RELATION BETWEEN LEFT-VENTRICULAR FUNCTION AT REST AND WITH EXERCISE AND SILENT-MYOCARDIAL-ISCHEMIA

The prognostic value of radionuclide measures of left ventricular func tion at rest and exercise is well established. Some studies have sugge sted that the frequency and duration of silent ischemia during ambulat ory monitoring provide similar prognostic information; however, studie s comparing these two techniques have not been performed. This study e xamines the relation between left ventricular function at rest and exe rcise-induced ischemia assessed by radionuclide ventriculography with myocardial ischemia during ambulatory electrocardiographic (ECG) monit oring. Of the 155 patients with coronary artery disease studied, 88% h ad left ventricular dysfunction with exercise, defined as failure of t he ejection fraction to increase by > 4% with exercise, and 33% of pat ients had left ventricular dysfunction at rest (ejection fraction < 45 %); 52% had transient episodes of ST segment depression during 48-h am bulatory ECG monitoring. Exercise-induced left ventricular dysfunction during radionuclide ventriculography was extremely sensitive (94%) in detecting patients with ischemic episodes during ambulatory ECG monit oring; however, only 55% of patients with exercise-induced left ventri cular dysfunction had ST segment depression during ambulatory monitori ng. Moreover, patients with left ventricular dysfunction at rest had a lower prevalence of transient episodes of ST segment depression (31%) than did patients with normal left ventricular function at rest (62%) (p = 0.008). The relation between prognostically important variables during exercise radionuclide ventriculography and the number and durat ion of transient episodes of ST depression was examined. By multivaria te regression analysis only the change in left ventricular ejection fr action with exercise was independently related to the number and durat ion of episodes of ST depression, but these correlations were weak (r2 = 0.04, p < 0.01 and r2 = 0.03, p = 0.05, respectively). Thus, myocar dial ischemia during daily life detected by ST segment monitoring corr elates poorly with radionuclide ventriculographic measures of ischemia . This is particularly evident in patients with left ventricular dysfu nction at rest in whom episodes of transient ST segment depression are infrequent. Ambulatory ST segment monitoring must be used with cautio n in risk stratification of patients with coronary artery disease, esp ecially in patients with left ventricular dysfunction after myocardial infarction.