[Early changes in the circulation of the humeral artery in borderline arterial hypertension]. / Modifications précoces de la circulation de l'artère humérale dans l'hypertension artérielle limite.

The brachial artery diameter and blood flow rate were measured by pulsed Doppler velocimetry in 9 healthy subjects and 24 patients of the same age group with borderline hypertension. To evaluate the results, the patients were divided into two groups according to their cardiac output: high cardiac output group (i.e. patients whose cardiac output was superior to the mean +/- 2 S.D. value in the control population), and normal cardiac output group (i.e. cardiac output lower than that value). Patients in both groups were of the same age and had the same level of blood pressure. The brachial artery diameter and blood flow rate values were the same in the normal cardiac output group and in the control population. However, these values were significantly higher in patients with high cardiac output than in controls (P less than 0.05 and P less than 0.001) and in patients with normal cardiac output (P less than 0.01). These results suggest that the haemodynamic profile in the brachial artery is not the same in all patients with borderline hypertension: there was a tendency to vasoconstriction in patients with normal cardiac output, whereas the brachial artery was clearly dilated in patients with high cardiac output.

Effect of converting enzyme inhibitors on hypertensive large arteries in humans.

As demonstrated in hypertensive humans on the basis of non-invasive Doppler methods, converting enzyme inhibitors (CEI) dilate not only small arteries but also large arteries, particularly in the brachial and the carotid circulations. The dilating effect of CEI on large arteries is associated with an enhancement of systemic and brachial arterial compliance, implying a particular action of the drug on arterial smooth muscle. Converting enzyme inhibitors are thus able to reverse the reduced arterial compliance observed in patients with essential hypertension.

Common carotid blood flow in patients with hypertension and stenosis of the internal carotid artery.

Common carotid blood flow has been measured using pulsed Doppler techniques in hypertensive patients over 45 years of age, with and without stenosis of the internal carotid artery. In hypertensive patients without stenosis, arterial diameter remained within the normal range, whereas blood flow velocity and blood flow were significantly reduced. Vascular resistance was significantly increased but did not change markedly after administration of the vasodilating drug isosorbid dinitrate. Patients with hypertension and stenosis of the internal carotid artery were compared with two different populations used as controls: In comparison with hypertensive patients without stenosis of the internal carotid artery, both arterial diameter and blood flow velocity were reduced, leading to a more pronounced decrease in blood flow; and in comparison with normotensive patients with stenosis of the internal carotid artery, common carotid blood flow was more reduced at any degree of stenosis. In a subset of patients, blood flow returned toward normal ranges after endarterectomy. The study suggested that in patients with hypertension without stenosis of the internal carotid artery, the decrease in blood flow is due to a decrease in blood flow velocity with normal arterial diameter despite the elevated blood pressure, and in patients with hypertension and stenosis of the internal carotid artery, blood flow was more reduced than in the normotensive patients with stenosis of the internal carotid artery, suggesting that caution must be taken with indications of antihypertensive treatment.

Haemodynamic effects of vasodilating drugs on the common carotid and brachial circulations of patients with essential hypertension.

The haemodynamic pattern of the common carotid artery was studied in men with sustained essential hypertension using pulsed Doppler methods before and after administration of vasodilating drugs. Captopril produced both a fall in vascular resistance and an increase in arterial diameter of the common carotid artery. Isosorbide dinitrate increased markedly the arterial diameter but did not change vascular resistance. Nitrendipine decreased vascular resistance with no change in the arterial diameter. In the common carotid circulation of patients with essential hypertension, vasodilating drugs may either dilate small arteries (nitrendipine), large arteries (isosorbide dinitrate), or both (captopril).

[Central and peripheral hemodynamic effects of nifedipine administered orally and sublingually in essential arterial hypertension]. / Effets hémodynamiques centraux et périphériques de la nifédipine administrée par voie oral et par voie sublinguale dans l'hypertension artérielle essentielle.

The central and peripheral haemodynamic effects of the administration of 10 mg nifedipine sublingually in 6 patients with essential hypertension were compared with those observed after the administration of one 20 mg slow release tablet of nifedipine in 7 other hypertensive patients of the same age. The circulatory effects in the forearm were studied by pulsed Doppler velocimetry which allowed simultaneous measurement of the diameter of the brachial artery and of the velocity of blood flow. Both forms of administration significantly reduced the blood pressure by a significant reduction in total peripheral resistance. This reduction in total peripheral resistance was more significant (p less than 0.001 vs p less than 0.01) and more rapid with sublingual administration and was associated with a greater increase in heart rate and cardiac output. Both forms of administration induced an increase in brachial arterial blood flow due to a simultaneous increase in vessel calibre and velocity of blood flow. The results of this study show that both forms of administration act directly on the vessel wall of the arterioles and great arteries leading to a fall in blood pressure associated with an increase in peripheral blood flow. Sublingual nifedipine would seem to be the drug of choice for the treatment of hypertensive crises, whilst the slow release preparation with its lesser baroreflex stimulation would appear better suited for the long-germ treatment of essential hypertension.

