Cardiologists recommend bypass over angioplasty
Bypass is treatment of choice for revascularization
Cutting-edge research shows that diabetic patients with myocardial infarctions (MIs) can be revascularized most successfully through bypass surgery using the left internal mammary artery. Furthermore, American and Belgian researchers discovered that patients undergoing the procedures and using sulfonylureas had significantly worse outcomes than those on metformin.
The study, involving 15,809 patients (9,600 in Leuven, Belgium and 6,209 at the Mid America Heart Institute in Kansas City, MO — 1,938 of them diabetics at baseline) was published in the European Heart Journal in November.
Only slightly more than half (51%) of the patients achieved complete revascularization through angioplasty, but 82% achieved complete success through bypass surgery, according to the study’s lead author James H. O’Keefe, MD, professor of medicine at the University of Missouri in Kansas City and director of preventive cardiology at the Mid America Heart Institute.
In addition, the study shows that the 10-year survival rate for pharmacologically treated patients was better after bypass surgery (60%) than for angioplasty patients (46%). (See box, at left.)
All the U.S. diabetic angioplasty patients involved in the study who used oral agents were using sulfonylureas, while among the Belgian diabetics who had bypass surgery, 248 were using sulfonylureas, 35 metformin, and 11 both drugs. Metformin was not available in the United States at the time of the study and was used by only a small number of the Belgian bypass patients. Troglitazone was not available then in either country.
O’Keefe says, "There’s no question that patients do worse with sulfonylureas after angioplasty. In general, risk-adjusted long-term survival of diabetic patients was worse after angioplasty than after surgery. This was especially true for diabetics treated with oral agents, where the surgical survival advantage was importantly magnified."
He says explanations for the worse outcomes on sulfonylureas are "speculative." A body of evidence beginning decades ago with the University Group Diabetes Program in the 1970s concluded that tolbutamide increased death from cardiovascular disease. O’Keefe concedes that the findings of the University Group study were largely dismissed because there was a lack of a suitable alternative therapy for Type II diabetics at the time.
One theory for the outcomes, according to O’Keefe, is sulfonylureas close down potassium ion channels, prolonging myocardial refractoriness, "possibly predisposing the dysrhythmias and also exacerbating the consequences of myocardial ischemia and infarction by mitigating ischemic preconditioning."
In a current study still in draft form, he further speculates that sulfonylureas may "increase atherogenesis and its complications" regardless of the level of glycemic control because they are vasoconstrictors and they worsen vascular reactivity. "Anybody who has high-risk coronary disease, ischemia, and multivessel involvement should opt for bypass surgery."
O’Keefe’s results take the five-year BARI (Bypass Angioplasty Revascularization Investigation) results to the next level. However, the EAST (Emory Angioplasty vs. Surgery Trial) study showed no difference in survival for diabetics following angioplasty or bypass surgery. "Neither of these studies included comparative outcomes after revascularization in diabetics as a pre-specified end-point, and both studies involved a relatively small number of diabetic patients," he notes.
The BARI-II trial comparing angioplasty and bypass surgery in diabetic patients is currently under way.
Some diabetics, mainly those at high risk, may do as well with angioplasty as with bypass surgery, O’Keefe says, including the very young, who are likely to have discrete disease and the very old, who are at increased risk of perioperative morbidity. He also found the use of the internal mammary artery for grafting to the left anterior descending artery provided a "significant survival benefit" for patients receiving vessel grafts only or angioplasty.
It is important to note that the study took place before metformin and troglitazone were available in the United States and before stent procedures were in general use, says Sanjay Kaul, MD, attending cardiologist at Cedars-Sinai Medical Center in Los Angeles.
Kaul says since intimal hyperplasia or scarring of the arteries is "more luxuriant" in diabetics, angioplasty tends to be less successful than bypass surgery. He says that vein grafts obstruct more easily than arterial grafts, which explains the success rate of the mammary-arterial grafts.
Kaul is an advocate of stenting and says more research needs to be done along these lines. "About 70% of my coronary patients undergo stenting, and the re-stenosis rate is lower [than in angioplasty] at about 50%," Kaul says. "But there is evidence the outcome for diabetic patients is not as great, convincing, or compelling as for non-diabetic patients."
For more information, contact James H. O’Keefe, MD, Professor of Medicine at the University of Missouri in Kansas City and Director of Preventive Cardiology at the Mid America Heart Institute. Telephone: (816) 931-1883.
Diabetic Patient Outcomes: James H. O’Keefe Study
¤ 15,809 total patients in study:
9,600 with bypass surgery in Belgium
6,209 with angioplasty in United States
¤ 1,938 diabetics at baseline (12%):
1,056 with bypass surgery in Belgium (11% of total)
882 with angioplasty in U.S. (14% of total)
¤ Complete revascularization achieved:
Angioplasty: 51%
Bypass: 82%
¤ Drug treatment of diabetic patients:
• Diet only:
Angioplasty: 201 (3%)
Bypass: 475 (5%)
• Oral agents:
Angioplasty: 360 (6%)
Bypass: 294 (3%)
• Insulin:
Angioplasty: 314 (5%)
Bypass: 287 (3%)
¤ 10-year survival rate for patients treated pharmacologically:
Angioplasty: 46%
Bypass: 60%
¤ Risk-adjusted 10-year survival for diabetics treated with oral agents:
Angioplasty: 62%
Bypass: 75%
¤ Risk-adjusted 10-year survival for diabetics treated with diet only:
Angioplasty: 81%
Bypass: 84%
¤ Risk-adjusted 10-year survival for diabetics treated with insulin:
Angioplasty: 64%
Bypass: 63%
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content