptured chord and use of artificial chordae for unsupported anterior leaflet abnormalities. The use of posterior flexible posterior annuloplasty band is individualized and if a band is to be used, we generally select 1 size larger so as to minimize the potential development of SAM after the repair. We previously detailed 32 patients with obstructive HCM and intrinsic mitral valve disease who underwent concomitant septal myectomy and mitral valve repair or replacement. Among the 28 patients who required mitral valvuloplasty, 10 (36%) had leaflet resection, 6 (21%) had repair with an edge-to-edge stitch, and 8 (29%) had leaflet plication; the remaining patients had annuloplasty alone. An annuloplasty ring/band was
used in 19 (68%) and commissural annuloplasty in 2 (7%) patients. At late follow-up, LVOT gradient and SAM resolved in all patients.8 ALTERNATIVE APPROACHES TO TRANSAORTIC SEPTAL MYECTOMY Mobilization of the Fibrous Trigones This technique was described by Yacoub et al and is based on the role played by both the right and left fibrous trigones in the functional anatomy of the normal and diseased LVOT. The authors proposed that LVOT obstruction is due to the presence of a complete fibromuscular ring in the LVOT connecting both fibrous trigones together and this needs to be excised completely with adequate mobilization of both trigones to completely relieve the LVOT obstruction whether it is dynamic or fixed or both.9 Exposure is obtained through an aortotomy. The aortic valve is inspected and any commisural fusion is divided; next the subaortic area is inspected and any subaortic membrane is removed. A vertical incision is made in the septum starting just below the right and middle thirds of the base of the right coronary cusp and extending deep into the ventricle to the level of anterior papillary muscle of the mitral valve. A fibromuscular wedge of tissue is then
Figure 9. This figure demonstrates an example of an accessory papillary muscle that arises from the ventricular septum and is attached to the side of the anterior leaflet. This accessory muscle is excised in its entirety. The fibrous attachments to the side of the leaflet are cut and the papillary muscle is amputated at its base and removed (dotted line). Importantly, chordal attachments to the leading edge of the anterior leaflet are preserved. (Color version of figure is available online at http://www.semthorcardiovascsurg.com.) © 2012 Wiley Periodicals, Inc.
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY excised toward the left fibrous trigone. The left trigone is then mobilized by extending the incision laterally to open the hinge mechanism between the septum and the subaortic curtain. Any bridging tissue between the mitral leaflet and the septum is also excised. The right fibrous trigone is also mobilized by excision of the wedge of abnormal tissue in the angle between the membranous septum and subaortic curtain. We have no experience with this procedure in patients with obstructive HCM but have used similar methods in patients with congenital subaortic obstruction with membranous and varying degrees of muscular obstruction. Transmitral Myectomy A left atrial approach to septal myectomy has been described as an alternative to the standard transaortic procedure.10 Our experience with this method is limited to the pediatric population as the transaortic approach may be challenging in the presence of small aortic valve annulus. An added advantage for the left atrial approach is the ability to address concomitant mitral valve abnormalities and myectomy through a single incision. ADJUNCTS TO SEPTAL MYECTOMY Papillary Muscle Abnormalities Abnormalities of the mitral valve apparatus can exist in some patients with HCM, and may contribute to persistent LVOT gradient if they are not recognized and treated at the time of initial myectomy.11 Anomalous papillary muscle insertion into the anterior mitral leaflet is a well-recognized entity, and its diagnosis is not infrequently missed on preoperative echocardiography. Management of the anomalous papillary muscle depends on its insertion into the mitral leaflet. If it is attached to the free edge of the leaflet, we tend to leave it as a resection in this situation may compromise the competency of the mitral valve, however; if it inserts into the body of the anterior leaflet, it can be excised safely (Fig. 9). Surgical Treatment of Atrial Fibrillation Patients with HCM are at increased risk of atrial fibrillation (AF) because of the long-standing increase in the left ventricular end-diastolic and left atrial pressures. Our current strategy is to perform concomitant AF surgery, primarily pulmonary vein isolation, with septal myectomy for most patients who have AF preoperatively. Early results have demonstrated the feasibility of such an approach with no added risk and improved maintenance of
