Microvascular reactivity in normotensive subjects with a familial predisposition to hypertension.

Using the laser-Doppler method we measured blood flow on the nailfold skin to compare the reactivity of cutaneous microcirculation in three groups of normotensive subjects: 11 subjects with a familial predisposition to hypertension without a previous record of high blood pressure, 6 predisposed subjects with a previous record of high blood pressure, and 13 subjects with no predisposition to hypertension. The flow was measured after direct and indirect skin cooling and heating and during postocclusive reactive hyperemia (PRH) after a 10-min occlusion of digital arteries. The frequency of flow oscillations in the second part of the PRH was established. Heart rate spectral analysis was performed based on the monitoring of the peripheral pulse frequency by means of the finapres device. In comparison to the other two groups of subjects, the group with a predisposition and a previous record of high blood pressure displayed a larger surface area in the low frequency band (0.05 to 0.15 Hz) of the heart rate variability power spectrum (the Bonferroni test, P < 0.05). As compared to subjects without predisposition, both groups of predisposed subjects exhibited higher frequency of flow oscillations in the second part of the PRH (the Bonferroni test, P < 0.05). Our results indicate that there could be a change in cutaneous microvascular reactivity of local (most probably myogenic) origin even in normotensive subjects with a predisposition to hypertension, whereas in normotensives with a predisposition and a previous record of high blood pressure there could be also a different cutaneous microvascular reactivity of central (nonvascular) origin.

Pressure sensitivity of flow oscillations in postocclusive reactive skin hyperemia.

Skin blood flow was monitored using a laser-Doppler (LD) flowmeter in 21 healthy volunteers after an occlusion of the digital arteries. The peripheral vascular bed was exposed to occlusion ischemia of varying duration (1, 4, or 8 min) and to a change in digital arterial pressure produced by different positions of the arm above heart level to characterize the pattern of LD flow oscillations in postocclusive reactive hyperemia (PRH) and to elucidate the relevance of metabolic and myogenic mechanisms in governing its fundamental frequency. The descending part of the hyperemic flow was characterized by the appearance of conspicuous periodic oscillations with a mean fundamental frequency of 7.2 +/- 1.5 cycles/min (SD, n = 9), as assessed by a Fourier transform frequency analysis of 50-s sections of flow. The mean respiratory frequency during the periods of flow frequency analysis was 17.0 +/- 2.2 (SD, n = 9), and the PRH oscillations remained during apnea in all tested subjects. The area under the maximum flow curve increased significantly with prolongation of the occlusion (paired t test, P < 0.001; n = 9), but showed no dependence on the estimated blood pressure in the digital arteries, which suggests the predominant role of a metabolic component in this part of the PRH response. In contrast, the fundamental frequency of PRH oscillations exhibited a significant decrease with a reduction in the estimated digital arterial pressure (linear regression, b = 0.08, P < 0.001; n = 12), but did not change with the prolongation of arterial occlusion despite a significant increase in mean LD flow (paired t test, P < 0.001; n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)