Does lower systemic temperature enhance cardioplegic myocardial protection?

Area of Science:

• Cardiology
• Cardiovascular Surgery
• Physiology

Background:

• Maintaining myocardial protection during cardiac surgery is critical.
• Potassium cardioplegia is a standard method for inducing cardiac arrest.
• The impact of systemic temperature on cardioplegia efficacy requires further investigation.

Purpose of the Study:

• To investigate the effect of systemic temperature on myocardial cooling and rewarming rates.
• To determine if systemic temperature influences the protective effects of potassium cardioplegia.
• To assess myocardial metabolic changes under different systemic temperatures during cardioplegic arrest.

Main Methods:

• Twenty-one dogs underwent cardiopulmonary bypass with 3 hours of ischemic arrest.
• Potassium cardioplegic solution (0-4°C) was infused every 20 minutes.
• Animals were maintained at different systemic temperatures: 23°C (Group A), 30°C (Group B), and 37°C (Group C).

Main Results:

• Myocardial temperature reached 11°C in Groups A and B versus 13°C in Group C post-infusion.
• Myocardial temperature increased to 19°C (A), 21°C (B), and 26°C (C) after 20 minutes.
• Myocardial adenosine triphosphate (ATP) and glycogen significantly decreased in Groups B and C, but not in Group A.
• Lactate levels increased more in Groups B and C compared to Group A.

Conclusions:

• Moderate systemic hypothermia (23-30°C) improves myocardial protection during potassium cardioplegia.
• Lower systemic temperatures reduce metabolic derangement (ATP and glycogen depletion) during ischemic arrest.
• Systemic hypothermia enhances the efficacy of cold potassium cardioplegia, offering better myocardial preservation.