The association of sustained ventricular tachycardia/fibrillation (VT/VF) with mortality in patients undergoing primary percutaneous coronary intervention (PCI) may vary with baseline patient risk and may be associated with higher mortality in patients who have high-risk baseline features but not in the low-risk patient cohort undergoing this procedure.

Among the 5,259 ST Elevation Myocardial Infarction (STEMI) patients presenting for primary PCI from the APEX AMI trial, we evaluated the association of VT/VF with outcomes according to underlying risk for 90-day mortality estimated using baseline variables and with a Cox regression model.

Ventricular tachycardia/fibrillation occurred in 3.6% (63/1,736), 4.9% (87/1,788), and 8.1% (141/1,735) of patients in the low-, intermediate-, and high-tertiles of 90-day predicted death, respectively. Ninety-day death was between 3.2- and 4.8-fold higher in patients with VT/VF compared with those without it in the 3 risk groups (low risk 1.6% vs 0.5%, intermediate risk 5.7% vs1.2%, high risk 33.6% vs 7.7%). Both early (during cardiac catheterization) and late VT/VF (after cardiac catheterization) were associated with high risk of death regardless of baseline risk category.

The incidence of VT/VF and mortality increased as patients' baseline risk increased, and VT/VF remained an important prognostic marker for the increased risk of clinical adverse events and 90-day mortality irrespective of underlying baseline risk in patients undergoing primary PCI. Thus, even in otherwise low-risk patients, occurrence of VT/VF helps to further identify higher risk cohort that may warrant closer monitoring.