Asian Cardiovasc Thorac Ann 2006;14:306-309
© 2006 Asia Publishing EXchange Ltd
Off-Pump Revascularization for Significant Left Ventricular Dysfunction
Y Joseph Woo, MD,
Todd J Grand, BS,
George P Liao, MB,
Corinna M Panlilio, BS
Division of Cardiothoracic Surgery, Department of Surgery, University of Pennsylvania, Philadelphia, USA
For reprint information contact: Y Joseph Woo, MD Tel: 1 215 662 2956 Fax: 1 215 349 5798 Email: wooy{at}uphs.upenn.edu, Division of Cardiothoracic Surgery, Department of Surgery, University of Pennsylvania School of Medicine, 6 Silverstein Pavilion 3400 Spruce St., Philadelphia, PA 19104, USA.
 |
ABSTRACT
|
|---|
Left ventricular dysfunction is a predictor of perioperative morbidity and mortality in on-pump coronary artery bypass grafting. Obligatory global myocardial ischemia and injury induced during crossclamping as well as adverse systemic effects of cardiopulmonary bypass may induce a disproportionately greater overall physiologic insult in patients with poor ventricular function. All patients undergoing nonemergency off-pump coronary artery bypass by a single surgeon during an 18-month period were retrospectively analyzed. Two groups with preoperative ejection fraction classified as poor (10%–35%; n = 31) or normal (55%–80%; n = 60) were compared. The mean ejection fractions were 26% ± 1% and 63% ± 1% respectively, p < 0.000001. In those with significant left ventricular dysfunction, there were 2.8 ± 0.1 grafts per patient, time to extubation was 8.4 ± 1.2 hours, and discharge was after 4.9 ± 0.6 days. These results were statistically equivalent to those in the group with normal left ventricular function. There was no intraaortic balloon pump insertion or mortality in either group. This technique provides an effective means of safely revascularizing patients with significant left ventricular dysfunction, and it may provide a valuable alternative approach in patients with ischemic cardiomyopathy.
|
INTRODUCTION
|
|---|
A large and increasing proportion of the total cardiovascular disease burden is attributed to heart failure, primarily of ischemic etiology.1 Significant morbidity and mortality due to ischemic heart failure is well documented. Revascularization in such patients with amenable coronary anatomy has yielded significant functional improvement.2,3 However, left ventricular (LV) dysfunction has been clearly shown to be a predictor of perioperative morbidity and mortality during conventional coronary artery bypass grafting (CABG) on cardiopulmonary bypass (CPB). The use of substantial inotropic and vasopressor support is difficult to quantify but is clearly a frequent and integral component of cardiac surgery in patients with significant LV dysfunction. The use of an intraaortic balloon pump (IABP) is a somewhat more definitive outcome, and in many settings, reflects the next step beyond inotropic support. In conventional on-pump CABG in patients with significant LV dysfunction, the need for an IABP ranges widely from 15% to nearly 70%, probably reflecting variability in prophylactic utilization.3,4 Perioperative mortality has been reported as 5%–15%.3–7 These and other indices of outcome are clearly worse than those observed among patients with normal LV function. Crossclamp-induced myocardial ischemia and adverse systemic effects of CPB may produce greater overall physiologic derangement in patients with ventricular dysfunction. Off-pump coronary artery bypass (OPCAB) obviates these factors and may provide a benefit.
Attempts to compare CABG on CPB with OPCAB in patients with significant LV dysfunction are encumbered by several limitations. Retrospective studies are subject to patient selection bias. In many clinical scenarios, patients at higher risk are referred specifically for OPCAB. Prospective randomized studies of CABG versus OPCAB are few, comprise less patients overall, and generally exclude those with significant LV dysfunction.8 Thus an alternative means of evaluating the potential benefits of OPCAB for patients with significant LV dysfunction would be to compare those with LV dysfunction undergoing OPCAB with patients with normal LV function undergoing OPCAB, a population which is known to have at least equivalent if not better outcomes compared to patients undergoing standard CABG.9,10
|
PATIENTS AND METHODS
|
|---|
All consecutive patients who underwent nonemergency OPCAB by one surgeon at a single institution during an 18-month period were retrospectively analyzed. Two groups with preoperative ejection fraction (EF) classified as poor (10%–35%; n = 31) or normal (55%–80%; n = 60) were compared. There were no exclusions. Patients in both groups had equivalent preoperative characteristics (Table 1
).
