Functional and anatomic correlates of markedly abnormal stress tests

Comparison of ischemic response during exercise and dobutamine echocardiography in patients with left main coronary artery disease

OBJECTIVES

This study sought to compare manifestations of myocardial ischemia evoked by exercise and dobutamine echocardiography in patients with left main coronary artery disease.

BACKGROUND

During exercise testing, left ventricular cavity dilation, marked ST segment depression and blood pressure decrease indicate severe coronary artery disease. Whether these signs are comparably evoked by dobutamine echocardiography has not been described.

METHODS

Fifty-four patients who underwent stress echocardiography (36 exercise, 18 dobutamine) and coronary angiography showing > or = 50% left main stenosis were analyzed. Electrocardiographic and blood pressure changes, symptoms, wall motion score indexes and sensitivity for coronary artery disease were compared. In 47 patients, the left ventricular endocardium was traced to quantify volumes and ejection fraction.

RESULTS

Stress-induced regional wall motion abnormalities developed in 91% of patients; this was not different on exercise (89%) or dobutamine echocardiography (94%). Rate-pressure product and wall motion score index, similar at rest, tended to be higher after exercise than after dobutamine stress (p = 0.07 and p = 0.05, respectively). ST segment depression > or = 1 mm was more common with exercise (p = 0.005). Ejection fraction and end-systolic and end-diastolic volume indexes were comparable at rest in both groups. With exercise, ejection fraction decreased in 87% of patients, and end-systolic and end-diastolic volume indexes increased in 80%. In contrast, with dobutamine, decreased ejection fraction and increased volume indexes were infrequent. Ejection fraction was lower ([mean +/- SD] 45 +/- 19% vs. 54 +/- 12%, p = 0.007) and end-diastolic (69 +/- 26 vs. 50 +/- 17 ml/m2, p =0.02) and end-systolic (39 +/- 20 vs. 24 +/- 13 ml/m2, p = 0.02) volume indexes were higher after exercise than after dobutamine stress.

CONCLUSIONS

On the basis of changes in regional wall motion both dobutamine and exercise echocardiography have a comparable high sensitivity in diagnosing myocardial ischemia in left main coronary artery disease. However, conventional signs of severe myocardial ischemia, including left ventricular cavity dilation and marked ST segment depression, occur more often with exercise than with dobutamine echocardiography.

Prognostic value of iodine-123 labelled BMIPP fatty acid analogue imaging in patients with myocardial infarction

This study was undertaken to evaluate the prognostic value of iodine-123 labelled 15-iodophenyl-3-R,S-methyl pentadecanoic acid (BMIPP) imaging in patients with myocardial infarction. BMIPP is an iodinated methyl branched fatty acid analogue which is trapped in the myocardium with little washout, thereby reflecting fatty acid utilization in the myocardium. We previously reported that in patients with myocardial infarction, regions are often observed where reduced BMIPP uptake is seen relative to thallium-201 perfusion at rest. However, the clinical significance of such discordant BMIPP uptake remains unknown. Fifty consecutive patients with chronic myocardial infarction referred for stress thallium scan and coronary arteriography underwent BMIPP imaging at rest. Each patient was in a stable condition at the time of the radionuclide study. Follow-up was performed at a mean interval of 23 months to investigate the prognostic implications of the radionuclide studies. Nine patients had cardiac events during the follow-up period. Univariate analysis showed that the number of discordant BMIPP versus 201TL uptake segments was the best predictor of future cardiac events (P=0.0245), followed by the presence of discordant BMIPP uptake (P=0.0388) and the number of 201TL redistribution segments (P=0.0444). When all the clinical and radionuclide variables were analysed by Cox regression analysis, the presence of discordant BMIPP uptake was the best, and an independent, predictor of future cardiac events (chi 2=8.5) followed by the number of coronary stenoses on angiography (chi 2=3.9). These preliminary data suggest that decreased BMIPP uptake relative to 201TL is a valuable predictor of future cardiac events in patients with myocardial infarction. Areas with such discordant BMIPP uptake may contain jeopardized myocardium where fatty acid utilization has been severely suppressed relative to myocardial perfusion.

Duration and magnitude of ST-segment depression during exercise and recovery: a symmetric relation

The pattern of appearance and disappearance of ST depression on 12-lead electrocardiographic exercise testing in subjects with coronary artery disease (> or = 70% stenosis) and its relation to the severity of disease were prospectively explored in 34 consecutive patients. The first lead to show positivity during exercise also developed maximum ST depression in 73% of patients and was the last lead to lose positivity in recovery (94%). The last lead to show positivity during exercise was first to lose positivity in recovery (92%). Greater ST depression was associated with a greater number of positive leads (p < 0.001; r = 0.7). The duration of ST depression during exercise, maximum ST depression, and recovery time were related (p = 0.001, r = 0.6; p = 0.006, r = 0.5; p < 0.001, r = 0.6, respectively, for the three interactions). However, the correlations of ST depression and recovery time with the severity of vessel disease and with rate-pressure product at initial ST depression were poor, suggesting that the degree of ST-segment depression and recovery time may depend more on the duration and intensity of myocardial ischemia solicited with exercise rather than on the ischemic threshold or on the severity of coronary artery disease.

