Arterial compliance by cuff sphygmomanometer. Application to hypertension and early changes in subjects at genetic risk

A new common functional coding variant at the DDC gene change renal enzyme activity and modify renal dopamine function

The intra-renal dopamine (DA) system is highly expressed in the proximal tubule and contributes to Na+ and blood pressure homeostasis, as well as to the development of nephropathy. In the kidney, the enzyme DOPA Decarboxylase (DDC) originating from the circulation. We used a twin/family study design, followed by polymorphism association analysis at DDC locus to elucidate heritable influences on renal DA production. Dense single nucleotide polymorphism (SNP) genotyping across the DDC locus on chromosome 7p12 was analyzed by re-sequencing guided by trait-associated genetic markers to discover the responsible genetic variation. We also characterized kinetics of the expressed DDC mutant enzyme. Systematic polymorphism screening across the 15-Exon DDC locus revealed a single coding variant in Exon-14 that was associated with DA excretion and multiple other renal traits indicating pleiotropy. When expressed and characterized in eukaryotic cells, the 462Gln variant displayed lower Vmax (maximal rate of product formation by an enzyme) (21.3 versus 44.9 nmol/min/mg) and lower Km (substrate concentration at which half-maximal product formation is achieved by an enzyme.)(36.2 versus 46.8 μM) than the wild-type (Arg462) allele. The highly heritable DA excretion trait is substantially influenced by a previously uncharacterized common coding variant (Arg462Gln) at the DDC gene that affects multiple renal tubular and glomerular traits, and predicts accelerated functional decline in chronic kidney disease.

The usefulness of a single arm cuff oscillometric method (Arteriograph) to assess changes in central aortic blood pressure and arterial stiffness by antihypertensive treatment: results from the Doxazosin-Ramipril Study

PURPOSE

Inhibition of the renin-angiotensin system may have effects on vascular structure and function beyond the effects on blood pressure (BP) reduction. We studied the ability of a single arm cuff oscillometric method (Arteriograph, TensioMed, Hungary) to assess effects of antihypertensive treatment on BP and arterial stiffness. Furthermore, this technique was compared to pulse wave analysis and applanation tonometry (SphygmoCor, AtCor Medical, Australia).

MATERIALS AND METHODS

Brachial and aortic BP, augmentation index (AIx), and carotid-femoral pulse wave velocity (PWV) was simultaneously assessed by both techniques in 71 untreated hypertensive patients. Thereafter, 58 completed double-blind randomized treatment for 12 weeks with ramipril or doxazosin.

RESULTS

Treatment (assessed by the Arteriograph) reduced aortic more than brachial systolic BP (-13.2 vs. -11.2 mm Hg; p = .002) and improved all indices of arterial stiffness. This greater reduction in aortic to brachial systolic BP was more marked by ramipril than by doxazosin (-20.9 and -17.1 vs. -4.3 and -4.2 mm Hg; p = .006), with a similar trend for AIx (-6.2 vs. -2.2%; p = .058). Both devices showed correlations for aortic and brachial systolic and diastolic BP and AIx (r = 0.75-0.86, all p < .001), while agreement for PWV was weaker (r = 0.28; p = .043). The Arteriograph generally recorded higher values for aortic BP and AIx than the SphygmoCor.

CONCLUSIONS

Antihypertensive treatment reduced aortic systolic BP more than brachial BP and improved arterial stiffness. Blocking the renin-angiotensin system may have additional effects beyond BP reduction. We demonstrate the feasibility of the Arteriograph to monitor changes in BP and arterial stiffness by treatment.

Radial arterial compliance measurement by fiber Bragg grating pulse recorder

In the present work, we report a novel, in vivo, noninvasive technique to determine radial arterial compliance using the radial arterial pressure pulse waveform (RAPPW) acquired by fiber Bragg grating pulse recorder (FBGPR). The radial arterial compliance of the subject can be measured during sphygmomanometric examination by the unique signatures of arterial diametrical variations and the beat-to-beat pulse pressure acquired simultaneously from the RAPPW recorded using FBGPR. This proposed technique has been validated against the radial arterial diametrical measurements obtained from the color Doppler ultrasound. Two distinct trials have been illustrated in this work and the results from both techniques have been found to be in good agreement with each other.

Genetic variation at the delta-sarcoglycan (SGCD) locus elevates heritable sympathetic nerve activity in human twin pairs

The Syrian Cardiomyopathic Hamster (BIO-14.6/53.58 strains) model of cardiac failure, resulting from naturally occurring deletion at the SGCD (delta-sarcoglycan) locus, displays widespread disturbances in catecholamine metabolism. Rare Mendelian myopathy disorders of human SGCD occur, although common naturally occurring SGCD genetic variation has not been evaluated for effects on human norepinephrine (NE) secretion. This study investigated the effect of SGCD genetic variation on control of NE secretion in healthy twin pairs. Genetic associations profiled SNPs across the SGCD locus. Trait heritability (h(2)) and genetic covariance (pleiotropy; shared h(2)) were evaluated. Sympathochromaffin exocytosis in vivo was probed in plasma by both catecholamines and Chromogranin B (CHGB). Plasma NE is substantially heritable (p = 3.19E-16, at 65.2 ± 5.0% of trait variance), sharing significant (p < 0.05) genetic determination with circulating and urinary catecholamines, CHGB, eGFR, and several cardio-metabolic traits. Participants with higher pNE showed significant (p < 0.05) differences in several traits, including increased BP and hypertension risk factors. Peak SGCD variant rs1835919 predicted elevated systemic vascular compliance, without changes in specifically myocardial traits. We used a chimeric-regulated secretory pathway photoprotein (CHGA-EAP) to evaluate the effect of SGCD on the exocytotic pathway in transfected PC12 cells; in transfected cells, expression of SGCD augmented CHGA trafficking into the exocytotic regulated secretory pathway. Thus, our investigation determined human NE secretion to be a highly heritable trait, influenced by common genetic variation within the SGCD locus. Circulating NE aggregates with BP and hypertension risk factors. In addition, coordinate NE and CHGB elevation by rs1835919 implicates exocytosis as the mechanism of release.

