Autonomic Modulation as a Paradigm for Cardiovascular Treatments Kenneth Dormer1, Stavros Stavrakis2, Benjamin Scherlag2, and Sunny Po2 1Department of Physiology and Pharmacology, Liberty University College of Osteopathic Medicine,

Lynchburg, VA 24515 USA and 2Heart Rhythm Institute, Division of Cardiology, University of Oklahoma HSC, Oklahoma City, 73104 OK USA

Atrial Fibrillation- GP

Radiofrequency AblationAtrial Fibrillation-Vagal

Nerve StimulationAtrial Fibrillation- GP

Magnetically Targeted

Nanoformulation

Abstract:

Background: Structural remodeling and

associated pathologies of the autonomic

nervous system (ANS) are well recognized.

Autonomic imbalance in patients such as

increased sympathoexcitation or reduced

vagal tone can lead to hypertensive heart

disease. Innovative treatment strategies

are emerging that focus on autonomic

neuromodulation. Four existing clinical trial

strategies ( Zile & Little, 2012) include: a)

spinal cord stimulation; b) baroreceptor

activation; c) vagal nerve stimulation; and

d) renal nerve denervation. However, the

Symplicity HTN-3 renal denervation failed

in 2014, suggesting getting back to basics

in better understanding the anatomy,

neurology and physiology of the procedure.

Intrinsic Cardiac ANS Modulation: For 50 years it has been known there are

multiple layers of cardiac control, central

and intrathorasic (extra-and intra-cardiac).

Intracardiac ganglionated plexi (GP), the

largest are near the pulmonary vein –atrial

junction, are major components of the

intrinsic cardiac ANS (ICANS) and

integrate with descending ANS extrinsic

cardiac nerves. There are 2-way

interdependent neural communications

between ICANS, extracardiac nerves and

the medullary CNS. Our group has been

exploring autonomic modulation and the

role of GP from the perspective of

arrhythmogenesis (atrial fibrillation, AF).

Previous studies have shown

cardiovascular responsiveness decreases

with age, suggesting dysautonomic

imbalance between the extrinsic and

ICANS.

Atrial Fibrillation-Tragus

Stimulation

Background: Continuously variable external

electromagnets are the optimal means of targeting

magnetically susceptible nanoparticles for delivery of

therapeutic substances to targeted tissues. The

scientific teams of NTS Inc. include physicists,

engineers, clinician, physiologists,

pharmacologist/toxicologist, chemist and pathologist

for the design and testing of an electromagnetic

system for targeted delivery. We have proven the

concept of magnetic targeting in the canine, using

permanent magnets placed over the GP to target

neurosuppressants. AF inducibility has been reduced

(Yu, 2011). Continuing studies using external, variable

electromagnets have shown capture of magnetite-

polymer-drug NP in coronary arteries and

extravasation into atrial epicardium surrounding GP.

Background: Four major ICANS GP are located

on the atrial epicardial surface (see Figure). First

discovered in the 1970’s, these GP integrate extrinsic

and intrinsic cardiac ANS with chronotropic,

dromotropic and inotropic consequences. Relatively

recently, radio-frequency (RF) ablation of specific GP

has been added to the usual ablation regimen of

pulmonary vein isolation (PVI), standardly performed

by catheter or surgical techniques. Major GP have

been implicated in AF. Imbalance between cardiac

extrinsic and intinsic ANS may be responsible for AF,

especially in the aged. Such dystonia may be

corrected by reducing GP tone. We have shown that

an approach with less invasion, risk and cost can

reduce GP activity. Targeting magnetic nanoparticles

carrying neuromodulation drugs to GP has acutely

prevented/suppressed AF in dogs.

Vaso-Vagal Syncope-

GP Ablation

Autonomic Modulation as a paradigm for Cardiovascular Treatments

Kenneth Dormer1, Benjamin Scherlag2, Stavros Stavrakis2, and Sunny Po2

1 Integrative Physiology & Pharmacology Department, Liberty University

College of Osteopathic Medicine, Lynchburg, VA 24515, USA. 2 Heart

Rhythm Institute, Division of Cardiology, University of Oklahoma Health

Sciences Center, Oklahoma City, OK 73104 USA

Objective: Consider physiological interventions of the autonomic nervous

system (ANS) related to treatments for cardiovascular diseases, especially

arrhythmias, and note a developing theme for autonomic modulation.

Summary: Increasingly, experimental and clinical data on ANS denervation

or stimulation are reporting therapeutic effects: a) Regional radiofrequency

catheter ablation of atrial ganglionated plexi (GP) restored sinus rhythm in

71% of patients with atrial fibrillation (AF); b) Low level electrical stimulation

of the vago-sympathetic trunks significantly suppresses AF inducibility in the

canine; c) our demonstration that polymeric magnetic nanoparticles

delivering a neurosuppressant payload while extravasated and targeted by

an external magnetic field to GP, suppressed/prevented AF inducibility; d)

Vaso-vagal syncope (intrinsic cardiac ANS dysreflexia) had no recurrence in

patients with partial GP ablations; and e) Low level transcutaneous electrical

stimulation of the auricular branch of the vagus nerve at the tragus of the

ear suppresses AF in patients. Forty patients with paroxysmal AF about to

undergo radiofrequency ablation for AF were randomized into two groups.

