Differential activation of cardiac and peripheral sympathetic nervous system by nifedipine: role of pharmacokinetics

Calcium channel blockers for preventing cardiomyopathy due to iron overload in people with transfusion-dependent beta thalassaemia

BACKGROUND

Beta-thalassaemia is an inherited blood disorder that reduces the production of haemoglobin. The most severe form requires recurrent blood transfusions, which can lead to iron overload. Cardiovascular dysfunction caused by iron overload is the leading cause of morbidity and mortality in people with transfusion-dependent beta-thalassaemia. Iron chelation therapy has reduced the severity of systemic iron overload, but removal of iron from the myocardium requires a very proactive preventive strategy. There is evidence that calcium channel blockers may reduce myocardial iron deposition. This is an update of a Cochrane Review first published in 2018.

OBJECTIVES

To assess the effects of calcium channel blockers plus standard iron chelation therapy, compared with standard iron chelation therapy (alone or with a placebo), on cardiomyopathy due to iron overload in people with transfusion-dependent beta thalassaemia.

SEARCH METHODS

We searched the Cochrane Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books, to 13 January 2022. We also searched ongoing trials databases and the reference lists of relevant articles and reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of calcium channel blockers combined with standard chelation therapy versus standard chelation therapy alone or combined with placebo in people with transfusion-dependent beta thalassaemia.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. We used GRADE to assess certainty of evidence.

MAIN RESULTS

We included six RCTs (five parallel-group trials and one cross-over trial) with 253 participants; there were 126 participants in the amlodipine arms and 127 in the control arms. The certainty of the evidence was low for most outcomes at 12 months; the evidence for liver iron concentration was of moderate certainty, and the evidence for adverse events was of very low certainty. Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may have little or no effect on cardiac T2* values at 12 months (mean difference (MD) 1.30 ms, 95% confidence interval (CI) -0.53 to 3.14; 4 trials, 191 participants; low-certainty evidence) and left ventricular ejection fraction (LVEF) at 12 months (MD 0.81%, 95% CI -0.92% to 2.54%; 3 trials, 136 participants; low-certainty evidence). Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may reduce myocardial iron concentration (MIC) after 12 months (MD -0.27 mg/g, 95% CI -0.46 to -0.08; 3 trials, 138 participants; low-certainty evidence). The results of our analysis suggest that amlodipine has little or no effect on heart T2*, MIC, or LVEF after six months, but the evidence is very uncertain. Amlodipine plus standard iron chelation compared with standard iron chelation (alone or with placebo) may increase liver T2* values after 12 months (MD 1.48 ms, 95% CI 0.27 to 2.69; 3 trials, 127 participants; low-certainty evidence), but may have little or no effect on serum ferritin at 12 months (MD 0.07 μg/mL, 95% CI -0.20 to 0.35; 4 trials, 187 participants; low-certainty evidence), and probably has little or no effect on liver iron concentration (LIC) after 12 months (MD -0.86 mg/g, 95% CI -4.39 to 2.66; 2 trials, 123 participants; moderate-certainty evidence). The results of our analysis suggest that amlodipine has little or no effect on serum ferritin, liver T2* values, or LIC after six months, but the evidence is very uncertain. The included trials did not report any serious adverse events at six or 12 months of intervention. The studies did report mild adverse effects such as oedema, dizziness, mild cutaneous allergy, joint swelling, and mild gastrointestinal symptoms. Amlodipine may be associated with a higher risk of oedema (risk ratio (RR) 5.54, 95% CI 1.24 to 24.76; 4 trials, 167 participants; very low-certainty evidence). We found no difference between the groups in the occurrence of other adverse events, but the evidence was very uncertain. No trials reported mortality, cardiac function assessments other than echocardiographic estimation of LVEF, electrocardiographic abnormalities, quality of life, compliance with treatment, or cost of interventions.

AUTHORS' CONCLUSIONS

The available evidence suggests that calcium channel blockers may reduce MIC and may increase liver T2* values in people with transfusion-dependent beta thalassaemia. Longer-term multicentre RCTs are needed to assess the efficacy and safety of calcium channel blockers for myocardial iron overload, especially in younger children. Future trials should also investigate the role of baseline MIC in the response to calcium channel blockers, and include a cost-effectiveness analysis.

Sympathetic hyperactivity in patients with hypertension: pathogenesis and treatment. Part II

The second part of the review considers different classes of drugs affecting blood pressure in increased activity of the sympathetic nervous system. Additional possibilities are discussed on how to reduce the negative effect of sympathetic hyperactivity on cardiovascular system and improve the prognosis.

Ethnic comparison in takotsubo syndrome: novel insights from the International Takotsubo Registry

Background

Ethnic disparities have been reported in cardiovascular disease. However, ethnic disparities in takotsubo syndrome (TTS) remain elusive. This study assessed differences in clinical characteristics between Japanese and European TTS patients and determined the impact of ethnicity on in-hospital outcomes.

Methods

TTS patients in Japan were enrolled from 10 hospitals and TTS patients in Europe were enrolled from 32 hospitals participating in the International Takotsubo Registry. Clinical characteristics and in-hospital outcomes were compared between Japanese and European patients.

Results

A total of 503 Japanese and 1670 European patients were included. Japanese patients were older (72.6 ± 11.4 years vs. 68.0 ± 12.0 years; p < 0.001) and more likely to be male (18.5 vs. 8.4%; p < 0.001) than European TTS patients. Physical triggering factors were more common (45.5 vs. 32.0%; p < 0.001), and emotional triggers less common (17.5 vs. 31.5%; p < 0.001), in Japanese patients than in European patients. Japanese patients were more likely to experience cardiogenic shock during the acute phase (15.5 vs. 9.0%; p < 0.001) and had a higher in-hospital mortality (8.2 vs. 3.2%; p < 0.001). However, ethnicity itself did not appear to have an impact on in-hospital mortality. Machine learning approach revealed that the presence of physical stressors was the most important prognostic factor in both Japanese and European TTS patients.

Conclusion

Differences in clinical characteristics and in-hospital outcomes between Japanese and European TTS patients exist. Ethnicity does not impact the outcome in TTS patients. The worse in-hospital outcome in Japanese patients, is mainly driven by the higher prevalence of physical triggers.

Trial Registration

URL: https://www.clinicaltrials.gov; Unique Identifier: NCT01947621.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01857-4.

Sympathetic neural modulation of arterial stiffness in humans

Elevated large-artery stiffness is recognized as an independent predictor of cardiovascular and all-cause mortality. The mechanisms responsible for such stiffening are incompletely understood. Several recent cross-sectional and acute experimental studies have examined whether sympathetic outflow, quantified by microneurographic measures of muscle sympathetic nerve activity (MSNA), can modulate large-artery stiffness in humans. A major methodological challenge of this research has been the capacity to evaluate the independent neural contribution without influencing the dynamic blood pressure dependence of arterial stiffness. The focus of this review is to summarize the evidence examining 1) the relationship between resting MSNA and large-artery stiffness, as determined by carotid-femoral pulse wave velocity or pulse wave reflection characteristics (i.e., augmentation index) in men and women; 2) the effects of acute sympathoexcitatory or sympathoinhibitory maneuvers on carotid-femoral pulse wave velocity and augmentation index; and 3) the influence of sustained increases or decreases in sympathetic neurotransmitter release or circulating catecholamines on large-artery stiffness. The present results highlight the growing evidence that the sympathetic nervous system is capable of modulating arterial stiffness independent of prevailing hemodynamics and vasomotor tone.

Comparison of short-acting versus extended-release nifedipine: Effects on hemodynamics and sympathetic activity in patients with stable coronary artery disease

We investigated the impact of short-acting and extended release nifedipine on sympathetic activity using radiotracer methodology in patients with stable coronary artery disease in order to more accurately document the response of the sympathetic nervous system to different formulations of this dihydropyridine calcium channel antagonist. Participants were randomized to placebo, short-acting or extended release nifedipine for 7–10 days. On the final day, systemic blood pressure, cardiac filling pressures, cardiac output, plasma norepinephrine (NE) and total body NE spillover were measured at baseline (time 0) and repeated at intervals for 6 hours. There were no differences in baseline measures between groups. Following the morning dose of study medication there were no changes in hemodynamics or sympathetic activity in the placebo group. However, there was a significant fall in blood pressure and a significant increase in total body NE spillover in both nifedipine groups. Importantly, the increase in sympathetic activity in response to short-acting nifedipine began earlier (30 minutes) and was much greater than that observed in the extended release group, which occurred later (270 minutes). These findings confirm that sustained therapy with nifedipine is associated with activation of the sympathetic nervous system which is dependent on the pharmacokinetics of the formulation.

