Direct comparison of characteristics, treatment, and outcomes of patients enrolled versus patients not enrolled in a clinical trial at centers participating in the TIMI 9 Trial and TIMI 9 Registry

Abstract

Background: Questions about the generalizability of randomized trial results to clinical practice have arisen because the overall mortality rate is generally lower in trials, potentially because patients who are at lower risk are enrolled. However, little is known about the characteristics of patients included in clinical trials versus those who are not included.

Methods: The Thrombolysis In Myocardial Infarction (TIMI) 9 Registry prospectively evaluated patients with ST-elevation myocardial infarction at 20 hospitals during the TIMI 9 trial, which compared hirudin versus heparin with fibrinolysis. We compared the characteristics, treatment, and outcomes of patients enrolled in TIMI 9B (n = 3002) with other fibrinolytic-eligible patients not enrolled in TIMI 9B (n = 296) and with those not eligible for fibrinolysis by American College of Cardiology/American Heart Association criteria, at the same centers (n = 282), with the latter groups divided by use of reperfusion therapy.

Results: Across the groups, ranging from those in the TIMI 9 trial to those ineligible for fibrinolysis, we observed a gradient of higher-risk baseline characteristics, lower use of reperfusion therapy, and higher mortality rates (P <.001). In addition, comparing fibrinolytic-eligible patients in TIMI 9B versus those not enrolled in the trial, the use of aspirin, beta-blockers, and angiotensin-converting enzyme inhibitors was significantly higher in the TIMI 9B trial. Ineligible patients not treated with reperfusion therapy had much lower rates of use of these medications and the highest inhospital mortality rate (24%, adjusted odds ratio 2.8, P <.0001)

Conclusions: In this prospective registry, patients not enrolled in a clinical trial had higher risk characteristics and worse outcomes; however, they also were treated less frequently with guideline-recommended medications, which may have contributed to their higher mortality rates.