Influence of left ventricular function on signal averaged late potentials in patients with coronary artery disease with and without ventricular tachycardia

Left ventricular dysfunction has been suggested as a cause of late potentials on the signal averaged ECG of patients with coronary artery disease. We compared the averaged surface ECG with angiographic findings in 57 patients with coronary artery disease and left ventricular dysfunction. Sixteen patients had sustained ventricular tachycardia and 41 had no documented arrhythmia. These two patient groups were comparable with respect to age, mean ejection fraction, and wall motion score. Late potentials, defined as voltage less than 25 microV in the last 40 msec of the filtered QRS complex, were found in 10 of 16 patients with ventricular tachycardia and in 6 of 41 patients without arrhythmia (p less than 0.005). However, late potentials were independent of ejection fraction, wall motion score, or presence of dyskinesis in both groups. There was no correlation between the total filtered QRS duration and ejection fraction or wall motion score in either patient group. In patients with coronary artery disease, late potentials are associated with ventricular tachycardia but are independent of global or regional left ventricular function. This finding has important implications for studies of the prognostic value of late potentials following myocardial infarction.     

Late arrhythmic events and patency of the infarct-related coronary artery in survivors of acute myocardial infarction.

In the present study we evaluated the influence of intravenous thrombolysis and patency of the infarct-related coronary artery on both markers of ventricular electrical instability and incidence of late arrhythmic events after acute myocardial infarction (AMI). Ninety one patients surviving a first AMI who consecutively performed coronary angiography were enrolled in the present study; 44 patients (48%) received thrombolysis, 47 patients (52%) were treated conventionally. Of 91 patients, 90 (99%) had signal-averaged electrocardiogram (SAECG), and 40 (44%) programmed ventricular stimulation. No significant difference was observed between thrombolytic-treated and control group in late potential rate, SAECG determinants and ventricular arrhythmia inducibility. Of 91 patients, 40 (44%) had occlusion of the infarct-related artery: of these, 15 (37%) had late potentials compared with 5 of 51 patients (9%) with a patent artery (p < 0.01). Mean left ventricular ejection fraction was not significantly different between the two groups (0.50 +/- 0.15 vs 0.55 +/- 0.12; p = NS). No significant difference was present between the two groups of patients with regard to inducibility of sustained ventricular tachyarrhythmias, however an odds ratio of 3.5 was observed in the group with a closed vessel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between late potentials and myocardial viability assessed by dobutamine echocardiography in the early postinfarction period

BACKGROUND: In the postmyocardial infarction period, late potentials (LPs) are a sensitive marker for the occurrence of sustained ventricular tachycardia and ventricular fibrillation. The relationship between positive signal-averaged electrocardiogram (SAECG) and myocardial viability remains controversial. The aim of the present study was to assess prospectively the possible relationship between LPs and myocardial viability detected by dobutamine stress echocardiography (DSE) in the early period after myocardial infarction (AMI), before hospital discharge. DESIGN: Ninety-nine patients with AMI were included prospectively in the study. The mean age was 58 +/- 11 years, 17 were women and 82 were men. All patients had SAEG and DSE, and 94 had coronary angiography before hospital discharge. RESULTS: In the overall population, presence of viability was demonstrated in fewer patients with LPs [37 of 70 (52%)] than absence of viability [18 of 29 (62%)] but the difference did not reach statistical significance. In the subgroup of patients with left ventricular ejection fraction (LVEF) lower than 40%, at higher risk of arrhythmias, the presence of viability was associated with the absence of LPs: 80% of the patients without LPs had viability by DSE (P < 0.01) and only 35% of patients with LPs had viability by DSE (not significant). CONCLUSIONS: In patients with an acute myocardial infarction and with low ejection fraction (<40%), the absence of LPs is related to the presence of viable myocardium as assessed by DSE early after the acute event. These data also suggest that myocardial viability is not the substrate for LPs in this population.     