Predictors of risk and resilience for posttraumatic stress disorder among ground combat Marines: methods of the Marine Resiliency Study

The Marine Resiliency Study (MRS) is a prospective study of factors predictive of posttraumatic stress disorder (PTSD) among approximately 2,600 Marines in 4 battalions deployed to Iraq or Afghanistan. We describe the MRS design and predeployment participant characteristics. Starting in 2008, our research team conducted structured clinical interviews on Marine bases and collected data 4 times: at predeployment and at 1 week, 3 months, and 6 months postdeployment. Integrated with these data are medical and career histories from the Career History Archival Medical and Personnel System (CHAMPS) database. The CHAMPS database showed that 7.4% of the Marines enrolled in MRS had at least 1 mental health diagnosis. Of enrolled Marines, approximately half (51.3%) had prior deployments. We found a moderate positive relationship between deployment history and PTSD prevalence in these baseline data.

Cardiac and vascular consequences of pre-hypertension in youth

Hypertension is associated with increased left ventricular mass (LVM) and carotid intima-media thickness (cIMT), which predict cardiovascular (CV) events in adults. Whether target organ damage is found in pre-hypertensive youth is not known. The authors measured body mass index, blood pressure, fasting glucose, insulin, lipids and C-reactive protein, LVM/height(2.7) (LVM index), diastolic function, cIMT, carotid stiffness, augmentation index, brachial artery distensibility, and pulse wave velocity (PWV) in 723 patients aged 10 to 23 years (29% with type 2 diabetes mellitus). Patients were stratified by blood pressure level (normotensive: 531, pre-hypertensive: 65, hypertensive: 127). Adiposity and CV risk factors worsened across blood pressure group. There was a graded increase in cIMT, arterial stiffness, and LVM index and decrease in diastolic function from normotension to pre-hypertension to hypertension. In multivariable models adjusted for CV risk factors, status as pre-hypertension or hypertension remained an independent determinant of target organ damage for LVM, diastolic function, internal cIMT, and carotid and arterial stiffness. Pre-hypertension is associated with cardiovascular target organ damage in adolescents and young adults.

Genetic covariance between gamma-glutamyl transpeptidase and fatty liver risk factors: role of beta2-adrenergic receptor genetic variation in twins

BACKGROUND & AIMS

Plasma levels of gamma-glutamyl transpeptidase (GGT) are associated with risk factors for nonalcoholic fatty liver disease (NAFLD), such as dyslipidemia, insulin resistance (IR), and hypertension. Limited data exist on whether there is genetic covariance between plasma levels of GGT and NAFLD risk factors. Variants of beta2-adrenergic receptor gene (ADRB2) have been associated with dyslipidemia, IR, and hypertension, but its effect on GGT secretion is not known. We estimated the heritability of GGT using a twin-study design and examined the genetic covariance between GGT levels, IR, hypertension, levels of low-density lipoproteins and triglycerides, and ADRB2 variants.

METHODS

We studied phenotypes of 362 twins; the heritabilities of increased GGT activity and genetic covariance with NAFLD risk factors were estimated by variance-component methodology. ADRB2 genotype associations with plasma GGT activity were examined using generalized estimating equations to account for intra-twinship correlations.

RESULTS

GGT activity was heritable at 49% +/- 8% of the twin cohort and had significant covariance with IR; insulin, triglyceride, and uric acid levels; and diastolic blood pressure. In generalized estimating equation models, the most common haplotype of ADRB2 was significantly associated with plasma GGT activity. Five single nucleotide polymorphisms in ADRB2 were associated with levels of GGT; ADRB2 haplotypes displayed pleiotropic effects on GGT and triglyceride levels.

CONCLUSIONS

In a twin study, GGT shared genetic codetermination with traits of metabolic syndrome. The ADRB2 gene had pleiotropic effects on plasma levels of GGT and triglycerides, indicating linked pathways (eg, adrenergic) between genetic susceptibility to NAFLD and metabolic syndrome.

Changes in endothelial dysfunction and associated cardiovascular disease morbidity markers in GH-IGF axis pathology

Arterial endothelial dysfunction is an early event in the pathogenesis of atherosclerosis and predisposes individuals to the deposition of unstable atherosclerotic plaques. It can also lead to increased arterial stiffness, which is an accepted cause of increased arterial pulse wave velocity (APWV). Endothelial dysfunction is reversed by recombinant human growth hormone (rhGH) therapy in patients with growth hormone (GH) deficiency (GHD), favorably influencing the risk for atherogenesis. Endogenous human growth hormone (hGH), secreted by the anterior pituitary, and levels of insulin-like growth factor-I (IGF-I), produced in response to hGH stimulation of the liver, peak during early adulthood, but decline throughout adulthood. It is suspected that low-grade inflammatory cardiovascular pathophysiologic markers such as homocysteine, nitric oxide, C-reactive protein (CRP), and fibrinogen and plasminogen activator inhibitor along with changes in lipid and glucose metabolism may all contribute to GHD-associated metabolic and cardiovascular complications. These effects are associated with increased APWV, but are attenuated by rhGH therapy in GHD. GH replacement increases IGF-I levels and reduces CRP and large-artery stiffness. Reviews of rhGH in the somatopause have not been overtly favorable. Whereas reviews of rhGH/rhIGF-I combinations in GH resistance are more positive than those for rhGH alone, their combined use in the somatopause is limited. Senescent individuals may benefit from such a combination.

