A modelling study of the cardiovascular response to exercise in patients with mitral stenosis

摘要

The objective of the present study was to quantitatively investigate the effect of mitral valve stenosis on the hemodynamics, both at rest and during exercise. The analysis was performed by means of a mathematical model. The model includes the pulsating heart, the pulmonary and systemic circulation, and the main mechanisms involved in exercise response: the ventilatory adjustments to exercise, the muscle and respiratory pump, the local metabolic vasodilation in active muscles, the central motor command, the arterial baroreflex, and the lung inflation reflex. With basal parameter values, the model is able to reproduce the cardiovascular response measured in healthy human subjects to different levels of aerobic exercise. Simulation of moderate mitral stenosis conditions shows that the pathological status at rest is partially masked by the action of the baroreflex. However, the depressed cardiac reserve is clearly revealed even at mild exercise: the stenosed heart cannot increase its output to a normal extent, seriously reducing patient's exercise tolerance. Moreover, pulmonary venous pressure increases up to a high-risk level of pulmonary edema. The model allows a quantitative interpretation of the complex interaction between regulatory mechanisms and cardiocirculatory parameters during exercise.