Exercise ventilatory inefficiency in heart failure and chronic obstructive pulmonary disease

Area of Science:

• Cardiology
• Pulmonology
• Exercise Physiology

Background:

• Dyspnea on exertion is a common symptom in both heart failure (HF) and chronic obstructive pulmonary disease (COPD).
• Accurate differentiation between HF and COPD is crucial for effective clinical management.
• Ventilatory efficiency indices, specifically the V̇E/V̇CO2 slope and V̇E intercept, are potential non-invasive tools for distinguishing these conditions.

Purpose of the Study:

• To compare the efficacy of non-invasive indices of ventilatory efficiency in differentiating patients with HF (both HFpEF and HFrEF) from those with COPD.
• To determine if the V̇E/V̇CO2 slope or V̇E intercept is a more accurate discriminator between HF and COPD.

Main Methods:

• Cardiopulmonary exercise testing (CPET) was performed on patients with HFpEF (n=21), HFrEF (n=20), and COPD (n=22) up to volitional fatigue.
• Ventilatory (V̇E) and gas exchange (V̇CO2) data were measured using breath-by-breath open-circuit spirometry.
• V̇E/V̇CO2 slope and V̇E intercept were calculated using linear regression, and ROC curves were used to identify optimal cutoffs for discrimination.

Main Results:

• Patients with HFrEF exhibited a significantly higher V̇E/V̇CO2 slope compared to HFpEF and COPD patients (p<0.01).
• COPD patients demonstrated a significantly greater V̇E intercept than HFpEF and HFrEF patients (p<0.01).
• A V̇E intercept cutoff of 2.64 L/min demonstrated high accuracy (AUC: 0.88, p<0.01) in discriminating COPD from HF, whereas the V̇E/V̇CO2 slope did not (p=0.11).

Conclusions:

• The V̇E intercept serves as a valuable non-invasive index for differentiating COPD from both HFpEF and HFrEF.
• The V̇E/V̇CO2 slope is less effective in distinguishing COPD from HF patients.
• These findings support the clinical utility of V̇E intercept in the diagnostic workup of exertional dyspnea.