Cardioprotective Effect of Early Moderate Hypothermia during Ischemia

Background: Cardiac arrhythmias with cardiac arrest because of ischemic tissue are major complications after congenital heart surgery. Therapeutic hypothermia (TH) is mainly used during surgery to improve neurological outcome. In this study the authors investigated how early induced TH effects cell survival and apoptosis in cardiomyocytes.

Methods: Therefore, the authors established a cell culture model using the murine cardiac muscle cell line HL-1. Cardiac ischemia was simulated in a hypoxic chamber (0.2% O₂) in glucose and serum free medium for 6 hours. After 3 hours they induced moderate hypothermia (33.5 °C). Cell death was determined by lactate dehydrogenase release (LDH) and cell counting. Quantification of metabolically active cells was based on ATP measurement. For specific detection of apoptosis they used M30 CytoDEATH immunostaining.

Results: Under ischemia TH reduces LDH release and preserves cell numbers and intracellular ATP levels. TH also leads to less M30 CytoDEATH staining. TH helps cells to maintain a physiological morphology, the integrity of cell membrane and cell-to-cell adhesion.

Conclusions: TH is a promising therapy to protect heart tissue after cardiac arrest. The authors could demonstrate that early induction of TH after ischemia protects cardiac muscle cells from ischemic damage by down-regulating apoptotic pathways. Data lead to the assumption that early induced TH after a longer period of ischemia might be beneficial for heart tissue and to restore myocardial function.