**A.3 Proper index of arterial stiffness**

β is considered not to depend on pressure, while Ep decreases with a decrease in pressure. Most of the severe MR patients with hypertension were medicated with antihypertensive drugs. Therefore, in our study, systolic pressure in MR was lower than that in the healthy subject group, and there was no difference in Ep between the two groups. However, β was higher in MR. We consider that the increase in β was not caused by MR but caused by the history of hypertension. Actually, 38% of the patients were diagnosed as hypertension and medicated. Thus, β is suitable to evaluate arterial stiffness in low pressure subjects.
