Radionuclide evaluation of exercise left ventricular performance in patients with coronary artery disease

Physical training improves myocardial perfusion but not left ventricular function response to exercise in patients with microvascular angina

BACKGROUND

Patients with primary microvascular angina (PMA) commonly exhibit abnormal left ventricular function (LVF) during exercise, potentially owing to myocardial ischemia. Herein, we investigated in PMA patients the effect of the reduction of myocardial perfusion disorders, by using aerobic physical training, upon LVF response to exercise.

METHODS

Overall, 15 patients (mean age, 53.7±8.9 years) with PMA and 15 healthy controls (mean age, 51.0±9.4 years) were studied. All subjects were subjected to baseline resting and exercise ventriculography, myocardial perfusion scintigraphy (MPS), and cardiopulmonary testing. PMA group members then participated in a 4-month physical training program and were reevaluated via the same methods applied at baseline.

RESULTS

Baseline left ventricular ejection fraction (LVEF) determinations by ventriculography were similar for both groups (PMA, 67.7±10.2%; controls, 66.5±5.4%; P=0.67). However, a significant rise in LVEF seen in control subjects during exercise (75.3±6.2%; P=0.0001) did not materialize during peak exercise in patients with PMA (67.7±10.2%; P=0.47). Of the 12 patients in the PMA group who completed the training program, 10 showed a significant reduction in reversible perfusion defects during MPS. Nevertheless, LVEF at rest (63.5±8.7%) and at peak exercise (67.3±15.9%) did not differ significantly (P=0.30) in this subset.

CONCLUSIONS

In patients with PMA, reduced left ventricular inotropic reserve observed during exercise did not normalize after improving myocardial perfusion through aerobic physical training.

[Cardiovascular evaluation in athletic children]

Although rare, sports related sudden cardiac deaths in children and adolescents justify the search for risk factors in any child or adolescent who wishes to practice sports. Each time that history and careful clinical cardiovascular examination point to a possible cardiovascular abnormality, an electrocardiogram and an echocardiography must be performed. Exercise testing is useful to appreciate the cardiovascular tolerance, either in normal subjects or in subjects with a cardiovascular abnormality; its interpretation requires good knowledge and understanding of hemodynamic responses to exercise. Indications, risks and procedures of exercise testing are discussed with reference to exercise physiology.

Prediction of death and myocardial infarction by radionuclide angiocardiography in patients with suspected coronary artery disease

The prognostic value of radionuclide angiocardiography was examined in patients with suspected coronary artery disease. Nine hundred and eight patients who underwent rest and exercise radionuclide angiocardiography without subsequent cardiac catheterization were followed for a median of 4.6 years. Fifty-two cardiovascular deaths and 28 nonfatal myocardial infarctions occurred during the follow-up period. Thirty-nine radionuclide angiocardiographic and clinical variables were analyzed in association with the end points of cardiovascular death, total cardiac events and death from all causes using the Cox proportional hazards model and Kaplan-Meier survival estimates. Univariable analysis identified the exercise ejection fraction as the best predictor of cardiovascular death (chi-square = 82), total cardiac events (chi-square = 84) and death from all causes (chi-square = 66). A small subset of patients (n = 45) with an exercise ejection fraction less than 0.35 were at high risk for future cardiac events, whereas most patients (n = 776) had an exercise ejection fraction greater than or equal to 0.50 and a low probability of a subsequent event. Three variables--the exercise ejection fraction, the exercise change in heart rate, and gender--contained independent prognostic information determined by multivariable analysis. The exercise ejection fraction was the strongest independent predictor (p less than 0.0001) for every end point. The measurement of ventricular function during exercise provides important independent prognostic information in patients with suspected coronary artery disease. Radionuclide angiocardiography successfully identifies patients requiring invasive assessment, and the low probability of cardiac events in patients with good exercise ventricular function obviates the need for interventional therapy.

Insensitivity of noninvasive tests to detect coronary artery vasculopathy after heart transplant

Obstructive coronary artery vasculopathy can be a major problem after cardiac transplant. The use of noninvasive tests to detect coronary artery vasculopathy was studied in 73 consecutive patients after heart transplant. Angiographically or autopsy-proved coronary artery disease was noted in 19 consecutive patients (26%) followed prospectively for 2.5 +/- 1.3 years (mean +/- standard deviation). Patients underwent yearly surveillance echocardiographic, rest/exercise-gated wall motion, oral dipyridamole thallium, ambulatory electrocardiographic monitor and angiographic studies. Positive test results were defined by decrease in ejection fraction, wall motion abnormality, failure to increase ejection fraction, lack of systolic blood pressure increase, and ischemic ST changes at maximal exercise (or on ambulatory monitor). Wall motion abnormalities and depressed ejection fraction on echocardiography were also abnormal studies as were fixed or reversible perfusion defects on thallium scan. Angiograms were considered positive when 50% luminal narrowing was observed and autopsy coronary artery vasculopathy was defined as cross-sectional coronary obstruction greater than or equal to 70%. No procedure that was examined proved to be a sensitive noninvasive detector of heart transplant coronary artery vasculopathy. All except ambulatory electrocardiographic monitoring had positive predictive values less than 50%. Interestingly, of the techniques evaluated, echocardiography was most sensitive (53%). The poor predictive ability of noninvasive testing in this population may be due to the fact that these tests are designed to detect effects of ischemia rather than coronary obstruction alone. Use of these particular noninvasive modalities routinely after heart transplant to detect coronary artery vasculopathy should be reconsidered because of their low sensitivity and predictive value when used as a surveillance screen.

Left ventricular pressure/volume relationship in coronary artery disease

This study examined the changes during exercise in LV EF and P/V relationship (systolic blood pressure/end-systolic volume index ratio) in 287 patients. Normal range (mean +/- standard deviation) for exercise EF, exercise P/V, and the changes from rest to exercise (delta) in EF and P/V were established in 51 subjects with less than 1% probability of CAD. The results were compared to those obtained in 53 patients with normal coronary angiograms and 183 patients with angiographically proven CAD. Abnormality in either delta EF or percent delta P/V were observed in 76% of the patients with one-vessel disease and in 91% of patients with multivessel disease. Abnormalities in either delta EF or percent delta P/V were more common than delta EF alone in the total CAD group and in subgroups stratified according to the resting EF, extent of CAD, and adequacy of exercise end points. Similar results were obtained when absolute exercise EF or exercise P/V were used. Abnormalities in the percent delta P/V or delta EF were also seen in 26 of the 53 patients with normal coronary angiograms. Thus, abnormalities in the P/V relationship or EF during exercise are more common than abnormalities in the EF alone. Relative and absolute measurements provide similar results.