All patients underwent general endotracheal anesthesia and pulmonary artery catheter placement. After conduit harvest, the patients were systemically anticoagulated with heparin with a target activated clotting time of 400 sec prior to left internal mammary artery division. The heart was positioned with an apical suction device, and the target coronary artery was exposed with the aid of a suction stabilizer. The grafting sequence generally entailed grafting the internal mammary artery to the left anterior descending coronary artery, followed by right coronary/posterior descending artery grafting, and then circumflex/obtuse marginal grafting. In general, each distal anastomosis was followed by its corresponding proximal anastomosis to sequentially revascularize the heart. The exception to this sequence was an occluded right-sided coronary artery, which was bypassed first. The proportion of internal mammary artery-to-left anterior descending artery grafts as well as posterior target grafting was equivalent between the groups. The systemic blood pressure was maintained at 100 mm Hg during distal anastomoses, and at 60 mm Hg during proximal anastomoses. On completion of revascularization, heparin was reversed with protamine, usually requiring only half of the standard protamine dose used for CPB.8 Postoperative care, including weaning from mechanical ventilation, blood transfusion, and hospital discharge were conducted according to standardized protocols.
Values are expressed as mean ± standard error of the mean. Statistical analyses were performed using the Student t test and the chi-squared test. A value of p < 0.05 was considered significant.
|
RESULTS
|
|---|
Table 2 compares multiple perioperative parameters and outcomes. Other than EF, all values were statistically equivalent between groups. There were no differences in extent of revascularization, duration of mechanical ventilation, degree of postoperative bleeding, amount of blood products transfused, length of hospital stay, or mortality between the patients with normal LV function and those with severe LV dysfunction. One patient with normal LV function suffered a perioperative myocardial infarction. There was no intraoperative conversion to on-pump CABG, no reexploration, and no perioperative stroke in either group. No patient in either group required insertion of an IABP or ventricular assist device.
|
DISCUSSION
|
|---|
Ischemia, infarction, and subsequent loss of myocardial contractile mass are obvious mechanisms of heart failure. On the other hand, chronic myocardial ischemia that does not cause tissue loss can induce a spectrum of derangements in cardiomyocyte metabolism with marked uncoupling of energy consumption and work production, yielding an inefficient failing heart. In ischemic cardiomyopathy, high-energy phosphate stores are diminished.11 Decreased levels of myocardial creatine phosphate measured by 31P magnetic resonance spectroscopy correlate strongly with mortality.12 The activity of creatine kinase, which catalyzes phosphate transfer from creatine phosphate to adenosine diphosphate to form adenosine triphosphate, is also depressed.13 Ischemia can also trigger detrimental myocardial apoptosis.
Enhancing myocardial perfusion may reverse metabolic derangements, restore energy efficiency, and reverse heart failure. Patients with post-infarction heart failure who develop angiographic collateralization manifest improved regional ventricular function.14 Those with cardiomyopathy with anatomically amenable coronary disease benefit from revascularization. Weeks to months after successful revascularization, patients will often exhibit increased EF on transthoracic echocardiography.3,6,15 Patients also experience marked functional improvement; in one report, 89% of patients were in New York Heart Association functional class III or IV preoperatively, and 79% were in class I or II at 50 months postoperatively.6 Even at the extreme end of the LV dysfunction spectrum, (EF 10%–20%, mean 18%), patients can be operated on safely with reasonable mortality (11%), and also derive long-term myocardial functional benefit with a mean EF of 35% at 1-year follow-up.16 Patients with ischemic cardiomyopathy often have associated mitral regurgitation from annular dilatation and chordal tethering due to ventricular dilatation. Revascularization may also improve mitral regurgitation.15
The greatest challenge rests in successfully and safely revascularizing these patients. Perioperative mortality during CABG in patients with significant LV dysfunction has been reported as 5%–15%.3–7 Intraaortic balloon pump use, also a reflection of myocardial dysfunction, ranges from 15% to 70%.3–7 Among other factors, crossclamp time > 60 min and CPB time > 120 min were identified as predictors of mortality.6 The use of off-pump techniques avoids the obligatory global myocardial ischemia from aortic crossclamping. Off-pump coronary artery bypass also avoids the multiple systemic inflammatory effects of CPB, which may be particularly detrimental to patients with compromised ventricular function.17 Furthermore, those with significant LV dysfunction often have some degree of other organ dysfunction, especially liver and kidney, and thus may be more susceptible to exacerbation of such dysfunction by CPB. A retrospective comparison of on- and off-pump approaches in patients with LV dysfunction observed IABP rates of 14.7% vs. 7.5%, and mortality of 14.1% vs. 6.6%.4 Another retrospective study of patients with LV dysfunction found hospital mortality of 10.9% for CABG on CPB and 3% for OPCAB.18 A prospective registry of 48 patients with LV dysfunction undergoing OPCAB noted IABP use in 25% and a perioperative mortality rate of 7%.19 These studies suggest a benefit in employing OPCAB techniques.
