PCI: Better Late than Never!

By: Andrew Perron, MD, FACEP, FACSM, Residency Program Director, Department of Emergency Medicine, Maine Medical Center, Portland, ME Dr. Perron reports no relationships with companies having ties to the field of study covered by this CME program.

Source: Schomig A, et al. Mechanical reperfusion in patients with acute myocardial infarction presenting more than 12 hours from symptom onset. JAMA 2005;293:2865-2872.

Percutaneous coronary intervention (PCI) has developed into the clear choice as the reperfusion strategy in acute myocardial infarction (MI) when weighed against fibrinolysis. When used within 12 hours of symptom onset, PCI has demonstrated increased myocardial salvage, preservation of left ventricular function, and overall improved survival as compared with intravenous fibrinolytic strategies. Further, studies that looked at intravenous fibrinolysis beyond 12 hours from symptom onset have shown no benefit to this modality; in fact, results showed a trend toward harm. What generally is unknown is whether there is any benefit to a late PCI reperfusion strategy in the subset of acute MI patients presenting more than 12 hours after symptom onset. Observational studies have hinted that there may be benefit, but prospective data are lacking. These late presenters (i.e., patients presenting more than 12 hours from symptom onset) have been reported to constitute between 8% and 32% of all patients presenting with acute MI.

The purpose of this prospective, open-label, randomized, controlled study carried out in Italy, Germany, and Austria was to determine if there was benefit to PCI performed for acute MI in patients who presented more than 12 hours after symptom onset. As fibrinolysis was not an option for those patients not randomized to receive PCI, these patients were randomized to conventional conservative treatment. The primary outcome measure was prospectively defined as left ventricular (LV) infarct size. Secondary outcome measures included death, recurrent MI, or stroke at 30 days.

All patients received standard care including aspirin and an initial dose of glycoprotein IIb/IIIa inhibitor, and heparin. All patients also received beta-blockers, as well as angiotensin converting enzyme inhibitors and statins as indicated. All patients were admitted to telemetry for at least 48 hours. Patients in the control group continued taking heparin for 24 hours, and ultimately had a symptom-limited stress test prior to discharge. Patients assigned to PCI were taken to the cardiac catheterization laboratory immediately. If indicated, these patients had angioplasty and/or stenting; these patients received abciximab following their procedures.

The study enrolled 365 patients between May 2001 and December 2004; 182 were randomized to the PCI arm and 183 randomized to the control group. The results showed significantly smaller infarct size in the PCI group (8%, IQR 2%-16%) as compared with controls (13%, IQR 3%-27%). There was a trend toward improved secondary outcome measures in the PCI group (4.4%) as compared with controls (6.6%), but this did not reach statistical significance (relative risk 0.67, p = 0.37).

The authors of the study concluded that PCI— even when used at 12 or more hours after onset of symptoms—results in smaller infarct size in acute MI patients.

Commentary

The fundamental question being asked by this multi-center, multinational trial is: Regarding PCI for AMI, is late better than never? The answer would seem to be a cautious "yes" at least for infarct size. Now the astute clinician likely (and rightly) will ask first whether the 5% reduction in LV infarct size is clinically significant. The answer again seems to be yes, based upon other studies. Other authors have reported that even a 3% difference in infarct size results in reduced 30-day mortality.1

The reader might then question why there was not a significant difference in 30-day composite outcomes in this study. While the relative risk of reaching one of the three composite endpoints was reduced by 33% in the treatment arm, this factor did not reach statistical significance. The authors (and an accompanying editorial)2 pointed out that this study was never powered to find such a difference. Far more patients would need to be enrolled to demonstrate (or disprove) this.

I don’t think that this relatively small study is enough to make PCI an absolute requirement (i.e., a Class I indication) for all comers with acute MI regardless of time from symptom onset. I do think it should allow the clinician to feel comfortable pushing the interventional cardiologist toward doing the procedure when the only limitation identified is time from symptom onset.

References

1. Chareonthaitawee P, et al. CORE Investigators. The impact of time to fibrinolytic treatment on outcome in patients with acute myocardial infarction. Heart 2000;84:142-148.

2. Gibbons RJ, et al. Acute PCI for ST-segment elevation myocardial infarction. Is later better than never? JAMA 2005;293:2930-2932.