Relationship between myocardial viability and ventricular late potentials in patients with history of myocardial infarction

AIM. To study relationship between presence and volume of viable myocardium and registration of late ventricular potentials in patients with history of myocardial infarction. MATERIAL AND METHODS. High resolution ECG, dobutamine stress echocardiography and Holter ECG monitoring were carried out 34 patients (mean age 54.1-/+3.1 years) with history of documented myocardial infarction. RESULTS. According to data of dobutamine stress echo patients were divided into 2 groups: with irreversible myocardial dysfunction (n=16, group 1) and with hibernating myocardium (n=18, group 2). Ventricular late potentials were registered in 3 (18.7%) and 11 (61,1%) patients in groups 1 and 2, respectively. Group 2 patients more often had high-grade ventricular arrhythmias. There was no association between presence of ventricular late potentials and Lown grade of ventricular arrhythmias on Holter ECG. Duration of filtered QRS (QRSt) complex correlated directly with index of regional wall motion abnormality, end-diastolic volume, and negatively - with total ejection fraction. CONCLUSION. Among myocardial infarction survivors patients in whom dobutamine stress echo detects viable myocardium significantly more often have ventricular late potentials and high grade ventricular arrhythmias compared with patients with myocardial scars without viable myocardium.     

High-resolution ECG in assessment of myocardial functional state in patients with ischemic heart disease and resultant cardiac dilatation

High resolution signal-averaged ECG (SAECG), echocardiography and 24-hour Holter ECG monitoring were used in the study of 30 patients (mean age 56-/+2 years) with coronary heart disease and stable class II-IV angina (group 1) and 66 patients (mean age 45-/+1 years) with dilated cardiomyopathy of ischemic origin (group II). SAECG was used for detection of late ventricular potentials and calculation of time-voltage and velocity parameters of P-waves. Disturbances of myocardial de- and repolarization indicative of pronounced hemodynamic left atrial overload associated with elevated left ventricular end diastolic pressure were revealed. These disturbances were more pronounced in patients of group II. Late ventricular potentials and arrhythmias were more frequent in patients with more severe cardiac failure. Sensitivity of SAECG for detection of arrhythmogenic substrate in the myocardium was 70 and 90% in groups I and II, respectively. Positive predictive power of ventricular late potentials for occurrence of ventricular arrhythmias in these groups was 86 and 91%, respectively.     

血运重建对冠心病合并心功能不全患者心肌收缩功能和心室重构的影响

目的探讨血运重建对冠心病合并左心功能不全患者心肌收缩功能和心室重构的影响。方法86例冠心病合并心功能不全患者术前应用超声心动图进行心功能、左心室(左室)几何形态和心肌活性评定,分为有存活心肌组和无存活心肌组,两组分别行血运重建或药物治疗。随访(13±5)个月后重新评价上述指标。结果57例有存活心肌的患者中行血运重建者较药物治疗者左室射血分数(LVEF)、存活节段数、左室球状指数(LVSI)明显提高;左室舒张末容积(LVEDV)、左室收缩末容积(LVESV)、左室重量(LVM)明显降低(P值均<0.01)。29例无存活心肌的患者中上述指标两种治疗间无显著性差异(P值均>0.05)。结论血运重建能改善冠心病合并左心功能不全但有存活心肌患者的心肌收缩功能和几何形态。     

Low-dose dobutamine radionuclide ventriculography for prediction of myocardial viability: quantitative analysis of regional left ventricular function

BACKGROUND: It is important to distinguish viable myocardium from necrotic tissue in order to decide upon therapy in patients with ischemic heart disease. HYPOTHESIS: We verified the hypothesis that quantitative analysis of regional left ventricular function using low-dose dobutamine radionuclide ventriculography (RNV) can sensitively predict myocardial viability and compared its usefulness with thallium-201 (201Tl) single-photon emission computed tomography (201Tl-SPECT). METHODS: Radionuclide ventriculography at rest and during low-dose dobutamine infusion (5 micrograms/kg/min), 201Tl-SPECT, and coronary angiography were performed in 51 subjects with severe ischemia-related stenosis of coronary arteries and 3 subjects without coronary artery disease. 201Tl uptake was assessed as normal (control), low perfusion (LP), or defect. We compared the response of regional function to dobutamine with the regional 201Tl uptake. The accuracy of both methods for identifying viable myocardium was investigated in 17 patients who underwent successful coronary revascularization, with a resulting improvement in wall motion. RESULTS: The increase in regional ejection fraction (delta r-EF) in response to dobutamine was significantly greater in the control (12 +/- 6%) and LP (16 +/- 11%) regions than in the defect (5 +/- 10%) regions. The increase in one-third regional ejection fraction (delta r-1/3EF) was also significantly higher in the control (14 +/- 7%) and LP (10 +/- 8%) regions than in the defect regions (5 +/- 6%). We defined myocardial viability as a delta r-EF > 5% or a delta r-1/3EF > 2%. The sensitivity and specificity of the delta r-EF for identification of myocardial viability were 91.4 and 55.5%, respectively. The sensitivity and specificity of the delta r-1/3EF were 91.4 and 66.6%, respectively; the corresponding values for 201Tl SPECT were 74.2 and 77.8%. CONCLUSION: Low-dose dobutamine RNV with quantitative analysis of regional left ventricular function was more sensitive for identification of viable myocardium than 201Tl-SPECT.     

