The number of patients undergoing noncardiac surgery worldwide is growing, and annually 500,000 to 900,000 of these patients experience perioperative cardiac death, nonfatal myocardial infarction or cardiac arrest. We have previously shown that elective vascular surgery is a high-risk operation with an anticipated perioperative risk of either death or non-fatal myocardial infarction of 15%. Our previous data from the Coronary Artery Revascularization Prophylaxis (CARP) trial has showed that an elevated cardiac troponin level can occur in 25-30% of patients, and this finding is associated with an increased risk of death at 2.5 years following surgery. Because preoperative coronary artery revascularization does not improve patient outcomes, we need to test other preoperative strategies. One potential strategy for reduction of myocardial injury during surgery is Remote Ischemic Preconditioning (RIPC), which describes the cardioprotection obtained from application of brief episodes of muscle ischemia to a distant vascular territory prior to the index myocardial ischemic event. RIPC is usually applied by inflating a blood pressure cuff above the systolic blood pressure to induce transient forearm ischemia. The working hypothesis is that RIPC done within 24 hours prior to surgery will increase the proportion of patients with undetectable troponin, defined as a troponin I below the upper reference limit (URL), during the first 3 days post-surgery. We also hypothesized that among patients with a detectable troponin after surgery, RIPC reduces the median peak value, a surrogate marker for infarct size. This study will also provide a preliminary estimate of the effect of RIPC on the proportion of patients that have an increase in circulating troponin greater than 3 times the upper level in normals, a clinical significantly increase, and examine the incidence of clinically significant EKG changes. The results of this pilot investigation will be utilized to propose a multicenter, large-scale randomized controlled clinical trial of remote ischemic preconditioning prior to vascular surgery. The preliminary evidence and CDA support is not sufficient to support a definitive trial at this time. Over 300,000 surgical revascularizatin procedures are performed in the US annually as part of the treatment of expanding abdominal aortic aneurysms, critical limb ischemia, and severe carotid disease. Cardiovascular disease and peripheral arterial disease are highly prevalent among Veterans. RIPC is an inexpensive and safe therapy with proven benefits after coronary stenting and bypass surgery. We believe a positive signal in this pilot study could lay the foundation for planning and executing a multicenter clinical trial with enough power to detect clinical events.
Cardiovascular disease is the leading cause of death in the United States. Compared to the civilian population veterans have higher rates of cardiovascular risk factors and male gender preponderance, all of which contributes to higher rates of coronary heart disease. Coronary artery disease and peripheral arterial disease often coexist in the same patient. Patients with peripheral arterial disease in need of a vascular operation are at increased risk of post-operative cardiac complications, which result in excess long-term mortality. The proposed investigation aims at improving surgical outcomes by treating at-risk patients with a safe and inexpensive protocol of remote ischemic preconditioning prior to the vascular operation.