Hemodynamic characteristics of primary aldosteronism

The mTOR-inhibitor everolimus reduces hypervolemia in patients with primary aldosteronism

BACKGROUND

We recently showed in a proof-of-concept study that treating individuals with primary aldosteronism with the mTOR-inhibitor everolimus decreases home blood pressure and renin suppression overall, and markedly reduces aldosterone levels in a subset of individuals. Based on these findings, the question arose whether the effects of everolimus were also mediated via aldosterone-independent mechanisms. Here, we undertook an exploratory, secondary analysis of above-mentioned study to comprehensively investigate how everolimus impacted the hemodynamic status of the study participants, which in turn could elucidate these mechanisms.

METHODS

Hemodynamic parameters were measured in study participants with primary aldosteronism at baseline, after treatment with everolimus 0.75 mg orally twice daily for 2 weeks and after a 2-week wash-out. Of the 14 participants, 10 participants had complete data sets for peripheral and central blood pressure, heart rate and pulse wave velocity, and 7 participants had complete data sets for cardiac index, inotropic state index, left stroke work index and stroke systemic vascular resistance index that could be analyzed. Parameters were acquired by brachial oscillometry (Mobil-o-graph PWA) and thoracic electrical bioimpedance (HOTMAN® System).

RESULTS

After treatment with everolimus, peripheral (P=0.049) and central (P=0.037) diastolic blood pressure, as well as hypervolemia (P=0.008) were significantly decreased. Likewise, peripheral (P=0.073) and central systolic blood pressure (P=0.166) trended downwards.

CONCLUSIONS

Everolimus lowers central and peripheral blood pressure in individuals with primary aldosteronism, possibly by decreasing primary aldosteronism-induced hypervolemia and preload.

Tangram of Sodium and Fluid Balance

Homeostasis of fluid and electrolytes is a tightly controlled physiological process. Failure of this process is a hallmark of hypertension, chronic kidney disease, heart failure, and other acute and chronic diseases. While the kidney remains the major player in the control of whole-body fluid and electrolyte homeostasis, recent discoveries point toward more peripheral mechanisms leading to sodium storage in tissues, such as skin and muscle, and a link between this sodium and a range of diseases, including the conditions above. In this review, we describe multiple facets of sodium and fluid balance from traditional concepts to novel discoveries. We examine the differences between acute disruption of sodium balance and the longer term adaptation in chronic disease, highlighting areas that cannot be explained by a kidney-centric model alone. The theoretical and methodological challenges of more recently proposed models are discussed. We acknowledge the different roles of extracellular and intracellular spaces and propose an integrated model that maintains fluid and electrolyte homeostasis and can be distilled into a few elemental players: the microvasculature, the interstitium, and tissue cells. Understanding their interplay will guide a more precise treatment of conditions characterized by sodium excess, for which primary aldosteronism is presented as a prototype.

Coincidence of Large Adrenal Cyst and Prominent Hyporeninemic Hyperaldosteronism

A 67-year-old Japanese woman who had end-stage renal disease was referred to our hospital for kidney transplantation. Abdominal CT revealed a large adrenal mass with inhomogeneity. She had a history of hospitalization for stroke and heart failure and exhibited prominent hyporeninemic hyperaldosteronism. Histological examination of the resected tumor with anti-CYP11B2 antibody indicated that she had a vascular endothelial cyst with primary aldosteronism (PA) due to multiple adrenocortical micronodules. This report implicates the pathological interaction between adrenal vascular cysts and PA-mediated vascular damage of the adrenal vein.

Aldosterone-induced cardiac damage in primary aldosteronism depends on its subtypes

OBJECTIVES

This study compared cardiac function, morphology, and tissue characteristics between two common subtypes of primary aldosteronism (PA) using a 3T MR scanner.

DESIGN

A retrospective, single-center, observational study.

METHODS

We retrospectively reviewed 143 consecutive patients with PA, who underwent both adrenal venous sampling and cardiac magnetic resonance. We acquired cine, late gadolinium enhancement, and pre- and postcontrast myocardial T1-mapping images.

RESULTS

PA was diagnosed as unilateral aldosterone-producing adenoma (APA) in 70 patients and bilateral hyperaldosteronism (BHA) in 73. The APA group showed significantly higher plasma aldosterone concentration (PAC) and aldosterone to renin rate (ARR) than the BHA group. After controlling for age, sex, antihypertensive drugs, systolic and diastolic blood pressure, and disease duration, the parameters independently associated with APA were: left ventricular end-diastolic volume index (EDVI: adjusted odds ratio (aOR) = 1.06 (95% CI: 1.030-1.096), P < 0.01), end-systolic volume index (ESVI: 1.06 (1.017-1.113), P < 0.01), stroke index (SI: 1.07 (1.020-1.121), P < 0.01), cardiac index (CI: 1.001 (1.000-1.001), P < 0.01), and native T1 (1.01 (1.000-1.019), P = 0.038). Weak positive correlations were found between PAC and EDVI (R = 0.28, P < 0.01), ESVI (0.26, P < 0.01), and SI (0.18, P = 0.03); and between ARR and EDVI (0.25, P < 0.01), ESVI (0.24, P < 0.01), and native T1 (0.17, P = 0.047).

CONCLUSIONS

APA is associated with greater LV volumetric parameters and higher native T1 values, suggesting a higher risk of volume overload and myocardial damage.

Primary aldosteronism: Higher volume load, cardiac output and arterial stiffness than in essential hypertension

BACKGROUND

The diagnostics of primary aldosteronism (PA) are usually carried out in patients taking antihypertensive medications. We compared haemodynamics between medicated PA, medicated essential hypertension (EH), never-medicated EH and normotensive controls (n = 130 in all groups).

METHODS

The hypertensive groups were matched for age (53 years), sex (84 male/46 female) and body mass index (BMI) (30 kg m^-2 ); normotensive controls had similar sex distribution (age 48 years, BMI 27 kg m^-2 ). Haemodynamics were recorded using whole-body impedance cardiography and radial pulse wave analysis, and the results were adjusted as appropriate. Radial blood pressure recordings were calibrated by brachial blood pressure measurements from the contralateral arm.

RESULTS

Radial and aortic systolic and diastolic blood pressure was similar in PA and never-medicated EH, and higher than in medicated EH and normotensive controls (P ≤ 0.001 for all comparisons). Extracellular water balance was ~ 4% higher in PA than in all other groups (P < 0.05 for all), whilst cardiac output was ~ 8% higher in PA than in medicated EH (P = 0.012). Systemic vascular resistance and augmentation index were similarly increased in PA and both EH groups when compared with controls. Pulse wave velocity was higher in PA and never-medicated EH than in medicated EH and normotensive controls (P ≤ 0.033 for all comparisons).