Limited usefulness of exercise testing and thallium scintigraphy in evaluation of ambulatory patients several months after recovery from an acute coronary event: implications for management of stable coronary heart disease. Multicenter Myocardial Ischemia Research Group

OBJECTIVES

This study evaluated the value of noninvasive testing to predict cardiac events in patients with stable coronary disease after hospital admission (and risk stratification) for an acute coronary event.

BACKGROUND

Exercise testing with thallium perfusion imaging identifies patients with obstructive coronary artery disease and has been used to stratify patients after myocardial infarction. Its usefulness for predicting cardiac events in patients with stable coronary disease after recovery from an acute coronary event was explored.

METHODS

Nine hundred thirty-six patients were enrolled 1 to 6 months after hospital admission for a coronary event. Patients underwent exercise treadmill testing with planar thallium-201 scintigraphy and were followed up for an average of 23 months (range 6 to 43). End points were 1) unstable angina requiring hospital admission, nonfatal myocardial infarction or cardiac death; 2) nonfatal infarction or cardiac death; or 3) cardiac death alone.

RESULTS

Twelve patients died of cardiac causes (1.2%); 32 had a nonfatal myocardial infarction (3.4%); and 79 patients (8.4%) developed unstable angina in the first year. Exercise testing improved proportional hazards models constructed from clinical variables for all three end points (p < 0.05). The perfusion scan further improved models for the end points (nonfatal infarction or cardiac death and cardiac death alone, p < 0.05). However, the exercise test with or without thallium added little to the overall prediction of primary events (area under the receiver operating curve increased from 0.649 to 0.663), and only 2% to 13% of patients with abnormal results either had a nonfatal infarction or died.

CONCLUSIONS

Thallium-201 scintigraphy and exercise testing variables identify patients at risk for subsequent cardiac events. However, the poor predictive performance of these tests in this group of patients with stable coronary disease severely limits their usefulness. These results suggest a limited role for exercise and thallium testing in predicting cardiac events in patients with known coronary disease.

Clinical and pathophysiologic correlates of ST-T-wave abnormalities in coronary artery disease

Clinical, hemodynamic and coronary angiographic data from 9,801 patients were evaluated to determine the correlates of ST-segment depression, with or without T-wave inversion, on the resting routine electrocardiogram. The relative risk (RR) of having a measured clinical or angiographic variable was computed whether or not ST-T-wave abnormalities were observed. ST-segment depression was seen significantly more often in subjects greater than 55 years of age (RR = 1.4) who were women (RR = 1.3) or nonwhite (RR = 1.5), were hypertensive (RR = 1.8), had diabetes mellitus (RR = 1.6) or who smoked cigarettes (RR = 1.5). Angiographic findings related to presence of ST-T-wave abnormalities included severe coronary obstruction (less than 70%), higher number of diseased vessels, and the presence of obstruction in the left anterior descending coronary artery. In a multivariate model, the most significant correlates of ST-T-wave abnormalities were presence of left ventricular contraction abnormality, followed by age, gender, presence of left anterior descending coronary artery disease, elevated end-systolic volume index, and a diagnosis of hypertension. Thus, electrocardiographic ST-T abnormalities has specific and significant clinical and pathophysiologic correlates.

Alterations in transmural blood flow and body surface ST segment abnormalities produced by ischemia in the circumflex and left anterior descending coronary arterial beds of the dog

Previous studies have documented a quantitative relation between alterations in transmural myocardial blood flow and body surface electrocardiographic distributions during rapid atrial pacing after chronic occlusion of the left circumflex coronary artery (LCx). Because other studies have described functional differences between the left anterior descending (LAD) and the LCx perfusion beds, we tested the hypothesis that these two territories exhibit quantitative differences in their responses to demand-dependent myocardial ischemia. To do so, 25 sedated dogs were studied 3 weeks after implantation of an ameroid constrictor around the proximal LCx (15 dogs, group I) or the LAD (group II). Oxygen demand was increased by rapid atrial pacing at rates of 90 to 210 beats/min, myocardial blood flow was measured by serial injections of radiolabeled microspheres, and the electrocardiographic consequences were evaluated by isopotential body surface mapping. Endocardial flows and the endocardial/epicardial flow ratio fell to significantly lower levels during atrial pacing in the ischemic LAD bed than in the LCx perfusion zone. Electrocardiographic patterns indicative of subendocardial ischemia also developed with lesser abnormalities in endocardial/epicardial ratios as determined by logistic regression models, in the LAD than in the LCx bed. Thus the LAD bed is more susceptible to ischemia than the LCx region because of differences in collateral blood flow patterns. In addition, the intensity of the surface electrocardiographic potentials during ischemia was significantly greater, as measured by linear regression, after LAD than after LCx obstruction. These data thus demonstrate significant differences between the two cardiac regions as electrocardiographic potential sources during ischemia.

