Different contribution of sympathetic nerve activity to arterial velocity pulse index in hypertensive patients with and without diastolic dysfunction

Introduction

Left ventricular diastolic dysfunction (LVDD) is the main cause of heart failure with preserved ejection fraction (HFpEF). LVDD is related not only to arterial stiffness but also sympathetic nerve activity (SNA). Recent study demonstrated that increased muscle sympathetic nerve activity (MSNA) may be one of contributing factor for arterial stiffness. In clinical practice, Cardio-ankle vascular index (CAVI) provides a reproducible index of arterial stiffness, independent of blood pressure (BP). Recently, Arterial Velocity pulse Index (AVI), which is an index of arterial reflected waves, have been proposed as new index of arterial stiffness. We reported that AVI was associated with MSNA in hypertensive (HT) patients. However, it is still uncertain the effect of LVDD on the association between AVI and SNA in HT patients. Thus, we tested the hypothesis that AVI would be increased and related to MSNA in HT patients with LVDD.

Methods

Patients with essential HT subjects were included in this study. HT was diagnosed as systolic blood pressure (SBP) ≥140mmHg or diastolic blood pressure (DBP) ≥90mmHg. Patients with secondary HT was excluded. AVI was measured from left upper arm by NAS-1000 (Nihon Koden, Japan). CAVI was measured by VaSera VS-1500A (Fukuda Denshi, Japan). Transthoracic echocardiography was performed by trained sonographers. SNA was evaluated by direct recording of MSNA from peroneal nerves.

Results

25 HT patients were included (age 63±14 years, Male/Female 9/16). They were divided into two groups according to E/e' (no LVDD group, E/e' ≤9, N=12; LVDD group, E/e' >9, N=13). There were no significant differences between no LVDD and LVDD groups in age (63±9 vs 69±9 years p=0.205), body mass index (23±3 vs 24±4 p=0.355), BP (SBP 139±16 vs 144±20mmHg p=0.524, DBP 87±15 vs 78±14mmHg p=0.167). LV Ejection Fraction (EF) and Stroke Volume (SV) did not differ between two groups (EF 66±7 vs 69±6% p=0.471, SV 58±7 vs 62±14ml p=0.599). MSNA had tendency to increase in LVDD group compared to no LVDD group (MSNA 53±10 vs 44±12 bursts/100 heartbeats, p=0.052). Contrary to our hypothesis, AVI and CAVI did not differ between two groups (AVI 27±7 vs 29±7 p=0.398, CAVI 8.7±1.4 vs 8.6±1.4 p=0.894). However, a significant correlation was seen between AVI and MSNA in no LVDD group (r=0.57, p<0.05), but no correlation in LVDD group. There is no correlation between CAVI and MSNA in no LVDD and LVDD group. Significant relationship was observed between AVI and CAVI in LVDD group (r=0.61, p<0.05), but no relationship in no LVDD group.

Conclusion

AVI was significantly associated with MSNA in HT patients without LVDD, but not with LVDD. CAVI was related to AVI in HT patients with LVDD, but not without LVDD. MSNA was slightly increased in HT patients with LVDD compared to without LVDD. These results indicate that augmented SNA could contribute to the increase in arterial stiffness in HT patients without LVDD, however, this contribution might be attenuated in HT patients with LVDD.

Funding Acknowledgement

Type of funding sources: None.

Effect of pulmonary vein isolation on left atrial remodeling and muscle sympathetic nerve activity in patients with atrial fibrillation

Background

Catheter ablation (CA) for atrial fibrillation (AF) improves left ventricular function and induces left atrium reverse remodeling (LARR). CA is also associated with the modulation of ganglionated plexi in the left atrium (LA), including stretch-sensitive sympathetic and parasympathetic nerve mechanoreceptors. Increased filling pressure and enlargement of LA stimulate stretch-sensitive sympathetic nerve mechanoreceptors in heart failure, which contribute augmented sympathetic nerve activity. However, little is known about an effect of CA on the interaction between the changes of LARR and sympathetic nerve activity.

Purpose

To test the hypothesis that CA induce the reduction in sympathetic nerve activity in accordance with LARR in patients with atrial fibrillation.