CONCLUSIONS

Medicated PA patients presented with corresponding systemic vascular resistance and wave reflection, but higher extracellular water volume, cardiac output and arterial stiffness than medicated EH patients. Whether the systematic evaluation of these features would benefit the clinical diagnostics of PA remains to be studied in future.

Left ventricular remodeling and dysfunction in primary aldosteronism

Primary aldosteronism (PA) is a common cause of secondary hypertension and is associated with worse cardiovascular outcomes. The elevated aldosterone in PA leads to left ventricular (LV) remodeling and dysfunction. In recent decades, clinical studies have demonstrated worse LV remodeling including increased LV mass and cardiac fibrosis in patients with PA compared to patients with essential hypertension. Several mechanisms may explain the process of aldosterone-induced LV remodeling, including directly profibrotic and hypertrophic effects of aldosterone on myocardium, increased reactive oxygen species and profibrotic molecules, dysregulation of extracellular matrix metabolism, endothelium dysfunction and circulatory macrophages activation. LV remodeling causes LV diastolic and systolic dysfunction, which may consequently lead to clinical complications such as heart failure, atrial fibrillation, ischemic heart disease, and other vascular events. Adequate treatment with adrenalectomy or medical therapy can improve LV remodeling and dysfunction in PA patients. In this review, we discuss the mechanisms of aldosterone-induced LV remodeling and provide an up-to-date review of clinical research about LV remodeling-related heart structural changes, cardiac dysfunction, and their clinical impacts on patients with PA.

Resolution of drug-resistant hypertension by adrenal vein sampling-guided adrenalectomy: a proof-of-concept study

Drug-resistant hypertension (RH) is a very high-risk condition involving many hypertensive patients, in whom primary aldosteronism (PA) is commonly overlooked. Hence, we aimed at determining if (1) adrenal vein sampling (AVS) can identify PA in RH patients, who are challenging because of receiving multiple interfering drugs; (2) AVS-guided adrenalectomy can resolve high blood pressure (BP) resistance to treatment in these patients.

Based on a pilot study we selected from 1016 consecutive patients referred to our Centre for ‘difficult-to-treat’ hypertension those with RH, for an observational prospective cohort study. We excluded those non-adherent to treatment (by therapeutic drug monitoring) and those with pseudo-RH (by 24-h BP monitoring), which left 110 patients who met the European Society of Cardiology/European Society of Hypertension (ESC/ESH) 2013 definition for RH. Of these patients, 77 were submitted to AVS, who showed unilateral PA in 27 (mean age 55 years; male/female 19/8). Therefore, these patients underwent AVS-guided laparoscopic unilateral adrenalectomy, which resolved RH in all: 20% were clinically cured in that they no longer needed any antihypertensive treatment; 96% were biochemically cured. Systolic and diastolic BP fell from 165/100 ± 26/14 mmHg at baseline, to 132/84 ± 14/9 mmHg at 6 months after surgery (P&lt;10−4 for both) notwithstanding the fall of number and defined daily dose (DDD) of antihypertensive drugs required to achieve BP control (P&lt;10−4 for both). A prominent regression of cardiac and renal damage was also observed.

Thus, the present study shows the feasibility of identifying PA by AVS in RH patients, and of resolving high BP resistance to treatment in these patients by AVS-guided adrenalectomy.

Cardiac Remodeling in Patients With Primary and Secondary Aldosteronism

Background—

Primary aldosteronism (PA) causes excess left ventricular (LV) hypertrophy and diastolic dysfunction; whether this occurs also in secondary aldosteronism (SA) without hypertension is unknown. We investigated the cardiac modifications in patients with preserved LV ejection fraction who had PA or SA.

Methods and Results—

We measured several Doppler echocardiography–derived variables, including tissue Doppler imaging (TDI) parameters and strain rate analysis, in 262 patients with PA, 117 with SA because of liver cirrhosis, and in 61 control healthy subjects. SA and PA patients showed markedly elevated aldosterone levels (67 versus 39 ng/dL, respectively; normal values <15 ng/dL) but contrasting values of plasma renin activity (15.00 versus 0.56 ng/mL/h; P <0.001). Compared with PA, SA patients showed higher heart rate, and lower blood pressure and vascular resistance values. Both PA and SA showed increased LV diameters, LV volumes, stroke volume, stroke work, and septal peak systolic tissue velocity, and had more LV hypertrophy (61% and 39%, respectively) and diastolic dysfunction (35% and 36%, respectively) than healthy subjects. Peak systolic septal strain (20% versus 23%; P =<0.001) and midwall fractional shortening (15.9% versus 16.7%; P =0.001) were lower in PA than in SA patients.

Conclusions—

Primary and secondary hyperaldosteronism correlate with LV enlargement and high prevalence of LV hypertrophy and diastolic dysfunction; a subclinical systolic dysfunction is evident only in PA. In SA, the high rate of LV hypertrophy, in spite of low peripheral resistances and low-to-normal blood pressure, could be accounted for the high renin and aldosterone values, and the work overload associated with a hyperdynamic circulatory state.

Ambulatory Blood Pressure Monitoring-Derived Short-Term Blood Pressure Variability in Primary Aldosteronism

The aim of this study was to investigate the short-term blood pressure (BP) variability (BPV) derived from ambulatory blood pressure monitoring (ABPM) in patients with primary aldosteronism (PA), either idiopathic hyperaldosteronism (IHA) or aldosterone-producing adenoma (APA), in comparison with patients with essential hypertension (EH) and normotensive (NT) controls. Thirty patients with PA (16 with IHA and 14 with APA), 30 patients with EH, and 30 NT controls, matched for sex, age, body mass index, and antihypertensive therapy, were studied. The standard deviation (SD) of 24-hour, daytime, and nighttime BP; 24-hour weighted SD of BP; and 24-hour BP average real variability were not different between patients with PA and those with EH (P=not significant). All BPV indices were higher in patients with PA, either IHA or APA subtypes, and patients with EH, compared with NT controls (P<.001 to P<.05). ABPM-derived short-term BPV is increased in patients with PA, and it may represent an additional cardiovascular risk factor in this disease. The role of aldosterone excess in BPV has to be clarified.

Impact of aldosterone-producing adenoma on cardiac structures in echocardiography

Background

Primary aldosteronism (PA) is a most common cause of secondary hypertension. In PA, left ventricular hypertrophy (LVH) is more progressive than in any other cause of hypertension. Aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA) are major subtypes of PA. However there is little information concerned with differences of cardiac structures between these two subtypes.

