Ventricular mechanoreflex and chemoreflex alterations in chronic heart failure

Area of Science:

• Cardiovascular Physiology
• Heart Failure Pathophysiology
• Autonomic Nervous System Regulation

Background:

• Cardiac and arterial baroreflexes are crucial for circulatory control.
• Heart failure disrupts these regulatory mechanisms.
• Ventricular vagal afferents influence heart rate and blood pressure via mechanical and chemical reflexes.

Purpose of the Study:

• To investigate alterations in ventricular mechanoreflexes and chemoreflexes in a canine model of chronic heart failure.
• To assess the impact of induced heart failure on reflex responses.
• To quantify changes in cardiac reflex sensitivity.

Main Methods:

• Utilized a conscious canine model with instrumentation for hemodynamic monitoring (left ventricular pressure, left atrial pressure, arterial pressure, heart rate).
• Employed vascular occluders and a coronary artery catheter for stimulus delivery.
• Induced chronic heart failure via rapid cardiac pacing (250 bpm) after arterial baroreceptor denervation.
• Administered prostacyclin (PGI2) as a chemical stimulus and ascending aortic occlusion as a mechanical stimulus.

Main Results:

• Ascending aortic occlusion elicited a significant heart rate decrease (36.1 bpm) before heart failure induction.
• Following heart failure induction, the heart rate response to aortic occlusion was nearly abolished.
• The sensitivity of the ventricular reflex (slope of pulse interval vs. left ventricular end-diastolic pressure) decreased by 90.5%.

Conclusions:

• Chronic heart failure profoundly diminishes ventricular mechanoreflex and chemoreflex sensitivity in dogs.
• These findings highlight significant autonomic dysfunction in heart failure.
• Impaired ventricular reflexes may contribute to the pathophysiology of heart failure.