Autonomic cardiovascular control and diastolic dysfunction in hypertensive subjects

Effects of baroreflex activation therapy on cardiac function and morphology

AIMS

Arterial hypertension (aHTN) plays a fundamental role in the pathogenesis and prognosis of heart failure with preserved ejection fraction (HFpEF). The risk of heart failure increases with therapy-resistant arterial hypertension (trHTN), defined as inadequate blood pressure (BP) control ≥140/90 mmHg despite taking ≥3 antihypertensive medications including a diuretic. This study investigates the effects of the BP lowering baroreflex activation therapy (BAT) on cardiac function and morphology in patients with trHTN with and without HFpEF.

METHODS

Sixty-four consecutive patients who had been diagnosed with trHTN and received BAT implantation between 2012 and 2016 were prospectively observed. Office BP, electrocardiographic and echocardiographic data were collected before and after BAT implantation.

RESULTS

Mean patients' age was 59.1 years, 46.9% were male, and mean body mass index (BMI) was 33.2 kg/m2. The prevalence of diabetes mellitus was 38.8%, atrial fibrillation was 12.2%, and chronic kidney disease (CKD) stage ≥3 was 40.8%. Twenty-eight patients had trHTN with HFpEF, and 21 patients had trHTN without HFpEF. Patients with HFpEF were significantly older (64.7 vs. 51.6 years, P < 0.0001), had a lower BMI (30.0 vs. 37.2 kg/m2, P < 0.0001), and suffered more often from CKD-stage ≥3 (64 vs. 20%, P = 0.0032). After BAT implantation, mean office BP dropped in patients with and without HFpEF (from 169 ± 5/86 ± 4 to 143 ± 4/77 ± 3 mmHg [P = 0.0019 for systolic BP and 0.0403 for diastolic BP] and from 170 ± 5/95 ± 4 to 149 ± 6/88 ± 5 mmHg [P = 0.0019 for systolic BP and 0.0763 for diastolic BP]), while a significant reduction of the intake of calcium-antagonists, α2-agonists and direct vasodilators, as well as a decrease in average dosage of ACE-inhibitors and α2-agonists could be seen. Within the study population, a decrease in heart rate from 74 ± 2 to 67 ± 2 min-1 (P = 0.0062) and lengthening of QRS-time from 96 ± 3 to 106 ± 4 ms (P = 0.0027) and QTc-duration from 422 ± 5 to 432 ± 5 ms (P = 0.0184) were detectable. The PQ duration was virtually unchanged. In patients without HF, no significant changes of echocardiographic parameters could be seen. In patients with HFpEF, posterior wall diameter decreased significantly from 14.0 ± 0.5 to 12.7 ± 0.3 mm (P = 0.0125), left ventricular mass (LVM) declined from 278.1 ± 15.8 to 243.9 ± 13.4 g (P = 0.0203), and e' lateral increased from 8.2 ± 0.4 to 9.0 ± 0.4 cm/s (P = 0.0471).

CONCLUSIONS

BAT reduced systolic and diastolic BP and was associated with morphological and functional improvement of HFpEF.

Abnormal neurovascular control during central and peripheral chemoreceptors stimulation in heart failure patients with preserved ejection fraction

PURPOSE

Central and peripheral chemoreceptors are hypersensitized in patients with heart failure with reduced ejection fraction. Whether this autonomic alteration occurs in patients with heart failure with preserved ejection fraction (HFpEF) remains little known. We test the hypothesis that the central and peripheral chemoreflex control of muscle sympathetic nerve activity (MSNA) is altered in HFpEF.

METHODS

Patients aged 55-80 years with symptoms of heart failure, body mass index ≤ 35 kg/m2, left ventricular ejection fraction > 50%, left atrial volume index > 34 mL/m2, left ventricular early diastolic filling velocity and early diastolic tissue velocity of mitral annulus ratio (E/e' index) ≥ 13, and BNP levels > 35 pg/mL were included in the study (HFpEF, n = 9). Patients without heart failure with preserved ejection fraction (non-HFpEF, n = 9), aged-paired, were also included in the study. Peripheral chemoreceptors stimulation (10% O2 and 90% N2, with CO2 titrated) and central chemoreceptors stimulation (7% CO2 and 93% O2) were conducted for 3 min. MSNA was evaluated by microneurography technique, and forearm blood flow (FBF) by venous occlusion plethysmography.