sinus rhythm.12 The choice of type of maze procedure to be performed is controversial. In general, pulmonary vein isolation is more suitable for those with paroxysmal AF, but for patients who are highly symptomatic with AF and have continuous AF with severely enlarged left atria, we prefer the biatrial Cox maze III (cut and sew) procedure. ALCOHOL SEPTAL ABLATION Septal Ablation vs Septal Myectomy Although septal myectomy is considered the treatment of choice for patients with an obstructive variant of HCM who require septal reduction, alcohol septal ablation (infarction) has emerged as an alternative to surgery.13 Alcohol septal ablation can decrease the LVOT gradient and improve symptoms, but comparative studies tend to support septal myectomy for better long-term symptom relief. When a myectomy is performed in experienced centers, the procedure success rate is higher and the complication rate is lower.14 In a review of 138 patients who underwent alcohol septal ablation at Mayo Clinic between 1998 and 2006, mortality and morbidity of this procedure were higher than that of an age- and gender-matched population who underwent septal myectomy.15 Septal myectomy in patients aged 65 years or younger also had significantly better survival, free of death and severe symptoms (P ¼ 0.01). Patients who might be good candidates for septal reduction by alcohol ablation primarily include older patients with favorable coronary anatomy and associated clinical conditions that would preclude safe operation. Alcohol septal ablation seems ill advised in certain subsets of patients with HCM including young patients, those with severe (diffuse) or relatively thin septal thickness, and very high LVOT gradient. Other major advantages of septal myectomy over alcohol septal ablation are the immediate reduction of the LVOT gradient16 and the possibility of addressing other abnormalities of the outflow tract, especially abnormalities of the mitral valve and anomalous papillary muscles that can also contribute to dynamic outflow tract obstruction. The fact that up to 10% of patients with the presumptive diagnosis of obstructive HCM referred to specialized centers have fixed subaortic obstruction and would not be expected to respond to alcohol septal ablation is often overlooked. Septal Myectomy After Alcohol Septal Ablation An increasing number of patients may present with recurrent symptoms secondary to persistent
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SURGICAL TREATMENT OF HYPERTROPHIC CARDIOMYOPATHY outflow tract obstruction following septal artery ablation that may require reintervention, and 2 points deserve comment.17 First, alcohol septal infarction frequently results in a right bundle branch block, and left bundle branch block often follows septal myectomy. So when septal myectomy is performed after unsuccessful alcohol ablation, permanent pacing is required in a high percentage of patients. A second consideration is patient survival. Among 40 patients who underwent myectomy following alcohol septal ablation, early mortality and perioperative morbidity greater than expected for patients having septal myectomy as a primary procedure.18 RECURRENT OBSTRUCTION AFTER SEPTAL MYECTOMY A small group of patients experience recurrence of their symptoms and LVOT obstruction after previous septal myectomy. In our experience, this occurs most often because of incomplete myectomy at the initial operation rather than recurrent muscle growth. Recurrent obstruction due to muscle regrowth is a potential problem in patients with congenital subaortic obstruction (membranous or tunnel subaortic obstruction or both), but in these patients the subaortic obstruction is fixed and not related to SAM of the mitral valve. Our experience with redo myectomy now includes more than 50 patients. We have identified the following mechanisms for recurrence of left ventricular outflow tract obstruction (LVOTO): limited initial myectomy, septal hypertrophy at the midventricular level, and the pre-existence of an anomalous papillary