| Popis: |
Surgical intervention for chronic aortic or mitral regurgitation in asymptomatic individuals is recommended on the basis of regurgitant severity and the hemodynamic consequences on the left ventricle (LV). Echocardiography is the standard tool in clinical practice for evaluation of adults with chronic regurgitation. Regurgitant volume (RV) and fraction (RF) can be determined as the difference between stroke volumes measured at two intracardiac sites: antegrade flow across the regurgitant valve compared to antegrade flow across a normal valve. Alternatively, these severity measures can be determined by imaging the proximal flow convergence. Regurgitant orifice area also can be determined. However, limitations do exist with echocardiography due to poor image quality, variability in measuring flow diameters and foreshortened views of the ventricle. Cardiac magnetic resonance (CMR) imaging is a promising modality which can also measure regurgitant severity and may provide additional information about LV size and function. Q-flow methods allow measurement of flow velocity and instantaneous volume flow rates in the aorta or pulmonary artery; this data can be integrated over the cardiac cycle to determine RV and RF. CMR also allows accurate measurement of left and right ventricular volumes; the difference in stroke volume between the two ventricles is regurgitant volume. The role of CMR in clinical management of adults with valve regurgitation merits further study. Currently, we find CMR helpful when regurgitant severity is indeterminant on echocardiography (particularly if LV dysfunction is present), when more accurate measures of LV function are needed and when aortic dilation is present. |
