Time from acute coronary occlusion to electrocardiographic ischemic findings in humans: A controlled balloon occlusion study.

Conventional teaching describes a fixed sequence: hyperacute T waves within minutes, ST-segment elevation at approximately 30 min, and pathologic Q waves over hours. No primary study reports that interval; experimental occlusion places ST elevation within 25 to 40 s of ligation. In STAFF III (104 patients, 142 recordings), balloon inflation during elective angioplasty produces complete occlusion with the onset recorded to the second. Three criteria were applied to 10-s windows on a 5-s grid: guideline ST-elevation cutoffs at the J point relative to the PQ junction, the Meyers hyperacute T-wave score, and the Birnbaum terminal QRS distortion definition referred to each patient's own baseline. In leads subtending the occluded artery, ST-segment displacement and the hyperacute T-wave score both exceeded resting variability within 15 s and rose faster during occlusion than at rest (P < .001). Criteria were satisfied within 1 to 2 min: ST elevation in 71 of 104 patients (68%) at 50 s, terminal QRS distortion in 24 (23%) at 80 s, and hyperacute T waves in 16 (15%) at 70 s. Q waves could not be resolved. After deflation, Wellens type A predominated in anterior leads (6.2% vs 1.3% of other leads; P = .001), whereas type B did not. Ischemic electrocardiographic change begins within seconds of abrupt complete occlusion, with the T wave and the ST segment affected together. The traditional interval reflects the intermittent, incomplete occlusion of spontaneous infarction and clinical sampling intervals, rather than any latency in the myocardial response.