Effect of Perioperative Ultrasound-guided Remote Ischemic Conditioning on Acute Myocardial Infarction

Overview

Acute myocardial infarction (AMI) is an event of myocardial necrosis caused by myocardial ischemia. Although the incidence and economic burden of AMI has declined in high-income countries, the incidence rate of AMI in China has increased dramatically over the past several decades. Initial medical therapy combined with primary percutaneous coronary intervention (PCI) is currently the most important advance in restoring coronary perfusion. Timely reperfusion therapy may halt the progress of necrosis and preserve viable tissue; however, it can also induce myocardial injury and cause cardiomyocyte death, a phenomenon called myocardial ischemia reperfusion injury (IRI), which can increase final myocardial infarct size by up to 50%. Unfortunately, there is no effective intervention for preventing IRI to date, though an improved understanding of the pathophysiology of IRI has led to the suggestion of several innovative therapeutic strategies with the potential for reducing unintended negative side effects of reperfusion therapy in AMI patients. Whether there is a therapeutic intervention that can effectively and safely reduce myocardial infarct size and cardiac mortality has been intensely explored over the years. Against this backdrop, a phenomenon called remote ischemic conditioning (RIC) has long been discussed as a potential approach to address the above issues. The purpose of present study is to investigate the efficacy of perioperative remote ischemic conditioning delivered at individual timepoints (e.g., pre-, per- and post-PCI) on myocardial injury in patients with AMI.

RIC refers to a cardio-protective effect induced by non-invasively applying cycles of physiological ischemia and reperfusion to remote body parts, e.g., through application of a blood pressure cuff or similar device to a remote limb. The actual molecular biological mechanisms underlying RIC may be attributed to a neuro-hormonal pathway conveying a cardio-protective signal from a local limb to the remote heart. The safety of RIC delivered at a single time point (e.g., pre-, per- or post-PCI) in AMI patients has been well established in a number of clinical trials. However, the RIC's cardio-protective effects remain under debate, especially for RIC programs delivered at individual timepoints during operative period (pre-, per- and post-PCI). Besides, in these trials, the cuff compression pressure of RIC protocol is mostly 200mmHg or 20-50mmHg above systolic pressure. Peripheral vascular ischemia effects of upper limbs are different under different pressure conditions. However, no study has been conducted to investigate the clinical effects of RIC training under different pressure conditions. In the present study, ultrasound is used to determine the brachial artery total occlusion pressure (TOP), which is regarded as optimal pressure of flow restriction in ischemic exercise training. And patients in the ultrasound-guided RIC group will receive RIC applying TOP as cuff compression pressure, while compression pressure applied in traditional RIC group patients is 20mmHg above systolic pressure. The purpose of present study is to investigate the effect of perioperative RIC delivered across the full disease cycle, and compare the effects of ultrasound-guided RIC protocol and traditional RIC protocol on cardiac enzyme infarct size, cardiac function, cardiopulmonary endurance and quality of life in patients with AMI.