Feasibility of Noninvasive Assessment of Cardiac Output during Exercise in Healthy Adults by a Novel Elaboration on Systolic Time Intervals

Abstract

Background: Although assessment of cardiovascular hemodynamics during exercise can provide clinical insights, it is challenging to acquire it in clinical settings. Objectives: Accordingly, this preliminary study was to determine whether a novel elaboration on systolic time interval measures (eSTICO) method of quantifying cardiac output and stroke volume was comparable to those obtained using a validated soluble gas (open circuit CO measure [OpCircCO]) method or calculation based on oxygen consumption (oxygen consumption-based CO [VO2CO]) during exercise. Methods: For the present study, 14 healthy subjects (male: n = 12, female: n = 2) performed incremental exercise on a recumbent cycle ergometer. At rest and during exercise, cardiac output (CO) was obtained via the eSTICO method, while the OpenCircCO and VO2CO measures were obtained at the last minute of each workload. Results: At peak, there was no difference between eSTICO and OpCircCO (12.39 ± 3.06 vs. 13.96 ± 2.47 L/min, p > 0.05), while there was a slight difference between eSTICO and VO2CO (12.39 ± 3.06 vs. 14.28 ± 2.55 L/min, p < 0.05). When we performed correlation analysis with all subjects and all measures of CO at all WL, between eSTICO and OpenCircCO, there was a good relationship (r = 0.707, p < 0.001) with a Bland and Altman agreement analysis demonstrating a −1.6 difference (95% LoA: −6.3–3.5). Between eSTICO and VO2CO, we observed an r = 0.865 (p < 0.001) and a Bland and Altman agreement analysis with a −1.2 difference (95% LoA: −4.8–2.4). Conclusion: A novel exploitation of cardiac hemodynamics using systolic timing intervals may allow a relatively good assessment of CO during exercise in healthy adults.