Original Article
Intraaortic balloon pump boon for off-pump coronary artery bypass grafting
Asian Cardiovascular & Thoracic Annals 2015, Vol. 23(3) 267–270 ß The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492314544158 aan.sagepub.com
Kamales Kumar Saha1–3, Ram P Kaushal4, Ajay Kumar1, Mandar Deval3, Kakalee K Saha1 and Shibban K Kaul3
Abstract Background: Off-pump coronary artery bypass techniques have evolved in the past decade, but there are some concerns about hemodynamic decompensation requiring conversion to cardiopulmonary bypass. These conversions are associated with higher morbidity and mortality. We use an intraaortic balloon pump to treat ischemia-induced hemodynamic instability and arrhythmias during off-pump coronary artery bypass. The objective of this study was to assess the impact of intraaortic balloon pump use in off-pump coronary artery bypass to prevent emergency conversion to cardiopulmonary bypass. Methods: Data of 529 consecutive unselected patients who underwent isolated coronary artery bypass were included in this retrospective study of prospectively collected data and operation notes. Complete revascularization was performed using an off-pump technique. All arterial grafts using bilateral internal mammary arteries, and aortic no-touch technique were preferred. If the clinical situation demanded, vein grafts were used. During the procedure, any hemodynamic compromise not responding to conventional inotropic therapy was treated with intraaortic balloon pump insertion. Results: Complete revascularization was possible in all 529 patients. An intraaortic balloon pump was inserted in 33 (6.2%) patients to treat hemodynamic instability; in all cases, conversion to cardiopulmonary bypass was avoided and complete revascularization was achieved. Conclusion: For treating hemodynamic instability during off-pump coronary artery bypass, we recommend intraaortic balloon pump insertion as the preferred bail-out method rather than conversion to cardiopulmonary bypass.
Keywords Coronary artery bypass grafting, CABG, off-pump CABG, coronary artery disease, intra-aortic balloon pump, off-pump conversion
Introduction Off-pump coronary artery bypass (OPCAB) techniques have continued to evolve over the years, but one area of concern for the surgeon remains hemodynamic decompensation during coronary anastomosis. Hemodynamic decompensation during OPCAB has been traditionally treated by institution of cardiopulmonary bypass. Emergency conversion of OPCAB to an on-pump procedure is associated with increased morbidity and mortality, and hence is undesirable.1 Hemodynamic decompensation during OPCAB can be due to either decreased preload resulting from hypovolemia or
myocardial dysfunction resulting from ischemia. Hypovolemia can be easily treated using volume resuscitation. Hypotension due to myocardial ischemia can 1
Private practice in multiple private hospitals in Mumbai, India Fortis SL Raheja Hospital, Mumbai, India 3 MGM Medical College, Navi Mumbai, India 4 Gandhi Medical College, Bhopal, India 2
Corresponding author: Kamales Kumar Saha, C-801/802 Raheja Sherwood, Behind Hub Mall, Off Western Express Highway, Nirlon Compound, Goregaon East, Mumbai 400063, India. Email: [email protected]
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
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be treated using inotropic support. For hypotension refractory to inotrope therapy, an intraaortic balloon pump (IABP), which is routinely used to treat cardiogenic shock, has been used. There have been reports of use of ventricular assist device to prevent conversions, however, IABP use during OPCAB to prevent conversion has not been reported before.2 Various studies have suggested that preoperative IABP insertion in high-risk patients may facilitate OPCAB.3 We perform OPCAB routinely in all isolated coronary artery bypass cases, and use an IABP to treat hemodynamic compromise rather than for preoperative prophylactic use. The objective of this study was to assess the effectiveness of IABP in preventing OPCAB conversions to cardiopulmonary bypass.
