Pulmonary vascular overreactivity in systemic hypertension. A pathophysiological link between the greater and the lesser circulation

Autonomic control of the pulmonary circulation: Implications for pulmonary hypertension

The autonomic regulation of the pulmonary vasculature has been under-appreciated despite the presence of sympathetic and parasympathetic neural innervation and adrenergic and cholinergic receptors on pulmonary vessels. Recent clinical trials targeting this innervation have demonstrated promising effects in pulmonary hypertension, and in this context of reignited interest, we review autonomic pulmonary vascular regulation, its integration with other pulmonary vascular regulatory mechanisms, systemic homeostatic reflexes and their clinical relevance in pulmonary hypertension. The sympathetic and parasympathetic nervous systems can affect pulmonary vascular tone and pulmonary vascular stiffness. Local afferents in the pulmonary vasculature are activated by elevations in pressure and distension and lead to distinct pulmonary baroreflex responses, including pulmonary vasoconstriction, increased sympathetic outflow, systemic vasoconstriction and increased respiratory drive. Autonomic pulmonary vascular control interacts with, and potentially makes a functional contribution to, systemic homeostatic reflexes, such as the arterial baroreflex. New experimental therapeutic applications, including pulmonary artery denervation, pharmacological cholinergic potentiation, vagal nerve stimulation and carotid baroreflex stimulation, have shown some promise in the treatment of pulmonary hypertension.

The effect of stimulation and unloading of baroreceptors on cough in experimental conditions

Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms that contributes to the sensitization of cough pathways at the peripheral and/or central level via neuroplasticity and it manifests most often as augmented coughing. Cardiorespiratory coupling is an important mechanism responsible for a match between oxygenation and cardiac output and bidirectional relationships exist between respiration and cardiovascular function. While the impact of cough with the robust swings of the intrathoracic pressure on haemodynamic parameters and heart electrophysiology are well characterized, little is known about the modulation of cough by haemodynamic parameters - mainly the blood pressure. Some circumstantial findings from older animal studies and more recent sophisticated analysis confirm that baroreceptor stimulation and unloading alters coughing evoked in experiments. Clinical relevance of such findings is not presently known.

Artemisinin Improves Acetylcholine-Induced Vasodilatation in Rats with Primary Hypertension

Purpose

Endothelial dysfunction and the subsequent decrease in endothelium-dependent vascular relaxation of small arteries are major features of hypertension. Artemisinin, a well-known antimalarial drug, has been shown to exert protecting roles against endothelial cell injury in cardiac and pulmonary vascular diseases. The current study aimed to investigate the effects of artemisinin on endothelium-dependent vascular relaxation and arterial blood pressure, as well as the potential signalling pathways in spontaneously hypertensive rats (SHRs).

Methods

In this study, acetylcholine (ACh)-induced dose-dependent relaxation assays were performed to evaluate vascular endothelial function after treatment with artemisinin. Artemisinin was administered to the rats by intravenous injection or to arteries by incubation for the acute exposure experiments, and it was administered to rats by intraperitoneal injection for 28 days for the chronic experiments.

Results

Both acute and chronic administration of artemisinin decreased the heart rate and improved ACh-induced endothelium-dependent relaxation but negligibly affected the arterial blood pressure in SHRs. Incubation with artemisinin decreased basal vascular tension, NAD(P)H oxidase activity and reactive oxygen species (ROS) levels, but it also increased endothelial nitric oxide (NO) synthase (eNOS) activity and NO levels in the mesenteric artery, coronary artery, and pulmonary artery of SHRs. Artemisinin chronic administration to SHRs increased the protein expression of eNOS and decreased the protein expression of the NAD(P)H oxidase subunits NOX-2 and NOX-4 in the mesenteric artery.

Conclusion

These results indicate that treatment with artemisinin has beneficial effects on reducing the heart rate and basal vascular tension and improving endothelium-dependent vascular relaxation in hypertension, which might occur by increasing eNOS activation and NO release and inhibiting NAD(P)H oxidase derived ROS production.