Methods

We reviewed echocardiographic findings in 46 patients with PA. All patients had a positive screen test and subtypes of PA were confirmed by adrenal vein sampling. Subjects consisted of 20 patients with APA (APA group, 52.4 ± 10.8 years) and 26 patients with IHA (IHA group, 56.2 ± 9.5 years). We investigated differences of cardiac structures and functions in the left atrium and ventricle between the APA group and IHA group.

Results

In terms of clinical characteristics, the height and duration of hypertension were greater and serum potassium concentration and BMI were lower in the APA group than in the IHA group. Plasma aldosterone concentration (PAC) and PAC to plasma renin activity ratio were higher in the APA group than in the IHA group. In echocardiographic assessment, the left atrial volume, left ventricular end-diastolic and end-systolic diameters, left ventricular mass (LVM), and prevalence of LVH were greater in the APA group than in the IHA group. Multiple linear regression analysis revealed that the diagnosis of APA independently correlated with left atrial volume, left ventricular end-diastolic diameter, and LVM.

Conclusions

We demonstrated that differences of cardiac structures between the APA group and IHA group existed. In APA, left atrial enlargement and LVH were more prominent than in IHA.

How NaCl raises blood pressure: a new paradigm for the pathogenesis of salt-dependent hypertension

Excess dietary salt is a major cause of hypertension. Nevertheless, the specific mechanisms by which salt increases arterial constriction and peripheral vascular resistance, and thereby raises blood pressure (BP), are poorly understood. Here we summarize recent evidence that defines specific molecular links between Na(+) and the elevated vascular resistance that directly produces high BP. In this new paradigm, high dietary salt raises cerebrospinal fluid [Na(+)]. This leads, via the Na(+)-sensing circumventricular organs of the brain, to increased sympathetic nerve activity (SNA), a major trigger of vasoconstriction. Plasma levels of endogenous ouabain (EO), the Na(+) pump ligand, also become elevated. Remarkably, high cerebrospinal fluid [Na(+)]-evoked, locally secreted (hypothalamic) EO participates in a pathway that mediates the sustained increase in SNA. This hypothalamic signaling chain includes aldosterone, epithelial Na(+) channels, EO, ouabain-sensitive α(2) Na(+) pumps, and angiotensin II (ANG II). The EO increases (e.g.) hypothalamic ANG-II type-1 receptor and NADPH oxidase and decreases neuronal nitric oxide synthase protein expression. The aldosterone-epithelial Na(+) channel-EO-α(2) Na(+) pump-ANG-II pathway modulates the activity of brain cardiovascular control centers that regulate the BP set point and induce sustained changes in SNA. In the periphery, the EO secreted by the adrenal cortex directly enhances vasoconstriction via an EO-α(2) Na(+) pump-Na(+)/Ca(2+) exchanger-Ca(2+) signaling pathway. Circulating EO also activates an EO-α(2) Na(+) pump-Src kinase signaling cascade. This increases the expression of the Na(+)/Ca(2+) exchanger-transient receptor potential cation channel Ca(2+) signaling pathway in arterial smooth muscle but decreases the expression of endothelial vasodilator mechanisms. Additionally, EO is a growth factor and may directly participate in the arterial structural remodeling and lumen narrowing that is frequently observed in established hypertension. These several central and peripheral mechanisms are coordinated, in part by EO, to effect and maintain the salt-induced elevation of BP.

Differential regional haemodynamic changes during mineralocorticoid hypertension

BACKGROUND

Primary aldosteronism is a cause of hypertension in up to 10% of hypertensive patients, but the mechanisms by which excess aldosterone raises arterial pressure remain unclear.

OBJECTIVE

To investigate the systemic and regional haemodynamic changes during the development and maintenance of aldosterone-induced hypertension and the effect of sympathetic and vasopressin blockade.

METHODS

Responses to intravenous infusion of aldosterone (10 microg/h) for 4 weeks were determined in five conscious sheep. The effects of sympathetic blockade with propranolol and phentolamine or vasopressin V1-receptor blockade with SR59049 were investigated in six further sheep infused with aldosterone.

RESULTS

Aldosterone progressively increased the mean arterial pressure by 20 mmHg over 4 weeks (P < 0.001). The changes in cardiac output were variable between animals, resulting in no overall significant change. Total peripheral conductance was significantly decreased due to selective reductions in mesenteric conductance (from 6.17 +/- 0.27 to 4.46 +/- 0.15 ml/min per mmHg, P < 0.001) and iliac conductance (from 1.54 +/- 0.21 to 1.27 +/- 0.15 ml/min per mmHg, P < 0.001). In contrast, renal and coronary conductance were unchanged and renal blood flow increased from 290 +/- 17 to 350 +/- 28 ml/min (P < 0.01) and coronary blood flow from 34.7 +/- 3.0 to 44.6 +/- 2.5 ml/min (P < 0.05). These aldosterone-induced changes were not inhibited by sympathetic or vasopressin V1-receptor blockade.

CONCLUSION

Excess aldosterone caused a slow progressive increase in arterial pressure, which in the long term depended on reduced total peripheral conductance. This resulted from vasoconstriction in the gut and skeletal muscle, but not the kidney. These effects were not mediated by the sympathetic nervous system or vasopressin.

Myocardial ultrasonic backscatter in hypertension: relation to aldosterone and endothelin

A disproportionate accumulation of fibrillar collagen is a characteristic feature of hypertensive heart disease, but the extent of myocardial fibrosis may differ in different models of hypertension. In experimental studies, aldosterone and endothelins emerge as important determinants of myocardial fibrosis. Changes in myocardial extracellular matrix and collagen deposition can be estimated noninvasively by analysis of the ultrasonic backscatter signal, which arises from tissue heterogeneity within the myocardium and describes myocardial texture. This study was designed to investigate the relations between myocardial integrated backscatter and circulating aldosterone and immunoreactive endothelin in human hypertension. The study population consisted of 56 subjects: 14 healthy normotensive volunteers and 42 hypertensive patients (14 with primary aldosteronism, 7 with renovascular hypertension, and 21 with essential hypertension). The patients with essential and secondary hypertension were matched for age, gender, body mass index, and blood pressure. Myocardial integrated backscatter at diastole was 19.8+/-2.0 and 20.8+/-2.9 decibels in normotensive control subjects and patients with essential hypertension and significantly higher in patients with primary aldosteronism (27.4+/-3.8 decibels, P<0.01) and renovascular hypertension (26.8+/-4.8 decibels, P<0.01). In the population as a whole, as well as in the hypertensive subpopulation, myocardial integrated backscatter was directly related to plasma aldosterone (r=0.73 and 0.71, P<0.01 for both) and immunoreactive endothelin (r=0.60 and 0.56, P<0.01 for both). The data of this study suggest that in human hypertension, circulating aldosterone and immunoreactive endothelin may induce alterations in left ventricular myocardial texture, possibly related to increased myocardial collagen content.