Dopamine D1 receptor (DRD1) genetic polymorphism: pleiotropic effects on heritable renal traits

Because dopamine D(1) receptors (DRD1) influence renal sodium transport and vascular hemodynamics, we examined whether genetic polymorphisms play a role in renal function. We conducted polymorphism discovery across the DRD1 open reading frame and its 5'-UTR and then performed association studies with estimated glomerular filtration rate (eGFR), plasma creatinine (pCr), and fractional excretion of uric acid (FeUA). We used a twin/family group of 428 subjects from 195 families and a replication cohort of 677 patients from the Kaiser health-care organization sampled from the lower percentiles of diastolic blood pressures. Although the coding region lacked common non-synonymous variants, we identified two polymorphisms in the DRD1 5'-UTR (G-94A, A-48G) that occurred with frequencies of 15 and 30%, respectively. In the twin/family study, renal traits were highly heritable, such that DRD1 G-94A significantly associated with eGFR, pCr, and FeUA. Homozygotes for the G-94A minor allele (A/A) exhibited lower eGFR, higher pCr, and lower FeUA. No effects were noted for DRD1 A-48G. Patients in the Kaiser group had similar effects of G-94A on eGFR and pCr. Kidney cells transfected with the -94A variant but not the wild type vectors had increased receptor density. Because the -94A allele is common and may reduce glomerular capillary hydrostatic pressure, G-94A profiling may aid in predicting survival of renal function in patients with progressive renal disease.

Arterial pulse wave velocity, inflammatory markers, pathological GH and IGF states, cardiovascular and cerebrovascular disease

Blood pressure (BP) measurements provide information regarding risk factors associated with cardiovascular disease, but only in a specific artery. Arterial stiffness (AS) can be determined by measurement of arterial pulse wave velocity (APWV). Separate from any role as a surrogate marker, AS is an important determinant of pulse pressure, left ventricular function and coronary artery perfusion pressure. Proximal elastic arteries and peripheral muscular arteries respond differently to aging and to medication. Endogenous human growth hormone (hGH), secreted by the anterior pituitary, peaks during early adulthood, declining at 14% per decade. Levels of insulin-like growth factor-I (IGF-I) are at their peak during late adolescence and decline throughout adulthood, mirror imaging GH. Arterial endothelial dysfunction, an accepted cause of increased APWV in GH deficiency (GHD) is reversed by recombinant human (rh) GH therapy, favorably influencing the risk for atherogenesis. APWV is a noninvasive method for measuring atherosclerotic and hypertensive vascular changes increases with age and atherosclerosis leading to increased systolic blood pressure and increased left ventricular hypertrophy. Aerobic exercise training increases arterial compliance and reduces systolic blood pressure. Whole body arterial compliance is lowered in strength-trained individuals. Homocysteine and C-reactive protein are two inflammatory markers directly linked with arterial endothelial dysfunction. Reviews of GH in the somatopause have not been favorable and side effects of treatment have marred its use except in classical GHD. Is it possible that we should be assessing the combined effects of therapy with rhGH and rhIGF-I? Only multiple intervention studies will provide the answer.

Heritability and genome-wide linkage in US and australian twins identify novel genomic regions controlling chromogranin a: implications for secretion and blood pressure

BACKGROUND

Chromogranin A (CHGA) triggers catecholamine secretory granule biogenesis, and its catestatin fragment inhibits catecholamine release. We approached catestatin heritability using twin pairs, coupled with genome-wide linkage, in a series of twin and sibling pairs from 2 continents.

METHODS AND RESULTS

Hypertensive patients had elevated CHGA coupled with reduction in catestatin, suggesting diminished conversion of precursor to catestatin. Heritability for catestatin in twins was 44% to 60%. Six hundred fifteen nuclear families yielded 870 sib pairs for linkage, with significant logarithm of odds peaks on chromosomes 4p, 4q, and 17q. Because acidification of catecholamine secretory vesicles determines CHGA trafficking and processing to catestatin, we genotyped at positional candidate ATP6N1, bracketed by peak linkage markers on chromosome 17q, encoding a subunit of vesicular H(+)-translocating ATPase. The minor allele diminished CHGA secretion and processing to catestatin. The ATP6N1 variant also influenced blood pressure in 1178 individuals with the most extreme blood pressure values in the population. In chromaffin cells, inhibition of H(+)-ATPase diverted CHGA from regulated to constitutive secretory pathways.

CONCLUSIONS

We established heritability of catestatin in twins from 2 continents. Linkage identified 3 regions contributing to catestatin, likely novel determinants of sympathochromaffin exocytosis. At 1 such positional candidate (ATP6N1), variation influenced CHGA secretion and processing to catestatin, confirming the mechanism of a novel trans-QTL for sympathochromaffin activity and blood pressure.

Development and validation of a noninvasive method to estimate cardiac output using cuff sphygmomanometry

BACKGROUND

Obtaining cardiac output (CO) measurements noninvasively during routine blood pressure recording can improve hypertension management. A new method has been developed that estimates cardiac output using pulse-waveform analysis (PWA) from a brachial cuff sphygmomanometer. This study evaluates the ability of PWA to track changes in CO as derived by Doppler ultrasound during dobutamine stimulation.

