Quantification of aortic valve area and left ventricular muscle mass in healthy subjects and patients with symptomatic aortic valve stenosis by MRI.

Abstract

MRI allows visualization and planimetry of the aortic valve orifice and accurate determination of left ventricular muscle mass, which are important parameters in aortic stenosis. In contrast to invasive methods, MRI planimetry of the aortic valve area (AVA) is flow independent. AVA is usually indexed to body surface area. Left ventricular muscle mass is dependent on weight and height in healthy individuals. We studied AVA, left ventricular muscle mass (LMM) and ejection fraction (EF) in 100 healthy individuals and in patients with symptomatic aortic valve stenosis (AS). All were examined by MRI (1.5 Tesla Siemens Sonate) and the AVA was visualized in segmented 2D flash sequences and planimetry of the performed AVA was manually. The aortic valve area in healthy individuals was 3.9+/-0.7 cm(2), and the LMM was 99+/-27 g. In a correlation analysis, the strongest correlation of AVA was to height (r=0.75, p<0.001) and for LMM to weight (r=0.64, p<0.001). In a multiple regression analysis, the expected AVA for healthy subjects can be predicted using body height: AVA=-2.64+0.04 x(height in cm) -0.47 x w (w=0 for man, w=1 for female).In patients with aortic valve stenosis, AVA was 1.0+/-0.35 cm(2), in correlation to cath lab r=0.72, and LMM was 172+/-56 g. We compared the AS patients results with the data of the healthy subjects, where the reduction of the AVA was 28+/-10% of the expected normal value, while LMM was 42% higher in patients with AS. There was no correlation to height, weight or BSA in patients with AS. With cardiac MRI, planimetry of AVA for normal subjects and patients with AS offered a simple, fast and non-invasive method to quantify AVA. In addition LMM and EF could be determined. The strong correlation between height and AVA documented in normal subjects offered the opportunity to integrate this relation between expected valve area and definitive orifice in determining the disease of the aortic valve for the individual patient. With diagnostic MRI in patients with AS, invasive measurements of the systolic transvalvular gradient does not seem to be necessary.