Influence of venous function on exercise tolerance in chronic heart failure

The clinical phase of chronic heart failure (HF) includes a marked decline in exercise tolerance, in part due to impaired skeletal muscle blood flow delivery. Interestingly, the role of the venous system on exercise tolerance in patients with HF has not received much attention, despite evidence of changes in venous structure and function. The purpose of this study was to examine the relationship between forearm arterial and venous function, and exercise tolerance in patients with HF and age-matched controls.

Vascular function and exercise tolerance was examined in 20 patients with HF (age 59 +/- 13 years) and 10 control subjects (age 51 +/- 16 years). Nondominant forearm arterial inflow, vascular resistance, venous capacitance, and venous outflow were evaluated at rest and after 5 minutes of upper arm occlusion, using strain gauge plethysmography. Exercise tolerance was measured as the maximum walking distance achieved on a 6-minute walking test.

Maximum walking distance (HF: 178 +/- 65 m; controls: 562 +/- 136 m, P=.0001), and forearm vascular function after occlusion were significantly different between groups (forearm arterial inflow: HF 15.3 +/- 6; controls 22 +/- 6.7; forearm venous capacitance: HF 1.4 +/- 0.5; controls 2.0 +/- 0.4; forearm venous outflow: HF 24.5 +/- 9.4; controls: 33 +/- 10 mL x 100 mL tissue(-1) x min(-1); and forearm vascular resistance: HF 7.8 +/- 3; controls 4.6 +/- 1.4 U). Correlation analysis revealed significant associations between all forearm vascular measurements after occlusion and maximum walking distance.

These data confirm previous studies indicating the importance of arterial reactivity on exercise tolerance in patients with HF. Additionally, the results suggest the importance of venous function as a contributing factor to exercise performance.