Low-frequency and low-intensity ultrasound increases cardiac parasympathetic neural activity and decreases clinic hypertension in elderly hypertensive subjects with type 2 diabetes

BACKGROUND: The aims of the present study were to determine the effects of an ultrasound irradiation on clinic hypertension and the heart rate variability in elderly hypertensive subjects with type 2 diabetes. METHODS: We examined the effects of ultrasound (800 kHz, 25 mW/cm(2)) applied to the forearm for 10 min on the autonomic nerve activity and the difference between BP at home and at a clinic visit in Japanese subjects with type 2 diabetes and hypertension. RESULTS: In 108 subjects who displayed systolic BP (SBP) >140 mm Hg at a clinic visit, 75 subjects (69%) had a mean SBP <135 mm Hg at home and 33 subjects (31%) had a mean SBP >135 mm Hg at home in the morning for 14 days. SBP, pulse rate, and pulse pressure in the ultrasound treatment group were significantly lower than the baseline values in these hypertensive subjects with type 2 diabetes, and lower than those of placebo controls independently of SBP at home. In 31 subjects who displayed systolic BP >140 mm Hg at a clinic, standard deviation of all RR intervals and the root mean square of successive differences were significantly higher in the ultrasound treatment group than the baseline values in these hypertensive subjects with type 2 diabetes, and lower than those of placebo controls. CONCLUSIONS: The ultrasound treatment increases the cardiac parasympathetic neural activity and decreases the differences between SBP at home and at a clinic visit in elderly hypertensive subjects with type 2 diabetes.