Coronary artery disease: evaluation by the multistage treadmill exercise test and right atrial pacing

Alterations in left ventricular volumes and ejection fraction during atrial pacing in patients with coronary artery disease: assessment with radionuclide ventriculography

The present study was performed to determine the utility of radionuclide ventriculography (RNV) in conjunction with atrial pacing in the identification of individuals with coronary artery disease. Accordingly, left ventricular end-diastolic volume index, end-systolic volume index, ejection fraction, and regional wall motion were measured with radionuclide ventriculography before and during atrial pacing in 37 patients: 27 with and 10 without (control subjects) coronary artery disease. In the control subjects, pacing caused a decrease in end-diastolic volume index (77 +/- 19 [mean +/- SD] ml/M2 at rest, 50 +/- 18 ml/M2 at peak pacing; p less than 0.001), a decrease in end-systolic volume index (34 +/- 14 ml/M2 at rest, 19 +/- 9 ml/M2 at peak pacing; p less than 0.001), an increase in ejection fraction (0.61 +/- 0.11 at rest, 0.66 +/- 0.11 at peak pacing; p = 0.006); and no deterioration in wall motion. In 16 patients with coronary artery disease who developed ECG and/or metabolic evidence of ischemia during pacing, end-diastolic volume index decreased (87 +/- 26 ml/M2 at rest, 69 +/- 24 ml/M2 at peak pacing; p less than 0.001), end-systolic volume index was unchanged (43 +/- 20 ml/M2 at rest, 44 +/- 21 ml/M2 at peak pacing; p = NS), ejection fraction decreased (0.55 +/- 0.12 at rest, 0.40 +/- 0.14 at peak pacing; p less than 0.001), and new wall motion abnormalities developed in 14. In 11 patients with coronary artery disease but no ECG or metabolic evidence of ischemia, pacing caused a decrease in end-diastolic volume index (80 +/- 26 ml/M2 to 61 +/- 31 ml/M2; p less than 0.001), a decrease in end-systolic volume index (36 +/- 17 ml/M2 to 28 +/- 20 ml/M2; p = 0.002), no change in ejection fraction (0.60 +/- 0.11 to 0.60 +/- 0.13; p = NS), and new wall motion abnormalities in four. Although the specificity of these scintigraphic measurements for the identification of patients with coronary artery disease was excellent (1.0), the combined sensitivity of all scintigraphic measurements was high only if ECG or metabolic evidence of ischemia was present: 0.94 in patients with evidence of ischemia but only 0.36 in those without ischemia. Thus radionuclide ventriculography during incremental atrial pacing is useful in the identification of patients with coronary artery disease only if ischemia is induced.

Comparison of right atrial pacing soon after myocardial infarction with treadmill testing 6 months later

Seventy-four patients recovering from acute myocardial infarction underwent right atrial pacing before hospital discharge, and treadmill exercise testing 6 months later. The early right atrial pacing test was positive in 32 patients (43 percent) and the late treadmill test was positive in 32 patients (42 percent). The results of the two tests were concordant in 77 percent of the patients, 23 with an ischemic response and 34 with a normal response on both tests. In nine patients a positive right atrial pacing test was followed by a negative treadmill test, and in eight patients a negative pacing test was followed by a positive treadmill test. A positive right atrial pacing test at hospital discharge had an 81.0 percent predictive accuracy for a positive late treadmill test; chest pain, congestive heart failure or increased cardiothoracic ratio at discharge had a predictive value of only 52.9, 42.8 and 42.8 percent, respectively. Both the early right atrial pacing test and the late treadmill test were positive in a significantly higher proportion of patients with inferior or subendocardial infarction than of patients with anterior myocardial infarction. During early right atrial pacing the mean maximal heart rate achieved was higher than that during late treadmill testing (148 versus 133 beats/min) and the mean systolic blood pressure was lower (137 versus 162 mm Hg), but the pressure-rate product was similar on the two tests (20,282 versus 21,455 mm Hg/min). This finding may explain the similar frequency of ischemic responses to the two tests. These results indicate that the response to right atrial pacing soon after myocardial infarction is a good predictor for the presence or absence of an ischemic response to treadmill testing 6 months later. Thus, early right atrial pacing at the time of hospital discharge may be used to determine the pace of rehabilitation and short-term prognosis.