Final answer:
The principal electrocardiographic finding in severe valvular aortic stenosis is left ventricular hypertrophy.
Step-by-step explanation:
The principal electrocardiographic finding in severe valvular aortic stenosis is left ventricular hypertrophy. When the aortic valve is narrowed, the left ventricle needs to work harder to overcome this obstruction, which leads to the thickening or hypertrophy of the ventricular walls.