Abstract 313: Effects of Therapeutic Hypothermia on Myocardial Oxygen Demand and Coronary Flow Velocity
Therapeutic hypothermia (TH) has been recently introduced as a therapeutic strategy for brain protection in comatose patients after cardiac arrest (CA). It has been hypothesized that TH could be also useful for myocardial protection thanks to the temporary reduction of myocardial oxygen demand. We aimed to evaluate the effects of mild TH on myocardial oxygen demand and coronary flow velocity (CFV).
Material and methods: We studied 11 comatose patients (9 male, aged 59 ± 12) treated with TH after CA of cardiac origin, and with angiographically normal left descending coronary artery (LAD). Rest CFV in the LAD was detected by transthoracic Doppler echocardiography at TH maintenance phase (32.7 ± 0.8 °C) and after rewarming (36.9 ± 0.5 °C).At same time we evaluated the rate-pressure product as a simple way for the estimation of myocardial oxygen demand.
Results: During TH, CFV was lower than in normothermic condition (11.5± 2.3 vs. 18.4 ± 4.8, p=0.007) as rate-pressure product (6476 ± 1261 vs. 9565 ± 2332, p=0.021). At linear unadjusted regression analysis the relationships between CFV in LAD and rate-pressure product during TH and after rewarming were close (R2=0.598, p=0.0001, figure). Furthermore, TH reduced CFV by 8.8 ± 6.9% for each 1°C reduction in body temperature.
Conclusions: TH reduces rate-pressure product and CFV thus suggesting its potential in reducing myocardial oxygen demand. CFV reduction, induced by hypothermia, parallels that of oxygen demand reduction and is related to the entity of temperature decrease. TH has a potential in protecting myocardium from ischemic damage.
- © 2012 by American Heart Association, Inc.