Discriminating Circulatory Problems From Deconditioning: Echocardiographic and Cardiopulmonary Exercise Test Analysis

Background Discriminating circulatory problems with reduced stroke volume (SV) from deconditioning, in which the muscles cannot consume oxygen normally, by gas exchange parameters is difficult. Methods We performed combined stress echocardiography (SE) and cardiopulmonary exercise tests (CPET) in 110 patients (20 with normal effort capacity, 54 with attenuated SV response, and 36 with deconditioning) to evaluate multiple hemodynamic parameters and oxygen content difference (A-V.O₂ Diff) in four predefined activity levels to assess which of the gas measures may help in the discrimination. Results Reduced anaerobic threshold (AT), low unchanging peak oxygen pulse, periodic breathing, shallow Δ peak oxygen consumption (V.O₂)/Δwork rate (WR) ratio, and high expired volume per unit time/carbon dioxide production (V._E/V.CO₂) slope were all associated with abnormal SV response (P < .05 for all). The best discriminator was V._E/V.CO₂ slope to V.O₂ ratio (≥ 2.7; area under the curve [AUC], 0.79; P < .0001). The optimal gas exchange model included ΔV.O₂/ΔWR < 8.6; V._E/V.CO₂ slope to peak V.O₂ ratio ≥ 2.7, and periodic breathing (AUC of 0.84; P < .0001). Conclusions The best single gas exchange parameter to discriminate between circulatory problems and deconditioning is V._E/V.CO₂ slope to peak V.O₂ ratio. Combining it with ΔV.O₂/ΔWR and periodic breathing improves the discriminative ability.