Chrysanthos Zamboulis

Prevalence of primary hyperaldosteronism in resistant hypertension: a retrospective observational study.

BACKGROUND Results of several studies published since 1999 suggest that primary hyperaldosteronism (also known as Conns syndrome) affects more than 10% of people with hypertension; however, such a high prevalence has also been disputed. Experts generally agree that resistant hypertension has the highest prevalence of primary hyperaldosteronism, on the basis of small studies. We aimed to assess the prevalence of primary hyperaldosteronism in a large group of patients with resistant hypertension. METHODS Patients with resistant hypertension (blood pressure >140/90 mm Hg despite a three drug regimen, including a diuretic) who attended our outpatient clinic were assessed for primary hyperaldosteronism. Serum aldosterone and plasma renin activity were determined and their ratio was calculated. Patients with a positive test (ratio >65.16 and aldosterone concentrations >416 pmol/L) underwent salt suppression tests with intravenous saline and fludrocortisone. Diagnosis of primary hyperaldosteronism was further confirmed by the response to treatment with spironolactone. FINDINGS Over 20 years, we studied 1616 patients with resistant hypertension. 338 patients (20.9%) had a ratio of more than 65.16 and aldosterone concentrations of more than 416 pmol/L. On the basis of salt suppression tests, 182 (11.3%) patients had primary hyperaldosteronism, and response to spironolactone treatment further confirmed this diagnosis. Hypokalaemia was seen only in 83 patients with primary hyperaldosteronism (45.6%). INTERPRETATION Although the prevalence of primary hyperaldosteronism in patients with resistant hypertension was high, it was substantially lower than previously reported. On the basis of this finding, we could assume that the prevalence of primary hyperaldosteronism in the general unselected hypertensive population is much lower than currently reported. Thus, the notion of an epidemic of primary hyperaldosteronism is not supported.

Angiotensin Converting Enzyme Gene Polymorphism is Not Related to Essential Hypertension in a Greek Population

Studies in various ethnic groups have shown contradictory evidence on the association of the angiotensin converting enzyme (ACE) insertion/ deletion (I/D) polymorphism with essential hypertension. In addition, mistyping of the insertion allele in heterozygotes has been reported. We analyzed the ACE genotype of 98 hypertensive and 84 normotensive subjects of Greek origin. Genomic DNA was extracted from blood samples and amplified by polymerase chain reaction (PCR). PCR primers were flanking the polymorphic region in intron 16 of the ACE gene. To avoid mistyping of heterozygotes, samples with the DD genotype were also amplified with primers that detect only the insertion allele. The distribution of the DD, ID, and II ACE genotypes was 30, 45, and 23 in hypertensive patients and 29, 40, and 15 in normotensive subjects, respectively. The estimated frequency of the insertion allele was 0.45 in hypertensive and 0.42 in normotensive subjects. The difference was not statistically significant. The results indicate a lack of association between ACE I/D polymorphism and essential hypertension in this Greek population, suggesting that other genes must contribute to the pathogenesis of hypertension.

Nitric oxide dysfunction in vascular endothelium and platelets: role in essential hypertension.

Both endothelial and platelet-derived nitric oxide have important vasculoprotective properties. Increasing evidence suggests a dysfunctional platelet nitric oxide synthase type 3 (NOS3) pathway in essential hypertension, whereas for endothelial-derived nitric oxide the picture is more complicated, with many studies suggesting an impairment of endothelial nitric oxide generation, whilst others have suggested that the endothelial nitric oxide pathway is preserved. Controversy also exists as to whether any observed reduction in endothelial or platelet-derived nitric oxide exerts a pathogenetic role or is simply the result of the raised blood pressure. In this review, we examine the evidence that endothelial and/or platelet-derived nitric oxide are disturbed in essential hypertension, and whether such disturbances are cause or effect.

