Abstract 153: Timing of Hypothermia to Reduce Infarct Size in St-Elevation Myocardial Infarction and Improve Survival in Cardiogenic Shock
Background: In ST-elevation myocardial infarction (STEMI) cardiogenic shock account for half of the early mortality. Hypothermia is beneficial in protecting the brain after cardiac arrest. Previous clinical hypothermia studies have failed in protecting the heart in ST-elevation myocardial infarction (STEMI). We did a series of pig studies to develop a rapid cooling protocol (cold saline and endovascular cooling), evaluate timing of hypothermia (how long before and after reperfusion) and the effect in cardiogenic shock.
Methods: A closed chest pig model with 40 min ischemia in mid-LAD. A pig cardiogenic shock model (occluded proximal LAD 40 min). Cold saline (1–2 l) and endovascular cooling was evaluated in a phase I STEMI trial (20 patients). Myocardium at risk (MaR) and infarct size (IS) were assessed by cardiac magnetic resonance using T2-weighted imaging and late gadolinium enhancement imaging, respectively.
Results: The pig STEMI trials show that hypothermia must reach a target temp of < 35°C before reperfusion to reduce infarct size. Prolonged postreperfusion hypothermia from 15 to 60 min did not improve infarct size reduction. Cold saline and endovascular cooling induced rapid cooling in pigs (5 min to < 35°C) and in man (17 min to < 35°C) and reached target temp in all STEMI patients before reperfusion (PCI) and reduced infarct size by 38%. No increase in heart failure or pulmonary congestion was seen. Hypothermia induced with endovascular cooling alone in pigs reduced acute mortality in cardiogenic shock, improved hemodynamic parameters and reduced metabolic acidosis.
Conclusions: Hypothermia must reach target temp (< 35°C) before reperfusion to reduce infarct size and this can be achieved by a combination of cold saline and endovascular cooling. Hypothermia in cardiogenic shock reduces mortality, improves hemodynamic parameters and reduces metabolic acidosis. Our studies suggest that hypothermia could be beneficial for STEMI patients both by reducing infarct size and increase survival in cardiogenic shock. We suggest a protocol of rapid cooling with cold saline and endovascular cooling before reperfusion with short (1 h) postreperfusion cooling to be tested in larger clinical trials. In cardiogenic shock, prolonged cooling could be beneficial.
- © 2010 by American Heart Association, Inc.