Exercise stroke volume and heart rate response differ in right and left heart failure

Area of Science:

• Cardiology
• Pulmonology
• Exercise Physiology

Background:

• In pulmonary arterial hypertension (PAH), exercise capacity is limited by elevated pulmonary artery pressure impacting stroke volume (SV).
• In left heart failure (LHF), SV increase during exercise is constrained by left ventricular function.
• Distinct hemodynamic profiles in PAH and LHF may lead to different exercise-induced heart rate (HR) and SV responses, with potential implications for treatment, including beta-blocker therapy.

Purpose of the Study:

• To investigate and compare the exercise response of SV and HR between patients with PAH and LHF.
• To test the hypothesis that SV and HR responses to exercise differ significantly between PAH and LHF populations.

Main Methods:

• A cohort of 28 PAH patients and 18 LHF patients, matched for maximal oxygen uptake (<15 mL/kg/min) and without prior beta-blocker exposure, underwent maximal cardiopulmonary exercise testing.
• Data collected included SV and HR responses relative to oxygen uptake during exercise.

Main Results:

• Both PAH and LHF groups demonstrated similarly impaired exercise tolerance, approximately 42% of predicted maximal oxygen uptake.
• PAH patients exhibited a significantly lower peak SV response to exercise compared to LHF patients (-14 mL, P = 0.01).
• This diminished SV response in PAH was compensated by a steeper increase in HR relative to oxygen uptake (0.03 beats/mL, P = 0.001).

Conclusions:

• Patients with PAH demonstrate a smaller increase in stroke volume during exercise compared to those with LHF.
• Conversely, PAH patients show a proportionally larger increase in heart rate during exercise than LHF patients.
• These differential responses highlight distinct cardiovascular adaptations to exercise in PAH and LHF, informing therapeutic strategies.