Methods

This study was conducted as a retrospective, observational study. Twenty-eight AF patients (65.4±12.1 years old) were included in this study. We measured mean blood pressure (BP), heart rate (HR), brain natriuretic peptide (BNP), and direct recording of muscle sympathetic nerve activity (MSNA) using microneurography technique before and 12 weeks after CA. Echocardiogram was also performed to assess LARR and left ventricular function. To evaluate the interaction between LARR and MSNA, AF patients were divided into two groups by presence (LARR group; n=18) and absence (no LARR group; n=10) of LARR according to left atrium volume index (LAVi) following CA.

Results

No significant differences were observed at baseline in BP, MSNA and LAVi between two groups. BP did not change significantly after CA in both groups. HR significantly increased in the LARR group (63.1±5.7 vs 69.9±7.8, p<0.01) compared to no LARR group. CA significantly reduced MSNA in the LARR group (37.8±10.1 vs 24.9±8.8 bursts/min, p<0.01), but there was no significant change in the no LARR group. The septal E/e' ratio (11.3±3.8 vs 9.8±2.9, p<0.05), left ventricular end-systolic volume index (LVESVi) (24.4±11.9 vs 19.6±7.8 ml/m2, p<0.05) and Ln BNP (4.0±1.2 vs 3.3±1.0 log/pg/ml, p<0.05) were also significantly improved in the LARR group. On the other hand, in the no LARR group, there were no significancy in the changes of the septal E/e' ratio, LVESVi and Ln BNP. LVEF was not significantly changed in both two groups.

Conclusion

Our study shows CA reduced MSNA accompanied by LARR in AF patients. The reduction in MSNA, septal E/e' ratio, LVESVi and Ln BNP were all more pronounced in the LARR group compared to the no LARR group. These findings suggest that LARR is associated with the reduction in MSNA in AF patients, which was attributed to CA-induced modulation of stretch-sensitive sympathetic nerve mechanoreceptors.

Funding Acknowledgement

Type of funding sources: None.

Age differences in the association between arterial velocity pulse index and muscle sympathetic nerve activity in hypertensive patients

Background

Increased arterial stiffness characterize by aging. It is reported that age-related increases in muscle sympathetic nerve activity (MSNA) may be one of contributing factor for arterial stiffness. Arterial reflected wave was composed of SNA and aging. Increased arterial reflected wave partly plays an important role in blood pressure. Recently, we reported that arterial velocity pulse index (AVI), a novel index of arterial reflected waves, was associated with MSNA in hypertensive patients. It is still uncertain the effect of age on the association between AVI and SNA in hypertensive patients.

Method

Patients with essential HT and matched non-hypertensive control subjects were included in this study. HT was diagnosed as systolic blood pressure (SBP) ≥140 mmHg or diastolic blood pressure (DBP) ≥90 mmHg. AVI was measured from left upper arm by NAS-1000. SNA was evaluated by direct recording of muscle sympathetic nerve activity (MSNA) from peroneal nerves.

Results

45 HT patients and 46 control subjects were included. Age, SBP and DBP were significantly increased in HT group compared to control (Age 63±14 vs 42±16 years, p<0.001; SBP 144±16 vs 115±9 mmHg, p<0.001; DBP 80±14 vs 67±9 mmHg, p<0.001). MSNA and AVI were significantly increased in HT group compared to control (MSNA 34±10 vs 25±8 bursts/min, p<0.05; AVI 28±9 vs 17±5, p<0.05). AVI was significantly correlated with MSNA, age, and SBP in HT group. HT group was divided into two groups according to their age (group 1, age ≤63 N=21, group 2, age ≥64 N=26). AVI in group 1 showed correlation with MSNA (r=0.59, p<0.05), but no correlation was seen in group 2. However excluded SBP>160 mmHg subjects in group 2, significant correlation was clarified between AVI and MSNA (r=0.62, p<0.05).

Conclusion

The relationship between AVI and MSNA in HT patients is preserved regardless of aging, however, high blood pressure over 160mmHg might obscure its correlation. These results indicate that AVI is useful to estimate sympathetic nerve activity in high aging HT patient treated <160 blood pressure.