Österreichischer Blutdruckkonsens 2019

Erhöhter Blutdruck bleibt eine Hauptursache von kardiovaskulären Erkrankungen, Behinderung und frühzeitiger Sterblichkeit in Österreich, wobei die Raten an Diagnose, Behandlung und Kontrolle auch in rezenten Studien suboptimal sind. Das Management von Bluthochdruck ist eine häufige Herausforderung für Ärztinnen und Ärzte vieler Fachrichtungen. In einem Versuch, diagnostische und therapeutische Strategien zu standardisieren und letztendlich die Rate an gut kontrollierten Hypertoniker/innen zu erhöhen und dadurch kardiovaskuläre Erkrankungen zu verhindern, haben 13 österreichische medizinische Fachgesellschaften die vorhandene Evidenz zur Prävention, Diagnose, Abklärung, Therapie und Konsequenzen erhöhten Blutdrucks gesichtet. Das hier vorgestellte Ergebnis ist der erste Österreichische Blutdruckkonsens. Die Autoren und die beteiligten Fachgesellschaften sind davon überzeugt, daß es einer gemeinsamen nationalen Anstrengung bedarf, die Blutdruck-assoziierte Morbidität und Mortalität in unserem Land zu verringern.

CMR feature tracking in cardiac asymptomatic systemic sclerosis: Clinical implications

Background

Impaired myocardial deformation has been sporadically described in cardiac asymptomatic systemic sclerosis (SSc). We aimed to study myocardial deformation indices in cardiac asymptomatic SSc patients using cardiac magnetic resonance feature tracking (CMR-FT) and correlate these findings to the phenotypic and autoimmune background.

Methods

Fifty-four cardiac asymptomatic SSc patients (44 females, 56±13 years), with normal routine cardiac assessment and CMR evaluation, including cine and late gadolinium enhancement (LGE) images, were included. SSc patients were compared to 21 sex- and age- matched healthy controls (17 females; 54±19 years). For CMR-FT analysis, a mid-ventricular slice for LV peak systolic radial and circumferential strain and a 4-chamber view for LV/RV peak systolic longitudinal strain were used.

Results

Twenty-four patients had diffuse cutaneous SSc and 30 limited cutaneous SSc. Thirteen patients had digital ulcers. Median disease duration was 3.6 years. LV ejection fraction was higher in SSc patients compared to controls (62±6% vs. 59±5%, p = 0.01). Four patients had no LGE examination; in the remaining patients LGE was absent in 74%, while 18% had RV insertion fibrosis and 8% evidence of subendocardial infarction. LV longitudinal strain differed in those with insertion fibrosis (-18.0%) and infarction (-16.7%) compared to no fibrosis (-20.3%, p = 0.04). Patients with SSc had lower RV longitudinal strain and strain rate compared to controls (p<0.001 and p = 0.01, respectively). All other strain and strain rate measurements were non-significant between patients and controls.

Conclusions

In cardiac asymptomatic SSc patients with normal routine functional indices, CMR-FT identifies subclinical presence of insertion fibrosis and/or myocardial infarction by impaired LV longitudinal strain. RV derived longitudinal indices were impaired in the patient group. CMR FT indices did not correlate to the patients’ phenotypic and autoimmune features.

Arterial Stiffness Can Be Modulated by Pressure-Independent Mechanisms in Hypertension

Background Effects of short-term interventions on large-artery stiffness assessed by pulse wave velocity (PWV) have mainly been explained by concomitant changes in blood pressure (BP). However, lower body negative pressure, which increases sympathetic activity and has other hemodynamic effects, has a specific effect on PWV in healthy volunteers. Methods and Results We examined effects of lower-limb venous occlusion (LVO), a similar intervention to lower-body negative pressure that reduces BP but increases sympathetic activity and device-guided breathing (DGB), which reduces both BP and sympathetic activity, on PWV in patients with essential hypertension (n=70 after LVO, n=45 after DGB and LVO in random order). The short-acting calcium channel antagonist nifedipine was used as a control for changes in BP. LVO produced a small but significant reduction in mean arterial pressure of 1.8 (95% CI 0.3-3.4) mm Hg. Despite this, aortic and carotid-femoral PWV increased during LVO by 0.8 (0.2-1.4) m/s and 0.7 (0.3-1.05) m/s, respectively. DGB reduced PWV by 1.2 (0.9-1.4) m/s, to a greater extent than did nifedipine 10 mg (reduction of 0.7 [0.1-1.3] m/s, P<0.05 compared with reduction during DGB). This occurred despite a greater decrease in BP with nifedipine compared with DGB. Conclusions Arterial stiffness can be modulated independently of BP over the short term. The mechanism could involve alterations in sympathetic activity or other as yet uncharacterized effects of LVO and DGB.

Calcium channel blockers for preventing cardiomyopathy due to iron overload in people with transfusion-dependent beta thalassaemia

BACKGROUND

Beta thalassaemia is a common inherited blood disorder. The need for frequent blood transfusions in this condition poses a difficult problem to healthcare systems. The most common cause of morbidity and mortality is cardiac dysfunction from iron overload. The use of iron chelation therapy has reduced the severity of systemic iron overload but specific, non-toxic treatment is required for removal of iron from the myocardium.

OBJECTIVES

To assess the effects of calcium channel blockers combined with standard iron chelation therapy in people with transfusion-dependent beta thalassaemia on the amount of iron deposited in the myocardium, on parameters of heart function, and on the incidence of severe heart failure or arrhythmias and related morbidity and mortality.

SEARCH METHODS

We searched the Cochrane Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched ongoing trials databases, and the reference lists of relevant articles and reviews.Date of last search: 24 February 2018.

SELECTION CRITERIA

We included randomised controlled trials of calcium channel blockers combined with standard chelation therapy compared with standard chelation therapy alone or combined with placebo in people with transfusion-dependent beta thalassaemia.

DATA COLLECTION AND ANALYSIS

Two authors independently applied the inclusion criteria for the selection of trials. Two authors assessed the risk of bias of trials and extracted data and a third author verified these assessments. The authors used the GRADE system to assess the quality of the evidence.

MAIN RESULTS

Two randomised controlled trials (n = 74) were included in the review; there were 35 participants in the amlodipine arms and 39 in the control arms. The mean age of participants was 24.4 years with a standard deviation of 8.5 years. There was comparable participation from both genders. Overall, the risk of bias in included trials was low. The quality of the evidence ranged across outcomes from low to high, but the evidence for most outcomes was judged to be low quality.Cardiac iron assessment, as measured by heart T2*, did not significantly improve in the amlodipine groups compared to the control groups at six or 12 months (low-quality evidence). However, myocardial iron concentration decreased significantly in the amlodipine groups compared to the control groups at both six months, mean difference -0.23 mg/g (95% confidence interval -0.07 to -0.39), and 12 months, mean difference -0.25 mg/g (95% confidence interval -0.44 to -0.05) (low-quality evidence). There were no significant differences between treatment and control groups in serum ferritin (low-quality evidence), liver T2* (low-quality evidence), liver iron content (low-quality evidence) and left ventricular ejection fraction (low-quality evidence). There were no serious adverse events reported in either trial; however, one trial (n = 59) reported mild adverse events, with no statistically significant difference between groups (low-quality evidence).

AUTHORS' CONCLUSIONS

The available evidence does not clearly suggest that the use of calcium channel blockers is associated with a reduction in myocardial iron in people with transfusion-dependent beta thalassaemia, although a potential for this was seen. There is a need for more long-term, multicentre trials to assess the efficacy and safety of calcium channel blockers for myocardial iron overload, especially in younger children. Future trials should be designed to compare commonly used iron chelation drugs with the addition of calcium channel blockers to investigate the potential interplay of these treatments. In addition, the role of baseline myocardial iron content in affecting the response to calcium channel blockers should be investigated. An analysis of the cost-effectiveness of the treatment is also required.

Effects of Long- and Intermediate-Acting Dihydropyridine Calcium Channel Blockers in Hypertension: A Systematic Review and Meta-Analysis of 18 Prospective, Randomized, Actively Controlled Trials

BACKGROUND

Dihydropyridine calcium channel blockers are a heterogeneous group of antihypertensive drugs. Long-acting dihydropyridine agent amlodipine is widely used for monotherapy and combination therapy for hypertension in clinical practice, while intermediate-acting dihydropyridine agents have shown inconsistent results in randomized clinical trials (RCTs).

METHODS AND RESULTS

A meta-analysis of 18 RCTs enrolling a total of 80,483 patients with hypertension followed for a mean of 51.4 months was performed. Amlodipine therapy was associated with 25% higher risk of heart failure (relative risk [RR]: 1.25, 95% confidence interval [CI], 1.05-1.49, P = .019) but 17% lower risk of stroke (RR: 0.83, [95% CI, 0.72-0.97], P = .009) without statistically significant effect on acute myocardial infarction (AMI) compared to major alternative antihypertensive therapy (MAAT), including β-blocker, diuretic, angiotensin-converting enzyme inhibitor, or angiotensin-receptor blocker. Intermediate-acting dihydropyridine calcium channel blocker therapy was associated with 25% higher risk of heart failure (RR: 1.25, [95% CI, 1.06-1.47], 0.005, P = .005) and 26% higher risk of AMI (RR: 1.26, [95% CI, 1.05-1.51], 0.019, P = .019) compared to MAAT. Results of the subgroup analysis suggested that the intermediate-acting dihydropyridine calcium channel blocker was associated with higher risk of heart failure (RR: 1.30, [95% CI, 1.08-1.56], P = .005) and AMI (RR: 1.50, [95% CI, 1.01-2.22], P = .043) compared to renin-angiotensin system blockers and a trend toward higher risk of AMI (RR: 1.17, [95% CI, 0.99-1.38], P = .064) compared to conventional therapy, including β-blockers and diuretics. Meta-regression analyses suggested that long-acting dihydropyridine calcium channel blocker is associated with lower risk of AMI ( B: -0.327, [95% CI, -0.530 to -0.123], P = .002) with a trend toward lower risk of stroke ( B: -0.203, [95% CI, -0.410 to 0.003] P = .054).

