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European Journal of Heart Failure 2003 5(1):85-93; doi:10.1016/S1388-9842(02)00089-2
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© 2002 European Society of Cardiology

Prognosis of patients with chronic coronary artery disease and severe left ventricular dysfunction. The importance of myocardial viability

Jaroslav Meluzína,*, Jan Cernyb, Lenka Spinarováa, Jirí Tomana, Ladislav Grocha, Frantisek Stetkab, Milan Frélichb, Petr Hudea, Jan Krejcía, Lada Rambouskováa and Roman Panovskya

a First Department of Internal Medicine, Masaryk University St. Anna Hospital, Pekarská 53, Brno, Czech Republic
b Center of Cardiovascular and Transplant Surgery St. Anna Hospital, Brno, Czech Republic

* Corresponding author. Tel.: +420-5-4318-2224; fax: +420-5-4318-2205


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 References
 
Background and aim: The choice of optimal treatment strategy in patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction is often difficult. The aim of this study was to compare long-term results of patients with chronic CAD, severe heart failure and a defined scope of myocardial viability treated with coronary revascularization, heart transplantation, or kept on medical therapy.

Methods: From 1993 to 2000, viability evaluation using low-dose dobutamine echocardiography was performed in 124 patients with CAD and LV ejection fraction ≤30%. The dysfunctional myocardial segments were defined as viable if they exhibited improvement in their thickening at any dose of dobutamine or worsening without initial improvement. The patients were divided into five groups and followed up for a mean period of 27±23 months. Group A consisted of 39 patients with viability (at least two dysfunctional but viable segments) who were revascularized. Group B consisted of 29 patients with viability treated medically. Groups C (n=23) and D (n=22) comprised patients with non-viable dysfunctional myocardial segments who were revascularized or kept on medical therapy, respectively. Eleven patients referred for heart transplantation after dobutamine echocardiography and 62 patients with ischemic cardiomyopathy transplanted in the same time interval were included in the group of transplanted patients (Group E).

Results: The Kaplan–Meier survival analysis demonstrated a significantly better survival of group A patients as compared with group B patients (P<0.05). The prognostic benefit of revascularization in patients with viability was not manifested until 3 years after the procedure. At 5 years, survival in groups A, B, C, D and E was 89, 60, 67, 50 and 78%, respectively.

Conclusion: In patients with CAD, severe LV dysfunction, and the evidence of viability in dysfunctional myocardium, coronary revascularization improves survival. At least 3-years follow-up is necessary to objectively assess the prognostic effect of coronary revascularization.

Key Words: Coronary artery disease • Viability • Prognosis • Dysfunction

Received August 16, 2001; Revised September 17, 2001; Accepted December 17, 2001


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 References
 
Despite advances in modern medicine, the treatment of patients with coronary artery disease (CAD) and severe left ventricular (LV) dysfunction still represents a serious problem. These patients have high mortality and morbidity and their treatment is expensive with only suboptimal results. During the last decade, many authors have demonstrated that ventricular dysfunction may not always be an irreversible process but, in a relatively large proportion of patients, it represents an adaptation to chronic hypoperfusion—so-called myocardial hibernation. Such a myocardium has the potential for functional recovery after coronary revascularization resulting in the improvement of the patients’ functional class as well as prognosis [1,2]. Dobutamine echocardiography, which exhibits a good sensitivity and specificity in predicting functional recovery after coronary revascularization [3], has become one of the established methods to identify viability in dysfunctional myocardium. The large clinical importance of the assessment of myocardial viability is due to the fact that viability is supposed to be present in more than 50% of dysfunctional myocardial segments [4]. Thus, the assessment of viability may identify a large cohort of patients with heart failure to whom coronary revascularization offers a large benefit. On the other hand, the risk of bypass surgery significantly increases with gradual decrease in LV ejection fraction (EF) and with signs of heart failure, and some patients may benefit more from heart transplantation or from medical therapy. To date, there have been only a few reports comparing different treatment strategies in patients with heart failure and a defined amount of viable myocardium. In addition, most of these studies included not exclusively patients with severely depressed LV function, but also those with only moderate dysfunction [5–9]. Thus, the aim of our study was to compare long-term results in patients with chronic CAD, severe heart failure (EF ≤30%), and a defined level of myocardial viability, treated with coronary revascularization, heart transplantation, or kept on medical therapy.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 References
 