HYPOTHESIS

This study aims to validate the PWA CO estimation over a wide CO range as would be obtained by dobutamine stimulation during Doppler ultrasound evaluation.

METHOD

A total of 48 patients undergoing standard dobutamine stress echocardiography testing for accepted clinical indications were enrolled. Among them, 44 patients (age 36-83, 18 females, 26 males) with good waveform data for analyses provided estimates of CO in this study. Noninvasive measurements of CO were performed using both Doppler ultrasound recordings and PWA techniques simultaneously at each stage of dobutamine infusion.

RESULTS

A total of 207 simultaneous pulse-waveform analyses and Doppler measurements were taken during dobutamine stress on 44 cardiac patients. Linear regression analysis revealed good intra-patient correlation between pulse-waveform analysis and Doppler at different dobutamine-induced CO with coefficients from r = 0.69 to 0.98 (p < 0.05). Analysis of all patients yielded an overall correlation of r = 0.82 (p < 0.001, bias = 0.4 L/min, standard deviation = 1.8 L/min).

CONCLUSION

The CO measured noninvasively from a sphygmomanometer using this PWA method correlates well with those of Doppler through a range of dobutamine-stimulated levels. The CO by PWA should be useful for monitoring hemodynamic changes in hypertensive and cardiac patients during routine blood pressure measurement.

Effects of occupational noise exposure on 24-hour ambulatory vascular properties in male workers

BACKGROUND

Epidemiologic studies have demonstrated that occupational noise exposure is associated with hypertension, but the related mechanism in vascular structural changes is unclear.

OBJECTIVE

This panel study aimed to investigate effects of occupational noise exposure on ambulatory vascular structural properties in male workers.

METHODS

We recruited 20 volunteers and divided them into a high-noise-exposure group of 15 and a low-noise-exposure group of 5 based on environmental noise measurement in an automobile manufacturing company. We determined individual noise exposure and measured personal ambulatory vascular property parameters simultaneously during 24 hr. Linear mixed-effects regression models were used to estimate transient and sustained effects of noise exposure on vascular parameters by adjusting some confounders collected from self-administrated questionnaires and health checkups.

RESULTS

The high-noise-exposed (85 +/- 8 dBA) workers had significantly higher systemic vascular resistance (SVR) than the low-noise-exposed workers (59 +/- 4 dBA) during work and sleep periods. Contrarily, low-noise-exposed workers had significantly higher brachial artery compliance (BAC), brachial artery distensibility (BAD), and systemic vascular compliance (SVC; marginal, p = 0.07) than high-noise-exposed workers during off-duty periods. We also found that high-noise-exposed workers had significantly lower BAC (1.38 +/- 0.55 %mL/mmHg) and BAD (1.29 +/- 0.51 %/mmHg), as well as lower SVC (0.24 +/- 0.10 mL/L/mmHg), but higher SVR (1.93 +/- 0.67 mL/L/min) compared with low-noise-exposed workers over a 24-hr period.

CONCLUSIONS

Our findings suggest that in automobile workers, occupational noise exposure may have sustained, not transient, effects on vascular properties and also enhances the development of hypertension.

Discovery of common human genetic variants of GTP cyclohydrolase 1 (GCH1) governing nitric oxide, autonomic activity, and cardiovascular risk

GTP cyclohydrolase 1 (GCH1) is rate limiting in the provision of the cofactor tetrahydrobiopterin for biosynthesis of catecholamines and NO. We asked whether common genetic variation at GCH1 alters transmitter synthesis and predisposes to disease. Here we undertook a systematic search for polymorphisms in GCH1, then tested variants' contributions to NO and catecholamine release as well as autonomic function in twin pairs. Renal NO and neopterin excretions were significantly heritable, as were baroreceptor coupling (heart rate response to BP fluctuation) and pulse interval (1/heart rate). Common GCH1 variant C+243T in the 3'-untranslated region (3'-UTRs) predicted NO excretion, as well as autonomic traits: baroreceptor coupling, maximum pulse interval, and pulse interval variability, though not catecholamine secretion. In individuals with the most extreme BP values in the population, C+243T affected both diastolic and systolic BP, principally in females. In functional studies, C+243T decreased reporter expression in transfected 3'-UTRs plasmids. We conclude that human NO secretion traits are heritable, displaying joint genetic determination with autonomic activity by functional polymorphism at GCH1. Our results document novel pathophysiological links between a key biosynthetic locus and NO metabolism and suggest new strategies for approaching the mechanism, diagnosis, and treatment of risk predictors for cardiovascular diseases such as hypertension.

On measuring the instantaneous blood pressure in an artery via the tissue control method

This paper presents a non-invasive approach to measuring the instantaneous arterial blood pressure based upon the tissue control method. According to animal experiments, there exists a pressed location where the mean blood pressure in the artery is equivalent to the mean pressure measured on the skin. At this location, the stiffness measured on the skin is equivalent to the stiffness of the tissue only. By means of the tissue control method, the pulsations of the artery are excluded from tissues. The displacement measured on the skin and the tracking pressure obtained from the controller identify the dynamical impedance of the blood vessel, and then estimate the instantaneous intra-arterial blood pressure. The experimental results show that errors of mean blood pressure, systolic blood pressure and diastolic blood pressure are less than 4%, and indicate that the tissue control method is a feasible way to detect the instantaneous arterial blood pressure.

