Heart Disease

Both low- and high-risk patients fare better when they undergo cardiovascular procedures at high-volume hospitals

Some argue for referring only high-risk cardiovascular patients to high-volume hospitals, which often have more experience and better patient outcomes, in order to transfer fewer patients and put less strain on financially less viable small-volume hospitals. However, a recent study of over 800,000 elderly Medicare patients treated at all U.S. hospitals performing cardiovascular surgery casts doubt on this approach. In this study, both low- and high-risk patients fared better when treated in high-volume hospitals.

In the study, which was supported by the Agency for Healthcare Research and Quality (HS10141), John D. Birkmeyer, M.D., of Dartmouth Medical School, and his colleagues used the national Medicare database (from 1994 to 1999) to study operative mortality in elderly patients undergoing four cardiovascular procedures: coronary artery bypass graft (CABG) surgery, aortic valve replacement (AVR), mitral valve replacement (MVR), and abdominal aortic aneurysm repair (AAAR). They defined high-risk patients as those in the highest 25th percentile of predicted risk of death based on other coexisting illnesses, previous heart attack, and other risk indicators. They defined low-risk patients as those in the lowest 75th percentile of predicted risk of death.

The researchers compared operative deaths among patients undergoing surgery at very-high volume hospitals (VHVH, highest 20th percentile of procedure volume) and very-low volume hospitals (VLVH, lowest 20th percentile of procedure volume). Operative mortality rates for both low- and high-risk patients were 25 to 50 percent lower at high-volume hospitals. For example, 4.8 percent of low-risk CABG patients died at VLVH versus 3.8 percent at VHVH, while 9.1 percent of high-risk CABG patients died at VLVH versus 7.3 percent at VHVH. The relative risk (RR) of death between VHVH and VLVH was nearly equal for high-risk patients and low-risk patients for all procedures (CABG, 0.78 vs. 0.77; AVR, 0.73 vs. 0.76; MVR, 0.73 vs. 0.74; and AAAR, 0.51 vs. 0.54).

See "Should volume standards for cardiovascular surgery focus only on high-risk patients?" by Philip P. Goodney, M.D., F.L. Lucas, Ph.D., and Dr. Birkmeyer, in the January 28, 2003, Circulation 107, pp. 384-387.

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