CONCLUSIONS

This study suggests that Amlodipine offers greater protection against major complications of hypertension compared to intermediate-acting dihydropyridine calcium channel blockers.

Antihypertensive drugs

Successful treatment of hypertension is possible with limited side effects given the availability of multiple antihypertensive drug classes. This review describes the various pharmacological classes of antihypertensive drugs, under two major aspects: their mechanisms of action and side effects. The mechanism of action is analysed through a pharmacological approach, i.e. the molecular receptor targets, the various sites along the arterial system, and the extra-arterial sites of action, in order to better understand in which type of hypertension a given pharmacological class of antihypertensive drug is most indicated. In addition, side effects are described and explained through their pharmacological mechanisms, in order to better understand their mechanism of occurrence and in which patients drugs are contra-indicated. This review does not address the effectiveness of monotherapies in large randomized clinical trials and combination therapies, since these are the matters of other articles of the present issue. Five major pharmacological classes of antihypertensive drugs are detailed here: beta-blockers, diuretics, angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, and calcium channel blockers. Four additional pharmacological classes are described in a shorter manner: renin inhibitors, alpha-adrenergic receptor blockers, centrally acting agents, and direct acting vasodilators.

Sympathomodulatory Effects of Antihypertensive Drug Treatment

BACKGROUND

An activation of sympathetic neural influences to the heart and peripheral circulation has been shown to represent a hallmark of the essential hypertensive state, adrenergic neural factors participating together with other variables at the development and progression of the high blood pressure state as well as of the hypertension-related target organ damage. This represents the rationale for employing in hypertension treatment drugs which combine the blood pressure-lowering properties with the modulatory effects on the sympathetic neural function.

METHODS AND RESULTS

Several studies published during the past 40 years have investigated the impact of antihypertensive drugs on the sympathetic target as assessed by indirect and direct approaches. In the present paper, the effects of different monotherapies or combination drug treatment used in hypertension to lower elevated blood pressure values on various adrenergic markers will be examined. This will be followed by a discussion of the (i) hemodynamic and nonhemodynamic consequences of employing antihypertensive drugs with sympathomodulatory or sympathoexcitatory properties and (ii) mechanisms potentially responsible for the adrenergic responses to a given antihypertensive drug. The final part of this review will address the questions still open related to the impact of antihypertensive drug treatment on sympathetic function. Two questions in particular will be examined, i.e., whether antihypertensive drugs with sympathomodulatory properties may be capable to fully restore a "normal" adrenergic drive and how far sympathetic activity should be reduced in hypertensive patients.

CONCLUSION

Future investigations aimed at answering these questions will be needed in order to improve cardiovascular protection in treated hypertensive patients.

Determination of catecholamines in plasma and urine

For more than 20 years, measurement of catecholamines in plasma and urine in clinical chemistry laboratories has been the cornerstone of the diagnosis of neuroendocrine tumors deriving from the neural crest such as pheochromocytoma (PHEO) and neuroblastoma (NB), and is still used to assess sympathetic stress function in man and animals. Although assay of catecholamines in urine are still considered the biochemical standard for the diagnosis of NB, they have been progressively abandoned for excluding/confirming PHEOs to the advantage of metanephrines (MNs). Nevertheless, catecholamine determinations are still of interest to improve the biochemical diagnosis of PHEO in difficult cases that usually require a clonidine-suppression test, or to establish whether a patient with PHEO secretes high concentrations of catecholamines in addition to metanephrines. The aim of this chapter is to provide an update about the catecholamine assays in plasma and urine and to show the most common pre-analytical and analytical pitfalls associated with their determination.

The effect of sodium restricted diet on plasma visfatin levels in hypertensive patients with visceral obesity

AIM/BACKGROUND

Experimental and clinical studies revealed contradictory data concerning the influence of renin-angiotensin-aldosterone (RAA) system activation on visfatin release. The aim of the present study was the assessment of the effect of dietary sodium restriction with RAA system activation on visfatin level in hypertensive and normotensive patients with visceral obesity.

METHODS

The study included 24 hypertensive patients with visceral obesity (12 women) and 22 normotensive subjects with visceral obesity (11 women) constituting the control group. Plasma renin activity, plasma insulin, aldosterone and visfatin levels were determined twice, on normal-salt diet after 6-8 h in recumbent position and the second time after 3 days of dietary sodium restriction and upright position for 2 h. Dietary compliance was controlled by 24 h natriuresis measurement.

RESULTS

Hypertensive patients had significantly higher plasma visfatin level than the control group [11.0 (8.5-13.5) vs. 6.8 (6.0-7.6) ng/ml, p=0.003]. Dietary sodium restriction and upright position caused significant increase in PRA and plasma aldosterone level in both groups. While, plasma visfatin level remained unaffected. In the combined group plasma visfatin levels correlated with BMI (r=0.398), waist circumference (r=0.391), glucose (r=0.328), insulin (r=0.663), HOMA-IR (r=0.698), triglycerides (r=0.500) and CRP (r=0.546) but not with percentage of fat mass, percentage of trunk fat, and blood pressure values.

CONCLUSIONS

1) Increased plasma visfatin concentration may play a significant role in the pathogenesis of hypertension in patients with visceral obesity. 2) RAA system activation by dietary sodium restriction and upright position has no effect on plasma visfatin levels in subjects with visceral obesity.

Effects of moxonidine on sympathetic nerve activity in patients with end-stage renal disease

OBJECTIVE

End-stage renal disease (ESRD) is characterized by markedly increased sympathetic outflow that contributes to increased cardiovascular mortality in these patients. The central sympatholytic drug moxonidine (MOX) has been shown to reduce muscle sympathetic nerve activity (MSNA) in initial stages of chronic kidney disease; however, the effects in ESRD are not known. The aim of this study was to test the hypothesis that low-dose MOX causes sustained decreases in sympathetic outflow in ESRD patients.

DESIGN AND METHODS

Twenty-three ESRD patients (mean age 46.4 +/- 16 years, 14 men, seven women, no diabetic patients) were randomized to a daily treatment of 0.3 mg MOX or placebo (PLA) in addition to pre-existing antihypertensive therapy. At baseline and after 1 and 6 months of treatment, heart rate (HR, ECG), blood pressure (mean arterial pressure, automatic sphygmanometer), calf blood flow (CBF, venous occlusion plethysmography), muscle sympathetic nerve activity (MSNA) (microneurography at the peroneal nerve) were measured. Data are mean +/- SEM.

RESULTS

MOX acutely decreased MSNA within 2 h after oral intake (from 45 +/- 3.7 to 35 +/- 3.9 bursts/min, P < 0.05). This decrease was sustained over 6 months (MSNA 45 +/- 3.7, 35 +/- 4.6, 33 +/- 4.5 bursts/min at 0, 1 and 6 months, P < 0.05). PLA had no effect. Neither MOX nor PLA resulted in any significant acute or long-term changes in HR, MAP or CBF.

CONCLUSIONS

In ESRD patients, low-dose MOX produced sustained and substantial reductions in sympathetic outflow without hemodynamically compromising them. We suggest that the inhibition of central sympathetic outflow may improve cardiovascular prognosis in ESRD.

Peripheral chemosensor function is blunted in moderate to severe chronic kidney disease

BACKGROUND

Cardiovascular mortality is markedly increased in chronic kidney disease (CKD) and may be explained in part by sympathetic hyperactivity. Impaired hyperoxic chemoreflex sensitivity (CHRS) has been attributed to an increased sympathetic tone. The aim of the present study was to examine whether chemosensor function is altered in patients with CKD.

METHODS AND RESULTS

We assessed CHRS in 20 patients with stage 3 CKD [glomerular filtration rate (GFR) 30-59 ml/min/1.73 m(2)], in 15 patients with stage 4 CKD [GFR 15-29 ml/min/1.73 m(2)], as well as in 35 age and gender matched patients without any evidence of CKD. The difference in the R-R intervals divided by the difference in the oxygen pressures before and after deactivation of the chemoreceptors by inhalation of pure oxygen was calculated as the CHRS. A CHRS below 3.0 ms/mmHg was defined as pathological. CHRS was significantly depressed in patients with stage 3 CKD (2.9 ± 0.9 ms/mmHg, P=0.005) and in patients with stage 4 CKD (2.1 ± 0.6 ms/mmHg, P<0.001), as compared with patients without CKD (6.7 ± 0.9 ms/mmHg). There was a negative correlation between serum creatinine and CHRS (r=-0.51; P<0.001). In patients with CKD, chemosensor deactivation decreased mean arterial pressure from 91 ± 4 mmHg to 87 ± 3 mmHg (P=0.03). Multivariate analysis showed that GFR (P=0.001) was the only independent predictor of a pathological CHRS.