Overweight and Hyperinsulinemia Provide Individual Contributions to Compromises in Brachial Artery Distensibility in Healthy Adolescents and Young Adults: Brachial Distensibility in Children

BACKGROUND: Brachial artery distensibility (BrachD) was measured in healthy children to identify associations with atherosclerotic risk factors. METHODS: 969 black and white subjects 13-22 years were classified as lean (L) or overweight (O) and hyperinsulinemic (H-I) or normoinsulinemic (N-I). BP and BrachD were obtained with a DynaPulse Pathway instrument. ANOVA was performed looking for group mean differences. Correlations between BrachD and risk variables were examined. Determinates of BrachD were determined by backward elimination regression stratified by BMI-Insulin group. RESULTS: Decreased BrachD correlated with male gender, O, higher BP, HR, fasting glucose and log of fasting insulin after adjusting for pulse pressure (PP). BrachD was greatest in L/N-I with progressive decreases seen in L/H-I, O/N-I, and O/H-I subjects. Regression modeling found PP and HR were major determinates of BrachD. Glucose was significant for subjects with N-I regardless of adiposity. Excluding BP, glucose remained important in N-I subjects. Gender was significant for all. HR retained significance only in O subjects regardless of insulin level. CONCLUSIONS: In healthy adolescents, hyperinsulinemia and obesity adversely affect brachial artery function with overweight contributing to a greater degree. In normoinsulinemic subjects, fasting glucose was inversely related to BrachD. Metabolic factors may play a role in vascular function in youth.

C-reactive protein, an 'intermediate phenotype' for inflammation: human twin studies reveal heritability, association with blood pressure and the metabolic syndrome, and the influence of common polymorphism at catecholaminergic/beta-adrenergic pathway loci

BACKGROUND

C-reactive protein (CRP) both reflects and participates in inflammation, and its circulating concentration marks cardiovascular risk. Here we sought to understand the role of heredity in determining CRP secretion.

METHODS

CRP, as well as multiple facets of the metabolic syndrome, were measured in a series of 229 twins, both monozygotic (MZ) and dizygotic (DZ), to estimate trait heritability (h2). Single nucleotide polymorphism (SNP) genotyping was done at adrenergic pathway loci. Haplotypes were inferred from genotypes by likelihood methods. Association of CRP with hypertension and the metabolic syndrome was studied in a larger series of 732 individuals, including 79 with hypertension.

RESULTS

MZ and DZ twin variance components indicated substantial h2 for CRP, at approximately 56 +/- 7% (P < 0.001). CRP was significantly associated (P < 0.05) with multiple features of the metabolic syndrome in twins, including body mass index (BMI), blood pressure (BP), leptin and lipids. In established hypertension, elevated CRP was associated with increased BP, BMI, insulin, HOMA (index of insulin resistance), leptin, triglycerides and norepinephrine. Twin correlations indicated pleiotropy (shared genetic determination) for CRP with BMI (P = 0.0002), leptin (P < 0.001), triglycerides (P = 0.002) and systolic blood pressure (SBP) (P = 0.042). Approximately 9800 genotypes (43 genetic variants at 17 loci) were scored within catecholaminergic pathways: biosynthetic, receptor and signal transduction. Plasma CRP concentration in twins was predicted by polymorphisms at three loci in physiological series within the catecholamine biosynthetic/beta-adrenergic pathway: TH (tyrosine hydroxylase), ADRB1 (beta1-adrenergic receptor) and ADRB2 (beta2-adrenergic receptor). In the TH promoter, common allelic variation accounted for up to approximately 6.6% of CRP inter-individual variance. At ADRB1, variation at Gly389Arg predicted approximately 2.8% of CRP, while ADRB2 promoter variants T-47C and T-20C also contributed. Particular haplotypes and diplotypes at TH and ADRB1 also predicted CRP, though typically no better than single SNPs alone. Epistasis (gene-by-gene interaction) was demonstrated for particular combinations of TH and ADRB2 alleles, consistent with their actions in a pathway in series. In an illustration of pleiotropy, not only CRP but also plasma triglycerides were predicted by polymorphisms at TH (P = 0.0053) and ADRB2 (P = 0.027).

CONCLUSIONS

CRP secretion is substantially heritable in humans, demonstrating pleiotropy (shared genetic determination) with other features of the metabolic syndrome, such as BMI, triglycerides or BP. Multiple, common genetic variants in the catecholaminergic/beta-adrenergic pathway contribute to CRP, and these variants (especially at TH and ADRB2) seem to interact (epistasis) to influence the trait. The results uncover novel pathophysiological links between the adrenergic system and inflammation, and suggest new strategies to probe the role and actions of inflammation within this setting.

Conceptual design of a multi-functional sphygmus detection system

From the energy point of view, obtaining simultaneous blood pressure and flow rate of the radial artery at the wrist is very important for sphygmic diagnosis in medicine. This work depicts the conceptual design for a noninvasive multi-functional sphygmus detection system. According to Y. C. Fung's flow rate equation, flow rate is a function of the diameter of the blood vessel, two adjacent pressures, arterial compliance, the distance between the two adjacent pressures and the viscosity of the blood. Because the distance between the two adjacent pressures is preset and the viscosity is obtained from either a data bank or viscometer, four measuring techniques are proposed to realize the calculation of the flow rate. First, use thermal array sensors and a thermal image identification technique to locate the artery for positioning the sphygmus detection head at wrist and to estimate the diameter of blood vessel as well. Second, detect the delay time between the two adjacent pressures, and then compute the downstream pressure in accordance with the sampled upstream pressure and delay time. Third, employ pressure feedback control to determine the variation of the vessel diameter that in turn can be used to compute the dynamic arterial compliance. Finally, use the nonlinear flow rate equation to calculate the blood flow rate.

