Relation between chemosensitivity and the ventilatory response to exercise in chronic heart failure

Area of Science:

• Cardiopulmonary Physiology
• Cardiovascular Research
• Respiratory Medicine

Background:

• Patients with chronic heart failure often show an increased ventilatory response during exercise.
• This hyperpnea is characterized by a steeper ventilation-carbon dioxide output (VE/VCO2) slope.
• Chemoreceptor sensitivity alterations are hypothesized to contribute to this phenomenon.

Purpose of the Study:

• To determine the chemosensitivity in patients with chronic heart failure (CHF).
• To investigate the role of chemosensitivity in the exercise hyperpnea characteristic of CHF.

Main Methods:

• Studied hypoxic and peripheral hypercapnic chemosensitivity using transient gas inhalations in 38 CHF patients and 15 controls.
• Assessed changes in chemosensitivity during mild exercise.
• Characterized central hypercapnic chemosensitivity via rebreathing in 25 patients and 10 controls.
• Performed cardiopulmonary exercise testing on all subjects.

Main Results:

• CHF patients had significantly lower maximal oxygen consumption and a steeper VE/VCO2 slope compared to controls.
• Hypoxic and central hypercapnic chemosensitivity were significantly enhanced in CHF patients at rest.
• Enhanced chemosensitivity correlated with the ventilatory response to exercise and remained elevated during exercise.
• Peripheral hypercapnic chemosensitivity was similar between groups.

Conclusions:

• Enhanced hypoxic and central hypercapnic chemosensitivity are present in patients with chronic heart failure.
• These chemosensory alterations likely contribute to the increased ventilatory response to exercise in CHF.
• Peripheral chemosensitivity plays a lesser role in CHF-related exercise hyperpnea.