CONCLUSION

Using a relatively non-invasive bedside test we provide evidence for a blunted peripheral chemosensor function in chronic kidney disease. We thereby lay the basis for interventional studies assessing chemosensor function in chronic kidney disease.

Sympathetic neural activity in hypertension and related diseases

BACKGROUND

Several hemodynamic variables, such as blood pressure, vascular resistance, cardiac output, and heart rate, are regulated, among others, by sympathetic cardiovascular influences. This has led many years ago investigators to advance the hypothesis that alterations in the sympathetic modulation of the cardiovascular system may occur in hypertension and related disease.

METHODS

The role of the sympathetic nervous system as promoter and amplifier of the hypertensive state has been examined in a consistent number of studies carried out by making use of sophisticated and sensitive approaches to evaluate adrenergic function, such as the norepinephrine spillover technique and the recording of efferent postganglionic muscle sympathetic-nerve traffic.

RESULTS

The results of the above-mentioned investigations support the concept that adrenergic activation characterizes essential hypertension, correlating with the clinical severity of the disease. Furthermore, sympathetic cardiovascular influences may favor the hypertensive disease progression, by concurring with other hemodynamic and nonhemodynamic factors at the development of target organ damage. Finally, an adrenergic overdrive of pronounced degree also characterizes hypertension-related cardiovascular and metabolic disease. In several of these clinical conditions, the adrenergic overdrive plays a role in the disease's physiopathology and prognosis.

CONCLUSIONS

The data reviewed in this article provide evidence that sympathetic activation represents a hallmark of the essential hypertensive state. They further show that adrenergic neural factors may participate at the development and progression of the hypertensive state and its complications. This represents the rationale for the use of antihypertensive and, in more in general, cardiovascular drugs capable to exert sympatho-inhibitory effects.

Sympathetic hyperactivity influences chemosensor function in patients with end-stage renal disease

Background

Autonomic neuropathy is common in patients suffering from end-stage renal disease (ESRD). This may in part explain the high cardiovascular mortality in these patients. Chemosensory function is involved in autonomic cardiovascular control and is mechanistically linked to the sympathetic tone.

Objective

The aim of the present study was to assess whether sympathetic hyperactivity contributes to an altered chemosensory function in ESRD.

Materials and methods

In a randomized, double-masked, placebo controlled crossover design we studied the impact of chemosensory deactivation on heart rate, blood pressure and oxygen saturation in 10 ESRD patients and 10 age and gender matched controls. The difference in the R-R intervals divided by the difference in the oxygen pressures before and after deactivation of the chemoreceptors by 5-min inhalation of 7 L oxygen was calculated as the hyperoxic chemoreflex sensitivity (CHRS). Placebo consisted of breathing room air. Baseline sympathetic activity was characterized by plasma catecholamine levels and 24-h time-domain heart rate variability (HRV) parameters.

Results

Plasma norepinephrine levels were increased (1.6 ± 0.4 vs. 5.8 ± 0.6; P < 0.05) while the SDNN (standard deviation of all normal R-R intervals: 126.4 ± 19 vs. 100.2 ± 12 ms), the RMSSD (square root of the mean of the squared differences between adjacent normal R-R intervals: 27.1 ± 8 vs. 15.7 ± 2 ms), and the 24-h triangular index (33.6 ± 4 vs. 25.7 ± 3; each P < 0.05) were decreased in ESRD patients as compared to controls. CHRS was impaired in ESRD patients (2.9 ± 0.9 ms/mmHg, P < 0.05) as compared to controls (7.9 ± 1.4 ms/mmHg). On multiple regression analysis 24 h-Triangular index, RMSSD, and plasma norepinephrine levels were independent predictors of an impaired hyperoxic CHRS.

Conclusion

Sympathetic hyperactivity influences chemosensory function in ESRD resulting in an impaired hyperoxic CHRS.

Hyperoxic chemoreflex sensitivity is impaired in patients with neurocardiogenic syncope

BACKGROUND

During the development of neurocardiogenic syncope (NCS) postural dependant venous blood pooling sets off a cascade of autonomic reflexes. This causes an initial rise in sympathetic tone, which is followed by an overshoot parasympathetic activation resulting in systemic vasodilatation and/or sinus bradycardia. However, other factors like associated hyperventilation or changes in blood gas content may also contribute to syncope. Hyperoxic cardiac chemoreflex sensitivity (CHRS) is an autonomic functional test that describes the heart rate decrease in response to increases in blood oxygen content. The purpose of this study was to investigate whether CHRS is altered in NCS.

METHODS AND RESULTS

CHRS was compared in 16 NCS patients (49+/-4 yr old) vs. 16 age and gender matched controls (53+/-2 yr old). NCS was verified by clinical syncope and positive head-up tilt testing. The hyperoxic CHRS was measured by determination of the venous partial pressure of oxygen and heart rate before and after 5 min of pure oxygen inhalation. The difference of the R-R intervals before and after oxygen inhalation divided by the difference in the oxygen pressures were calculated as hyperoxic chemoreflex sensitivity [ms/mm Hg]. CHRS in the control group was 7.1+/-1.1 ms/mm Hg. By contrast, CHRS in NCS patients was significantly lower (2.8+/-1.0 ms/mm Hg; p<0.05).

CONCLUSION

Neurocardiogenic syncope is associated with decreased hyperoxic cardiac chemoreflex sensitivity possibly reflecting impaired deactivation of arterial chemoreceptors. The clinical and pathophysiologic importance of chemosensor function in neurocardiogenic syncope needs to be investigated in more detail.

Long-acting nifedipine in the management of the hypertensive patient

Hypertension is a global condition affecting billions worldwide. It is a significant contributor to cardiovascular events, cardiac death and kidney disease. A number of medication classes exist to aid healthcare providers and their patients in controlling hypertension. Nifedipine, a dihydropyridine calcium channel blocker, was once one of the most widely used medications for hypertension, but safety and tolerability concerns along with the introduction of new classes of antihypertensive medications and an increasing pool of data showing mortality benefit of other classes caused nifedipine to fall out of favor. More recently, long-acting formulations were developed and made available to clinicians. These newer formulations were designed to address many of the concerns raised by earlier formulations of nifedipine. Numerous clinical trials have been conducted comparing long-acting nifedipine to many of the more commonly prescribed antihypertensive medications. This review will address the pharmacology, pharmacokinetics and the available clinical trial data on long-acting nifedipine and summarize its role in the management of hypertension.

Treatment of hypertension in patients with diabetes mellitus

Antihypertensive treatment in diabetes mellitus, especially in diabetics known to have cardiac autonomic neuropathy, may have to consider the status of the autonomic nervous system. In diabetic subjects with cardiac autonomic neuropathy, vagal activity during the night is often reduced. The reduction results in relative or absolute sympathetic activation, which could increase cardiovascular risk. Pathophysiological and clinical data suggests that antihypertensive treatment should reduce rather than induce sympathetic activity in this setting. Beta blocking agents, ACE inhibitors, calcium antagonists of verapamil or diltiazem type and selective imidazoline receptor agonists reduce sympathetic activity and, therefore, may have a beneficial effect in diabetic patients with disturbed sympathovagal balance.

Sympathetic nerve activity in renal transplant patients before and after withdrawal of cyclosporine

BACKGROUND

It has been suggested that the increase in blood pressure observed in transplant patients treated with cyclosporine is mediated by cyclosporine-induced sympathoexcitation. However, the chronic effects of cyclosporine on sympathetic outflow in renal transplant patients have not been investigated. Therefore we studied sympathetic nerve activity and blood pressure before and 6 months after the withdrawal of cyclosporine in renal transplant patients.

METHODS

Twenty-four renal transplant patients with histologically confirmed chronic allograft nephropathy (age 48 +/- 3 years, 60 +/- 10 months after transplantation) were included in the prospective study and randomly assigned to either withdrawal (n = 12) or continuation (n = 12) of cyclosporine. Both groups received mycophenolate mofetil and prednisolone as additional immunosuppressants. At entry and 6 months later blood pressure, muscle sympathetic nerve activity (MSNA), and plasma norepinephrine were measured. To assess the potential influence of the diseased native kidneys, three renal transplant patients who had their native kidneys removed were studied before and after cyclosporine withdrawal.

