Changes in the ST- and ventricular gradient vectors over a period of 25 years

The ECG is a major diagnostic instrument for the detection of acute ischemia and subsequent triaging of patients after first medical contact in the setting of acute coronary syndrome. However, sensitivity and specificity of the ECG with current diagnostic criteria are limited. When a previous non-ischemic ECG is available for reference purposes, comparison of the acute and reference ECG by serial analysis is known to increase sensitivity. For acceptable specificity in serial comparison it is a prerequisite that a reference ECG remains valid (is stable) in time. We compared, within 88 patients, 6 non-ischemic ECGs, each five years apart. The first ECG was used as a reference ECG, and each of the next 5 ECGs was compared with the initial reference ECG. We computed for each comparison the diference in the ST vector at the J point and 60 ms after the J point, and, additionally, the diference in the ventricular gradient (VG) vector. These diferences were interpreted in relation to the proposed ischemia thresholds of 50 fJ,V (ST vector) and 20 mVms (VG vector). Ischemia detection thresholds were increasingly exceeded with time, varying from 26% after 5 years to 60% after 25 years, when measured 60 ms after the J point. Actually, in our study group there were many more ECGs made than those selected for our study: measured from an arbitrarily chosen point in time the most recent ECG was only 1.3 years old. Hence, the serial analyses with a time lag of 5 years was the most relevant. Our study suggests that serial ECG comparison for ischemia detection in this patient group is feasible from the point of view of dynamics in the reference ECG.