Catheter-based transcoronary myocardial hypothermia attenuates arrhythmia and myocardial necrosis in pigs with acute myocardial infarction.

OBJECTIVES: This study evaluated the efficacy of catheter-based transcoronary myocardial hypothermia (CTMH) in pigs with acute myocardial ischemia.
BACKGROUND: Although it has been suggested that hypothermia therapy can attenuate myocardial necrosis, few applications have been accepted for clinical use.
METHODS: This study comprises 2 substudies. In both studies, pigs underwent 60 min of coronary occlusion and 180 min of reperfusion. In study 1, after 15 min of coronary occlusion with an over-the-wire-type balloon (OTWB), pigs in the hypothermia group (H) (n = 13) were directly infused with 4 degrees C saline into the coronary artery through the OTWB wire lumen (2.5 ml/min) for 60 min. Pigs in the normothermia group (N) (n = 15) received the same amount of 36.5 degrees C saline. In study 2, pigs in the hypothermia-reperfusion group (HR) (n = 5) were infused with 4 degrees C saline through the infusion catheter (8 ml/min) for 30 min with a later start (60 min after coronary occlusion), whereas simple reperfusion was used for the reperfusion group (R) (n = 6).
RESULTS: Catheter-based transcoronary myocardial hypothermia was successful in both studies. In study 1, CTMH significantly decreased ventricular arrhythmia and the ratio of necrosis to ischemic risk area (H: 9 +/- 2%; N: 36 +/- 4%; p < 0.0001) with a significant reduction of enzyme leaks. In study 2, CTMH tended to reduce the ratio of necrosis (HR: 33 +/- 2%; R: 45 +/- 5%; p = 0.08). In both studies, CTMH significantly suppressed the increase of 8-iso-prostaglandin F(2alpha) while preserving the coronary flow reserve.
CONCLUSIONS: Catheter-based transcoronary myocardial hypothermia reduced myocardial necrosis while preserving coronary flow reserve, due, in part, to attenuation of oxidative stress.