Systemic Arterial Oxygen Levels Differentiate Pre- and Post-capillary Predominant Hemodynamic Abnormalities during Exercise in Undifferentiated Dyspnea on Exertion.

Hardin KM; Boston; Giverts I; Campain J; Farrell R; Cunningham T; Brooks L; Christ A; Wooster L; Bailey CS; Schoenike M; Sbarbaro J; Baggish A; Nayor M; Ho JE; Malhotra R; Shah R; Lewis GD;

Journal of cardiac failure [J Card Fail] 2023 Jul 17.
Date of Electronic Publication: 2023 Jul 17.

Background: Whether systemic oxygen levels (SaO 2 ) during exercise can provide a window into invasively derived exercise hemodynamic profiles in patients with undifferentiated dyspnea on exertion is unknown.
Methods: We performed cardiopulmonary exercise testing with invasive hemodynamic monitoring and arterial blood gas sampling in individuals referred for dyspnea on exertion. Receiver operator analysis was performed to distinguish heart failure with preserved ejection fraction from pulmonary arterial hypertension (PAH).
Results: Among 253 patients (mean ± SD, age 63±14 years, 55% female, arterial O 2 (PaO 2 ) 87±14mmHg, SaO 2 96±4%, resting pulmonary capillary wedge pressure (PCWP) 18±4mmHg and pulmonary vascular resistance (PVR) 2.7±1.2 Wood units), there was no exercise PCWP threshold, measured up to 49mmHg, above which hypoxemia was consistently observed. Exercise PaO 2 was not correlated with exercise PCWP (rho=0.04, p=0.51) but did relate to exercise PVR (rho=-0.46, p<0.001). Exercise PaO 2 and SaO 2 levels distinguished left-heart predominant dysfunction from pulmonary vascular-predominant dysfunction with an AUC of 0.89 and 0.89, respectively.
Conclusion: Systemic O 2 levels during exercise distinguish relative pre- and post-capillary pulmonary hemodynamic abnormalities in patients with undifferentiated dyspnea. Hypoxemia during upright exercise should not be attributed to isolated elevation in left heart filling pressures and should prompt consideration of pulmonary vascular dysfunction.