Hyperaldosteronism: the internist's hypertensive disease

Primary aldosteronism (PA) is a disorder typically characterized by resistant hypertension, hypokalemia, alkalosis and suppressed plasma renin activity, and excessive aldosterone production. A true estimate of the prevalence of the disorder is difficult to estimate because its detection is dependent on the awareness of the healthcare provider to the disorder, but it has generally been felt to be a rare occurrence. Its frequency of detection began to change when Hiramatsu suggested calculating the ratio of plasma aldosterone/plasma renin activity as a screening tool for the disorder. He found a ratio greater than 75 as a sensitive indicator for aldosterone-producing adenomas. Using the ratio, several investigators have found prevalence ranging from 3 to 9%. Two major classifications of PA exist: aldosterone-producing adrenal adenoma (APA) and zona glomerulosa hyperplasia (IHA). Distinguishing between these 2 entities is important clinically, because removal of a unilateral aldosterone-producing adenoma may result in correction of elevated blood pressure and hypokalemia. Thus, when evaluating hypertensive patients, PA should be suspected in those with moderate to severe hypertension or with hypertension refractory to standard treatment or in hypertensive patients with disease onset at an early age. The aldosterone-to-renin ratio is an easy, inexpensive, and rapid means of screening for the disorder. The ratio is the screening test of choice, but further confirmatory testing is required to clinch the diagnosis. Frequently employed confirmatory tests include urinary aldosterone excretion on a high-salt diet, aldosterone suppression after a saline infusion, and the fludrocortisone suppression test, which is considered the most sensitive confirmatory maneuver. Both high-resolution CT and MRI scans appear to have similar ability to differentiate between APA and IHA. As with essential hypertension, the goal of treatment is to prevent the long-term sequela of hypertension. The underlying pathology resulting in PA dictates the treatment strategy. The drug of choice is spironolactone. Surgical intervention should be entertained in those patients with PA in whom imaging studies suggest an adenoma.

Medical management of primary hyperaldosteronism

Most forms of primary aldosteronism are surgically correctable. However, when surgery is not appropriate, medical management is just as effective in correcting the pathophysiologic abnormalities due to aldosterone excess. A prerequisite for the rational medical management of primary aldosteronism is an understanding of the mechanisms that sustain hypertension. Primary aldosteronism can be associated with severe and resistant hypertension, and persistent hypervolemia is the primary reason for resistance to therapy. Patients with overriding comorbidities or strong preferences have been medically treated over the intermediate term of 5 to 7 years without evidence of escape or evidence of malignant transformation of adrenal adenomas.

Heart rate as a predictor of future blood pressure in schoolchildren

Heart rate (HR) has been shown to predict future blood pressures (BP) in studies in adults. We explored the relation of HR to future BP levels in a cohort of 344 black and 456 white schoolchildren ages 5 to 19 years, to examine the hypothesis that HR predicts subsequent BP even very early in life. After making baseline measurements, BP was assessed longitudinally 1 to 24 additional times (mean = 8.25) after the baseline period, at intervals of approximately 6 months. We found that HR was significantly related to future diastolic BP in the black boys (P = .016) after adjusting for baseline diastolic BP, age, and body mass index, but not in the black girls or in the white children. Because HR is reflective of sympathetic nervous system (SNS) activity that in turn can be related to the renin-angiotensin system (RAS), we also explored the relation of HR to the RAS by studying relationships to variants in the angiotensinogen gene and the angiotensin I-converting enzyme (ACE) gene. We found a significantly positive relationship of HR to the presence of the deletion allele of the ACE gene (P = .0015), but, again, only in the black boys. Because blacks in general appear to retain additional sodium when compared with whites, the SNS, as reflected in the HR, may influence BP more when individuals have increased sodium retention. In summary, baseline HR predicted future diastolic BP in the black boys but not in the black girls or in the white children.

Altered adrenal sensitivity to angiotensin II in low-renin essential hypertension

Low-renin essential hypertension (LREH) describes a widely recognized classification validated by clinical features, including salt-sensitive blood pressure and diuretic responsiveness. Classic physiological teaching has cited normal plasma aldosterone concentration despite suppressed renin as evidence for adrenal supersensitivity to angiotensin II (Ang II). We studied 94 patients with LREH, 242 normal-renin hypertensives, and 135 normal subjects as controls. Low-renin hypertensives did not differ significantly from the other groups in either basal or Ang II-stimulated aldosterone concentrations on a high-sodium diet. Stimulated with a low-sodium diet, LREH patients demonstrated the smallest rise in basal aldosterone secretion. Ang II responsiveness was also subnormal: the rise in aldosterone after Ang II infusion in LREH (613+/-39 pmol/L), although greater than in nonmodulators (180+/-17 pmol/L; P=0.001), was less than either the patients with intact modulation (940+/-53 pmol/L; P=0.001) or normotensives (804+/-50 pmol/L; P<0.05). Blacks with LREH demonstrated an even lower response than low-renin whites ((388+/-50 versus 610+/-47 pmol/L; P=0.0001). In contrast, the rise in systolic blood pressure with Ang II infusion on a low-salt diet was greatest among LREH patients (P=0. 001). Patients with LREH and nonmodulators were equally salt-sensitive. These results indicate that the adrenal response in LREH is normal on a high-salt diet but becomes progressively more abnormal as sodium control mechanisms are stressed. The factors that mediate enhanced adrenal response to Ang II with sodium restriction may be defective, suggesting the existence of alternative physiological mechanisms for sodium homeostasis in the low-renin state.

