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Biomedical subjects

N De Luca

Publications and source records attributed to N De Luca.

At least 55 records · Page 3Linked to original sources
PubMed1989

Blunted sympathetic response to cardiopulmonary receptor unloading in hypertensive patients with left ventricular hypertrophy. A possible compensatory role of atrial natriuretic factor.

To investigate whether or not hypertension with left ventricular hypertrophy (LVH) modifies the mechanisms underlying the vascular adjustments to orthostatic stress, we evaluated the hemodynamic and hormonal effects of graded lower-body negative pressure (LBNP) (-10 and -40 mm Hg) before and after sympathetic blockade in 10 hypertensive patients with LVH and in five age- and sex-matched normotensive subjects. In control conditions, LBNP elicited comparable vasoconstrictor responses in the forearm in the two groups. In normotensive subjects, graded increases in plasma norepinephrine and plasma renin activity (PRA) and reductions in plasma immunoreactive atrial natriuretic factor (irANF) were recorded. In hypertensive patients, a significant increase in plasma norepinephrine and plasma renin activity was obtained only with the higher level of LBNP, whereas irANF plasma levels decreased progressively. In both groups, sympathetic blockade abolished the increase in plasma renin activity and did not modify the changes in plasma irANF induced by both levels of LBNP in control conditions. The vascular response to -10 mm Hg LBNP remained unchanged after sympathetic blockade in both groups. However, after sympathetic blockade, the vasoconstrictor response to -40 mm Hg LBNP in normal subjects was no longer different from that elicited by -10 mm Hg LBNP, whereas in hypertensive patients the vasoconstrictor response was still significantly higher than that induced by -10 mm Hg LBNP. Direct correlations between the percent changes in forearm vascular resistance and those in plasma norepinephrine and plasma renin activity were found only in normal subjects in control conditions but were not observed after sympathetic blockade. On the contrary, the inverse correlation between changes in irANF plasma levels and in forearm vascular resistance found in control conditions in both groups was still observed after sympathetic blockade. In a separate group of hypertensive patients with left ventricular hypertrophy, exogenous infusion of ANF induced an increase in venous irANF plasma levels of the same magnitude of the decrease evoked by LBNP and significantly reduced forearm vascular resistance. These data show that in hypertensive patients with left ventricular hypertrophy, sympathetic activation does not contribute to the vascular response to cardiopulmonary receptor unloading (-10 mm Hg LBNP). They also suggest that in these patients inhibition of ANF secretion may play a role in the response to a low level of LBNP so that the peripheral vasoconstriction induced by cardiopulmonary receptor unloading is comparable to that observed in normal subjects despite the lack of appropriate sympathetic reflex vasoconstriction.

Adaptation, Physiological↗
PubMed1988

Cardiac function in systemic hypertension before and after reversal of left ventricular hypertrophy.

In 3 age- and sex-matched groups of subjects--15 normotensives, 15 hypertensives without left ventricular (LV) hypertrophy and 15 hypertensives with LV hypertrophy--the slopes of the regression line obtained by plotting the individual values of LV fractional shortening against the corresponding values of echocardiographic end-systolic stress were compared. The first 2 groups were studied only in control conditions while the third group was restudied after a 20% reduction in LV mass index induced by a long-term antihypertensive treatment and after a 3-week washout period. A significant relation between fractional shortening and end-systolic stress was found in all instances. The slope of this correlation was higher in normotensives (-0.251) and in hypertensives without LV hypertrophy (-0.232) (both p less than 0.01) than in hypertensives with ventricular hypertrophy (-0.079). In this latter group, the slope increased after the reversal of LV hypertrophy (-0.230, p less than 0.01) and remained unchanged (-0.202) at the end of the washout period. No difference was detectable between the slopes obtained in these patients after reversal of LV hypertrophy, both with the antihypertensive treatment on and off, and those of normotensives and hypertensives without LV hypertrophy. Thus, LV hypertrophy attenuates the influence of changes in afterload on LV function. Reversal of LV hypertrophy restores a fractional shortening end-systolic stress relation quite comparable to that found both in normotensives and in hypertensives before the development of LV hypertrophy.

