Post-ischemic myocardial function after pre-ischemic application of propranolol or verapamil

Area of Science:

• Cardiology
• Cardiovascular Surgery
• Pharmacology

Background:

• Myocardial protection during cardioplegic arrest is crucial for cardiac surgery.
• Pre-ischemic drug administration may influence myocardial outcomes post-arrest.
• Understanding the effects of beta-blockers and calcium channel blockers on myocardial function is vital.

Purpose of the Study:

• To investigate the effects of pre-ischemic propranolol and verapamil on myocardial oxygen consumption and coronary resistance.
• To evaluate the impact of these drugs on myocardial sodium uptake post-cardioplegic arrest.
• To assess the protective or detrimental effects of these agents in a canine heart model.

Main Methods:

• Langendorff technique in open-chest canine heart experiments.
• Cardioplegic arrest for 300 minutes at 22-24°C using histidine-buffered Bretschneider solution.
• Intravenous administration of propranolol (0.8 mg/kg) or verapamil (0.1 mg/kg) in two fractions before arrest.
• Post-ischemic reperfusion with modified Tyrode solution at 35°C.

Main Results:

• The verapamil group exhibited the lowest post-ischemic myocardial oxygen consumption.
• Propranolol significantly diminished coronary resistance (p < 0.05) compared to controls.
• Verapamil distinctly enhanced coronary resistance and led to massive post-ischemic myocardial sodium uptake.

Conclusions:

• Propranolol demonstrates a beneficial effect by reducing coronary resistance post-ischemic arrest.
• Verapamil's administration was associated with increased coronary resistance and myocardial sodium influx, indicating potential membrane destabilization.
• The findings suggest differential effects of propranolol and verapamil on myocardial protection strategies during cardioplegic arrest.