Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Partial ileal bypass reduced coronary artery disease morbidity and cholesterol levels after myocardial infarction

ACP J Club. 1991 Jan-Feb;114:1. doi:10.7326/ACPJC-1991-114-1-001


Source Citation

Buchwald H, Varco RL, Matts JP, et al., and the POSCH Group. Effect of partial ileal bypass surgery on mortality and morbidity from coronary heart disease in patients with hypercholesterolemia. Report of the Program on the Surgical Control of the Hyperlipidemias (POSCH). N Engl J Med. 1990;323:946-55.


Abstract

Objective

To determine whether partial ileal bypass improves cholesterol profiles and decreases overall mortality and morbidity caused by coronary heart disease in patients surviving a first myocardial infarction compared with diet instruction only.

Design

Randomized, single-blind, controlled trial with a mean follow-up of 9.7 years.

Setting

3 university hospitals and 1 private hospital in the United States.

Patients

Patients between 30 and 64 years old were included if they had survived 1 myocardial infarction between 6 and 60 months earlier. Patients were excluded for hypertension, a body weight over 40% above the ideal weight, diabetes, or certain predefined impairments of the cardiovascular or other major organ systems. No patients were lost to follow-up.

Intervention

Patients were assigned to diet instruction only (n = 417) or to diet instruction plus partial ileal bypass (n = 421).

Main outcome measures

Death from any cause, recurrent myocardial infarction, episodes of unstable angina, other atherosclerotic events, and sequential arteriographic changes.

Main results

Total cholesterol levels and low-density lipoprotein (LDL) cholesterol levels were lower in the surgery group throughout the trial (P < 0.001) and high-density lipoprotein (HDL) cholesterol levels were higher (P = 0.02). Overall mortality was not reduced in the surgery group compared with the diet instruction alone group (12% vs 15%, P = 0.16) {absolute difference 3%, 95% CI -1% to 8%}* but there were fewer deaths among patients with an ejection fraction ≥ 50% (P = 0.02). 82 patients (20%) in the surgery group had a fatal or nonfatal coronary heart disease (CHD) event compared with 125 patients (30%) in the control group. {This absolute risk reduction (ARR) of 10% means that 10 patients would need to be treated (NNT) with partial ileal bypass (rather than diet only) to prevent 1 additional patient from having a fatal or nonfatal CHD event, 95% CI 6 to 21; the relative risk reduction (RRR) was 35%, CI 17% to 49%}*. During follow-up 52 patients (12%) in the surgery group had coronary-artery bypass grafting compared with 132 patients (32%) in the control group (P < 0.001) {ARR 20%; NNT 5, CI 4 to 7; RRR 62%, CI 50% to 72%}*. Disease progression was slower in the surgery group, judged by coronary arteriograms at baseline and follow-up (P < 0.001). The principal side effect of partial ileal bypass was diarrhea (3 bowel movements/d in the surgery group vs 1.5 bowel movements/d in the control group, P < 0.001); the incidence of kidney stones, gallstones, and symptoms of bowel obstruction were also increased.

Conclusion

Compared with diet alone, partial ileal bypass plus diet instruction induced sustained changes in cholesterol and reduced the morbidity associated with coronary artery disease in patients surviving a single myocardial infarction.

Sources of funding: The National Heart, Lung, and Blood Institute and a Minnesota State Special Legislative Appropriation.

Address for article reprint: Dr. H. Buchwald, Box 290 UMHC, University of Minnesota, Minneapolis, MN 55455, USA.

*Numbers calculated from data in article.


Commentary

This trial was done in mainly hypercholesterolemic, middle-aged, white men who had had a previous myocardial infarction. For this group, the results showed that surgery had a significant benefit for various morbid outcomes and favorable trends for mortality. Before partial ileal bypass surgery can, however, be added to the ever-growing array of pharmacologic and nonpharmacologic approaches to the prevention and management of coronary heart disease, additional questions must be answered. The main question concerns the cost-benefit ratio of partial ileal bypass compared with those of other, newer treatments, including lipid-lowering medications. The cost-benefit question is particularly important considering the many adverse effects of partial ileal bypass including disturbances of gastrointestinal function, gallstones, and kidney stones.

Robert J. Goldberg, PhD
University of Massachusetts Medical SchoolWorcester, Massachusetts, USA


Author's Response

The commentator seems to be threatened by an effective surgical technique in the field of lipid intervention. The impact of POSCH, however, resides in the marked lipid changes achieved and in their overwhelming effects on clinical and arteriographic end points. Truly, the study should not be debated with respect to the conclusive evidence provided to end the "cholesterol controversy." Partial ileal bypass, first done in 1963, was confirmed as a clinical intervention long before POSCH. Perhaps future trials should be done to adjudicate between surgical and drug therapy.

[A 5-year follow-up report has just been submitted for publication (Nov, 1996). The results of this update are an affirmation and extend the 1990 findings.]

H. Buchwald, MD