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Eur J Cardiothorac Surg 2001;20:937-948
© 2001 Elsevier Science NL

Long-term results of coronary artery bypass grafting procedure in the presence of left ventricular dysfunction and hibernating myocardium

^a Cardiac Surgery Division, Civic Hospital, 25125 Brescia, Italy
^b Cardiology Division, Civic Hospital, 25125 Brescia, Italy
^c Nuclear Cardiology Division, Civic Hospital, 25125 Brescia, Italy
^d Biomedical Statistics, University of Brescia, Brescia, Italy

Received 5 December 2000; received in revised form 11 July 2001; accepted 20 July 2001.

Corresponding author. Tel.: +39-030-3384031; fax: +39-030-3995004
e-mail: roberto_lorusso{at}iol.it

	Abstract

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 
Objective: Long-term left ventricular (LV) performance and patient outcome after coronary artery bypass grafting (CABG) procedure in the presence of depressed LV function and hibernating myocardium (HM) have been poorly determined. Therefore, we prospectively evaluated patients undergoing CABG with severe LV dysfunction and HM to elucidate postoperative prognosis. Methods: We enrolled 120 consecutive patients undergoing CABG with severe LV dysfunction and HM as assessed by dobutamine echocardiography and by rest-redistribution radionuclide (Thallium-201) study. Mean patient age was 60±9 years (range 31–77 years). Mean preoperative LVEF was 28%±9 (range 10–40%). All patients underwent echocardiographic study to assess LV recovery of function intraoperatively, prior to hospital discharge, at 3 months, at 1 year, and yearly during the follow-up. Univariate and multivariate analysis were performed to to evaluate predictors of postoperative survival. Results: There were 2 hospital (1.6%) and 15 late (12.5%) deaths, mainly for heart failure, leading to an actuarial survival of 80±6% and 60±9% at 5 and 8 years, respectively. LVEF significantly improved perioperatively (from 28±9% to 40±2%, P<0.01). Increase in LVEF, however, was gradually offset over the time (EF of 33±9%, 32±8%, and 30±9% at 3 months, and 12 months, and 8 years after surgery, respectively). Furthermore, patients who experienced limited LV functional recovery perioperatively had a more remarkable decline of LVEF thereafter, and suffered from recurrence of heart failure symptoms (freedom from heart failure 82±5% and 60±8% at 4 and 8 years respectively). Advanced preoperative NYHA Class, and age were independent risks factors for reduced postoperative survival. Preoperative angina and use of arterial conduits apparently did not influence patient morbidity and mortality at long term. Conclusion: CABG procedure in the presence of HM enhances LV recovery of function and has a favourable prognosis. Functional benefit of the left ventricle, however, appears to be time-limited, despite remarkable improvement in patient functional capacity. Advanced preoperative heart failure, minimal perioperative improvement of LVEF, and age account for a poor long-term prognosis.

Key Words: Coronary artery bypass grafting • Hibernating myocardium • Left ventricular dysfunction • Ischemic cardiomyopathy • Postoperative prognosis

	1. Introduction

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 
Surgical revascularization in patients with severe left ventricular (LV) dysfunction provides survival benefit as compared to medical therapy at long term [1,2]. Despite recovery of impaired myocardial function has been shown after coronary artery bypass grafting (CABG) [1–7], contractile dysfunction of the LV remains a negative determinant of postoperative outcome [2,5,8]. Recently, the presence of akinetic yet viable myocytes, peculiar condition denominated hibernating myocardium [9] (HM), showed to characterise subgroup of patients having higher probability of improvement in LV function and more favourable postoperative survival after revascularization [10–15]. The likelihood of predicting reversible myocardial dysfunction has gained enormous relevance among the investigators, and techniques capable of identifying HM have been, therefore, a critical component of the diagnostic process to select patients for conventional methods of myocardial revascularization despite advanced LV dysfunction, with important implications either on early and on late postoperative results or allocation of alternative therapies [15]. Preoperative clinical condition has been also associated with postoperative outcome, being the preoperative presence of angina a positive predictor of improved life expectancy despite impaired LV performance as compared to patients with heart failure symptoms, and usually linked to viable and recoverable myocardium [1]. However, despite the impact of depressed LV function on CABG results has been largely highlighted and the importance of patient selection variably underscored, scarce information are available on the actual outcome of CABG in patients affected by LV dysfunction and HM. The long-term benefits of such a surgical therapy in this peculiar setting of myocardial compromise are, therefore, still undefined as are the potential predictors of unfavourable late LV function and patient survival. Our study prospectively enrolled patients characterised exclusively by LV impairment and HM. The results of such a follow-up are herein reported.