Patients and methods All 529 cases of consecutive unselected isolated coronary artery bypass grafting operated on by the first author were included in this retrospective study of prospectively collected data and operation notes. The operation records of all patients were analyzed. OPCAB was performed routinely in all patients. Complete revascularization was attempted in every case. An IABP was kept on standby with electrocardiogram leads connected. Each patient had femoral artery access and a central venous line (central line or pulmonary artery catheter) inserted under local anesthesia before induction of general anesthesia. We followed a standard protocol for OPCAB in all patients. After pericardiotomy, cardiac manipulation was avoided and only the left anterior descending artery (LAD) was inspected and palpated. We did not use a deep pericardial stay suture. Warm saline-soaked gauze pads were used to position the heart. A suction type of stabilizer and mister bower were used for OPCAB. Grafting of the LAD can be easily performed with minimal cardiac manipulation. We used maximum number of arterial grafts and both internal mammary arteries (IMA) when possible. Vein grafts were used when arterial grafts were not suitable for use, or to supplement the length of arterial grafts. Aortic clamping was avoided when possible. Both IMA were used in situ. The left IMA was used most frequently to graft the LAD, and sometimes the right IMA was used for LAD grafting; the other IMA was used as a composite graft with radial artery or saphenous vein. After grafting the LAD, the heart was lifted and the other target vessels were assessed. A composite graft between the other IMA and radial artery was created,4 and the remaining grafts were constructed. In every patient, an inotropic infusion was kept connected so it could be started without delay. Any ventricular arrhythmia considered to be of ischemic origin
was treated by medical therapy initially, and by IABP insertion if refractory. Ventricular arrhythmia was treated by direct current shock and an intravenous lidocaine bolus. Intravenous amiodarone infusion was started. Hypokalemia and acidosis were corrected. If hemodynamics were satisfactory after the restoration of normal rhythm, off-pump grafting was continued. However, if ventricular arrhythmia recurred, myocardial contractility was poor, and/or hemodynamics remained unsatisfactory, IABP was inserted. If systolic arterial blood pressure was less than 100 mm Hg in spite of inotropic support, IABP insertion was considered. If systolic pressure was less than 100 mm Hg, we assessed the cardiac filling pressure. The central venous pressure or pulmonary artery diastolic pressure indicates cardiac filling. In the presence of low cardiac filling, temporary lowering of head end to increase systolic pressure and volume resuscitation were initiated. However, in the presence of increased filling pressure, elevation of the head end will improve hemodynamics. In such situations, inotropic support with dobutamine (up to 10 mg kg 1) and norepinephrine (up to 0.1 mg kg 1) were used. If blood pressure remained refractory and/or myocardial contraction appeared sluggish, IABP was inserted. After IABP insertion and a functioning graft to the LAD was achieved, if the patient continued to require high doses of inotropics, we revascularized the right coronary artery or posterior descending artery, which can be performed without too much cardiac manipulation. The IABP was removed in the postoperative intensive care unit, depending on the clinical condition of the patient.
Results Table 1 shows the distribution of patients according to left ventricular ejection fraction. An IABP was inserted in 33 (6.2%) patients during grafting to treat ischemiainduced hemodynamic instability and arrhythmia. Table 2 shows the various indications for IABP insertion; intraoperative hemodynamic compromise was the commonest indication. In patients with hemodynamic compromise, after IABP insertion, systolic blood pressure improved and cardiac filling pressure decreased. These favorable changes in hemodynamics allowed us to complete OPCAB without conversion to cardiopulmonary bypass. Often in these patients, performing the distal coronary anastomosis and reestablishing blood flow in the coronary artery resulted in further improvement in hemodynamics (increased systemic blood pressure and decreased cardiac filling pressure). In patients with arrhythmia, after IABP insertion normal rhythm was restored and hemodynamics improved. In these patients, an improvement in hemodynamics was also noted after distal coronary anastomosis. OPCAB
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
Saha et al.
269
Table 1. Use of an intraaortic balloon pump in 529 patients undergoing off-pump coronary artery bypass. IABP insertion
Total
EF 4 30% EF 31%–49% EF 5 50%
No. of patients No IABP IABP Preoperative Intraoperative Postoperative
529
153
198
178
486 43 (8.1%) 6 33 4
119 34 (22.2%) 6 25 3
195 3 (1.5%) 0 3 0
172 6 (3.4%) 0 5 1
EF: ejection fraction; IAPB: intraaortic balloon pump.