muscle.19 From our experience, repeat septal myectomy is safe and feasible and should be offered to symptomatic patients with dynamic outflow tract obstruction. LATENT OBSTRUCTION Patients with HCM may be symptomatic in the presence of low resting LVOT gradients, and the clinical dilemma is whether symptoms are due to diastolic dysfunction or a labile outflow tract gradient. The key feature is to evaluate the LVOT gradient at rest and with the use of provocative maneuvers such as exercise testing, Valsalva, or amyl nitrite inhalation during Doppler echocardiography. To better understand the role of septal myectomy in patients with low resting gradients, we reviewed our experience with 249 patients with latent obstruction (gradient o30 mm Hg at rest) but with evidence of severe LVOTO when provoked by Valsalva maneuver or amyl nitrite inhalation. This group was compared with those who had severe resting gradients (430 mm Hg) and underwent septal myectomy during the same
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time period. Early mortality was similarly low (1%) and long-term survival was comparable to that of an agematched population.20 Most importantly, patients with latent obstruction had similar functional improvement after myectomy as those with high resting gradients. We believe, therefore, that in patients with labile obstruction and low resting gradients, symptoms may often be related to a latent form of obstruction rather than diastolic dysfunction, and septal myectomy should be considered. MAYO CLINIC EXPERIENCE More than 2200 patients have had septal myectomy for HCM at the Mayo Clinic. Risk of hospital death after isolated septal myectomy for obstructive HCM is o1% and is similar to the risk of operation for elective mitral valve repair. Complications, such as complete heart block requiring permanent pacemaker and iatrogenic ventricular septal perforation, are uncommon (2%), although partial or complete left bundle branch block is a frequent finding on the postoperative ECG. Usually, this is not associated with adverse sequelae, but if the patient has complete right bundle branch block preoperatively, the left bundle branch block after myectomy increases the risk of complete heart block and the need for permanent pacing. This is particularly important in patients who have had alcohol septal ablation preoperatively, which leads to right bundle branch block in up to 60% of patients.21 Relief of LVOT obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM. Approximately 90% of severely symptomatic patients have improvement of at least 2 function classes, and relief of outflow gradients by myectomy is equally effective in improving limitations because of dyspnea, angina, or syncope.22 Importantly, symptomatic benefit of myectomy is related directly to reduction in the basal outflow tract obstruction, mitral regurgitation, and improvement in left ventricular systolic and enddiastolic pressures (in more than 90% of patients), which in turn may also favorably influence myocardial ischemia. Relief of the gradient may decrease left atrial size and the subsequent risk of developing AF. Importantly, the late survival of HCM patients who have had septal myectomy is equivalent to an agematched population and the risk of appropriate implantable cardioverter defibrillator (ICD) discharges decreases significantly after abolishment of the gradient. We have used the transapical approach in a total of 115 patients with midventricular and apical variants of HCM between 1993 and 2012. All patients with midventricular obstruction (n ¼ 55)
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1. Gersh BJ, Maron BJ, Bonow RO, et al: 2011 ACCF/AHA guideline for the diagnosis and treatment of hypertrophic cardiomyopathy: A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. American College of Cardiology Foundation/American Heart Association Task Force on Practice; American Association for Thoracic Surgery; American Society of Echocardiography; American Society of Nuclear Cardiology; Heart Failure Society of America; Heart Rhythm Society; Society for Cardiovascular Angiography and Interventions; Society of Thoracic Surgeons. J Thorac Cardiovasc Surg 142(6):e153-e203, 2011 2. Nishimura RA, Giuliani ER, Brandenburg RO, et al: Hypertrophic cardiomyopathy. In: Giuliani ER, Gersh BJ, McGoon MD, Hayes DL, Schaff HV, editors. Myocardial Disease: Mayo Clinic Practice of Cardiology, 3rd ed. St. Louis, MO: Mosby-Year