冠状动脉旁路术前存活心肌的评价(附13例报告)

目的对１３例准备行冠状动脉旁路术（ＣＡＢＧ）的冠心病患者术前行硝酸异山梨酯（ＩＳＤＮ）介入２０１ＴＩ心肌断层显像，评价其检测存活心肌及预测心功能恢复的价值。方法ＣＡＢＧ术前患者于多巴酚丁胺负荷高峰时注射２０１ＴＩ行负荷、３小时再分布心肌显像后，静脉点滴ＩＳＤＮ并再次注射２０１ＴＩ（ＩＳＤＮ／ＲＩ）进行心肌显像，ＣＡＢＧ术后３个月复查静态心肌显像，并比较术前后左室射血分数。结果１３例患者负荷像共有４８个节段灌注异常，ＩＳＤＮ／ＲＩ显像后有２９个节段灌注改善，其中２６个节段在术后心肌灌注亦有改善；不可逆灌注或异常加重的１９节段中，术后仍有１７个节段灌注无改善，ＩＳＤＮ／ＲＩ显像检测存活心肌的准确性为８９．５％。且左室射血分数的提高与ＩＳＤＮ／ＲＩ显像可逆灌注节段数密切相关（ｒ＝０．７３，Ｐ＜０．００５）。结论ＩＳＤＮ／ＲＩ２０１ＴＩ心肌显像在估测存活心肌和预测心功能恢复方面有较高的临床实用价值。     

Prognostic significance of the signal averaged electrocardiogram in patients with chronic stable coronary artery disease. Analysis in the time domain and by spectral temporal mapping

BACKGROUND: Ventricular late potentials detected by the signal averaged electrocardiogram (SAECG) have been used to predict cardiac death in patients after recent myocardial infarction. The goal of this study was to investigate the prognostic significance of the SAECG in a population of chronic coronary artery disease, with and without previous myocardial infarction. METHODS: SAECG was recorded in 698 patients with angiographically proven coronary artery disease and analyzed by time domain analysis (TDA) and by spectral temporal mapping (STM). Cardiac death or ventricular fibrillation (= cardiac event) were used as the primary endpoint for follow-up (25 to 33 months). RESULTS: A cardiac event occurred in 46 out of 698 patients (6.6%). An abnormal SAECG using TDA was found in 43% of patients with a cardiac event, as compared to 21.7% in those without (p<0.0005). The probability of a cardiac event during follow-up was 4.4% when TDA and STM were both normal, 9.5% and 10.2% when either STM or TDA were abnormal and 28.5% when both were abnormal. A duration of the averaged QRS complex of more than 120 ms and a left ventricular ejection fraction of less than 45% were the only independent predictors of a cardiac event. Logistic regression analysis could predict a cardiac event with a sensitivity of 54% and a specificity of 88%. CONCLUSIONS: In patients with chronic coronary artery disease the duration of the signal averaged QRS complex and left ventricular ejection fraction are independent predictors of cardiac death or ventricular fibrillation.     

The prognostic value of myocardial viability recognized by low dose dipyridamole echocardiography in patients with chronic ischaemic left ventricular dysfunction.

