Heart, Lung and Circulation (2014) 23, e131–e135 1443-9506/04/$36.00 http://dx.doi.org/10.1016/j.hlc.2014.01.007
MitraClip Implantation as a New Treatment Strategy against Systolic Anterior Motion-induced Outflow Tract Obstruction in Hypertrophic Obstructive Cardiomyopathy Ulrich Scha¨fer, MD *, Felix Kreidel, MD , Christian Frerker, MD Asklepios Clinics Sankt Georg, Hamburg, Germany Received 16 August 2013; received in revised form 14 November 2013; accepted 7 January 2014; online published-ahead-of-print 24 January 2014
We report on catheter-based treatment of left ventricular outflow tract (LVOT) obstruction targeting primarily a systolic anterior motion of the anterior mitral leaflet in hypertrophic obstructive cardiomyopathy (HOCM). A patient was successfully treated with the MitraClip two years after septal myectomy in conjunction with mitral valve repair. The results prove the concept, that systolic anterior motion (SAM) is clearly involved in gradient formation and is more than an epiphenomenon in HOCM. Thus, SAM-induced subaortic obstruction might be a target for MitraClip implantation. Keywords
Hypertrophic obstructive cardiomyopathy Systolic anterior motion MitraClip Haemodynamics Outflow tract obstruction
Introduction There is an ongoing debate whether septal myectomy should be primarily performed using either surgical myectomy (Morrow procedure) or transcatheter instillation of alcohol into septal perforators for ablation of the septal hypertrophy. In younger patients with hypertrophic obstructive cardiomyopathy (HOCM) the gold standard is surgical myectomy to relieve left ventricular outflow tract obstruction and cardiac symptoms [1,2]. Interestingly, HOCM is frequently accompanied by abnormalities of the mitral valve and the subvalvular mitral apparatus . Usually, these abnormalities can be best managed surgically, without the need for mitral valve replacement. But many surgeons still prefer mitral valve replacement (MVR, sometimes mechanical MVR) instead of mitral valve repair for patients with HOCM and concomitant mitral regurgitation (MR). In this regard systolic anterior
motion (SAM) of the anterior mitral leaflet usually causes the MR, but may also be a significant contributor to LVOT obstruction. To prevent LVOT obstruction extended septal myectomy is concomitantly performed with leaflet resection, leaflet plication and/or annuloplasty rings/bands . In addition, an edge-to-edge stitch  or transfer of posteriorly directed secondary chords (which would otherwise be resected) to the underside of the middle of the mid-anterior leaflet with a small piece of an anchoring pledget  have been proposed. Thus the use of a MitraClip was especially appealing to us, since the MitraClip might keep the anterior leaflet edge away from the LVOT.
Case report A 69 year-old male patient with a past medical history of treated HOCM was admitted to our institution. Two years ago he underwent surgical myectomy in conjunction with
*Corresponding author: Asklepios Clinics Sankt Georg, Department of Cardiology, Lohmuehlenstrasse 5, 20099 Hamburg, Germany, Tel.: +49 401818854473, fax: +49 401818854444., Email: [email protected]
© 2014 Published by Elsevier Inc on behalf of Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ).
U. Scha¨fer et al.
Figure 1 Transoesophageal echocardiography displaying significant mitral regurgitation in conjunction with significant LVOT obstruction due to severe SAM of the anterior mitral leaflet.
mitral ring annuloplasty (Edwards Physioring II 30 mm). The patient reported suffering from increasing dyspnoea on slight physical exertion (NYHA 2-3) and he complained about dizziness. During routine transoesophageal examination MR was discovered with significant SAM (Fig. 1) and LVOT obstruction. Invasive assessment confirmed a dynamic subaortic obstruction with a characteristic bifid
pulse and a basal peak pressure gradient between 59 and 83 mmHg at rest (mean gradient 38-60 mmHg), which was post-extrasystolic significantly augmented to more than 150 mmHg (Fig. 2). In addition infusion of nitroglycerine significantly augmented the pressure gradient across the LVOT. Laboratory testing showed normal troponin levels and an elevated Nt-proBNP. Coronary artery disease was
Figure 2 Invasive measurement of the basal transvalvular aortic gradient (aortic pressure vs. mid left ventricular pressure) displaying a significant LVOT obstruction. The transvalvular aortic gradient shows a significant post- extrasystolic increase (see blue arrow) indicating dynamic obstruction.
MitraClip Implantation as a New Treatment Strategy
excluded by coronary angiography. Several perforator branches were identified to be likely suitable for alcohol septal ablation. Due to the profound SAM with a secondary MR, we hypothesised that placing a MitraClip into the A2P2segment of the mitral valve should significantly reduce not only the MR, but also the obstruction within the LVOT. In addition, alcohol septal ablation was discussed but judged as a second choice, since surgical myectomy had been previously performed. Despite the relatively young age and low operative risk of the patient (logEUROscore 15.8%), a MitraClip approach was favoured within the HEART team over repeated cardiac surgery or alcohol septal ablation. After a detailed explanation of the procedure including risks and benefit, the patient consented completely to this experimental approach. The following day, the patient was scheduled for MitraClip implantation, in stand-by for alcohol septal ablation if edge-to-edge therapy failed. After transseptal puncture, the clip was oriented into the A2P2 segment (using 3D TEE) with precise perpendicularity to the line of coaptation. After a single grasp (guidance by X-plane visualisation) MR was almost completely abolished (Fig. 3). 3D-TEE confirmed a broad tissue bridge between A2 and P2 with an
insignificant mean transmitral gradient of 3 mmHg. But most importantly, the MitraClip was able to significantly blunt the gradient (Fig. 4). Moreover, post-extrasystolic pressure augmentation was no longer present (Fig. 4). The patient’s condition demonstrated an immediate improvement and he was discharged at day 1 after the procedure. At three, six and 12 months follow-up, the patient presented in a persistent improved clinical state (NYHA class I) and echocardiography revealed an insignificant residual MR with a continuously reduced LVOT gradient.
