OBESITY IN CHRONIC HEART FAILURE IS ASSOCIATED WITH REDUCED EXERCISE HYPERPNEIC RESPONSE

Abstract

Objective: Patients with chronic heart failure manifest an inappropriate elevation in their ventilatory response to treadmill exercise. Increased body mass index may restrict the ventilatory response to exercise, but the relationship between obesity and ventilatory response in chronic heart failure(CHF) has not been well characterised. Methodology: We analysed data from 246 consecutive patients with chronic heart failure, who underwent cardiopulmonary exercise testing. Exercise testing was performed on a treadmill according to the modified Bruce protocol, with continuous on-line respiratory gas. The slope of the relationship between ventilation (VE) and CO2 production (VCO ) was determined by 2 computerised graphical analysis (VE/VCO slope). 2 Results: Patients were aged 60±10.7 years (mean±SD), and had mean left ventricular ejection fraction 27.7±13.9%, peak oxygen uptake 17.2±6.2 ml/min/kg. The subjects had mean body mass index (BMI) of 26.6±4.3 kg/m2 (mean±SD), and VE/VCO slope values of 37.3±10.2. The correlation between 2 BMI and VE/VCO slope was highly significant and inverse -0.455 (p<0.0001). 2 When the patients were divided into categories according to BMI (<22, 22-30, >30), there were differences between the mean VE/VCO slopes of each group, 2 which was significant for each pair of comparisons. Conclusion: This study suggests that patients with normal or mildly increased BMI show a relatively greater hyperpneic response to exercise. In contrast, patients with marked obesity (BMI>30) demonstrate a much milder hyperpneic response to exercise.