Exercise echocardiography is an accurate and cost-efficient technique for detection of coronary artery disease in women

Prognostic implications of exercise echocardiography in women with known or suspected coronary artery disease

OBJECTIVES

The purpose of this study was to define the value of exercise echocardiography as an independent predictor of cardiac events in women with known or suspected coronary artery disease (CAD), incremental to the data provided by clinical evaluation and exercise testing.

BACKGROUND

Exercise echocardiography is more accurate than exercise electrocardiography for the identification of CAD in women. However, the prognostic implications of exercise echocardiography, especially relative to exercise electrocardiography, are undefined.

METHODS

Symptom-limited exercise echocardiography was performed in 549 consecutive women between 1989 and 1993. Echocardiography and electrocardiography were performed before and after treadmill exercise; an abnormal result on exercise electrocardiography was defined by ST segment depression > 0.1 mV, ischemia by exercise echocardiography as a new or worse wall motion abnormality after exercise and scar by akinesia or dyskinesia at rest. After exclusion of six patients with uninterpretable studies (1%) and 35 (6%) lost to follow-up, 508 women (mean [+/-SD] age 55 +/- 11 years) were followed up for 41 +/- 10 months for cardiac-related death, infarction or late revascularization.

RESULTS

The group attained 92 +/- 10% of age-predicted maximal heart rate, with an exercise capacity of 7 +/- 2 metabolic equivalents. Of 420 women with an interpretable electrocardiogram, significant ST segment changes were present in 68 (16%). Results of exercise echocardiography were normal in 413 (81%) women, positive for ischemia in 66 (13%) and scar only in 29 (6%). No events occurred in 444 patients (89%), and 19 underwent primary revascularization (within 3 months of exercise test). Cardiac events occurred in 36 women (7%), including 17 who died of cardia causes and 19 who had a myocardial infarction or required late revascularization for progressive symptoms. On univariate analysis, the variables associated with cardiac mortality and total cardiac events were a history of CAD, diabetes, left ventricular hypertrophy, exercise capacity and echocardiographic evidence of myocardial ischemia and infarction. A Cox proportional hazards model showed the independent predictors of outcome to be known CAD (odds ratio [OR] 6.6, 95% confidence interval [CI] 3.2 to 13.7, p < 0.00001) and echocardiographic ischemia (OR 4.3, 95% CI 2.1 to 8.7, p < 0.0001). The prognostic value of exercise echocardiography incremental to clinical and exercise variables was demonstrated using sequential Cox models.

CONCLUSIONS

In this large cohort of women, exercise echocardiography provided key prognostic information incremental to clinical and exercise testing data.

Applying principles of pharmacoeconomic evaluation to perflenapent emulsion, a new echocardiographic contrast agent for use in cardiac function testing

A pharmacoeconomic evaluation was performed to determine the cost-effectiveness of perflenapent emulsion, a new contrast agent for use in echocardiography. A decision tree analysis was performed on data from the charts of 108 patients who had undergone stress echocardiography without contrast enhancement as part of a cardiac function or wall-motion study. An analysis of a theoretical cohort of patients was conducted to determine shifts in cost associated with enhancement of stress echocardiography with perflenapent emulsion. Outcome was determined by the point at which the clinician was able to determine a treatment course for the patient based on the diagnostic information given. Stress echocardiography without contrast was identified as the most cost-effective path in terms of a conclusive test. Perflenapent emulsion shows a positive cost impact in patients who have had an inconclusive stress echocardiogram without the use of a contrast agent. These results are supported by a sensitivity analysis across a wide range of pricing for perflenapent emulsion, a wide range of cost for a stress echocardiogram, and up to 99% efficacy of contrast-enhanced stress echocardiography.

Use of exercise echocardiography for prognostic evaluation of patients with known or suspected coronary artery disease

OBJECTIVES

This study prospectively compared the incremental prognostic benefit of exercise echocardiography with that of exercise testing in a large cohort.

BACKGROUND

Exercise echocardiography is widely accepted as a diagnostic tool, but the prognostic information provided by this test, incremental to clinical and stress testing evaluation, is ill-defined.

METHODS

Clinical, exercise and echocardiographic variables were studied in a consecutive group of 500 patients undergoing exercise echocardiography. After exclusion of patients who underwent revascularization within 3 months of the stress test (n = 16, 3%) and those lost to follow-up (n = 21, 4%), the remaining 463 patients (mean [+/-SD] age 57 +/- 12 years, 302 men) were followed-up for 44 +/- 11 months. Outcome was related to the exercise and echocardiographic findings, and the incremental prognostic benefit of exercise echocardiography was compared with that of standard exercise testing.

