A new method to quantify postexercise ST‐deviation – the ST‐deficit. A study in men at high and low‐risk for coronary heart disease

BACKGROUND: Quantitative heart rate adjusted exercise ST criteria like microV/beats per minute (bpm) improve the diagnostic accuracy of the exercise ECG. However, there are few quantitative HR adjusted postexercise variables available. The aim of the present exercise study was to evaluate a new such variable from computerized averaging of the postexercise ECG. METHODS: The presence of possible myocardial ischaemia in a population based sample of 74 elderly male hypertensives at high-risk of coronary heart disease, and in 42 age-matched clinically healthy males (reference group) at low-risk was assessed by exercise ECG. All men had a normal resting ECG without signs of ischaemia. VARIABLES STUDIED: standard ST-criteria, ST/HR slope < or =-2.4 microV. bpm-1, shape of the rate-recovery loop, the latter also with a new quantitative variable, the ST-deficit. RESULTS: In spite of a normal resting ECG many subjects showed an abnormal ST/HR slope during exercise, 43% in the hypertension group and 26% in the reference group. An abnormal rate-recovery loop (ST-deficit) also contributed substantially to identify patients with possible myocardial ischaemia, 30 vs. 10%, respectively (P<0.02); cumulatively for the two HR adjusted criteria 53% vs. 29%, respectively (P<0.02). Mean ST-deficit was significantly lower in the high-risk group. CONCLUSIONS: Effort-related myocardial ischaemia is frequently silent in elderly high-risk hypertensives and necessitates testing, preferably with computerized exercise ECG and heart rate adjusted ST criteria. A new quantitative variable to assess the postexercise rate-recovery loop in the time domain, the ST-deficit is described. This variable seems to effectively discriminate between subjects with low and high-risk for coronary heart disease and thus provides new information. Further studies are warranted to validate this variable against myocardial perfusion scintigraphy and coronary angiography.