Our results appear to improve on those reported not only for patients with LV dysfunction but also those with normal LV function undergoing OPCAB. We encountered no perioperative mortality nor any need to implant an IABP. Our postoperative length of hospital stay of 4.9 days in patients with LV dysfunction undergoing OPCAB is markedly less than the reported 7 to 9 days.18,20 The period of mechanical ventilation among our LV dysfunction OPCAB group of 8.4 hr was also less than the 16.5 hr reported previously.20 The percentage of patients requiring mechanical ventilation for > 24 hr was 26% in one study and 87% in another.4,18 Only one (3%) patient in our LV dysfunction group required ventilation exceeding 24 hr. The mean units of packed red blood cells transfused per patient was the same (1.5) as that in a previous report.20 Some groups have suggested that preoperative prophylactic IABP usage improves outcomes.3,5,7 Our results suggest otherwise. A limitation of OPCAB to revascularize patients with severe LV dysfunction is the inability to address significant functional ischemic mitral regurgitation. Although there are some reports of a reduction in mitral regurgitation after revascularization, this topic is controversial, and currently our patients with ischemic mitral regurgitation greater than 2+ undergo CABG and mitral valve reconstruction under CPB.
It was concluded from this study that patients with significant LV dysfunction undergoing OPCAB demonstrated excellent perioperative outcomes that exceeded those previously reported and were equivalent to outcomes in our patients with normal LV function. This technique may be very useful for the safe revascularization of patients with significant LV dysfunction.
Presented in part at the International Society of Minimally Invasive Cardiac Surgery 7th Annual Scientific Meeting, London, UK, June 23–26, 2004.
|
ACKNOWLEDGMENTS
|
|---|
This work was supported in part by NIH NHLBI/TSFRE HL072812 (YJW).
|
REFERENCES
|
|---|
- Beller GA. Coronary heart disease in the first 30 years of the 21st century: challenges and opportunities: The 33rd Annual James B. Herrick Lecture of the Council on Clinical Cardiology of the American Heart Association. Circulation 2001;103:2428–35.[Free Full Text]
- Pagley PR, Beller GA, Watson DD, Gimple LW, Ragosta M. Improved outcome after coronary bypass surgery in patients with ischemic cardiomyopathy and residual myocardial viability. Circulation 1997;96:793–800.[Medline]
- Elefteriades JA, Morales DL, Gradel C, Tollis G Jr, Levi E, Zaret BL. Results of coronary artery bypass grafting by a single surgeon in patients with left ventricular ejection fractions < or = 30%. Am J Cardiol 1997;79:1573–8.[Medline]
- Al-Ruzzeh S, Athanasiou T, George S, Glenville BE, DeSouza AC, Pepper JR, et al. Is the use of cardiopulmonary bypass for multivessel coronary artery bypass surgery an independent predictor of operative mortality in patients with ischemic left ventricular dysfunction? Ann Thorac Surg 2003;76:444–52.[Abstract/Free Full Text]
- Bouchart F, Tabley A, Litzler PY, Haas-Hubscher C, Bessou JP, Soyer R. Myocardial revascularization in patients with severe ischemic left ventricular dysfunction. Long-term follow-up in 141 patients. Eur J Cardio-thorac Surg 2001;20:1157–62.[Abstract/Free Full Text]
