The prognosis for patients with an acute myocardial infarction (MI) can be significantly improved with timely interventions that improve coronary blood flow in the infarct-related coronary artery. During the past two decades, published data have indicated that intravenous thrombolytic therapy can restore blood flow in 50 to 70 percent of patients and reduce mortality by an estimated 20 to 30 percent. Primary angioplasty can restore normal blood flow in 80 to 95 percent of patients. These findings have resulted in debate about the long-term efficacy of both treatments. Zijlstra and colleagues conducted a randomized trial that compared intravenous streptokinase therapy to primary angioplasty in the treatment of acute MI.
Enrollment was limited to patients who presented with acute MI symptoms lasting longer than 30 minutes, accompanied by an electrocardiogram showing ST-segment elevation of at least 1 mm in two or more contiguous leads, and who presented within six hours after the onset of symptoms. All patients were initially given aspirin and intravenous heparin. They were then randomly assigned to receive 1.5 million units of intravenous streptokinase or to undergo immediate angioplasty. Global left ventricular ejection fraction was measured in all patients by equilibrium radionuclide ventriculography between day 4 and day 10 post-treatment. In addition, all patients underwent coronary angiography during follow-up to assess patency of the infarct-related artery. Patients were followed for a mean of 5 ± 2 years. Medical costs for the initial hospitalization and all follow-up care were estimated on the basis of days spent in the hospital, diagnostic and therapeutic procedures, and medications.
Of the 395 patients enrolled in the study, 201 received streptokinase and 194 underwent primary angioplasty. The mean age of the participants was approximately 60 years, and 80 percent were men. The infarct-related artery was patent in 90 percent of the patients who underwent angioplasty and in 65 percent of the patients who received streptokinase. The left ventricular ejection fraction was less than 40 percent in 14 percent of the patients who underwent angioplasty compared with 26 percent of the patients given streptokinase.
During the follow-up period, 26 deaths occurred in the angioplasty group and 48 in the streptokinase group. A strong relationship (in quartiles) was observed between the ejection fraction and the incidence of cardiac death. During the first 30 days post-treatment, 19 nonfatal infarctions occurred in the streptokinase group, and only one occurred in the angioplasty group. During long-term follow-up, 56 patients had nonfatal reinfarctions, with 44 of these occurring in the streptokinase group. The combined incidence of death and nonfatal reinfarction was lower in the angioplasty group during the first 30 days and after 30 days of treatment. The streptokinase-treated patients required significantly more warfarin, nitrate and diuretic therapy. During the follow-up period, 74 of the original patients who underwent angioplasty were readmitted to the hospital, with a total of 115 readmissions; 104 patients who received streptokinase treatment were readmitted, for a total of 221 readmissions. The estimated total medical charge per patient still alive at the end of the study was $18,664 in the angioplasty group and $21,772 in the streptokinase group.
The authors conclude from this study that primary angioplasty, as compared with intravenous streptokinase therapy, lowers mortality and reinfarction rates during the first 30 days and during long-term treatment. Data indicate that angioplasty improves patency rate and results in improved left ventricular function, incidence of reinfarction and mortality. It may also represent a more cost-effective approach because of the reduced need for readmissions.