Effect of Remote Ischemic Preconditioning in Patient Undergoing Cardiac Bypass Surgery

Ischemic heart disease (IHD) is currently the leading cause of morbidity and mortality in the developed world, and is set to become the leading cause of death in the world by the year 2020, according to the World Health Organisation. Patients with severe IHD that require coronary artery bypass graft (CABG) surgery, although protected by techniques such as cross-clamp fibrillation and cardioplegia, still sustain significant myocardial injury as evidenced by perioperative troponin T or I or CK-MB release. Novel treatment strategies are required to limit the myocardial injury sustained by patients undergoing CABG surgery in order to improve the clinical outcomes of this patient group.

One such cardioprotective strategy is remote ischemic preconditioning(RIPC) which describes the cardioprotection obtained from inducing ischemia in tissue or an organ remote from the heart. Our laboratory and others have established RIPC using forearm ischemia (induced by an automated cuff applied to the upper arm) as an effective cardioprotective intervention in children undergoing corrective cardiac surgery for congenital heart disease and in adults undergoing CABG surgery. In this study we investigate whether simultaneous inflation/deflation of cuffs placed on the upper arm and thigh can reduce peri-operative myocardial injury and improve short-term outcomes in patients undergoing CABG surgery.

Eligible patients will be those patients undergoing elective CABG surgery who are >18 years old, with no significant renal or hepatic disease, and have not had a recent AMI (within 1 month).

Consented patients will randomized to RIPC treatment or control.The RIPC protocol will comprise simultaneous 2 x 5 minutes of forearm and lower leg ischemia (with an automated pressure cuff inflated to 200 mmHg) with an intervening 5 minutes of reperfusion (during which the cuff is deflated) between each inflation. The control protocol will comprise a deflated cuff being placed on the upper arm and thigh for 20 minutes. The RIPC protocol will be implemented after the patients have been anesthetized and immediately prior to CABG surgery.

The measured endpoint of cardioprotection will be troponin-T release at 0, 12, 24, 48 and 72 hours following CABG surgery.

Inclusion criteria

• Adult patients undergoing elective CABG surgery

Exclusion criteria

• <18 years old
• Significant renal or hepatic disease
• Previous acute myocardial infarction (within 4 weeks)