Table 4. Distribution of patients according to number of grafts received. No. of grafts
No. of patients
9 8 7 6 5 4 3 2 1
1 (0.2%) 4 (0.8%) 14 (2.6%) 56 (10.6%) 142 (26.8%) 189 (35.7%) 76 (14.4%) 40 (7.6%) 7 (1.3%)
Table 2. Indications for intraaortic balloon pump insertion. Indication
Preoperative
Intraoperative
Postoperative
Hemodynamic instability Arrhythmia Left ventricular failure Unstable angina Total
1
29
1
0 2
4 0
3 0
3 6
0 33
0 4
Table 3. Distribution of grafts in 529 patients. Grafts
No. of patients
Bilateral IMA grafts Total grafts per patient Arterial grafts per patient Vein grafts per patient
484 (91.5%) 4.2 3.8 0.4
IMA: internal mammary artery.
conversion was avoided in all 529 patients. Complete revascularization was achieved in all patients. There was no IABP-related complication in the patients who required IABP insertion. Table 3 shows the distribution of arterial and venous grafts. A total of 2256 grafts were created (range 1–9). Table 4 shows the distribution of patients according to the number of grafts they received; 406/529 (76.7%) patients received 4 or more grafts. Forty-seven patients who received 1 or 2 grafts had single-vessel disease of the LAD and received a graft to either the LAD alone (7 patients) or the LAD and diagonal.
Discussion OPCAB technique continues to evolve, particularly in India and other Asian countries.5 There are some
concerns about short and long term results of OPCAB compared to conventional on-pump coronary bypass grafting which was previously considered the gold standard for surgical revascularization. We tried to address the two key issues associated with OPCAB skepticism in this study: conversion to cardiopulmonary bypass, and completeness of revascularization.5 To prevent OPCAB conversion, we followed a standardized protocol in every patient. Using this protocol, we were able to treat 529 consecutive unselected cases of OPCAB with no conversions to cardiopulmonary bypass. It has been well established that the rate of conversion decreases with operator experience.1,6 It can be argued that many of the conversions are the result of a panic reaction by the surgeon or anesthetist or both. In view of the adverse outcomes of such conversions, the rate of conversion may be considered a surrogate performance indicator in OPCAB.1 Management of hemodynamic instability during OPCAB is not as complex as touted. Hypotension due to hypovolemia is easily treated by volume resuscitation. Just as hypotension due to myocardial infarction in cardiogenic shock is treated using IABP support, ischemic myocardial dysfunction-induced hypotension during OPCAB can also be managed by IABP, and thus avoid conversion. Ischemia-induced arrhythmias refractory to pharmacological agents can also be successfully treated with an IABP. There are reports of the use of a ventricular assist device to prevent OPCAB conversion.7 Many articles describe the use of prophylactic IABP in high-risk patients during OPCAB.8 We feel that with established femoral access, proper training and motivation of team members, and keeping an IABP on standby, IABP support can be started at very short notice. We feel routine prophylactic use of preoperative an IABP to facilitate OPCAB is unnecessary even in high-risk patients because we often observe an increase in systemic blood pressure and a decrease in cardiac filling pressure after graft flow is
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
270
Asian Cardiovascular & Thoracic Annals 23(3)
established to ischemic coronary artery. Preoperative IABP insertion should be reserved for patients with unstable angina refractory to medical therapy, left ventricular failure, or cardiogenic shock. What constitutes complete revascularization remains controversial. It is often observed that the requirement of more than 3 grafts is considered an indication for an on-pump procedure rather than OPCAB.9 In our series, the average number of grafts per patient was more than 4, and 76% received 4 or more grafts. No diseased artery was left without a bypass graft because of a technical difficulty. Earlier revascularization of the posterolateral and inferior vessels used to be considered difficult during OPCAB, but with refinement of the technique, these vessels are being routinely grafted during OPCAB without any hemodynamic instability. Actually, we find grafting these vessels easier during OPCAB because no assistance is required to retract the heart as in on-pump grafting. We successfully performed 9 grafts in a patient with diffuse coronary artery disease. We feel that without the stress imposed by prolonged aortic crossclamp time or cardiopulmonary bypass time, complete revascularization can be performed more often than not. This is particularly true in patients with small vessels and diffuse coronary artery disease, which are prevalent in our part of the world. We sometimes even have to cut across a severely diseased segment and perform a long anastomosis using innovative techniques such as onlay patch plasty. It is obvious that such a long anastomosis will increase the cardiopulmonary bypass and clamp time and deter surgeons from performing complete revascularization. With OPCAB, our threshold for sequentially grafting the LAD has become low; for distal LAD disease, we use sequential left IMA grafts to the mid and distal LAD, whereas in on-pump coronary artery bypass, surgeons might be inclined to leave the distal LAD disease to medical management. Several limitations of our study should be recognized. The study was retrospective in nature. Moreover, it is the experience of a single surgeon with a strong bias for OPCAB. There was no control group of patients who required conversion to cardiopulmonary bypass. Further study on the use of IABP insertion to prevent OPCAB conversion is warranted. We concluded that complete revascularization and OPCAB conversion are interrelated. Apprehension of OPCAB conversion and its sequelae will always be in the mind of a surgeon while performing lateral wall revascularization. This is particularly true for a beginner in a low-volume center. The apprehension of OPCAB conversion can lead to incomplete revascularization. This may be the reason for the widespread reports of incomplete revascularization in OPCAB.5 The detrimental effects of conversion and incomplete
revascularization are well highlighted in the literature, but there are very few articles that provide a framework for prevention of emergency conversion in OPCAB. In our large series, we found that conversion can be avoided and complete revascularization in OPCAB is possible by timely and effective use of an IABP. Acknowledgments Presented at the annual meeting of The Society for Cardiothoracic Surgery in Great Britain and Ireland, Edinburgh, UK, March 10–12, 2014.
