Implications of normal exercise electrocardiographic results in patients with angiographically documented coronary artery disease. Correlation with left ventricular function and myocardial perfusion

Triple vessel coronary artery disease presenting as a markedly positive stress electrocardiographic test and a negative SPECT-TL scintigram: a case of balanced ischemia

The presence of false negative nuclear stress test in the settings of positive electrocardiographic changes is a very unusual phenomenon and is usually secondary to balanced ischemia of the myocardial segments evaluated by SPECT-TL. We present a case of an 81-year old post-menopausal female who presented to her primary care physician for evaluation of a 6-week dyspnea on exertion and was referred to our institution for exercise stress test with Thallium SPECT with the objective of ruling out coronary artery disease and identifying possible areas of myocardial ischemia. The resting electrocardiogram was unremarkable and stress test evaluation was made. The patient was admitted to the cardiac care unit and coronary artery bypass grafting was successfully performed. The presence of false negative nuclear stress test in the settings of positive electrocardiographic changes is a very unusual phenomenon and is usually secondary to balanced ischemia of the myocardial segments evaluated by SPECT-TL. Patients undergoing stress tests with these characteristics should undergo careful evaluation and a high level of suspicion should be adopted for further diagnostic assessment of coronary artery disease.

Prevalence and prognostic value of perfusion defects detected by stress technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography in asymptomatic patients with diabetes mellitus and no known coronary artery disease

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in diabetics. Early diagnosis of CAD and identification of high-risk subgroups, followed by appropriate therapy, may therefore enhance survival. This study sought to determine the value of stress myocardial perfusion single-photon emission computed tomography (SPECT) with technetium-99m sestamibi to detect perfusion defects and predict cardiac events in asymptomatic diabetics. One hundred eighty asymptomatic diabetics without known CAD who underwent 2-day stress technetium-99m sestamibi SPECT were followed up for 36 +/- 18 months. End points were defined as hard (myocardial infarction or cardiac death) or total events (myocardial infarction, cardiac death, or late revascularization). Logistic regression analysis evaluated clinical variables, type of stress, exercise treadmill test (ETT), and SPECT as predictors of end points. Perfusion defects were found in 26% of patients (15% reversible, 6% mixed, and 5% fixed). Clinical or ETT variables were not associated with perfusion defect type or with hard events. However, male gender predicted total events (chi-square 3.3; p = 0.01). An abnormal SPECT significantly increased the risk of hard events (chi-square 5.4; p = 0.001) and total events (chi-square 7.4; p = 0.0001). Extensive defects determined the highest risk of total events (chi-square 18.8; p = 0.0001). Event rates increased according to SPECT: 2% of hard events per year and 5% of total events per year in patients with normal SPECT versus 9% per year and 38% per year, respectively, in those with abnormal SPECT. Importantly, a normal SPECT identified a relatively low-risk subgroup of patients. Thus, stress technetium-99m sestamibi SPECT was useful in evaluating asymptomatic diabetics for the presence of CAD, and effectively risk-stratified this population.

Significance of ST-segment depression with R-wave amplitude decrease on exercise testing

A retrospective evaluation was performed of patients who underwent exercise tests and angiography and 50 ambulatory normal subjects who underwent only exercise testing. We found that when deltaST depression of 0.5 mm was combined with deltaR-wave decrease of 1 mm, the sensitivity and specificity were improved.

Hemodynamic characteristics of patients with coronary artery disease presenting false-negative exercise stress test

The present study was designed to clarify the characteristics of left ventricular hemodynamics and coronary arteries in patients with coronary artery disease presenting false-negative response to the Master's two-step stress test. Eighty-eight consecutive patients performed the Master's two-step stress test and had coronary angiography for evaluation of suspected or known coronary artery disease. The frequency of false-negative and true-positive responses in the Master's two-step stress test was 20% and 45%, respectively. Elevated left ventricular end-diastolic pressure, reduced ejection fraction, and low cardiac output characterized the left ventricular hemodynamics in patients with false-negative responses, as compared with those with true-positive response. The severity and extent of coronary artery disease, as well as prior myocardial infarction, did not affect the frequency of false-negative response. This study indicates that the false-negative response to the Master's two-step test is unexpectedly frequent in coronary artery disease with severe left ventricular dysfunction. Thus, one should be careful in judging the results of the Master's two-step test in symptomatic patients with severe left ventricular dysfunction.

Relation between left ventricular diastolic function and exercise tolerance in patients with left ventricular dysfunction

Previous studies show no correlation between resting systolic left ventricular performance assessed as the ejection fraction and exercise tolerance. This study examined the relation between left ventricular diastolic performance and exercise tolerance in 63 patients with left ventricular dysfunction (ejection fraction less than 50%) due to known or suspected coronary artery disease. The 51 men and 12 women, aged 54 +/- 8 years (mean +/- standard deviation), underwent symptom-limited upright exercise testing on a bicycle ergometer. The exercise end-points were angina (n:5), dyspnea (n:16), and fatigue (n:42). The patients were divided into three groups: group 1 (n:28) with normal exercise tolerance (9.5 +/- 2.4 minutes), group 2 (n:18) with mild exercise intolerance (5.8 +/- 0.5 minutes), and group 3 (n:17) had severe exercise intolerance (3.7 +/- 0.9 minutes). The three groups did not differ in age, ejection fraction, end-diastolic volume, exercise end-point, exercise heart rate, and left ventricular peak filling rate at rest. The exercise peak filling rate was, however, significantly higher in group 1 (p = 0.03). Stepwise multivariate discriminant analysis of important variables identified the exercise peak filling rate as the only predictor of exercise tolerance (F = 6.0). Thus, variation in exercise peak filling rate may in part explain the variability of exercise tolerance in patients with left ventricular dysfunction; patients with preserved exercise capacity have higher exercise peak filling rate than those with exercise intolerance.