Right ventricular systolic function in Nigerians with heart failure secondary to hypertensive heart disease

Background

Right ventricular (RV) dysfunction has been shown to be a major contributor to the adverse outcomes in subjects with heart failure. Few studies evaluating the right ventricle in heart failure subjectshave been carried out in Sub-Saharan Africa. This studywas therefore designed to evaluate the right ventricular systolic function in subjects with heart failure secondary to hypertensive heart disease presenting to the University College Hospital, Ibadan Nigeria.

Methodology

Seventy-six subjects with heart failure secondary to hypertension and 92 normal controls underwent clinical, electrocardiographic and echocardiographic evaluation. Indices of right ventricular systolic function that were measured include tricuspid annular plane systolic excursion (TAPSE), tissue Doppler derived tricuspid peak systolic lateral annulus velocity(S′) and right ventricular fractional areachange(RVFAC).

Results

Sixty-two (81.6%) heart failure subjects had right ventricular systolic dysfunction, 31(40.8%) had abnormal TAPSE, 42(55.5%) had abnormal S′ while 49(64.5%) had abnormal RVFAC. Elevated pulmonary artery systolic pressure was found in 25(32.9%) of the subjects. There was no relationship between the indices of right ventricular systolic function and the estimated systolic pulmonary artery pressures. The independent predictor of right ventricular systolic dysfunction was the right atrial size.

Conclusion

Right ventricular systolic function is impaired in patients with heart failure secondary to hypertensive heart disease. There is no relationship between the indices of right ventricular systolic function and systolic pulmonary artery pressure. Further studies are needed to assess right ventricular systolic function in Nigerians.

Right ventricular remodelling in mild hypertensive patients: role of left ventricular morpho-functional parameters

Previous studies suggested that hypertensive patients with left ventricular (LV) hypertrophy display right ventricular (RV) remodelling. Few data are available about RV remodelling in naive hypertensives without severe cardiac organ damage. Our aim was to evaluate the relationship between RV and LV morpho-functional parameters in never-treated patients with grade 1 hypertension and whether central blood pressure (CBP), inflammatory and metabolic parameters are potentially associated with RV remodelling. 150 never-treated subjects without evidence of diabetes or other cardiovascular diseases were enrolled in our study. We recruited 100 patients with mild hypertension (twenty-four hours blood pressure (24 h BP) ≥ 130/80 mmHg) and 50 normotensive subjects matched for gender, age and body mass index. To estimate the LV/RV parameters, we performed echography as well as arterial tonometry to assess pulse wave analysis/velocity (PWA/PWV). We found 24 h BP, CBP and PWV were higher in hypertensive patients than in normotensives. In addition, LV mass index was higher in hypertensives, and greater RV free wall thickness was observed (5.3 ± 1.4 vs 4.6 ± 1.2 mm, P = 0.02). RV thickness correlated with interventricular septum (IVS), systolic CBP and RV E' (r = 0.50, P = 0.0001, r = 0.30, P = 0.003, r = -0.24, P = 0.015); linear regression analysis showed a correlation with only IVS (β = 0.39, P = 0.001). RV E' was correlated with IVS, LV E' and systolic CBP (r = -0.35, P = 0.0001, r = 0.25, P = 0.012, r = -0.24, P = 0.019); the correlation with IVS and LV E' (β = -0.310, P = 0.001; β = 0.27, P = 0.004) was confirmed by linear regression analysis. Our study shows RV remodelling is mostly correlated with IVS thickness, supporting the ventricular interdependence hypothesis.

