Pulse wave velocity is a noninvasive parameter that's used to evaluate arterial stiffness and it is an independent predictor of the risk for cardiovascular disease1-4). A new device that can simply measure the PWV by simultaneous oscillometric measurement of the pulse wave in all four extremities (brachial-ankle pulse wave velocity, baPWV) has recently been developed. This method is fairly reproducible and it is well correlated with the conventional central PWV5-9). The baPWV, which was confirmed in large clinical trials as a parameter of arterial stiffness, is a useful screening method for evaluating the atherosclerotic risk10-14).

Age, gender and blood pressure are the major determinants of the PWV1, 6-8, 14-16). Among these, blood pressure is affected by various conditions such as the surrounding environment, emotional stress and/or physical activities. Although attempts to correct the baPWV via the blood pressure have been done in several studies in order to estimate the absolute risk of atherosclerotic cardiovascular diseases1, 6, 16-18), there is currently no data about the effects of acute changes of the blood pressure on the baPWV in one subject. In the present study, we evaluated the relationship between the change of several blood pressure parameters and the baPWV with an acute reduction of blood pressure after the administration of sublingual nifedipine.

The clinical characteristics and hemodynamic parameters of the subjects are shown in Table 1. The subjects' mean age was 62.9±10.9 years and 7 of the 30 patients were male. Table 2 depicts the change of the blood pressure parameters, the heart rate and the baPWV after administration of nifedipine. All of the blood pressure parameters and the baPWV were acutely decreased for a brief period of time and in contrast, the heart rate was significantly increased. In 30 patients, the mean change of systolic blood pressure was 27±13 mmHg and that of the baPWV was 187±189 cm/sec. The ΔSBP, ΔDBP, ΔMAP and ΔPP between before and after the administration of nifedipine were well correlated with the ΔbaPWV, but the ΔHR was not correlated with the ΔbaPWV (Table 3). On univariate linear regression analysis, the ΔSBP, ΔDBP and ΔMAP were the significant variables for predicting the ΔbaPWV. However, the ΔDBP and ΔMAP showed weak partial correlation with the ΔbaPWV if the ΔbaPWV was adjusted by the ΔSBP, and then these 2 factors were excluded because of their statistical insignificance on the multiple linear regression analysis by the stepwise method (Table 4). Finally, the linear equation was acquired as ΔbaPWV=8.7×ΔSBP-48 (Figure 1).

Age, gender and systolic blood pressure are known to be the major determinants of the baPWV1, 6-8, 14-16). In a previous study, the baPWV was lower in females than in males until the age of 60 and it became similar in both genders over the age of 60. The relationship between age and baPWV demonstrated a quadratic curve for both genders15). Blood pressure, which is both changeable and modifiable, is also a major determinant of the baPWV for evaluating the arterial stiffness. The blood pressure is affected by various conditions such as the surrounding environment, emotional stress and/or physical activities. Therefore, it is difficult to discriminate whether the measured baPWV reflects only an elevated blood pressure or it increases the potential risk for atherosclerotic cardiovascular disease, and especially in those patients with high blood pressure. In other words, the baPWV may under- or overestimate the real potential risk for atherosclerotic cardiovascular disease if it is not corrected by the blood pressure level. There have been several studies that attempted to correct the PWV in patients by altering their blood pressure. Asmar et al1) reported on a simple linear equation to obtain the carotid-femoral PWV, and this equation was derived from the systolic blood pressure and age. Kubo et al6) also reported a regression equation that was derived from the mean systolic pressure and age by gender. Yamashina et al studied 5302 subjects with either normal blood pressure or with high blood pressure and they were without other atherosclerotic risk factors, and these researchers created a nomogram of the relation of the baPWV with blood pressure and then applied it to 297 subjects with coronary heart disease16). Yet there have been no studies about the changes of baPWV in one subject when there is an acute reduction of blood pressure. The present study confirmed that the difference of systolic blood pressure between before and shortly after the administration of nifedipine was positively correlated with the change of the baPWV. We believed that there were no changes in the conditions when measuring the baPWV except for the blood pressure. This fact may suggest that the baPWV is a reflection of the blood pressure to a large degree. Using multiple linear regression analysis, we also acquired a linear equation that can quantify the relation between the change of systolic blood pressure and the baPWV. This relationship might be useful to calibrate the change of blood pressure, especially when assessing the efficacy of antihypertensive agents for treating arterial stiffness.

The findings of our study have to be interpreted in light of the following limitation. First, we used the calcium channel blocker nifedipine (10 mg), which had an influence on the PWV by lowering the blood pressure through a vasodilatory effect. However, there are various types of antihypertensive drugs that have different mechanisms to lower blood pressure and they have different effects on the baPWV. We didn't compare the acute effect of blood pressure on the baPWV according to the types of antihypertensive drugs. Second, because the linear equation was acquired in a study that examined only 30 hypertensive patients, a larger sample size may be needed to validate and strengthen the statistical power of the equation.

In this study, we concluded that the baPWV is affected by the systolic blood pressure level to a large degree, and careful attention must be paid to the blood pressure level when evaluating arterial stiffness with using the baPWV.