	2. Methods

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 
From February 1989 until April 2000, 120 consecutive patients were enrolled for this prospective study. Inclusion criteria consisted of presence of severe LV dysfunction (EF40%), evidence of ample segments of hibernating myocardium involving at least the territories of the anterior descending coronary artery (LAD), graftable coronary vessels, elective surgery, absence of acute myocardial infarction (less than 1 month prior to surgery). Preoperative patient characteristics are summarised in Table 1. Heart failure symptoms (NYHA Class III or IV) were present in 43% of patients preoperatively. Diabetes mellitus was present in 29 patients (34.8%). Concomitant mitral valve insufficiency was present in 29 patients (trivial in 10 patients, mild in 15 patients, moderate in two patients and severe in two patients, respectively), requiring mitral valve repair (annular remodelling with prosthetic ring) in three patients. One patient had had associated aortic valve disease and had undergone aortic valve replacement. Ten patients had had mechanical circulatory support (intraortic balloon counterpulsation) prior to CABG procedure, but were not under mechanical assistance at the time of surgery. Two patients had had implantable defibrillator (AICD) implantation prior to CABG procedure due to malignant ventricular arrhythmia. One-vessel disease was present in five patients, two-vessel disease in 37 patients, and tree-vessel disease in 78 patients, respectively.

2.2. Surgical management
Because of a wide time span, surgical strategies varied along the study course, particularly with regards to myocardial protection. Indeed, cardiac arrest was induced by different techniques, as described in Table 2. A change in CABG conduits also occurred during the study period since patients in the first series underwent myocardial revascularization with vein conduits only (36 patients), whereas arterial graft (internal thoracic artery) was used almost routinely to perfuse the LAD territories in the most recent series series (84 patients). Complete coronary revascularization was achieved in almost all patients of operated patients (2.8±0.8 grafts/patient).

2.4. Statistical analysis
All values are presented as mean±standard deviation. Linear mixed models for repeated measures were performed to predict postoperative trend of LV function. Univariate and multivariate analysis were performed to disclose predictive variables for patient survival. Variables considered for univariate and multivariate analysis were as follows: patient age and gender, history of and location of previous myocardial infarction, primary symptoms (angina or heart failure symptoms), use of left internal thoracic artery (LITA) or vein grafts for the anterior descending coronary artery, LVEF, pulmonary hypertension, diabetes, NYHA Class, percentage of intraoperative increase in LVEF, number of distal anastomosis, extracorporeal circulation and aortic cross-clamping times, route and type of cardioplegia.

	3. Results

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 
Mean follow-up was 3.8±6 years (range from 3 months to 9 years) and no patient was lost during follow-up. There were two hospital (1.6%) and 15 late (12.5%) deaths, leading to an actuarial survival of 84±6% and 60±9% at 4 and 8 years, respectively (Fig. 1). Causes of postoperative deaths are presented in Table 2. The majority of late deaths were due to chronic heart failure and occurred in patients with preoperative end-stage heart failure and more severe impairment of LV function. Remarkably, sudden death did not represent a frequent postoperative event in this study population, with only three arrhythmic-related deaths during follow-up, despite frequent premature ventricular beats present at the preoperative electrocardiogram and lack of prophylactic medical therapy to prevent arrhythmia postoperatively.

View larger version (13K): [in this window] [in a new window]   Fig. 1. The figure shows estimated survival (Kaplan–Meyer) probabilities of the 120 patients with impaired LV function and hibernating myocardium following CABG procedure. Dashed lines enclose the 70% confidence limits.

View larger version (18K): [in this window] [in a new window]   Fig. 3. This figure shows the survival (A) and heart failure recurrence (B) probability after coronary artery bypass according to different degree of preoperative impaired LVEF. There was a reduced life expectancy at mid-term, whereas heart failure occurred more frequently at late follow-up in patients with worse preoperative LVEF. LVEF, left ventricular ejection fraction.

