Stroke volume during exercise in cystic fibrosis

Area of Science:

• Cardiovascular Physiology
• Pulmonary Medicine
• Cystic Fibrosis Research

Background:

• Conflicting previous studies on cardiac output (Q) and stroke volume (SV) in cystic fibrosis (CF) patients compared to controls.
• Methodological differences may explain discrepancies in prior research regarding Q and SV in CF.
• Need for better characterization of Q and SV during exercise across varying airflow obstruction severity in CF.

Purpose of the Study:

• To investigate and compare cardiac output (Q) and stroke volume (SV) during exercise in cystic fibrosis (CF) patients with mild and severe airflow obstruction.
• To identify factors influencing SV limitations in CF patients during physical exertion.

Main Methods:

• Study included 18 CF patients (FEV1 28-80% predicted) without pulmonary hypertension and 16 matched controls.
• Cardiac output (Q) measured at three upright cycle exercise intensities using the indirect Fick (CO2) method with blood gas sampling.
• Stroke volume (SV) calculated from Q and heart rate.

Main Results:

• Overall cardiac output (Q) during exercise was comparable between CF patients and control subjects.
• Stroke volume (SV) was significantly lower in CF patients compared to controls, particularly in those with FEV1 ≤ 55% predicted.
• Relative underweight significantly impacted SV, but lower SV persisted even in well-nourished CF patients with FEV1 56-80% predicted.

Conclusions:

• Despite similar cardiac output, cystic fibrosis patients exhibit reduced stroke volume during exercise.
• This SV limitation is observed across a range of lung disease severity and is not solely explained by malnutrition.
• An unidentified mechanism likely contributes to stroke volume limitation during exercise in cystic fibrosis.