Mineralocorticoid hypertension

Hypertension with hypokalaemia and suppression of plasma renin activity is known as mineralocorticoid hypertension. Although mineralocorticoid hypertension accounts for a small number of patients labelled as having "essential" hypertension, it is a potentially reversible cause of high blood pressure. The most common cause of mineralocorticoid hypertension is probably primary aldosteronism; controlled posture studies to measure plasma renin activity and aldosterone concentrations, followed by adrenal imaging, will ensure the differential diagnosis between an aldosterone-producing adenoma and idiopathic adrenal hyperplasia in most cases. Three monogenic forms of mineralocorticoid hypertension have been described: glucocorticoid-suppressible hyperaldosteronism, Liddle's syndrome, and apparent mineralocorticoid excess, which have provided new insights into mineralocorticoid hormone action. Many patients with mineralocorticoid-based hypertension are now known to have normal serum potassium concentrations. Until the true prevalence of primary aldosteronism and monogenic forms of mineralocorticoid hypertension are defined, a high index of suspicion is needed in every hypertensive patient. Hypertensive patients with hypokalaemia, together with those with severe hypertension or a family history of hypertension or stroke, should be screened for mineralocorticoid excess.

Left ventricular systolic function in primary aldosteronism and hypertension

OBJECTIVE

This study was designed to investigate whether the excess aldosterone found in primary aldosteronism (PA) influences left-ventricular systolic function (LVSF), through a positive inotropic effect

METHODS

M-mode and two-dimensional echocardiography and transmitral Doppler flow velocity measurements were performed in 82 patients: 44 with confirmed PA (23 male; 21 female; aged 51.8+/-13 years) and 38 essential hypertension patients (16 male; 22 female; aged 48.5+/-12 years) matched for demography and blood pressure (BP) values. We measured left-ventricular (LV) midwall fractional shortening (MwFSho) and LV circumferential end-systolic stress (cESS, calculated according to Reichek's equation) and analysed the relationship between MwFSho and cESS.

RESULTS

These are given as the mean +/- standard deviation. PA patients had significantly higher cardiac index (CI) (3.55+/-0.94 l/m2 vs 2.98+/-0.58, P < 0.005) and lower E wave/A wave time-velocity integral ratio (0.93+/-0.27 vs 1.26+/-0.41, P < 0.001) than EH, whereas mean BP (126+/-12 mmHg vs 128+/-12), MwFSho (17.1+/-2.4% vs 16.3+/-1.9), cESS (118+/-19 Kdynes/cm2 vs 121+/-18) and the relationship between LV MwFSho and LV cESS did not differ between groups.

CONCLUSION

These findings confirm that PA patients exhibit: (1) a modest increase of CI; (2) an LV diastolic filling mainly occurring with the atrial kick. However, they do not lend support to the contention that the excess of plasma aldosterone seen in PA is associated with enhanced LV inotropism under resting conditions.

Left ventricular anatomy and function in primary aldosteronism and renovascular hypertension

Left ventricular hypertrophy (LVH) is a common finding in hypertension and represents a detrimental outcome since it is associated with increased morbidity and mortality. For similar elevation of blood pressure the severity and type of LVH vary considerably in relation to several factors. Compelling evidence suggests that both the renin-angiotensin system (RAS) and the aldosterone excess play an important role in the pathogenesis of LVH, since experimentally angiotensin II has been found to cause myocardial cells hypertrophy and/or hyperplasia and excess aldosterone has been related to extracellular matrix and collagen deposition and therefore to myocardial fibrosis. Secondary forms of hypertension offer models for investigating the relative role of the RAS and aldosterone on the heart in humans. Being rare in the population of hypertensive patients, they furnish an example of the so called Bateson's approach to the understanding of diseases "Treasure your exceptions." In this paper, we review the data concerning the LV changes in primary aldosteronism and renovascular hypertension and discuss the insight that they have provided into the pathogenesis of LVH.

Left ventricular hypertrophy precedes other target-organ damage in primary aldosteronism

To elucidate whether there is a difference in the progression of target-organ damage between primary aldosteronism and essential hypertension, we compared left ventricular hypertrophy and extracardiac target-organ damage in 23 patients with primary aldosteronism and 116 patients with essential hypertension. The severity of hypertensive retinopathy and the renal involvement in primary aldosteronism were subclinical and similar to those in essential hypertension without left ventricular hypertrophy but significantly milder than those in essential hypertension with left ventricular hypertrophy. There was a strongly significant correlation between the degree of left ventricular mass index and the severity of hypertensive retinopathy and renal involvement independent of office blood pressure in essential hypertension. In contrast, left ventricular hypertrophy markedly progressed despite the mild extracardiac target-organ damage in primary aldosteronism. Left ventricular end-diastolic dimension index in primary aldosteronism (3.16+/-0.50 cm/m2) was significantly larger than in essential hypertension without (2.87+/-0.23) and with (2.88+/-0.22) left ventricular hypertrophy. On the other hand, there was no difference in extracardiac target-organ damage between 13 primary aldosteronism patients with eccentric left ventricular hypertrophy and the 26 essential hypertensive patients with eccentric left ventricular hypertrophy. The results suggest that predominantly volume load, be it due to aldosteronism or other mechanisms, resulting in eccentric left ventricular hypertrophy is less likely to cause extracardiac target-organ damage than hemodynamic or nonhemodynamic mechanisms resulting in concentric left ventricular hypertrophy.

Primary Hyperaldosteronism

OBJECTIVE

To characterize the syndrome of primary aldosteronism and summarize diagnostic and therapeutic strategies.

METHODS

We review the mechanisms of action of aldosterone and outline features that distinguish the major subtypes of aldosteronism.

RESULTS

The state of aldosterone excess should be suspected in every patient manifesting hypertension and hypokalemia. The documentation of low renin activity and high plasma aldosterone concentration in such patients suggests the presence of primary aldosteronism. Lack of appropriate suppression of plasma aldosterone after saline infusion is thought to be the best maneuver for confirming primary aldosteronism. Nonetheless, a similar lack of aldosterone suppressibility after either oral salt loading for 3 days or oral administration of a single 25-mg dose of captopril may help achieve the same purpose. Once primary aldosteronism has been diagnosed, the distinction between two major subtypes--unilateral adrenal adenoma or Conn's syndrome and bilateral idiopathic adrenal hyperplasia--is important because of the difference in management. Certain physiologic maneuvers, such as change of posture from supine to upright, oral administration of cyproheptadine, and radiologic localization with several techniques including iodocholesterol scanning and adrenal venous sampling, will almost always help distinguish unilateral adenoma from bilateral hyperplasia.

CONCLUSION

The distinction between adrenal adenoma and adrenal hyperplasia is critical because of the varied approach to treatment. Most patients with bilateral adrenal hyperplasia are managed medically with an aldosterone antagonist such as spironolactone, whereas most unilateral adenomas are resected after correction of hypertension and hypokalemia with appropriate medical therapy.