View larger version (13K): [in this window] [in a new window]   Fig. 2. This plot shows the actuarial freedom from recurrence of heart failure after coronary artery bypass grafting in the presence of hibernating myocardium. Dashed lines enclose the 70% confidence limits.

The use of arterial conduits for (LAD) revascularization did not apparently exert additional benefit to postoperative outcome. Indeed, survival, heart failure or angina recurrence rate were not modified by the use of left thoracic artery to revascularize the LAD territories (Fig. 4), although postoperative evaluation was performed with a limited mean follow-up. Repeated revascularization (PTCA) because of recurrence of angina was necessary only in three patients. No repeated CABG was performed along the follow-up. In terms of predictors of postoperative outcome, univariate analysis showed that ECC and aortic cross-clamping times, together with advanced symptoms of heart failure and age were predictive of unfavourable outcome, whereas Cox model of multivariate analysis showed that only advanced preoperative NYHA Class and age were risks factors for reduced postoperative survival (Table 3). Preoperative symptoms had variable impact on postoperative survival. Indeed, patients who were particularly compromised preoperatively (NYHA Class III or IV) had worse prognosis, whereas the presence of preoperative angina did not influence patient survival or the recurrence of heart failure (Fig. 5).

View larger version (16K): [in this window] [in a new window]   Fig. 4. The influence of the use of LITA (yes) on patient survival (A) and freedom from heart failure (B) is shown. No substantial impact of the use of arterial conduit for reperfusing the anterior descending coronary artery territories could be found up to 9 years from surgery. LITA, left internal thoracic artery.

View larger version (17K): [in this window] [in a new window]   Fig. 5. This figure shows the influence of preoperative angina on postoperative outcome of patients submitted to coronary artery bypass grafting with depressed cardiac function and hibernating myocardium. No difference was found in relation to patient survival (A) or to recurrence of postoperative heart failure (B) when ischemic symptoms where present (yes) or absent (no).

	4. Discussion

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

4.1. Assessment of hibernating myocardium and patient selection
Myocardial akinesis is not an irreversible condition in coronary artery disease. Indeed, the presence of functional myocardial inactivity has been shown to be associated, in particular conditions, with preserved myocyte structure and ‘freezed’ contractile function. This condition, denominated ‘hibernating’ myocardium, represents a sensitive predictors of recovery once blood perfusion has been restored in these zones [9–15]. The prevalence of patients affected by marked compromise of LV function associated with hibernating myocardium may be as high as 50% of the total population having ischemic cardiomyopathy [17], clearly underlining the relevance of identifying this peculiar myocardial condition in therapeutic decision making.

However, predicting the likelihood of myocardial recovery and postoperative prognosis of patients undergoing coronary artery bypass with depressed LV function and HM remains a challenge [18]. Noninvasive tests to establish the presence and the amount of HM have shown to be paramount for accurate patients selection and more favourable postoperative results to be achieved [11,12,14,15,17], but are still under refinement [18,19]. Apparently, functional tests (that is, dobutamine or other inotrope-related stress-test echocardiogarphy) reliably indicate potential for early LV recovery of function following CABG, whereas metabolic investigations (that is, rest-redistribution radionuclide tests or PET) are more intimately related to long-term results. In our study, dobutamine echocardiography and Thallium-201 rest-redistribution scintigraphy showed to be valuable methods to identify HM and predict favourable postoperative outcome. However, predicting the extent and the maintenance of functional improvement remains a difficult task. Indeed, despite objective evidence of adequate quote of HM, perioperative results were not confirmed at late follow-up. Our study did not include a comprehensive evaluation of myocardial histology. As demonstrated by Shivalkar and associates, only structurally preserved and perfused myocytes show substantial postrevascularization recovery [14]. Accordingly, noninvasive evaluation of HM must parallel structural integrity, otherwise neither significant nor durable recovery of LV function, and then patient outcome, can be achieved. Recently, La Canna showed that a simple acquisition of a basic echocardiographic parameter, namely preserved diastolic thickness, invariably correlates with successful surgical revascularization [19], having echocardiographic stress test or radionuclide assessment a complementary role in establishing potential of LV recovery. Myocardial wall thickness at echocardiography, indeed, has been shown to correlate well with histological findings obtained at intraoperative biopsy from HM segments [20]. The apparent maintenance of myocardial thickness and myocyte function, either metabolically or pharmacologically evidenced are, therefore, the gold standard for patient selection in this setting,