Funding This research received no specific grant from any funding agency in the public, commerical, or not-for-profit sectors.
Conflict of interest statement None declared.
References 1. Mukherjee D, Ahmed K, Baig K, Patel VM, Darzi A and Athanasiou T. Conversion and safety in off-pump coronary artery bypass: a system failure that needs re-emphasis. Ann Thorac Surg 2011; 91: 630–639. 2. Saha KK, Deval M, Jagdale L and Sahani P. Off-pump coronary artery bypass grafting in a low-volume center. Heart Surg Forum 2011; 14: E349–E353. 3. Mannacio V, Di Tommaso L, De Amicis V, Stassano P, Musumeci F and Vosa C. Preoperative intraaortic balloon pump for off-pump coronary arterial revascularization. Ann Thorac Surg 2012; 93: 804–809. 4. Saha KK, Deval M, Manoria P, Manoria PC and Jagdale L. Off-pump CABG with aortic-no-touch using bilateral in-situ IMA—a new technique. Ind J Thorac Cardiovasc Surg 2011; 27: 165–8. (Available at: http://link.springer. com/article/10.1007/s12055-011-0125-1. Accessed June 27, 2014. 5. Lazar HL. Should off-pump coronary artery bypass grafting be abandoned [Review]? Circulation 2013; 128: 406–413. 6. Hsu RB and Lin CH. Surgical proficiency and quality indicators in off-pump coronary artery bypass. Ann Thorac Surg 2013; 96: 2069–2074. 7. Gregoric ID, Poglajen G, Span M, Frazier OH, Loyalka P and Kar B. Percutaneous ventricular assist device support during off-pump surgical coronary revascularization. Ann Thorac Surg 2008; 86: 637–639. 8. Qiu Z, Chen X, Xu M, et al. Evaluation of preoperative intra-aortic balloon pump in coronary patients with severe left ventricular dysfunction undergoing OPCAB surgery: early and mid-term outcomes. J Cardiothorac Surg 2009; 4: 39. 9. Lattouf OM, Puskas JD, Thourani VH, Noora J, Kilgo PD and Guyton RA. Does the number of grafts influence surgeon choice and patient benefit of off-pump over conventional on-pump coronary artery revascularization in multivessel coronary artery disease? Ann Thorac Surg 2007; 84: 1485–1894.
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
Intraaortic balloon pump boon for off-pump coronary artery bypass grafting
Asian Cardiovascular & Thoracic Annals 2015, Vol. 23(3) 267–270 ß The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492314544158 aan.sagepub.com
Kamales Kumar Saha1–3, Ram P Kaushal4, Ajay Kumar1, Mandar Deval3, Kakalee K Saha1 and Shibban K Kaul3
Abstract Background: Off-pump coronary artery bypass techniques have evolved in the past decade, but there are some concerns about hemodynamic decompensation requiring conversion to cardiopulmonary bypass. These conversions are associated with higher morbidity and mortality. We use an intraaortic balloon pump to treat ischemia-induced hemodynamic instability and arrhythmias during off-pump coronary artery bypass. The objective of this study was to assess the impact of intraaortic balloon pump use in off-pump coronary artery bypass to prevent emergency conversion to cardiopulmonary bypass. Methods: Data of 529 consecutive unselected patients who underwent isolated coronary artery bypass were included in this retrospective study of prospectively collected data and operation notes. Complete revascularization was performed using an off-pump technique. All arterial grafts using bilateral internal mammary arteries, and aortic no-touch technique were preferred. If the clinical situation demanded, vein grafts were used. During the procedure, any hemodynamic compromise not responding to conventional inotropic therapy was treated with intraaortic balloon pump insertion. Results: Complete revascularization was possible in all 529 patients. An intraaortic balloon pump was inserted in 33 (6.2%) patients to treat hemodynamic instability; in all cases, conversion to cardiopulmonary bypass was avoided and complete revascularization was achieved. Conclusion: For treating hemodynamic instability during off-pump coronary artery bypass, we recommend intraaortic balloon pump insertion as the preferred bail-out method rather than conversion to cardiopulmonary bypass.
