Bypass surgery results in better five-year survival than balloon angioplasty and stent procedures

Bypass surgery results in better five-year survival than balloon angioplasty and stent procedures for patients with serious coronary artery disease and additional health conditions such as diabetes, according to a study published in today’s rapid access issue of Circulation: Journal of the American Heart Association.

In a group of patients with multiple clogged coronary arteries and other high-risk characteristics, death rates after five years for those who underwent coronary artery bypass grafting (CABG) were almost half the rate of patients who received percutaneous coronary intervention (PCI).  PCI involves angioplasty or stenting to widen a narrowed blood vessel in the heart.

“The sicker the patient the more bypass surgery helped,” said study author Sorin J. Brener, M.D., assistant professor of medicine and medical director of the Angiography Core Laboratory at the Cleveland Clinic Foundation in Ohio.  “The findings were somewhat surprising.  Even in this era of advanced PCI with stents and glycoprotein IIb/IIIa antiplatelet therapy, bypass surgery saved more lives.”

Glycoprotein (GP) IIb/IIIa inhibitors are antiplatelet drugs administered intravenously to reduce blood clotting.

This is one of the largest studies to compare five-year survival rates in groups of bypass and contemporary PCI patients, most of whom received stents and GP IIb/IIIa inhibitors.  The survival advantage was evident even though patients in the CABG group had considerably higher overall health risks.  The advantage was even greater among those with diabetes and advanced heart failure.

Brener and his colleagues examined survival records for 5,161 patients who underwent bypass surgery and 872 who had PCI at Cleveland Clinic.  Roughly one-half of patients in both groups had diabetes or significant left ventricular dysfunction.  While overall survival rates were similar between the two groups, significant differences emerged as the researchers used propensity analysis, a process whereby individual patient cardiovascular risk characteristics – hypertension, smoking, diabetes and other factors – as well as many other procedural elements are factored into the comparison matrix.

“Mortality rates for patients who underwent surgical bypass were almost half the rate of those treated with angioplasty who had similar cardiovascular risk profiles,” said Brener.  The one- and five-year unadjusted mortality rates were 5 and 16 percent for PCI, and 4 and 14 percent for CABG.  However after propensity analysis adjustment, PCI was associated with a significantly higher death rate across all categories, including patients with left ventricular dysfunction and diabetes.  One of the likely explanations is that bypass grafts helped prevent damage from subsequent artery blockages, he said.

Because patients who undergo bypass surgery at the Cleveland Clinic have mortality rates that are one-third the national average during the initial hospital stay, the results may not as be good in other hospitals, cautioned Brener.

“It is quite clear that our results cannot be generalized to the entire country.  Our in-hospital mortality is extremely low – 1.1 percent compared to 3.3 percent in the database of the Society of Thoracic Surgeons, which includes survival data on some 100,000 cardiovascular surgeries.”

Guidelines for PCI published in June 2001 by the American Heart Association and American College of Cardiology acknowledge that patients with diabetes and multivessel disease have higher survival rates when they undergo an arterial bypass graft instead of balloon angioplasty.   However, they also recognize that PCI technology is continually being modified and refined.

Improvements in the technology used in traditional balloon angioplasty, the development of stents and other devices and the use of such new drugs as glycoprotein IIb/IIIa platelet receptor antagonists have helped improve PCI outcomes.   Currently up to 99 percent of coronary interventions are initially successful.

The major advantage of PCI over bypass surgery is its relative ease of use – no general anesthesia, no surgical opening of the chest and no use of a machine to keep the blood artificially oxygenated.   Repeat PCI can be performed more easily than repeat bypass surgery, and blood flow can be restarted more quickly in emergency situations.

However, the guidelines recommend that physicians and patients weigh PCI’s advantages against its disadvantages, which include reocclusion of some vessels within four to six months and the inability to relieve those that are totally blocked or have extensive disease.