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Sodium, large arteries, and diuretic compounds in hypertension
Insights
Sodium intake and diuretics impact arterial properties in hypertension. Low sodium intake improves arterial diameter and compliance, while some diuretics may affect arterial wall elasticity independently of blood pressure changes.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
- Nephrology
Background:
- Antihypertensive drugs exhibit variable effects on arterial compliance for equivalent blood pressure reduction.
- Limited data exists on the specific impact of sodium and diuretics on arterial visco-elastic properties in hypertension.
Purpose of the Study:
- To investigate the independent effects of sodium intake and diuretic agents on arterial compliance and visco-elastic properties in hypertensive individuals.
- To clarify the role of sodium in modulating arterial wall characteristics beyond blood pressure changes.
Main Methods:
- Review of cross-sectional epidemiologic and longitudinal studies examining sodium intake, arterial diameter, and pulse wave velocity.
- Analysis of animal studies and clinical trials evaluating the effects of specific diuretics (cycletanine, indapamide, hydrochlorothiazide) and a calcium channel blocker (felodipine) on arterial compliance and pulse pressure.
Main Results:
- Decreased sodium intake correlates with lower pulse wave velocity and larger brachial artery diameter in hypertensive patients.
- Sodium overload reduces arterial compliance and distensibility, independent of blood pressure.
- Certain diuretics (cycletanine, indapamide) increased arterial compliance in animal models, while hydrochlorothiazide showed no effect in human trials.
- Indapamide improved aortic distensibility markers, whereas felodipine enhanced arterial compliance and pulse wave velocity.
Conclusions:
- Sodium influences arterial wall properties independently of blood pressure modulation.
- Diuretics appear to have the least impact on the arterial system compared to other antihypertensive agents.
- Counter-regulatory mechanisms, including the renin-angiotensin and sympathetic nervous systems, may explain observed variations in diuretic effects.
Abstract:
Clinical and experimental data have shown that antihypertensive drugs do not cause the same change in arterial compliance for an equipotent blood pressure reduction. However, there is not clear data on the effect of sodium and diuretics on the visco-elastic properties of the hypertensive arterial wall. Cross-sectional epidemiologic studies suggest that, at any given value of age and blood pressure, pulse wave velocity is lower in the presence of decreased sodium intake. Longitudinal studies indicate that, in hypertensive subjects, low sodium intake is associated with a larger brachial artery diameter than is high sodium intake. In hypertension in the elderly and in severe hypertension with end-stage renal disease, sodium overload causes a reduction in arterial compliance and distensibility unrelated to blood pressure changes. In animal studies, the diuretic compounds cycletanine and indapamide were shown to increase systemic and carotid compliance independently of blood pressure changes. In contrast, a crossover study of hypertensive subjects showed that the diuretic agent hydrochlorothiazide did not change arterial compliance and pulse wave velocity, whereas the calcium entry blocker, felodipine, improved these parameters. Nevertheless, indapamide decreased the pulse pressure on stroke volume ratio, a parameter used as a marker of aortic distensibility. Taken together, such studies indicate that sodium may act on the arterial wall independently of blood pressure changes. The contribution of counter regulatory mechanisms, possibly related to the renin-angiotensin and sympathetic nervous systems, might explain the differences between the clinical and experimental changes observed with diuretic compounds. Of the various antihypertensive agents, diuretics seem to have the least effect on the arterial system.