RESULTS

During hypoxia, MSNA responses were greater (p < 0.001) and FBF responses were lower in patients with HFpEF (p = 0.006). Likewise, MSNA responses during hypercapnia were higher (p < 0.001) and forearm vascular conductance (FVC) levels were lower (p = 0.030) in patients with HFpEF.

CONCLUSIONS

Peripheral and central chemoreflex controls of MSNA are hypersensitized in patients with HFpEF, which seems to contribute to the increase in MSNA in these patients. In addition, peripheral and central chemoreceptors stimulation in patients with HFpEF causes muscle vasoconstriction.

Cardiometabolic-based chronic disease: adiposity and dysglycemia drivers of heart failure

Heart failure (HF) is a complex clinical syndrome, associated with high rates of mortality, hospitalization, and impairment of quality of life. Obesity and type 2 diabetes are major cardiometabolic drivers, represented as distinct stages of adiposity- and dysglycemia-based chronic disease (ABCD, DBCD), respectively, and leading to cardiometabolic-based chronic disease (CMBCD). This review focuses on one aspect of the CMBCD model: how ABCD and DBCD influence genesis and progression of HF phenotypes. Specifically, the relationships of ABCD and DBCD stages with structural and functional heart disease, HF risk, and outcomes in overt HF are detailed. Also, evidence-based lifestyle, pharmacological, and procedural interventions that promote or reverse cardiac remodeling and outcomes in individuals at risk or with HF are discussed. In summary, driver-based chronic disease models for individuals at risk or with HF can expose prevention targets for more comprehensive interventions to improve clinical outcomes. Future randomized trials that investigate structured lifestyle, pharmacological, and procedural therapies specifically tailored for the CMBCD model are needed to develop personalized care plans to decrease HF susceptibility and improve outcomes.

Associations between Heart Rate Variability Parameters and Hemodynamic Profiles in Patients with Primary Arterial Hypertension, Including Antihypertensive Treatment Effects

Background: Autonomic nervous system (ANS) dysfunction is an important factor in the development and progression of arterial hypertension (AH) and may produce adverse hemodynamic sequelae. ANS function can be evaluated by analyzing heart rate variability (HRV). The purpose of this study was to assess the possible correlation between HRV and the hemodynamic profile of AH patients, including antihypertensive treatment effects after 12 months. Methods: The study was conducted on 144 patients with uncomplicated AH. The hemodynamic profile was assessed via echocardiography and impedance cardiography (ICG). The analyzed HRV parameters included SDNN, rMSSD, pNN50, low frequency (LF, 0.05–0.15 Hz), high frequency (HF, 0.15–0.4 Hz), total power (TP, the variance of all NN intervals), and the day, night, and 24-h low-to-high frequency ratios (LF/HF). Results: Analysis showed various correlations of HRV parameters both with arterial blood pressure and with the hemodynamic profile assessed via echocardiography and ICG. The HRV parameters of increased ANS activity showed a correlation with improved left ventricle function (LV) and lower LV afterload. Conclusions: Effective antihypertensive treatment demonstrated beneficial effects on both the ANS balance and the hemodynamic profile.

The role of arterial hypertension in development heart failure with preserved ejection fraction: just a risk factor or something more?

Heart failure with preserved ejection fraction (HFpEF) is an entity that still raises many questions. The agreement about definition, pathophysiology, and therapeutic approach is still missing. Arterial hypertension is present in majority of patients with HFpEF, and it is still not clear if it represent a risk factor or "sine qua non" condition for HFpEF development. The underlying mechanisms of hypertension and HFpEF involve the same biohumoral systems: renin-angiotensin-aldosterone, sympathetic nervous system, and oxidative stress. However, not all hypertensive patients have HFpEF. The predisposition of some hypertensive patients to develop HFpEF needs to be resolved. Large randomized controlled trials did not prove the usefulness of renin-angiotensin-aldosterone inhibitors, diuretics, calcium channel blockers, and beta-blockers in HFpEF patients. The majority of studies did not succeed to demonstrate the reduction of cardiovascular and all-cause mortality in HFpEF individuals. One of the major limitations in these investigations was the inconsistency of HFpEF definition, which mainly refers to left ventricular ejection fraction (LVEF) cut-off that ranged from 40 to 50% in different studies. This review article provides the available data about pathophysiology and mechanisms that connect hypertension and HFpEF, investigations and therapy used in both conditions.

