A novel cardiac output response to stress test developed to improve diagnosis and monitoring of heart failure in primary care

Sarah J. Charman, Nduka C. Okwose, Renae J. Stefanetti, Kristian Bailey, Jane Skinner, Arsen Ristic, Petar M. Seferovic, Mike Scott, Stephen Turley, Ahmet Fuat, Jonathan Mant, Richard F.D. Hobbs, Guy A. MacGowan, Djordje G. Jakovljevic

Primary care physicians lack access to an objective cardiac function test. This study for the first time describes a novel cardiac output response to stress (CORS) test developed to improve diagnosis and monitoring of heart failure in primary care and investigates its reproducibility. Prospective observational study recruited 32 consecutive primary care patients (age, 63 ± 9 years; female, n = 18). Cardiac output was measured continuously using the bioreactance method in supine and standing positions and during two 3 min stages of a step-exercise protocol (10 and 15 steps per minute) using a 15 cm height bench. The CORS test was performed on two occasions, i.e. Test 1 and Test 2. There was no significant difference between repeated measures of cardiac output and stroke volume at supine standing and Stage 1 and Stage 2 step exercises (all P > 0.3). There was a significant positive relationship between Test 1 and Test 2 cardiac outputs (r = 0.92, P = 0.01 with coefficient of variation of 7.1%). The mean difference in cardiac output (with upper and lower limits of agreement) between Test 1 and Test 2 was 0.1 (-1.9 to 2.1) L/min, combining supine, standing, and step-exercise data. The CORS, as a novel test for objective evaluation of cardiac function, demonstrates acceptable reproducibility and can potentially be implemented in primary care.