Balancing the benefits of primary angioplasty against the benefits of thrombolytic therapy for acute myocardial infarction: the importance of timing.

CONTEXT: A meta-analysis found that primary percutaneous transluminal coronary angioplasty (PTCA) was more effective than thrombolytic therapy in reducing mortality from acute myocardial infarction. However, fewer than 20% of U.S. hospitals have facilities to perform PTCA and many clinicians must choose between immediate thrombolytic therapy and delayed PTCA. COUNT: The number of minutes of PTCA-related delay that would nullify its benefits. CALCULATION: For 10 published randomized trials, we calculated the following: PTCA-related delay = median "door-to-balloon" time--median "door-to-needle" time Survival benefit = 30-day mortality after thrombolytic therapy--30-day mortality after PTCA The relationship between delay and benefit was assessed with linear regression.
RESULTS: The reported PTCA-related delay ranged from 7 to 59 minutes, while the absolute survival benefit ranged from -2.2% (favoring thrombolytic therapy) to 7.4% (favoring PTCA). Across trials, the survival benefit decreased as the PTCA-related delay increased: For each additional 10-minute delay, the benefit was predicted to decrease 1.7% (P < 0.001). Linear regression showed that at a PTCA-related delay of 50 minutes, PTCA and thrombolytic therapy yielded equivalent reductions in mortality.
CONCLUSIONS: In clinical trials with short PTCA-related delays, PTCA produced better outcomes, while trials with longer delays favored thrombolytic therapy. A more precise estimate of the time interval to equipoise between the two therapies needs to be modeled with patient-level data. At experienced cardiac centers, PTCA is probably still preferable, even with delays longer than 50 minutes.