Platelet Activation in Essential Hypertension: Implications for Antiplatelet Treatment

Essential hypertension is associated with increased risk of arterial thrombotic disease. Among other factors, enhanced platelet activity contributes significantly to this phenomenon. An increased level of circulating monocyte-platelet aggregates (MPAs) represents one of the most robust markers of platelet activation; furthermore, these aggregates are also believed to contribute to the pathophysiology of atherothrombotic disease. Putative mechanisms that contribute to platelet activation in essential hypertension include endothelial dysfunction, neurohumoral (sympathetic and renin-angiotensin systems) overactivity, decreased platelet nitric oxide (NO) biosynthesis, and platelet degranulation secondary to increased shear. Current recommendations are that hypertensive patients receive aspirin therapy only if their calculated cardiovascular risk is high and their blood pressure (BP) is adequately controlled. By contrast, the use of antiplatelet treatment in low-risk hypertensive patients is not established and merits further investigation. Moreover, the place of alternative antiplatelet agents other than aspirin, such as clopidogrel, is unclear at present. Some experimental evidence suggests that clopidogrel may confer an additive protective effect over and above aspirin in hypertensive patients, by virtue of effects on the evolution of the atherosclerotic process. This now needs to be investigated in long-term clinical outcome studies.

The interaction of vasoactive substances during exercise modulates platelet aggregation in hypertension and coronary artery disease.

BackgroundAcute vigorous exercise, associated with increased release of plasma catecholamines, transiently increases the risk of primary cardiac arrest. We tested the effect of acute submaximal exercise on vasoactive substances and their combined result on platelet function.MethodsHealthy volunteers, hypertensive patients and patients with coronary artery disease (CAD) performed a modified treadmill exercise test. We determined plasma catecholamines, thromboxane A2, prostacyclin, endothelin-1 and platelet aggregation induced by adenosine diphosphate (ADP) and collagen at rest and during exercise.ResultsOur results during exercise showed a) platelet activation (increased thromboxane B2, TXB2), b) increased prostacyclin release from endothelium and c) decreased platelet aggregation in all groups, significantly more in healthy volunteers than in patients with CAD (with hypertensives lying in between these two groups).ConclusionDespite the pronounced activation of Sympathetic Nervous System (SNS) and increased TXB2 levels during acute exercise platelet aggregation decreases, possibly to counterbalance the prothrombotic state. Since this effect seems to be mediated by the normal endothelium (through prostacyclin and nitric oxide), in conditions characterized by endothelial dysfunction (hypertension, CAD) reduced platelet aggregation is attenuated, thus posing such patients in increased risk for thrombotic complications.

Benefits from Treatment and Control of Patients with Resistant Hypertension

Resistant hypertension is commonly found in everyday clinical practice. However, the risks of resistant hypertension, as well as the benefits of treatment and control of blood pressure in patients with resistant hypertension remain vaguely clarified. Data from small clinical studies and observational cohorts suggest that patients with resistant hypertension are at increased cardiovascular risk, while control of blood pressure offers substantial benefits. It has to be noted however that data from appropriate large randomized studies are missing, and resistant hypertension remains remarkably understudied. Resistant hypertension has attracted significant scientific interest lately, as new therapeutic modalities become available. The interventional management of resistant hypertension either by carotid baroreceptor stimulation or renal sympathetic denervation is currently under investigation with promising preliminary results. This review presents available evidence regarding the benefits of treatment and control of blood pressure in patients with resistant hypertension and offers a critical evaluation of existing data in this field.

Carotid Baroreceptor Stimulation for the Treatment of Resistant Hypertension

Interventional activation of the carotid baroreflex has been an appealing idea for the management of resistant hypertension for several decades, yet its clinical application remained elusive and a goal for the future. It is only recently that the profound understanding of the complex anatomy and pathophysiology of the circuit, combined with the accumulation of relevant experimental and clinical data both in animals and in humans, has allowed the development of a more effective and well-promising approach. Indeed, current data support a sustained over a transient reduction of blood pressure through the resetting of baroreceptors, and technical deficits have been minimized with a subsequent recession of adverse events. In addition, clinical outcomes from the application of a new implantable device (Rheos) that induces carotid baroreceptor stimulation point towards a safe and effective blood pressure reduction, but longer experience is needed before its integration in the everyday clinical practice. While accumulating evidence indicates that carotid baroreceptor stimulation exerts its benefits beyond blood pressure reduction, further research is necessary to assess the spectrum of beneficial effects and evaluate potential hazards, before the extraction of secure conclusions.