Pacing –induced AF duration was significantly decreased by low level

stimulation of the tragus.

Conclusion: Together these observations suggest that selective ANS

denervation, stimulation or suppression, delivered by devices, electrodes or

magnetically targeted nanoformulations represent a paradigm of ANS

modulation that might present as future therapeutic cardiovascular

interventions.

Funding: Magnetic Targeting Studies: NanoMed Targeting Systems Inc.,

Oklahoma City (www.nanomed-systems.com)

ANS Modulation-Clinical: Catheter and

surgical RF lesions of major GP can

complement PVI RF lesions for the prevention

of AF.

Background: Efferent vagal stimulation has

previously been associated with termination of

ventricular tachycardia (Waxman, 1977), prevention of

sudden cardiac death (canine; Vanoli, 1991) and

amelioration of heart failure. We have shown,

however, low level vagal stimulation, below efferent

bradycardic effects, experimentally protects against AF

(Scherlag, 2011). We reduced AF inducibility following

stimulation of the vago-sympathetic trunk at either 1 V

or 10-50% below threshold. The vagal complex

provides two way communications and physiological-

pathophysiological information for the heart (Ardell,

2004). This paradigm may apply to other viscera as

well.

Waxman et al., Circ, 1977; Vanoli et al., Circ Res,

1991; Scherlag et al., J Cardiovasc Translational Res,

2011; Armour & Ardel, Basic and Clinical Clinical

Neurocardiology, 2004; Yu et al., Heart Rhythm, 2012

(manuscript)

ANS Modulation-Experimental: Efferent

vagal stimulation, below the threshold of

afferent bradycardia, has a central ANS-

mediated effect on the GP in suppressing AF.

ANS Modulation-Experimental:

Neurosuppressant drugs, magnetically targeted

to selected GP in nanoparticles, suppresses or

prevents AF.

ANS Modulation-Experimental: GP are in

the pathway responsible for HR slowing in

vaso-vagal syncope. ARGP anesthesia

attentuated HR slowing and prevented

asystole

ANS Modulation-Clinical & Experimental:

Low level tragus stimulation suppresses AF

and decreases inflammatory cytokines in

patients with paroxysmal AF, supporting the

emerging paradigm of neuromodulation of AF.

Background: We recently have shown in canines

and 40 patients that low-level transcutaneous

electrical stimulation of the auricular branch of the

vagus nerve at the tragus (LLTS), suppresses AF. The

vagus contains many afferents relaying cardiac status

to the medullary control regions. We examined if

LLTS suppressed AF inducibility and duration, as well

as, decreased acute AF-related inflammatory and pro-

thrombotic effect in patients with paroxysmal AF.

Methods: 16 anesthetized dogs; electrodes attached

to pulmonary veins and atria; microelectrodes

inserted into anterior right GP; Rapid atrial pacing

(RAP) induced atrial remodeling and AF tragus clips

stimulated at 20 Hz at 80% below threshold for

slowing sinus rate. Effective Refractory Period (ERP)

and window of vulnerability (AF inducibility) (WOV)

were measured.

40 patients with AF, who were undergoing RF ablation

procedures, were randomized to receive 1 hr. of LLTS

at 50% below threshold stimulation at 20 Hz, or

control no stimulation. Blood samples were drawn

from coronary sinus or femoral vein before and

following 1 hr. of stimulation and analyzed for TNF-α,

C-reactive protein and interleukin-6. Results : Dogs:

Rapid atrial pacing increased WOV and decreased

ERP (P<.05). LLTS returned ERP, WOV and neural

activity to baseline levels (P<.05). Patients: AF

duration decreased and AF cycle length

increased significantly from baseline in

the LLTS group but not in the control

group. Systemic cytokines changed

favorably only in the LLTS group.

Zile & Little, JACC, 2012; Scherlag et al., J

Cardiovasc Translational Res, 2011;

Schlaich et al., Frontiers in Physiol, 2012

and Curr Hyperten Res, 2012; Xu, Clin Sci

(Lond), 2014

Conclusion: ANS experimental

modulations are emerging as

translatable therapeutic treatment

paradigms for cardiovascular diseases.

Stavrakis et al., Heart Rhythm, 2014; Yu et al. Heart

Rhythm, 2013; Ustinova & Shultz, Circ Res, 1994;

Yu et al., Circ, 2011; Singh et al., J. Thorasic & Cardiovasc Surg, 1996;

Armour et al., Am J Physiol Regul Integr Comp

Physiol, 2004; Haisaguerre et al., Circ, 1992;

Scherlag & Jackman, Circ, Arr & Electrophys, 2014

Pokushalov et al., JACC, 2014.