Cardiomegaly↗
PubMed1988

Effects of chronic antihypertensive treatment with ketanserin versus metoprolol on blood pressure and large arteries' compliance in humans: a cross-over double-blind study.

The antihypertensive efficacy of a serotonin-receptor antagonist, ketanserin, was compared with that of a well-established antihypertensive drug, metoprolol, and their cardiac and forearm hemodynamic effects were investigated using echocardiography and bidimensional pulsed Doppler flowmetry, respectively. Twenty hypertensive subjects completed a double-blind, cross-over, randomized study using ketanserin and metoprolol. Two 5-week courses with ketanserin or metoprolol were preceded by a placebo period; the total duration of the study was 15 weeks. Despite a comparable efficacy in reducing systolic and diastolic blood pressure (about 10% of the basal value), the two drugs showed quite different effects on forearm hemodynamics. Ketanserin increased forearm blood flow and induced a significant decrease in forearm vascular resistance (from 141 +/- 16 to 75 +/- 11 mm Hg/mL/sec, P less than .01). Furthermore, this treatment was able to improve brachial artery compliance (from 1.89 +/- .3 to 3.2 +/- .3 cm4/dyne 10(-7), P less than .01). On the contrary, metoprolol did not modify forearm hemodynamics. Both drugs did not significantly modify cardiac performance, as evaluated by left ventricle circumferential fiber shortening. Cardiac output was increased by ketanserin (from 5.9 +/- .3 to 6.6 +/- .5 L/min, P less than .05) and fell during treatment with metoprolol (from 5.9 +/- .4 to 4.9 +/- .3 L/min P less than .01). Thus, the two drugs reduce blood pressure through different hemodynamic mechanisms and the effects of ketanserin on systemic and peripheral circulation seem more favorable.

Adult↗
PubMed1988

Reflex control of coronary vascular tone by cardiopulmonary receptors in humans.

To examine whether cardiopulmonary receptors participate in the reflex control of coronary vascular resistance, systemic and coronary hemodynamics were assessed before and during -10 mm Hg lower body negative pressure in eight normal subjects and eight hypertensive patients with left ventricular hypertrophy. In both study groups, lower body negative pressure induced a significant decrease in right atrial pressure, left ventricular filling pressure and cardiac output, an increase in systemic vascular resistance and no change in mean arterial pressure and heart rate. In normal subjects, there was also a significant increase in plasma norepinephrine concentration (from 294 +/- 39 to 421 +/- 47 pg/ml, p less than 0.01). This increase was accompanied by a reduction in coronary blood flow, assessed by the continuous thermodilution method (from 101 +/- 5 to 79 +/- 4 ml/min, p less than 0.05). An increase in coronary vascular resistance (from 0.865 +/- 0.1 to 1.107 +/- 0.1 mm Hg/ml per min, p less than 0.05) and in myocardial oxygen consumption was detected in normal subjects during cardiopulmonary baroreceptor unloading. In contrast, in hypertensive patients, -10 mm Hg lower body negative pressure failed to induce any change in plasma norepinephrine, coronary blood flow or vascular resistance. Intravenous propranolol administration caused no significant change in the systemic hemodynamic response to -10 mm Hg lower body negative pressure in either study group, but it did abolish the decrease in coronary flow and the increase in plasma norepinephrine, coronary vascular resistance and myocardial oxygen consumption observed in normal subjects in control conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Stable improvement in large artery compliance after long-term antihypertensive treatment with enalapril.

In 12 patients with mild or moderate essential hypertension we assessed by 2-D pulsed Doppler flowmetry the influence of a 6-month effective treatment with enalapril or atenolol on peripheral hemodynamics. The patients were studied in control conditions, at the end of the 6-month pharmacologic treatment, and 2 weeks after the withdrawal of the therapy. In spite of a comparable fall in blood pressure, the effects of the two drugs on forearm hemodynamics were quite different. Enalapril induced a fall in vascular resistance and an increase in brachial artery diameter, flow, and compliance, while atenolol failed to modify all these parameters. In the enalapril group the improvement in forearm vascular resistance and brachial artery compliance persisted after the 2-week washout period. This latter observation raises the possibility that enalapril may reverse structural changes in the large arteries.

