Thrombolysis and Angioplasty in Myocardial Infarction - VI study group - TAMI-6

Description:

Late reperfusion therapy for acute myocardial infarction.

Hypothesis:

Either thrombolytic therapy or percutaneous transluminal angioplasty (PTCA) or both may achieve infarct vessel recanalization in the majority of late-entry patients.

Study Design

Study Design:

Patients Screened: Not given
Patients Enrolled: 197
Mean Follow Up: 6 months
Mean Patient Age: 57
Female: 27

Patient Populations:

Acute myocardial infarction more than 6 but less than 24 hours after the onset of symptoms
ECG ST-segment elevation of 1 mm or more in two or more contiguous leads
Second randomization to PTCA or no PTCA: patients with infarct-related occluded arteries

Exclusions:

>75 years of age
Chest pain relieved by nitroglycerin
History of stroke or recent injury or trauma
Predisposition to bleeding
Previous Q-wave infarction in the distribution of the infarct-related artery
Blood pressure greater than 180 mmHg by two separate measurements
Second randomization to PTCA or no PTCA: stenosis in the left main coronary artery of more than 50% or its equivalent (>75% lesions in the proximal left circumflex and left anterior descending arteries); severe, diffuse, multilesional infarct vessel disease; a small infarct vessel or branch judged to be insignificant; an unidentifiable infarct vessel

Primary Endpoints:

Infarct vessel patency at 6 to 24 hours after the administration of the study drug.

Secondary Endpoints:

First randomization to thrombolysis or placebo: six-point difference in ejection fraction by gated cardiac blood pool scintigraphy; second randomization to PTCA or no PTCA: nine-point difference in ejection fraction by gated cardiac blood pool scintigraphy.

Drug/Procedures Used:

t-PA, 1.0 mg/kg body wt in the first hour with 10% administered as a bolus and a maximum of 80 mg (In the subsequent hour, 20 mg was given such that the maximum total dose was 100 mg.); heparin, 5,000 U bolus at 120 minutes after the study medication was initiated with infusion maintained at 1,000 U/hour and adjusted to keep the partial thromboplastin time at 1.5 to 2 times the control level for at least 48 hours

Concomitant Medications:

Oral aspirin, 325 mg/day; beta-blockers; nitrates; angiotensin-converting enzyme inhibitors; (calcium channel blockers were not administered unless specifically required to treat myocardial ischemia, hypertension, or supraventricular arrhythmias)

Principal Findings:

Ventricular function and cavity size were reassessed at 1 month by gated blood pool scintigraphy and at 6 months by repeat cardiac catheterization.

The primary end point, infarct vessel patency, was 65% for plasminogen activator patients compared with 27% in the placebo group (p less than 0.0001).

There were no differences between these groups in ejection fraction or infarct zone regional wall motion at 1 or 6 months. At 6 months, infarct vessel patency was 59% in both groups. In the placebo group, there was a significant increase in end-diastolic volume from acute phase of 127 ml to 159 ml at 6-month follow-up (p = 0.006) but no increase in cavity size for the plasminogen activator group patients.

Coronary angioplasty was associated with an initial 81% recanalization success and improved ventricular function at 1 month, but by late follow-up no advantage could be demonstrated for this procedure, and there was a 38% spontaneous recanalization rate in the patients assigned to no angioplasty.

Interpretation:

The study demonstrates that it is possible to achieve infarct vessel recanalization in the majority of late-entry patients with either thrombolytic therapy or angioplasty. Thrombolytic intervention had a favorable effect on prevention of cavity dilatation and left ventricular remodeling, but there are no late benefits on systolic function after thrombolysis or coronary angioplasty. The conclusions concerning overall potential benefit of applying late reperfusion therapy will require data from large-scale trials designed to assess mortality reduction.

References:

1. Circulation 1992;85:2090-99. Final results

Clinical Topics: Anticoagulation Management, Dyslipidemia, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Lipid Metabolism, Novel Agents, Interventions and Imaging, Angiography, Nuclear Imaging

Keywords: Thrombolytic Therapy, Myocardial Infarction, Follow-Up Studies, Gated Blood-Pool Imaging, Cardiac Catheterization, Heparin, Dilatation, Fibrinolytic Agents, Electrocardiography, Angioplasty, Balloon, Coronary, Plasminogen Activators, Plasminogen, Ventricular Remodeling, Partial Thromboplastin Time, Tissue Plasminogen Activator


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