Keywords Coronary artery bypass grafting, CABG, off-pump CABG, coronary artery disease, intra-aortic balloon pump, off-pump conversion
Introduction Off-pump coronary artery bypass (OPCAB) techniques have continued to evolve over the years, but one area of concern for the surgeon remains hemodynamic decompensation during coronary anastomosis. Hemodynamic decompensation during OPCAB has been traditionally treated by institution of cardiopulmonary bypass. Emergency conversion of OPCAB to an on-pump procedure is associated with increased morbidity and mortality, and hence is undesirable.1 Hemodynamic decompensation during OPCAB can be due to either decreased preload resulting from hypovolemia or
myocardial dysfunction resulting from ischemia. Hypovolemia can be easily treated using volume resuscitation. Hypotension due to myocardial ischemia can 1
Private practice in multiple private hospitals in Mumbai, India Fortis SL Raheja Hospital, Mumbai, India 3 MGM Medical College, Navi Mumbai, India 4 Gandhi Medical College, Bhopal, India 2
Corresponding author: Kamales Kumar Saha, C-801/802 Raheja Sherwood, Behind Hub Mall, Off Western Express Highway, Nirlon Compound, Goregaon East, Mumbai 400063, India. Email: [email protected]
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
268
Asian Cardiovascular & Thoracic Annals 23(3)
be treated using inotropic support. For hypotension refractory to inotrope therapy, an intraaortic balloon pump (IABP), which is routinely used to treat cardiogenic shock, has been used. There have been reports of use of ventricular assist device to prevent conversions, however, IABP use during OPCAB to prevent conversion has not been reported before.2 Various studies have suggested that preoperative IABP insertion in high-risk patients may facilitate OPCAB.3 We perform OPCAB routinely in all isolated coronary artery bypass cases, and use an IABP to treat hemodynamic compromise rather than for preoperative prophylactic use. The objective of this study was to assess the effectiveness of IABP in preventing OPCAB conversions to cardiopulmonary bypass.
Patients and methods All 529 cases of consecutive unselected isolated coronary artery bypass grafting operated on by the first author were included in this retrospective study of prospectively collected data and operation notes. The operation records of all patients were analyzed. OPCAB was performed routinely in all patients. Complete revascularization was attempted in every case. An IABP was kept on standby with electrocardiogram leads connected. Each patient had femoral artery access and a central venous line (central line or pulmonary artery catheter) inserted under local anesthesia before induction of general anesthesia. We followed a standard protocol for OPCAB in all patients. After pericardiotomy, cardiac manipulation was avoided and only the left anterior descending artery (LAD) was inspected and palpated. We did not use a deep pericardial stay suture. Warm saline-soaked gauze pads were used to position the heart. A suction type of stabilizer and mister bower were used for OPCAB. Grafting of the LAD can be easily performed with minimal cardiac manipulation. We used maximum number of arterial grafts and both internal mammary arteries (IMA) when possible. Vein grafts were used when arterial grafts were not suitable for use, or to supplement the length of arterial grafts. Aortic clamping was avoided when possible. Both IMA were used in situ. The left IMA was used most frequently to graft the LAD, and sometimes the right IMA was used for LAD grafting; the other IMA was used as a composite graft with radial artery or saphenous vein. After grafting the LAD, the heart was lifted and the other target vessels were assessed. A composite graft between the other IMA and radial artery was created,4 and the remaining grafts were constructed. In every patient, an inotropic infusion was kept connected so it could be started without delay. Any ventricular arrhythmia considered to be of ischemic origin
was treated by medical therapy initially, and by IABP insertion if refractory. Ventricular arrhythmia was treated by direct current shock and an intravenous lidocaine bolus. Intravenous amiodarone infusion was started. Hypokalemia and acidosis were corrected. If hemodynamics were satisfactory after the restoration of normal rhythm, off-pump grafting was continued. However, if ventricular arrhythmia recurred, myocardial contractility was poor, and/or hemodynamics remained unsatisfactory, IABP was inserted. If systolic arterial blood pressure was less than 100 mm Hg in spite of inotropic support, IABP insertion was considered. If systolic pressure was less than 100 mm Hg, we assessed the cardiac filling pressure. The central venous pressure or pulmonary artery diastolic pressure indicates cardiac filling. In the presence of low cardiac filling, temporary lowering of head end to increase systolic pressure and volume resuscitation were initiated. However, in the presence of increased filling pressure, elevation of the head end will improve hemodynamics. In such situations, inotropic support with dobutamine (up to 10 mg kg 1) and norepinephrine (up to 0.1 mg kg 1) were used. If blood pressure remained refractory and/or myocardial contraction appeared sluggish, IABP was inserted. After IABP insertion and a functioning graft to the LAD was achieved, if the patient continued to require high doses of inotropics, we revascularized the right coronary artery or posterior descending artery, which can be performed without too much cardiac manipulation. The IABP was removed in the postoperative intensive care unit, depending on the clinical condition of the patient.