Angiotensin-(1-7) induced vascular relaxation in spontaneously hypertensive rats

Enhanced vasoconstriction and decreased vasodilatation due to endothelial dysfunction contribute to the progression of hypertension. Angiotensin (Ang)-(1-7) plays important roles in regulating the cardiovascular activity. The current study aimed to investigate the roles of Ang-(1-7) in modulating blood pressure, vascular tension and its signal pathway in spontaneously hypertensive rats (SHR). The effects of intravenous injection of drugs were determined in rats with anesthesia in vivo. Mesenteric artery (MA), coronary artery (CA) and pulmonary artery (PA) were isolated from rats and isometric tension measurements in arteries were performed. Compared with Wistar-Kyoto rats (WKY), the high K⁺ induced vasoconstriction was enhanced and acetylcholine-induced vasodilatation were attenuated in the MA, CA and PA in SHR. Intravenous injection of Ang-(1-7) decreased, while A-779 increased mean arterial pressure and abolished the hypotensive effect of Ang-(1-7) in SHR. Ang-(1-7) caused dose-dependent relaxation in MA, CA and PA in SHR, which was inhibited by pretreatment with Mas receptor antagonist A-779, nitric oxide (NO) synthase inhibitor l-NAME, guanylate cyclase inhibitor ODQ and protein kinase G (PKG) inhibitor DT-2. The Mas receptor expression, NO, cGMP and PKG levels of the three above arteries of SHR were lower than that of WKY. Ang-(1-7) increased the NO, cGMP and PKG levels in arteries from SHR, which was blocked by A-779. Activation of the Mas receptor by Ang-(1-7) relaxes the MA, CA, and PA through the NO-cGMP-PKG pathway, which contributes to the decrease of arterial pressure in SHR.

Right heart remodeling induced by arterial hypertension: Could strain assessment be helpful?

Left ventricular structural and functional changes in patients with arterial hypertension are well established. However, the influence of arterial hypertension on right ventricular (RV) remodeling is still being investigated. The introduction of strain analysis provided an insight into RV function and mechanics. Previous research has demonstrated the predictive value of RV longitudinal strain in patients with various cardiovascular conditions, such as pulmonary hypertension, heart failure, congenital heart diseases, and valvular disease. Nowadays, we are aware of the fact that conventional echocardiographic methods usually do not provide necessary information about RV dysfunction in patients with arterial hypertension, which is why the evaluation of new parameters that could detect RV subtle changes in hypertension is essential. The present review article is an overview of the main principles of RV deformation and a summary of the current knowledge and clinical significance of RV strain in patients with arterial hypertension.

Right ventricular hypertrophy in systemic hypertension: an updated review of clinical studies

AIM

Experimental and clinical evidence supports the view that right ventricular hypertrophy (RVH) may parallel left ventricular hypertrophy in systemic hypertension; a comprehensive analysis of this issue, however, is lacking. Thus, we analyzed the literature in order to provide an updated information on the right ventricular structural changes associated to systemic hypertension.

DESIGN

A literature search using the key words 'right ventricle' 'right ventricular hypertrophy', 'biventricular hypertrophy' 'right and left ventricular hypertrophy'. 'hypertension', 'echocardiography' was performed in order to identify relevant articles. Full articles published in English language in the last three decades reporting studies in adult hypertensive individuals were considered.

RESULTS

A total of 13 studies, including 1290 untreated (45%) and treated hypertensive patients and 259 normotensive controls, were considered. Overall, in hypertensive individuals right ventricular wall was thicker than in normotensive counterparts (standardized difference 1.3 mm, P < 0.001). RVH prevalence consistently varied among studies (17.0-80.0%) with an average of 28.6% in the pooled population. This was also the case for LVH prevalence rates (9.0-100%) with an average value of 30.6%.

CONCLUSION

Clinical studies consistently indicate that RVH is a common cardiac phenotype in systemic hypertension. As this finding is based on a limited number of cross-sectional studies including small population samples, further investigations are needed to determine the clinical utility and prognostic value of this phenotype in clinical practice.

Carotid atherosclerosis and right ventricular diastolic dysfunction in a sample of hypertensive Nigerian patients

AIM

To determine the association of carotid atherosclerosis and right ventricular diastolic dysfunction (DD) among treated hypertensive Nigerian patients.

METHODS

This was a single center cross-sectional study performed at the Cardiology Clinic of LAUTECH Teaching Hospital, Ogbomoso, Nigeria between January and December 2012. The study included 122 hypertensive Nigerians (mean age, 57.3±14.7 years, 36.9% women). Patients' clinical, demographic, and echocardiographic parameters were obtained. Diastolic dysfunction was assessed with the trans-tricuspid Doppler flow.

