Ischemic preconditioning may reduce adverse outcomes in CABG patients

Preconditioning the heart with brief episodes of ischemia before an elective coronary artery bypass graft (CABG) protected the heart from injury and lowered the risk of mortality, German researchers found in a study published Aug. 17 in The Lancet.

“The cardioprotective effects were measured as a 17.3 percent reduction in the cTnI [cardiac troponin] AUC [area under the curve] by remote ischemic conditioning," wrote the authors, led by Matthias Thielmann, MD, PhD, of the West-German Heart Center in Essen. Previous studies, they added, made a similar finding.

The researchers randomized 329 patients who underwent elective CABG surgery under cold crystalloid cardioplegia and cardiopulmonary bypass between April 2008 and October 2012. They were assigned to receive either remote ischemic preconditioning or no preconditioning. The preconditioning consisted of three cycles of five minutes of ischemia and five minutes of reperfusion in the left upper arm after anesthesia induction.

To bring on ischemia, a blood pressure cuff was inflated to 200 mm Hg. Patients in the control group wore a cuff, but it was never inflated.

Blood samples were obtained before and at various times after surgery to measure troponin levels, which helped determine perioperative myocardial injury, the primary endpoint.

cTnI AUC was 266 ng/mL over 72 hours in the preconditioning group and 321 ng/mL in the control group. All-cause mortality and major adverse cardiac and cerebrovascular events (MACCE) were also lower in the preconditioning group than in the control group. At one year, all-cause mortality was 1.9 percent vs. 6.9 percent and MACCE was 2.6 percent vs. 12 percent.

“In cardiac surgery, perioperative myocardial injury is closely associated with postoperative morbidity and mortality in the short and long terms,” the authors explained. The patients in their study, however, were low-risk in terms of adverse postoperative outcomes. Future studies, the authors suggested, should be conducted in higher-risk populations.

A similar but larger, multicenter trial—the ERICCA trial—is currently underway in Europe that may provide move evidence of the benefits of preconditioning, but at this point, “our findings indicate that remote ischemic preconditioning is a safe perioperative method that provides cardioprotection and improves prognosis in patients undergoing elective CABG surgery,” Thielmann and his colleagues wrote.

In an accompanying editorial, Nathan Mewton, MD, PhD, and Michel Ovize, MD, PhD, of Claude Bernard University in Lyon, France, noted that the study also found a lower incidence of events not related to the heart, such as sepsis and stroke.

“These findings suggest that the effect on the heart might be only one aspect of a much wider effect, and that remote conditioning, unlike local conditioning, might lead to persistent protection,” they wrote.