A new study has analyzed the effects of a procedure, known as remote ischaemic preconditioning, on patients undergoing coronary artery bypass graft surgery.
In the procedure, the blood supply to an area of the body remote from the heart, like the arm, is briefly cut off and then restored. It has long been known that this reduces injury to the heart muscle, but this is the first randomized control trial that explores whether remote preconditioning affects long-term survival or has any effects on other clinical outcomes.
Having screened nearly 3,000 patients from the West German Heart Centre, the researchers assigned 162, who were scheduled to undergo heart bypass surgery, to the intervention group. These patients had their blood supply restricted for five minutes using a normal blood pressure cuff, followed by five minutes to restore blood supply. The cycle was repeated three times. An additional 167 patients made up a control group, and did not go through remote preconditioning.
After surgery, the researchers measured blood concentrations of troponin I, a protein that indicates damage to the heart muscle; higher concentrations would indicate more extensive damage. Damage to the heart muscle is a common consequence of complex heart surgery and is associated with poorer long-term survival. The researchers also followed up with patients for up to four years after surgery to determine any long-term health effects.
Results indicated a clear immediate benefit to the conditioning. Patients in the study group had an average troponin I concentration that was 17 percent lower than those in the control group. The long-term data were also encouraging. A year after surgery, compared to the control group, study patients were 73 percent less likely to have died of any cause, and 86 percent less likely to have died from a heart attack or stroke.
The benefit of remote ischaemic preconditioning is that it is non-invasive, simple, cheap, and safe. The procedure may be a promising way to protect patients’ heart muscle during surgery, and hopefully improve health outcomes after surgery.
The study results appear to indicate beneficial effects from the remote conditioning beyond events directly related to the heart. Incidence of non-heart-related events, such as sepsis or stroke, was also lower in the remote ischaemic preconditioning group relative to the control group. This finding suggests that the effect on the heart could be only one part of a much wider effect. Thus, remote conditioning, unlike local conditioning, may lead to persistent protection.