Reliability of a noninvasive device to measure systemic hemodynamics in hemodialysis patients

OBJECTIVE

To evaluate the reliability of a noninvasive hemodynamic monitor in hemodialysis patients.

METHODS

We enrolled 15 male patients (mean age 63+/-12 years) on stable chronic hemodialysis. Blood pressure and hemodynamic readings were obtained with the Dynapulse 500 Guardian device (Pulsemetric Inc., San Diego, California, USA), which measures systemic hemodynamics on the basis of oscillometric waveforms obtained through a cuff placed over the brachial artery. Measurements were taken sequentially, in duplicate, before, during and after hemodialysis, in the supine, seated and standing positions on four separate midweek dialysis sessions over a 2-week period.

RESULTS

The repeatability of the method was tested using 200 pairs of valid measurements. The average values (+/-SD) were 137+/-22 mmHg for systolic blood pressure, 80+/-13 mmHg for diastolic blood pressure, 76+/-15 bpm for heart rate, 1320+/-268 mmHg/s for dP/dtmax, 2.8+/-0.5 l/min/m for cardiac index, and 1455+/-359 dyn/s/cm for systemic vascular resistance. The mean differences (+/-SD of the difference) between readings were 0.1+/-10.4 mmHg for systolic blood pressure, 0.3+/-6.0 mmHg for diastolic blood pressure, -0.2+/-8.0 bpm for heart rate, 0.2+/-234 mmHg/s for dP/dtmax, 0.03+/-0.26 l/min/m for cardiac index and -10+/-177 for systemic vascular resistance, yielding limits of agreement (95%) of -20 to 20 mmHg for systolic blood pressure, -11 to 12 mmHg for diastolic blood pressure, -16 to 17 bpm for heart rate, -458 to 458 mmHg/s for dP/dtmax, -0.5 to 0.5 l/min/m for cardiac index and -338 to 357 dyn/s/cm for systemic vascular resistance. Other hemodynamic parameters fared similarly, and coefficients of variation were all between 7 and 18%.

CONCLUSION

We conclude that the Dynapulse 500 Guardian has adequate reliability indices in hemodialysis patients.

Noninvasive detection of vessel stiffness from continuous blood pressure recordings in hypertensive subjects

This paper presents results of blood pressure dynamicity analysis aimed at vessel stiffness detection and subsequent cardiac risk stratification. We analyzed ECG and BP parameters from 12 normotensive young healthy volunteers, 10 old healthy volunteers, and two groups of hypertensive patients -- 12 young non-medicated hypertensive subjects with no other known complications and 16 hypertensive non-medicated subjects with confirmed obesity (according to waist circumference), hyperlipidemia or diabetes mellitus. The dynamic parameters obtained from a derivative continuous blood pressure signal provide additional information about vessel compliance. They can differentiate hypertensive subjects according to the level of cardiovascular risk.

Arterial compliance in elderly men with chronic kidney disease

BACKGROUND/AIM

Chronic kidney disease (CKD) is associated with decreased arterial compliance (AC). The stage of development of impaired arterial function in CKD in relation to loss of glomerular filtration rate (GFR) is not known. This study's aim was to evaluate the relationship between GFR and AC in patients with CKD.

METHODS

We recruited 91 men aged > or =60 years with GFR 15-89 ml/min (mean 47 +/- 21) to evaluate the relationship between GFR and AC in a cross-sectional study. We measured AC at the brachial artery with an oscillometric device (brachial artery distensibility; BAD).

RESULTS

There was no correlation between GFR and BAD (r = 0.08, p = 0.44). When stratified according to CKD stages, all groups showed decreased BAD compared with reference values, and there were no differences among them (one-way ANOVA). Bivariate analyses showed statistically significant correlations between BAD and age (r = -0.23, p = 0.03), antihypertensive drug number (r = 0.27, p = 0.009) and serum hemoglobin (r = 0.24, p = 0.02), but only age and antihypertensive drug number remained significant markers of BAD in a multiple regression model.

CONCLUSION

Older men with CKD have impaired arterial function, but GFR and CKD stage have no relationship to the degree of decrease in brachial artery distensibility.

Methods of assessment of volume status and intercompartmental fluid shifts in hemodialysis patients: implications in clinical practice

Determining dry weight and assessing extracellular fluid volume in hemodialysis (HD) patients is one of the greatest challenges to practicing nephrologists. The clinical examination has limited accuracy, so different strategies have been investigated to aid in this evaluation. Biochemical markers of volume overload (ANP, BNP, cGMP) are fraught with excessive variability and poor correlation with volume status. Inferior vena cava ultrasound is effective, but cumbersome and costly. Bioimpedance measurements of intra- and extracellular water have significant shortcomings when used as isolated measurements, but can be useful in following trends over time and have been shown to improve intradialytic symptoms and blood pressure control. Continuous blood volume monitoring is helpful in preventing intradialytic hypotension and may help identify patients who are volume overloaded and need increased ultrafiltration. In this review we discuss these different techniques and other developments in the evaluation of dry weight and volume status, which may enhance our ability to improve patient stability and well-being during HD sessions.

The effects of low calcium dialysate on arterial compliance and vasoactive substances in patients with hemodialysis

BACKGROUND

Considering that dialysate calcium concentration is potentially a main determinant of the serum ionized calcium level and vasoconstriction is associated with the blood calcium concentration, we conducted a study to evaluate the interdialytic effects of treatment with a low calcium dialysate (LdCa, 1.25 mmol/L) on the changes in arterial compliance (AC), blood pressure (BP), biochemical parameters and vasoactive substances.

