Balloon Counterpulsation After Acute MI Angioplasty
August 1, 1997 3 minutes read
Balloon Counterpulsation After Acute MI Angioplasty
ABSTRACT & COMMENTARY
Synopsis: A strategy of prophylactic intra-aortic balloon pump counterpulsation in high-risk post primary angioplasty acute MI patients did not result in improved outcomes.
Source: Stone GW, et al. J Am Coll Cardiol 1997;29: 1459-1467.
Despite the positive reports on the successes of primary angioplasty for acute myocardial infarction (MI), adverse outcomes are still a problem, and observational studies have suggested that intra-aortic balloon pump counterpulsation (IABP) prophylactically after primary angioplasty for MI may improve outcomes. This hypothesis was tested in 1100 patients in the Primary Angioplasty in MI study (PAMI-II). After angioplasty patients were divided into a high-risk group (> 70 years old, three-vessel disease, ejection fraction < 45%, vein graft occlusion or suboptimal result) or a low-risk group. The high-risk patients were randomized to 48 hours of IABP (211) or conventional therapy (226). The primary end point was in-hospital death, reinfarction, infarct artery occlusion, stroke, heart failure, or hypotension. IABP was successfully deployed in 86% of those randomized to receive it, and the mean duration of counterpulsation was 48 hours. Among the conventional treatment group, 12% were treated with IABP because of hemodynamic instability, persistent ischemia, or coronary artery complications. There were no differences in the primary end point between the two groups. Assessment of specific events showed a higher stroke rate in the IABP patients (2.4%) vs. conventional therapy (7.0%, P = 0.03). Secondary end point analysis showed less persistent angina in the IABP group (3% vs. 8%, P = 0.05) and less repeat non-protocol catheterization (8% vs. 13%, P = 0.05). IABP resulted in more hemorrhagic complications because of access site bleeding, but there was no difference in major bleeding or vascular complications. Also, preservation of left ventricular function at hospital discharge and six weeks later was not different between the two groups. Stone and colleagues conclude that a strategy of prophylactic IABP in high-risk post primary angioplasty acute MI patients did not result in improved outcomes.
COMMENT BY MICHAEL H. CRAWFORD
Although hospital days were no different in the two groups, the lack of benefit of IABP for 48 hours will save hospital costs associated with IABP use such as prolonged intensive care unit stays. Thus, these negative results are welcomed by our hospital administrators, as they should be. This is another example of how a high- technology (read cost) approach does not always result in improved outcomes. It also highlights the value of prospective randomized trials.
The major reason for the negative results compared to previously reported experience was the low mortality rate in the conventional therapy arm (3%). These results are reminiscent of the recent report from the VANQWISH trial, which showed an incredibly low mortality in the conservative strategy (Clin Cardiol Alert 1997;16:47-48). The point is that in the 34 centers involved in this study, primary angioplasty for acute MI was very successful. The reocclusion rate was 6% vs. up to 20% in other studies, yet these were high-risk patients. Although superior operators may be a factor, improved angioplasty techniques, new adjuvant drugs, and the general lack of prior thrombolytic therapy probably contributed to these excellent results.
The study confirms experimental observations that IABP increases coronary blood flow since ischemic events were reduced by IABP. Unfortunately, stroke rates were increased somewhat, and there were more bleeding complications. Despite these complications, IABP still has a role in those with ongoing ischemia and hemodynamic instability. It may also be indicated in patients with known coronary dissection or prophylactically for patients following rescue angioplasty where reocclusion rates are higher. However, as routine prophylactic therapy for primary angioplasty, it is of no overall benefit and may be harmful.
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