Principal Findings:

Therapeutic decision making in critically ill patients requires both prompt and comprehensive analysis of available information. Data derived from randomized clinical trials provide a powerful tool for risk assessment in the setting of acute myocardial infarction (MI); however, timely and appropriate use of existing therapies and resources are the key determinants of outcome among high-risk patients.

Demographic, procedural, and outcome data from MI patients were collected at 1073 U.S. hospitals collaborating in the National Registry of MI (NRMI 2). Patients were classified on hospital arrival as either "low risk" or "high risk" according to a modified Thrombolysis in Myocardial Infarction II Risk Scale based on predetermined demographic, electrocardiographic, and clinical features.

Among the 170,143 patients enrolled, 67.5% were classified as low risk and 32.5% as high risk for in-hospital death, recurrent ischemia, recurrent MI, congestive heart failure, and stroke. Using a composite outcome measure, a greater proportion of patients classified as high risk sustained in-hospital adverse events. By multivariate analysis, age >70 years, prior MI, Killip class >1, anterior infarction, and the combination of hypotension and tachycardia were independent predictions of poor outcome. High-risk patients with ST-segment elevation were treated with thrombolytics (47.5%) or alternative forms of reperfusion therapy (9.3%) within 62 minutes and 226 minutes of hospital arrival, respectively. High-risk patients offered reperfusion therapy were also more likely to receive aspirin, beta-blockers and angiotensin-converting enzyme inhibitors within 24 hours of infarction (all p < 0.0001), survive their event (8.4% versus 21.4% p < 0.0001), and leave the hospital sooner than those not reperfused.

One substudy sought to determine whether cases of acute myocardial infarction (AMI) varied by season.

The number of cases of AMI reported to NRMI-2 by season during the period July 1, 1994 to July 31, 1996 was analyzed. Data were normalized so that seasonal occurrence of AMI was reported according to a standard 90-day length.

A total of 259,891 cases were analyzed during the study period. Approximately 53% more cases were reported in winter than during summer. The same seasonal pattern was seen in men and women, in different age groups and in 9 of 10 geographic areas. In-hospital case fatality rates for AMI also followed a seasonal pattern, with a peak of 9% in winter.

Another substudy compared outcomes after primary percutaneous transluminal coronary angioplasty (PTCA) or thrombolytic therapy for acute myocardial infarction (MI).

From June 1, 1994, through October 31, 1995, 4,939 patients underwent primary PTCA within 12 h of symptom onset, and 24,705 patients received alteplase (rt-PA). When lytic-ineligible patients and patients presenting in cardiogenic shock were excluded, baseline characteristics were similar. The median time from presentation to initiation of rt-PA in the thrombolytic group was 42 min; the median time to first balloon inflation in the primary PTCA group was 111 min (p < 0.0001). In-hospital mortality was higher in patients in shock after rt-PA than after PTCA (52% vs. 32%, p < 0.0001). In-hospital mortality was the same in lytic-eligible patients not in shock: 5.4% after rt-PA and 5.2% after PTCA. The stroke rate was higher after lytic therapy (1.6% vs. 0.7% after PTCA, p < 0.0001), but the combined end point of death and nonfatal stroke was not significantly different between the two groups (6.2% after rt-PA and 5.6% after PTCA). There was no difference in the rate of reinfarction (2.9% after rt-PA and 2.5% after PTCA).

These findings suggest that for lytic-eligible patients not in shock, PTCA and rt-PA are comparable methods of reperfusion.