The Effect of Different Topical Negative Pressures on Microvascular Blood Flow in Reperfused Myocardium during Hypothermia

Abstract

Objective Hypothermia is known to limit the extent of myocardial infarction. The earlier hypothermia is applied to an ischemic myocardium, the more tissue can be salvaged. Topical negative pressure (TNP) is known to increase blood flow and stimulate angiogenesis in subcutaneous tissue and skeletal muscle. We have previously shown that a myocardial TNP of −50 mm Hg significantly increases microvascular blood flow in the underlying myocardium in ischemic and reperfused porcine myocardium. The present study was designed to elucidate the effect of different TNP levels on microvascular blood flow in reperfused myocardium during hypothermia. Methods Seven pigs underwent median sternotomy. The microvascular blood flow in the myocardium was recorded before and after the application of −50, −75, −100, −125, and −150 mm Hg using laser Doppler velocimetry. Analysis was performed in the epicardium and at a depth of 6 to 8 mm in the myocardium after 40 minutes of occlusion of the left anterior descending artery followed by cooling to 31°C, and reperfusion for another 20 minutes. Results A TNP of −50 mm Hg significantly increased blood the flow in the epicardium, from 116.7 ± 10.0 PU to 244.5 ± 52.6 PU (*P < 0.05) at 31°C. A TNP of −50 mm Hg significantly increased microvascular blood flow in the myocardium, from 155.0 ± 8.4 PU to 236.7 ± 61.5 PU (*P < 0.05). Conclusions Only a TNP of −50 mm Hg, applied over the left anterior descending artery region in reperfused hypothermic myocardium significantly increased the microvascular blood flow in the epicardium and in the myocardium.