Antihypertensive Agents↗
PubMed1988

Atrial natriuretic factor potentiates forearm reflex vasoconstriction induced by cardiopulmonary receptor deactivation in man.

Previous evidence suggests that atrial natriuretic factor (ANF) interferes with the autonomic control of circulation. In the present study we investigated whether ANF modulates forearm vasoconstriction reflexly induced by cardiopulmonary receptor unloading in man. For this purpose, the hemodynamic response to -20 mm Hg lower body negative pressure (LBNP) was assessed under control conditions and during the constant infusion of alpha-human ANF (0.5 micrograms/kg bolus followed by 0.05 micrograms/kg/min) in seven normal subjects. ANF infusion resulted in a slight reduction in blood pressure and right atrial pressure, did not modify heart rate or forearm vascular resistance, but significantly potentiated the reflex increase in forearm vascular resistance during LBNP (+25 +/- 9% under control conditions vs +40 +/- 12% during ANF, p less than .05). In an attempt to clarify the mechanisms underlying the enhanced reflex vasoconstriction during infusion of ANF, in five additional subjects we demonstrated that there was a comparable vascular reflex response to LBNP under control conditions and during nitroglycerin infusion at a dose that induced a reduction in atrial pressure comparable to that observed during ANF. Finally, in seven additional subjects we found that ANF infusion did not alter the reflex hemodynamic responses elicited by carotid baroreceptor unloading induced by a +60 mm Hg increase in external neck pressure. We conclude that during the infusion of a pharmacologic dose of ANF the reflex forearm vasoconstriction in response to selective cardiopulmonary receptor unloading is potentiated. This effect does not seem to be related to the hemodynamic actions of the peptide or to interference with the sympathetic control of peripheral circulation.

Adult↗
PubMed1988

Effects of moderate low sodium/high potassium diet on essential hypertension: results of a comparative study.

It is generally accepted that a significant restriction in sodium intake can lower blood pressure in hypertensive patients and more recently it has also been suggested that a high potassium intake can exert an antihypertensive effect. We have therefore, conducted a double-blind, randomized, cross-over study to evaluate the antihypertensive efficacy of the combination of a modest dietary sodium restriction and a high potassium intake in hypertensive patients of mild and moderate degrees. During the modest sodium (100 mmol/day)/high potassium (130 mmol/day) diet the blood pressure was significantly reduced (-17/-6 mmHg) when compared to the normal diet (160 mmol Na/day and 80 mmol K/day). The blood pressure reduction did not interfere with hemodynamic and humoral responses to dynamic exercise. The modest reduction in sodium intake and increase in potassium content in the diet was well tolerated by the patients.

Adult↗
PubMed1987

[Regulation of coronary circulation in patients with hypertensive cardiopathy: role of ventricular mechanoreceptors].

In order to assess the involvement of the cardiopulmonary receptors in the regulation of the coronary circulation, changes in coronary resistance produced by the application of a -10 mmHg pressure to the lower body were studied in 6 healthy subjects and 6 patients with arterial hypertension and left ventricular hypertrophy. The results show that the inhibition of the ventricular receptors significantly increases coronary resistance and that this reflex response is eliminated in hypertensive patients with ventricular hypertrophy. The results show that the inhibition of the ventricular receptors significantly increases coronary resistance and that this reflex response is eliminated in hypertensive patients with ventricular hypertrophy.

Adult↗
PubMed1987

Effects of celiprolol on systemic and forearm circulation in hypertensive patients: a double-blind cross-over study versus metoprolol.

