At what myocardial temperature does spontaneous arrest occur?

The temperature range at which spontaneous arrest of the myocardium occurs is typically within the range of 10-20 degrees Celsius. At these lower temperatures, myocardial metabolism slows significantly, and the heart enters a state of suspended function, which can lead to arrest. This phenomenon is partly due to the reduced activity of ionic channels and enzymes, causing a decrease in electrical excitability and mechanical function of the heart muscle.

When the temperature drops to this level, the heart is more resistant to ischemic damage, and lowering temperature is a strategy sometimes employed in surgeries such as cardiac arrest for myocardial protection. The interplay between temperature decrease and metabolic processes helps to delay cellular injury, allowing for potentially safe periods of ischemia.

Understanding the significance of this temperature range is crucial for procedures that involve cardiopulmonary bypass and other situations where myocardial preservation is necessary.