RESULTS

Patients with DD were significantly older than those with normal diastolic function. Mean and maximum carotid intima media thickness measurements were significantly higher among patients with right ventricular DD than in those with normal diastolic function. Mean systolic blood pressure (148.3±31.9 vs 128.0±2.8 mm Hg, P=0.049) and interventricular septal thickness in diastole (12.8±2.3 vs 11.6±2.8 mm, P=0.048) were significantly higher and tricuspid annular pulmonary systolic excursion (33.6±4.9 vs 23.0±4.2 mm, P=0.035) was significantly lower in patients with right ventricular DD than in those with normal diastolic function. Carotid intima media thickness measurements were correlated with early trans-tricuspid Doppler flow and early transtricuspid diastolic flow/late right atrial transtricupsid diastolic flow ratio.

CONCLUSION

Right ventricular DD in hypertensive patients was significantly correlated with increased carotid atherosclerosis. Carotid intima media thickness measurements may therefore be a surrogate marker for DD in hypertensive subjects.

Metabolic syndrome and right ventricle: an updated review

The cluster of metabolic and hemodynamic abnormalities which characterize the metabolic syndrome (MS) is responsible for subclinical cardiac and extra-cardiac damage such as left ventricular hypertrophy, diastolic dysfunction, carotid atherosclerosis and microalbuminuria. The development of different non-invasive imaging methods enabled a detail investigation of right ventricular structure and function, and revealed that right ventricular remodeling followed changes in the left ventricular structure and function in patients with arterial hypertension, diabetes or obesity. Previous investigations also reported that the coexistence of two components of the MS induced more significant cardiac remodeling than the presence of only one MS risk-factor. The relationship between different components of the MS (increased blood pressure, abdominal obesity, increased fasting glucose level and dyslipidemia) and right ventricular remodeling could be explained by several hemodynamic and non-hemodynamic mechanisms. However, the association between right ventricular remodeling and the MS has not been sufficiently investigated so far. The aim of this article was to review recent articles focusing on the association between metabolic syndrome components and the metabolic syndrome itself with impairments in right ventricular structure and function assessed by different imaging techniques.

Effect of systemic hypertension on right ventricular morphology and function: an echocardiographic study

BACKGROUND

Hypertension is an important cardiovascular risk factor worldwide. It is associated with left ventricular hypertrophy (LVH). Both diastolic and systolic dysfunction may occur in hypertensive heart disease. The ventricles are structurally and functionally interdependent on each other. This was an echocardiographic study intended to describe the impact of left ventricular pressure overload and hypertrophy due to hypertension on right ventricular morphology and function.

METHODS

One hundred subjects with systemic hypertension and 50 age- and gender-matched normotensive control subjects were used for this study. Two-dimensional (2-D), M-mode and Doppler echocardiographic studies were done to evaluate the structure and function of both ventricles. Data analysis was done using the SPSS 16.0 (Chicago, Ill). Statistical significance was taken as p < 0.05.

RESULTS

Age and gender were comparable between the two groups. Hypertensive subjects had significantly increased left ventricular end-diastolic dimensions, posterior wall thickness, interventricular septal thickness, left atrial dimensions and left ventricular mass and index. The mitral valve E/A ratio was reduced among hypertensive subjects when compared to normal controls (1.15 ± 0.75 vs 1.44 ± 0.31, respectively; p < 0.05). A similar pattern was found in the tricuspid E/A ratio (1.14 ± 0.36 vs 1.29 ± 0.30, respectively; p < 0.05). Hypertensive subjects also had reduced right ventricular internal dimensions (20.7 ± 8.0 vs 23.1 ± 3.1 mm, respectively; p < 0.001) but similar peak pulmonary systolic velocity. The mitral e/a ratio correlated well with the tricuspid e/a ratio.

CONCLUSION

Systemic hypertension is associated with right ventricular morphological and functional abnormalities. Right ventricular diastolic dysfunction may be an early clue to hypertensive heart disease.

Prevalence and clinical correlates of right ventricular hypertrophy in essential hypertension

AIM

Right ventricular hypertrophy (RVH) has been reported to be a component of cardiac damage in systemic hypertension; this evidence, however, is based on small studies and major determinants of biventricular hypertrophy are still undefined. Thus, the prevalence and clinical correlates of RVH have been investigated in essential hypertension.