Secondary hypertension: evaluation and treatment

Most patients with hypertension in the United States have essential (primary) hypertension (95%), the cause of which is unknown. The remaining 5% of adults with hypertension have the secondary form of hypertension, the cause and pathophysiologic process of which are known. Internists and other primary care physicians refer to this as treatable or curable hypertension, because the hypertension can be managed or even controlled with medications. Similarly, the condition is called surgical hypertension by surgeons in the belief that once the cause is determined and identified, surgical intervention will result in cure of hypertension. Secondary causes of hypertension include renal parenchymal disease, renovascular diseases, coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism. Occasionally included in this category are alcohol- and oral contraceptive-induced hypertension and hypothyroidism, but these conditions are not discussed herein. The evaluation of secondary hypertension is of interest and can bring together different facets of anatomy, physiology, pharmacology, and radiology in the medical and surgical treatment of these disorders. Despite enthusiasm that can be generated in the evaluation of these conditions, evaluation can be expensive and should not be conducted for all patients with hypertension. Features that aid in the diagnosis of secondary hypertension include the following: 1. Onset of hypertension before the age of 20 or after the age of 50 years. The presence of hypertension at a young age may suggest coarctation of the aorta, fibromuscular dysplasia, or an endocrine disorder. Hypertension found for the first time after the age of 50 years may suggest the presence of renovascular hypertension caused by atherosclerosis. 2. Markedly elevated blood pressure or hypertension with severe end-organ damage, as in grade III or IV retinopathy. These findings suggest the presence of renovascular hypertension or pheochromocytoma. 3. Specific body habitus and ancillary physical findings. For example, truncal obesity and purple striae occur with hypercortisolism, and exophthalmos is associated with hyperthyroidism. 4. Resistant or refractory hypertension (poor response to medical therapy usually necessitating use of more than three antihypertensive medications from three different classes). 5. Specific biochemical test that suggest the existence of certain disorders, such as hypercalcemia in hyperparathyroidism, hyperglycemia in Cushing's syndrome and pheochromocytoma, and unprovoked hypokalemia with renin-producing tumors, primary hyperaldosteronism, or renin-mediated renovascular hypertension. 6. Other characteristics that may suggest secondary hypertension such as abdominal diastolic bruits (renovascular hypertension), decreased femoral pulses (coarctation of the aorta), or bitemporal hemianopias (Cushing's disease). A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation.

Changes in left ventricular anatomy and function in hypertension and primary aldosteronism

We investigated the effects on the heart of hypertension due to the excess of aldosterone and suppression of the renin-angiotensin system caused by primary aldosteronism with M-mode echocardiography and transmitral Doppler flow velocity measurements. We studied 34 consecutive patients with primary aldosteronism and 34 with essential hypertension individually matched for age, gender, race, body mass index, blood pressure values, and duration of hypertension. The groups were similar in age, body mass index, blood pressure, and duration of hypertension. However, lower serum potassium levels (3.5 +/- 0.6 versus 4.1 +/- 0.2 mmol/L, P < .0001) and plasma renin activity (0.53 +/- 0.45 versus 1.82 +/- 1.59 ng Ang I x mL-1 x h-1, P < .0001) and higher plasma aldosterone levels (1107 +/- 774 versus 206 +/- 99 pmol/L, P < .0001), left ventricular wall thickness, and left ventricular mass index (112 +/- 4.7 versus 98 +/- 3.7 g/m2, P = .029) were found in patients with primary aldosteronism compared with those with essential hypertension. Similarly, the PQ interval was longer (173 +/- 20 versus 141 +/- 14 milliseconds, P < .001) in primary aldosteronism than in essential hypertension patients. Significantly more primary aldosteronism than essential hypertension patients had left ventricular hypertrophy or left ventricular concentric remodeling (50% versus 15%, chi 2 = 11.97, P = .007). Both the E wave flow velocity integral (1063 +/- 65 versus 1323 +/- 78, P = .013) and the E/A integral ratio (0.91 +/- 0.05 versus 1.25 +/- 0.08, P < .001) were lower, and atrial contribution to left ventricular filling was higher (53.3 +/- 1.5% versus 45.5 +/- 1.3% P < .001) in patients with primary aldosteronism compared with essential hypertension patients. After 1 year of follow-up, highly significant decreases of left ventricular wall thickness and mass were observed in patients treated with surgical excision of an aldosterone-producing tumor, but not in those with medical therapy. Thus, in patients with primary aldosteronism, the excess aldosterone with suppression of the renin-angiotensin system is associated with both increased left ventricular mass and significant changes of left ventricular diastolic filling. The former changes appear to be reversible on removal of the cause of excessive aldosterone production.

Normal sympathetic vasomotor and cardiac parasympathetic activities in patients with primary aldosteronism: assessment by spectral analysis

The role of the autonomic nervous system in hypertension due to mineralocorticoid excess remains unclear. To address this issue, we performed power spectral analysis of blood pressure (BP) and RR interval oscillations in 20 patients with primary aldosteronism (PA), 54 patients with essential hypertension (EH) and 45 normotensive (NT) subjects. Blood pressure and the degree of organ damage were similar between PA and EH groups. Age did not differ between the three groups. The Mayer wave power spectrum (MWP) of BP (approx. 0.1 Hz), an index of sympathetic vasomotor tone, was smaller in patients with PA than in patients with EH either while subjects were supine (systolic/diastolic; 3.9 +/- 3.2 (SD)/1.5 +/- 1.3 vs. 5.5 +/- 4.2/2.1 +/- 1.6 mmHg2, P < 0.05 for both) or standing (7.6 +/- 6.6/3.0 +/- 3.0 vs. 17.7 +/- 23.7/7.2 +/- 8.3 mmHg2, P < 0.05 for both). Supine respiratory-related power spectrum (RRP) of the RR interval (approx. 0.25 Hz), an index of cardiac parasympathetic tone, was greater in patients with PA than in patients with EH (545 +/- 574 vs. 302 +/- 464 ms2, P < 0.01). The MWP of BP and the RRP of the RR interval were similar between patients with PA and NT subjects. Adrenalectomy reduced the 24-h mean BP (-18 mmHg for systolic BP, P < 0.001; -12 mmHg for diastolic BP, P < 0.01) and increased the 24-h mean heart rate (+8 bpm, P < 0.001). Furthermore, the diastolic MWP increased mildly (+32%, P < 0.05) and the RRP of the RR interval decreased dramatically (-75%, P < 0.01) following adrenalectomy. These results suggest that both vascular sympathetic and cardiac parasympathetic regulatory systems have minor roles in the maintenance of hypertension in patients with PA. The autonomic nervous system contributes more to the maintenance of BP following than prior to adrenalectomy. This information may be useful for the management of hypertension still persists after removal of adrenal adenoma.