The antihypertensive efficacy of a new beta-receptor blocking agent, celiprolol, was compared with that of a well-established antihypertensive drug, metoprolol. Their systemic and forearm hemodynamic effects were investigated using echocardiography and two-dimensional pulsed Doppler flowmetry, respectively. Twenty hypertensive patients completed a double-blind, cross-over, randomized study using celiprolol and metoprolol. Two six-week courses with celiprolol or metoprolol were preceded and followed by a two-week placebo period; the total duration of the study was 18 weeks. In spite of a comparable efficacy in reducing systolic and diastolic blood pressure (about 10% of the basal value), the two drugs showed quite different systemic and regional hemodynamic effects. Celiprolol induced a significant decrease in forearm vascular resistance (from 157 +/- 17 to 113 +/- 13 mm Hg/mL/s, P less than .01) and total peripheral resistance (from 1596 +/- 90 to 1398 +/- 91 dyne.s.cm-5, P less than .05) whereas cardiac output remained unchanged and forearm blood flow increased. Metoprolol reduced cardiac output (from 6.5 +/- 3 to 5.7 +/- 3 L/min, P less than .05), through a reduction in heart rate, since stroke volume was unchanged. Both drugs did not significantly modify cardiac performance, as evaluated by left ventricle fractional shortening and ejection fraction. Thus, the two drugs seem to reduce blood pressure through different hemodynamic mechanisms.

Adrenergic beta-Antagonists↗
PubMed1987

Beta blockers and left ventricular hypertrophy in hypertension.

It is now generally accepted that hypertension-induced left ventricular hypertrophy (LVH) represents a phenomenon of multifactorial origin. Antihypertensive therapy with beta-blocking drugs influences most of the factors involved in the control of left ventricular mass. Therefore, although initial animal experiments yielded conflicting results, it is not surprising that a great deal of evidence has been accumulated in clinical studies showing that successful long-term antihypertensive treatment with beta blockers induces regression of LVH in hypertensive subjects. Differences in molecular structure among various beta-blocking agents do not seem to influence this property. On the contrary, the question of whether reversal of LVH represents a beneficial or harmful byproduct of antihypertensive treatment with beta blockers is still unanswered. Animal and clinical studies suggest that left ventricular systolic function is unchanged or even improved after regression of LVH, whereas the ability of the heart to withstand recurrence of hypertension is slightly reduced. Furthermore, development of LVH in hypertensive subjects is associated with abnormalities in diastolic function which are not reduced by reversal of LVH induced by antihypertensive treatment with beta blockers.

Adrenergic beta-Antagonists↗
PubMed1987

Hemodynamic and hormonal effects of atrial natriuretic factor in patients with essential hypertension.

Hemodynamic and hormonal effects of two graded infusions of alpha-human-(1-28)-atrial natriuretic factor (0.5 microgram/kg prime followed by 0.05 microgram/kg per min for 20 minutes and by 0.1 microgram/kg per min for 20 minutes) were evaluated in 13 patients with mild to moderate essential hypertension. The lower dose of atrial natriuretic factor did not change significantly any of the considered variables, although it tended to reduce aortic mean blood pressure (from 132.6 +/- 5.3 to 125.5 +/- 4.6 mm Hg), cardiac index (from 3.67 +/- 0.2 to 3.54 +/- 0.18 liters/min per m2) and forearm vascular resistance (from 178.6 +/- 15 to 148.3 +/- 10 mm Hg/ml per s). The higher dose of atrial natriuretic factor significantly reduced mean aortic pressure (118.6 +/- 5 mm Hg), cardiac index (3.29 +/- 0.16 liters/min per m2) and stroke volume index (from 45.9 +/- 2.6 to 38.9 +/- 3 ml/m2) and slightly decreased pulmonary wedge pressure, whereas both total peripheral resistance and forearm vascular resistance were not modified. With this latter dose a reduction in aortic pressure was observed in all patients at the steady state, and this was associated with a fall in stroke volume index in 10 of the 13 patients and with a reduction in total peripheral resistance in only 6 patients. Heart rate and right atrial and pulmonary pressures did not change during infusion of atrial natriuretic factor. Plasma renin activity was only slightly reduced by atrial natriuretic factor, whereas plasma norepinephrine rose significantly (from 233 +/- 34 to 330 +/- 58 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Effects of coronary occlusion on arterial baroreflex control of heart rate and vascular resistance.