Funding Acknowledgement

Type of funding sources: None.

Novel index of arterial reflected waves, Arterial Velocity pulse Index, relates to muscle sympathetic nerve activity independent of Arterial Pressure volume Index in patients with hypertension

Background

Arterial reflected wave is determined by not only atherosclerosis but also sympathetic nerve activity. Recently, Arterial Velocity pulse Index (AVI), which is an index of arterial reflected waves, and Arterial Pressure volume Index (API), which is an index of volume of a conductive blood vessel, have been proposed as new index of arterial stiffness. However, it is unclear whether API and AVI would be associated with muscle sympathetic nerve activity (MSNA) in hypertensive subjects.

Purpose

The purpose of this study was to evaluate the correlation between AVI, API and MSNA in hypertensive subjects.

Method

41 hypertensive patients and 40 non-hypertensive subjects were included in this study. We performed a cross-sectional, observational study. Hypertension (HT) was defined as systolic blood pressure (SBP) ≥140 mmHg, diastolic blood pressure (DBP) ≥90 mmHg or medical treatment for HT. AVI and API was measured by NAS-1000 (Nihon Koden, Japan). MSNA, central sympathetic outflow to peripheral muscle, was recorded directly from peroneal nerve. MSNA was expressed by burst frequency (bursts/minute) and burst incidence (bursts/100heartbeats). Blood pressure, heart rate and MSNA were recorded simultaneously.

Results

Age, systolic and diastolic pressure were significantly higher in hypertensive patients compared to control (40±15 vs 61±13 years, p<0.001; 142±16 vs 113±9 mmHg, p<0.001; 81±14 vs 67±9 mmHg, p<0.001). MSNA and AVI were significantly augmented in hypertensive patients compared to control (34±11 vs. 23±6 bursts/min, p<0.05; 26±7 vs. 16±4, p<0.05). AVI was correlated with MSNA in each group (hypertension: r=0.59, P<0.001, non-hypertension: r=0.51, p<0.001). However, no correlation was shown between API and MSNA in each group (hypertension: r=0.22, p=0.15, non-hypertension: r=0.07, p=0.63). Multiple regression analysis also showed MSNA was significantly related with AVI but was not with API.

Conclusion

Our finding showed that AVI relates to MSNA independent of API in patients with hypertension. It suggested that Novel index of arterial reflected waves, AVI, is helpful to estimate augmented SNA in hypertensive subjects regardless of volume of a conductive blood vessel.

Funding Acknowledgement

Type of funding source: None

P3559Renal sympathetic nerve activity, assessed by renal 123-iodine metaiodobenzylguanidine scintigraphy, reflects disease severity in heart failure with reduced ejection fraction

Background

Sympathetic nerve activity is related to cardio-renal syndrome, which plays a crucial role in deterioration in heart failure with reduced ejection fraction (HFrEF). Previous studies reported that renal denervation was effective in HFrEF patients. Recently, we have demonstrated that renal 123-iodine metaiodobenzylguanidine (MIBG) scintigraphy is useful for assessment of renal sympathetic function in hypertension. However, it is unclear whether renal MIBG would reflect disease severity in HFrEF patients.

Methods

Twenty-four HFrEF patients and eleven control without heart failure were included in this study. HFrEF patients were performed MIBG and MSNA and hemodynamics inspection using Swan-Ganz's catheter (SGC). HFrEF was defined as echocardiography with EF of 50% or less. MSNA was recorded from the right peroneal nerve to evaluate direct sympathetic nerve activity to the peripheral vascular bed. MSNA was expressed as the number per minute (burst frequency = BF) and the number per 100 heartbeats (burst incidence = BI). Renal MIBG scintigraphy was simultaneously performed with cardiac MIBG scintigraphy. The 20 minutes (early) and 180 minutes (delayed) kidney-to-mediastinum ratio (K/M), early and delayed heart-to-mediastinum ratio (H/M), and washout rate (WR) were measured.

