Two-Dimensional and M-Mode Echocardiographic Predictors of Disease Severity in Dogs With Congenital Subaortic Stenosis

Echocardiographic studies from 50 dogs with congenital subaortic stenosis were examined. The degree of concentric, left-ventricular hypertrophy as assessed by M-mode measurement demonstrated a positive relationship (P <0.05) to disease severity. However, the clinical utility of these measures is hindered by a large amount of individual variation (r²=0.243 to 0.473). Two-dimensional ultrasound was used to compare the cross-sectional area of the left-ventricular outflow tract to the cross-sectional area of the aortic root. The ratio of these two areas demonstrated a strong inverse relationship (P=0.001; r²=0.778) with disease severity. This ratio provides a method of estimating severity of disease by two-dimensional echocardiography.