Modulation of ventilatory reflex control by cardiac resynchronization therapy

Area of Science:

• Cardiopulmonary Physiology
• Heart Failure Pathophysiology

Background:

• Heart failure (HF) is associated with heightened CO2 chemoreflex and ergoreflex sensitivity.
• This heightened sensitivity leads to increased ventilatory drive, manifesting as elevated minute ventilation per volume of expired CO2 (VE/VCO2).

Purpose of the Study:

• To investigate the impact of cardiac resynchronization therapy (CRT) on CO2 chemosensitivity.
• To evaluate the effects of CRT on the arterial CO2 setpoint in heart failure patients.

Main Methods:

• Cardiopulmonary exercise testing and CO2 chemosensitivity evaluation using a rebreathe method were performed before and 4-6 months after CRT in 35 HF patients.
• Paired t-tests or Wilcoxon tests were used to compare pre- and post-CRT measures.
• Multivariate analysis adjusted for age and sex was conducted.

Main Results:

• CRT significantly decreased peak VE/VCO2 (44 ± 10 vs 40 ± 8; P < .01).
• CO2 chemosensitivity decreased (2.2 ± 1.1 vs 1.7 ± 0.8 L min(-1) mm Hg(-1); P = .04), and peak end-tidal CO2 increased (29 ± 5 vs 31 ± 5 mm Hg; P < .01) post-CRT.
• The decrease in peak VE/VCO2 was strongly associated with the increase in peak end-tidal CO2 (β = -0.84; P < .0001).

Conclusions:

• The reduction in VE/VCO2 following CRT is associated with diminished CO2 chemosensitivity.
• An increase in the arterial CO2 setpoint was observed after CRT.
• These findings suggest decreased activation of both the CO2 chemoreflex and ergoreflex post-CRT.