Effects of nitroglycerin-induced vasodilation on elastic and muscular artery stiffness in older Veterans

Vascular smooth muscle tone may play an important role in the physiology of increased arterial stiffness that occurs with aging. This study evaluated the impact of smooth muscle tone on arterial stiffness in older individuals following nitroglycerin-induced vasodilation in elastic and muscular arteries. Forty older Veterans (≥60 years old) without known cardiovascular disease were included in this study. Twenty Veterans were included as hypertensive participants (70.8 ± 6.6 years, 10 females), and 20 were included as normotensive controls (72.0 ± 9.3 years, 8 females). Nitroglycerin (NTG)-induced changes in arterial stiffness were measured locally with vascular ultrasound in the carotid and brachial arteries and regionally by carotid-femoral pulse wave velocity (cfPWV) with tonometry. With NTG treatment, both hypertensive participants and normotensive controls Veterans showed increased carotid PWV (6.4 ± 1.3 m/s to 7.2 ± 1.4 m/s, Δ 0.8 ± 1.1 m/s, p = 0.007) and cfPWV (8.6 ± 1.9 m/s to 9.5 ± 2.4 m/s, Δ 0.9 ± 2.3 m/s, p = 0.020) but did not show changes in brachial PWV (11.2 ± 2.4 m/s to 11.1 ± 2.2 m/s, Δ -0.2 ± 2.5 m/s, p = 0.72). The carotid artery was dilated more in control participants than hypertensive Veterans (Δ 0.54 ± 0.19 mm vs. 0.42 ± 0.12 mm, p = 0.022). Brachial artery dilation was similar between the two groups (Δ 0.55 ± 0.26 mm vs. 0.51 ± 0.20 mm, p = 0.46). In older Veterans without known cardiovascular disease, NTG-induced vasodilation increased elastic artery stiffness but did not change muscular artery stiffness. Increased central arterial stiffness and a decrease in the arterial stiffness gradient could offset some of the benefits of lowering blood pressure in older patients who are prescribed vasodilators as an antihypertensive therapy. Elastic artery stiffening with vasodilation warrants further investigation, as it may be important for antihypertensive medication selection and influence CVD development.