ASSESSMENT OF EARLY POSTINFARCTION ISCHEMIA - CORRELATION BETWEEN AMBULATORY ELECTROCARDIOGRAPHIC MONITORING AND EXERCISE TREADMILL TESTING

PURPOSE: Demand-related myocardial ischemia detected by treadmill test ing is commonly used to identify high-risk patients after myocardial i nfarction (MI). Although ischemia detected by ambulatory electrocardio graphic monitoring (AECG) has also been shown to predict poor outcome in some patient groups, the relationship between AECG-detected ischemi c ST changes and post-MI treadmill ischemia is unknown. PATIENTS AND M ETHODS: We screened 94 patients after MI with 24-hour AECG monitoring and a Naughton treadmill test. Forty-two patients were excluded becaus e of left bundle branch block, left ventricular hypertrophy, abnOrmal baseline ST segments, or digoxin therapy. In the remaining 52 patients , AECG was performed 5.1 +/- 2.2 days after MI (mean +/- SD) and the t readmill test 8.4 +/- 2.2 days after MI. Each patient was taking the s ame drugs for both studies, had no interim revascularization procedure s, and all studies were interpreted blindly. RESULTS: The treadmill te st (ETT) was positive for ST changes and/or thallium reperfusion defec ts in 19 of 52 patients (36%). The AECG was positive for ischemia (ST depression greater than 1 mm, for more than 1 minute) in 14 of 52 pati ents (27%) (Group I), with 9.9 +/- 8.2 ischemic episodes per patient l asting 13.5 +/- 7.5 minutes per episode. The AECG was negative for isc hemia in the remaining 38 patients (73%) (Group II). The ETT and AECG correlation was as follows: 9 patients with AECG-detected ischemic ST changes had positive ETT results; 10 patients without AECG-detected is chemic ST changes had positive ETT results; 5 patients with AECG-detec ted ischemic ST changes had negative ETT results; and 28 patients with out AECG-detected ischemic ST changes had negative EtT results (p < 0. 02 by chi2). The predictive accuracy of a positive AECG identifying a positive ETT was 65% (specificity 85%, sensitivity 47%), and the predi ctive accuracy of a negative AECG identifying a negative ETT was 74%. Group I patients were older than Group H patients (63.6 +/- 8.2 years versus 53.2 +/- 10.6 years p < 0.02), more commonly had painless ETT i schemia (43% versus 18% p = 0.08), and tended to have positive ETT res ults at a lower level of exercise (366 +/- 210 seconds versus 588 212 seconds, p = 0.04). CONCLUSION: Ischemic ST changes as detected by AEC G monitoring correlate significantly with post-MI treadmill test resul ts with a high specificity, albeit a low sensitivity. In patients with out baseline ST-segment abnormalities and limited exercise capability, AECG monitoring may be of limited use in identifying early post-MI is chemia.