AoS: Decline in CABG volume and post-CABG mortality puzzles researchers

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Study finds in-hospital death rates have improved independent of CABG volume. Source: Wikipedia  

For years, increases in coronary artery bypass grafting (CABG) were accompanied by decreases in in-hospital mortality rates, with the assumption that if CABG volumes decreased, mortality rates would increase. This is not the case, according to a large retrospective study published in the April issue of the Archives of Surgery.

Rocco Ricciardi, MD, MPH, of the University of Minnesota in Minneapolis, and colleagues examined a 20 percent random sample of patients admitted to U.S. hospitals, approximately 108 million patients, from the discharge data of the Nationwide Inpatient Sample from Jan. 1, 1988 through Dec. 31, 2003.

Approximately, 1.08 million (1 percent) underwent CABG, while 187,000 received heart valve replacement and repair and 1.59 million received percutaneous transluminal coronary intervention, the researchers said.

“During our 16-year study period, the rate of CABG increased from 7.2 cases per 1,000 discharges in 1988 to 12.2 cases in 1997 but then decreased to 9.1 cases in 2003, while the rate of percutaneous interventions tripled,” Ricciardi and colleagues wrote.

“For CABG, the proportion of high-volume hospitals declined from 32.5 percent in 1997 to 15.5 percent in 2003,” the authors noted.

Despite the shift, the investigators said that the in-hospital death rate following CABG decreased from 5.4 percent in 1988 to 3.3 percent in 2003. Hospitals performing the fewest CABG procedures experienced the largest decreases in death rates.

The investigators said that their findings suggest that improved quality practices may have disseminated to all facilities performing CABG. In addition, lower death rates may have remained constant at previously high-volume hospitals that began performing fewer CABG procedures.

“Our data indicate that in-hospital mortality rates and, possibly, quality care practices are improving everywhere independent of CABG volume,” the authors wrote. “This finding should challenge the setting of any arbitrary volume cut point: positive effects on patient outcome are multifactorial and are inadequately described by procedure volume. In addition, the in-hospital mortality rate after CABG may have diminished to such low levels that it is no longer a useful marker of quality.”