RESULTS

Mean arterial pressure decreased significantly in the cyclosporine-withdrawal group (95 +/- 4 versus 105 +/- 4 mmHg 6 versus 0 months, P < 0.05) but not in the cyclosporine-continuation group (103 +/- 3 versus 105 +/- 4 mmHg, NS). However, plasma norepinephrine and MSNA did not change significantly in either group (MSNA 43 +/- 4 versus 44 +/- 3 and 38 +/- 5 versus 39 +/- 4 bursts/min in the cyclosporine-withdrawal and cyclosporine-continuation groups, NS). Graft function remained stable in both groups and in transplant patients who had their native kidneys removed MSNA did not decrease after cyclosporine withdrawal.

CONCLUSION

The withdrawal of cyclosporine in renal transplant patients, receiving relatively low doses of cyclosporine, resulted in a substantial decrease in blood pressure. However, MSNA and norepinephrine did not change. This suggests that cyclosporine treatment does not cause chronic sympathetic activation that could explain the cyclosporine-induced blood pressure elevation in renal transplant patients.

Modified-release nifedipine: a review of the use of modified-release formulations in the treatment of hypertension and angina pectoris

Nifedipine is a dihydropyridine calcium channel antagonist with predominantly vasodilatory activity. Modified-release formulations of nifedipine are effective antihypertensive and antianginal therapies and are generally well tolerated. Among the available formulations, those that produce a gradual increase in plasma nifedipine concentration, which is then sustained over a 24-hour period, are preferred, as they cause a gradual onset of vasodilatation and avoid baroreflex sympathetic activation (for example, nifedipine gastrointestinal therapeutic system [GITS] and a Japanese controlled-release formulation). Modified-release nifedipine had beneficial effects on a number of markers of vascular function, and nifedipine GITS reduced the need for coronary procedures in patients with coronary artery disease. In patients with hypertension, nifedipine GITS and nifedipine retard had beneficial effects on the overall incidence of major cardiovascular events, as did nifedipine retard in patients with concurrent hypertension and coronary artery disease.

Sensitive and simple liquid chromatographic method with ultraviolet detection for the determination of nifedipine in canine plasma

An isocratic high-performance liquid chromatographic method with detection at 240 nm was developed, optimized and validated for the determination of nifedipine in canine plasma. Liquid-liquid extraction was used as the sample preparation technique. Carbamazepine was used as internal standard. A Hypersil BDS RP-C18 column (250 mm x 4.6 mm, 5 microm) was equilibrated with a mobile phase composed of water and methanol, 45:55 (v/v). Its flow rate was 1 ml min(-1). The elution time for nifedipine and carbamazepine was approximately 12 and 8 min, respectively. Calibration curves of nifedipine in plasma were linear in the concentration range of 1-200 ng ml(-1). Limits of detection and quantification in plasma were 0.5 and 1.5 ng ml(-1), respectively. Recovery was greater than 98%. Intra- and inter-day relative standard deviation for nifedipine in plasma was less than 8.5 and 10%, respectively. This method was applied to the determination of nifedipine plasma levels after administration of commercially available soft gelatine capsules to dogs.

Coffee Blunts Mental Stress–Induced Blood Pressure Increase in Habitual but Not in Nonhabitual Coffee Drinkers

Coffee is widely consumed, especially during mental stress conditions. Cardiovascular impact of coffee remains debated because the underlying mechanisms of action are complex. We reported previously differential cardiovascular stimulation of coffee at rest depending on habitual consumption. The present study was designed to evaluate the effects of coffee on cardiovascular response to mental stress. In 15 healthy volunteers (6 habitual, 9 nonhabitual coffee drinkers), we assessed the effect of mental stress on blood pressure (BP), heart rate (HR), and muscle sympathetic activity (MSA) before and after a triple espresso, intravenous caffeine, and placebo in the same subjects. Under baseline conditions, mental stress significantly increases MSA (+2.5±0.7 volts per minute; +14.1±10.3%), systolic (+11.6±4.1 mm Hg) and diastolic BP (+6.4±2.0 mm Hg), and HR (+9.6±1.8 minutes −1 ). In nonhabitual coffee drinkers, a triple espresso but not caffeine induced an additional increase in systolic BP (+9±6.3 mm Hg; P =0.003) during mental stress, whereas in habitual drinkers, the stress-induced BP increase was blunted (+4±3.9 mm Hg; P =NS). As a result, nonhabitual coffee drinkers experienced significantly higher BP during mental stress than habitual drinkers (151±17.9/83±5.6 mm Hg versus 130±7.8/74±6.7 mm Hg; P <0.05). Caffeine induced similar effects in habitual and nonhabitual coffee drinkers at rest and during mental stress. The response to the cold pressor test was not influenced by coffee drinking in both groups. In conclusion, in nonhabitual coffee drinkers, coffee enhances the cardiovascular response to mental stress with an additional increase in systolic BP, whereas in habitual drinkers, the response is blunted. Caffeine alone does not exert any potentiating effect, confirming that ingredients other than caffeine are partially responsible for the stimulating effect of coffee on the cardiovascular system.

Calcium antagonists

Calcium antagonists were introduced for the treatment of hypertension in the 1980s. Their use was subsequently expanded to additional disorders, such as angina pectoris, paroxysmal supraventricular tachycardias, hypertrophic cardiomyopathy, Raynaud phenomenon, pulmonary hypertension, diffuse esophageal spasms, and migraine. Calcium antagonists as a group are heterogeneous and include 3 main classes--phenylalkylamines, benzothiazepines, and dihydropyridines--that differ in their molecular structure, sites and modes of action, and effects on various other cardiovascular functions. Calcium antagonists lower blood pressure mainly through vasodilation and reduction of peripheral resistance. They maintain blood flow to vital organs, and are safe in patients with renal impairment. Unlike diuretics and beta-blockers, calcium antagonists do not impair glucose metabolism or lipid profile and may even attenuate the development of arteriosclerotic lesions. In long-term follow-up, patients treated with calcium antagonists had development of less overt diabetes mellitus than those who were treated with diuretics and beta-blockers. Moreover, calcium antagonists are able to reduce left ventricular mass and are effective in improving anginal pain. Recent prospective randomized studies attested to the beneficial effects of calcium antagonists in hypertensive patients. In comparison with placebo, calcium antagonist-based therapy reduced major cardiovascular events and cardiovascular death significantly in elderly hypertensive patients and in diabetic patients. In several comparative studies in hypertensive patients, treatment with calcium antagonists was equally effective as treatment with diuretics, beta-blockers, or angiotensin-converting enzyme inhibitors. From these studies, it seems that a calcium antagonist-based regimen is superior to other regimens in preventing stroke, equivalent in preventing ischemic heart disease, and inferior in preventing congestive heart failure. Calcium antagonists are also safe and effective as first-line or add-on therapy in diabetic hypertensive patients. Heart rate-lowering calcium antagonists (verapamil, diltiazem) may have an edge over the dihydropyridines in post-myocardial infarction patients and in diabetic nephropathy. Thus, calcium antagonists may be safely used in the management of hypertension and angina pectoris.

Improvement of insulin resistance by troglitazone ameliorates cardiac sympathetic nervous dysfunction in patients with essential hypertension

BACKGROUND

It was recently suggested that insulin resistance is significantly correlated with activation of the cardiac sympathetic nervous system in patients with essential hypertension.

OBJECTIVES

To examine the effects of troglitazone, an agent used to treat insulin resistance, on cardiac sympathetic nervous dysfunction and insulin resistance in patients with essential hypertension.

METHODS

The study participants included 34 patients (14 men, 20 women) with mild essential hypertension and 17 normal controls (group C, seven men). The patients were randomly divided into two groups, one treated with 400 mg troglitazone and antihypertensive drugs (group T, n = 17) and the other treated with antihypertensive drugs only (group N, n = 17). We evaluated insulin resistance and cardiac sympathetic nervous function before and after 6 months of treatment. Insulin resistance was evaluated using steady-state plasma glucose (SSPG; mg/dl) concentrations and cardiac sympathetic nervous function was evaluated using the heart-to-mediastinum ratio (H : M) and mean washout rate measured by 123I-meta-iodobenzylguanidine (MIBG) cardiac imaging.

RESULTS

There were significant differences in SSPG (P < 0.01), early (P < 0.05) and delayed (P < 0.05) phases of H : M and washout rate (P < 0.05) between the hypertensive patients and group C. The SSPG concentration was significantly improved after treatment only in group T, from 153.3 to 123.7 mg/dl (P < 0.01). The early and delayed phases of H : M and washout rate also were significantly improved (P < 0.05) (from 2.59 to 2.63, from 2.12 to 2.27 and from 18.1 to 13.7%, respectively) in only group T.The change in SSPG was significantly correlated with the changes in H : M and washout rate (r = -0.639 and 0.577, respectively).

CONCLUSION

Troglitazone had a beneficial effect on cardiac sympathetic nervous function through a decrease in insulin resistance in patients with essential hypertension.

The I1-imidazoline agonist moxonidine decreases sympathetic tone under physical and mental stress

AIMS

Moxonidine is an I1-imidazoline receptor agonist that reduces blood pressure by inhibition of central sympathetic activity. The effects of the drug under physical and mental stress have not been studied in detail.