Book; 1996. p. 689-711, 1996 [Chapter 20] 3. Kirklin JW, Ellis Jr FH: Surgical relief of diffuse subvalvular aortic stenosis. Circulation 24: 739-742, 1961 4. Goodwin JF, Hollman A, Cleland WP, et al: Obstructive cardiomyopathy simulating aortic stenosis. Br Heart J 22:403-414, 1960 5. Morrow AG, Brockenbrough EC: Surgical treatment of idiopathic hypertrophic subaortic stenosis: Technique and hemodynamic results of subaortic ventriculomyotomy. Ann Surg 154:181-189, 1961 6. Said SM, Dearani JA, Ommen SR, et al: Surgical treatment of hypertrophic cardiomyopathy. Expert Rev Cardiovasc Ther 11(5):617-627, 2013 7. Schaff HV, Said SM: Transaortic extended septal myectomy for hypertrophic cardiomyopathy. Oper Tech Thorac Cardiovasc Surg 17 (4):238-250, 2012
akinesis, but this is relatively small and does not lead to significant systolic dysfunction. Indeed, in patients with apical HCM, the apex is obliterated with muscle and does not contribute to left ventricle stroke volume.23
8. Wan CK, Dearani JA, Sundt 3rd TM, et al: What is the best surgical treatment for obstructive hypertrophic cardiomyopathy and degenerative mitral regurgitation? Ann Thorac Surg 88(3): 727-731, 2009 [discussion 731-2] 9. Yacoub M, Onuzo O, Riedel B, et al: Mobilization of the left and right fibrous trigones for relief of severe left ventricular outflow obstruction. J Thorac Cardiovasc Surg 117(1):126-132, 1999 [discussion 32-3] 10. Matsuda H, Nomura F, Kadoba K, et al: Transatrial and transmitral approach for left ventricular myectomy and mitral valve plication for diffuse-type hypertrophic obstructive cardiomyopathy: A novel approach. J Thorac Cardiovasc Surg 112(1):195-196, 1996 11. Klues HG, Roberts WC, Maron BJ: Anomalous insertion of papillary muscle directly into anterior mitral leaflet in hypertrophic cardiomyopathy; Significance in producing left ventricular outflow tract obstruction. Circulation 84:1188-1197, 1991 12. Chen MS, McCarthy PM, Lever HM, et al: Effectiveness of atrial fibrillation surgery in patients with hypertrophic cardiomyopathy. Am J Cardiol 93(3):373-375, 2004 13. Lakkis NM, Nagueh SF, Dunn JK, et al: Nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy: One-year follow-up. J Am Coll Cardiol 36(3):852-855, 2000 14. Maron BJ: Controversies in cardiovascular medicine. Surgical myectomy remains the primary treatment option for severely symptomatic patients with obstructive hypertrophic cardiomyopathy. Circulation 116(2):196-206, 2007 15. Sorajja P, Valeti U, Nishimura RA, et al: Outcome of alcohol septal ablation for obstructive hypertrophic cardiomyopathy. Circulation 118 (2):131-139, 2008
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16. Maron BJ: Commentary and re-appraisal: Surgical septal myectomy vs. alcohol ablation: After a decade of controversy and mismatch between clinical practice and guidelines. Prog Cardiovasc Dis 54(6):523-528, 2012 17. Chang SM, Lakkis NM, Franklin J, et al: Predictors of outcome after alcohol septal ablation therapy in patients with hypertrophic obstructive cardiomyopathy. Circulation 109 (7):824-827, 2004 18. ElBardissi AW, Dearani JA, Nishimura RA, et al: Septal myectomy after previous septal artery ablation in hypertrophic cardiomyopathy. Mayo Clin Proc 82(12):1516-1522, 2007 19. Minakata K, Dearani JA, Schaff HV, et al: Mechanisms for recurrent left ventricular outflow tract obstruction after septal myectomy for obstructive hypertrophic cardiomyopathy. Ann Thorac Surg 80(3):851-856, 2005 20. Schaff HV, Dearani JA, Ommen SR, et al: Expanding the indications for septal myectomy in patients with hypertrophic cardiomyopathy: Results of operation in patients with latent obstruction. J Thorac Cardiovasc Surg 143(2): 303-309, 2012 [Epub 2011 Dec 10] 21. McCann GP, Van Dockum WG, Beek AM, et al: Extent of myocardial infarction and reverse remodeling assessed by cardiac magnetic resonance in patients with and without right bundle branch block following alcohol septal ablation for obstructive hypertrophic cardiomyopathy. Am J Cardiol 99:563-567, 2007 22. McCully RB, Nishimura RA, Tajik AJ, et al: Extent of clinical improvement after surgical treatment of hypertrophic obstructive cardiomyopathy. Circulation 467-471 23. Said SM, Schaff HV, Abel MD, et al: Transapical approach for apical myectomy and relief of midventricular obstruction in hypertrophic cardiomyopathy. J Card Surg 27(4):443-448, 2012 [Epub 2012 May 29]
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