Intracoronary hypothermia before reperfusion to reduce reperfusion injury in acute myocardial infarction: a novel hypothesis and technique

Because current reperfusion strategies in acute myocardial infarction (AMI) seem to be exhausted in terms of additional mortality benefit, there remains a need for new methods to attenuate reperfusion injury and, thereby, further reduce myocardial infarct size and improve long-term survival. Therapeutic hypothermia (32-35°C) diminishes reperfusion injury and reduces infarct size in a variety of animal models of AMI if provided before reperfusion. In human studies this reduction has not been confirmed so far, most likely because systemic cooling acts slowly, and therefore, the target temperature is not reached in time or at all in a substantial number of patients. Furthermore, systemic cooling can cause adverse effects such as severe shivering, volume overload, and an enhanced adrenergic state. In most randomized clinical trials, however, subgroups of patients with anterior myocardial infarction that reached the target temperature before reperfusion did show a reduction in infarct size. To transform therapeutic hypothermia into a clinically feasible treatment for AMI, its method must be modified. An ideal technique should be quick enough to achieve sufficient myocardial hypothermia before reperfusion, without significant delay and without the adverse effects of systemic cooling. In this review, we propose a novel, potentially feasible method of selective intracoronary hypothermia to overcome the problems encountered with prior techniques.