METHODS

We investigated the effects of 0.4 mg moxonidine orally on sympathetic activity, blood pressure and heart rate in a double-blind, placebo-controlled crossover study in 12 healthy volunteers. The subjects underwent physical exercise test using bicycle ergometry and a mental stress test using an adaptive reaction test device. Potential association of parameters with the GNB3 C825T polymorphism was also assessed.

RESULTS

Under resting conditions, moxonidine decreased plasma noradrenaline (NA: -66.1 +/- 12 pg ml(-1); P < 0.01 vs placebo) and adrenaline (A: -18.8 +/- 6 pg ml(-1); P < 0.05 vs placebo). Physical exercise evoked a significant increase in plasma NA and A (NA: 760 +/- 98 pg ml(-1); A: 97 +/- 9 pg ml(-1); P < 0.001 vs baseline), which was significantly reduced after pretreatment with moxonidine (NA: 627 +/- 68 pg ml(-1); P < 0.05 vs placebo; A: 42.8 +/- 4 pg ml(-1); P < 0.01 vs placebo). Maximal physical exercise capacity was not limited by moxonidine (NS). During the mental stress test, increases in NA (placebo: 146 +/- 24 pg ml(-1), moxonidine: 84 +/- 26 pg ml(-1); P < 0.01 vs placebo) and A (placebo: 22.8 +/- 9 pg ml(-1), moxonidine: 8.0 +/- 8 pg ml(-1); P < 0.01 vs placebo) were significantly reduced after pretreatment with moxonidine. Increases in blood pressure during mental stress were significantly lower after pretreatment with moxonidine (P < 0.05 vs placebo). There was no association of the response to moxonidine with GNB3 genotypes (NS).

CONCLUSIONS

Moxonidine decreases total sympathetic tone under basal conditions as well as during physical exercise and mental stress without limiting absolute exercise capacity. Thus, moxonidine appears suitable for the treatment of patients with high SNS activity and hypertension induced by physical or mental stress. As the drug does not reduce exercise capacity, it may be considered as an alternative to beta-adrenoceptor blockers in selected patients.

Drug treatment of stable angina pectoris in the elderly: defining the place of calcium channel antagonists

Chronic stable angina pectoris (CSAP) resulting from coronary artery disease (CAD) is common in elderly patients, and significantly reduces their quality of life. Myocardial revascularisation procedures in this age group entail significant risks, largely related to comorbidities rather than advanced age itself. Coronary artery anatomy is more likely to be technically unsuitable for revascularisation and angina more resistant to drug treatment. Therefore, elderly patients often take combinations of antianginal drugs. Calcium channel antagonists (CCAs) are effective antianginal drugs first introduced for clinical use in the late 1970's. They reduce myocardial ischaemia by both causing vasodilatation of coronary resistance vessels and reducing cardiac workload (negative inotropic effect). However, adverse effects related to abrupt arterial vasodilatation limited the tolerability of these short acting 'first generation' drugs (nifedipine, verapamil and diltiazem). Furthermore, short acting nifedipine may occasionally increase both the frequency of angina pectoris and mortality in patients with CAD. Since then, long acting formulations of first generation agents and new chemical entities (second and third generation drugs) have been developed. These are well tolerated and effective at attenuating both myocardial ischaemia and the frequency and severity of angina pectoris in most patients with stable CAD. Current guidelines on the drug treatment of CSAP propose that beta-adrenoceptor antagonists (beta-blockers) should be used as first line medication primarily for their prognostic benefits, and that CCAs need only be introduced if beta-blockers are not tolerated, contraindicated or ineffective. Despite this, there is a wealth of evidence from clinical trials that demonstrate equal antianginal efficacy for CCAs and beta-blockers. The presence of chronic heart failure and prior myocardial infarction are clear indications for the use of beta-blockers in preference to CCAs for the treatment of CSAP. However, in patients with both CSAP and hypertension, second and third generation CCAs may offer prognostic benefits of similar magnitude to those provided by beta-blockers. Therefore, antianginal drug therapy must be tailored to the individual needs and comorbidities of each elderly patient.

Short-versus long-term effects of different dihydropyridines on sympathetic and baroreflex function in hypertension

Antihypertensive treatment with dihydropyridines may be accompanied by sympathetic activation. Data on whether this is common to all compounds and similar in the various phases of treatment are not univocal, however. In 28 untreated essential hypertensives (age, 56.4+/-1.8 years; mean+/-SEM) finger blood pressure (BP, Finapres), heart rate (HR, ECG), plasma norepinephrine (NE, high-performance liquid chromatography), and muscle sympathetic nerve traffic (MSNA, microneurography) were measured at rest and during baroreceptor manipulation (vasoactive drugs) in the placebo run-in period and after randomization to double-blind acute and chronic (8 weeks) felodipine (10 mg/d, n=14) or lercanidipine (10 mg/d, n=14). Acute administration of both drugs induced pronounced BP reductions and marked increases in HR, NE, and MSNA. After 8 weeks of treatment, BP reductions were similar to those observed after acute administration, whereas HR, NE, and MSNA responses were markedly attenuated (-7%, -32%, and -14%, respectively; P<0.05). There was a small residual increase in sympathetic activity in the felodipine group, whereas in the lercanidipine group, all adrenergic markers returned to baseline values. Baroreflex control of HR and MSNA was markedly impaired (-42% and -48%, respectively) after acute drug administration, with a recovery and complete resetting during chronic treatment. Thus, the sympathoexcitation induced by 2 different dihydropyridines is largely limited to the acute administration. The 2 drugs have, nevertheless, a different chronic sympathetic effect, indicating that dihydropyridines do not homogeneously affect this function. The acute sympathoexcitation, but not the small between-drugs differential chronic adrenergic effect, is accounted for by baroreflex impairment.

Sympathetic nerve activity in end-stage renal disease

BACKGROUND

Uremia is proposed to increase sympathetic nerve activity (SNA) in hemodialysis patients. The aims of the present study were to determine whether reversal of uremia by successful kidney transplantation (RTX) eliminates the increased SNA and whether signals arising in the diseased kidneys contribute to the increased SNA in renal failure.

METHODS AND RESULTS

We compared muscle sympathetic nerve activity (MSNA) in 13 hemodialysis patients wait-listed for RTX and in renal transplantation patients with excellent graft function treated with cyclosporine (RTX-CSA, n=13), tacrolimus (RTX-FK, n=13), or without calcineurin inhibitors (RTX-Phi, n=6), as well as in healthy volunteers (CON, n=15). In addition to the above patients with present diseased native kidneys, we studied 16 RTX patients who had undergone bilateral nephrectomy (RTX-NE). Data are mean+/-SEM. MSNA was significantly elevated in hemodialysis patients (43+/-4 bursts/min), RTX-CSA (44+/-5 bursts/min), RTX-FK (34+/-3 bursts/min), and RTX-Phi (44+/-5 bursts/min) as compared with CON (21+/-3 bursts/min), despite excellent graft function after RTX. RTX-NE had significantly reduced MSNA (20+/-3 bursts/min) when compared with RTX patients. MSNA did not change significantly with RTX in 4 hemodialysis patients studied before and after RTX (44+/-6 versus 43+/-5 bursts/min, P=NS). In contrast, nephrectomy resulted in reduced MSNA in all 6 RTX patients studied before and after removal of the second native kidney.

CONCLUSIONS

Despite correction of uremia, increased SNA is observed in renal transplant recipients with diseased native kidneys at a level not significantly different from chronic hemodialysis patients. The increased SNA seems to be mediated by signals arising in the native kidneys that are independent of circulating uremia related toxins.

Flecainide augments muscle sympathetic nerve activity in humans

The Cardiac Arrhythmia Suppression Trial has shown that treatment with flecainide is associated with an increased incidence of cardiac death in patients following myocardial infarction. It is believed that there is a complex mechanism involving an interaction between flecainide, sympathetic activation, and acute ischemia that is responsible for the increased risk of sudden death. The purpose of this study was to determine the effects of flecainide on muscle sympathetic nerve activity (MSNA) in humans. We measured MSNA using microneurography and cardiac output using the dye dilution method in 30 healthy individuals. Measurements were made at rest and after the oral administration of flecainide (200mg, n=12) or placebo (n=9), or intravenous administration of propranolol (0.2 mg/kg, n=9). Flecainide significantly increased heart rate and decreased the cardiac index (both p<0.01). Flecainide increased the burst rate from 16.7 +/- 3.5 to 23.3 +/- 4.1 bursts/min and the burst incidence from 26.6 +/- 5.1 to 34.7 +/ -5.6bursts/100 heartbeats (both p<0.01). For all of the hemodynamic parameters except heart rate, the effects of propranolol were similar to those of flecainide. Propranolol also increased the burst rate by 52 +/- 34% and the burst incidence by 106 +/- 39%. These results suggest that flecainide suppresses myocardial contractility and produces reflex-mediated increases in sympathetic nerve firing in humans.

