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Eur J Cardiothorac Surg 2004;26:1118-1128
© 2004 Elsevier Science NL
Loma Linda University Medical Center, 11175 Campus Street, Suite 21121, Loma Linda, CA 92354, USA
Received 25 November 2003; received in revised form 11 June 2004; accepted 7 July 2004.
* Corresponding author. Tel.: +1-909-558-4354; fax: +1-909-558-0348. (E-mail: nwang{at}som.llu.edu).
| Abstract |
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| 1. Introduction |
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Nevertheless, the risk of surgical treatment in patients with severe left ventricular dysfunction and mitral insufficiency is still extremely high [3,7], and is further escalated in patients with prior CABG. In these patients, reoperation is fraught with potential hazards. Moreover, the amount of reversible myocardial disease is often uncertain, thus making surgical outcome unpredictable.
Although the risks of coronary reoperation in ischemic cardiomyopathy patients have been reported [810], until now, the additional impact of mitral insufficiency has not been well defined. It also has not been clear how mitral insufficiency affects the late survival of patients undergoing redo CABG. Does mitral insufficiency in fact produce the same effect, in terms of operative risks and late survival, on the redo CABG patients as it does on the initial CABG patients? And is it legitimate to extrapolate from initial CABG patients with mitral insufficiency the criteria and guidelines to treat redo CABG patients with mitral insufficiency?
To further our understanding of these patients, we retrospectively reviewed our 10-year operative experience in ischemic cardiomyopathy patients. Our goal was to determine the impact of mitral insufficiency on surgical risk and subsequent survival of redo CABG patients with severe left ventricular dysfunction. We also compare the effect of mitral insufficiency on survival of redo CABG patients versus initial CABG patients. The present study is in fact the first study that examines the impact of MR in ischemic cardiomyopathy patients undergoing redo CABG.
| 2. Materials and methods |
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Of the 891 CAGB patients, 708 were initial CABG patients (Initial) and 183 reoperative CABG patients (Redo). Significant mitral regurgitation (MR), defined as grade 3 or 4 on echocardiography, was present in 180 patients. Since the main objective of the present study was to determine the impact of MR on reoperative coronary surgery, the study cohort was subdivided into four groups (Table 1): Initial with absence of MR (Initial/MR), Initial with presence of MR (Initial/MR+), Redo with absence of MR (Redo/MR), and Redo with presence of MR (Redo/MR+).
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2.3. Surgical technique
Our approach to CABG operation has been previously described [11,12]. We routinely used blood cardioplegia with retrograde coronary sinus delivery. Because of severe left ventricular dysfunction, we also incorporated into the myocardial protection scheme the delivery of continuous warm blood cardioplegia during a portion of, or the entire aortic cross-clamp period in, many patients. The precise delivery protocols varied according to surgeon and case. In recent years, more beating heart CABG operations were performed. Consequently, 80 patients (9.0%) had no cardioplegic arrest: off-pump in 59 patients and no aortic cross-clamping in 21 patients.
The mean cardiopulmonary bypass time was 130±54min (28468min), and the mean duration of aortic cross-clamping was 82±34min (0230min). On average, 2.48±1.28 bypass grafts (16 grafts) per patient were performed and at least one arterial graft was used in 655 patients (73.5%).
Our approach to mitral insufficiency has evolved over time. Proportionally more mitral valves were repaired during the latter half of the study period. Posterior mitral annuloplasty was the principal repair technique. Over time, more CosgroveEdwards annuloplasty bands were implanted in preference to pericardial strips or other annuloplasty rings. Additional repair techniques (commissuroplasty, edge-to-edge leaflet approximation, and sliding posterior leaflet) were also more frequently utilized in recent years.
2.4. Statistical analysis
Data are summarized by frequencies and percentages for the discrete variables, and means and standard deviations for the continuous variables. Univariate analyses were performed by
2 or Fisher exact tests for the discrete variables and Student's t-tests for the continuous variables.
