CHF is associated with marked insulin resistance, characterized by both fasting and stimulated hyperinsulinemia. Advanced heart failure (in terms of reduced peak VO2) is related to increased insulin resistance, but this is not directly mediated through ventricular dysfunction or increased catecholamine levels.

The predictors of exercise capacity change with the development of cardiac cachexia from age and strength to peak blood flow. This shift may be caused by additional endocrine or catabolic, abnormalities active in end stage heart failure.

Abnormalities of skeletal muscle rather than of haemodynamics may be important determinants of exercise capacity in chronic heart failure. We investigated an array of indicators of central haemodynamics and peripheral muscle function to establish which resting measurements predicted exercise performance. In 20 patients quadriceps strength, resting and peak leg blood flow and leg muscle cross sectional area were measured. In 18 patients average daytime blood pressure and pulse rate, haemodynamic variables at rest and during exercise, and autonomic activity were measured. There were correlations between peak oxygen consumption and quadriceps strength (0.65; P = 0.007), thigh muscle cross sectional area (r = 0.63; P = 0.004), and average daytime systolic blood pressure (r = 0.66; P < 0.01). There were no correlations with indices of peripheral blood flow, measures of haemodynamic function, or autonomic function. Quadriceps strength was the most important individual correlate of exercise tolerance (r = 0.73). With total muscle cross sectional area and left quadriceps strength also taken into consideration, 82% of the variation in peak oxygen consumption was explained. Of the haemodynamic variables, only average daytime systolic blood pressure predicted exercise performance. The resting variables that best predict exercise performance in chronic heart failure are measures of skeletal muscle function and bulk, and average daytime systolic blood pressure. These findings suggest that abnormalities in the periphery largely determine exercise performance in chronic heart failure, and that the ability of the heart to generate an adequate blood pressure response to daily activities is also predictive of functional status.

Objective-To assess the exercise limitation of patients with chronic heart failure (CHF) and its relation to possible pulmonary and ventilatory abnormalities. Setting-A tertiary referral centre for cardiology. Methods-The metabolic gas exchange responses to maximum incremental treadmill exercise were assessed in 55 patients with CHF (mean (SD) age (13.0) years; 5 female, 50 male) and 24 controls (age 53-0 (11.1) years; 4 female, 20 male). Ventilatory response was calculated as the slope of the relation between ventilation and carbon dioxide produc- (Heart 1997;77:138-146) Keywords: metabolic gas exchange; dead space ventilation; chronic heart failure; exerciseThe cardinal feature of the syndrome of chronic heart failure is exercise limitation. The symptoms causing limitation are most frequently shortness of breath and muscle fatigue. Either symptom can occur in the same patient depending upon the type of exercise undertaken. 12 The syndrome is commonly assessed clinically using incremental exercise protocols to determine ventilation and metabolic gas exchange. Peak exercise capacity is measured as peak oxygen consumption (Vo2), although the reduction in peak Vo2 characteristic of chronic heart failure correlates only poorly with indices of haemodynamic function.134 Many investigators have shown that there is an increase in ventilation,5-7 and this increase in ventilation (VE) expressed as an increase relative to the rate of carbon dioxide production (Vco2), as VEIVCO2 slope, correlates closely with reduction in peak Vo2.89To account for the increased ventilatory response, several investigators have proposed that dead space ventilation is increased,7101 although how this abnormality is sensed is difficult to imagine, given the stability of arterial blood gas tensions during exercise in heart failure. 1213 We have explored the relations between ventilation, blood gas tensions, dead space, and metabolic gas exchange in a large group of patients with chronic heart failure and age matched controls in an attempt to determine the cause of the ventilatory abnormalities. MethodsWe examined the responses of 55 patients (average age 57-9 (SD 13.0) years; five female, 50 male) with documented treated, stable chronic heart failure. The diagnosis was confirmed by the presence of at least the following: (1)

BACKGROUND Right ventricular function may be an important determinant of exercise capacity, peak oxygen consumption (VO2), and the ventilatory response to carbon dioxide production (VE/VCO2 relation) in patients with chronic heart failure (CHF). METHODS AND RESULTS We studied the role of right ventricular function in CHF and also investigated the effects of absent right ventricular reserve in patients previously operated on with Fontan's procedure by measuring metabolic gas exchange during exercise in five groups of patients: (1) 10 patients who had previously undergone Fontan's procedure for congenital heart disease in whom the right ventricle is not functional; (2) 11 age-matched control subjects with dilated cardiomyopathy (DCM); (3) 15 age-matched normal subjects; (4) 42 patients with CHF; and (5) 16 age-matched control subjects. Left and right ventricular ejection fractions (LVEF and RVEF) were measured by radionuclide ventriculography in group 4. In the young subjects, the VE/VCO2 slope was lower in the control subjects than in the other two groups, being 24.4 +/- 4.3 against 33.3 +/- 6.6 in group 1 (P < .001) and 29.6 +/- 8.1 in group 2 (P < .05). The correlation between peak VO2 and VE/VCO2 was -0.80 (P = .005) in group 1 and -0.76 (P = .007) in group 2. In the older age groups, the VE/VCO2 slope was significantly greater (38.0 +/- 14.9 versus 25.4 +/- 3.7; P < .001) in the heart failure group (group 4). In neither control group was there a significant relation between peak VO2 and VE/VCO2 slope. In group 4, the relation between peak VO2 and VE/VCO2 was similar to that seen for groups 1 and 2. LVEF was 24.3 +/- 14.1%, and RVEF was 32.5 +/- 13.1%. There was no correlation between either RVEF or LVEF and peak VO2 or VE/VCO2 slope in the heart failure group. CONCLUSIONS The relation between excessive ventilation and reduction in peak oxygen consumption is present in patients with no functioning right ventricle. RVEF is not a determining feature of either exercise capacity or the excessive ventilatory response in CHF.