METHODS

A total of 330 untreated and treated uncomplicated essential hypertensives consecutively attending a hospital out-patient hypertension clinic were considered for the analysis. All individuals underwent a quantitative echocardiographic examination as well as extensive clinical and laboratory investigations. RVH was defined by an anterior RV wall thickness equal or higher than 3.1/3.0 mm/m2 in men and women, respectively, and left ventricular hypertrophy (LVH) by LV mass index equal or higher than 51/47g/m2.7 in men and women, respectively.

RESULTS

Overall, 114 (34.5%) patients fulfilled the criteria for LVH and 111 (33.6%) for RVH; normal cardiac morphology was observed in 164 patients (49.6%), isolated RVH in 52 (15.7%), isolated LVH in 55 (16.6%) and bi-ventricular hypertrophy in 59 (17.8%). In a logistic regression analysis, modifiable risk factors such as abdominal obesity (OR 3.41, CI 1.73-6.74, P = 0.0004), LV mid-wall fractional shortening (OR 2.48, CI 1.26-4.85, P = 0.008), fasting blood glucose (OR 2.47, CI 1.25-4.89, P = 0.009) and systolic blood pressure (OR 2.39, CI 1.19-4.82, P = 0.014) were the major independent correlates of biventricular hypertrophy.

CONCLUSION

RVH is commonly found in systemic hypertension and is associated with LVH (i.e., biventricular hypertrophy) in approximately one-fifth of the patients seen in a specialist setting. The clinical correlates of biventricular hypertrophy suggest that this phenotype is associated with a profile of very high cardiovascular risk.

Determinants of right ventricular pressure in mild hypertension

OBJECTIVE

Doppler echocardiography was used to define reference values and determinants of tricuspid regurgitation peak velocity (TRV) in hypertensive patients. A TRV value > 2.5 m/s is the threshold usually defining abnormal right ventricular systolic pressure.

DESIGN AND PATIENTS

Doppler echocardiography was performed in 320 consecutive uncomplicated hypertensive patients, without overt pulmonary or heart disease. Doppler echocardiography included LV mass measurement, LV inflow and pulmonary venous flow analysis, LV systolic function and TRV measurements.

RESULTS

Among 320 patients, 255 had normal TRV < 2.5 m/s and 65 had elevated TRV > or = 2.5 m/s. Compared with the normal TRV group, the elevated TRV group was older (60 versus 50 years, P < 0.0001), systolic blood pressure was higher (156 versus 151 mmHg, P = 0.02) and antihypertensive therapy was more frequent (68 versus 51%, P = 0.02); indexed LV mass was higher (45.4 versus 40.6 g/m2.7, P = 0.001), pulmonary D wave peak velocity was higher (42 versus 38 cm/s, P = 0.03). In univariate analysis, age was the most predictive variable of TRV (r = 0.36). In multivariate analysis, three variables were independently related to TRV: age, LV mass, pulmonary D wave (multiple r = 0.47).

CONCLUSION

In mild hypertension, TRV is independently related to age, and to a lesser extent, to LV morphology and LV filling pressure. In clinical practice, age should be taken into account to interpret TRV.

Blood pressure and plasma catecholamines in acute and prolonged hypoxia: effects of local hypothermia

This study measured the pressor and plasma catecholamine response to local hypothermia during adaptation to hypobaric hypoxia. Eight healthy men were studied at rest and after 10 and 45 min of local cooling of one hand and forearm as well as after 30 min of rewarming at sea level and again 24 h and 5 days after rapid, passive transport to high altitude (4,559 m). Acute mountain sickness scores ranged from 5 to 16 (maximal attainable score: 20) on the first day but were reduced to 0-8 by the fifth day. Systolic blood pressure, heart rate, and plasma epinephrine increased on day 1 at altitude compared with sea level but declined again on day 5, whereas diastolic and mean blood pressures continued to rise in parallel with plasma norepinephrine. With local cooling, an increased vasoactive response was seen on the fifth day at altitude. Very high pressures were obtained, and the pressure elevation was prolonged. Heart rate increased twice as much on day 5 compared with the other two occasions. Thoracic fluid index increased with cooling on day 5, suggesting an increase in pulmonary vascular resistance. In conclusion, prolonged hypoxia seems to elicit an augmented pressor response to local cooling in the systemic and most likely also the pulmonary circulation.