The Unilateral Measurement of Blood Pressure May Mask the Diagnosis or Delay the Effective Treatment of Hypertension

Several studies have indicated the presence of significant interarm blood pressure (BP) differences; this could result in misclassification of BP status. Nevertheless, the findings of these studies were not consistent. This prospective, observational study investigated the presence and magnitude of interarm BP differences and determined the influence of age, gender, arm circumference, smoking, being hypertensive or diabetic, or having a previous history of cardiovascular disease in these differences. The study included 384 subjects, who were patients, ward visitors, and members of the nursing staff of this Department. BP measurements were recorded simultaneously in both arms by using 2 validated, fully automated oscillometric electronic devices. There were significant differences between the right arm and left arm systolic BP (p<0.0005), between right arm and left arm diastolic BP (p<0.05), and between right arm and left arm pulse pressure (p=0.006). The mean interarm differences in systolic and diastolic BP measurements were 1.2 ±5.0 mm Hg and 0.4 ±4.2 mm Hg, respectively. There were 13 subjects (3.4%) and 4 subjects (1.04%) with an interarm systolic and diastolic BP difference of >10 mm Hg, respectively, and a single patient with both interarm systolic and diastolic BP differences of >10 mm Hg (0.26%). None of the studied demographic or clinical characteristics was a significant predictor of interarm systolic and diastolic BP differences. The authors conclude that significant interarm systolic and diastolic BP differences are frequently present. Therefore, the unilateral measurement of BP may mask the diagnosis or delay the effective treatment of hypertension. It is thus recommended that BP should be simultaneously measured in both arms at the initial consultation and the higher of the 2 readings should be used to guide further management decisions.

Lack of an association between angiotensin-converting enzyme gene insertion/deletion polymorphism and ischaemic stroke.

Background and Purpose: Numerous factors have been reported to influence the pathogenesis of stroke. The angiotensin I-converting enzyme (ACE) gene is a candidate gene for atherosclerotic-related diseases. In the present study, the association between the polymorphism of the ACE gene and ischaemic stroke was investigated. Methods: Using polymerase chain reaction techniques, 100 patients (48 males, age 69.3 ± 9.7 years) with cerebral infarction and 100 age- and sex-matched controls were divided into the following three ACE genotypes [deletion (D) and insertion (I)]: II, ID and DD. Results: There was no evidence of any association between the ACE gene polymorphism and the presence of ischaemic stroke (odds ratio 0.874, 95% confidence interval 0.386–1.973). Conclusions: The DD genotype in the human ACE gene does not appear to be a risk factor for ischaemic stroke. Further evaluation in a larger population study is required to examine the possibility of an increased risk of ischaemic stroke in DD homozygotes.

Divergent Retinal Vascular Abnormalities in Normotensive Persons and Patients With Never-Treated, Masked, White Coat Hypertension

BACKGROUND Hypertensive patients with retinal arteriolar abnormalities are at increased risk for cardiovascular events. However, the extent of retinal microvascular changes in naïve, never-treated patients with hypertension of short duration has not been established. In addition to this, the lack of relevant data about other phenotypes of hypertension (masked and white-coat hypertension) determined by ambulatory blood-pressure measurement (ABPM) is notable, despite their relationship to increased cardiovascular risk mediated by underlying target-organ and vascular damage. METHODS We conducted a study in which nonmydriatic retinal photography was used to assess central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) diameters and the retinal arteriovenus ratio (AVR) in a group of 103 individuals with never-treated hypertension of recent (< 1 year) appearance, 28 individuals with masked and 20 with white-coat hypertension, and 50 normotensive individuals, as appropriately classified by ABPM. RESULTS Patients with sustained and masked hypertension had narrower values of CRAE than did normotensive individuals (86.7±10.1 and 87.6±9.2 vs. 94.8±10.6, P < 0.001 and P = 0.02, respectively). The AVR was lower in patients with sustained hypertension (0.736±0.102), masked hypertension (0.716±0.123), and white-coat hypertension (0.739±0.127) than in normotensive subjects (0.820±0.095), P < 0.001, P < 0.001, and P = 0.03, respectively. Both AVR and CRAE were negatively associated with mean systolic and diastolic daytime, nighttime, and 24-hour blood pressures, even after adjustment for other factors. CONCLUSIONS Subtle retinal microvascular signs of pathology are observed in hypertensive patients at early stages of hypertension and in patients with both masked and white coat hypertension. These changes may be indicative or may mediate the differences in cardiovascular mortality in persons with masked and white-coat hypertension, and relevant information about this can be easily accessed with retinal photography.