Abstract
BACKGROUND: Patients with chronic conditions, such as heart failure, swim regularly and most rehabilitation exercises are conducted in warm hydrotherapy pools. However, little is known about the acute effects of warm water immersion (WWI) on cardiac haemodynamics in patients with chronic heart failure (CHF). METHODS: Seventeen patients with CHF (NYHA I and II; mean age 67 years, 88% male, mean left ventricular ejection fraction 33%) and 10 age-matched normal subjects were immersed up to the neck in a hydrotherapy pool (33-35 °C). Cardiac haemodynamics were measured non-invasively, and echocardiography was performed at baseline, during WWI, 3 min after kicking in the supine position and after emerging. RESULTS: In patients with CHF, compared to baseline, WWI immediately increased stroke volume (SV, mean ± standard deviation; from 65 ± 21 to 82 ± 22 mL, p < 0.001), cardiac output (CO, from 4.4 ± 1.4 to 5.7 ± 1.6 L/min, p < 0.001) and cardiac index (CI, from 2.3 ± 0.6 to 2.9 ± 0.70 L/min/m², p < 0.001) with decreased systemic vascular resistance (from 1881 ± 582 to 1258 ± 332 dynes/s/cm(5), p < 0.001) and systolic blood pressure (132 ± 21 to 115 ± 23 mmHg, p < 0.001). The haemodynamic changes persisted for 15 min of WWI. In normal subjects, compared to baseline, WWI increased SV (from 68 ± 11 to 80 ± 18 mL, p < 0.001), CO (from 5.1 ± 1.9 to 5.7 ± 1.8 L/min, p < 0.001) and CI (from 2.7 ± 0.9 to 2.9 ± 1.0 L/min/m², p < 0.001).In patients with CHF, compared to baseline, WWI caused an increase in left atrial volume (from 57 ± 44 to 72 ± 46 mL, p = 0.04), without any changes in left ventricular size or function or amino terminal pro B-type natriuretic peptide. CONCLUSIONS: In patients with CHF, WWI causes an acute increase in cardiac output and a fall in systemic vascular resistance. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (Identifier: NCT02949544) https://clinicaltrials.gov/ct2/show/NCT02949544?cond=NCT02949544&rank=1 .