Doppler-derived pulmonary arterial systolic pressure in patients with known systemic arterial pressures

In the present study, we evaluated Doppler-derived systolic pulmonary artery pressure in 476 hypertensive patients. Clinical interpretation of systolic pulmonary arterial pressure should take into account age, body size, and systolic blood pressure values.

Pulmonary vascular reactivity in severe pulmonary hypertension associated with mixed connective tissue disease

Pulmonary vascular reactivity tests were performed in a young woman with mixed connective tissue disease and severe pulmonary hypertension. Vasoreactivity was documented in response to intravenous prostacyclin (PGI2), oral nifedipine, and inhaled nitric oxide, with quantitative differences. Nitric oxide produced a moderate lowering of pulmonary arterial pressure and resistance without any deleterious systemic effect. The use of nitric oxide in testing for pulmonary vasoreactivity merits further evaluation.

Neural influences on the human pulmonary circulation as a defence reaction to volume depletion

The role of the autonomic nervous system in the regulation of pulmonary vasomotility in man is unsettled and great emphasis is usually given to changes in flow as the main regulating mechanism. In order to simulate hypovolemia, which might reduce the mechanical influence of flow and disclose a neural mechanism, we decreased venous return through balloon distention in the inferior vena cava in 12 normal subjects, during right heart catheterization performed for diagnostic purposes. Caval obstruction was graduated to reduce cardiac output, right atrial and pulmonary arterial pressures, without altering systemic arterial pressure and heart rate. The sympathetic nervous system was activated by arithmetic and cold pressor tests. During the former, the increase in cardiac output was more than halved by venous return restraint, as compared to the unrestrained condition, and clear pulmonary vasoconstriction, instead of vasodilatation, was observed. During the cold test, cardiac output remained almost steady, in the absence as in the presence of balloon expansion. In both conditions pulmonary arteriolar resistance rose, but in the latter this increase was more than doubled. This study suggests that the autonomic nervous system is involved in the regulation of pulmonary vasomotility in man, its role being unveiled when the mechanical influence of flow is reduced by mimicking a hypovolemic state.

Enhanced hypoxic pulmonary vasoconstriction in hypertension

In this study, we tested the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension. The hypothesis took origin from the following two considerations: alveolar hypoxia constricts the pulmonary vessels by enhancing the Ca2+ penetration across sarcolemma of the smooth muscle cells and systemic high blood pressure is associated with an elevation of tone and reactivity of the lung vessels, which seems to depend on an excessive cytosol free Ca2+ concentration due to alterations in sodium handling and in the Na+-Ca2+ exchange system. These considerations suggest the possibility that the disorders in the biochemistry of smooth muscle contraction in hypertension facilitate the rise of cytosol Ca2+ concentration during alveolar hypoxia, thus resulting in a potentiation of the vasoconstrictor properties of this stimulus. In 43 hypertensive and 17 normotensive men, pulmonary arteriolar resistance has been evaluated during air respiration and after 15 minutes of breathing 17%, 15%, and 12% oxygen in nitrogen. Curves relating changes in pulmonary arteriolar resistance to oxygen breathing contents had similar configuration in the two populations but in hypertension were steeper and significantly shifted to the left, reflecting a lower threshold and an enhanced reactivity. This pattern was not related to differences in severity of the hypoxic stimulus, plasma catecholamine concentration, or hypocapnia and respiratory alkalosis induced by hypoxia and probably was not mediated through alpha-receptor activation. Calcium channel blockade with nifedipine was able to almost abolish both the normotensive and the hypertensive pulmonary vasoconstriction reaction. These findings support the hypothesis that hypoxic pulmonary vasoconstriction may be enhanced in systemic hypertension.