2.1. Characteristics of the patients
Between 1993 and 2000, a total of 162 consecutive patients with LV EF ≤30%, who were potential candidates for coronary revascularization, underwent dobutamine echocardiography for viability evaluation. One hundred and thirty of them fulfilled the following criteria: (1) LV EF ≤30% as assessed by echocardiography; (2) luminal diameter narrowing ≥50% of at least one major coronary artery on coronary angiography; (3) no myocardial infarction or unstable angina pectoris within 6 weeks before dobutamine echocardiography; (4), the ability to evaluate regional wall motion of all 16 myocardial segments with echocardiography; (5), no cardiac disease except CAD and no need for aneurysmectomy. Sixty-six patients were referred for coronary revascularization, 13 for heart transplantation; the remaining 51 patients were advised to continue on medical therapy. The decision on therapy was made on the basis of clinical criteria (the presence and severity of angina pectoris) and the result of coronary angiography (number of stenotic coronary arteries, number of bypassable arteries). In patients with prevailing symptoms of heart failure having minimal or no angina, who were investigated within the last 3 years, the result of dobutamine echocardiography was, in addition, taken into account in selecting the treatment strategy. Patients with significant viability (four or more dysfunctional but viable segments) were referred for coronary revascularization. However, the result of dobutamine echocardiography was used for the decision on the treatment strategy in only 24 (18%) patients, of whom only two died during the follow-up. Patients who had cardiac events in the interval between dobutamine echocardiography and coronary revascularization (two patients) or heart transplantation (two patients) were excluded from the study. We also excluded two patients in whom vessels supplying normokinetic segments were revascularized, while stenotic arteries supplying dysfunctional segments with preserved viability could not be revascularized because of their insufficient runoff. Thus, the final cohort comprised 124 patients: 119 men and five women. Their mean age was 57±9 years (range, 41–81), LV EF 25±4% (range, 15–30%). One hundred and sixteen (94%) had a history of myocardial infarction, 68 (55%) were treated for hypertension, 79 (64%) for hypercholesterolemia and 46 (37%) for diabetes. Eighty-eight (71%) patients suffered from stable angina pectoris and 86 (69%) exhibited symptoms of heart failure defined by the presence of shortness of breath at rest or on exertion and the need for diuretic and/or digitalis therapy. All patients gave their informed consent to dobutamine echocardiography and written consent to coronary angiography, coronary artery bypass grafting surgery, coronary angioplasty, or heart transplantation. The study protocol was approved by the Institutional Ethics Committee and the study conformed with the principles outlined in the Declaration of Helsinki.

2.2. Coronary angiography
Selective coronary angiography was performed in multiple views using standard techniques within 1 week before dobutamine echocardiography. The severity of coronary stenoses was expressed as the percent of luminal diameter narrowing. Significant CAD was defined as ≥50% diameter stenosis of at least one major coronary artery.

2.3. Dobutamine and follow-up echocardiography
Standard transthoracic and low-dose dobutamine echocardiography was performed in the left lateral decubitus position. Dobutamine was administered intravenously with an infusion pump at doses of 5 and 10 µg/kg per min each for 5 min. Parasternal long-axis view, parasternal short-axis views at the base, papillary muscle and apex levels and apical 2- and 4-chamber views were recorded at rest and at both doses of dobutamine on VHS videotape for subsequent off-line analysis. Follow-up standard echocardiography was obtained 3–6 months (mean 4±1) after coronary revascularization.

2.4. Echocardiographic analysis
Regional wall motion was assessed using a 16-segment model recommended by the American Society of Echocardiography [10]. Myocardial segments were scored with the following scale: 1=normal or hyperkinetic; 2=hypokinetic; 3=akinetic; and 4=dyskinetic, with scoring by visual analysis of systolic wall thickening. Wall thickening was assessed at a distance of ≥1 cm from the adjacent segment to minimize the effect of tethering. The dysfunctional segments were defined as viable if they exhibited functional improvement of at least one grade with any dose of dobutamine, or if they exhibited worsening without initial improvement [2,11,12]. Patients were considered to have viable myocardium, if they had at least two such adjacent segments. A change from dyskinesis to akinesis was not considered to be improved wall motion; similarly the opposite change in wall motion was not considered to be worsening. The volumes and EFs were calculated as an average of three to five consecutive heart cycles using the biplane Simpson's method [10]. Regional wall motion analysis and EF calculations were performed off-line from videotapes by readers who were blinded to patients’ data. All EF calculations were done by one experienced echocardiographer (J.M.). Regional wall motion was assessed by consensus of two experienced observers (J.M. and L.S.). Interobserver and intraobserver variabilities of these readers have been published previously [13] and attained 93% concordance for the scoring of 800 segments and 92% concordance for identifying the presence of contractile reserve of 121 dysfunctional segments, respectively. Intraobserver variability was concordant for wall motion scoring in 769 of 800 segments (96%), and for the presence of contractile reserve in 115 of 121 segments (95%), respectively.