Results

In the HFrEF group, the EF was significantly lower than control group (EF 34.8±9.51% vs. 63.0±7.43, p<0.01), and MSNA parameters were significantly increased (burst incidence (BI), 57.7±18.7 vs. 37.0±11.3, p<0.01; BF 42.7±14.4 vs. 24.1±8.50, p<0.01). WR of cardiac MIBG was not related to MSNA parameters but negatively related to cardiac output (r=−0.46, p<0.05) and stroke volume (r=−0.61, p<0.01) and delayed H/M negatively correlated with mean pulmonary capillary wedge pressure (r=−0.57, P<0.05). WR of both left and right renal MIBG showed a strong correlation with MSNA (BI; left, r=0.69, p<0.01, right 0.60, p<0.01, BF; left, r=0.64, p<0.01, right, r=0.58, p<0.01) and no significant correlation between renal MIBG and hemodynamics parameters. HFrEF patients were divided into stage B and stage C based on American College of Cardiology/American Heart Association (ACC/AHA) classification (stage B, n=13; stage C, n=11). There was no significant difference between the two groups in cardiac MIBG parameters. Renal WRs in stage C was increased than stage B (Lt renal WR,51.6±10.6 vs. 40.6±6.53, p<0.05; Rt renal WR, 43.9±9.97 vs. 35.1±11.3, p<0.05).

Conclusions

Cardiac WR negatively correlated with cardiac output and renal WR correlated with MSNA. Renal WRs had a significant difference in the heart failure stage of ACC/AHA classification, but cardiac MIBG parameters did not. These results indicate that renal MIBG might be useful to assess renal sympathetic nerve activity in patients with HFrEF and suggesting that renal SNA might be promising therapeutic target in HFrEF.

1417Effect of sodium glucose cotransporter 2 inhibitor on sympathetic nerve activity in type 2 diabetes mellitus patients

Background

Diabetes mellitus (DM) is a well-known risk factor for cardiovascular diseases. Augmented sympathetic nerve activity plays an important role in the progressive worsening disease severity. Most of anti-diabetic drugs were demonstrated to not only decrease blood glucose, but also increase sympathetic nerve activity. Recently, it has been reported that sodium glucose cotransporter 2 (SGLT2) inhibitor has beneficial effects on cardiovascular events in spite of the decrease in blood glucose in type 2 DM patients. The underlying mechanisms remain speculative; however, it is assumed that SGLT2 inhibitor would improve sympathetic nerve activity in type 2 DM patients.

Purpose

The purpose of this study was to evaluate the effect of SGLT2 inhibitor on sympathetic nerve activity in type 2 DM patients.

Methods

This study was designed as the prospective single-arm study. Type2 DM patients whose HbA1c >7.0% with at least one atherosclerotic risk factors (Hypertension, obesity, smoking history, aging ...) were included. Patients who had renal failure (eGFR<45ml/min/1.73m2) or high age patients (>80 years old) were excluded. We measured blood glucose, HbA1c and blood insulin concentration at baseline and 12 weeks after treatment of dapagliflozin (5mg/day). Muscle sympathetic nerve activity (MSNA) was applied to scrutinize accurate sympathetic nerve activity in type 2 DM patients. Also, baroreflex sensitivity was calculated by examining the relationship between MSNA and beat to beat diastolic blood pressure.

Results

Eleven type2 DM patients were included in this study. Body mass index, blood pressure, HbA1c and blood insulin concentration tended to decrease at 12weeks after dapagliflozin (body mass index: 27.2±6.3 vs. 24.9±3.2 kg/m2. systolic blood pressure: 121±12.3 vs. 118±13.6 mmHg. diastolic blood pressure: 74.3±6.3 vs. 72.5±7.6 mmHg. HbA1c: 7.6±0.3 vs. 7.2±0.7%. insulin: 9.7±7.2 vs. 8.8±5.1 μU/ml). Dapagliflozin significantly decrease MSNA and heart rate compared to baseline (46.7±7.5 vs. 38.6±6.9 bursts/minute, P<0.05. Heart rate: 80.6±8.5 vs. 72.8±7.4 beats per minute, P<0.05). However, there is no interaction between the reduction in MSNA and baroreflex sensitivity or insulin resistance.