Combined hemodynamic overload of the left and right ventricles as a possible cause of interventricular septum preponderance in high blood pressure

We tested whether overload of the two ventricles may be associated with a preponderance of interventricular septum in patients with high blood pressure. The rationale is that the septum is shared by the greater and lesser circulation and that in hypertension the latter shows the same qualitative hemodynamic alterations as the former. Among 65 hypertensive patients, 40 (group 1) showed (echo) posterior wall thickness within the mean +/- 1 SD of 62 normal subjects, and 25 (group 2) had a posterior wall thickness exceeding the mean + 1 SD of the normal population. Both groups were subdivided into subgroups A and B, which included patients whose ventricular septum was similar to (within the mean + 1 SD) and thicker than (exceeding the mean + 1 SD) the posterior wall thickness in the corresponding group, respectively. Resting differences in systemic and pulmonary pressure and vascular resistance among subgroups 1A, 1B, and 2A were not significant; however, in subgroup 2B these variables exceeded those in the other subgroups to a significant extent. During cold pressor testing (CPT) the levels reached and the changes in pressure and resistance from baseline values in both circuits were much greater in subgroups B than in subgroups A. The baseline plasma norepinephrine value showed a trend toward an increase from subgroup 1A to 1B and from subgroup 2A and 2B; during CPT norepinephrine invariably changed and in subgroups B it rose significantly more than in subgroups A. It was not determined whether this caused the hemodynamic overload in subgroups B.(ABSTRACT TRUNCATED AT 250 WORDS)

The pulmonary circulation in essential systemic hypertension

Seventy-one men, ages 16 to 59 years, were referred for systemic hypertension, which was without detectable cause and with limited organ damage (World Health Organization stages I to II). They performed a graded exercise test on the bicycle ergometer in the sitting position. Mean brachial intraarterial pressure, mean pulmonary artery and wedge pressures and cardiac output (Fick method) were measured. At rest mean brachial artery pressure ranged from 72 to 168 mm Hg. Mean pulmonary wedge pressure was significantly (p less than 0.05) related to mean brachial artery pressure at rest, at submaximal work (50 watts) and at the end of exercise (161 +/- 42 [standard deviation] watts). In each subject pulmonary vascular resistance was calculated as the slope of the relation between the pressure gradient across the pulmonary circulation and cardiac output from data at rest, at 50 watts and at the end of exercise; mean critical closing pressure was calculated as the intercept of this relation. Pulmonary vascular resistance averaged 0.63 +/- 0.37 mm Hg/liter/min and was significantly related to age (r = 0.28, p less than 0.05) but not to rest brachial artery pressure (r = 0.14) or pulmonary wedge pressure (r = 0.09, difference not significant for both). The mean critical closing pressure averaged 6.1 +/- 4.0 mm Hg and was not related to brachial artery pressure (r = -0.08) or to age (r = -0.18, difference not significant for both). It is concluded that there is neither a primary nor a secondary effect of systemic hypertension on the pulmonary vasculature in patients with World Health Organization stages I to II essential hypertension.

Correlates of plasma atrial natriuretic factor in health and hypertension

Plasma concentrations of atrial natriuretic factor (ANF) were compared in normotensive subjects and subjects with untreated, uncomplicated essential hypertension (n = 21 pairs) matched for age, sex, and race. Plasma peptide values were slightly greater (45 +/- 3 vs 36 +/- 3 pg/ml; p less than 0.05) in the hypertensive group. On univariate analysis, age (r = 0.52, n = 47, p less than 0.001) and creatinine clearance (r = -0.30, n = 47, p less than 0.05) were significantly related to plasma ANF concentrations, but arterial pressure was not (r = 0.14, n = 47), in an extended group of normal subjects. In contrast, plasma ANF values were related to arterial pressure in both an extended group of subjects with untreated essential hypertension (r = 0.54, n = 38, p less than 0.001) and in our total heterogeneous pool of hypertensive patients (r = 0.46, n = 79, p less than 0.001), but weak positive associations with age and inverse relationships with creatinine clearance were not statistically significant in either hypertensive group. Similar weak inverse relationships between plasma ANF values and renin-angiotensin-aldosterone system activity were found in both normal and hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in systemic and pulmonary vascular reactivity in hypertension following nifedipine and verapamil