4.2. Patient survival and mode of death
Surgical revascularization has shown to be superior as compared to medical therapy in patients with impaired LV function either with regards to life expectancy or to LV functional recovery also when HM is not specifically established for patient selection [1–3]. However, long-term information of patients with impaired LV function and HM submitted to CABG are still scarce. Our clinical series represents, therefore, a relevant experience since highly selected patients, with proved myocardial hibernation associated with compromised LV function, were enrolled and prospectively followed up. Patient survival, in our series, was 60% at 8 years, showing a better outcome as compared to previous series, which, however, variably included patients without an established presence of HM at the preoperative assessment. It is, therefore, reassuring that conventional therapy, provided that accurate patient selection is carried out, may still have a primary role in the treatment of ischemic cardiomyopathy. Surgical revascularization appeared to influence also the mode of death, since the majority of late fatal events were due to congestive heart failure whereas a few deaths occurred because of malignant arrhythmia. This finding is in contrast to previously reported data concerning mode of death in patients affected by ischemic cardiomyopathy undergoing surgical revascularization. Indeed, arrhythmia-related events have been related to postoperative deaths in 60–100% of the cases [5,21], or have been commonly associated with late morbidity. In addition, our results should be further highlighted by the lack of any prophylactic therapeutic regimen to reduce or prevent ventricular arrhythmia. We can assume, therefore, that, despite the marked compromise of cardiac function, which is usually considered a predisposing factor to life-threatening arrhythmic events, the presence of revascularized HM in patients with ischemic cardiomyopathy appears to play a protective role by reducing the occurrence of malignant ventricular arrhythmia and, hence, of sudden deaths.

4.3. Left ventricular recovery of function and heart failure recurrence
Our data confirmed that substantial improvement of contractile performance was shown immediately after revascularizing impaired LV myocardium if adequate amount of HM is present. Nonetheless, the recovery of LV function, in our series, was neither quantitatively uniform nor stable along the time. The explanation for such a variable result may be multifactorial. As previously stated, myocardial structure of the hypocontractile segments plays a critical role in functional recovery, being the limited presence of fibrotic tissue a positive predictor of LV functional improvement following CABG [14]. The presence of well developed coronary collateral net was also shown to predict restoration of segmental wall motion [22]. Our series showed that CABG procedure in the presence of appropriate extent of HM and positive response to preoperative echo-stress test accounts for significant LV improvement at short term. Furthermore, patients with worse preoperative LV function had limited perioperative LV recovery, had a rapid decline in improved LVEF, and had more frequent recurrence of heart failure symptoms, high hospital admittance rate, and reduced survival. It can therefore be speculated that patients who had this less than optimal result, despite preoperative assessment of HM, might have had major structural derangement within the akinetic or hypocontractile zones, with expected limited benefit after blood perfusion was restored or with gradual loss of recovered myocardial function due to progressive myocyte degeneration. It appears, therefore, that CABG reduces postoperative death-related events, but does not protect against the progression of ischemic cardiomyopathy in some patients. The time-limited beneficial effects of CABG in the presence of LV dysfunction was also shown by Luciani, who showed a 47% of patient free from heart failure symptoms at 5 years, despite a 75% of survival at the same follow-up timing [23]. This series, however, included only 48% of patients with preoperative assessment of myocardial viability, making the performance of CABG in patients with irreversibly damaged myocardium likely. It is, therefore, unquestionable that more homogeneous clinical series are still needed to further elucidate the optimal patient selection process in the decision making of ischemic cardiomyopathy, and, on the other hand, it should be taken into account that other determinants may contribute to unfavourable postoperative outcome or to transient benefit of myocardial revascularization. The recurrence of heart failure, for instance, may be due to several factors which have no relation to preoperative patient characteristics: postoperative coronary or myocardial disease progression, incomplete myocardial revascularization with limited reperfusion of potentially recoverable segments, postoperative graft disease, intraoperative-induced myocardial damage, are all factors which may act singly or in combination limiting or hampering the benefits obtained by the CABG procedure. It is conceivable that the etiology of patient death and recidivant episodes of heat failure in this peculiar setting may be multifactorial and, as such, extremely complex to disclose.