RESULTS

Cardiac events occurred in 81 patients (17%), including 33 (7%) with spontaneous events (cardiac death, myocardial infarction and unstable angina) and 48 with late revascularizations due to progressive symptoms. In a multivariate Cox proportional hazards model, the likelihood of any cardiac event was increased in the presence of ischemia (relative risk [RR] 5.06, 95% confidence interval [CI] 3.09 to 8.29, p < 0.001) and lessened by more maximal stress, measured as percent age-predicted maximal heart rate (RR per 5% increment 0.84, 95% CI 0.77 to 0.92, p < 0.001). Spontaneous events were more strongly predicted by ischemia (RR 8.20, 95% CI 3.41 to 19.71, p < 0.001) and percent age-predicted maximal heart rate (RR per 5% increment 0.78, 95% CI 0.67 to 0.91, p < 0.001). An interactive logistic regression model showed that the addition of echocardiographic to exercise and clinical data offered incremental predictive value.

CONCLUSIONS

The presence of ischemia on the exercise echocardiogram can predict whether patients will experience an event. This relation is independent of, and incremental to, clinical and exercise data.

Outcomes and cost implications of a clinical-based algorithm to guide the discriminate use of stress imaging before noncardiac surgery

Approximately 8 million patients at risk for coronary artery disease undergo noncardiac surgery annually in the United States. This study defined the appropriateness and cost of evaluating these patients with stress imaging tests. Before noncardiac surgery, 178 consecutive patients were prospectively studied by stress imaging. Pretest cardiac risk (low, intermediate, high) was established by interviewing the referring physician and separately by a cardiologist on the basis of the nature of noncardiac surgery and Eagle's clinical criteria. Patients were followed-up for alterations in management and perioperative events until hospital discharge. Referring physicians and cardiologists identified low risk in 24% and 54% of patients, respectively (p < 0.0001). Of 96 patients identified as low risk by cardiologists, 75 had minor surgery and 21 had major surgery, but no clinical risk factors. In the remaining 82 patients with major surgery, ischemia and other severe abnormalities were detected in 19 (23%) patients. At follow-up, no perioperative complications occurred in minor surgery; one patient with major surgery but no clinical risk factors died from complications related to hypertrophic cardiomyopathy. Patients with at least one clinical risk factor undergoing major surgery but who did not have ischemia on stress testing (n = 63) had two complications (infarction and unstable angina). Intervention (revascularization and surgical cancellation) was probably the explanation for the absence of events in 19 patients with ischemia. With a weighted mean Medicare reimbursement ($386), the use of a simple selection algorithm based on noncardiac surgery and clinical risk to avoid testing low-risk patients would have an average cost of $214 per patient, representing a 45% savings.

The specificity of exercise electrocardiography in women grouped by estrogen status

We compared the specificity of exercise electrocardiography in 1880 men and 1818 women with women grouped by menopausal and estrogen replacement status. Specificity for > or = 1 mm horizontal or downsloping ST-segment depression was determined using angiography in 781 patients and using two other nonangiography-based methods (a pretest probability-based method and a predictive accuracy-based method) in all patients. Using angiography, the specificities+/-SE were 84 +/- 2 for men, 79 +/- 3 for women, 81 +/- 5 for premenopausal women, 81 +/- 4 for postmenopausal women without estrogen replacement, and 77 +/- 5 for women on estrogen replacement. None of these were significantly different. For all patients, the respective specificities using the probability and predictive accuracy-based methods were 97 +/- 1 and 94 +/- 1 for men, 90 +/- 1 and 88 +/- 1 for women, 97 +/- 1 and 92 +/- 2 for premenopausal women, 92 +/- 4 and 88 +/- 3 for postmenopausal women without estrogen replacement, and 85 +/- 4 and 81 +/- 3 for women on estrogen replacement. (Men vs. all women groups except premenopausal women-P < 0.05). Therefore, the premenopausal women had significantly greater specificity than women on estrogen replacement (P < 0.001) and no difference in specificity with men. Women on estrogen replacement had a significantly lower specificity than postmenopausal women not on estrogen replacement (P < 0.05). These results suggest that estrogen replacement therapy and not naturally occurring estrogen has a role in producing false positive exercise electrocardiograms in women.

Sex and test verification bias. Impact on the diagnostic value of exercise echocardiography

BACKGROUND

The use of exercise echocardiography for the diagnosis of coronary artery disease (CAD) has been validated in pilot studies but is not documented in clinical practice and in women comparatively with men. The objectives of this study were to determine the effects of sex and of test verification bias on the diagnostic performance of exercise echocardiography.

METHODS AND RESULTS

Three thousand six hundred seventy-nine consecutive patients (1714 women, 1965 men) who underwent an exercise echocardiographic study were studied; the observed sensitivity, specificity, and correct classification rate were calculated among 340 patients (244 men, 96 women) who underwent angiography; to study the effect of test verification bias, sensitivity and specificity were estimated for all patients who underwent exercise echocardiography including those not referred to angiography. In the angiographic group, the prevalence of CAD was 60% in women and 80% in men. The observed sensitivity and specificity of exercise echocardiography was 78% and 44% in men and 79% and 37% in women. After adjustment for test verification bias, the estimated sensitivity was lower in women (32% versus 42% in men), whereas specificity was similar in both sexes. The positive predictive value was lower in women (66%) compared with men (84%).

