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Ann Thorac Surg 2007;83:2029-2035
© 2007 The Society of Thoracic Surgeons
Division of Thoracic and Cardiovascular Surgery, University of Virginia, Charlottesville, Virginia
Accepted for publication January 22, 2007.
* Address correspondence to Dr Fedoruk, Division of TCV Surgery, University of Virginia Health System, PO Box 800679, Charlottesville, VA 22908-0679 (Email: lfedoruk{at}telus.net).
Presented at the Fifty-third Annual Meeting of the Southern Thoracic Surgical Association, Tucson, AZ, Nov 8–11, 2005.
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Abstract |
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Methods: A retrospective analysis of University of Virginia patients from January 2000 until September 2006 was undertaken. Patients with CABG and an ejection fraction less than 35%, ischemic mitral regurgitation by operative characterization, and patients with LVR were identified. The Society of Thoracic Surgeons database risks, complications, and outcomes as well as degree of revascularization, quality of targets, and type of additional procedures were analyzed. Incomplete revascularization was defined as a planned bypass not performed. Poor targets were defined as per the operative note.
Results: In all, 382 patients were identified (220 CABG, 97 CABG/MVR, and 65 LVR). The overall operative mortality was 7.9%. Mortality was 9.1% for CABG, 8.2% for CABG/MVR, and 3.1% for LVR. Preoperative risk factors for mortality included diabetes mellitus (p = 0.05), previous cerebrovascular disease (p = 0.05), and chronic renal dysfunction (p = 0.03). Patients with emergency operations had a significantly increased mortality (p < 0.001) as did patients with intra-aortic balloon pumps (p = 0.015).
Conclusions: Additional procedures such as MVR or LVR did not add to the operative risk of CABG for ischemic cardiomyopathy. Only preoperative comorbidities and emergency operations increased operative mortality.
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Introduction |
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Heart failure is a complex syndrome that results from myocardial dysfunction that impairs the heart’s ability to circulate blood at a rate sufficient to maintain the metabolic needs of the bodies tissues. Once compensatory mechanisms are exhausted, a progressively worsening clinical course characterized by fatigue, fluid retention, dyspnea, and shortened survival occurs [3].
There are a multitude of causes of heart failure; however, ischemic cardiomyopathy is responsible for approximately 70% of the cases [4, 5]. Therapeutic strategies aimed at the treatment of heart failure are primarily medical, focused on the treatment of acute exacerbations. Long-term pharmacologic therapies (angiotensin-converting enzyme inhibitors, digoxin, ß-adrenergic blockers) [6–8] have somewhat improved the grim prognosis of a 50% mortality 5 years after diagnosis [9] to a 50% mortality at 8 years [10]. The addition of mitral regurgitation decreases the already bleak survival to less than 40% at 1 year [11, 12]. Ultimately, medical therapy does not treat the underlying cause.
Allman and colleagues [13], in their meta-analysis, demonstrated a survival advantage for surgery versus medical therapy in patients with viable myocardium. At present, no clear surgical algorithm exists for the treatment of ischemic cardiomyopathy. Both transplantation and revascularization are established therapies. Unfortunately, as part of the altered ventricular geometry secondary to infarction and remodeling, patients often have concomitant ventricular akinesis or mitral regurgitation that adds surgical complexity. Many believe that this significantly increases already high operative risks.
This study examines our patients with ischemic cardiomyopathy who were not transplant candidates. We assessed the preoperative characteristics, operative risks, and associated mortality of various surgical options in the treatment of ischemic cardiomyopathy: coronary artery bypass grafting (CABG), CABG and mitral valve repair (CABG/MVR), and left ventricular remodeling (LVR) with or without CABG. We examined the hypothesis that additional procedures increased the risk in patients with ischemic cardiomyopathy. We also examined the hypothesis that surgery for congestive heart failure does not require left ventricular assist device standby, and finally, we determined whether preoperative variables such as the urgency of operation had an impact on the surgical outcome.
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Material and Methods |
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Exclusion criteria included concomitant aortic valve disease requiring aortic valve replacement or a nonischemic cause for mitral regurgitation as noted on the operative report. Patients with acute mitral regurgitation from papillary muscle rupture were also excluded. All preoperative risk factors, operative variables. and postoperative outcomes as defined by The Society of Thoracic Surgeons (STS) database were analyzed. The degree of revascularization, quality of targets, and type of additional procedure were analyzed. A chart review was performed to assimilate all data not in the STS database. Incomplete revascularization was defined as a planned bypass not performed. Poor targets were defined as per the operative note. Overall operative mortality was defined as death within 30 days of operation and was confirmed by institutional contact or telephone interview.