Results Table 1 shows the distribution of patients according to left ventricular ejection fraction. An IABP was inserted in 33 (6.2%) patients during grafting to treat ischemiainduced hemodynamic instability and arrhythmia. Table 2 shows the various indications for IABP insertion; intraoperative hemodynamic compromise was the commonest indication. In patients with hemodynamic compromise, after IABP insertion, systolic blood pressure improved and cardiac filling pressure decreased. These favorable changes in hemodynamics allowed us to complete OPCAB without conversion to cardiopulmonary bypass. Often in these patients, performing the distal coronary anastomosis and reestablishing blood flow in the coronary artery resulted in further improvement in hemodynamics (increased systemic blood pressure and decreased cardiac filling pressure). In patients with arrhythmia, after IABP insertion normal rhythm was restored and hemodynamics improved. In these patients, an improvement in hemodynamics was also noted after distal coronary anastomosis. OPCAB
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
Saha et al.
269
Table 1. Use of an intraaortic balloon pump in 529 patients undergoing off-pump coronary artery bypass. IABP insertion
Total
EF 4 30% EF 31%–49% EF 5 50%
No. of patients No IABP IABP Preoperative Intraoperative Postoperative
529
153
198
178
486 43 (8.1%) 6 33 4
119 34 (22.2%) 6 25 3
195 3 (1.5%) 0 3 0
172 6 (3.4%) 0 5 1
EF: ejection fraction; IAPB: intraaortic balloon pump.
Table 4. Distribution of patients according to number of grafts received. No. of grafts
No. of patients
9 8 7 6 5 4 3 2 1
1 (0.2%) 4 (0.8%) 14 (2.6%) 56 (10.6%) 142 (26.8%) 189 (35.7%) 76 (14.4%) 40 (7.6%) 7 (1.3%)
Table 2. Indications for intraaortic balloon pump insertion. Indication
Preoperative
Intraoperative
Postoperative
Hemodynamic instability Arrhythmia Left ventricular failure Unstable angina Total
1
29
1
0 2
4 0
3 0
3 6
0 33
0 4
Table 3. Distribution of grafts in 529 patients. Grafts
No. of patients
Bilateral IMA grafts Total grafts per patient Arterial grafts per patient Vein grafts per patient
484 (91.5%) 4.2 3.8 0.4
IMA: internal mammary artery.
conversion was avoided in all 529 patients. Complete revascularization was achieved in all patients. There was no IABP-related complication in the patients who required IABP insertion. Table 3 shows the distribution of arterial and venous grafts. A total of 2256 grafts were created (range 1–9). Table 4 shows the distribution of patients according to the number of grafts they received; 406/529 (76.7%) patients received 4 or more grafts. Forty-seven patients who received 1 or 2 grafts had single-vessel disease of the LAD and received a graft to either the LAD alone (7 patients) or the LAD and diagonal.
