Objective: This is an experimental work designed to determine, using the isolated perfused rat heart, the effect of the ultra-short acting beta-blocker esmolol on cardiac arrest and cardiac function recovery following esmolol withdrawal.
Methods: Changes in heart rate, coronary flow, diastolic pressure and the rate pressure product were evaluated on the isolated heart (Langendorff model). Esmolol concentrations of 125, 250, and 500 mg/l were tested. In another experiment using esmolol concentration of 250 mg/l, cardiac function recovery was assessed after 20- and 45-min arrest.
Results: While concentrations of 250 and 500 mg/l are necessary to produce cardiac arrest, the concentration of 500 mg/l does not result in full cardiac function recovery following esmolol withdrawal. After the highest concentration of esmolol, coronary flow, heart rate and the rate-pressure product recovered to about 80, 70 and 60% of the initial control values, respectively. When comparing 20- and 45-min arrests we found cardiac function normalization occurs later after 45-min arrest.
Conclusion: The induction of cardiac arrest by esmolol is optimal at a concentration of 250 mg/l. A concentration of 125 mg/l does not result in cardiac arrest and produces bradycardia only, a concentration of 500 mg/l may be dangerous on account of persisting undesirable effects on the rat heart.