• acute myocardial infarction;
  • acute coronary syndromes;
  • vectorcardiography;
  • ST-vector magnitude;
  • QRS-vector difference;
  • ST-segment monitoring

Background: Vectorcardiographic (VCG) measurements of ST-vector magnitude (VM) and QRS-vector difference (VD) have been demonstrated to be independent predictors of adverse outcome (AO) and acute myocardial infarction (AMI) in emergency department (ED) chest pain patients with absence of bundle branch block or left ventricular hypertrophy (LVH) on the initial 12-lead electrocardiogram (ECG). The prognostic value of ST-VM and QRS-VD in ED chest pain patients with LVH on the initial 12-lead ECG has not been previously investigated.

Methods: A prospective observational study was performed in 196 consecutive ED chest pain patients with suspected AMI and presence of voltage criteria for LVH on initial ECG who underwent continuous VCG monitoring during the initial evaluation. The optimal baseline ST-VM value and 2-hour QRS-VD value were defined as the most accurate value on the receiver operator characteristic curve (value with lowest false-negative and false-positive rate). Thirty-day AO was defined as AMI, percutaneous coronary intervention, coronary artery bypass grafting (CABG), or cardiac death occurring within 30 days of initial ED visit.

Results: Fourteen patients (7.1%) were diagnosed as 24-hour AMI and 28 patients (14.3%) experienced 30-day AO. The optimal cut-off value for predicting 30-day AO was >124 μV for ST-VM and >21.7 μV for QRS-VD. Patients with either a positive ST-VM or a positive QRS-VD had 8.8 times increased odds of AMI (95% confidence interval, CI, 1.9–40.3; P = 0.003); 4.3 times increased odds of 30-day PTCA/CABG (95% CI 1.3–13.8; P = 0.019); and 3.8 times increased odds of 30-day AO (95% CI 1.6–9.3; P = 0.003).

Conclusions: Baseline ST-VM and 2-hour QRS-VD risk stratifies ED chest pain patients with LVH voltage criteria on the initial 12-lead ECG.