VALVULAR AND SYSTEMIC ARTERIAL HEMODYNAMICS IN AORTIC-VALVE STENOSIS - A MODEL-BASED APPROACH

Background Assessment of the severity of a stenotic aortic valve has b een confounded by reports of flow dependence of stenosis severity. We hypothesized that the pressure gradient at the stenotic aortic valve w ould be dependent on the characteristics of the arterial circulation. Therefore, clinically useful measures of the severity of aortic valve stenosis may have to take this dependence into account. Methods and Re sults We developed an analog model of the systemic arterial circulatio n in the presence of a stenotic aortic valve. The model clearly descri bes the dependence of stenosis severity (described by coefficients A a nd B) on the resistive and capacitive properties of the arterial syste m. We used high-fidelity pressure recordings obtained at the time of d iagnostic cardiac catheterizations and found that a highly significant relation between the measured mean transvalvular gradient and that pr edicted by the model was demonstrated both at rest (r(2)=.90) and with exercise (r(2)=.80). Furthermore, the relative constancy of stenosis coefficients A and B was validated. Conclusions Transvalvular hemodyna mics in patients with aortic valve stenosis are dependent on the prope rties of the arterial system. The current model describes such behavio r, correctly predicts the transvalvular gradient from model parameters , and may be useful in the assessment of stenosis severity under vario us clinical and physiological conditions.