Myocardial topical negative pressure increases blood flow in hypothermic, ischemic myocardium

Objectives. Hypothermia protects the myocardium from oxidative injury during ischemic stress and reperfusion. We have previously shown that topical negative pressure (TNP) of -50 mmHg significantly increases microvascular blood flow in the underlying myocardium in normal, ischemic, and reperfused porcine myocardium. The present study was designed to elucidate the effect of TNP between -50 mmHg and -150 mmHg on microvascular blood flow in ischemic myocardium during hypothermia. Design. The microvascular blood flow in the myocardium was recorded, in seven pigs, using laser Doppler velocimetry. Analyses were performed in the epicardium and in the myocardium, after 40 minutes of occlusion of the LAD followed by cooling to 31 degrees C. Results. A TNP of -50 mmHg applied to the epicardium, from 23.3 +/- 3.8 PU to 104.2 +/- 31.3 PU (*p<0.05), and in the myocardium, from 35.0 +/- 7.2 PU to 74.2 +/- 21.8 PU (*p<0.05). Conclusions. Only a TNP level of -50 mmHg significantly increased the microvascular blood flow in both the epicardium and in the myocardium during hypothermia.