Patients with identified coronary artery disease were assessed for revascularization. Angina was used as a surrogate for viability in the majority of the patients who underwent CABG. If a patient presented with heart failure symptomatology alone, viability was assessed with either technetium-99m sestimibi or thallium scans. Rarely, magnetic resonance imaging or 18F-fluorodeoxyglucose positron emission tomography scanning was used to assess viability.
Moderate-severe (3+ or greater) mitral regurgitation and symptoms of heart failure were indications for operation in this cohort. Significant (>50% stenosis) coronary artery disease was also treated. As well, patients who presented with angina and had identified 3+ or greater mitral regurgitation were provided surgical treatment of the regurgitation.
Patients who demonstrated severe left venricular dysfunction and regional akinesis or dyskinesis (aneurysm) of the anterior wall and apex by echocardiogram or ventriculogram in conjunction with heart failure were considered candidates for a remodeling procedure. The decision was made preoperatively and confirmed at the time of surgery. At the time of operation, the left ventricle was assessed. Intraoperative examination that demonstrated an akinetic or aneurismal segment by characteristic dimpling or flattening of the anterior wall after aortic cross clamp was applied and LV vent was applied was considered an indication for remodeling.
Three hundred and eighty-two patients (292 male, 90 female) met the criteria and were divided into three groups determined by their operative procedure: CABG, CABG/MVR, or LVR (Dor) with or without CABG.
Surgical Technique
Intraoperative transesophageal echocardiography was performed in all cases before cardiopulmonary bypass and cardioplegic arrest to evaluate the left ventricular (LV) and mitral valve function unless there was a contraindication to use. Standard cardiopulmonary bypass techniques were utilized. Cold blood cardioplegia was used in all procedures in an antegrade, retrograde, or combined fashion dependent on surgeon preference. A "hot shot" was routinely given before removal of the cross clamp.
In the CABG procedures, attempts were made to use a left internal mammary artery to left anterior descending artery graft in all cases. The bypass strategy was surgeon dependent; however, rarely was a second arterial graft utilized. Saphenous vein bypass grafting was routinely performed.
The LVR procedure performed was either an exclusion technique utilizing an intracardiac patch as described by the RESTORE group [15] or by modified linear closure [16]. In all cases, the anterior aspect of the left ventricle was opened and the akinetic or aneurismal segments excluded. All LVR procedures were performed under cross clamp.
All mitral valve procedures were performed either through the left atrium through Waterston’s groove or by a transseptal approach. In each case, the operative report noted the mechanism of regurgitation to be ischemic in origin. If the valve was replaced, a chordal-sparing technique was employed, and sutures were placed from the ventricle to the atrium. Five bioprosthetic and 3 mechanical mitral valves were placed. When the valve was repaired, a semirigid partial or complete ring was placed using interrupted 2-0 braided annular sutures. Valve sizing was planned to undersize the annulus by two sizes; however, it was surgeon dependent. A saline infusion test was performed to ensure the adequacy of the repair before closure.
Patients were weaned from cardiopulmonary bypass in standard fashion. Ionotropes and intra-aortic balloon pumps (IABP) were utilized as necessary. Immediate post–cardiopulmonary bypass transesophageal echocardiography was then performed to confirm adequacy of the repairs and to assess ventricular function. Postoperatively, the patients were taken to the thoracic and cardiovascular surgery intensive care unit. Standard postoperative care was provided.
Statistical Analysis
Independent statistical analysis of patient characteristics and postoperative outcomes between the two groups were performed with a two-sample Student t test, Fisher’s exact Test, or a test of two proportions. All p values are two-tailed. The results are presented as means ± SD in the test and tables. Where applicable, a 
2 test was used for comparison of proportions. All values are expressed as the mean ± SD unless otherwise indicated. All p values less than 0.05 were considered significant.
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Results |
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TopAbstractIntroductionMaterial and MethodsResultsCommentDiscussionReferences |
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Preoperative viability studies were also performed in 27 patients who underwent remodeling procedures. All of these demonstrated no viability in either the apical region or the anterior and apical areas; 30.8% of this cohort had an identified aneurysmal region of the ventricle defined by ventriculogram or echocardiogram. The remainder had akinetic segments.
Postoperative mechanical support was utilized in a small number of patients. Sixty-five patients (17%) required an IABP; however, 46 of these were present before the operation (70.8%). There were 15 deaths when an IABP was utilized, with 8 of the IABPs placed preoperatively. Only 3 patients in the entire cohort (0.8%) failed to wean from cardiopulmonary bypass and required extracorporeal membrane oxygenation (ECMO). One of the 3 survived. No patient had a ventricular assist device placed.
There were 30 deaths within the early postoperative period (30 days), and the cause of death is listed in Table 9. Twenty-three percent (n = 7) of our patients died of cardiac causes, with 2 of the 7 failing to wean from cardiopulmonary bypass. In each of these cases, a decision was made not to place the patient on ECMO because of significant comorbidities. The most common cause of death was multiorgan failure.