AIMS: The aim of this study was to assess the prognostic value of myocardial viability recognized as a contractile response to vasodilator stimulation in patients with left ventricular dysfunction in a large scale, prospective, multicentre, observational study. METHODS AND RESULTS: Three hundred and seven patients (mean age 60 +/- 10 years) with angiographically proven coronary artery disease, previous (>3 months) myocardial infarction and severe left ventricular dysfunction (ejection fraction <35%; mean ejection fraction: 28 +/- 7%) were enrolled in the study. Each patient underwent low dose dipyridamole echo (0.28 mg x kg(-1) in 4 min). Myocardial viability was identified as an improvement of >0.20 in the wall motion score index. By selection, all patients were followed up for a median of 36 months. One-hundred and twenty-four were revascularized either by coronary artery bypass grafting (n=83) or coronary angioplasty (n=41). The only end-point analysed was cardiac death. In the revascularized group, cardiac death occurred in one of the 41 patients with and in 16 of the 83 patients without a viable myocardium (2.4% vs 19.3%, P<0.01). Outcome, as estimated by Kaplan-Meier survival, was better for patients with, compared to patients without, a viable myocardium, who underwent coronary revascularization (97.6 vs 77.4%, P=0.01). Using a Cox proportional hazards model, the presence of myocardial viability was shown to exert a protective effect on survival (chi-square 4.6, hazard ratio 0.1, 95% CI 0.01-0.8, P<0.03). The survival rate in medically treated patients was lower than in revascularized patients irrespective of the presence of a viable myocardium (79.7% vs 86.2, P=ns). CONCLUSION: In severe left ventricular ischaemic dysfunction, myocardial viability, as assessed by low dose dipyridamole echo, is associated with improved survival in revascularized patients.     

Short-term effect of coronary artery bypass grafting on the signal-averaged electrocardiogram

Ventricular late potentials at the end of the QRS can be detected on the body surface during sinus rhythm by recording a signal-averaged electrocardiogram (SAECG). In patients with coronary artery disease, these late potentials have been shown to be markers for spontaneous or inducible ventricular tachycardia, or both. The short-term (before and 10 +/- 4 days after coronary revascularization) influence of coronary artery bypass grafting (CABG) on the quantitative SAECG variables was studied in 40 patients with chronic coronary artery disease. Twenty-five of these patients had a previous myocardial infarction. In the 15 patients without previous myocardial infarction, no abnormal SAECG indexes were recorded before CABG and no change in the quantitative SAECG variables was observed after surgery. In the patients with a previous myocardial infarction, 7 (28%) had a late potential before CABG. After CABG, 5 (71%) patients remained late potential-positive, whereas the other 2 (29%) lost their late potential. The mean values of their SAECG variables improved after coronary revascularization. In the entire group of postmyocardial infarction patients, the high-frequency QRS duration had shortened (p less than 0.01) after CABG (the other SAECG indexes did not change). The postoperative arrhythmic complications (transient atrial fibrillation, new onset of ventricular couplets) tended to be more frequent in the postmyocardial infarction group and in patients with late potentials. Our findings suggest that the reported increase in ventricular arrhythmias after CABG is probably not related to a change in the arrhythmogenic substrate for ventricular reentry but is associated with changes in the arrhythmogenic milieu.     

Benefits of coronary revascularisation in diabetic and non-diabetic patients with ischaemic cardiomyopathy: role of myocardial viability

BACKGROUND: Diabetes mellitus in patients with coronary artery disease is associated with poor outcome. In this study, the relation between myocardial viability, diabetes, coronary revascularisation and outcome was evaluated. METHODS: 129 patients (31 diabetic, 98 non-diabetic) with ischaemic cardiomyopathy underwent dobutamine stress echocardiography to assess myocardial viability. Patients with >or=4 viable segments were defined as viable and patients with <4 viable segments as nonviable. Left ventricular ejection fraction (LVEF) was assessed before and 9-12 months post-revascularisation. At the same time-points, LV volumes were measured to evaluate LV remodelling. Finally, cardiac events were noted during 5-year follow-up. RESULTS: The extent of viable myocardium was comparable between diabetic and non-diabetic patients. After revascularisation, LVEF increased >or=5% in 44% of diabetic and in 40% of non-diabetic patients. LVEF only improved in patients with viable myocardium. Ongoing LV remodelling occurred in 36% and 35% of diabetic and non-diabetic patients respectively, and was related to non-viability, whereas viability protected against ongoing LV remodelling, both in diabetic and non-diabetic patients. Viability was the only predictor of survival after revascularisation. CONCLUSIONS: Diabetic, viable patients with ischaemic LV dysfunction exhibit improvement in LVEF post-revascularisation with prevention of ongoing LV remodelling, similar to non-diabetic patients. Myocardial viability was also the only predictor of long-term outcome.     

Rest-redistribution 201-Tl single-photon emission CT imaging for determination of myocardial viability: relationship among viability, mode of therapy, and long-term prognosis.