2.5. Coronary revascularizations and heart transplantations
Coronary revascularizations were performed within 3 months after dobutamine echocardiography. Of 62 revascularized patients, 54 underwent coronary artery bypass grafting and eight were treated with coronary angioplasty. Heart transplantations were performed according to Lower and Shumway [14] or using the bicaval technique [15]. Patients referred for transplantation were in symptomatic heart failure of NYHA functional class III or IV, exhibited severe LV systolic and diastolic dysfunction and had peak oxygen consumption during spiroergometry <14 ml/kg per min.

2.6. Follow-up
Forty-nine revascularized or medically treated patients and all transplanted patients were regularly followed up in 3–6-month intervals in our institution. The remaining patients were interviewed by telephone, by mail using a questionnaire, or information was acquired from the referring physician. The patients were followed up for cardiac and all-cause mortality and non-fatal cardiac events including myocardial infarction, unstable angina pectoris and hospitalization for heart failure. Cardiac death was defined as death due to heart failure, myocardial infarction, malignant arrhythmias, or cardiac arrest. In patients who died out of hospital and in whom autopsy was not performed, a sudden unexpected death (within 1 h of the onset of symptoms) was attributed to a cardiac cause. Myocardial infarction was defined as a hospital admission for prolonged (>20 min) chest pain, electrocardiographic changes and at least a twofold increase in plasma enzyme activity. Unstable angina pectoris was defined by resting anginal symptoms requiring hospitalization with parenteral nitrates and/or heparin therapy (no cardiac enzyme elevation or new Q-waves on the electrocardiogram). Heart failure requiring hospitalization was identified by dyspnea, need for inotropic and/or diuretic therapy, and by symptoms associated with left (rales on lung auscultation, S3 gallop) and/or right (neck vein distension, ankle edema, hepatomegaly) heart failure. In the case of death or cardiac event, admitting departments or referring physicians were contacted to elucidate the exact reason for hospitalization or cause of death. The follow-up started on the day of resolution to treat medically, in medically treated patients, or on the day of procedure in revascularized and transplanted patients. The follow-up data were available from all patients.

2.7. Statistical analysis
Clinical and echocardiographic data are given as a mean±S.D. for continuous variables or as a number (percent) for categoric variables. Comparisons were performed for LV EFs before and after coronary revascularization and for patient groups defined according to the presence of viability and the mode of treatment. The differences in continuous variables were tested using the Mann–Whitney or Wilcoxon test; differences in categoric variables were evaluated using Fisher's exact test, respectively. Kaplan–Meier curves were used to compare survival and cardiac event-free survival of individual patient groups [16]. The differences in survival were assessed by the Mantel–Cox test. A P value <0.05 was considered to be significant.


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 References
 
3.1. Dobutamine and standard echocardiography and patient groups
Seventy-one patients were found to have dysfunctional but viable myocardial segments. Thirty-nine of them underwent coronary revascularization (Group A), 29 were kept on medical therapy (Group B), and three were referred for heart transplantation. Indications for revascularization in group A were mainly angina pectoris, severe CAD (left main disease, triple vessel disease, proximal left anterior descending coronary artery stenosis) or significant viability (four or more dysfunctional segments with viability) in patients with heart failure without angina. Group B patients were kept on medical therapy mainly because of inability to revascularize stenotic vessels. The mean numbers of dysfunctional but viable segments in groups A and B were 3.8±1.7 and 3.7±2.3, respectively. Fifty-three patients were identified to have dysfunctional non-viable myocardium. Twenty-three of them were revascularized (Group C), 22 remained on medical therapy (Group D) and eight were referred for heart transplantation. The reason for revascularization of group C patients was angina pectoris and the presence of significant CAD involving vessels supplying normokinetic myocardial segments. Eleven patients referred directly for heart transplantation were in heart failure functional class III–IV and had no or minimal angina and viability of dysfunctional myocardial segments. To create the group of transplanted patients (Group E), we included another 62 patients with CAD, transplanted in our institution within the time interval from 1994 to 2000. In these 62 patients, dobutamine echocardiography was not performed because there was no possibility of revascularizing coronary arteries (no bypassable arteries, severe heart failure). LV EFs assessed by echocardiography are shown in Table 1. In revascularized patients with viability (Group A), EF significantly increased from 27±3% to 34±4% (P<0.01) after revascularization, whereas there was no significant change in EF from 27±3% to 28±5% (P=NS) in those without viability (Group C). This comparison was performed for 33 group A and 19 group C patients, in whom both pre- and post-revascularization EFs were acquired.


