INCREASED ARTERIAL OXYGEN-CONTENT - AN IMPORTANT COMPENSATORY MECHANISM IN CHRONIC MODERATE HEART-FAILURE

Study objective - The aim was to determine whether there is a compensatory increase in arterial oxygen content to a hypokinetic circulation in ambulant patients with chronic moderate heart failure caused by dilated cardiomyopathy. Design - Central haemodynamics, arterial oxygen content, arterial haemoglobin concentration, arterial oxygen saturation, and blood gases were measured during a 6 min supine exercise test on a symptom related submaximal workload. At rest, total body haemoglobin was determined. Patients - 19 patients with chronic stable moderate heart failure caused by dilated cardiomyopathy, treated with diuretics and digoxin, were studied. Measurements and main results - During exercise arterial oxygen content correlated inversely with the cardiac index (r = 0.66, p < 0.01). The two determinants of arterial oxygen content, arterial haemoglobin concentration and arterial oxygen saturation, also correlated inversely with the cardiac index (r = 0.60, p < 0.01 and r = 0.70, p < 0.001 respectively). Cardiac index during exercise correlated inversely with total body haemoglobin (r = 0.73, p < 0.001). Conclusions - A hypokinetic circulation during daily living induces an increase in arterial oxygen content in patients with chronic stable moderate heart failure caused by dilated cardiomyopathy. Renal hypoperfusion may play a role in stimulating the erythropoiesis and exertional hyperventilation in raising arterial oxygen saturation.