Enhancing respiratory sinus arrhythmia increases cardiac output in rats with left ventricular dysfunction

Area of Science:

• Cardiology
• Physiology
• Biomedical Engineering

Background:

• Respiratory sinus arrhythmia (RSA) is a natural heart rhythm variation linked to good cardiac health.
• Loss of RSA is associated with poor prognosis in cardiovascular disease, particularly heart failure.
• Heart failure often presents with a lack of heart rate variability at rest.

Purpose of the Study:

• To investigate if restoring respiratory-modulated heart rate (RMH) pacing can improve cardiac function in a rat model of heart failure.
• To determine if RMH pacing leads to reverse-remodeling of the heart.
• To compare the effects of RMH pacing with monotonic (constant rate) pacing.

Main Methods:

• Heart failure was induced in Wistar rats via coronary artery ligation.
• Rats underwent 2 weeks of daily pacing: either RMH or monotonic pacing at a matched average heart rate.
• Cardiac function was assessed non-invasively using echocardiography before and after pacing, with pacing turned off during assessment.

Main Results:

• RMH pacing significantly increased cardiac output (20%) and stroke volume compared to monotonic pacing.
• Improvements in systolic function, including circumferential strain and contractility, were observed with RMH pacing.
• Enhanced cardiac function persisted after the pacing treatment was discontinued, suggesting reverse-remodeling.

Conclusions:

• Chronic RMH pacing improves cardiac function in heart failure by enhancing systolic performance.
• The observed functional improvements, even after pacing cessation, indicate that RMH pacing may induce beneficial reverse-remodeling.
• RMH pacing represents a promising novel therapeutic strategy for heart failure management.