Late survival statistic was obtained using the KaplanMeier method. Univariate analyses using the log-rank tests were used to access the individual relationship of each variable to survival. Variables that are at least marginally associated with survival on univariate analyses (P<0.15) were used to develop multivariate Cox proportional hazard models. Variables that were independently associated (P<0.05) with survival were then determined using stepwise regression methods.
| 3. Results |
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3.1. Preoperative characteristics (Table 1)
There were only slight differences in the preoperative non-cardiac risk factors among the four groups. Of interest was the slight preponderance of diabetes mellitus in Initial patients and hypercholesterolemia in Redo patients. Renal insufficiency/failure was more prevalent in MR patients in both Initial and Redo patients. None of the non-cardiac co-morbidities were significantly different between Redo/MR+ and the other three groups.
MR patients had greater cardiac risk factors. Both Redo/MR+ and Initial/MR+ had more heart failure than angina symptoms. Both had lower mean EF and more patients were on inotropic support preoperatively. The only difference between Redo/MR+ and Initial/MR+ was the higher incidence of left main coronary artery disease in Redo patients.
3.2. Operative characteristics (Table 1)
Of the 180 patients with 3/4+MR, 126 (70%) had MV repair or replacement. Concomitant cardiac operation therefore occurred with much greater frequency in Redo/MR+ and Initial/MR+ patients and were associated with much longer cardiopulmonary bypass and aortic cross-clamped times. More than one-third of Initial/MR+ patients had CABG alone, and was mostly operated on earlier in the study. Not surprisingly, Redo/MR+ patients had the longest and the most complicated operations. Although Redo/MR+ had longer cardiopulmonary bypass time when compared to Initial/MR+, the two groups had almost identical cross-clamped time.
Urgent patients were most common in Initial/MR, Initial/MR+ and Redo/MR groups while Redo/MR+ had the largest proportion of elective patients. As expected, intra-aortic balloon pumps were least utilized in Initial/MR patients.
3.3. Survival outcome (Table 1)
With a mean follow-up period of 3.0 years, the overall survival (Fig. 1) of Redo/MR+ (n=39) was 41.7±9.2%, which was significantly worse than Redo/MR (n=144) of 71.8±4.1% (P=0.0003, Initial/MR+ (n=141) of 68.5±4.2% (P=0.014) and Initial/MR (n=567) of 76.2±2.0% (P<0.0001).
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3.5. Concomitant mitral operation
Concomitant MV repair and MV replacement were performed in 100 (Initial 75, Redo 25) patients, and 26 (Initial 18, Redo 8) patients, respectively. In Initial/MR+ patients, MV repair had significantly lower in-hospital mortality compared to MV replacement (MVRpr (n=8, 10.7%), MVRpl (n=5, 27.8%), P=0.0027). In Redo/MR+ patients, both MV repair and MV replacement had similar mortality (MVRpr (n=4, 16.0%), MVRpl (n=1, 12.5%), P=0.32).
Late survival in Initial patients was not impacted by mitral valve operation. Compared to Initial/MR patients, Initial/MR+ patients with MV repair had similar (P=0.16) late survivals (Fig. 4). Though Initial/MR+ patients with MV replacement had inferior late survival, statistical significance was not demonstrable due to the small number of late survivors in the subset. In contrast, MV repair (P=0.014) did not produce equivalent late survival benefit in Redo/MR+ patients (Fig. 4). MV replacement (P=0.0055) in Redo patients had the worst late survival.
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| 4. Discussion |
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The converse was observed in our redo CABG patients with ischemic cardiomyopathy. Significant (3/4+) mitral regurgitation clearly had a negative impact on both in-hospital and subsequent late survival. In this subset, mitral insufficiency and congestive heart failure were the only preoperative variables that were independent predictors of poor late survival in our multivariate analysis. Despite the relatively small number of redo CABG patients with mitral insufficiency, we were still able to demonstrate statistically the negative impact of mitral insufficiency on redo CABG late survival. In contrast, we were unable to demonstrate an independent influence of ejection fraction on late survival (Fig. 3) in the same patient subset. To our knowledge, this prognostic implication of mitral insufficiency in redo CABG had not been previously observed. Several recent studies on redo CABG [810] failed to consider mitral insufficiency as a potential variable with possible detrimental impact on outcome.
