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LITTLE FALLS, N.J., May 5 -- Patients with ST-elevation myocardial infarction who develop ventricular tachycardia or fibrillation during or after a percutaneous coronary intervention (PCI) have worsened clinical outcomes, a retrospective study showed.

Patients who had sustained ventricular tachycardia or fibrillation (VT/VF) at any point after presentation were 3.63 times more likely to die within 90 days than those who did not have an arrhythmia (HR 3.63, 95% CI 2.59 to 5.09), according to Rajendra Mehta, M.D., of Duke Clinical Research Institute, and colleagues.

Risk was increased regardless of when the arrhythmia occurred, but outcomes were substantially poorer for those who developed one post-PCI, the researchers reported in the May 6 issue of the Journal of the American Medical Association.

They also found that patients who had a TIMI flow grade of 3 and complete ST resolution following PCI had a very low risk of developing VT/VF, which suggests that close monitoring may not be necessary for patients with complete reperfusion. They said these patients may be considered for early discharge.

"Because currently the majority of patients with STEMI worldwide are routinely monitored for longer than 72 hours, our findings have the potential to decrease resource use without compromising patient safety when a risk-based strategy of monitoring or early discharge is followed," they said.

However, the findings should be confirmed in future studies, they noted.

Dr. Mehta and colleagues looked at data from 5,745 STEMI patients undergoing PCI at 296 hospitals in 17 countries who were included in the

Assessment of Pexelizumab in Acute Myocardial Infarction (APEX AMI) trial.

VT/VF occurred in 5.7% of the patients; 64% of the arrhythmias occurred before the end of catheterization, and 90% occurred within 48 hours of presentation.

At 90 days, the rate of death among those with VT/VF at any time was higher than those who did not have one of these arrhythmias (23.2% versus 3.6%).

The mortality rate was worse for those who developed VT/VF after PCI (33.3%; HR 5.59, 95% CI 3.71 to 8.43) than for those who developed the irregular rhythm before the end of the catheterization (17.2%; HR 2.34, 95% CI 1.44 to 3.80).

Other clinical outcomes, such as cardiogenic shock (PP=0.01), recurrent MI (P=0.01), and stroke (P=0.008) were significantly associated with any VT/VF.

At 14 days, bleeding and renal failure were significantly more likely in patients who developed VT/VF (P
Factors that were associated with both early and late VT/VF included lower systolic blood pressure, higher heart rate, higher total baseline ST deviations, and a preprocedural TIMI flow grade of 0.

Factors associated with early VT/VF only were higher body weight, inferior infarction, lower creatinine clearance, a Killip class greater than I, and shorter time from symptom onset to randomization.

Those related to late VT/VF were a lack of beta-blockers on admission, ST resolution less than 70%, and a postprocedural TIMI flow grade of less than 3.

"These data support the prognostic importance of (any, early, or late) VT/VF as an independent and incremental risk marker, although this does not prove a cause-and-effect relationship," the researchers said.

Patients without complete reperfusion "may require close continuous surveillance in the intensive care or telemetry unit," they said.

They acknowledged some limitations of the study, including its retrospective design, some missing information, possible selection bias resulting from data derived from a randomized trial, and the inability to validate the findings using other data sets.

The APEX AMI trial was jointly funded by Procter & Gamble Pharmaceuticals and Alexion Pharmaceuticals. One of the study authors reported receiving modest honoraria from Procter & Gamble Pharmaceuticals for serving on the APEX AMI steering committee. Two of the other authors reported receiving significant research grants from Alexion Pharmaceuticals and Procter & Gamble Pharmaceuticals.

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