METHODS

Eight hemodialysis (HD) patients (mean age: 46.8 +/- 13.7 years, 4 men and 4 women) were included in the study. AC, systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), mean arterial pressure (MAP), serum ionized Ca, intact-PTH, serum nitric oxide and aldosterone were compared after 10 sessions of treatment with LdCa. Right carotid artery diameter was measured 3 times using a real time B-mode ultrasound imager (Hewlett-Packard Sonos 2000) and AC was calculated using the Hayoz method.

RESULTS

1) AC was recorded as 0.140 (0.080-0.170) mm2/kPa at the baseline (1.75 mmol/L calcium dialysate), 0.170 (0.050-0.290) mm2/kPa after LdCa treatment (p < 0.05 versus baseline), and 0.140 (0.070-0.250) mm2/kPa following the HdCa treatment (p < 0.05 versus LdCa data). 2) MAP and PP were calculated at 114.12 +/- 10.56 mmHg and 63.50 +/- 10.87 mmHg at the baseline; 98.37 +/- 15.14 mmHg and 56.50 +/- 5.95 mmHg after LdCa treatment (p < 0.05 versus baseline); and 115.75 +/- 9.64 mmHg and 62.00 +/- 15.71 mmHg following HdCa treatment (p < 0.05 versus LdCa data). 3) Serum ionized Ca and intact-PTH were measured at 4.66 +/- 0.40 mg/dL and 25.08 +/- 16.44 pg/mL at the baseline; 4.45 +/- 0.28 mg/dL and 90.71 +/- 27.03 pg/mL after LdCa treatment (p < 0.05 versus baseline); and 4.65 0.43 mg/dL and 24.08 +/- 15.44 pg/mL following HdCa treatment (p < 0.05 versus LdCa data). 4) Serum aldosterone concentration was 300.8 (65.5-836.1) pg/mL at the baseline, and 220.2 (42.8-527.9) pg/mL after LdCa treatment (p < 0.05).

CONCLUSION

There were favorable changes in AC, BP, biochemical parameters after treatment with LdCa. These changes may be associated with the reduction in serum ionized calcium and decreased serum aldosterone concentration.

Brachial artery distensibility and relation to cardiovascular risk factors in healthy young adults (The Bogalusa Heart Study)

Arterial distensibility decreases with age and atherosclerosis leading to increased pulse pressure (PP) and increased left ventricular work, resulting in left ventricular hypertrophy, a risk factor for cardiovascular morbidity. Brachial artery pulse curve data were collected using the DynaPulse 2000A. Distensibility measured in 920 healthy young adults (40% men, 70% white, age range 18 to 38 years) was compared with levels of cardiovascular risk factors. Laboratory, anthropometric, blood pressure (BP), and heart rate measurements were also obtained. Distensibility tended to decrease with age, reaching significance in women (p <0.05). Whites had greater distensibility adjusted for age than blacks, with women more than men (p <0.05). Distensibility adjusted for PP was negatively correlated with measures of body size, BP, glucose, insulin, low-density lipoprotein cholesterol, very low density lipoprotein cholesterol, and age (p <0.05). When distensibility was plotted as a function of PP to control for distending pressure, the lowest quintiles of systolic, diastolic, and mean arterial BPs tended to have greater distensibility. No differences were seen by quintiles of lipids. In multivariate analyses, BP, age, anthropometric measures, gender, and very low density lipoprotein cholesterol entered the model (r(2) = 0.56; p <0.02). Thus, brachial artery distensibility, which includes a normalization factor to control for body size, showed race and gender differences (whites and women had greater distensibility than blacks and men, respectively), even after adjustment for age. Stiffer vessels with decreased distensibility were seen in subjects with higher levels of cardiovascular risk factors across the range of normal PP. Therefore, noninvasive measures of distensibility are useful in measuring subclinical vascular changes related to arteriosclerosis.

Effects of perindopril on cardiovascular remodeling

The primary aim in the medical treatment of hypertension is to lower blood pressure (BP). A wide variety of agents have proved effective for meeting this goal. However, an ideal agent for management of hypertensive patients must also meet a number of additional criteria. It should have a significant positive impact on conditions that are likely to be associated with elevated BP and that are known risk factors for cardiovascular morbidity and mortality. This article reviews effects of the long-acting angiotensin-converting enzyme inhibitor perindopril erbumine on hypertension-associated blood vessel and myocardial remodeling known to be associated with increased cardiovascular risk. Long-term treatment with perindopril improves arterial compliance and increases the media-lumen ratio of peripheral resistance vessels. These effects appear to be at least partially independent of BP lowering. Reversal of hypertension-associated vascular remodeling with perindopril should decrease afterload and reduce or reverse left ventricular hypertrophy. Evaluation of patients who have received long-term perindopril therapy has shown this to be the case. This effect of perindopril on an important predictor of cardiovascular morbidity and mortality may also be partially independent of BP. The combination of treatment with such agents as perindopril and methods that permit early detection of vascular changes contributing to cardiovascular disease has the potential to markedly improve the prognosis for hypertensive patients and others at risk for development of cardiovascular disease.