This study was planned to assess whether circumflex coronary occlusion (CO) impairs the arterial baroreflex control of heart rate (HR) and hindlimb vascular resistance (HVR), and to determine the mechanisms involved in the mediation of these phenomena. Increasing doses of phenylephrine and nitroglycerin were given intravenously to anesthetized dogs with a constant flow-perfused hindlimb before and during 30-s CO. The reflex responses were assessed by the changes in HR and hindlimb perfusion pressure evoked by changes in arterial pressure following phenylephrine and nitroglycerin administration. During CO, there was an attenuation of the reflex control of HR and HVR as compared with control conditions. The application of lidocaine on the left ventricular epicardial surface was able to prevent the effect of CO on both the baroreflex responses. The intravenous administration of atropine prevented only the impairment in arterial baroreflex control of HR induced by CO. After the injection of phentolamine into the perfused hindlimb, the baroreflex had no effect on HVR either before or during CO. Finally, intravenous administration of propranolol failed to modify the effect of CO on both the baroreflex responses. These data indicate that CO attenuates the arterial baroreflex control of both HR and HVR through the stimulation of left ventricular receptors. The effect on HR is mediated by the parasympathetic system, whereas the effect on HVR is due to sympathetic efferents.

Animals↗
PubMed1987

Impaired control of vasopressin release in hypertensive subjects with cardiac hypertrophy.

The effects of graded lower body negative pressure (-10 and -40 mm Hg) on vascular resistance and plasma vasopressin, norepinephrine, and renin activity were assessed in seven hypertensive subjects with left ventricular hypertrophy and seven sex-matched and age-matched normotensive subjects. In both groups increasing levels of lower body negative pressure induced a progressive decrease in right atrial pressure and an increase in vascular resistance. In normal subjects plasma vasopressin, norepinephrine, and renin activity were progressively raised, whereas only the higher level of stimulation increased plasma renin activity, norepinephrine, and vasopressin in hypertensive subjects. Propranolol induced a significant increase in plasma vasopressin in normal subjects (from 1.3 +/- 0.1 to 2.0 +/- 0.1 pg/ml; p less than 0.05) but not in hypertensive subjects. In this latter condition -10 mm Hg lower body negative pressure failed to increase plasma vasopressin, norepinephrine, and renin activity in normal subjects. Propranolol abolished the change in plasma renin activity in both groups, reduced the increase in vascular resistance induced by -40 mm Hg lower body negative pressure in normotensive subjects, but did not modify the rise in vasopressin elicited by this stimulus in normal subjects or the humoral and hemodynamic reflex responses evoked in hypertensive subjects. These results suggest that cardiopulmonary receptors are involved in the control of vasopressin release in normal subjects, whereas in hypertensive subjects with left ventricular hypertrophy, this control is altered because of an impaired function of cardiopulmonary receptors.

Adult↗
PubMed1987

Changes in left ventricular anatomy and systemic hemodynamics induced by antihypertensive therapy with indenolol.

In 20 patients with mild or moderate essential hypertension who responded favorably to indenolol antihypertensive therapy, echocardiography was performed in the basal condition and 6 and 12 months after the beginning of permanent antihypertensive treatment. Indenolol induced a significant decrease in blood pressure, from a basal value of 170 +/- 3/100 +/- 8 mmHg to 142 +/- 4/87 +/- 2 mmHg after 6 months (p less than 0.01) and to 133 +/- 4/84 +/- 2 mmHg after 1 year (p less than 0.01), and in heart rate, from 72 +/- 5 to 61 +/- 3 bpm after 6 months (p less than 0.01) and to 60 +/- 2 bpm after 1 year (p less than 0.01). Simultaneously, there was a significant reduction in cardiac output (from 6.3 +/- .4 to 5.7 +/- .2 liters/min after 6 months, p less than 0.05, and to 5.6 +/- .2 liters/min after 1 year, p less than 0.01), due to a reduction in heart rate, increased stroke volume, and improved left ventricular performance after indenolol. Total peripheral resistance was also reduced, although statistical significance was not attained. However, a significant inverse correlation was found between the initial value of cardiac output and total peripheral resistance and the changes in these parameters induced by indenolol treatment (cardiac output: r = -0.824 and -0.855, total peripheral resistance: r = -0.876 and -0.899 at 6- and 12-month controls, respectively, all p less than 0.001). Finally, there was a parallel decrease in left ventricular wall and septal thickness and estimated left ventricular mass in patients with left ventricular hypertrophy, whereas no change in left ventricular anatomy could be detected in patients with normal left ventricular mass.