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Comment |
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The outcomes associated with ischemic cardiomyopathy are generally worse than other types of cardiomyopathy (eg, dilated, hypertrophic) [17, 18]. That is most likely secondary to the progressive nature of coronary artery disease as well as the association with diabetes mellitus, hypertension, and peripheral vascular disease.
Established therapy for the treatment of ischemic cardiomyopathy includes medical treatment, conventional cardiac surgical techniques, and heart transplantation. Some investigators have suggested that patients with severe ischemic cardiomyopathy may have better outcomes with transplantation as compared with conventional surgery [19]. Unfortunately, this option is available for only a select few, with fewer than 10% of patients eligible receiving transplantation. Others have demonstrated that transplantation for ischemic cardiomyopathy is associated with an operative mortality of 11.2% and poor 10-year survival (39%) [20].
It has been well demonstrated that lower ejection fractions are predictors of higher mortality among patients after CABG. Perhaps as importantly, the larger LV volumes seen in cardiomyopathy are also strongly associated with more adverse outcomes [21, 22]. Several studies have demonstrated higher mortality rates among patients with ischemic cardiomyopathy, lower ejection fractions, and mitral valve procedures [23, 24]. A recent study from our institution demonstrated significantly higher usage of IABP in patients undergoing LV restoration when the ejection fraction was less than 25% [25]. Furthermore, a study from Germany in 1997 demonstrated a 3.1% use of biventricular assist devices (Berlin Heart) in a high-risk CABG cohort [26]. Because of these and other studies, there has been a bias to refer patients with ischemic cardiomyopathy to centers with left ventricular assist device support.
Our overall IABP usage was 17%, and 15 of our 30 deaths had an IABP. Interestingly, the majority of the IABP placed were done so in the preoperative period. That is related to the institutional bias regarding the placement of these devices for preoperative stabilization by our cardiology service. Although ECMO was used in a very small number of our cases (0.8%), no patients were considered for left ventricular assist device therapy.
The initial results of the Surgical Anterior Ventricular Endocardial Restoration trial [15] demonstrated a requirement for postoperative mechanical support in a small number of patients: 7.7% required IABP, 1.3% required ECMO, and 0.05% required left ventricular assist device support. Although it is recognized that patients with low preoperative ejection fractions are at a higher risk for low cardiac output syndrome postoperatively [27], we believe that left ventricular assist device backup is not a necessity for this group of patients. However, postoperative mechanical support for low cardiac output syndrome with IABP counterpulsation and ECMO should be readily available as a short-term backup in critical situations.
Surprisingly, our study has demonstrated no difference in operative mortality between CABG and CABG with the addition of an LVR procedure or a mitral valve procedure, or both. If anything, there was higher mortality (albeit not statistically significant) in the CABG group. This was found despite a fairly reasonably matched cohort of patients with similar ejection fractions and preoperative characteristics. The overall operative mortality of 7.9% is quite reasonable given the severity of illness of the patients and certainly similar to transplant mortality of as high as 11%, confirming conventional surgery as a viable option to transplantation. Previously, Hausmann and coworkers [26] have demonstrated improved survival with CABG as compared with transplantation for "end-stage coronary artery disease." In general, at our institution, cardiac transplantation is reserved for patients who have dilated cardiomyopathy, patients with demonstrated lack of viability, and patients who have failed standard cardiac surgical procedures.
We attribute the similarities in outcome to the finding that although patients who required restoration procedures or mitral repairs had more complex procedures, they also had multiple reasons for LV dysfunction. Patients with mitral repairs had the regurgitant volume essentially eliminated, improving the effectiveness of contraction. Remodeling procedures remove the large areas of diastolic dysfunction and noncompliance, significantly improving the effective stroke volume acutely. Although CABG does provide immediate revascularization, stunned and hibernating myocardium can take a significant period (measured in months) to show significant improvement [28].
Two of the most significant factors associated with predicting operative outcomes were preoperative creatinine levels and the degree of urgency of our procedures. Elevated preoperative creatinine is a well-recognized clinical variable associated with increased mortality, especially if associated with worsening postoperative renal function requiring dialysis [29]. Patients who were taken emergently to the operating theater had a vastly worse outcome than did patients whose surgery was defined as elective or even urgent. These patients were also had by far the highest rate of IABP usage and all patients who were placed on ECMO were done emergently. The acuteness of illness associated with the acute ventricular decompensation portends an unstable situation and a grave prognosis. The SHOCK trial demonstrated a 47% surgical mortality among patients taken to the operating theater with cardiogenic shock, and certainly some of the patients in this trial would meet the SHOCK trial criteria for enrollment [30].