4.4. The influence of type of CABG conduit
The choice of conduit has been previously shown to influence postoperative morbidity and mortality in routine CABG experiences. The recent trends in CABG procedure have clearly favoured the use of arterial conduits, not only to perfuse the LAD coronary artery, also in patients with impaired cardiac function. Jegaden and coauthors, however, recently reported on potential unfavourable effects of extensive use of arterial grafts as compared to more conventional surgical management (LITA plus vein grafts) to revascularize patients affected by impaired LV function, documenting increased rate of perioperative complications and no benefit as far as survival was concerned [24]. The lack of benefit by using arterial grafts to perfuse ischemic cardiomyopathy was shown by other investigators [1,25]. Conversely, Luciani and coworkers showed that the use of LITA grafts appeared to be a positive predictor of reduced heart failure events or recurrence in patients with depressed LV performance [23]. This is in contrast to our findings since we could not document any benefit in terms of life expectancy, heart failure or angina recurrence in patients with LV dysfunction and HM when arterial grafts were used. Attrition rate of CABG conduits may affect recovery of myocardial function, but no reports, to our knowledge, have shown reduced benefit of CABG procedure in this particular setting or have objectively documented heart failure recurrence due to recidivant myocardial dysfunction or hibernation secondary to graft disease. On the other hand, longest follow-up in our study was limited to 9 years, and benefits from arterial revascularization are well known to exert an impact on a longer run. Recatheterization is, however, underway at our Institution and will hopefully provide meaningful insights on potential correlation between graft disease, and thus, benefit of arterial grafts, and postoperative outcome at medium and long term.

4.5. Preoperative predictors of late outcome
The complexity of accurately identifying additional predictors, other than the presence and extent of HM, is self-explanatory in patients who usually present several additional risk factors for unfavourable post-CABG results. Preoperative symptoms have been claimed to be associated with postoperative outcome. The presence of angina has been shown to predict better survival rate and more consistent improvement in LV function [7]. However, Di Carli and collaborators showed that also patients with depressed LV function and no or minimal anginal symptoms undergoing surgical revascularization did better than patients treated medically, despite results were less favourable than the angina group, provided that PET mismatch could be detected in akinetic areas1. In this study, however, viability assessment was not performed in all patients, with obvious implication on patient selection. Our study population, which included exclusively patients with evidence of HM, showed no difference in terms of mortality or heart failure recurrence regardless the presence of ischemic-related symptoms. These findings are in accordance with the study reported by Dreyfus who showed the importance of viability tests instead of clinical evaluation as crucial determinant for effective patient selection and subsequent postoperative outcome [26]. However, our study did show that preoperative heart failure symptoms and advanced impairment of functional capacity were independent predictors of poor prognosis, although HM was invariably detected in all the selected patients. This apparently contradictory finding stresses, once again, the importance of adding additional clues with regards to the need of obtaining more accurate information about extent of myocyte structural derangement. It is arguable that advanced heart failure conditions be more likely associated with wider areas of irreversible structural abnormalities and smaller amount of preserved yet hibernated myocyte structure.

Our study showed also that increased age was a significant predictor of unfavourable outcome, like previously demonstrated by other investigators [27,28], making the therapeutic decision making in elderly patients affected by ischemic cardiomyopathy extremely controversial since other additional alternatives, like heart transplantation, would also be contraindicated.

4.6. Study limitations
This series represents a prospective non-randomized study. Patients were selected exclusively for CABG procedure and according to the presence of adequate amount of HM. Therefore, they were not randomly assigned to different type of therapeutic management. Changes in operative strategies along the study course also occurred and, thus, may have influenced postoperative results and related data interpretation. Postoperative assessment was not complete in regards to quality of coronary revascularization and graft patency, since not all patients were submitted to recatheterization along the follow-up, making the interpretation of causes of unfavourable outcome potentially misleading if merely directed to preoperative factors since relevant postoperative factors might have intervened with marked impact on patient survival and LV function. Echocardiographic assessments were all performed by two experienced echocardiographists (G. L.C., C. C.), but no intra-observer variation was performed with potential influence on echocardiographic data interpretation.

