Studies on the bradycardia induced by bepridil

Area of Science:

• Cardiology
• Pharmacology
• Electrophysiology

Background:

• Bepridil is a novel compound for angina treatment.
• Its anti-tachycardial and bradycardial effects require mechanistic investigation.

Purpose of the Study:

• To investigate the in vitro and in vivo mechanisms of bepridil's effects on heart rate.
• To elucidate bepridil's direct action on cardiac sino-atrial tissue.

Main Methods:

• In vitro: Perfused isolated rabbit sino-atrial tissue with bepridil, measuring action potential (AP) parameters.
• In vivo: Administered bepridil intravenously to dogs with denervated hearts and adrenalectomies, monitoring heart rate.

Main Results:

• In vitro: Bepridil reduced AP spike frequency, amplitude, and depolarization velocities in a dose-dependent manner.
• In vivo: Bepridil significantly decreased heart rate in dogs for over 45 minutes.
• Observed flattening of phase 0 and phase 4 slopes, and prolonged AP duration.

Conclusions:

• Bepridil directly reduces heart rate by acting on the sinus node.
• The mechanism involves altered ionic current time constants, including potassium currents.
• Bepridil demonstrates a direct bradycardial effect on cardiac tissue.