Effects of chronic calcium channel blockade on sympathetic nerve activity in hypertension

The sympathetic nervous system (SNS) is an important regulator of the circulation. Its activity is increased in hypertension and heart failure and adversely affects prognosis. Although certain drugs inhibit SNS, dihydropyridine calcium antagonists may stimulate the system. Phenylalkylamine calcium antagonists such as verapamil have a different pharmacological profile. We therefore tested the hypothesis of whether amlodipine, nifedipine, or verapamil differs in the effects on muscle sympathetic nerve activity (MSA). Forty-three patients (31 men, 12 women) with mild to moderate hypertension were randomly assigned to 1 drug for 8 weeks. Blood pressure, heart rate, and MSA (by microneurography) were measured at baseline and after 8 weeks of treatment. All calcium antagonists led to a similar decrease in blood pressure of 5.0+/-1.5 to 6.4+/-1.4 mm Hg at 8 weeks (P<0.001 versus baseline). There were no significant differences in MSA between groups. With amlodipine, MSA averaged 49+/-3 bursts/min (3 versus baseline); with nifedipine, 48+/-3 bursts/min (2 versus baseline); and with verapamil, 49+/-2 bursts/min (all, P=NS). With verapamil, norepinephrine decreased by 4% but tended to increase by about one third with amlodipine or nifedipine (P=NS). Thus, in hypertension slow release forms of verapamil, nifedipine, and amlodipine exert comparable antihypertensive effects and do not change MSA, although there was a trend toward decreased MSA and plasma norepinephrine with verapamil.

Effects of losartan and its combination with quinapril on the cardiac sympathetic nervous system and neurohormonal status in essential hypertension

OBJECTIVE

Sympathetic nervous and renin-angiotensin systems play important roles in essential hypertension. This study was aimed at assessing the effects of losartan or its combination with quinapril on the cardiac nervous system and neurohormonal status in essential hypertension.

DESIGN AND METHODS

Randomized, comparative study of 105 patients with mild essential hypertension, carried out at Shizuoka General Hospital. In phase 1, 40 hypertensives were allocated randomly into the losartan (50 mg) group or the quinapril (10 mg) group. In phase 2, 65 hypertensives, after 3 months 10 mg quinapril monotherapy, were allocated randomly into groups with 50 mg losartan (n = 32) or 5 mg amlodipine (n = 33) added to quinapril, and were treated for a further 3 months. All patients underwent [(123)I]metaiodobenzylguanidine (MIBG) imaging and neurohormonal measurements before and 3 months after treatment.

RESULTS

Both monotherapies significantly increased renin activity, while losartan monotherapy also increased angiotensin II (AII) concentration. In both the losartan and quinapril groups, the washout rate was significantly decreased (18.1 +/- 11.4 versus 13.9 +/- 11.0%, P < 0.0002 and 13.3 +/- 9.3 versus 12.3 +/- 9.1%, P < 00001, respectively) without changes in the heart to mediastinum ratio (H/M ratio). Both combined therapies lowered blood pressure to similar levels. A combination therapy with losartan and quinapril significantly increased the H/M ratio (1.93 +/- 0.29 and 2.02 +/- 0.29, P < 0.01) and decreased the washout rate (17.6 +/- 11.0 and 15.3 +/- 9.2%, P < 0.02) without affecting AII concentration, whereas a combination therapy with amlodipine and quinapril therapy did not affect the scintigraphic parameters with an increase in the AII concentration.

CONCLUSIONS

With a usual antihypertensive dose, both losartan and quinapril had a little suppressive effect on the cardiac sympathetic activity in essential hypertension. In contrast, the combination therapy with losartan and quinapril, which results in a higher degree of inhibition of the renin-angiotensin system, could suppress the cardiac sympathetic activity effectively.

Antihypertensive drugs and the sympathetic nervous system

The sympathetic nervous system (SNS) plays an important role in the regulation of blood pressure homeostasis and cardiac function. Furthermore, the increased SNS activity is a predictor of mortality in patients with hypertension, coronary artery disease and congestive heart failure. Experimental data and a few clinical trials suggest that there are important interactions between the main pressor systems, i.e. the SNS, the renin-angiotensin system and the vascular endothelium with the strongest vasoconstrictor, endothelin. The main methods for the assessment of SNS activity are described. Cardiovascular drugs of different classes interfere differently with the SNS and the other pressor systems. Pure vasodilators including nitrates, alpha-blockers and dihydropyridine (DHP)-calcium channel blockers increase SNS activity. Finally, central sympatholytics and possibly phenylalkylamine-type calcium channel blockers reduce SNS activity. The effects of angiotensin-II receptor antagonists on SNS activity in humans is not clear; experimental data are discussed in this review. There are important interactions between the pressor systems under experimental conditions. Recent studies in humans suggest that an activation of the SNS with pure vasodilators in parallel increases plasma endothelin. It can be assumed that, in cardiovascular diseases with already enhanced SNS activity, drugs which do not increase SNS activity or even lower it are preferable. Whether this reflects in lower mortality needs to be investigated in intervention trials.

Comparative effects of mibefradil and nifedipine gastrointestinal transport system on autonomic function in patients with mild to moderate essential hypertension

BACKGROUND

L-type dihydropyridine calcium channel blockers (CCBs) have been implicated in increased cardiovascular events in patients with hypertension, perhaps due to adverse effects on autonomic nervous system (ANS) function. Blockade of T-type calcium channels may limit ANS dysfunction by inhibition of T channel-mediated neuroendocrine effects.

OBJECTIVE AND DESIGN

This double-blind, parallel group study compared the effect of nifedipine gastrointestinal transport system (GITS) (L-type CCB) versus mibefradil (T-type CCB) on ANS function in patients with mild-moderate essential hypertension.

METHODS

Sixteen patients (10 male, 6 female; age 57.2 +/- 2.3 years), diastolic blood pressure (DBP) < 95 mmHg were randomized to nifedipine 30 mg daily or mibefradil 50 mg daily (2 weeks), then nifedipine 60 mg daily or mibefradil 100 mg daily (4 weeks). Sympathetic nervous system activity (SNSA) was assessed using norepinephrine kinetics. Parasympathetic nervous system activity (PSNA) was assessed from 24 h Holter recordings of heart rate variability (HRV). Non-invasive baroreflex sensitivity (BRS) provided integrated assessment of ANS.

RESULTS

Patient groups were well matched at baseline. Achieved DBP was lower in patients treated with mibefradil compared with nifedipine, (83.4 +/- 1.7 versus 95.25 +/- 3.3 mmHg). There were no significant differences in SNSA and BRS between groups, however the root mean square of successive differences and high frequency power (HFP) were increased in mibefradil compared with nifedipine-treated patients [(+ 1.07 +/- 1.6 versus -3.36 +/- 1.2 ms, P < 0.05) and (+ 0.28 +/- 0.1 versus -0.23 +/- 0.1 ms2, P < 0.01), respectively]. Furthermore, Ln HFP/Ln total power was increased from week 0 to week 6 in the mibefradil-treated group, (0.71 +/- 0.02 versus 0.74 +/- 0.03, P = 0.046).

CONCLUSION

No differences existed between effect of L- and T-type CCBs on SNSA and BRS. However, T-type CCBs increased PSNA, independent of achieved changes in heart rate.

Baroreceptor dysfunction induced by nitric oxide synthase inhibition in humans

OBJECTIVES

We sought to investigate baroreceptor regulation of sympathetic nerve activity and hemodynamics after inhibition of nitric oxide (NO) synthesis.

BACKGROUND

Both the sympathetic nervous system and endothelium-derived substances play essential roles in cardiovascular homeostasis and diseases. Little is known about their interactions.

METHODS

In healthy volunteers, we recorded muscle sympathetic nerve activity (MSA) with microneurography and central hemodynamics measured at different levels of central venous pressure induced by lower body negative pressure.

RESULTS

After administration of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA, 1 mg/kg/min), systolic blood pressure increased by 24 mm Hg (p = 0.01) and diastolic blood pressure by 12 mm Hg (p = 0.009), while stroke volume index (measured by thermodilution) fell from 53 to 38 mL/min/m2 (p < 0.002). Administration of L-NMMA prevented the compensatory increase of heart rate, but not MSA, to orthostatic stress. The altered response of heart rate was not due to higher blood pressure, because heart rate responses were not altered during infusion of the alpha-1-adrenoceptor agonist phenylephrine (titrated to an equal increase of systolic blood pressure). In the presence of equal systolic blood pressure and central venous pressure, we found no difference in MSA during phenylephrine and L-NMMA infusion.

CONCLUSIONS

This study demonstrates a highly specific alteration of baroreceptor regulation of heart rate but not muscle sympathetic activity after inhibition of NO synthesis in healthy volunteers. This suggests an important role of NO in reflex-mediated heart rate regulation in humans.

