Comparison of the effects of amlodipine and verapamil on autonomic activity in hypertensive patients

Rationale and design of the EMPYREAN study

Aims

A sodium glucose cotransporter 2 (SGLT2) inhibitor was recently found to reduce heart failure hospitalization in the EMPA‐REG OUTCOME trial. We have hypothesized that autonomic nerve activity may be modulated by SGLT2 inhibition. The current study aims to investigate the impact of empagliflozin on sympathetic and parasympathetic nerve activity in patients with type 2 diabetes mellitus.

Methods and results

This ongoing study is a prospective, randomized, open‐label, multicentre investigation of 134 patients with type 2 diabetes mellitus. The patients are randomly allocated to receive either empagliflozin or sitagliptin with the treatment goal of the Japan Diabetes Society guidelines. Ambulatory electrocardiographic monitoring is performed at the baseline and at 12 and 24 weeks of treatment. Analyses of heart rate variability are conducted using the MemCalc method, which is a combination of the maximum entropy method for spectral analysis and the non‐linear least squares method for square analysis. The primary endpoint is the change in the low‐frequency (0.04–0.15 Hz)/high‐frequency (0.15–0.4 Hz) ratio from baseline to 24 weeks.

Conclusions

This investigation on the effect of EMPagliflozin on cardiac sYmpathetic and parasympathetic neRve activity in JapanEse pAtieNts with type 2 diabetes (EMPYREAN study) offers an important opportunity to understand the impact of SGLT2 inhibition on autonomic nerve activity in patients with type 2 diabetes.

Autonomic dysfunction in mild cognitive impairment: evidence from power spectral analysis of heart rate variability in a cross-sectional case-control study

BACKGROUND

Mild cognitive impairment (MCI) is set to become a major health problem with the exponential ageing of the world's population. The association between MCI and autonomic dysfunction, supported by indirect evidence and rich with clinical implications in terms of progression to dementia and increased risk of mortality and falls, has never been specifically demonstrated.

AIM

To conduct a comprehensive assessment of autonomic function in subjects with MCI by means of power spectral analysis (PSA) of heart rate variability (HRV) at rest and during provocative manoeuvres.

METHODS

This cross-sectional study involved 80 older outpatients (aged ≥ 65) consecutively referred to a geriatric unit and diagnosed with MCI or normal cognition (controls) based on neuropsychological testing. PSA was performed on 5-minute electrocardiographic recordings under three conditions--supine rest with free breathing (baseline), supine rest with paced breathing at 12 breaths/minute (parasympathetic stimulation), and active standing (orthosympathetic stimulation)--with particular focus on the changes from baseline to stimulation of indices of sympathovagal balance: normalized low frequency (LFn) and high frequency (HFn) powers and the LF/HF ratio. Blood pressure (BP) was measured at baseline and during standing. Given its exploratory nature in a clinical population the study included subjects on medications with a potential to affect HRV.

RESULTS

There were no significant differences in HRV indices between the two groups at baseline. MCI subjects exhibited smaller physiological changes in all three HRV indices during active standing, consistently with a dysfunction of the orthosympathetic system. Systolic BP after 10 minutes of standing was lower in MCI subjects, suggesting dysautonomia-related orthostatic BP dysregulation.

CONCLUSIONS

Our study is novel in providing evidence of autonomic dysfunction in MCI. This is associated with orthostatic BP dysregulation and the ongoing follow-up of the study population will determine its prognostic relevance as a predictor of adverse health outcomes.

Long-acting dihydropyridine calcium-channel blockers and sympathetic nervous system activity in hypertension: a literature review comparing amlodipine and nifedipine GITS

Calcium-channel blockers (CCBs) constitute a diverse group of compounds but are often referred to as a single homogeneous class of drug and the clinical responses indiscriminately summarized. Even within the dihydropyridine subgroup, there are significant differences in formulations, pharmacokinetics, durations of action and their effects on blood pressure, heart rate, end organs and the sympathetic nervous system. Amlodipine and nifedipine in the gastrointestinal therapeutic system (GITS) formulation are the most studied of the once-daily CCBs. Amlodipine has an inherently long pharmacokinetic half-life, whereas, in contrast, nifedipine has an inherently short half-life but in the GITS formulation the sophisticated delivery system allows for once-daily dosing. This article is derived from a systematic review of the published literature in hypertensive patients. The following search terms in three main databases (MEDLINE, Embase, Science Citation Index) from 1990 to 2011 were utilized: amlodipine, nifedipine, sympathetic nervous system, sympathetic response, sympathetic nerve activity, noradrenaline, norepinephrine and heart rate. More than 1500 articles were then screened to derive the relevant analysis. As markers of sympathetic nervous system activation, studies of plasma norepinephrine concentrations, power spectral analysis, muscle sympathetic nerve activity and norepinephrine spillover were reviewed. Overall, each drug lowered blood pressure in hypertensive patients in association with only small changes in heart rate (i.e. <1 beat/min). Plasma norepinephrine concentrations, as the most widely reported marker of sympathetic nervous system activity, showed greater increases in patients treated with amlodipine than with nifedipine GITS. The evidence indicates that both these once-daily dihydropyridine CCBs lower blood pressure effectively with minimal effects on heart rate. There are small differences between the drugs in the extent to which each activates the sympathetic nervous system with an overall non-significant trend in favour of nifedipine GITS.

