The Primary Angioplasty in Myocardial Infarction Study - PAMI-stent
Primary stenting vs. PTCA for angiographic and clical outcomes in acute MI.
To evaluate angiographic and clinical outcomes following heparin-coated Palmaz-Schatz stents for acute MI.
Patients Screened: Not given
Patients Enrolled: 1,458
Acute MI within 12 hours of symptom onset
Use of thrombolysis
Contraindication to aspirin, ticlopidine, or heparin
Combined endpoint of death, recurrent MI, disabling stroke, and ischemia-driven target vessel revascularization at 6 months
Heparin-coated Palmaz-Schatz stent or PTCA in acute MI.
Following heparin-coated stent placement, operators were instructed to discontinue heparin immediately, although about one-third of this group still received post-procedural heparin, often due to the presence of a large anterior MI, atrial fibrillation, or a subtotal occlusion in another vessel. In the primary PTCA group, heparin was recommended for 1 or 2 days post-procedure.
About 98% of patients randomized to stent placement received a stent. In the remaining patients, there was either an inability to deploy the stent or a proper-sized stent was unavailable. Sixty-seven PTCA patients (15%) ultimately crossed over to stenting. Procedural success was more than 99% for both groups.
Acute angiographic results showed significantly greater residual stenosis in the primary PTCA group compared to primary stenting (24.8% vs. 11%, p=0.0001). This difference remained at 6-month follow-up with 20% of stent patients showing >50% stenosis versus 32% among patients randomized to primary PTCA. Both acute and 6-month angiographic data showed a greater minimal lumen diameter in the stent group.
Target vessel revascularization (TVR) at 6 months was more likely in the PTCA group (21.4% vs. 12.8%, p<0.001). Patients undergoing primary stenting also showed significantly reduced post-procedural anticoagulant use, as well as reduced angiographic restenosis and reocclusion.
Overall, stenting was associated with a reduction in the combined endpoint of death, recurrent MI, disabling stroke, and ischemia-driven TVR at 6 months (12.4% vs. 20.1%, p<0.01). This difference appeared to be related almost entirely to a reduction in ischemia-driven TVR.
The results of this 12-nation, 62-center study, should be widely applicable. The rates of reocclusion of the infarct vessel following stent implantation are now down in the range of 4% as opposed to about 13% with primary angioplasty. Reocclusion rates after thrombolysis alone are significantly higher. Stenting improved angiographic parameters at six months, with a reduction in the composite clinical endpoint at six months. The trial results reflect an unexpectedly low rate of death and myocardial infarction in the control group; this is partly secondary to the crossover rate to bailout stenting and possibly also due to the differences in post-procedure heparin regimens used in the two groups. Differences in revascularization rates may be confounded by the impracticality of blinding operators to patients' interventions. Nonetheless, the PAMI stent trial remains the largest study of primary stenting to date.
1. Circulation 1998;98(Suppl I):I-22.
Keywords: Myocardial Infarction, Stroke, Follow-Up Studies, Heparin, Constriction, Pathologic, Angioplasty, Balloon, Coronary, Stents
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