The Beauty and the Beast: Aspects of the Autonomic Nervous System

Sympathetic nerve activity is altered and is a prognostic factor for many cardiovascular diseases such as hypertension, coronary syndromes, and congestive heart failure. Therefore, the selection of vasoactive drugs for the treatment of these diseases should also take into consideration their effects on the sympathetic nervous system.

Cardiovascular effects of melatonin in hypertensive patients well controlled by nifedipine: a 24-hour study

AIMS

As melatonin has been found to play a role in the mechanisms of cardiovascular regulation, we designed the present study to evaluate whether the evening ingestion of the pineal hormone might interfere with the antihypertensive therapy in hypertensive patients well-controlled by nifedipine monotherapy.

METHODS

Forty-seven mild to moderate essential hypertensive outpatients taking nifedipine GITS 30 or 60 mg monotherapy at 08.30 h for at least 3 months, were given placebo or melatonin 5 mg at 22.30 h for 4 weeks according to a double-blind cross-over study. At the end of each treatment period patients underwent a 24 h noninvasive ambulatory blood pressure monitoring (ABPM) during usual working days; sleeping period was scheduled to last from 23.00 to 07.00 h.

RESULTS

The evening administration of melatonin induced an increase of blood pressure and heart rate throughout the 24 h period (DeltaSBP = + 6.5 mmHg, P < 0.001; DeltaDBP = + 4.9 mmHg, P < 0.01; DeltaHR = + 3.9 beats min-1, P < 0.01). The DBP as well as the HR increase were particularly evident during the morning and the afternoon hours.

CONCLUSIONS

We hypothesize that competition between melatonin and nifedipine, is able to impair the antihypertensive efficacy of the calcium channel blocker. This suggests caution in uncontrolled use of melatonin in hypertensive patients. As the pineal hormone might interfere with calcium channel blocker therapy, it cannot be considered simply a dietary supplement.

Sympathoinhibition by central and peripheral infusion of nifedipine in spontaneously hypertensive rats

The present study assessed whether central mechanisms may contribute to the hypotensive effect of the calcium channel blocker nifedipine. In conscious, spontaneously hypertensive rats (SHR) on a high-salt diet, hemodynamic (mean arterial pressure [MAP] and heart rate) and sympathetic (renal sympathetic nerve activity) responses to low, central, intracerebroventricular infusion rates (25 microg. kg(-1). h(-1) for 2 hours) and peripheral intravenous rates (50 microg. kg(-1). h(-1) for 3 hours and then 100 microg. kg(-1). h(-1) for 2 hours) of nifedipine were evaluated. The distribution of nifedipine in the blood and tissues was assessed at the end of the infusions. Nifedipine significantly inhibited renal sympathetic nerve activity and lowered MAP in SHR beginning 30 minutes after the start of the intracerebroventricular infusion. The decrease of MAP by intravenous infusion began at 60 minutes and was more profound with 100 microg. kg(-1). h(-1). Inhibition of sympathetic activity preceded and then paralleled the decrease in blood pressure; it occurred earlier with central (15 to 30 minutes) than with peripheral (30 to 60 minutes) infusion. Intravenous infusion resulted in concentrations of nifedipine in brain structures (brain stem, midbrain, and cortex) that were 30% to 40% of those in the heart, kidneys, and liver. From the hemodynamic and sympathetic responses and the distribution of nifedipine into the central nervous system, we conclude that the peripheral infusion of nifedipine at relatively low rates may evoke a hypotensive response in SHR, not only via peripheral mechanisms, but also through central mechanisms, which will lead to an inhibition of sympathetic outflow and, therefore, a lowering of blood pressure.

Nocturnal continuous positive airway pressure decreases daytime sympathetic traffic in obstructive sleep apnea

BACKGROUND

Patients with obstructive sleep apnea (OSA) have high levels of muscle sympathetic nerve activity (MSNA). We tested the hypothesis that long-term continuous positive airway pressure (CPAP) treatment will decrease MSNA in OSA patients.

METHODS AND RESULTS

We measured blood pressure, heart rate, and MSNA in 11 normotensive, otherwise healthy patients with OSA who were treated with CPAP. The measurements were obtained at baseline and after 1 month, 6 months, and 1 year of CPAP treatment. These measurements were compared with those recorded in 9 otherwise healthy OSA patients who were not treated with CPAP for 1 year. In both untreated and treated patients, blood pressure and heart rate did not change over time. MSNA was similar during repeated measurements in the untreated group. By contrast, MSNA decreased significantly over time in patients treated with CPAP. This decrease was evident after both 6 months and 1 year of CPAP treatment (P=0.02 for both).

CONCLUSIONS

CPAP treatment decreases muscle sympathetic traffic in patients with OSA. This effect of CPAP is evident only after an extended duration of therapy.

Effects of amlodipine and cilnidipine on cardiac sympathetic nervous system and neurohormonal status in essential hypertension

N-Type calcium channel antagonists may suppress sympathetic activity. The purpose of this study was to assess the effects of amlodipine and cilnidipine on the cardiac sympathetic nervous system and the neurohormonal status of essential hypertension. 123I-metaiodobenzylguanidine (MIBG) cardiac imaging was performed and blood samples were taken to determine plasma renin activity and plasma norepinephrine concentration before and 3 months after drug administration in 47 patients with mild essential hypertension. Twenty-four of the patients were treated with 5 to 10 mg/d of amlodipine; the other 23 were treated with 10 to 20 mg/d of cilnidipine. For comparison, 12 normotensive subjects were also studied. No significant differences were found in the basal characteristics between the 2 hypertensive groups. In both hypertensive groups, both the systolic and diastolic blood pressures were significantly reduced to similar levels 3 months after drug treatment. Before the drug treatment, the 2 hypertensive groups had a significantly higher washout rate and lower heart-to-mediastinum (H/M) ratio compared with the normotensive subjects. The H/M ratio significantly increased (P<0.05) in combination with a decreased washout rate (P<0.02) after drug treatment in the cilnidipine group. In the amlodipine group, a significant decrease in washout rate (P<0. 04) was noted, without an increase in the H/M ratio. However, no significant changes were found in plasma renin activity and plasma norepinephrine concentration in either group. Thus, in patients with essential hypertension, cilnidipine suppressed cardiac sympathetic overactivity and amlodipine had a little suppressive effect. Cilnidipine may provide a new strategy for treatment of cardiovascular diseases with sympathetic overactivity.

Endothelin in cardiovascular control: the role of endothelin antagonists

Endothelin (ET) is a potent vasoconstrictor associated with various cardiovascular diseases. ET mediates its effects through ET receptors on vascular smooth muscle cells as well as on the vascular endothelium. Furthermore, a neurotransmitter role for ET has been suggested on the basis of experimental and human in vivo studies. ET antagonists are potent tools for studying the effects of ET and its receptors. They have been widely used in vitro and in experimental models of cardiovascular disease, where ET levels are elevated and reactivity to ET is altered. Promising clinical trials in hypertension, coronary artery disease, and congestive heart failure are discussed in this review. Different forms of renal failure are associated with markedly increased ET levels, and ET antagonists experimentally improve renal function in these models. Extrapolating from experimental and first clinical experience, ET antagonists could be useful in the treatment of hypertension, coronary artery disease, congestive heart failure, and renal failure, especially in combination with other drugs, ie, angiotensin converting enzyme inhibitors. The inhibition of ET-induced stimulation of nociception allows for speculation that ET antagonists might even have analgesic properties.

I1-imidazoline agonist moxonidine decreases sympathetic nerve activity and blood pressure in hypertensives

Moxonidine is an I1-imidazoline receptor agonist that reduces blood pressure in hypertensives. Experimental data suggest that moxonidine inhibits central sympathetic activity. However, whether such a mechanism is involved in vivo in humans is still unclear. We investigated the effects of 0.4 mg moxonidine orally on muscle sympathetic nerve activity and heart rate in an open study in 8 healthy volunteers. Furthermore, we studied the effects of 0.4 mg moxonidine on muscle sympathetic nerve activity, heart rate, blood pressure, 24-hour blood pressure profile, and hormone plasma levels in 25 untreated hypertensives in a double-blind, placebo-controlled study. Moxonidine decreased muscle sympathetic nerve activity in both healthy volunteers (P<0.05 versus baseline) and hypertensives (P<0.02 versus placebo). Plasma norepinephrine also decreased (P<0. 01), whereas plasma epinephrine and renin levels did not change (P=NS). Furthermore, moxonidine decreased systolic (P<0.0001) and diastolic (P<0.001) blood pressure. Heart rate decreased after moxonidine in healthy subjects (P<0.05); in hypertensives, heart rate decreased during the night hours (P<0.05) but not during daytime (P=NS). Plasma levels of LDL, HDL, and total cholesterol were not influenced by the drug (P=NS). Moxonidine decreases systolic and diastolic blood pressure by inhibiting central nervous sympathetic activity. This makes this new drug suitable for the treatment of human hypertension and possibly for other cardiovascular diseases with increased sympathetic nerve activity, ie, ischemic heart disease and heart failure.