CONCLUSIONS

In clinical practice, test verification bias results in a lower observed specificity and a higher sensitivity of exercise echocardiography. In women, positive predictive value and adjusted sensitivity are lower compared with that in men.

Adenosine technetium-99m sestamibi myocardial perfusion SPECT in women: diagnostic efficacy in detection of coronary artery disease

OBJECTIVES

This study sought to assess the diagnostic efficacy of adenosine technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) in a consecutive series of female patients.

BACKGROUND

The utility of adenosine myocardial perfusion SPECT for the detection of coronary artery disease is not well defined in women because most studies have described a predominantly male population with a high prevalence of coronary artery disease.

METHODS

Of the 201 consecutive female patients in the study group who had undergone adenosine Tc-99m sestamibi myocardial perfusion SPECT, 130 had coronary angiography within 2 months of the nuclear test, and the other 71 had a low likelihood (<10%, mean [+/-SD] 5 +/- 3%) of coronary artery disease. The SPECT protocol used separate acquisition of rest thallium-201 and adenosine Tc-99m sestamibi and was visually analyzed in 20 segments with a semiquantitative five-point scoring system (0=normal; 4=absent uptake).

RESULTS

The normalcy rate in patients with a low likelihood of coronary artery disease was 93% (66 of 71). Among the catheterized group, the overall sensitivity, specificity and predictive accuracy of adenosine sestamibi SPECT for detecting coronary artery disease (> or = to 50% diameter stenosis) were 93% (87 of 94), 78% (28 of 36) and 88% (115 of 130), respectively. In the 103 patients without a prior myocardial infarction, the sensitivity, specificity and predictive accuracy were 91% (61 of 67), 78% (28 of 36) and 86% (89 of 103), respectively, for detecting > or = to 50% diameter stenosis. Of particular interest, the sensitivity and specificity were as high in patients with nonanginal symptoms (93% and 69%, respectively) as in patients with angina (92% and 83%, respectively, p=NS). The sensitivity and specificity among patients with a relatively low (<25%), intermediate (between 25% and 75%) or high prescan likelihood of coronary artery disease (>75%) were similar: 82% and 82%, 93% and 73%, and 95% and 100%, respectively. The sensitivity and specificity for detecting individual diseased vessels (> or = to 50% diameter stenosis) were, respectively, 76% and 81% for the left anterior descending coronary artery, 44% and 90% for the left circumflex coronary artery and 75% and 77% for the right coronary artery.

CONCLUSIONS

Adenosine Tc-99m sestamibi SPECT is an efficient protocol with high sensitivity and specificity for the detection of coronary artery disease in women irrespective of presenting symptoms or pretest likelihood of coronary artery disease and a high normalcy rate. These findings are of particular clinical relevance because chest pain, anginal or otherwise, has been shown to be a frequent but a less specific marker for coronary artery disease among female patients.

Dobutamine-induced hypoperfusion without transient wall motion abnormalities: less severe ischemia or less severe stress?

OBJECTIVES

This study sought to compare the clinical characteristics, hemodynamic response and severity of ischemia in patients with coronary artery disease and reversible perfusion defects on dobutamine 2-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography (SPECT) with or without transient wall motion abnormalities.

BACKGROUND

The occurrence of reversible perfusion defects without concomitant wall motion abnormalities in patients with coronary artery disease was attributed to less severe ischemia. However, little data are available to support this observation.

METHODS

Fifty-four consecutive patients with significant coronary artery disease and reversible perfusion defects on dobutamine (up to 40 micrograms/kg body weight per min) MIBI SPECT were studied (mean [+/- SD] age 59 +/- 11 years; 38 men, 16 women). All patients underwent simultaneous echocardiography. The myocardium was divided into six matched segments, and ischemic perfusion score was quantitatively derived in myocardial segments with reversible defects.

RESULTS

New or worsening wall motion abnormalities occurred in 40 patients (74%) (group A) and were absent in 14 (26%) (group B). There was no significant difference between the two groups with respect to age, previous myocardial infarction, number of abnormal coronary arteries (1.8 +/- 0.8 vs. 1.6 +/- 0.9), number of reversible perfusion defects (1.6 +/- 0.9 vs. 1.8 +/- 0.7) or ischemic perfusion score (412 +/- 750 vs. 526 +/- 553). Patients in group A had a higher prevalence of male gender (80% vs. 43%, p < 0.01), higher peak systolic blood pressure (147 +/- 30 vs. 127 +/- 31 mm Hg, p < 0.05), higher peak rate-pressure product (19,632 +/- 4,081 vs. 16,939 +/- 4,344, p < 0.01) and a higher prevalence of angina (53% vs. 14%) and ST segment depression (55% vs. 14%) than group B (p < 0.05 for both).

CONCLUSIONS

In patients with coronary artery disease and ischemia on dobutamine MIBI SPECT, the absence of transient wall motion abnormalities is associated with a similar extent and severity of reversible perfusion defects, a lower stress rate-pressure product and a higher prevalence of female gender than patients with transient wall motion abnormalities. Mechanically silent ischemia should not be regarded as a marker of less severe ischemia on myocardial perfusion scintigraphy.