LEFT-VENTRICULAR HYPERCONTRACTILITY AND ST SEGMENT DEPRESSION IN PATIENTS WITH SYNDROME-X

Objectives. This study was designed to assess the relation between res t left ventricular function and exercise capacity in patients with syn drome X. Background. Clinical observation has suggested that some pati ents with syndrome X have a high rest left ventricular ejection fracti on. In this study we determined the relation between left ventricular ejection fraction and exercise capacity and the electrocardiographic ( ECG) changes that develop on exercise. Methods. The pattern of left ve ntricular function, exercise capacity and 24-h ambulatory ECG monitori ng were studied in 37 patients (9 men, 28 women; mean age 52 +/- 7 yea rs) with syndrome X (angina with normal coronary arteries and a positi ve exercise test result). All patients had normal findings on echocard iogram and rest ECG. All treatment was dis continued for greater than or equal to 48 h. Left ventricular ejection fraction was determined by computerized analysis of the left ventricular angiogram. In patients with syndrome X, exercise duration and heart rate were measured at 1-m m ST segment depression and at peak exercise. Results. Left ventricula r hypercontractility (ejection fraction greater than or equal to 80%) was observed in 12 patients (32%) (group 1), whereas 25 patients (68%) had normal left ventricular contraction (group 2). The time to 1-mm S T depression on exercise testing was significantly earlier in group 1 than in group 2 (5.13 +/- 1.03 vs. 10.76 +/- 0.63 min, respectively, p < 0.001). The magnitude of the ST segment depression at peak exercise was significantly greater in group 1 than in group 2 (2.03 +/- 0.2 vs . 1.33 +/- 0.05 mm, respectively, p < 0.001). The mean time for ST seg ment depression to normalize was significantly greater in group 1 than in group 2 (4.76 +/- 0.78 vs. 3.16 +/- 0.39 min, respectively, p < 0. 05). Linear regression analysis of all patients with syndrome X showed a significant correlation between exercise duration and ejection frac tion (r = 0.55, p < 0.001). The mean circadian variation of heart rate and episodes of ST segment depression on 24-h ambulatory ECG monitori ng were similar in the two groups of patients. Conclusions. These find ings indicate that approximately one third of patients with chest pain , normal coronary angiograms and a positive exercise test have left ve ntricular hypercontractility, and this is associated with the developm ent of ST segment depression at a lower heart rate and work load and a longer time to normalization of ST segment depression after exercise.