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Left ventricle haemodynamics and vaso-active hormones during graded supine exercise in healthy male subjects
I L Kanstrup1, J Marving, N Gadsbøll
1Department of Clinical Physiology and Nuclear Medicine, University of Copenhagen, Denmark.
Insights
This study shows that the heart
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Understanding the cardiac response to exercise is crucial for assessing cardiovascular health.
- Previous studies have extrapolated data from animal models, limiting direct human application.
Purpose of the Study:
- To investigate left ventricle systolic and diastolic function during graded exercise in healthy men.
- To examine the role of vaso-active hormones in cardiovascular homeostasis during exercise.
Main Methods:
- Gated equilibrium radionuclide cardiography was used to measure left ventricle functional parameters.
- Twelve healthy men underwent rest and graded supine exercise protocols.
- Vaso-active hormone concentrations (Noradrenaline, Adrenaline, Angiotensin II, Atrial Natriuretic Factor, Dopamine) were measured at various exercise intensities.
Main Results:
- Cardiac output significantly increased with exercise, driven by elevated stroke volume and heart rate.
- Left ventricle ejection and filling rates increased substantially during maximal exercise.
- Noradrenaline, Adrenaline, and Angiotensin II concentrations rose sharply at maximal exercise, suggesting a role in blood pressure regulation.
- Atrial Natriuretic Factor and cyclic guanosine monophosphate showed a continuous increase, highly correlated with each other.
- Myocardium oxygen consumption was higher than anticipated, indicating limitations in extrapolating dog heart data to humans.
Conclusions:
- The human heart's pumping capacity appears to be a limiting factor for maximal exercise performance.
- Noradrenaline, Adrenaline, and Angiotensin II play key roles in maintaining blood pressure during intense exercise.
- Dopamine has a minimal role in cardiovascular homeostasis during exercise.
- Direct extrapolation of cardiac data from dogs to humans is not advisable.
Abstract:
Left ventricle systolic and diastolic functional parameters were measured by gated equilibrium radionuclide cardiography in 12 healthy men (age 33-51 years) at rest and during graded supine exercise. The leftventricle end-diastolic volume showed an initial small (11%) increase during low submaximal exercise [from mean 163 (SD 40) at rest to mean 181 (SD 48) ml], while left ventricle end-systolic volume decreased successively [from mean 59 (SD 19) to mean 39 (SD 21) ml] with increasing exercise. Stroke volume was therefore elevated at all exercise levels compared with rest [mean 104 (SD 23) ml], and the peak value [mean 128 (SD 33) ml] was found at the lowest exercise level, contributing 40% to the initial increase in cardiac output. Cardiac output increased from mean 6.2 (SD 1.4) at rest to mean 20.2 (SD 5.0) l.min-1 at maximum. Left ventricle peak ejection and peak filling rates increased from mean 449 (SD 89) and mean 442 (SD 85) ml.s-1 at rest to mean 996 (SD 227) and mean 1255 (SD 333) ml.s-1, respectively, at maximum. The myocardium oxygen consumption, assumed to be proportional to the sum of the stroke work and the potential energy, increased fourfold, but absolute values were twice as high as expected, indicating that extrapolation from data obtained in dog hearts (as we have done) cannot be directly applied to humans. Selected vaso-active hormones were measured at all exercise intensities. Noradrenaline (NA), adrenaline (A) and angiotensin II (AII) concentrations showed a very pronounced increase at maximal exercise compared with the preceding lower intensites, while atrial natriuretic factor (ANF) and cyclic guanosinemonophosphate (cGMP) concentrations showed a more continuous increase, and dopamine (DA) remained almost unchanged. This speaks in favour of a crucial role for NA, A and AII in preserving blood pressure at maximum exercise, while DA probably has no importance for the cardiovascular homeostasis during exercise. Increases in concentrations of ANF and cGMP were highly correlated (r = 0.86). Our data supported the opinion that there is a cardiac limitation to maximal performance connected to the cardiac pumping capacity.