[Ventricular pump function under ectopic excitation of the frog heart]

Area of Science:

• Cardiac Electrophysiology
• Ventricular Pump Function
• Amphibian Physiology

Context:

• Understanding cardiac excitation-contraction coupling is crucial for cardiovascular research.
• Ectopic beats can alter heart rhythm and pump efficiency.
• The frog heart (Rana temporaria) serves as a model for studying cardiac mechanics.

Purpose:

• To investigate the effects of ectopic excitation on ventricular pump function in frogs.
• To compare the impact of pacing the ventricular base versus the apex on cardiac performance.
• To analyze changes in intraventricular pressure, pressure rise rate, relaxation, and QRS duration.

Summary:

• Pacing the ventricular base and apex in frogs led to decreased systolic pressure and increased QRS duration compared to supraventricular rhythm.
• Ventricular pacing, especially at the apex, reduced the systolic rate of pressure rise (dP/dtmax).
• Apical pacing significantly slowed isovolumetric relaxation (dP/dtmin), indicating impaired ventricular relaxation.

Impact:

• Ventricular pump function is demonstrably reduced under ectopic excitation, with apical pacing having a more pronounced negative effect.
• Findings highlight the importance of excitation origin in determining cardiac mechanical output.
• This research provides insights into the electro-mechanical coupling mechanisms in the vertebrate heart.