Doppler Echocardiography vs. Severity Index. A. Severity index as determined by Doppler echocardiography for patients with aortic sclerosis (aortic jet velocity <2.0 m/sec), mild to moderate AS (aortic jet velocity 2.0–4.0 m/sec) and severe AS (aortic jet velocity >4.0 m/sec). The severity index increased with increasing severity of aortic valve disease and was significantly different between the three groups (p < 0.0001 by one-way [ANOVA]). B. Correlation of maximum Doppler aortic jet velocity with Severity Index. There was a strong correlation between aortic jet velocity and severity index (r = 0.84).