Adult↗
PubMed1987

Influence of atrial natriuretic factor on forearm reflex vasoconstriction induced by cardiopulmonary or arterial receptor unloading.

We studied the influence of atrial natriuretic factor (ANF) infusion on the reflex increase in forearm vascular resistance in normotensive subjects. Reflex vasoconstriction was induced by cardiopulmonary receptor unloading [lower body negative pressure (LBNP), -20 mmHg for 15 min] or by carotid baroreceptor deactivation (+60 mmHg increase in external neck pressure by a pneumatic neck-chamber). Atrial natriuretic factor induced a significant increase in the reflex forearm vasoconstriction to LBNP, but did not modify systemic and regional reflex haemodynamic responses to carotid baroreceptor deactivation. These results suggest that ANF has important interactions with the neural control of peripheral circulation. In addition, the study shows that the peptide causes a selective potentiation of the reflex vasoconstrictor response evoked by cardiopulmonary receptor unloading.

Adult↗
PubMed1986

Impaired responsiveness of the ventricular sensory receptor in hypertensive patients with left ventricular hypertrophy.

We studied the control of forearm vascular resistance (FVR) by cardiopulmonary receptors in seven patients with hypertension and left ventricular hypertrophy (LVH) and in seven normotensive control subjects. Increasing levels of lower body negative pressure (LBNP) (-10 and -40 mm Hg) induced a progressive decrease in central venous pressure (CVP) and an increase in FVR. The changes in these two variables were correlated both in normal subjects and patients with hypertension (slope for normal subjects = -29.9, for patients with hypertension = -40.3, NS). After propranolol, there was a significant reduction in the increase in FVR induced by -40 mm Hg LBNP in normal subjects (+107 +/- 5 vs +129 +/- 15 mm Hg/ml/sec, p less than .05) but not in patients with hypertension. Consequently, the slope of the delta CVP/delta FVR regression was reduced in normal subjects (-20.6, p less than .01) but not in patients with hypertension. In another seven normal subjects and seven patients with hypertension and LVH we assessed the effects of -10 and -40 mm Hg LBNP on left ventricular filling pressure (LVFP). LBNP induced similar changes in CVP, LVFP, and total peripheral resistance both in normal subjects and in patients with hypertension. Propranolol failed to modify the effects of LBNP on CVP and LVFP in both groups and reduced the response of total peripheral resistance to -40 mm Hg LBNP only in normal subjects. Propranolol did not reduce the response of FVR to the cold pressor test and sustained handgrip or the arterial baroreflex response to the injection of phenylephrine and increased neck tissue pressure. Thus, hypertension-induced LVH seems to be associated with a selective impairment of the left ventricular sensory receptors.

Adult↗
PubMed1986

Effects of lower body negative pressure in hypertensive patients with left ventricular hypertrophy.

We studied the response of forearm vascular resistance to lower body negative pressure (LBNP) at -10 and -40 mmHg in seven established hypertensives with left ventricular hypertrophy (LVH) and seven age-matched normotensive controls. To evaluate the specific role of ventricular baroreceptors, we also investigated the effects of propranolol on the reflex response. Under control conditions, graded LBNP induced a progressive decrease in central venous pressure (CVP) and increased forearm vascular resistance. Changes in CVP and forearm vascular resistance were inversely correlated both in controls (r = -0.944) and in hypertensives (r = -0.960), P less than 0.001 for both. No difference was found between the regression slopes obtained for the two groups (normotensives, -30; hypertensives, -40; NS). After propranolol there was a significant reduction in the increase in forearm vascular resistance induced by -40 mmHg LBNP in normotensives but not in hypertensives. Consequently, the slope of the regression delta CVP/delta forearm vascular resistance was reduced in normotensives (-21) but not in hypertensives. In contrast, propranolol did not attenuate the vasoconstrictor response to other stimuli. Left ventricular hypertrophy therefore seems to be associated with changes in the role of the different cardiopulmonary receptor areas during mediation of the haemodynamic response to stimulated orthostatic stress.

Adult↗