The electrocardiographic "triangular QRS-ST-T waveform" pattern in patients with ST-segment elevation myocardial infarction: Incidence, pathophysiology and clinical implications.

BACKGROUND: A specific ECG pattern of presentation of ST-segment elevation acute myocardial infarction (STEMI), characterized by "triangular QRS-ST-T waveform" (TW), has been associated with poor in-hospital prognosis but longitudinal data on its incidence and clinical impact are lacking. We prospectively evaluated the incidence and prognostic meaning of the TW pattern in a cohort of consecutive STEMI patients. METHODS: All STEMI patients who presented within 12h of symptoms onset and showed no complete bundle branch block or paced ventricular rhythm were included. The TW pattern was defined as a unique, giant wave (amplitude≥1mV) resulting from the fusion of the QRS complex, the ST-segment and the T-wave and showing a "triangular" morphology with a positive polarity in the leads exploring the ischemic region. RESULTS: Among 428 consecutive STEMI patients, 367 fulfilled the enrollment criteria. The TW pattern was identified in 5 of 367 patients (1.4%) on the admission ECG. This subset of STEMI patients with TW pattern significantly more often showed a left main coronary artery involvement (2/4, 50% vs 2/322, 0.6%; p<0.001), experienced ventricular fibrillation (5/5, 100% vs 35/362, 9.6% p<0.001), had cardiogenic shock (4/5, 80% vs. 14/362, 3.8%, p<0.001) and died during hospitalization (2/5, 40% vs 15/362, 4.1% p=0.02), compared with those with other ST-segment elevation ECG patterns. CONCLUSIONS: The TW pattern is an uncommon ECG finding, which reflects the presence of a large area of transmural myocardial ischemia and predicts cardiogenic shock accounting for high in-hospital mortality. When present, this ECG pattern should prompt aggressive therapeutic strategies, including mechanical support of circulation.