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

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.

Validation of radiofrequency determined lung fluid using thoracic CT: Findings in acute decompensated heart failure patients.

BACKGROUND: Noninvasive outpatient monitoring for heart failure (HF) has significant opportunity to reduce patient morbidity and the costs associated with recurrent hospitalization. The purpose of this study was to validate the ability of radiofrequency (RF) to assess lung fluid via a wearable patch device compared to thoracic CT in order to characterize volume overload. METHODS: 120 subjects were studied: 66 acute heart failure (AHF) inpatients and 54 subjects without AHF (Control - 44 healthy and 10 stable HF). All underwent supine thoracic CT scans and supine RF readings from the wearable patch device placed on the left mid-axillary line (age = 74 ± 16 vs. 57 ± 15 yrs.; female = 38 vs. 44%; BMI = 33.2 ± 9.0 vs. 27.3 ± 5.1, AHF vs. Control respectively). Reflected RF signals and subject-specific anthropometric data were used to calculate the RF-determined lung fluid content. CT Lung fluid was reported as percentage of lung volume. Classification analyses were used to compare RF and CT performance. RESULTS: AHF presented with higher lung fluid than controls by both CT and RF (CT: 20.1 ± 4.2% vs. 15.4 ± 2.4%; RF: 20.7 ± 5.6% vs. 15.6 ± 3.3%; p < 0.05 for all). The correlation between lung fluid measured by CT vs. RF was r = 0.7 (p < 0.001). RF determined lung fluid performed as well as CT in distinguishing AHF from control subjects: Sensitivity: 70% vs. 86%; Specificity: 82% vs. 83%; Positive Predictive Value: 82% vs. 86%; Negative Predictive Value: 69% vs. 83%, CT vs. RF respectively. CONCLUSIONS: Noninvasive nonionizing RF determined lung fluid provides a potential alternative to other measures for diagnosing and monitoring pulmonary fluid overload.