Discussion OPCAB technique continues to evolve, particularly in India and other Asian countries.5 There are some
concerns about short and long term results of OPCAB compared to conventional on-pump coronary bypass grafting which was previously considered the gold standard for surgical revascularization. We tried to address the two key issues associated with OPCAB skepticism in this study: conversion to cardiopulmonary bypass, and completeness of revascularization.5 To prevent OPCAB conversion, we followed a standardized protocol in every patient. Using this protocol, we were able to treat 529 consecutive unselected cases of OPCAB with no conversions to cardiopulmonary bypass. It has been well established that the rate of conversion decreases with operator experience.1,6 It can be argued that many of the conversions are the result of a panic reaction by the surgeon or anesthetist or both. In view of the adverse outcomes of such conversions, the rate of conversion may be considered a surrogate performance indicator in OPCAB.1 Management of hemodynamic instability during OPCAB is not as complex as touted. Hypotension due to hypovolemia is easily treated by volume resuscitation. Just as hypotension due to myocardial infarction in cardiogenic shock is treated using IABP support, ischemic myocardial dysfunction-induced hypotension during OPCAB can also be managed by IABP, and thus avoid conversion. Ischemia-induced arrhythmias refractory to pharmacological agents can also be successfully treated with an IABP. There are reports of the use of a ventricular assist device to prevent OPCAB conversion.7 Many articles describe the use of prophylactic IABP in high-risk patients during OPCAB.8 We feel that with established femoral access, proper training and motivation of team members, and keeping an IABP on standby, IABP support can be started at very short notice. We feel routine prophylactic use of preoperative an IABP to facilitate OPCAB is unnecessary even in high-risk patients because we often observe an increase in systemic blood pressure and a decrease in cardiac filling pressure after graft flow is
Downloaded from aan.sagepub.com at University of Ulster Library on June 9, 2015
270
Asian Cardiovascular & Thoracic Annals 23(3)
established to ischemic coronary artery. Preoperative IABP insertion should be reserved for patients with unstable angina refractory to medical therapy, left ventricular failure, or cardiogenic shock. What constitutes complete revascularization remains controversial. It is often observed that the requirement of more than 3 grafts is considered an indication for an on-pump procedure rather than OPCAB.9 In our series, the average number of grafts per patient was more than 4, and 76% received 4 or more grafts. No diseased artery was left without a bypass graft because of a technical difficulty. Earlier revascularization of the posterolateral and inferior vessels used to be considered difficult during OPCAB, but with refinement of the technique, these vessels are being routinely grafted during OPCAB without any hemodynamic instability. Actually, we find grafting these vessels easier during OPCAB because no assistance is required to retract the heart as in on-pump grafting. We successfully performed 9 grafts in a patient with diffuse coronary artery disease. We feel that without the stress imposed by prolonged aortic crossclamp time or cardiopulmonary bypass time, complete revascularization can be performed more often than not. This is particularly true in patients with small vessels and diffuse coronary artery disease, which are prevalent in our part of the world. We sometimes even have to cut across a severely diseased segment and perform a long anastomosis using innovative techniques such as onlay patch plasty. It is obvious that such a long anastomosis will increase the cardiopulmonary bypass and clamp time and deter surgeons from performing complete revascularization. With OPCAB, our threshold for sequentially grafting the LAD has become low; for distal LAD disease, we use sequential left IMA grafts to the mid and distal LAD, whereas in on-pump coronary artery bypass, surgeons might be inclined to leave the distal LAD disease to medical management. Several limitations of our study should be recognized. The study was retrospective in nature. Moreover, it is the experience of a single surgeon with a strong bias for OPCAB. There was no control group of patients who required conversion to cardiopulmonary bypass. Further study on the use of IABP insertion to prevent OPCAB conversion is warranted. We concluded that complete revascularization and OPCAB conversion are interrelated. Apprehension of OPCAB conversion and its sequelae will always be in the mind of a surgeon while performing lateral wall revascularization. This is particularly true for a beginner in a low-volume center. The apprehension of OPCAB conversion can lead to incomplete revascularization. This may be the reason for the widespread reports of incomplete revascularization in OPCAB.5 The detrimental effects of conversion and incomplete
revascularization are well highlighted in the literature, but there are very few articles that provide a framework for prevention of emergency conversion in OPCAB. In our large series, we found that conversion can be avoided and complete revascularization in OPCAB is possible by timely and effective use of an IABP. Acknowledgments Presented at the annual meeting of The Society for Cardiothoracic Surgery in Great Britain and Ireland, Edinburgh, UK, March 10–12, 2014.
Funding This research received no specific grant from any funding agency in the public, commerical, or not-for-profit sectors.
Conflict of interest statement None declared.
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