The Primary Angioplasty in Myocardial Infarction Study - PAMI

Description:

Primary angioplasty for death or recurrent ischemia in acute MI.

Hypothesis:

The problems of thrombolytic therapy for acute myocardial infarction (bleeding complications, the impossibility of reperfusing all occluded coronary arteries, recurrent myocardial ischemia, and the relatively small number of patients who are appropriate candidates for this therapy) could be overcome by the use of immediate percutaneous transluminal coronary angioplasty (PTCA), without previous thrombolytic therapy.

Study Design

Study Design:

Patients Screened: Not given
Patients Enrolled: 395
Mean Follow Up: 6 months
Mean Patient Age: 60
Female: 27
Mean Ejection Fraction: 51 ±14 to 53 ±13

Patient Populations:

Any age who presented within 12 hours of the onset of ischemic chest pain if ST-segment elevation of at least 1mm was present in two or more contiguous electrocardiographic leads.

Exclusions:

Inability to provide informed consent
Dementia
Complete left bundle branch block
Cardiogenic shock
Higher-than-normal risk of bleeding

Primary Endpoints:

Recurrent ischemia or death

Drug/Procedures Used:

PTCA, or recombinant tissue plasminogen activator (rt-PA), 100mg IV or 1.25 mg/kg over 3 hours for patients weighing <65kg.

Concomitant Medications:

Before randomization: oxygen, IV nitroglycerin, oral aspirin, 325 mg, and a 10,000 U IV bolus of heparin. Patients assigned to PTCA: heparin, 5000-10,000 U IV. All patients received IV heparin for 3-5 days to achieve a partial thromboplastin time 1.5-2 times the control, oral aspirin, 325 mg/day, and oral diltiazem, 30-60 mg qid. Beta-blockers and IV lidocaine at the discretion of the investigator.

Principal Findings:

Among the patients randomly assigned to PTCA, 90 percent underwent the procedure; the success rate was 97 percent, and no patient required emergency coronary-artery bypass surgery. The in-hospital mortality rates in the rt-PA and PTCA groups were 6.5 and 2.6 percent, respectively (P = 0.06).

In a post hoc analysis, the mortality rates in the subgroups classified as "not low risk" were 10.4 and 2.0 percent, respectively (P = 0.01). Reinfarction or death in the hospital occurred in 12.0 percent of the patients treated with rt-PA and 5.1 percent of those treated with PTCA (P = 0.02).

Intracranial bleeding occurred more frequently among patients who received rt-PA than among those who underwent PTCA (2.0 vs. 0 percent, P = 0.05).

The mean (± SD) ejection fractions at rest (53 (±13) vs. 53 (±13) percent) and during exercise (56 (±13) vs. 56 (±14) percent) were similar in the rt-PA and PTCA groups at six weeks.

By six months, reinfarction or death had occurred in 32 patients who received rt-PA (16.8 percent) and 16 treated with PTCA (8.5 percent, P = 0.02).

The benefits of primary angioplasty were maintained at 2-year follow-up: lower incidence of death or MI (14.9% vs. 23%; p = 0.034), less recurrent ischemia (36.4% vs. 48%; p = 0.026), lower reintervention rates (27.2% vs. 46.5%; p < 0.0001), and lower rehospitalization rates (58.5% vs. 69.0%; p = 0.035) (see Circulation 1999;33:640).

Total mean (+/- SD) hospital charges were $3,436 lower per patient with PTCA than with t-PA ($23,468 +/- $13,410 vs. $26,904 +/- $18,246, p = 0.04), primarily due to the reduction in adverse in-hospital outcomes. Total charges, although favoring PTCA, were not significantly different ($27,653 +/- $13,709 vs. $30,227 +/- 18,903, p = 0.21).

Interpretation:

As compared with rt-PA therapy for acute myocardial infarction, immediate PTCA reduced the combined occurrence of nonfatal reinfarction or death, was associated with a lower rate of intracranial hemorrhage, and resulted in similar left ventricular systolic function. Compared with t-PA, reperfusion by primary PTCA improves clinical outcomes with similar or reduced costs. An impressively short randomization to balloon time was observed (average 60 minutes vs. 42 minutes for door to thrombolysis). In clinical practice, less than a third of patients have a door to balloon time of under 90 minutes, and as a result, the benefits observed here may not be observed in community practice. At 6 months, the PTCA benefit persisted: death or reinfarction in 8.2% vs. 17.0% (p = 0.02). In the subsequent GUSTO 2 trial, the difference in outcomes between primary PTCA and thrombolysis were no longer significant by 6 months. The accompanying editorial asserts that high-risk patients are most likely to gain the most benefit from immediate PTCA (e.g., >75 years of age, anterior MI, cardiogenic shock). The benefit among this same group of high risk patients was not observed in the subsequent GUSTO IIB study. The editorial also points out that PTCA was available in only 18% of hospitals (even fewer with emergency and/or CABG capability). This trial was conducted before the availability of stents, glycoprotein 2b3a inhibitors, fibrin selective lytic agents. Current trials are assessing the benefit of combining angioplasty and pharmacologic therapy in trials of "facilitated" PCI.

References:

1. N Engl J Med 1993;328:673-79. Final results
2. J Am Coll Cardiol 1995;25:370-7. Predictors of outcome
3. J Am Coll Cardiol 1997;29:901-7. Cost-effectiveness

Clinical Topics: Dyslipidemia, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Lipid Metabolism, Acute Heart Failure

Keywords: Shock, Cardiogenic, Thrombolytic Therapy, Myocardial Infarction, Intracranial Hemorrhages, Follow-Up Studies, Chest Pain, Coronary Disease, Fibrin, Tissue Plasminogen Activator, Angioplasty, Balloon, Coronary, Stents


< Back to Listings