This study has several limitations. It is retrospective and not randomized. The numbers are relatively small. There is the potential for significant surgical bias. The results demonstrate only outcomes in the immediate 30-day postoperative period.
In conclusion, ischemic cardiomyopathy is best served by surgical management. The type and complexity of procedure performed should not influence management decisions, as we have demonstrated similar outcomes in all three surgical options: CABG, CABG and mitral valve repair or replacement, or LVR (Dor) with or without CABG. This group of patients may require an IABP for their management and postoperative mechanical support is rarely necessary. Emergent procedures have a significant impact on operative outcomes and may portend a grave prognosis.
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Discussion |
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I was impressed with a couple of things in your paper. First of all, that the overall mortality was less than 10% in this group of people who, based on their age alone, would have made them transplant candidates, but the fact that they were not candidates and you still had that kind of greater than 90% survival is very impressive. If you look at any medical papers in equally sick patients, and I am assuming most of these patients are class III and IV, although you really didn’t say that, we know that class III and IV heart failure patients have upwards of 50% to 80% 2-year mortality. So your outcomes are very good.
I was struck by the fact that you used balloon pumps in such a small percentage of patients who were generally very, very sick patients. I know in my own series of patients who were class III and IV, I have balloon pumps used in about 45% of the patients, and I find it absolutely necessary to get these people through the operation. So the question based on that is, how sick were these people based on their function? Were they all class III and IV? The ejection fraction is certainly a moving target, particularly in people who are actively ischemic. So try to give me a handle on how sick these people really were.
Secondly, why do you think that the CABG population had the highest mortality? If these people had no other concomitant procedures, I would think that they don’t have mitral regurgitation, they don’t have large areas of akinesis or dyskinesis that is going to be a power suck on the ventricles in these patients, so why did those patients not do well? Was it because they were incompletely revascularized to a greater degree than those patients who had mitral repairs or ventricular remodeling?
Thirdly and finally, I think I have some disagreement with your conclusion that ventricular assist devices aren’t needed. The majority of your patients who didn’t survive had balloon pumps put in, and the fact that they didn’t survive from there and they had low output states, which probably led to their multisystem organ failure, I would think that with greater support you may have been able to circumvent the left pump failure causes of death by having a ventricular assist device in those patients. I look forward to your answers and, again, congratulations on a very nice paper.
DR FEDORUK: Thank you, Dr Conte. To answer the first question about the degree of heart failure, more than half of our patients in this study were defined urgent or emergent by the STS definition, and when I went back and did a chart review trying to come up with that answer, I just couldn’t get a good handle on exactly what the functional class of these patients were. We received a significant number of patients from outside institutions who were transferred to the cardiac care unit (CCU) because of the need for intensive medical therapy, and we had perhaps 24 hours of preoperative information on them, and these patients were all fairly acutely ill. It was very difficult to get a sense of what their chronic New York Heart Association class was. It does make it difficult to assess them when they are in the CCU and they are dyspneic, and you could say they are all New York Heart class III or New York Heart class IV in that setting.
As far as the question about why our patients with CABG did worse, it was not secondary to incomplete revascularization. It is more likely that although patients that required a left ventricular restoration procedure or mitral repair had multifactoral reasons for ventricular dysfunction, more was done to fix the ventricle and improve the efficiency of contraction acutely. In the case of the remodeling procedures, the "power suck," as you so aptly describe it, is removed. With the mitral repairs, the regurgitant volume is essentially eliminated, improving the degree of effective contraction.
In terms of the final question with regard to the left ventricular assist device usage, perhaps this was underutilized. However, I looked at all the patients and tried to categorize their deaths. I agree with you that when you say that patients die of multiorgan system failure it is perhaps a marker of cardiogenic shock. However, having said that, most of the deaths defined as multiorgan failure were considered in the intensive care unit spiral, in the sense that if they had started to wean off the inotropes and then developed pneumonia or sepsis, things like that that altered their recovery, that is when I was categorizing them as multiorgan failure. I would disagree that multiorgan failure is always a surrogate for cardiogenic shock.
DR HORMOZ AZAR (Norfolk, VA): Congratulations on a very nice study and nice presentation. I have two questions. What were the guidelines used to make a decision regarding ventricular remodeling in some patients? How did you go about selecting those patients? These are all very sick patients with various segmental dysfunction.
DR FEDORUK: In general, patients with ventricular remodeling were chosen based on preoperative left ventriculograms demonstrating an aneurysm or dyskinetic segment. If we got into the operating room and applied suction to the ventricle and saw a significant dimpling suggestive of transmural infarction and aneurysm or an akinetic area, these patients tended to be opened and a remodeling procedure performed.
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References |
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TopAbstractIntroductionMaterial and MethodsResultsCommentDiscussionReferences |
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