BACKGROUND: The diagnosis of viable myocardium in the setting of ischemic left ventricular systolic dysfunction might indicate which patients have the greatest prognostic benefit from myocardial revascularization. Single-photon emission CT (SPECT) thallium-201 (201Tl) scintigraphy for the detection of viable myocardium is widely available in the community, but outcome data using this imaging modality are limited. METHODS: Thirty-seven patients (mean [+/- SD] age, 62+/-12 years) with ischemic left ventricular dysfunction (mean ejection fraction, 30+/-9%) initially referred for rest-redistribution SPECT thallium scintigraphy were evaluated 29+/-19 months after coronary bypass surgery (n = 15) or medical therapy alone (n = 22). The relationship among myocardial viability, mode of therapy, and long-term prognosis was evaluated. RESULTS: Significant myocardial viability (defined as a viability index [VI] of > 0.5) was present in 19 patients. Among patients with a VI > 0.5, the 48-month actuarial event-free survival was 89+/-10% for patients undergoing surgical revascularization, compared with 0% for the medical treatment subgroup (p = 0.005). In contrast, patients in the low-viability subgroup tended to have intermediate event-free survival rates, which were not statistically different for patients receiving either surgical (62+/-21%) or medical therapy (50+/-14%; p = 0.55). CONCLUSIONS: Survival is significantly more favorable for surgically revascularized patients with ischemic left ventricular dysfunction and myocardial viability as detected by SPECT 201Tl scintigraphy.     

Left Ventricular Remodeling after Late Revascularization Correlates with Baseline Viability

The ideal management of stable patients who present late after acute ST-elevation myocardial infarction (STEMI) is still a matter of conjecture. We hypothesized that the extent of improvement in left ventricular function after successful revascularization in this subset was related to the magnitude of viability in the infarct-related artery territory. However, few studies correlate the improvement of left ventricular function with the magnitude of residual viability in patients who undergo percutaneous coronary intervention in this setting.In 68 patients who presented later than 24 hours after a confirmed first STEMI, we performed resting, nitroglycerin-enhanced, technetium-99m sestamibi single-photon emission computed tomography–myocardial perfusion imaging (SPECT–MPI) before percutaneous coronary intervention, and again 6 months afterwards. Patients whose baseline viable myocardium in the infarct-related artery territory was more than 50%, 20% to 50%, and less than 20% were divided into Groups 1, 2, and 3 (mildly, moderately, and severely reduced viability, respectively). At follow-up, there was significant improvement in end-diastolic volume, end-systolic volume, and left ventricular ejection fraction in Groups 1 and 2, but not in Group 3.We conclude that even late revascularization of the infarct-related artery yields significant improvement in left ventricular remodeling. In patients with more than 20% viable myocardium in the infarct-related artery territory, the extent of improvement in left ventricular function depends upon the amount of viable myocardium present. The SPECT–MPI can be used as a guide for choosing patients for revascularization.     

The noninvasive assessment of myocardial viability

The major objective of noninvasive imaging for detection of myocardial viability is to assist in the improved selection of patients with coronary artery disease and severe left ventricular dysfunction who would benefit most from revascularization. The techniques most commonly used to identify viable myocardium are thallium-201 (TI) scintigraphy, positron emission tomography (PET) using a flow tracer in combination with a metabolic tracer, technetium-99m (Tc) sestamibi imaging, and dobutamine echocardiography. On stress TI scintigraphy, asynergic regions showing normal thallium uptake, an initial defect with delayed redistribution at 3–4 h, late redistribution at 24 h, or defect reversibility after reinjection of a second dose of TI at rest all suggest preserved viability. The greater the final uptake of TI in areas of regional myocardial dysfunction preoperatively, the greater the improvement in ejection fraction after coronary revascularization. Demonstration of uptake of fluoro-18 deoxyglucose (FDG) in regions of diminished blood flow on PET imaging also correlates well with improved systolic function after revascularization. Tc sestamibi may also be useful for assessment of myocardial viability, particularly after thrombolytic therapy for acute myocardial infarction. Dobutamine echocardiography has good positive predictive value for viability determination, but absence of systolic thickening in an akinetic zone in response to intravenous infusion of the drug may still be associated with viable myocardium in 25–50% of segments. Of all the techniques cited above, quantitative resting TI scintigraphy may be the best approach for distinguishing between viable and irreversibly injured myocardium.     

Does the abnormal signal-averaged electrocardiogram predict future appropriate therapy in patients with implantable cardioverter-defibrillators?