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  		Table 1 Clinical Characteristics

 
3.2. Baseline characteristics of patients in groups A, B, C, D and E
Clinical characteristics, results of coronary angiography and type of revascularization are presented in Tables 1 and 2. Hypercholesterolemia was defined as serum cholesterol >250 mg/dl, obesity as a body mass index ≥30 kg/m2. Groups A, B, C and D were comparable in all variables except for LV EF, which was mildly but significantly lower in group D than in the other groups, for age showing a small but significant difference between group A and B, and for the severity of CAD, which was more pronounced in group A than in group D. Transplanted patients (group E) differed from the other groups in more parameters. They were younger, suffered less from angina pectoris and hypertension, exhibited lower LV EF, and all had symptomatic heart failure. These differences reflect the selection bias, as younger patients (below 60 years) with dyspnea and the very severe heart failure constituted the majority of patients referred for heart transplantation. However, because group E patients were followed up from the day of transplantation, the different pre-transplant characteristics were unlikely to significantly affect the survival analysis. The symptoms of angina pectoris disappeared in 39 out of 47 symptomatic patients (83%) after revascularization. Table 3 shows medication of patients after coronary revascularization and for those on medical therapy. Two group A and three group C patients who died during or early after bypass surgery are not included. Group D patients were more often on diuretic therapy than group A patients, while group C patients were taking beta blockers more frequently compared with group B patients. Otherwise there were no differences among the groups.


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  		Table 2 Angiographic and coronary revascularization characteristics

 


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  		Table 3 Medication of patients after coronary revascularization and those on medical therapy

 
3.3. Follow-up results
Cardiac events in revascularized and medically treated patients are presented in Table 4. Only one event was considered in each patient in the following succession: death; non-fatal myocardial infarction; hospitalization for heart failure; and hospitalization for unstable angina pectoris. There was a significant increase in cardiac-related deaths in groups B and D as compared with group A. In groups A, B, C and D, all deaths were of cardiac origin except for one group D patient who died after a serious car accident (not included in the table). In revascularized patients (groups A and C), there were six early events (within 30 days after bypass surgery). One group A patient suffered non-fatal perioperative myocardial infarction, two group A and three group C patients died on days 1, 3 and 7, 27, 28, respectively, after operation. In the case of the five late deaths, the reasons were progressive heart failure in one group A and two group C patients, sudden death in one group A patient, and acute myocardial infarction in one group C patient. Of the medically treated patients who died, eight patients died suddenly (five group B and three group D patients), six died of progressive heart failure (three patients in both groups), and three (two group B and one group D) of acute myocardial infarction. During the follow-up, three patients initially referred for medical therapy underwent heart transplantation because of progression of heart failure symptomatology, and one patient underwent revascularization after an episode of unstable angina pectoris. All these patients were considered as medically treated and censored at the time of procedure. There were 17 deaths in the group of transplanted patients (group E). The causes of deaths were allograft rejection (seven patients), pulmonary embolism (two patients), lymphoma (two patients), sudden death of unrecognized origin (two patients), pneumonia (two patients), stroke (one patient) and cardiac tamponade (one patient). Fig. 1 demonstrates survival free of cardiac events in groups A, B, C and D. There were no significant differences among groups. Fig. 2 shows survival analysis in groups A, B, C, D and E. At the end of the study, the survival of group A patients was significantly better than that in group B (P<0.05). There were survival differences among groups related to the duration of follow-up. While there was a comparable survival of groups A, B, C, D and E at 1 year (89, 74, 82, 84 and 86%, respectively), the 3- and 5-year survival was significantly better for group A compared with group B (both P<0.05) and this benefit continued until the end of the study. At 3 years, there was significantly better survival of transplanted patients (group E) than that in patients with viability kept on medical therapy (group B, P<0.05). However, the survival benefit of transplantation was only temporary and was present neither at 5 years nor at the end of the study. The 3-year survival in groups A, B, C, D and E was 89, 60, 67, 60 and 81%, respectively. The corresponding values at 5 years were 89, 60, 67, 50 and 78%, respectively.