It is well known that patients with ischemic cardiomyopathy and mitral insufficiency have lower life expectancy and poorer quality of life. Indeed, in our series, mitral insufficiency was associated preoperatively with increased cardiac and renal co-morbidities in both the initial and the redo CABG patients. Yet mitral insufficiency affected late survival only in the redo CABG patients. Perhaps patients with prior CABG who also had low ejection fraction and mitral insufficiency were simply patients with the most advanced coronary artery disease and the greatest amount of irreversible myocardial damage. Compared to the initial CABG patients, the redo CABG patients probably had much less to benefit from revascularization and mitral valve operation, including mitral valve repair. Moreover, adding mitral valve operation to redo CABG would greatly increase the technical difficulty in these patients, further reducing the benefit-to-risk ratio. The results in our series seemed to support these assumptions. Neither redo CABG nor mitral insufficiency alone significantly altered the late survival (Fig. 2). Whereas patients with both redo CABG and mitral insufficiency showed a dramatic decrease in long-term survival.
It was gratifying to observe that mitral insufficiency did not have significant impact on long-term outcome in our initial CABG patients. In fact, patients with better ejection fraction (EF=2635%), late survival with and without mitral insufficiency were identical (Fig. 3). Conceivably, at least in the initial CABG patients, our surgical approach to mitral insufficiency, which included mitral valve repair, had been quite successful in ameliorating the poor late outcome generally associated with mitral insufficiency. Over the study period, our approach to mitral insufficiency in ischemic cardiomyopathy had evolved substantially. With each advancing year, proportionally more mitral valve repairs (n=99 (55.0%)) were performed in preference to no mitral valve operation (n=57 (31.7%)) or mitral valve replacement (n=24 (13.3%)). Majority of the untreated or mitral valve replacement patients were accrued during the earlier years of our experience. Overall, concomitant mitral valve replacement in our series was associated with high postoperative mortality with few late survivors. Mitral valve repair, however, showed a trend towards improved late survival in the initial CABG patients (Fig. 4). In this subset, concomitant mitral valve repair had yielded very similar late survival as initial CABG returns without mitral insufficiency. Conversely, concomitant mitral valve repair in redo CABG patients did not produce similar late survival benefit. Late survival was significantly worse in redo CABG patients regardless of operative approach to the mitral valve. We therefore, would advocate as other surgeons [14,15,16] in employing mitral valve repair, whenever possible, in ischemic cardiomyopathy patients with mitral insufficiency, but would expect much less favorable result in redo CABG patients compared to initial CABG patients.
Results of the present study have influenced our understanding and clinical approach to the surgical management of patients with ischemic cardiomyopathy. Our present surgical treatment has resulted in similar long-term benefit in the initial CABG patients, with or without mitral insufficiency, and the redo CABG patients without mitral insufficiency. Finer risk stratification is required in redo CABG patients with mitral insufficiency. Prior to embarking on high-risk reoperative coronary and mitral operation, this subset of patients would stand to benefit most from having additional viability studies such as PET scanning [1] or cardiac MRI imaging technique [17]. Hausmann and co-authors [18] had described several useful clinical variables that might aid in making the correct decisions in ischemic cardiomyopathy patients. Prior open-heart surgery was one variable to consider when deciding between revascularization versus transplantation. Based on the present series, perhaps only when mitral insufficiency was present in patients with prior CABG should transplantation be seriously offered as an alternative. Certainly, the decision would favor transplantation if such patients also had predominantly heart failure symptoms, relatively poor bypass targets, irreparable mitral valve and extremely low ejection fraction. In our series, late survival was particularly dismal in our redo CABG patients with mitral insufficiency and very low ejection fraction (EF<25%). Their 3- and 5-year late survivals were only 44.4 and 26.8%. Conceivably, novel options including destination therapy with mechanical devices might be explored, since the prognosis with medical treatment of most heart failure patients with cardiomyopathy and mitral insufficiency is dismal.