The influence of R-wave amplitude on the degree of ST-segment depression in exercise electrocardiography in the individual patient

Many factors have been found to influence the magnitude of ST-segment depression in the exercise electrocardiogram. We investigated whether R-wave amplitude is a significant factor. We studied the exercise electrocardiogram of 20 patients with angiographically documented coronary artery disease, including greater than or equal to 70% stenosis of the left anterior descending artery, who had an ischemic response to exercise but no previous anterior myocardial infarction. Precordial leads V1-6 were taken into account. When all 120 leads were measured, those with ST-segment depression greater than or equal to 2.0mm at peak exercise had a mean resting R-wave amplitude of 19.03 +/- 5.81mm; those with ST-segment depression 2.0-1.0mm, R 11.42 +/- 5.99mm; and those with ST-segment depression less than 1.0mm, R 5.9 +/- 5.21mm (p less than 0.001 between groups). When the R-wave amplitude was correlated with the ST-segment depression in each precordial lead, the correlation was 1.0. In leads V1-6, when 67 tracings with ST-segment depression greater than 0.5mm were measured, the correlation was 0.537 (p less than 0.001). In each precordial lead the t values of R-wave differences correlated very strongly (r less than 0.883) with the differences in ST-segment depression. We conclude that precordial R-wave amplitude significantly influences the magnitude of ST-segment depression.

Frequency of painless myocardial ischemia during exercise tolerance testing in patients with and without diabetes mellitus

To evaluate the frequency of painless myocardial ischemia, all patients with positive exercise tolerance test responses (at least 2 mm of ST depression) from 1983 to 1985 were examined. Of the 211 patients with exercise-induced ischemia, 101 (48%) did not have pain during the ischemic period; 26 (12%) had diabetes mellitus, 24 of whom (92%) had type II diabetes mellitus. Lack of pain was not correlated with age, gender, history of cigarette smoking, systemic hypertension, past acute myocardial infarction, coronary artery bypass grafting, use of beta-blocking or calcium-channel blocking drugs, number of narrowed coronary arteries or average calculated ejection fraction at cardiac catheterization. Patients with painless myocardial ischemia were less often taking nitrates (39% vs 55%, p less than 0.05) and reported prior episodes of chest pain less often (50% vs 82%, p less than 0.01) than control subjects. There was no difference in the frequency of painless myocardial ischemia between patients with and without diabetes mellitus (54% vs 47%). Duration of exercise was shorter in patients with diabetes mellitus and in patients who had pain with myocardial ischemia. No significant difference in age, gender, use of nitrates, beta-blocking or calcium-channel blocking drugs, history of myocardial infarction, angina pectoris or cigarette smoking was found between diabetic and nondiabetic patients. Systemic hypertension was more common in diabetic patients. Thus, painless myocardial ischemia is common in our patients with positive exercise tolerance test responses, but its frequency is similar in diabetic and nondiabetic patients.

Symptomatic coronary disease for 20 or more years: clinical aspects, angiographic findings, and therapeutic implications

Clinical, angiographic, and therapeutic aspect of coronary artery disease of long duration (exceeding 20 years) is reviewed in 50 patients (study group) and compared to a control group of 100 consecutive patients with coronary artery disease of shorter duration. All were referred because of symptomatic coronary artery disease. The study group had a greater incidence of clinically evident extracardiac vascular disease (28% vs 4%) (p less than 0.01). Transmural infarction was more frequent in the study group (64% vs 45%). Triple-vessel and main left disease was observed respectively in 90% and 28% compared to 36% and 7% in the control group (p less than 0.01). Twenty-nine percent of collaterals were jeopardized in the study group compared to 13% of collaterals in controls (p less than 0.01). Abnormal left ventricular ejection fraction (p less than 0.05) was found in 50% of the study group compared to 28% of controls (p less than 0.01). Medical therapy was recommended for 36% of the study group with 11 of 18 (61%) considered inoperable, whereas in 39% of the control group medical therapy was continued, with 9 of 39 (23%) considered inoperable (p less than 0.01) Surgery or coronary angioplasty was recommended in 64% of the study and in 61% of the control group. No patient in the study group was considered a candidate for coronary angioplasty, whereas in 20% (12 of 61) of the control group coronary angioplasty was recommended. Patients with coronary artery disease for over 20 years have severe coronary artery disease, with one in four having main left disease.(ABSTRACT TRUNCATED AT 250 WORDS)