Cardiac Preconditioning With Local Laser-Induced Hyperthermia

Background: Whole body hyperthermia has been shown to be highly effective in preconditioning cardiac tissue against reperfusion injury. The current study was aimed to assess the ability of regional sublethal laser-induced hyperthermia to precondition cardiac tissue against ischemic-induced myocardial infarction. Methods and results: Diode laser radiation was used to locally heat (42°C) the left ventricle by irradiating the epicardial surface of rat heart for 20 min. As control, another group of animals were treated with whole-body hyperthermia (WBH) for 20 min. After a 4-h recovery period, the left coronary artery was occluded for 30 min followed by 4 h of reperfusion. A significant degree of reduction in infarct size as assessed by percent of at-risk area was observed in animals that were subjected to laser-induced local hyperthermia (15.4 ± 3.1; n = 5) versus the sham group (49.8 ± 6.6; n = 5). The degree of cardiac protection induced by local hyperthermia was similar to the protection observed when the animals were preconditioned with WBH. Furthermore, regional laser-induced hyperthermia and WBH induced similar degree of up-regulation of heat shock protein 70 in cardiac tissue. Regional hyperthermia up-regulated heat shock protein in regions of the heart beyond that directly subjected to laser-induced heat stress. Conclusion: Sublethal local heating of the heart with diode laser irradiation can improve myocardial salvage and may provide a practical approach for tissue preconditioning against reperfusion injury.