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  		Table 4 Cardiac events in groups A, B, C and D

 


Figure 1
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  		Fig. 1 Kaplan–Meier estimates of cardiac event-free survival for groups A, B, C and D. There were no significant differences among the groups.

 


Figure 2
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  		Fig. 2 Kaplan–Meier estimates of survival for groups A, B, C, D and E. The survival was significantly better in group A than in group B (P<0.05).

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
References
 
The main finding of our study was the evidence of a significantly better survival in patients with dysfunctional but viable myocardium who underwent coronary revascularization than in those who remained on medical therapy. This fact underscores the utility of the assessment of myocardial viability in patients with CAD and severe LV dysfunction for the identification of optimal therapeutic approach. In addition, we demonstrated the importance of a long-time period for an objective assessment of the various treatment strategies.

4.1. Treatment of patients with chronic CAD and severe LV dysfunction
The decision on the optimal treatment of patients with severely depressed LV function is often difficult. No randomized or large-scale trials in patients with heart failure and a defined amount of myocardial viability comparing medical therapy, revascularization, or heart transplantation have been published. Despite marked progress in operative techniques and subsequent postoperative care, the hospital or early (within 30 days after bypass surgery) mortality in patients with LV EF <30% is not negligible ranging between 3.8 and 9.8% [17–20]. Operative mortality rises further with evidence of symptomatic heart failure, up to 14.3% [21]. However, despite this fact, the long-term prognosis of revascularized patients with severe LV dysfunction has been repeatedly found to be better than that in patients with comparable LV dysfunction treated only medically [18,22,23]. The more severe the LV dysfunction, the greater the benefit of revascularization compared to medical therapy [22,23]. However, comparative studies of medical therapy and coronary revascularization, in the current era of use of angiotensin-converting enzyme inhibitors, statins and beta blockers in patients with CAD and severely depressed LV function, are missing. Another alternative for heart failure patients is heart transplantation with 1-year survival of 79% [24]. The problem is that heart transplantation can only be offered to a limited number of heart failure patients because of shortage of donor hearts and patient mortality on the ‘waiting list’ is high [25]. Several investigators have recently demonstrated that potential candidates for heart transplantation who have hibernating myocardium can be successfully revascularized [26,27] and their long-term prognosis corresponds to that in transplanted patients [27]. The hibernating myocardium represents a substrate with a large potential of functional recovery after revascularization. If the area of viability is large, revascularization results in a significant improvement in LV EF [1,2,28], patient functional NYHA class [1,2] as well as prognosis [1,2,28–30]. In our study, there were no significant survival differences between transplanted and revascularized patients. However, when evaluating prognosis of transplanted patients, we did not take into account their period on the ‘waiting list’ for transplantation which often lasts more than 1 year and is accompanied by a high mortality. Thus the actual rate of events in patients referred for heart transplantation is probably higher than that demonstrated in Fig. 2, in which the patient follow-up started on the day of transplantation. However, a definitive answer to the role of revascularization and transplantation requires larger studies.