BACKGROUND: Several studies have documented the prognostic significance of the signal-averaged electrocardiogram (SAECG) both after myocardial infarction and nonischemic cardiomyopathy. However, whether the SAECG can identify patients with implantable cardioverter-defibrillator (ICD) who receive appropriate therapy has not been hitherto completely investigated. METHODS: Between August 2002 and August 2004, 83 consecutive ICD patients who had had SAECGs recorded were enrolled in this study. All patients were followed up in the outpatient ICD clinic, and interrogated electrograms were collected. RESULTS: Over 9.0 +/- 2.8 months of follow-up, 27 (32%) patients had appropriate ICD therapy for ventricular tachycardia or fibrillation; 15 (55.6%) patients had abnormal; and the remaining 12 (44.4%) had normal SAECGs. Of the 56 patients with no appropriate therapy, 27 (48.2%) and 29 (51.8%) patients had abnormal and normal SAECGs, respectively. There were no statistically significant differences between the 2 groups in SAECG findings (P = .41). A Cox regression analysis showed that the left ventricular ejection fraction was the only predictor of appropriate therapy (P = .02). Subgroup analysis of the patients with coronary artery disease and spontaneous monomorphic ventricular tachycardia indicated that left ventricular ejection fraction (P = .03) and abnormal SAECG (P = .02) were predictors of appropriate therapy. CONCLUSIONS: Our data demonstrate that except for the subgroup of patients with coronary artery disease presenting with monomorphic ventricular tachycardia, the SAECG did not predict ventricular tachyarrhythmia recurrence and, hence, appropriate ICD therapy. Thus, SAECG findings should generally not be a factor in decision for ICD implantation.     

Influence of residual myocardial ischaemia on induced ventricular arrhythmias following a first acute myocardial infarction.

OBJECTIVES: The purpose of this study was to assess the possible effect of residual myocardial ischaemia on induced ventricular arrhythmia during programmed ventricular stimulation in survivors of a first acute myocardial infarction. BACKGROUND: Most deaths after hospital discharge for acute myocardial infarction are sudden and presumably arrhythmic. Sudden cardiac death results from a dynamic interaction of structural abnormalities and transient triggering factors. The role of myocardial ischaemia as a trigger for ventricular arrhythmias remains unclear. We hypothesized that residual myocardial ischaemia after a first acute myocardial infarction is a potent trigger for sustained ventricular tachyarrhythmias, particularly in the presence of an abnormal myocardium. METHODS AND RESULTS: In this prospective study, programmed electrical stimulation, coronary angiography and dipyridamole-thallium-201 scintigraphy single-photon emission computed tomography were performed in 90 consecutive survivors of a first acute myocardial infarction. Patients, divided in two groups - group 1 with induced ventricular tachyarrhythmia (n=24) and group 2 without induced ventricular tachyarrhythmia (n=66) - were compared regarding residual myocardial ischaemia. The two groups were comparable in terms of mean left ventricular ejection fraction, infarct size and location, gender ratio, peak creatine kinase value, and extent of coronary disease. Residual myocardial ischaemia was detected in 32 patients: 15 (42.5%) belonged to group 1 and 17 (25.7%) to group 2. There was a statistically significant difference between the two groups regarding the presence and the extent of residual myocardial ischaemia (P<0.05). CONCLUSION: Residual myocardial ischaemia, revealed by dipyridamole-thallium-201 scintigraphy following a first acute myocardial infarction, might contribute to electrical instability evaluated by programmed ventricular stimulation.     

Dobutamine stress-redisstribution-reinjection versus rest-redistribution thallium-201 spect in the assessment of myocardial viability

The aim of this study was to evaluate the value of thallium-201 chloride (²⁰¹Tl) reinjection imaging following dobutamine stress (DRi) to identify viable myocardium in comparison with a rest-redistribution ²⁰¹Tl protocol (RR). The identification of viable myocardium bears important consequences for adequate selection of patients with poor left ventricular function, often unable to exercise, who are considered for revascularization. Twenty-six patients with chronic coronary artery disease and depressed left ventricular function (ejection fraction 36±10%) were studied by both DRi and RR single photon emission computed tomography (SPECT). Semi-quantitative analysis of regional ²⁰¹Tl activity (5-point score) and wall motion by echocardiography using a 16-segment model was performed. Regions were classified as viable (normal/reversible/fixed moderate defects) or non-viable (fixed severe defects) and related to regional wall motion. Target heart rate was reached in 25 patients. Myocardial viability was demonstrated in 353/416 (85%) by DRi SPECT and in 346/416 (83%) by RR SPECT. The agreement between the 2 protocols was 98% with a K-value of 0.94; similar results were obtained when the analysis was limited to dyscontractile segments. In conclusion, this study demonstrates the feasibility and diagnostic value of DRi SPECT to identify viable myocardium.     

