A Multicenter Study of Noninvasive Cardiac Output by Bioreactance During Symptom-limited Exercise

BackgroundHemodynamic responses to exercise were assessed in patients with varying degrees of chronic heart failure (CHF) to determine the feasibility of using bioreactance during exercise testing in multicenter studies of CHF.Methods and ResultsA total of 210 symptomatic CHF patients and 22 subjects without heart failure were subjected to symptom-limited exercise testing on a bicycle (105) or treadmill (127) while measuring gas exchange for VO2, cardiac output (CO) noninvasively by a bioreactance technique, heart rate, and blood pressure. Peak CO (pCO) and VO2 (pVO2) during exercise were lower in patients with higher New York Heart Association (NYHA) class, in females and in older patients. Multiple linear regression analysis showed that pCO (L/min) = 19.6 + 4·M – 2.1·NYHA + 1.9·G – 0.09·Age, where M = 1 for treadmill and 0 for bicycle and G = 1 for males and 0 for females. Similarly, pVO2 (mL/kg/min) = 24 + 2.1·M – 2.9·NYHA + 1.26·G – 0.08·Age. VO2 and CO were also highly correlated to each other: pCO (mL/kg/min) = 0.059 + 0.007·pVO2 + 0.036·M – 0.025·G. Similar correlations were determined for other parameters of exercise, including left ventricular power, and the ratio of peak/resting VO2 (cardiovascular reserve), the ratio of peak/resting CO (cardiac reserve), and total peripheral vascular resistance.ConclusionBioreactance-based noninvasive measurements of CO at rest and during exertion identified abnormalities of cardiovascular function consistent with those identified by pVO2 and in prior studies using invasive CO measurements. This technique might therefore be useful for indexing disease severity, prognostication, and for tracking responses to treatment in clinical practice and in clinical trials.