EXERCISE ECHOCARDIOGRAPHIC CORRELATES OF TRANSIENT DILATATION OF THE LEFT-VENTRICULAR CAVITY ON EXERCISE THALLIUM-501 SPECT IMAGING

Transient dilatation of the left ventricular cavity on exercise thalli um perfusion imaging is recognized as a marker of significant coronary disease, but the mechanisms that produce this finding are not fully u nderstood. We studied 32 patients who underwent exercise thallium imag ing and exercise echocardiography to determine the changes in left ven tricular cavity size that underlie transient dilatation. Left ventricu lar area from the apical four-chamber view was used to approximate lef t ventricular cavity size. There were 24 patients who did not have tra nsient dilatation (group 1) and 8 patients who did have transient dila tation (group 2) on thallium imaging. Systolic area decreased from res t to exercise in group 1 patients but not in group 2 patients. There w as no significant change in diastolic area from rest to exercise in ei ther group 1 or group 2 patients. Thus, exercise-induced systolic dysf unction, manifested as a failure to decrease left ventricular systolic cavity size in exercise, may be an important mechanism in producing s cintigraphic transient dilatation.