Low exercise capacity increased CABG mortality risk in ischemic LV dysfunction

Among patients with ischemic left ventricular dysfunction, those with poor exercise tolerance are at elevated early and 5-year risk for mortality after CABG compared with medical therapy, according to recent findings.

Conversely, patients with a higher exercise capacity have better 5-year survival outcomes with CABG, the researchers wrote.

In an exploratory analysis, researchers evaluated 1,212 patients enrolled in the STICH trial, in which participants, all of whom were diagnosed with ischemic LV dysfunction and CAD, were randomly assigned to medical intervention alone (n=602) or medical therapy with CABG (n=610).

Before randomization, the researchers evaluated the patients’ physical activity level via a quality-of-life questionnaire and their performance during a 6-minute walk test. The questionnaire sought information on physical abilities and activities, as well as the extent to which the patients felt limited by HF. Based on the participants’ responses, the researchers ascribed a numeric Physical Ability Score (PAS) between 0 and 100, with 100 indicating no limitation during physical activity, to each patient. During the walking test, patients were instructed to walk around an established course for 6 minutes and attempt to cover as much ground as possible, but also to stop and rest as needed.

The primary outcome of the study was all-cause mortality during a median follow-up of 56 months.

Patients were able to walk 300 m during the 6-minute walk test in 682 cases, whereas 530 participants were unable to do so. PAS was >55 in 749 cases, and 433 patients had a PAS ≤55. During the study period, 462 patients died, with most deaths due to CV-related causes (80%).

Among the patients randomly assigned to CABG who walked ≥300 m during the test, the risk for mortality was lower compared with nonrecipients who walked the same distance (HR=0.77; 95% CI, 0.59-0.99). Mortality risk was also lower for CABG-allocated patients among those with a PAS >55 (HR=0.79; 95% CI, 0.62-1.01 vs. medical therapy alone), but this trend did not reach statistical significance. Mortality rate did not differ significantly according to treatment among those unable to walk 300 m during the test.

The researchers noted that patients who walked ≥300 m during the test and had a PAS >55 (n=486) were at significantly reduced mortality risk with CABG (HR=0.71; 95% CI, 0.52-0.97). No difference in mortality risk was observed according to treatment among those who did not meet both criteria.

Patients who were unable to walk 300 m during the test or who had PAS ≤55 had significantly higher 60-day mortality risk after CABG (HR=3.24; 95% CI, 1.64-6.83 vs. medical therapy).

Vera Bittner

In an accompanying editorial, Vera Bittner, MD, of the cardiovascular disease division at the University of Alabama at Birmingham, wrote that these findings make a possible case for pre-CABG exercise, or “pre-habilitation.”

“Could such exercise training be used in individuals with LVD before elective CABG to improve functional status, improve prognosis overall, and result in better outcomes after the surgical intervention?” Bittner wrote. “… Future studies should explore whether exercise training before CABG can improve post-surgical mortality in deconditioned CHD patients with and without LV [dysfunction].”

For more information:

Bittner V. JACC Heart Fail. 2014;doi:10.1016/j.jchf.2014.05.002.

Stewart RAH. JACC Heart Fail. 2014;doi:10.1016/j.jchf.2014.02.009.

Disclosure: The researchers report no relevant financial disclosures.