Importance of Performing Primary Angioplasty Early
Abstract & commentary
Synopsis: Time to treatment with PCI is a critical determinant of mortality with primary PCI therapy of AMI.
Source: Berger PB, et al. Circulation 1999;100:14-20.
Although primary angioplasty has been shown to result in TIMI-3 flow more often than thrombolytic therapy, the relationship between clinical outcomes and the speed of achievement of reperfusion has not been established. Thus, Berger and colleagues evaluated data from the GUSTO-IIb trial to determine the relationship between the time required to perform primary angioplasty and early clinical outcome. The direct percutaneous intervention (PCI) substudy of GUSTO-IIb compared direct PCI to thrombolytic therapy in 57 high-volume, 24-hour-operation hospitals in nine countries. Of the 1138 patients who presented within 12 hours of myocardial infarction (MI) onset, 565 were randomized to PCI and 79% received their first balloon inflation in the culprit artery at a mean time of 76 minutes after study enrollment; the other 19% did not undergo PCI for a variety of reasons (open artery, 36; surgery, 20; early death, 5; other, 32). The primary end point of 30-day mortality was 1.0% for those whose first balloon inflation was less than 60 minutes; 3.7% for 61-75 minutes; 4.0% for 76-90 minutes; 6.4% for more than 90 minutes; and 14.1% for those assigned to PCI who did not get it (P < 0.001). Mean left ventricular ejection fraction was also higher in the group treated within 60 minutes (60% vs 50% for the other groups). TIMI-3 flow was achieved in 73% of all PCI patients, and their mortality was 1.5% vs. 11.7% for those achieving less than TIMI-3 flow. However, in a multivariable logistic regression analysis, time to reperfusion was a significant predictor of mortality and TIMI flow achieved did not add to this relationship. Thus, Berger et al conclude that time to treatment with PCI is a critical determinant of mortality with primary PCI therapy of acute myocardial infarction (AMI).
Comment by Michael H. Crawford, MD
In centers where primary PCI is a feasible treatment for AMI, the use of thrombolytic therapy has almost disappeared. This study emphasizes that the time to achievement of an open artery is just as important with primary PCI as it is with thrombolytic therapy. In fact, if an artery cannot be opened within 90 minutes of hospital arrival, mortality may exceed what can be achieved with thrombolytic therapy. Thus, even in centers capable of performing primary PCI 24 hours a day, 7 days a week, the likely time to achieve an open artery must be considered and there may be situations when thrombolysis is preferable.
One important factor would be the time that the patient has delayed coming to the hospital. In this study, the time from symptoms to enrollment averaged 142-149 minutes for those whose enrollment to first balloon time was less than 90 minutes; those in the more than 90 minute group had a longer prehospital delay (169 minutes) and those not receiving PCI had the longest delay (201 minutes; P < 0.02). Why those presenting later required more time to accomplish PCI is unclear from the study. Perhaps the diagnosis was more challenging in these patients or they were less sick appearing and were treated more leisurely.
The mean time to PCI of 76 minutes in the entire group is longer than in smaller trials such as primary angioplasty in myocardial infarction (60 minutes) but shorter than the U.S. registry experience (120 minutes). Thus, the results should be applicable to many tertiary U.S. centers. Finally, this is a small study by current multicenter trial standards, with only 30 deaths. However, the results are consistent with other data and make sense clinically. Thus, before we completely abandon thrombolytic therapy in tertiary centers, we need to consider likely in-hospital time delays.
The lowest 30-day mortality with primary angioplasty for AMI is achieved when:
a. hospital diagnosis to first balloon inflation is less than 60 minutes.
b. angioplasty is not performed.
c. TIMI-3 flow is achieved.
d. a and c.