Cardiopulmonary blood volume and plasma renin activity in normal and hypertensive humans.

Plasma renin activity (PRA) and systemic and forearm hemodynamics were studied during acute changes in cardiopulmonary blood volume and central venous pressure in 20 subjects, including 9 normotensive controls and 11 essential hypertensive patients of the same age. Changes in cardiopulmonary blood volume and central venous pressure were induced by a "head-down" tilt and thigh-cuff inflation. Blood pressure, pulse pressure, and heart rate did not change during cardiopulmonary blood volume variations, whereas significant changes in cardiac output, forearm blood flow, and PRA were observed. A significant negative correlation between cardiopulmonary blood volume (CPBV) and PRA existed, and slope of this correlation of delta PRA/delta CPBV was estimated as a sensitivity index of control of renin release. Sensitivity of neural control of renin release was not statistically different in normal subjects and hypertensive patients. In two groups, sensitivity of this reflex mechanism similarly decreased with age. Aging seems to be an important factor influencing the sensitivity of neural control of renin release, both in normal and essential hypertensive humans.

Effects of chronic administration of enalapril and propranolol on the large arteries in essential hypertension.

The forearm arterial effects of enalapril and propranolol were compared by means of pulsed Doppler velocimetry in 28 patients with hypertension after treatment for 3-6 months. Enalapril decreased blood pressure, increased both brachial artery diameter and blood flow, decreased vascular resistance, and increased the arterial compliance of the forearm. Propranolol also decreased blood pressure but did not produce any other changes. It may be concluded that the treatment of hypertension with enalapril, but not propranolol, is associated with dilatation effects on the arterial circulation of the forearm.

Cardiac hypertrophy and arterial distensibility in essential hypertension.

Echocardiographic determinations, left ventricular mass-volume ratio (M/V), left ventricular end-systolic stress (ESS), carotidofemoral pulse wave velocity (PWV), and brachial artery compliance (BAC), deduced from pulsed Doppler measurements and from the Bramwell-Hill equation, were evaluated in 20 patients with sustained essential hypertension in comparison with 20 control subjects of the same age and sex. In hypertensive patients, M/V ratio, ESS, and PWV were significantly increased while BAC was reduced. In the overall population, ESS was directly correlated with PWV (r = 0.73), and M/V ratio was significantly correlated with PWV (r = 0.60), BAC (r = -0.70), and systolic arterial pressure (r = 0.71). No comparable results were observed with diastolic arterial pressure. PWV was unchanged after cadralazine, a dihydralazine-like substance, and was decreased with the same blood pressure reduction following nitrendipine, a new calcium-blocking agent. These results suggest that: (1) the distensibility of large arteries plays an important role in the maintenance of cardiac hypertrophy in hypertension, and (2) antihypertensive drugs may act differently on arterial distensibility with possible consequences on ESS and reversion of left ventricular hypertrophy.

Elevation of brachial arterial blood velocity and volumic flow mediated by peripheral beta-adrenoreceptors in patients with borderline hypertension.

Simultaneous determinations of cardiac output and brachial arterial blood flow were performed in patients with hypertension and high cardiac output in comparison with normal subjects of the same age. Brachial arterial blood flow was measured with a previously described pulsed Doppler apparatus that permitted the noninvasive determination of arterial diameter and blood flow velocity. In patients with borderline hypertension, brachial blood flow was significantly increased (136 +/- 11 vs 72 +/- 8 ml/min; p less than .001). After short-term administration of indomethacin, cardiac output decreased while brachial blood flow remained constant. After short-term administration of a selective beta 1-receptor antagonist (primidolol) and nonselective blocker (propranolol), cardiac output decreased significantly in both cases but the decrease in brachial blood flow was significant only after the administration of the nonselective beta-blocking agent. The study strongly suggested that in patients with borderline hypertension, the increased cardiac output is related to a prostaglandin and beta 1-adrenergic mechanisms whereas the increased brachial blood flow depends mainly on beta 2-adrenergic mechanisms.

Forearm arterial compliance: the validation of a plethysmographic technique for the measurement of arterial compliance.