12 weeks administration decreased MSNA

Conclusion

Our data demonstrated that dapagliflozin significantly decreased MSNA and HR beyond the lowering effect of blood glucose in type2 DM patients. These results indicate the favorable effect of SGLT2 inhibitor might be, in part, attributed to the improvement in sympathetic nerve activity.

P1580Left atrial volume index predicts improvement in renal function after catheter ablation of atrial fibrillation

Background

Atrial fibrillation (AF) increased the risk of development of kidney disease. The elimination of AF by catheter ablation is associated with improvement in renal function. However, the mechanism of cardio-renal interaction in AF has not been fully elucidated.

Purpose

We tested the hypothesis that left atrial volume index (LAVI), which is a marker of left atrial mechanical reserve, predicts improvement in renal function after restoring sinus rhythm with catheter ablation of AF.

Methods

We analyzed consecutive patients who underwent catheter ablation of AF from January 2012 to October 2018 and had completed follow-up more than 3 months after catheter ablation. Exclusion criteria were need for hemodialysis and acute hospitalization. Estimated glomerular filtration rate (eGFR) was assessed on admission and at the end of follow-up periods after catheter ablation and the difference was defined as ΔeGFR. Left atrial volume index was derived using the biplane area-length method.

Results

A total of 159 AF patients (paroxysmal 112 [70%], persistent 47 [30%]) were included in this study. The mean age was 65±11 years and 74% were male. During the mean follow-up period of 7.9±3.2 months, 105 patients (66%) were free from atrial tachyarrhythmias and 54 (34%) experienced the recurrence. Baseline eGFR and LAVI were not significantly different between the non-recurrence group and the recurrence group (71.0±17.4 and 75.1±22.8 mL/min/1.73m2; p=0.24, 35.7±12.5 and 37.9±15.0 ml/m2; p=0.34). ΔeGFR in the non-recurrence group was significantly greater compared with the recurrence group (+1.5±1.0 versus −4.3±1.4 mL/min/1.73m2; p=0.001). Baseline LAVI was negatively correlated with ΔeGFR in the non-recurrence group (r=−0.3; p=0.002; Figure), but not in the recurrence group (p=0.1). Multiple regression analysis in the non-recurrence group identified baseline LAVI (β=−0.35, p<0.001), baseline age (β=−0.31, p<0.001) and baseline eGFR (β=−0.59, p<0.001) as independent predictors for eGFR improvement after catheter ablation. In the patients with LAVI <34 ml/m2, age <70 years and eGFR <90 mL/min/1.73m2, the mean ΔeGFR was +6.3±1.9 mL/min/1.73m2.

Figure 1

Conclusions

LAVI, a marker of left atrial mechanical reserve, was an independent predictor of improvement in renal function after restoring sinus rhythm with catheter ablation of AF. This observation suggests that AF-related deterioration of renal function is due at least in part to impaired atrial mechanical function.

Fabrication of air-stable, transparent Cu grid electrodes by etching through a PVA-based protecting layer patterned using a screen mesh

As an alternative to conventional indium-tin-oxide (ITO) electrodes, a transparent Cu grid electrode was fabricated by etching a sputtered Cu on a flexible polyethylene naphthalate film through a polyvinyl alcohol (PVA)-based protecting layer. The masking pattern of the PVA-based polymer on the Cu was generated by evaporation of an aqueous solution containing PVA-based polymers using a screen mesh as a template. The solution formed a stable liquid-bridge network between contact points of the screen mesh and the substrate after being dropped onto the mesh placed on the substrate. Drying of the solution yielded grid or dotted patterns, depending on the concentration of PVA. Etching of the Cu film covered with the PVA pattern was done with a FeCl3 methanolic solution to form a grid-patterned Cu electrode. Although some underetching was observed, adjusting the etching time gave a fine line network of Cu with the PVA coated thoroughly. The Cu grid electrode showed a transparency of 87.2 ± 5.2% at 550 nm and 6.1 ± 5.3 Ω □-1, which is comparable to or greater than that of the conventional ITO. Furthermore, we found that the PVA coating barrier significantly enhanced the oxidation resistance of the Cu grid electrode.