Exercise-Induced Oxygen Desaturation and Heart Rate Response During 6-Min Walk Test Predict Pulmonary Hypertension in Exertional Dyspnea: A Retrospective Cohort Study.

Abstract

Pulmonary hypertension (PH) is a life-threatening condition frequently associated with exertional dyspnea. It remains diagnostically challenging due to limitations in current screening modalities. While the 6-min walk test (6MWT) has been applied for risk stratification in confirmed PH, its potential role in screening remains unexplored. This retrospective cohort study investigated the diagnostic utility of 6MWT-derived parameters in 180 patients with exertional dyspnea. PH diagnosis was confirmed by right heart catheterization with the definition of mean pulmonary artery pressure > 20 mmHg. Among 79 PH patients (43.9%), a significantly reduced 6-min walk distance (6MWD) was observed compared to non-PH patients (469.5 ± 106.4 m vs. 509.8 ± 74.9 m, p = 0.019). Continuous physiological monitoring revealed that the SpO₂ trough and the heart rate (HR) peak occurred at different time points during 6MWT. Propensity score-matched case-control analysis further demonstrated greater exercise-induced desaturation of SpO₂ from the rest to minimal levels (ΔSpO₂_{rest -min}: 9 ± 9% vs. 4 ± 6%, p < 0.001) and exaggerated HR response from the rest to maximal levels (ΔHR_{max -rest}: 51±21bpm vs. 34±14bpm, p < 0.001) in PH patients. Multivariable analysis identified ΔSpO₂_{rest -min} ≥ 5% (AUC = 0.715, 95% CI: 0.640-0.852; p < 0.001) and ΔHR_{max -rest} ≥ 42 bpm (AUC = 0.740, 95% CI: 0.656-0.823; p < 0.001) as independent predictors of PH. The number of these predictors discriminated the risk of PH in dyspneic patients. A risk-stratification model incorporating these thresholds demonstrated improved predictive value for PH screening, with a C-statistic of 0.786 (95% CI: 0.710-0.863, p < 0.001). These findings suggest that parameters derived from the 6MWT, particularly exercise-induced SpO₂ desaturation and HR response, may facilitate noninvasive PH screening in exertional dyspneic patients.