The significance of amlodipine on autonomic nervous system adjustment (ANSA method): a new approach in the treatment of hypertension

INTRODUCTION

Cardiovascular autonomic modulation is altered in patients with essential hypertension.

OBJECTIVE

To evaluate acute and long-term effects of amlodipine on cardiovascular autonomic function and haemodynamic status in patients with mild essential hypertension.

METHODS

Ninety patients (43 male, mean age 52.12 +/- 10.7) years with mild hypertension were tested before, 30 minutes after the first 5 mg oral dose of amlodipine and three weeks after monotherapy with amlodipine. A comprehensive study protocol was done including finger blood pressure variability (BPV) and heart rate variability (HRV) beat-to-beat analysis with impedance cardiography, ECG with software short-term HRV and nonlinear analysis, 24-hour Holter ECG monitoring with QT and HRV analysis, 24-hour blood pressure (BP) monitoring with systolic and diastolic BPV analysis, cardiovascular autonomic reflex tests, cold pressure test, mental stress test. The patients were also divided into sympathetic and parasympathetic groups, depending on predominance in short time spectral analysis of sympathovagal balance according to low frequency and high frequency values.

RESULTS

We confirmed a significant systolic and diastolic BP reduction, and a reduction of pulse pressure during day, night and early morning hours. The reduction of supraventricular and ventricular ectopic beats during the night was also achieved with therapy, but without statistical significance. The increment of sympathetic activity in early phase of amlodipine therapy was without statistical significance and persistence of sympathetic predominance after a few weeks of therapy detected based on the results of short-term spectral HRV analysis. All time domain parameters of long-term HRV analysis were decreased and low frequency amongst spectral parameters. Amlodipne reduced baroreflex sensitivity after three weeks of therapy, but increased it immediately after the administration of the first dose.

CONCLUSION

The results of the study showed that amlodipine affected autonomic modulation as a shift to sympathetic hyperactivity, but without statistical significance. In the selected group of patients with vagal predominance in sympathovagal balance, amlodipine increased sympathetic and decreases vagal activity. Therefore we conclude that amlodipine mostly exerts impact on autonomic function modulation in patients with vagal predominance in resting state.

Is neurogenic hypertension related to vascular inflammation of the brainstem?

Essential hypertension is idiopathic although it is accepted as a complex polygenic trait with underlying genetic components, which remain unknown. Our supposition is that hypertension involves activation of the sympathetic nervous system. One pivotal region controlling arterial pressure set point is nucleus tractus solitarii (NTS). We recently identified that pro-inflammatory molecules, such as junctional adhesion molecule-1 (JAM-1), were over expressed in endothelial cells of the microvasculature supplying the NTS in an animal model of human hypertension (the spontaneously hypertensive rat) compared to normotensive Wistar-Kyoto rats (WKY). Over expression of JAM-1 in NTS of WKY rats was pro-hypertensive and induced leukocyte adherence to the microvasculature. Since leukocyte adhesion causes cytokine release, we found expression of monocyte chemoattractant protein-1 (MCP-1) was higher in the NTS of SHR while inter-leukin-6 (IL-6) was lower compared to the WKY rat. Inflammation of the brainstem microvasculature may increase vascular resistance within the brainstem. High brainstem vascular resistance and its inflammation may release pathological paracrine signaling molecules affecting central neural cardiovascular activity conducive to neurogenic hypertension.

Evaluation of autonomic activity in patients with subclinical hypothyroidism

It has been shown that impaired cardiac autonomic activity is closely related with lethal arhythmias. Heart rate variability (HRV), analysis of beat-to-beat variations, is an important and widely used non-invasive method to assess autonomic function. Impaired cardiac autonomic activity and altered sympathovagal balance were previously documented in patients with hypothyroidism. However, the effect of subclinical hypothyroidism (SH) on autonomic function has not been studied yet. We aimed to investigate the effect of SH on sympathovagal balance using the HRV method. The study included 31 patients with SH and 28 healthy volunteer controls. Patients with cardiac, metabolic, neurological disease or any other systemic disease that could affect autonomic activity were excluded from the study. HRV time domain and frequency domain parameters were determined over a period of 24 h. All time and frequency domain measures of HRV in patients with SH were not significantly different compared to those of healthy control group (p > 0.05). Additionally, we compared SH subgroups (TSH level > or =10 and TSH level <10 mU/l) with each other and the controls. A statistically significant difference was observed only in time domain parameters of SD of normal-to-normal intervals (SDNN) and SD of all 5-min mean normal NN intervals (SDANN) between subgroup with TSH level > or =10 and controls (p < 0.05, p < 0.05, respectively). In correlation analysis with TSH, there was positive relationship between TSH and the root mean square of successive differences between adjacent R-R intervals (rMSSD). These findings indicate that SH may affect cardiac autonomic activity in correlation with TSH levels.