Arterial compliance was determined in eight normal subjects and 23 patients with hypertension and vascular disease by two independent techniques: (a) with a plethysmographic strain gauge (to measure pulsatile forearm volume changes as representing intra-arterial volume changes) and an automated sphygmomanometric system (to measure pulse pressure) and (b) calculation from the local pulse wave velocity and dimension of the brachial artery measured by pulsed wave Doppler ultrasound. Arterial compliance measured both by the plethysmographic technique and calculated from the pulse wave velocity was reduced in subjects with hypertension and vascular disease as compared with normal subjects. The regression equation between the compliance determined by the plethysmographic technique (x) and that calculated (y) from the pulse wave velocity and brachial arterial diameter was y = 3. 35x + 1.53, r = 0.77, P less than 0.001. The good correlation appears to validate the plethysmographic technique as a method of determining arterial compliance.

Comparison of oral MK 421 and propranolol in mild to moderate essential hypertension and their effects on arterial and venous vessels of the forearm.

The efficacy of MK 421 and propranolol was compared in 48 patients with mild to moderate hypertension. Each patient was randomly assigned to receive 1 of the drugs for 12 weeks. Additionally, a subgroup of 28 patients underwent studies of forearm arterial and venous circulation by means of pulsed Doppler and mercury-in-silastic plethysmography. Both drugs reduced supine and standing blood pressure (BP) (p less than 0.001). Propranolol reduced heart rate (p less than 0.001), while MK 421 did not change it. Brachial artery diameter, blood velocity and flow increased after MK 421 (p less than 0.001), but were not changed after propranolol therapy. Forearm vascular resistance decreased after MK 421 (p less than 0.001) and after propranolol (p less than 0.05). Forearm venous tone was unaffected on MK 421, but increased after propranolol (p less than 0.01). Thus, in moderate hypertension, 3 months of treatment with MK 421 or propranolol similarly decrease BP, but affect the forearm circulation differently: MK 421 dilates both the brachial artery and the arterioles of the forearm, but does not affect the venous vessels, and propranolol causes little arterial change but increases the forearm venous tone.

Post-synaptic alpha-blockade and brachial artery compliance in essential hypertension.

Central (six patients) and brachial (12 patients) haemodynamics were studied in men with sustained essential hypertension before and after intravenous administration of an alpha post-synaptic adrenergic blocking drug, urapidil. Brachial arterial compliance was evaluated non-invasively from the simultaneous measurement of pulse wave velocity and arterial diameter. In basal conditions, arterial compliance was reduced in hypertensives. Urapidil caused a significant drop in blood pressure, due to a significant decrease in total peripheral resistance with no change in cardiac output and heart rate. Brachial arterial diameter and compliance did not change significantly. The results show that the decreased arterial compliance in hypertensive patients was not due exclusively to the elevation of blood pressure or to a predominant activation of the autonomic nervous system, or both. Such observations suggest that, in men with sustained essential hypertension, the decreased compliance was probably related to structural alterations of large arteries.

ACE inhibition and brachial artery haemodynamics in hypertension.

Brachial artery haemodynamics, including arterial diameter, blood flow velocity, blood flow and compliance of the brachial artery may be evaluated non-invasively in man, using pulsed Doppler methods. In patients with sustained untreated essential hypertension, brachial artery diameter is increased, blood flow is normal and arterial compliance is reduced independently of the level of blood pressure. Converting enzyme inhibition may reverse the large artery abnormalities, causing an increase in arterial diameter, blood flow and arterial compliance both in acute and long-term investigations. These changes in large arteries may contribute towards improved cardiovascular morbidity and less mortality in treated hypertensive patients.

A noninvasive determination of fistula blood flow in dialysis patients.

Arteriovenous fistula (AVF) blood flow was evaluated in 32 dialysis patients using a pulsed Doppler velocimeter with two dominant features: a range-gated time system and a double transducer probe. With the proposed apparatus, the observation angle between the ultrasound beam and the vessel axis was known. In radial AVF, blood flow was 728 +/- 53 ml/min and was negatively correlated with the age of the AVF (r = -0.62; p less than 0.01). In brachial AVF, blood flow was 778 +/- 152 ml/min. In bovine heterograft AVF, blood flow was 1,225 +/- 125 ml/min. In the overall population, a negative relationship was observed between the diameter of the fistula and the blood flow velocity (r = -0.57; p less than 0.01). The study describes an accurate noninvasive method for the determination of fistula blood flow in dialysis patients, which may be helpful in the follow-up of the regional hemodynamics of this vascular access.