In conclusion, our findings indicate that, despite LV dysfunction, the presence of HM confers low postoperative mortality and potential LV functional benefits to patients submitted to CABG. The advantage of CABG to perfuse functionally impaired myocardium in selected patients may also encompass an anthyarrhythmic effect, since a few sudden deaths were encountered, as compared to patients with chronic heart failure medically treated or surgically treated where HM was not detected. Several preoperative factors, however, may account for transient LV recovery of function with subsequent reappearance of heart failure. Furthermore, the perioperative augmentation of LVEF, even if remarkable, appears to be hardly maintained over the time with a trend towards progressive reduction of the LV hemodynamic performance, and the underlying mechanism warrant further investigation. Conduit choice for coronary bypass did not represent, in our study, a critical factor in patient outcome if LV impairment is present. Recent developments in diagnostic assessments will ensure adjunctive information for more appropriate patient selection in this complex settings and, therefore, better postoperative results and account for more favourable allocation of alternative therapeutic resources.

	Acknowledgments

 
We gratefully acknowledge the invaluable contribution of Dr. O. Alfieri to the initial part of this experience, and the support of ‘Associazione CUORE e Ricerca’.

	Footnotes

 
Presented at the 14th Annual Meeting of the European Association for Cardio-thoracic Surgery, Frankfurt, Germany, October 7–11, 2000.

	Appendix A. Conference discussion

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 
Dr. P. Sergeant (Leuven, Belgium): I have two questions and I would like to ask them in a consecutive fashion and allow you to answer each one first. We were a little bit disappointed, probably you also, at the loss of gain after a few months after surgery. What is your analysis of that observation?

Dr Lorusso: Unfortunately because of time constraints I couldn't show. We had a group of patients, the very initial group of patients, 30 patients, were resubmitted to coronary angiography, and I can tell you that of 30 patients, 10 patients had early graft disease, and these patients had a high recurrence rate of heart failure and less benefit from surgery. Unfortunately I couldn't show this data because they were really a small sample size. But I think that early graft disease may play a critical role in patient outcome, because most people think that when you have recurrence of heart failure it is because the diagnosis was probably not appropriate, so the hibernating myocardium was not amenable for recovery, but it is not the case. It can be that just the graft closed. And so it's a bet on hibernating myocardium probably. So this is I think the reason why we observed this limited and gradual limited benefit.

Dr Sergeant: If you allow me to continue in fact on the same line of thinking, should we have a more aggressive approach in the follow-up of these patients?

Dr Lorusso: Absolutely. Thank you for your comment and question. I do think that these patients are a little bit peculiar in this respect. Whenever you have a failure, whatever, I mean, a recurrence of arterial symptom, recurrence of angina, they are not submitted to an aggressive diagnostic process, because they say, well, what we could gain is death, so if nothing happens we cannot do that much. But probably it is not true. We should investigate again, because probably these patients have only graft disease and then can be again treated. So we should be more aggressive.

Dr Sergeant: So we should not wait for a return of left ventricular failure, we should not wait for events, but just reanalyze and make new observations?

Dr Lorusso: Sure.

Dr W. Flameng (Leuven, Belgium): There is not much known about the late outcome of hibernating myocardium after revascularization. You might be aware that we published a few years ago an extensive study in circulation where we correlated the ultrastructure of the hibernating myocardium with functional outcome after grafting. We found that in the hibernating myocardium there are two subpopulations. One subpopulation is characterized by a completely normal myocardium and the other by an increase in extracellular matrix surrounding the viable myocytes. I guess that it is mainly in this population of patients you see the bad outcome after revascularization. We could define them preoperatively by PET scanning: these patients do not have the classical mismatch.

Do you have any data on that?

Dr Lorusso: Of course your paper is a key reference in my manuscript. We did as well histologic assessment of these patients, and we found, of course, that the patient who had less benefit had a higher degree of apoptosis in the portion of hibernating myocardium areas. Unfortunately we do not have PETs, and so the assessment, the tools we had to screen these patients were again echocardiography and radio nucleoid studies. But I totally agree with you that with the PET mismatch and with the structural analysis of these patients we could probably further improve the identification of the patient or, let's say, the reason why some patients had such a temporary improvement and not maintain a stable increase in left ventricular ejection fraction.