The relation between myocardial ischemia and the ejection fraction response to exercise in patients with normal or abnormal resting left ventricular function

This study examines the relation between myocardial ischemia and the left ventricular (LV) ejection fraction (EF) response to exercise in patients with normal or abnormal resting EF. We studied 69 patients aged 25 to 78 years (mean 52 years) by radionuclide ventriculography (at rest and during peak upright exercise) and by exercise thallium-201 imaging. In 27 patients with resting EF less than 50%, the EF response to exercise was normal (greater than or equal to 5% increase) in 13 patients and abnormal in 14. The thallium scans showed reversible defects in 11 of the 14 patients (79%) with abnormal response but none in any of the patients with normal responses (p = 0.0001). In the 42 patients with resting EF greater than or equal to 50%, the EF response to exercise was normal in 23 and abnormal in 19. Reversible defects were present in 13 of the 19 patients (68%) with abnormal response and in only 3 of 23 patients (13%) with normal response (p = 0.0001). Therefore, an abnormal EF response to exercise was seen in 11 of 11 patients with resting EF less than 50% and in 13 of 16 patients (81%) with resting EF greater than or equal to 50% who had reversible thallium defects; normal EF responses were seen in 13 of the 16 patients (81%) with resting EF less than 50% and in 20 of 26 patients (77%) with resting EF greater than or equal to 50% who had no reversible thallium defects. Thus, in patients with abnormal resting LV function an abnormal EF response to exercise suggests the presence of myocardial ischemia rather than a nonspecific response to stress.

Similarity between women and men in manifestation of myocardial ischemia during exercise

We assessed the effect of gender on the electrocardiographic changes and thallium-201 myocardial perfusion during exercise in patients with coronary artery disease. Eighty-nine patients with coronary artery disease (50% or greater diameter narrowing of one or more major coronary arteries) who had undergone exercise thallium scintigraphy were retrospectively studied. There were 29 women and 60 men. Fifty-six patients had one-vessel disease, 11 patients had two-vessel disease, and 22 patients had three-vessel disease or left main disease. The extent of coronary artery disease was assessed by the Gensini score. There was no difference between men and women in age, medications, number of diseased vessels and the coronary artery disease score. Exercise tolerance was lower, although insignificantly in women compared to men. However, exercise heart rate, double product, and the electrocardiographic response were similar in men and women. Also, both the presence and size of exercise-induced perfusion defects were similar in men and women. Thus, the electrocardiographic response to exercise is not influenced by gender in patients with similar extent of coronary artery disease and comparable manifestations of myocardial ischemia.

Relation between electrocardiographic and scintigraphic location of myocardial ischemia during exercise in one-vessel coronary artery disease

The purpose of this study was to determine the usefulness of exercise electrocardiography in predicting the site of myocardial ischemia. Fifty-two patients were studied who had angiographically documented 1-vessel coronary artery disease (CAD) and exercise-induced reversible thallium-201 perfusion defects. The patients were divided into 2 groups: group I (28 patients) had left anterior descending CAD and group II (24 patients) had left circumflex or right CAD. There were no significant differences between the 2 groups in severity of coronary stenosis, heart rate and systolic blood pressure during exercise. The size of the perfusion defect was larger in group I than II (28 +/- 12% vs 19 +/- 10%, p less than 0.02). There was no significant difference between the 2 groups in the frequency of ST depression in the anterior, inferior or lateral electrocardiographic leads. ST depression occurred in 16 patients (57%) in group I and 11 patients (46%) in group II (difference not significant). The sensitivity of the exercise electrocardiogram was 52% using 12 leads, 50% using 3 leads (V3, V5 and aVF) and 50% using V5 alone (difference not significant). Thus, the site of ST depression during exercise is not a good predictor of the site of exercise-induced perfusion defect or anatomic site of CAD. The use of 12 leads does not improve the sensitivity of exercise electrocardiography in patients with CAD.

R wave amplitude: a new determinant of failure of patients with coronary heart disease to manifest ST segment depression during exercise

Patients with coronary artery disease may not manifest ST segment depression during exercise. Inadequate stress, mild coronary artery disease and severe left ventricular dysfunction have been postulated as mechanisms. The purpose of this study was to determine the influence of exercise R wave amplitude on ST segment depression in 81 patients with coronary artery disease (50% or greater diameter narrowing of one or more vessels). All patients underwent symptom-limited treadmill exercise testing and 71 patients (88%) had concomitant thallium-201 imaging. In 26 patients, the exercise R wave amplitude in electrocardiographic lead V5 was less than 11 mm (Group I), and in 55 patients it was 11 mm or greater (Group II). The two groups were similar with regard to age, sex, propranolol administration and left ventricular function. There was a significant difference in the incidence of positive exercise electrocardiograms in the two groups (2 patients [8%] in Group I and 27 patients [49%] in Group II; p = 0.002), despite similar exercise heart rate and extent of coronary artery disease. Myocardial ischemia, manifested by exercise-induced angina or exercise-induced thallium-201 perfusion defects, was similar in both groups. Thallium-201 imaging showed perfusion defects in 73% of patients in Group I and in 76% of patients in Group II (p = not significant). Thus, R wave amplitude is a new determinant of failure to develop ST depression during exercise. A low R wave amplitude (less than 11 mm) is rarely associated with ST depression, even in patients with multivessel coronary artery disease. Exercise thallium-201 imaging is a valuable diagnostic tool in patients with low R wave amplitude.