CABG Mortality: Low and Possibly Lower

According to the Foundation for Quality Health Care, overall mortality rates associated with coronary artery bypass grafting (CABG) hover at or below 2%, a 27% decrease from as recently as 2002. Ideally, surgeons aim for a mortality rate of zero, but since many CABG patients are older and high-risk, there is a low likelihood of eliminating CABG-related deaths entirely. Mortality rates following percutaneous intervention tend to be lower (1%) than those associated with isolated CABG (2%). Leadership at the Society of Thoracic Surgeons has asked cardiac surgeons to target the operative mortality rate for isolated CABG and reduce it to 1% by 2017. This will be a challenge. An article published in the Journal of Thoracic and Cardiovascular Surgery attempts to quantify the challenges, noting that the goal might be unrealistic because of the increasing number of high-risk patients that require CABG.

The researchers used data from the Society of Thoracic Surgeon’s multi-institution database for primary, isolated CABG operations from 2001 to 2012. They calculated the predicted risk of mortality (PROM) to determine the actual relationship between estimated patient risk and operative mortality. They then adjusted for operative year and surgeon volume (median volume 544 CABG procedures per surgeon over the 12-year study period).

Among the 34,416 patients they identified, the average age was approximately 64 years and the operative mortality rate was 1.87%. The association between PROM and operative mortality was highly significant. Fifty-seven percent of patients in this study had estimated mortality risk <1.27% using PROM, and fewer than 1% of patients in this group died, but PROM appears limited in its predictive capacity for those patients with estimated risk >1.27%.

The results further imply that patients with PROM >4.6%, preoperative hemodialysis requirements, or poor preoperative cardiac function are at significantly elevated risk.

Failure to prescribe statins, beta-blockers, and aspirin before discharge was a significant factor in increased mortality.

The researchers note that surgeons should be able to reduce the operative mortality rate to 1% for 60% of primary, isolated CABG patients. Unless other improvements in processes of care are made, achieving the 1% goal across the board is unlikely. They also note that prescribing medication according to the guidelines—a persistent problem in cardiology&mdash;is a critical element in process improvement.