Dr A. El Banna (Cairo, Egypt): Thank you for the nice presentation. The first question is, do you suggest using an intra-aortic balloon during induction of anesthesia with poor ventricular function or not?

The second question is, if you have scars in the myocardium, do you suggest using volume reduction techniques to help these patients?

Dr Lorusso: Thank you for your questions. First of all, this data about perioperative outcome will be presented in the afternoon, but nevertheless, I can tell you that I think we should use a little bit more the intra-aortic balloon pump, especially in the patients, of course, with a more delicate, unstable hemodynamic situation and with a poor left ventricular ejection fraction, just because you would like to reduce as much as possible the negative event in the perioperative phase, like acute myocardial infarction, which, unfortunately we cannot give an answer in this respect, could play a role, an additional role, in the outcome of these patients, because of course you can have some damage. So what you can gain by CABG you can lose by inducing a perioperative myocardial infarction. So I think in the peculiar patient setting I would use more the intra-aortic balloon pump, preoperatively and postoperatively.

As far as the second question, sorry?

Dr El Banna: Do you adopt volume reduction techniques?

Dr Lorusso: No. We used just one case, but so far we did not have experience in this respect. I believe that it can be an adjunct in your armamentarium, but still we do not have any evidence that this can be important in, let's say, patient outcome. So it is difficult to say. We do not have experience anyhow.

Dr P. Gerometta (Bergamo, Italy): I would like to ask you whether the perioperative left ventricular ejection fraction increase could be due to a better medical therapy (i.e. intravenous drug) or intensive care, and if you have any data regarding preoperative mitral insufficiency in these patients: have you systematically treated it or not?

Dr Lorusso: Well, as far as mitral insufficiency, we did not have many patients with mitral insufficiency, which could be strange in patients with dilated ventricles. So due to this small number, I cannot give you a definitive conclusion.

And the first one?

Dr Gerometta: It was about whether the left ventricular ejection fraction increase could be attributed just to a better medical therapy.

Dr Lorusso: I think that you can have many reasons. You know that in the perioperative phase you can have a catecholamine release, which could play even a major role in terms of left ventricular ejection fraction and performance. We tried to analyze the neural hormones produced in a few patients, and I can tell you that there are some trends that show that you have a higher release of catecholamines, which can explain partially why you have such a nice improvement perioperatively, which is not shown at three months, but, still, three months you have a significant increase in the left ventricular performance maintained. So this is not certainly related to an acute release of catecholamines.

So I think that it can be the acute effect of the surgery, the high increase, but this increase is maintained at three months and one year, and then after, you have a decrease. I think the progression of the disease, of the cardiomyopathy, can play a major role in this respect.

Dr G. Mani (New Delhi, India): Through the follow-up that we are having in the off-pump group being subjected, I mean patients with poor LV being subjected to off-pump, we are already noticing a difference in their postoperative follow-up, and I was wondering whether this is correlated to the drop in the diastolic pulmonary artery pressure, which we see more obviously in the off-pump surgery as compared to our previous bypass operations. I would like to know your comments.

Dr Lorusso: In the discussion of the manuscript we took into consideration the fact that in these patients, of course, probably the off-pump technique could give an additional help; we still don't know. Because trying to avoid any additional damage due to cardiopulmonary or total myocardial ischemia can be important, too, but certainly we do not have evidence to support that.

And I would say that looking at the patient who develops recurrence of heart failure symptom afterwards due to graft disease, I believe that if you can provide complete revascularization and appropriate revascularization with off-pump, then you can probably do that in these patients, but if you cannot reproduce the same thing you can achieve in the CPB patients, I think it can be really tricky, because then you can have incomplete revascularization or you can have probably a higher rate of graft diseases, stenosis of the anastomosis. I do not want to say that off-pump is less effective, but you have to take into consideration that you have to be really very complete in revascularizing a hibernating myocardium to have the most benefits, the biggest benefits.

	References

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion Appendix A. Conference... References

 

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