Noninvasive evaluation of mitral regurgitation by analysis of left atrial signal loss in cine magnetic resonance

Magnetic resonance imaging that uses shallow flip angles, short repetition times, and gradient refocused echoes results in multiple images throughout the cardiac cycle in which the blood pool has high signal intensity. In cine magnetic resonance images, disturbed (high velocity) blood flow produces a loss of signal intensity within the intracavitary blood pool, which makes this technique potentially useful for evaluating valvular disease. Multilevel cine magnetic resonance imaging was performed in 26 patients with mitral regurgitation (MR) documented and graded for severity by Doppler echocardiography or contrast ventriculography. Intracavitary left atrial signal intensity was analyzed in order to derive parameters that reflect the severity of the lesion. Seven normal volunteers were studied for comparison. All regurgitant lesions were visualized in cine magnetic resonance images as discrete regions of systolic signal loss extending from the mitral valve into the left atrium. The extent and degree of signal loss correlated well with severity. In patients with mild MR, signal loss was seen in 3.3 ± 1.2 (±SD) anatomic levels compared to 4.9 ± 1.4 levels in patients with moderate MR ( p = NS), and in 7.0 ± 1.4 levels in patients with severe MR ( p < 0.001 versus mild MR). The total area of maximal systolic left atrial signal loss seen in all levels was 10 ± 6 cm 2 in mild versus 31 ± 17 cm 2 in moderate ( p < 0.001) and 96 ± 30 cm 2 in severe MR ( p < 0.001). In normal subjects, signal intensity increased within the left atrium during systole, whereas in patients with MR the total left atrial signal intensity during systole decreased in relation to severity. Thus by analysis of left atrial signal characteristics, cine magnetic resonance imaging provides a noninvasive means for semiquantitation of MR.