Hypertensive crisis during the resection of an adrenal tumor in primary aldosteronism

Primary aldosteronism is one of the few causes of hypertension which is subject to total surgical treatment, but a hypertensive crisis can occur during the resection of the adrenal tumor. We undertook this study to evaluate the relationship between hormonal factors and a hypertensive crisis during surgery. Sixteen patients with primary aldosteronism who were scheduled for the resection of an adrenal tumor were participated in this investigation. Hormonal factors and hemodynamic variables were evaluated before induction of anesthesia, after induction of anesthesia, 30 minutes after the incision, during tumor manipulation, during resection, and immediately after surgery. During tumor manipulation, a hypertensive crisis occurred in six patients (hypertensive group; HG) but not in any others (non-hypertensive group; NHG). There were no differences in hormonal levels, except epinephrine, during tumor manipulation between HG and NHG. Hemodynamic evaluations revealed an increase of systemic vascular resistance during the hypertensive crisis. We conclude that the hypertensive crisis during the manipulation of an adrenal tumor is caused by the rapid release of epinephrine from the manipulated adrenal gland.

Left ventricular structural characteristics in unilateral renovascular hypertension and primary aldosteronism

To assess the importance of the renin-angiotensin system and plasma volume as determinants of hypertensive left ventricular hypertrophy and its anatomy, patients with unilateral renovascular hypertension and primary aldosteronism were studied by echocardiography. Blood pressure, age and sex were matched as closely as possible. The 19 patients with unilateral renovascular hypertension and the 19 patients with primary aldosteronism were similar in age, sex and blood pressure (168 +/- 19/97 +/- 11 and 163 +/- 17/99 +/- 10 mm Hg, respectively), but plasma volume was increased in the patients with primary aldosteronism. Interventricular septal thickness, left ventricular posterior wall thickness, left ventricular mass index and relative wall thickness did not differ between the 2 groups of patients. There was a significant correlation between the level of systolic blood pressure and either left ventricular mass index (r = 0.34, p less than 0.05) or relative wall thickness (r = 0.58, p less than 0.001) in both groups of patients. Left ventricular end-diastolic dimension index was increased in the patients with primary aldosteronism compared with those with unilateral renovascular hypertension (3.2 +/- 0.4 vs 2.9 +/- 0.3 cm/m2, p less than 0.02). When confined to the patients with systolic pressure greater than or equal to 150 mm Hg, relative wall thickness was significantly increased in the patients with unilateral renovascular hypertension. Patients with primary aldosteronism and unilateral renovascular hypertension of similar blood pressure levels, age and sex have almost identical degrees of left ventricular hypertrophy and anatomy. In contrast, the patients with primary oldosteronism had increased left ventricular dimension index.(ABSTRACT TRUNCATED AT 250 WORDS)

Syndrome of apparent mineralocorticoid excess. A defect in the cortisol-cortisone shuttle

The first adult case of 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) deficiency is described. The impaired conversion of cortisol to cortisone (indicated by urinary cortisol and cortisone metabolites and failure to metabolize 11 alpha-[3H]cortisol to [3H]H2O), was associated with hypertension, hypokalemia, and suppression of the renin-angiotensin-aldosterone system. When established on a fixed Na+/K+ intake, dexamethasone, given orally, produced a natriuresis and potassium retention. Plasma renin activity became detectable. When hydrocortisone (10 mg daily s.c. for 4 d) was added, there was marked Na+ retention, a kaliuresis (urinary Na+/K+ falling from 1.2 to 0.15), with suppression of plasma renin activity and an increase in blood pressure. These changes were also seen with the subject on no treatment. Conversion of cortisone to cortisol was not affected. These results suggest that cortisol acts as a potent mineralocorticoid in 11 beta-OHSD deficiency. The major site for the oxidation of cortisol to cortisone is the kidney. In this patient congenital deficiency of 11 beta-OHSD results in high intrarenal cortisol levels which then act on renal type I mineralocorticoid receptors. This condition can be treated with dexamethasone, which suppresses cortisol secretion and binds to the type II glucocorticoid receptor. We suggest that 11 beta-OHSD exerts a critical paracrine role in determining the specificity of the type I receptor. In the normal state cortisol is converted by 11 beta-OHSD to cortisone which thus allows aldosterone to bind preferentially to the type I receptors in the kidney and gut. In this patient deficiency of 11 beta-OHSD results in high intrarenal cortisol concentrations that then bind to the type I receptor.

Clinical implications of primary aldosteronism with resistant hypertension

Twenty-eight patients with resistant hypertension were found to have primary aldosteronism; 25 had solitary adenoma and 3 had adrenal hyperplasia. All were severely hypertensive despite receiving three or more antihypertensive agents, including conventional doses of diuretics, sympatholytics, and vasodilators. Hypervolemia (24 patients) or normovolemia (2 patients) despite severe diastolic hypertension was the hallmark in 26 patients. Adequate salt and water depletion alone with spironolactone (200 mg/day) and hydrochlorothiazide (50-100 ng/day) reduced arterial pressure in all. Twenty-two patients had surgical removal of a solitary adenoma. Over 1 to 2 years of follow-up, 13 were normotensive without medication, and six required hydrochlorothiazide and three hydrochlorothiazide plus a beta-blocker to normalize blood pressure. Blood pressure response to surgery had no relation to either duration or severity of hypertension. Six patients (three with hyperplasia, three with adenoma) have continued diuretic therapy and are normokalemic and normotensive. These results indicate that primary aldosteronism can be associated with sever and drug-resistant hypertension, that maintained hypervolemia is the reason for resistance to therapy, that sustained volume depletion is the most important therapeutic goal for these patients, and that cure can be achieved despite prolonged and severe hypertension.

Hemodynamic considerations in clinical hypertension

Hypertension by definition is a hemodynamic disorder. The hemodynamic characteristics of the different stages of essential hypertension are discussed, with particular emphasis on the involvement of the heart and kidneys.

