Forearm arterial distensibility in systolic hypertension

Abstract

It is unclear whether the stiffened arterial tree in systolic hypertension is the cause or the effect of the disease. In this study, brachial and radial arterial pulses were sensed by external Pixie transducers and measurements of pulse wave velocity converted to volume distensibility using the Bramwell-Hill equation. Blood pressure was controlled as a variable by repeating the measurements at a variety of transmural arterial pressures. This was accomplished by encasing the forearm in a rigid plastic cylinder within which pressures were varied. Twenty-nine patients with systolic hypertension were compared with 22 age-matched control subjects. At ambient pressures the volume distensibility of patients was lower than that of control subjects (0.10 versus 0.18% delta volume/mm Hg, p less than 0.001) but there was no difference in volume distensibility between the two groups at any comparable transmural pressure. Nineteen patients were treated for 1 month with a thiazide diuretic agent and the studies were then repeated. Systolic and diastolic blood pressure decreased significantly and volume distensibility increased (0.10 to 0.15% delta volume/mm Hg, p less than 0.001) at ambient pressures. But at comparable transmural pressures, volume distensibility was unchanged. It is concluded that, in the forearm, increased arterial stiffness is the result and not the cause of systolic hypertension, but these data cannot exclude increased aortic stiffness as a significant factor. Thiazide diuretic drugs increase forearm arterial compliance by lowering blood pressure without a demonstrable drug effect on this arterial wall.

A longitudinal study of vessel wall properties in normotensive and hypertensive renal transplant recipients

“…2,11,[15][16][17] Comparisons of mechanical vessel wall properties in normotensive and hypertensive patients are hampered, since the pressure-volume relationship in large arteries its not linear and the mechanical vessel wall properties can only be defined in terms of a given pressure. 11 Decreased arterial distensibility in hypertension can be the result of increased levels of distending pressure or may reflect chronic structural changes.…”

Improved arterial distensibility in normotensive subjects on a low salt diet.

“…Other studies have reported an increase in forearm volume arterial distensibility of hypertensive subjects after only 1 month of treatment with thiazide diuretics. 13 Although this may have been due to a reduction in blood pressure caused by the diuretics, it has been shown that reduction in brachial artery compliance obtained with isotonic saline infusion is due to mechanisms other than changes in blood pressure.…”

Carotid artery distensibility and distending pressure in hypertensive humans.

“…9 ' 10 Using determinations of pulse-wave velocity measured on the human forearm enclosed in an airtight box, Gribbin et al 9 and Smutyan et al 10 showed that, for the same mean transmural pressure, NT and HT had the same pulsewave velocity and therefore the same distensibility as derived from the Bramwell and Hill formula. However, arterial diameter and volume were not measured in these studies.…”

“…6 -8 Two different mechanisms have been suggested to explain these earlier alterations in hypertensive subjects: structural changes due to arterial degeneration or functional changes due to the increased distending pressure. 13 Gribbin et al 9 and Smulyan et al 10 have shown, by enclosing the forearm inside an airtight box and varying transmural pressure, that the increased distending pressure alone may explain the higher pulse wave velocity of hypertensive subjects. In addition, arterial wall hypertrophy in hypertensive subjects is not necessarily associated with reduced distensibility.…”