Magnetic resonance imaging in valvular heart disease.

Magnetic resonance techniques can be employed to depict valvular abnormalities but are especially helpful in quantifying regurgitant or stenotic lesions which cannot be quantitatively assessed by other noninvasive techniques. Gradient echo techniques and phase velocity mapping are the most important magnetic resonance pulse sequences employed for these purposes. Valvular regurgitation can be quantitated by measuring the area of signal void on conventional gradient-echo images, by calculating stroke volume differences from k-space segmented gradient echo images, by measuring the proximal convergence zone from velocity encoded images or by comparing stroke volumes of the ventricles from velocity measurements. In contrast to this variety of possibilities in regurgitant lesions, stenotic lesions can only be quantitated by using velocity mapping techniques. Magnetic resonance spectroscopy can be used to assess myocardial metabolism in chronic valvular lesions. However, this tool needs further development and more clinical data before its use can be recommended to assess the necessity and optimal timing of surgical intervention.