A systematic review concerning the relation between the sympathetic nervous system and heart failure with preserved left ventricular ejection fraction

BACKGROUND

Heart failure with preserved left ventricular ejection fraction (HFPEF) affects about half of all patients diagnosed with heart failure. The pathophysiological aspect of this complex disease state has been extensively explored, yet it is still not fully understood. Since the sympathetic nervous system is related to the development of systolic HF, we hypothesized that an increased sympathetic nerve activation (SNA) is also related to the development of HFPEF. This review summarizes the available literature regarding the relation between HFPEF and SNA.

METHODS AND RESULTS

Electronic databases and reference lists through April 2014 were searched resulting in 7722 unique articles. Three authors independently evaluated citation titles and abstracts, resulting in 77 articles reporting about the role of the sympathetic nervous system and HFPEF. Of these 77 articles, 15 were included for critical appraisal: 6 animal and 9 human studies. Based on the critical appraisal, we selected 9 articles (3 animal, 6 human) for further analysis. In all the animal studies, isoproterenol was administered to mimic an increased sympathetic activity. In human studies, different modalities for assessment of sympathetic activity were used. The studies selected for further evaluation reported a clear relation between HFPEF and SNA.

CONCLUSION

Current literature confirms a relation between increased SNA and HFPEF. However, current literature is not able to distinguish whether enhanced SNA results in HFPEF, or HFPEF results in enhanced SNA. The most likely setting is a vicious circle in which HFPEF and SNA sustain each other.

The autonomic nervous system and heart failure

The pathophysiology of heart failure (HF) is characterized by hemodynamic abnormalities that result in neurohormonal activation and autonomic imbalance with increase in sympathetic activity and withdrawal of vagal activity. Alterations in receptor activation from this autonomic imbalance may have profound effects on cardiac function and structure. Inhibition of the sympathetic drive to the heart through β-receptor blockade has become a standard component of therapy for HF with a dilated left ventricle because of its effectiveness in inhibiting the ventricular structural remodeling process and in prolonging life. Several devices for selective modulation of sympathetic and vagal activity have recently been developed in an attempt to alter the natural history of HF. The optimal counteraction of the excessive sympathetic activity is still unclear. A profound decrease in adrenergic support with excessive blockade of the sympathetic nervous system may result in adverse outcomes in clinical HF. In this review, we analyze the data supporting a contributory role of the autonomic functional alterations on the course of HF, the techniques used to assess autonomic nervous system activity, the evidence for clinical effectiveness of pharmacological and device interventions, and the potential future role of autonomic nervous system modifiers in the management of this syndrome.

Increased QT variability in young asymptomatic patients with beta-thalassemia major

BACKGROUND

Despite recent progress in iron chelation therapy, sudden cardiac death due to malignant ventricular arrhythmias remains a vexing, clinical problem in patients with beta-thalassemia major (TM). In this study we assessed whether the major indices of QT variability, emerging tools for risk stratification of sudden cardiac death, differ in young asymptomatic patients with TM and healthy persons.

METHODS

Thirty patients with TM and 30 healthy control subjects underwent a 5-min electrocardiography recording to calculate the following variables: QT variance (QT(v)), QT(v) normalized for mean QT (QTVN) and QT variability index (QTVI). All subjects also underwent a two-dimensional and Doppler echocardiography study and magnetic resonance imaging (MRI) to determine cardiac and hepatic T2* values.

RESULTS

No differences were observed in clinical and conventional echo-Doppler findings in healthy control subjects and patients with TM whereas QT(v), QTVN and QTVI values were significantly higher in patients than those in controls (QT(v), P < 0.001; QTVN, P < 0.05 and QTVI, P < 0.001) and cardiac T2* and hepatic MRI T2* values were significantly lower in patients with TM (P < 0.001). The indices of temporal QT variability correlated significantly with MRI data.

CONCLUSIONS

Young asymptomatic patients with TM have increased cardiac repolarization variability as assessed by QT variability indices, probably due to cardiac iron deposition. These easily assessed, non-invasive markers could be used to identify increased myocardial repolarization lability early in asymptomatic patients with TM.