Background: Different syncope syndromes are

under the umbrella of vasovagal syncope. The

central mechanism commonly leads to loss of

consciousness. Clinical studies indicate that GP

ablation prevents syncopal episodes of vaso-vagal

syndrome (V-VS). The cardioinhibitory response is

decreases in HR, cardiac output and arterial

pressure. This response is primarily from enhanced

parasympathetic tone. But mechanism(s) underlying

GP amelioration of V-VS are unknown. We

hypothesize that V-VS may be due to an “epileptic

type” burst of electrical activity in the medulla leading

to a transient hyperactive state of the extrinsic

autonomic nervous system.

Methods: 10 anesthetized dogs, left and right

cervical vagal trunks (LVG and RVG) were dissected;

wire electrodes inserted for electrical

stimulation. After thoracotomy, a plaque electrode

was attached to the anterior right ganglionated plexi

(ARGP). Electrical stimulation at each site

decreased HR by 50%. We determined the HR

slowing induced by RVG+LVG, RVG +ARGP,

LVG+ARGP and RVG+LVG+ARGP at voltages

required for 50% slowing for each of the 3

modalities. Results: Average baseline HR was 130

beat/min. Combination of RVG+LVG induced a

greater than 74%, HR slowing vs. either RVG

(p=<0.0001) or LVG (p=0.0002) alone. RVG+ARGP

and LVG+ ARGP induced a greater than 65.9% and

71.8% HR slowing, respectively, than either RVG

(p=0.0002) or LVG (p=<0.0001). Combined RVG+

LVG+ARGP induced the greatest (78.7%) change in

HR (10 to 42/min) and preceding asystolic periods of

3 to 7 seconds. Lidocaine injection into ARGP

markedly attenuated the HR slowing and prevented

asystole. Conclusion: Combined stimulation of the

Vagal trunks+ ARGP models the cardioinhibitory form

of V-VS with a common pathway mediated through

GP.

Magnetic capture, extravasation and targeting

Figure . Diagram of the atria as seen from a right thoracotomy. Electrode

catheters were sutured at the right superior and right inferior PVs (RSPV

and RIPV, respectively) and on the right atrial appendage (RAA). SVC

indicates superior vena cava; IVC, inferior vena cava. ARGP and IRGP are

anterior right and left ganglionated plexi.

Figure. Example of magnetic targeting. Microinjection of MNPs carrying 0.4

mg polymer-magnetite-neurosuppressant payload into the ARGP (n=6). Left,

Two hours after the injection, the maximal decrease in sinus rate by ARGP

stimulation was reduced from 408% to 219%. Right, AF threshold also

significantly increased 2 hours after injection. BS indicates baseline.

Yao et al., Circ Arrhyth & Electrophys, 2012; Pachon

et al., Europace, 2011;

Left Figure: 6 hrs. of rapid atrial

pacing increased the

vulnerability to inducing AF

(window of vulnerability, msec

accumulations); *** p<0.001,

∆∆∆ p<0.05 compared to

baseline and end of 3rd hour of

rapid atrial pacing.

Left Figure: AF inducibility is

reduced with the addition of low

level vagal stimulation from a

stimulating catheter positioned

at the superior vena cava; **

p<0.01, ∆∆ p<0.01 compared to

baseline and end of rapid atrial

pacing.

Right Figure: 6 hrs. of rapid atrial

pacing increased activity in neural

recordings from the ARGP. Both

the number of spikes and

recruitment increased. When low

level vagal nerve stimulation was

added (lower recording) the

amount of GP activity was

suppressed, illustrating the

probable basis for the suppression

of AF emanating from overactive

GP by vagal (afferent) activity.

Figure. RVG or ARGP

stimulation separately

reduced HR by 50%

(78/min). Combined

RVG+ARGP at their 50%

voltage resulted in asystole

of almost 3 secs and a rate

averaging 38/min (Panel

A). After lidocaine, a local

anesthetic, was injected

into the ARGP. the

combined effects of RVG

+ARGP stimulation at 50%,

the HR slowing was

markedly attenuated

(Panel B).

Figure. More

typical PVI RF

ablation

Figure. PVI

RF ablation

also including

GP ablations

Figure. In the dog model, the

remodeling effect on duration of AF is

shown to be suppressed by the

addition of LLTS vagal stimulation on

top of rapid atrial pacing. This

reduction occurred at 50-80% of the

threshold for slowing the sinus rate.

Additionally, ARGP neuronal activity

was decreased

Figure. (above left) Comparison of patients that received LLTS with

controls (no stimulation) showing significant reduction in AF duration.

(above right) comparison of patients’ reduction in release of the

inflammatory cytokineTNFα in systemic blood as a result of LLTS.

stimulating

electrode