- Lslamoglu F, Apaydin AZ, Posacioglu H, Ozbaran M, Hamulu A, Buket S, et al. Coronary artery bypass grafting in patients with poor left ventricular function. Jpn Heart J 2002;43:343–56.[Medline]
- Selim Isbir C, Yildirim T, Akgun S, Civelek A, Aksoy N, Oz M, et al. Coronary artery bypass surgery in patients with severe left ventricular dysfunction. Int J Cardiol 2003;90:309–16.[Medline]
- Woo YJ, Atluri P, Grand T J, Hsu V, Gardner TJ. Should standard on-pump protamine dosing formulas be recalculated for off-pump coronary artery bypass grafting? Heart Surg Forum 2004;7:42–4.[Medline]
- Puskas JD, Williams WH, Duke PG, Staples JR, Glas KE, Marshall JJ, et al. Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of stay: a prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting. J Thorac Cardiovasc Surg 2003;125:797–808.[Abstract/Free Full Text]
- Puskas JD, Williams WH, Mahoney EM, Huber PR, Block PC, Duke PG, et al. Off-pump vs conventional coronary artery bypass grafting: early and 1-year graft patency, cost, and quality-of-life outcomes: a randomized trial. JAMA 2004;291:1841–9.[Abstract/Free Full Text]
- Ingwall, JS, Atkinson, DE, Clarke, K, Fetters, JK. Energetic correlates of cardiac failure: changes in the creatine kinase system in the failing myocardium. Eur Heart J 1990;11(Suppl B):108–15.[Abstract/Free Full Text]
- Neubauer S, Horn M, Cramer M, Harre K, Newell JB, Peters W, et al. Myocardial phosphocreatine-to-ATP ratio is a predictor of mortality in patients with dilated cardiomyopathy. Circulation 1997;96:2190–6.[Abstract/Free Full Text]
- Nascimben L, Ingwall JS, Pauletto P, Friedrich J, Gwathmey JK, Saks V, et al. Creatine kinase system in failing and nonfailing human myocardium. Circulation 1996;94:1894–901.[Abstract/Free Full Text]
- Ejiri M, Fujita M, Sakai O, Miwa K, Asanoi H, Sasayama S. Development of collateral circulation after acute myocardial infarction: its role in preserving left ventricular function. J Cardiol 1990;20:31–7.[Medline]
- Tolis GA Jr, Korkolis DP, Kopf GS, Elefteriades JA. Revascularization alone (without mitral valve repair) suffices in patients with advanced ischemic cardiomyopathy and mild-to-moderate mitral regurgitation. Ann Thorac Surg 2002;74: 1476–81.[Abstract/Free Full Text]
- Carr JA, Haithcock BE, Paone G, Bernabei AF, Silverman NA. Long-term outcome after coronary artery bypass grafting in patients with severe left ventricular dysfunction. Ann Thorac Surg 2002;74:1531–6.[Abstract/Free Full Text]
- Menasche P. The systemic factor: the comparative roles of cardiopulmonary bypass and off-pump surgery in the genesis of patient injury during and following cardiac surgery. Ann Thorac Surg 2001;72:S2260–6.[Abstract/Free Full Text]
- Goldstein DJ, Beauford RB, Luk B, Karanam R, Prendergast T, Sardari F, et al. Multivessel off-pump revascularization in patients with severe left ventricular dysfunction. Eur J Cardio-thorac Surg 2003;24:72–80.[Abstract/Free Full Text]
- Eryilmaz S, Corapcioglu T, Eren NT, Yazicioglu L, Kaya K, Akalin H. Off-pump coronary artery bypass surgery in the left ventricular dysfunction. Eur J Cardio-thorac Surg 2004;21:36–40.
- Shennib H, Endo M, Benhamed O, Morin JF. Surgical revascularization in patients with poor left ventricular function: on- or off-pump? Ann Thorac Surg 2002;74:S1344–7.[Abstract/Free Full Text]
TOP
ABSTRACT
INTRODUCTION