4.2. Prognostic importance of myocardial viability
Current data in patients with CAD and LV dysfunction concordantly show a high cardiac event rate in medically treated patients with dysfunctional but viable myocardium [5,8,9,30–36]. In such patients myocardial revascularization significantly decreases mortality or the rate of non-fatal cardiac events [6,8,9,30–36]. The results of our study support this fact. Iskander and Iskandrian [37] summarized the results of 12 studies published up to 1997 including 1029 patients with CAD and LV dysfunction in whom the viability assessment was performed. The authors found a 27% annual event rate in patients with viable myocardium treated medically. The corresponding annual event rates were 6% in patients with viable myocardium who underwent coronary revascularization, and 7 and 5%, respectively, in those without viability treated medically or revascularized. However, in a significant proportion of included studies, the annual event rate was not available for all patient groups, and a mean LV EF of 33% suggests not negligible involvement of patients with only moderate LV dysfunction. Recently, Afridi et al. [30] demonstrated in 318 patients with CAD and LV EF ≤35% mortality rates of the corresponding patient groups to be 20, 6, 20 and 17%. Similarly higher mortality rates or rates of non-fatal cardiac events in patients without viability have recently been demonstrated by Senior et al. [1] and Pasquet et al. [6], and now described in our study. Thus, while there is agreement on a relatively favorable prognosis for revascularized patients with viability and adverse prognosis in those with viability who remain on medical therapy, conflicting data exist on the prognosis of patients without viability and on the effect of revascularization in such patients. The different results can probably be explained by different study populations. Studies with a higher rate of cardiac events in patients without viability, irrespective of the mode of treatment, probably included more seriously sick patients, the inclusion LV EF was ≤35% in Afridi's [30] and Senior's [1] study, and ≤30% in our study, and many patients in these studies exhibited symptomatic heart failure. Our study, however, highlighted another important point in comparing various therapeutic strategies—the time of follow-up. Paradoxically, the best survival within the first 10 months of follow-up was achieved in patients without viability kept on medical therapy, although their 5-year survival was the worst (Fig. 2). On the contrary, revascularized patients with viability exhibited a higher rate of early events due to a relatively high operative and early postoperative mortality, the significant prognostic benefit of revascularization occurred late. As demonstrated in Fig. 2, a minimum of 3-year follow-up is necessary to prove the prognostic benefit of coronary revascularization. However, in view of the relative increase in the frequency of late deaths in transplanted patients, accounting for the only temporary prognostic benefit of heart transplantation, probably an even longer follow-up interval should be achieved to compare various therapeutic strategies. Of the studies published so far, dealing with the problems of viability, treatment and survival of patients with severely depressed LV function, only a minimum fulfilled this important supposition. The improved survival in revascularized patients with viability in our study probably resulted from the removal of myocardial ischemia and mainly from the improvement in LV systolic function due to the revascularization of the hibernating myocardium, as demonstrated by an increase in LV EF from 27 to 34%. The survival of revascularized patients without viability tended to be somewhat better than that of medically treated patients, but the difference was not significant. The results in such patients probably depends on the proportion of patients with stress-induced ischemia in whom revascularization may offer prognostic benefit by removing myocardial ischemia, even if there is no recovery of the resting LV systolic function after revascularization [38]. The prognostic benefit may be expected even in patients without viability or ischemia if they have extensive (triple-vessel or left main) CAD [6]. In our study 83% of group C patients had either exertional angina pectoris or triple vessel or left main CAD. However, a definitive answer to the prognostic benefit of revascularization in patients without viability in dysfunctional myocardium requires evaluation in larger patient populations.

4.3. Study limitations
There are several limitations of our study. First, it is not a randomized study. The decision on treatment was in some patients influenced by the result of dobutamine echocardiography. However, in view of current knowledge of the marked prognostic benefit of revascularization in patients with a large amount of hibernating myocardium, the randomization of such patients to medical treatment is, in our opinion, unethical. In transplanted patients, the evaluation of the prognostic impact of myocardial viability is impossible, and these patients were included in this study only to demonstrate survival of patients with severe ischemic cardiomyopathy referred for heart transplantation. Second, because of the application of only low doses of dobutamine, we do not have information on the presence of stress-induced ischemia, which is known to be an important prognostic factor [5–7]. In addition, the application of both low and high doses of dobutamine enables more precise identification of myocardial viability [39]. Finally, in revascularized patients, repeated coronary angiography after revascularization was not performed to verify the patency of grafts or dilated arteries. However, removal of angina pectoris in 83% of the patients suggests a good effect of revascularization.


   Acknowledgements
 
This work was supported in part by grants from the Ministry of Health of the Czech Republic (IGA, No. 5874-3) and of the Ministry of Education of the Czech Republic (MSM, No. 141100004).


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

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 Eur J Heart FailHome page
M. Bountioukos, A. F.L. Schinkel, D. Poldermans, V. Rizzello, E. C. Vourvouri, B. J. Krenning, E. Biagini, J. R.T.C. Roelandt, and J. J. Bax
QT dispersion correlates to myocardial viability assessed by dobutamine stress echocardiography in patients with severely depressed left ventricular function due to coronary artery disease
Eur J Heart Fail, March 1, 2004; 6(2): 187 - 193.
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