Pressor factors and responsiveness in hypertension accompanying diabetes mellitus

Hypertension accompanying diabetes mellitus may involve abnormalities in at least two major blood pressure-regulating systems: the body sodium-fluid volume state and cardiovascular reactivity. In metabolically stable nonazotemic diabetes, exchangeable sodium is increased by 10% on average, regardless of age, insulin dependence or nondependence, or the presence or absence of diabetic retinopathy or clinical nephropathy (proteinuria greater than or equal to 0.3 g/24 hr). Possible contributing mechanisms include renal sodium retention and an extravascular shift of fluid and sodium; intracellular accumulation is not excluded. Circulatory volume is normal or low and the total exchangeable sodium/blood volume ratio increased. In hypertensive diabetes, the latter abnormality is particularly pronounced; systolic pressure tended to correlate with exchangeable sodium (r = 0.47, p less than 0.001) and diastolic pressure with the plasma sodium/potassium ratio (r = 0.25, p less than 0.05). Plasma aldosterone, renin, epinephrine, and norepinephrine levels are generally normal or sometimes low in metabolically stable nonazotemic diabetic patients with normal or high blood pressure; the plasma clearance of norepinephrine also appears to be unaltered. The cardiovascular pressor responsiveness to norepinephrine is often exaggerated relative to concomitant plasma concentrations, regardless of age, type of antidiabetic treatment, or presence or absence of diabetic retinopathy, peripheral neuropathy, or high blood pressure. Pressor responsiveness to angiotensin II also may sometimes be increased relative to plasma renin levels. Sodium retention and diabetic vasculopathy of resistance vessels could be important complementary mechanisms of hyperreactivity. In diabetes with mild hypertension, diuretic treatment restored exchangeable sodium, norepinephrine pressor responsiveness, and blood pressure toward normal. Thus sodium retention and cardiovascular hyperreactivity tend to occur even at the normotensive, nonazotemic stage of diabetes and may concomitantly predispose for the frequent development of hypertension in the diabetic population.

Hormone and blood pressure relationships in primary aldosteronism

We used continuous intra-arterial pressure monitoring and hourly venous hormone sampling over 24 hours in 5 patients with primary aldosteronism to study blood pressure and hormone regulation. Three patients were restudied under identical conditions of controlled diet electrolyte intake and body posture 3-7 months after removal of the aldosterone-secreting adrenal tumor. Prior to surgery there was no positive relationship of arterial pressure to renin or to aldosterone. Norepinephrine fluctuations showed positive correlations with arterial pressure but these 2 indices were more closely related after surgery. Plasma aldosterone levels paralleled those of cortisol both before and after cure of primary aldosteronism. Aldosterone/cortisol regression lines were steeper before surgery, and norepinephrine/renin regression lines were steepened in the post-operation studies. Our findings indicate that in established primary aldosteronism, fluctuations in arterial pressure are regulated in part by the sympathetic nervous system: the pattern of aldosterone secretion is controlled mainly by ACTH: aldosterone responsiveness to endogenous ACTH is enhanced: and sympathetic modulation of renin release in inhibited.

Recurrence of hypertension in primary aldosteronism after discontinuation of spironolactone. Time course of changes in cardiac output and body fluid volumes

Hemodynamic mechanisms underlying the hypertensive action of long-standing sodium overload were studied in ten subjects with aldosterone-producing adenoma. Arterial pressure was 129+/-4/91+/-4 mm Hg (mean+/-SEM) during spironolactone treatment, 177+/-5/114+/-3 mm Hg six weeks after the drug had been stopped, and 136+/-4/94+/-3 mm Hg two months after operation. In the six weeks following cessation of spironolactone, cardiac output, stroke volume, blood volume and sodium space were determined at weekly intervals. In each subject the biochemical syndrome of aldosterone-excess had been fully developed in two weeks. The hemodynamic changes in that period were also uniform. Mean arterial pressure in week 2 was increased by 20+/-3% with parallel increments of cardiac output and stroke volume of 22+/-5 and 30+/-6%. Blood volume and sodium space were increased by 11+/-2 and 29+/-4%. The patterns in weeks 2-6 were not uniform. In five subjects (age 33-49 yr) the hypertension was maintained through increased cardiac output; in week 6 it was 34+/-7% above its initial value, and stroke volume and blood volume were 37+/-4 and 16+/-4% above control. In the remaining five subjects (age 50-60 yr) cardiac output, stroke volume and blood volume returned to their initial values, and total peripheral resistance in week 6 was 36+/-13% above control. Sodium space remained expanded in both groups. The measurements after surgery confirmed the existence of the high-flow and high-resistance patterns; there was a decrease in cardiac output in the former group of subjects and a decrease in resistance in the latter. Apparently, increased resistance is not a direct consequence of increased flow. The observed age-related differences in hemodynamic patterns of sodium overload bear some resemblance to essential hypertension where a high-flow state of long duration may precede the ultimate phase of low vascular capacitance and high resistance.

Withdrawal of endogenous sympathetic drive lowers blood pressure in primary aldosteronism

We were able to observe the effect of withdrawal of endogenous sympathetic drive in a hypertensive patient with an aldosterone-secreting adrenal adenoma. Acute stimulation of both carotid sinus nerves lowered blood pressure to normotensive or hypotensive levels by reducing peripheral resistance. When chronic carotid sinus nerve stimulation was discontinued, peripheral resistance and blood pressure increased. These data suggest that the sympathetic nervous system is important in the maintenance of hypertension in established primary aldosteronism.

[Haemodynamic studies on the blood pressure-raising effect of mineralocorticoids (author's transl)]

The effects on systemic haemodynamics of long-term administration of high mineralocorticoid doses were studied in six healthy volunteers. The subjects received the synthetic steroid fludrocortisone in a daily oral dose of 0.8 mg. Central venous and arterial pressures were recorded directly, and cardiac output was determined by dye dilution method before as well as after 1 and 6 weeks of steroid application. Within the first week of steroid administration, mean arterial pressure rose by 5.6 +/- 4.6 (+/- S.D.) mm Hg (p less than 0.025). Body weight increased by 2.5 +/- 1.1 kg (p less than 0.01), and central venous pressure by 1.3 +/- 1.4 mm Hg (p less than 0.05). An increase in cardiac index was observed in all subjects, the average increase was 0.72 +/- 0.47 1/min.m2 (p less than 0.01). Heart rate decreased. After the 6th week of steroid administration, blood pressure had risen in all subjects, the average increase in mean arterial pressure was 17.8 +/- 6.0 mm Hg (p less than 0.001). This pressure rise was the consequence of an increase in total peripheral resistance by 267 +/- 125 dyn.cm-5.s (p less than 0.01) on the average. At that time cardiac index was even lower than at the first study in five of the six subjects. Compared to the second study, heart rate had decreased further, central venous pressure had increased further, and body weight had not changed significantly. This data show that the mineralocorticoid-induced blood pressure rise is initially due to an increase in cardiac output and in its chronic phase due to an elevated peripheral resistance. The mechanism of the increase in peripheral resistance remains unclear.