Clinical Studies
A Prospective, Randomized Evaluation of Prophylactic Intraaortic Balloon Counterpulsation in High Risk Patients With Acute Myocardial Infarction Treated With Primary Angioplasty fn1

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Abstract

Objectives. A large, international, multicenter, prospective, randomized trial was performed to determine the role of prophylactic intraaortic balloon pump (IABP) counterpulsation after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI).

Background. Previous studies have suggested that routine IABP use after primary PTCA reduces infarct-related artery reocclusion, augments myocardial recovery and improves clinical outcomes.

Methods. Cardiac catheterization was performed in 1,100 patients within 12 h of onset of AMI at 34 clinical centers. Clinical and angiographic variables were used to stratify patients undergoing primary PTCA into high and low risk groups. High risk patients were then randomized to 36 to 48 h of IABP (n = 211) or traditional care (n = 226). The study had 80% power to detect a reduction in the primary end point from 30% to 20%.

Results. There was no significant difference in the predefined primary combined end point of death, reinfarction, infarct-related artery reocclusion, stroke or new-onset heart failure or sustained hypotension in patients treated with an IABP versus those treated conservatively (28.9% vs. 29.2%, p = 0.95). The IABP strategy conferred modest benefits in reduction of recurrent ischemia (13.3% vs. 19.6%, p = 0.08) and subsequent unscheduled repeat catheterization (7.6% vs. 13.3%, p = 0.05) but did not reduce the rate of infarct-related artery reocclusion (6.7% vs. 5.5%, p = 0.64), reinfarction (6.2% vs. 8.0%, p = 0.46) or mortality (4.3% vs. 3.1%) and was associated with a higher incidence of stroke (2.4% vs. 0%, p = 0.03). IABP use did not result in enhanced myocardial recovery as assessed by paired admission to predischarge and 6-week rest and exercise left ventricular ejection fraction.

Conclusions. In contrast to previous studies, a prophylactic IABP strategy after primary PTCA in hemodynamically stable high risk patients with AMI does not decrease the rates of infarct-related artery reocclusion or reinfarction, promote myocardial recovery or improve overall clinical outcome.

(J Am Coll Cardiol 1997;29:1459–67)

Abbreviations

AMI
acute myocardial infarction
CABG
coronary artery bypass graft surgery
CK-MB
creatine kinase, MB fraction
ECG
electrocardiographic
IABP
intraaortic balloon pump
LVEF
left ventricular ejection fraction
PAMI
Primary Angioplasty in Myocardial Infarction
PTCA
percutaneous transluminal coronary angioplasty
TIMI
Thrombolysis in Myocardial Infarction

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fn1

Funding for this study was provided in part by unrestricted grants from Advanced Cardiovascular Systems, Inc., Santa Clara, California; Mallinkrodt Medical, Inc., Saint Louis, Missouri; Datascope Corporation, Montvale, New Jersey; St. Jude Medical, Chelmsford, Massachusetts; and Siemens Corporation, Iselin, New Jersey.

1

A complete list of participating investigators and institutions for the PAMI-II trial appears in the Appendix A.