4.1. Study limitations
The present study has limitations similar to other retrospective analyses of a clinical database. Certain important clinical variables were not considered at the inception of the database. All patients had coronary artery disease and had CABG. All patients were presumed to have ischemic cardiomyopathy although some patients might have combined etiologies. In patients with mitral insufficiency, the exact etiology and the exact reason for reoperation were not recorded. The vast majority had ischemic mitral regurgitation and reoperations were performed primarily for ischemic reason rather than valvular disorder. There was considerable variability in the approach to mitral insufficiency and in the mitral valve operation. In the last few years, mitral valve repair has been the preferred treatment in our cardiomyopathy patients with mitral insufficiency. There was much less variability in the conduct of CABG. The majority had at least one arterial revascularization (73.5%). Only saphenous vein grafts were used in the remaining patients due to lack of suitable targets or conduits, or the need to simplify the operation in extraordinarily high risk patients. Myocardial protection consisted of retrograde delivery of cardioplegia in almost all patients (91%). Only recently were off-pump CABG done on these patients. Finally, outcome was all-cause mortality data. The precise causes of death in these patients were not readily available.
| 5. Conclusion |
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| Appendix A. Conference discussion |
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Dr Wang: We did not specifically look at this information in fine detail, but the majority of the patients were reoperated on because of coronary ischemia rather than valve insufficiency.
Dr Mohl: And all had retrograde cardioplegia, most probably, since you are coming from Loma Linda?
Dr Wang: Yes. Well, in the period of the study retrograde cardioplegia was used predominantly. Over the years, of course, we have done quite a bit of continuous warm retrograde cardioplegia as well, intermixed with the usual protocol, and varies considerably from surgeon to surgeon, and more recently we have done quite a few patients without cardiopulmonary bypass as well.
Dr G. Rizzoli (Padova, Italy): How long was the interval between operation and reoperation of your patients with grade 3 mitral incompetence at the first operation?
Dr Wang: Unfortunately, our database does not have that information as well.
Dr P. Sergeant (Leuven, Belgium): So you have not checked on these patients the date of the first valve because it wasn't in the database, is that correct?
Dr Wang: Yes. Our database does not relate the timing of their first operation.
Dr Sergeant: But you could check it?
Dr Wang: It would be very difficult to retrospectively go through these patients to get that information, but certainly that is something that could be done.
Dr Sergeant: If I understand you correctly, in the redo population the benefit of repairing the mitral valve was lost due to the increased mortality and morbidity with the mitral valve repair. How has that guided you for future therapy in your own institute?
Dr Wang: We are frequently referred patients who had previous operation(s) in severe congestive heart failure who had severe ischemic cardiomyopathy and significant mitral valve insufficiency. It is not always clear what would constitute the best treatment for these patients because many of them actually do not have a lot of anginal symptoms, nor do they have great coronary targets, and there is really no other dependable diagnostic tool which may be helpful.
In our practice at the present time, we would offer, or at least consider, transplant as one of the alternatives for this patient. But clearly many patients are poor transplant candidates who may not benefit from cardiac transplant. In those patients I think further risk stratification, based on clinical grounds, as well as perhaps studies as suggested by the previous speaker may be helpful. In general, if the patients has predominant anginal symptoms and heart failure is not the predominant symptom, we would still operate on them anticipating fairly good results.
It is the patient with previous operation that has poorly controlled heart failure with mitral insufficiency and poor targets that we would probably recommend comfort measures versus high-risk reoperation or even device theray if heart transplant is not an option.
Dr S. Silberman (Jerusalem, Israel): In the reoperation group did you look at the indications for surgery and graft patency of the old grafts? The main indications for the surgery, were they valve or were they for the revascularization? Could they be two different groups of patients?
Dr Wang: Most of the patients, the indication was for coronary ischemia as the main indication for reoperation.
Dr G. Ramasubrahmanyam (Hyderabad, India): What is the contribution of right ventricular failure causing mortality in this MR and redo surgery?
Dr Sergeant: Can you please repeat your question? We have not understood your question.
Dr Ramasubrahmanyam: What is the right ventricular failure which is producing the mortality in your series of patients?
Dr Wang: I think he was asking about right ventricular function.
Dr Ramasubrahmanyam: Yes.
Dr Wang: We are conducting a study in that regard looking retrospectively at echocardiograms that are available on these patients trying to determine if right ventricular function does play into the risk consideration in these patients. Intuitively I would expect biventricular failure patients not to do as well as isolated left ventricular failure patients.
| Acknowledgments |
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| Footnotes |
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| References |
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