Beta2-adrenergic receptor polymorphisms at codon 16, cardiovascular phenotypes and essential hypertension in whites and African Americans

Beta2-adrenergic receptors (beta2-AR) contribute to cardiovascular regulation by influencing several functions and previous studies suggest that a decreased function of the beta2-AR may be involved in essential hypertension. Beta2-AR are polymorphic and certain polymorphisms of these receptors are of functional importance. We focus here on the Arg16-->Gly16 beta2-AR polymorphism, which shows enhanced agonist-promoted downregulation of the receptor and which, in two recent studies, yielded opposite results in terms of association with essential hypertension: an increased frequency of the Gly16 variant in African-Caribbean hypertensives and of the Arg16 variant in offspring of Norwegian white hypertensive parents. In the current study, we genotyped 243 subjects, including both African-American and white individuals, for codon 16 polymorphism and assessed blood pressure and cardiovascular function using impedance cardiography and pressor sensitivity to phenylephrine. We found similar patterns of cardiovascular function and expression of hypertension with the two genotypes of codon 16. There was no statistically significant difference in the overall allelic distribution of the two genotypes: among African-Americans, 51% of the hypertensives and 50% of the normotensives carried the Arg16 allele, whereas among the white subjects 40% of the hypertensives and 47% of the normotensives were carriers of the Arg16 allele. Although we observed a statistically significant increase in the Arg16/Gly16 heterozygotes in the African-American population, the Gly16 allele was not significantly increased in the African-Americans compared to whites. These findings indicate that the codon 16 polymorphisms are not associated with hypertension in a mixed American study population nor do they appear to substantially impact on a variety of hemodynamic variables.

Intradialytic and interdialytic effects of treatment with 1.25 and 1. 75 Mmol/L of calcium dialysate on arterial compliance in patients on hemodialysis

Arterial compliance (AC) is an important determinant of vascular structure, and abnormalities of AC can greatly affect the cardiovascular system. Given the vasoconstrictive properties of increased levels of serum ionized calcium (iCa), we investigated the way that dialysate calcium level can influence AC in the hemodialysis (HD) population. In a crossover randomized design, 19 dialysis patients undergoing regular bicarbonate HD (three times weekly) underwent two cycles of four successive HD sessions each with a low (LdCa; 1.25 mmol/L) and high dialysate calcium concentration (HdCa; 1.75 mmol/L). At the fourth session of each cycle, iCa level and hemodynamic parameters (systolic blood pressure [SBP], diastolic blood pressure, mean arterial pressure [MAP], pulse pressure [PP], heart rate, and AC) were measured pre-HD and post-HD. AC was measured noninvasively at the brachial artery by arterial pulse waveform analysis. The dialysate calcium level was a significant determinant of both pre-HD (r = 0.335; P < 0.05) and post-HD iCa level (r = 0.767; P < 0.001). Pre-HD AC increased significantly (P < 0.05) by 0.01+/- 0.02 mL/mm Hg (7% +/- 19%) on switching from HdCa to LdCa treatment. Multiple regression analysis showed that both pre-HD PP and iCa level were major inverse determinants of pre-HD AC in both the LdCa (R(2) = 0.65; P < 0.001) and HdCa (R(2) = 0.51; P < 0.01) treatment groups. AC increased by 32% (P < 0.01) and 37% (P < 0.05) during LdCa and HdCa dialysis, respectively. Intradialytic changes in AC were inversely correlated with changes in SBP and PP. In the HdCa group, changes in iCa level related significantly to MAP (r = 0.464; P < 0.05). The results show that changes in AC during HD are mainly mediated through concurrent changes of systemic hemodynamics, which are largely affected by dialysate calcium level through parallel changes in iCa level. Interdialytically, a significant, blood pressure-independent, inverse relationship between AC and iCa level exists. Therefore, HD with LdCa, by reducing the incidence of HD-induced hypercalcemia, may have a beneficial role in preventing the ongoing reduction of AC in HD patients and thus improving cardiovascular prognosis.

Heredity and the autonomic nervous system in human hypertension

Because the complex phenotype of human hypertension is at least in part genetically determined, how individual genes ultimately contribute to the disease is not well understood. By contrast, intermediate phenotypes are traits associated with complex disease, but which may display simpler genetic properties such as greater heritability, more consistent and earlier penetrance and bimodality, and may suggest particular candidate susceptibility genes. Because autonomic nervous system activity is altered in hypertension, we examined biochemical, physiologic, and pharmacologic autonomic traits that fulfill at least some of these properties. Such biochemical, physiologic, or pharmacologic autonomic traits may be especially valuable as phenotypic anchor points in linkage or association studies probing the genetic basis of human hypertension.

Aortic pulse wave velocity in young normotensives with a family history of hypertension

OBJECTIVE

To assess the effect of selected clinical and biochemical parameters, with particular consideration of familial hypertension, on the pulse wave velocity (PWV) in young normotensives.

SUBJECTS AND METHODS

Seventy voluntary students were enrolled (mean age 22.3+/-2.1 years), 39 men and 31 women, with normal blood pressure. A history was obtained with respect to diabetes mellitus, ischaemic heart disease, lipid disorders and arterial hypertension in the family. The subjects were subdivided into two groups: those with (n = 33) and without (n = 37) a family history of arterial hypertension, and blood pressure and heart rate were measured three times and total cholesterol and its subfractions determined in plasma. The carotid to femoral PWV was measured using an automatic computerized recorder and analysed by the Complior program.

RESULTS

The subjects with a family history of arterial hypertension had higher blood pressure levels (systolic and diastolic blood pressure, pulse pressure and mean arterial pressure), as well as mean body mass index and low-density lipoprotein (LDL) cholesterol. The PWV in this group did not differ from that in the subjects without a family history of arterial hypertension (9.69+/-2.8 versus 9.32+/-2.0). However, the PWV was significantly higher in males than females (10.62+/-2.2 versus 7.86+/-1.13, P < 0.0001) and there was a significant positive correlation between male gender and PWV.

CONCLUSIONS

Familial arterial hypertension does not significantly affect aortic stiffness in terms of PWV. Male gender in this population of young healthy subjects is one of the most important factors associated with central arterial stiffness.