Feasibility of the cardiac output response to stress test in suspected heart failure patients

Lay Summary Heart failure (HF) is a global pandemic affecting 26 million people worldwide with an estimated 1 million people in the United Kingdom. Accurate early diagnosis of HF and the initiation of evidence-based treatment is essential to reduce morbidity and mortality and the associated burden on healthcare. As there are no state-of-the-art approaches, early diagnosis is challenging and often inaccurate, as initial signs and symptoms are nonspecific. We have developed an innovative test, named CORS (cardiac output response to stress test), to help general practitioners identify HF, which uses a method similar to an electrocardiogram and measures heart function at rest and during short step exercise. We recruited suspected HF patients from specialist HF diagnostic clinics in secondary care to complete the CORS test. We successfully demonstrated that 79% of patients with newly diagnosed HF (n = 38) and 91% of non-HF patients (n = 67) were able to complete all phases of the CORS test. Our findings demonstrate that newly diagnosed HF patients are able to complete this test, which provides further evidence for the potential use of the CORS test to improve HF diagnostic and referral accuracy in primary care. Background Diagnostic tools available to support general practitioners diagnose heart failure (HF) are limited. Objectives (i) Determine the feasibility of the novel cardiac output response to stress (CORS) test in suspected HF patients, and (ii) Identify differences in the CORS results between (a) confirmed HF patients from non-HF patients, and (b) HF reduced (HFrEF) vs HF preserved (HFpEF) ejection fraction. Methods Single centre, prospective, observational, feasibility study. Consecutive patients with suspected HF (N = 105; mean age: 72 +/- 10 years) were recruited from specialized HF diagnostic clinics in secondary care. The consultant cardiologist confirmed or refuted a HF diagnosis. The patient completed the CORS but the researcher administering the test was blinded from the diagnosis. The CORS assessed cardiac function (stroke volume index, SVI) noninvasively using the bioreactance technology at rest-supine, challenge-standing, and stress-step exercise phases. Results A total of 38 patients were newly diagnosed with HF (HFrEF, n = 21) with 79% being able to complete all phases of the CORS (91% of non-HF patients). A 17% lower SVI was found in HF compared with non-HF patients at rest-supine (43 +/- 15 vs 51 +/- 16 mL/beat/m(2), P = 0.02) and stress-step exercise phase (49 +/- 16 vs 58 +/- 17 mL/beat/m(2), P = 0.02). HFrEF patients demonstrated a lower SVI at rest (39 +/- 15 vs 48 +/- 13 mL/beat/m(2), P = 0.02) and challenge-standing phase (34 +/- 9 vs 42 +/- 12 mL/beat/m(2), P = 0.03) than HFpEF patients. Conclusion The CORS is feasible and patients with HF responded differently to non-HF, and HFrEF from HFpEF. These findings provide further evidence for the potential use of the CORS to improve HF diagnostic and referral accuracy in primary care.