Myocardial viability in patients with Q wave myocardial infarction and no residual ischemia.

BACKGROUND. Coronary revascularization in patients with persistent angina after myocardial infarction reduces the incidence of recurrent angina pectoris and myocardial infarction and improves left ventricular function. The results of revascularization after a Q wave myocardial infarction when there is no residual ischemia may depend on myocardial viability. METHODS AND RESULTS. To determine whether there was viable myocardium in the infarct area in the absence of clinical and scintigraphic evidence of myocardial ischemia, 15 asymptomatic patients with a Q wave myocardial infarction, no redistribution on stress 201Tl test, and single-vessel disease (greater than 70% stenosis) with persistent anterograde blood flow were randomized to percutaneous transluminal coronary artery angioplasty (PTCA) or conservative medical treatment. After 2 months of follow-up, mean coronary blood flow measured by Doppler catheter in the infarct-related artery was higher in the PTCA treatment group (33 +/- 6 ml/min, n = 8) than in the conservative treatment group (16 +/- 4 ml/min, n = 7; p less than 0.05 between groups). The 201Tl pathological-to-normal ratios measured on postexercise images did not change in patients treated conservatively during the follow-up period (delta = +1.1 +/- 2.2%; NS from baseline) but increased significantly in patients treated by PTCA (delta = +8.5 +/- 2.3%; p less than 0.01 from baseline; p less than 0.05 between groups). Segmental wall motion improved on left ventricular angiography 2 months after PTCA (delta = +11.5 +/- 2.2%; p less than 0.001 from baseline) significantly more than in the conservative treatment group (delta = +4.1 +/- 1.4%; p less than 0.05 between both groups). Improvements of 201Tl ratios and segmental wall motion indexes correlated significantly (r = 0.73, p = 0.002). The mild improvement of global left ventricular ejection fraction measured in the PTCA treatment group did not differ significantly from changes in the conservative treatment group. CONCLUSIONS. Successful angioplasty of the stenotic infarct artery in patients with a Q wave myocardial infarction and no residual ischemia improved coronary flow, 201Tl uptake in the infarct area, and regional wall motion. Therefore, myocardial viability may last several weeks, as long as residual blood flow persists in the infarct-related artery. Optimal assessment of viability by imaging techniques should identify patients who are most likely to benefit from revascularization.     

Incremental value of myocardial viability for prediction of long-term prognosis in surgically revascularized patients with left ventricular dysfunction

OBJECTIVES: We assessed the incremental long-term prognostic value of myocardial viability in surgically revascularized (CABG) patients with left ventricular (LV) dysfunction. BACKGROUND: Clinical factors, medical therapy, the degree of LV dysfunction, and stress-induced ischemia may affect the relative prognostic value of myocardial viability. METHODS: Patients with coronary disease and ventricular dysfunction (mean ejection fraction 33% by echocardiography, 25% by angiography) were studied with dobutamine echocardiography. Follow-up (mean -4.9 years) was obtained in 95 patients (85% triple-vessel disease) who underwent CABG. RESULTS: The use of angiotensin-converting enzyme inhibitors, advanced heart failure, rest, low- and peak-dose wall motion scores were univariate predictors of cardiac death. The extent of contractile reserve and ischemia were not predictive. Low-dose score was the strongest multivariate predictor of death (p < 0.001, hazard ratio 6.7). A biphasic response predicted better survival (p = 0.045, hazard ratio 0.5). Five-year survival was better in those with extensive (low-dose score <2.00) versus intermediate (score 2.00 to 2.49) amounts of viable myocardium (p = 0.019). Patients with the least viability (score > or =2.5) had the worst outcome (p = 0.0001 vs. those with low-dose score <2.00; p = 0.05 vs. those with score 2.00 to 2.49). In stepwise multivariate analysis, low-dose score added incremental prognostic value (p = 0.024) to clinical information and rest score. CONCLUSIONS: Low-dose score, representing the extent of viable myocardium, has incremental prognostic value as a predictor of long-term outcome in CABG patients with LV dysfunction.