Cardiac output during exercise related to plasma atrial natriuretic peptide but not to central venous pressure in humans

New Findings

What is the central question of this study?

Is cardiac output during exercise dependent on central venous pressure?

What is the main finding and its importance?

The increase in cardiac output during both rowing and running is related to preload to the heart as indicated by plasma atrial natriuretic peptide but unrelated to central venous pressure. The results indicate that in upright humans central venous pressure reflects the gravitational influence on central venous blood rather than preload to the heart.

Abstract

Aim

This study evaluated the increase in cardiac output (CO) during exercise in relation to central venous pressure (CVP) and plasma arterial natriuretic peptide (ANP) as expressions of preload to the heart.

Methods

Seven healthy subjects (four men; 26 ± 3 years; 181± 8 cm height; and 76 ± 11 kg, weight; mean ± SD) rested in sitting and standing positions (in randomized order) and then rowed and ran at submaximal workloads. The CVP was recorded, CO (Modelflow) calculated, and arterial plasma ANP determined by radioimmunoassay.

Results

While sitting CO was 6.2 ± 1.6 l/min, plasma ANP 70 ± 10 pg/ml, and CVP 1.8 ± 1.1 mmHg (mean ± SD) and decreased to 5.9 ± 1.0 l/min, 63 ± 10 pg/ml, and ‐3.8 ± 1.2 mmHg, respectively when standing (P < 0.05). Ergometer rowing elicited an increase in CO to 22.5 ± 5.5 l/min as plasma ANP increased to 156 ± 11 pg/ml and CVP to 3.8 ± 0.9 mmHg (P < 0.05). Similarly, CO increased to 23.5 ± 6.0 l/min during running with albeit smaller (P < 0.05) increase in plasma ANP, but with little change in CVP (‐0.9 ± 0.4 mmHg).

Conclusion

The increase in CO in response to exercise is related to preload to the heart as indicated by plasma ANP, but unrelated to CVP. The results indicate that in upright humans CVP reflects the gravitational influence on central venous blood rather than preload to the heart.

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