Safety and feasibility of local myocardial hypothermia.

BACKGROUND In ST-elevation myocardial infarction (STEMI), reduction in time to reperfusion of the occluded coronary artery reduces infarct size. In animal models, an additional reduction of infarct size was observed when hypothermia was induced before reperfusion, despite a longer ischemic time. However, several human studies did not corroborate this positive effect, which is believed to be in part due to the inability of systemic induced hypothermia to induce sufficient decrease of local myocardial temperature before reperfusion. Providing rapid local myocardial hypothermia by intracoronary infusion of saline before reperfusion in patients with STEMI may overcome this problem. In this study, we evaluate the safety and feasibility of providing rapid intracoronary myocardial hypothermia in patients undergoing intracoronary blood flow measurements based on thermodilution with continuous infusion of saline at room temperature. METHODS AND RESULTS In 53 patients with stable angina (SA) and 20 patients with STEMI, a total of 215 measurements were performed. The measurements consisted of continuous selective intracoronary infusion of saline at room temperature with rates between 10 ml/min and 30 ml/min. Temperature changes compared to initial blood temperature (Tb ) were measured at the tip of the infusion catheter (Ti ) and distally in the coronary artery (Td ). In patients with SA, Ti was -5.65 ± 1.41°C (range -9.27 to -2.28) and Td was -0.78 ± 0.51°C (range -3.27 to -0.23°C). In patients with STEMI, Ti was -7.45 ± 0.51°C (range -8.21 to -6.56) and Td was -1.37 ± 0.82°C (range -4.62 to -0.74°C). In all patients, steady-state intracoronary hypothermia was achieved within 15 sec and could be maintained without noticeable complications. CONCLUSION This study demonstrates the safety and feasibility of inducing intracoronary hypothermia by selective infusion of saline at room temperature in patients with SA and STEMI. Steady-state hypothermia could be achieved and maintained quickly, easily, and safely using common PCI techniques. Therefore, our findings warrant further studies to the use of intracoronary hypothermia to enhance myocardial salvage in acute myocardial infarction.