LEFT-VENTRICULAR FUNCTIONAL RESERVE IN PATIENTS WITH SYNDROME-X - EVALUATION BY CONTINUOUS VENTRICULAR-FUNCTION MONITORING

Objectives. The objective of this study was to evaluate cardiac functional reserve in patients with syndrome X. Background. Syndrome X is characterized by stress-induced anginal pain and ST segment depression, normal findings on coronary angiography and normal left ventricular function at rest. Reduced coronary vasodilative reserve and abnormal myocardial lactate metabolism have been described in such patients. Methods. To assess left ventricular functional reserve in patients with syndrome X, continuous radionuclide monitoring of left ventricular end diastolic volume, end systolic volume and ejection fraction was performed in 12 patients and 13 normal control subjects during supine bicycle ergometer exercise. Results, In control subjects, end diastolic volume increased at peak exercise from 100% to 106.5% (p < 0.01), end-systolic volume decreased from 39.1% to 22.6% (p < 0.01) and ejection fraction increased from 60.9% to 78.6% (p < 0.01). In patients with syndrome X, end-diastolic volume increased at peak exercise from 100% to 106% (p < 0.01), and end-systolic volume decreased at ST segment depression less than or equal to 0.5 mm (the ST point) from 37% to 28.8% (p < 0.01) but increased at peak exercise to 44.7% (p < 0.01 vs. the ST point). Thus, ejection fraction increased at the ST point from 63% to 72.7% (p < 0.01) but decreased at peak exercise to 57.7% (p < 0.01 vs. the ST point and control subjects) in proportion to the degree of ST segment depression. In nine patients (75%), ejection fraction at peak exercise was lower than baseline values. All patients and control subjects showed a rapid ejection fraction increase just after exercise during the recovery period. The degree of ejection fraction ''overshoot'' in patients was similar to that in control subjects, but the interval from the end of exercise to the overshoot in patients was significantly longer than that in control subjects (118 vs. 65 s, p < 0.01). Conclusions. In patients with syndrome X subjected to exercise stress, left ventricular function remained normal before the onset of ST segment depression. Once ST segment depression appeared, left ventricular function deteriorated in proportion to the degree of depression, and reduced left ventricular function persisted into the recovery period. Continuous ventricular function monitoring is thus a useful predictor of reduced left ventricular functional reserve in patients with syndrome X.