Prolonged oxygen pulse oscillation during cardiopulmonary exercise testing identifies subclinical pulmonary congestion in heart failure

Abstract

Subclinical pulmonary congestion is common in heart failure (HF) and often remains undetected at rest. Oxygen pulse (VO2/HR), a surrogate of stroke volume, may exhibit oscillatory behavior during exercise reflecting hemodynamic instability. We evaluated whether the duration of significant oxygen pulse oscillations during CPET identifies pulmonary congestion detected by lung ultrasound (LUS).

We studied 104 patients with heart failure across the spectrum of left ventricular ejection fraction (preserved, mildly reduced, and reduced). During CPET, oxygen pulse oscillations were analyzed in the Wasserman panel, defining significant oscillations as fluctuations >10%. The primary variable was the percentage of total exercise time exhibiting significant oscillations.

Pulmonary congestion was assessed by LUS using a 12-zone protocol. Congestion was defined as ≥5 bilateral B-lines present in at least 3 zones.

Correlation between oscillation time and congestion was assessed using Spearman analysis. Diagnostic performance was evaluated by ROC analysis.

Results

Patients exhibiting significant oxygen pulse oscillations during >42% of total CPET duration showed evidence of pulmonary congestion on LUS.

The 42% threshold demonstrated:vStrong correlation with subclinical congestion (Spearman analysis)Sensitivity: 92%Specificity: 94%

This pattern was observed across HF phenotypes irrespective of baseline ejection fraction.

Conclusions

Prolonged oxygen pulse oscillation during exercise is a powerful marker of subclinical pulmonary congestion in heart failure. Quantifying the proportion of exercise time with significant oscillations provides a non-invasive, effort-based method for congestion detection and may enhance risk stratification during CPET.Oxygen pulse oscillationOscillation time and EF