Fibrinolysis in Acute MI and Hospital Revascularization Capability

Abstract & Commentary

Source: Mehta RH, et al. Patient outcome after fibrinolytic therapy for acute myocardial infarction at hospitals with and without coronary revascularization capability. J Am Coll Cardiol 2002;40:1034-1040.

In this retrospective study of the GUSTO-1 database, investigators compared clinical outcomes of more than 25,000 patients with acute myocardial infarction (AMI) who were treated with fibrinolytic therapy in U.S. hospitals with and without coronary revascularization capability for percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG).

Study data included 12,279 patients treated at 286 hospitals with coronary revascularization capability, and 13,236 patients treated at 374 hospitals without such capability. Outcome measures included mortality (in-hospital, 30-day, and one-year), as well as other clinical events following AMI (i.e., recurrent ischemia, reinfarction, congestive heart failure [CHF], shock, and stroke).

Data were adjusted for five baseline variables associated with mortality after myocardial infarction (MI), namely age, systolic blood pressure, heart rate, Killip CHF class, and MI location. Baseline characteristics between the two groups were similar, with the exception of a slightly higher incidence of prior angina, infarct, angioplasty, and CABG in patients seen at hospitals with revascularization capability.

The investigators report no difference between the two groups in rates of recurrent ischemia, reinfarction, CHF, shock, or stroke after fibrinolytic therapy for AMI. There was a slightly lower unadjusted 30-day mortality for patients seen at hospitals with revascularization capability as opposed to those without (6.6% vs 7.2% respectively), but this difference became insignificant after adjustment for baseline variables. Moreover, adjusted and unadjusted one-year mortality rates showed no significant differences between the two groups (9.6% vs 9.9% respectively).

Approximately 40% of patients who initially received therapy at hospitals without revascularization were transferred to hospitals with such capability. However, fewer than 10% of these patients were transferred within the first six hours for rescue PTCA. Transferred patients, as well as those who initially received fibrinolytic therapy at hospitals with revascularization capability, were more likely to undergo additional procedures such as pulmonary artery catheterization, temporary pacing, PTCA, and CABG.

The authors conclude that there is no difference in outcome for AMI patients treated with fibrinolytic therapy at hospitals without coronary revascularization capability compared to those hospitals with such capability, provided that transfer is available for angiography and revascularization if needed.

Commentary by Theodore C. Chan, MD, FACEP

In the setting of AMI, studies have shown that hospital volume and experience greatly impact outcome and mortality rates for mechanical reperfusion (PTCA and CABG), but not fibrinolytic reperfusion therapy.1 Similarly, this study reports no outcome difference for AMI patients who receive fibrinolytics at hospitals with and without revascularization capability. The authors suggest that these findings support the concept that as long as access to PTCA or CABG is available, it need not be immediately available to maintain the benefits of fibrinolysis.

There are a number of points to keep in mind regarding this study. First, GUSTO-1 was conducted in the early 1990s. Since that time, new advances have occurred in both pharmacologic reperfusion (the development of newer fibrinolytic agents), and mechanical reperfusion (the use of stents and glycoprotein inhibitors). Second, the two groups were not equivalent at baseline, with a higher percentage of patients with prior diagnosis and treatment of CAD presenting to hospitals with revascularization capability.

Third, this study does not address the ongoing debate regarding the merits of mechanical vs. pharmacologic reperfusion strategies. This study focused on patients who met criteria and received fibrinolytic therapy. The results would not apply to all AMI patients, such as those with cardiogenic shock in whom PCI has been shown to be superior to fibrinolytic therapy.2 Finally, while this study would appear to argue against the notion of regional heart-care centers for initiating fibrinolytic therapy, such centers still would be necessary to provide access to urgent rescue PCI and revascularization if needed.

Dr. Chan, Associate Clinical Professor of Medicine, Emergency Medicine, University of California, San Diego, is on the Editorial Board of Emergency Medicine Alert.

References

1. Canto J, et al. The volume of primary angioplasty procedures and survival after acute myocardial infraction. N Engl J Med 2000;342:1573-1580.

2. Hochman JS, et al. Early revascularization in acute myocardial infarction complicated by cardiogenic shock. N Engl J Med 1999;341:625-634.