Discussion Alcohol septal ablation for HOCM has emerged as a catheter based technique and thus as a lesser invasive alternative to surgical myectomy. A recent meta-analysis  demonstrated a sustained decrease in resting and provoked LVOT gradients, which were accompanied by a reduction in basal septal diameters, improvements in NYHA Class and an increase in exercise capacity. Nevertheless, early mortality (0.0-5.0%) and late mortality (0.0-9.3%) as well as other
Figure 3 Transoesophageal echocardiography showing almost complete abolition of mitral regurgitation in conjunction with significant reduced LVOT obstruction, SAM of the anterior mitral leaflet is no longer visible.
U. Scha¨fer et al.
Figure 4 Invasive measurement of the transvalvular aortic gradient (aortic pressure vs. mid left ventricular pressure) after MitraClip implantation, with virtually complete abolition of the basal LVOT gradient in addition to almost complete abolition of the post-extrasystolic increase in pressure gradient.
complications demonstrate a certain risk with alcohol septal ablation. Until today, complete heart block seems to be the most frequent complication after alcohol septal ablation reaching up to 20% in various reports . Thus, albeit with almost similar efficacy with regard to gradient reduction and clinical improvement with alcohol septal ablation compared to surgical myectomy, the occurrence of complete heart block favours surgical treatment over alcohol septal ablation especially in younger patients . Besides muscular LVOT obstruction, the mitral valve is frequently involved in the pathophysiology of HOCM . Elongation and pathological thickening of the mitral valve (MV) leaflets has been described in hypertrophic cardiomyopathy (HCM). Associated features include mal-positioning of the papillary muscles as well as SAM of the MV leaflets, which can worsen the turbulence and dynamic LVOT gradient. Coaptation of the MV leaflets depends on both anterior and posterior leaflet length and position, and failure of either to optimally adapt in this setting can result in mitral regurgitation or worsened LVOT obstruction. Thus targeting SAM with the MitraClip as shown in this particular patient, was considered as an appealing concept for us to treat LVOT obstruction. It might be argued that this approach was not supported by any experimental animal data. To our knowledge there is no suitable animal HOCM model for testing the MitraClip. In addition we needed a fast solution for the admitted patient. Due to our large experience with the MitraClip device (over 350 cases) we were intrigued to treat that patient in such an experimental setting since the patient fully consented to this approach. The procedure went exceptionally well without any difficulties of leaflet grasping and there was no sign of mitral stenosis despite the presence of a mitral annuloplasty ring. But most importantly, we were able to significantly blunt systolic outflow tract obstruction proving the concept that SAM does
significantly contribute to gradient formation. The patient felt an immediate improvement and completed recently a 12 months follow-up without any sign of clinical worsening in symptoms or recurrent gradient formation. Thus, the presented case might be considered as a novel approach for treatment of SAM-induced outflow tract obstruction. Interestingly, SAM of the mitral valve causing LVOT obstruction does not only occur in HOCM. SAM-induced LVOT obstruction has also been observed in conditions of hypertensive heart disease, dehydration, severe bleeding, sepsis, vasodilatation, excessive sympathetic stimulation, pericardial tamponade, after aortic valve replacement as well as after mitral valve repair. Especially post-mitral repair SAM with left ventricular outflow tract obstruction (LVOTO) and mitral regurgitation (MR) are a concern and continue to occur in 1% to 16% of patients [11–16] SAM can result in critical left ventricular outflow tract obstruction and/or mitral regurgitation and is associated with a risk of sudden death (suicide ventricle). The mechanisms of SAM are complex and depend on the functional status of the ventricle. A likely contributing mechanism has been suggested to occur if mitral valve coaptation to septum distance had been surgically reduced by implantation of down-sized annuloplasty ring. In some cases further surgery to relieve the obstruction is necessary. The present case presents a new treatment strategy, which might spare such a patient redo open-heart surgery. In general, good, comprehensive and multidisciplinary and experienced HOCM care at a Centres of Excellence should both avoid and treat the current dilemma, especially in a young individual, although the current description might be an option for those who have truly failed after standard treatment. It might be argued that the patient didn’t display a left bundle branch blockade after septal myectomy, possibly indicating a poorly performed myectomy. Nevertheless,
MitraClip Implantation as a New Treatment Strategy
MitraClip implantation clearly relieved his symptoms offering a new treatment option in such a patient.
Limitations Despite a promising 12 months follow-up in that particular patient, long-term outcomes are not assured with this novel approach over accepted practice. Clipping the valve adds a foreign body and may also continue to deteriorate over time.
Conclusion The edge-to-edge technique seems to be a plausible solution, since narrowing of the outflow-tract due to dislocation of the coaptation zone towards the septum can be ruled out. Due to the lower invasiveness of the MitraClip as opposed to surgical MVR, further efficacy testing of a MitraClip approach in conditions with extensive SAM might be of interest in the future.
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