Excessive vascular tone and overresponsiveness to adrenergic stimuli characterize the hemodynamics of the greater and the lesser circulation in hypertension. We tested whether calcium entry blockade with verapamil (11 cases) or nifedipine (11 cases) may improve the vascular regulation in high blood pressure. Mental arithmetic and cold were used as adrenergic activators. The former stimulus produced obvious elevation of epinephrine plasma concentration, increase of cardiac output (CO), slight systemic vasodilatation, pulmonary vasoconstriction, and rise of blood pressure in both circuits. After calcium antagonists, the epinephrine reaction to the arithmetic test was significantly attenuated, variations in CO and systemic blood pressure were unchanged, pulmonary vasoconstriction was abolished, and the pressure rise in the lesser circuit was halved. The cold pressor test increased norepinephrine plasma concentration (NE pc), systemic and pulmonary blood pressure, and vascular resistance and did not alter CO. The attained NE pc during cold was unvaried after verapamil and significantly enhanced after nifedipine; pressure and resistance responses of the two circuits were almost unchanged after the former, whereas systemic and pulmonary vascular resistance rises were importantly attenuated after the latter compound, resulting in much lower pressure reactivity. A modulation of the sympathoadrenal reaction, per se, can explain changes in the systemic and in the pulmonary vasomotion with calcium blockade during arithmetic. It would seem that after verapamil the sympathetic system was still activated during cold to such an extent as to maintain the same vasoconstrictor potency. NE pc suggests that the sympathetic discharge was not reduced by nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary vascular supersensitivity to catecholamines in systemic high blood pressure

Pulmonary pressure and arteriolar resistance are elevated in uncomplicated primary systemic hypertension. This study was carried out in 16 men with this form of hypertension and in 9 healthy men to compare 1) their pulmonary vascular reactivity to endogenous catecholamines released during mental arithmetic and cold pressor tests, and 2) the dose-response relation to exogenous epinephrine and norepinephrine. Arithmetic and cold pressor tests were associated, respectively, with a predominant increase in plasma epinephrine and norepinephrine concentration; changes were significantly greater in hypertensive men. During the two tests, pulmonary arteriolar resistance in the normotensive group was reduced by 13% and augmented by 7% of baseline, respectively, whereas it was raised by 31 and 70%, respectively, in the hypertensive group. In normal subjects, the dose (microgram)-response (delta dynes) relation to epinephrine was 1 = -4, 2 = -9, 3 = -9 and 4 = -10; to norepinephrine it was 2 = +3, 4 = +6, 6 = +7 and 8 = +7. In hypertensive patients, the respective relations were 1 = +18, 2 = +44, 3 = +59 and 4 = +77; and 2 = +39, 4 = +54, 6 = +76 and 8 = +98. Group differences were highly significant. In each of these circumstances, the driving pressure across the lungs was significantly augmented in the hypertensive but not the normotensive group. Both epinephrine and norepinephrine have a vasoconstrictor influence on the lesser circulation as a consequence of vascular overreactivity. The opposite changes in resistance between normotensive and hypertensive subjects produced by epinephrine suggest that a constrictor vascular supersensitivity becomes active in the pulmonary circuit with the development of systemic high blood pressure.

Hypersensitivity of lung vessels to catecholamines in systemic hypertension

Among patients with primary systemic hypertension pressure and arteriolar resistance in the pulmonary circulation exceed normal values and are hyper-reactive to sympathetic stimulation. A study was therefore carried out in 16 patients with uncomplicated essential hypertension and nine healthy subjects to compare the pulmonary vascular reactivity to exogenous catecholamines. In the normotensive group the dose response relation to adrenaline (microgram: dyn) was 1 = -4, 2 = -9, 3 = -9, and 4 = -10 and to noradrenaline 2 = +3, 4 = /8, 6 = +4, and 8 = +3. The relations in the hypertensive subjects were 1 = +18, 2 = +42, 3 = +59, and 4 = +77 and 2 = +39, 4 = +54, 6 = +76, and 8 = +100, respectively. Group differences were highly significant. Cardiac output (blood flow through the lungs) was raised by adrenaline and reduced by noradrenaline. In either case the driving pressure across the lungs was significantly augmented in the hypertensive patients but not in the normotensive group. Both catecholamines had a vasoconstrictor effect on the pulmonary circulation as a result of vascular over-reactivity. The opposite changes in resistance between normal and hypertensive subjects produced by adrenaline suggest that a constrictor vascular hypersensitivity occurs in the pulmonary circulation with the development of systemic high blood pressure.