1. Renal Nerve Stimulation for Treatment of Neurocardiogenic Syncope
Malini Madhavan, M.B.B.S.
Division of Cardiovascular Diseases
Mayo Clinic, Rochester, MN
test

2. Neurocardiogenic Syncope: Need for Novel Therapies
Syncope in the USA
3% ER visits, 6% hospital admissions
$ 2.4 billion / year
Neurocardiogenic syncope - 22% prevalence
No uniformly effective therapy for recurrent neurocardiogenic syncope
Pacemaker implantation
Recurrence of syncope in 30%
Ann Intern Med. 2000;133: ; BMJ 2004;329:336-41; JAMA 2003;289:2224-9

3. Neurocardiogenic Syncope: Mechanism
Trigger
Vagal efferents
Bradycardia
Sympathetic efferents
Vasodilation
↓Ventricular filling
↑Inotropy
↑Cardiac mechanoreceptors
↓Vascular baroreceptors
Vascular centers in Medulla
↑Vagal output
Bradycardia
Sympathetic withdrawal
Vasodilation
Effective Rx

4. Renal Sympathetic Innervation: Efferents
Nucleus tractus solitarius
Rostral ventrolateral medulla
Hypothalamus
T5-L2
↑ Renin
Sodium retention
Renal vasoconstriction
↑ BP
Celiac, Superior mesenteric, Aorticorenal ganglia
Renal A

5. Renal Sympathetic Innervation: Afferents
↑ Central sympathetic output
Vasoconstriction
↑ Heart rate
↑ Blood pressure
Renal pelvis
T12 – L3
Nucleus tractus solitarius
Rostral ventrolateral medulla
Hypothalamus

6. Renal Denervation Renal denervation – sustained ↓ Blood pressure
↓ Central sympathetic output
↓ Muscle sympathetic nerve activity
↓ Whole body and renal norepinephrine spill- over

7. Hypotheses
Stimulation of the renal sympathetic nerves increases blood pressure
Electrical stimulation from the renal vein can stimulate the renal nerves
Close proximity of renal vein, artery and nerves

8. Aim To assess the effect of
high frequency electrical stimulation of renal nerves
from the renal vein
on blood pressure in animals

9. Methods Dogs (n=5) Baboon (n=1) Isoflurane anesthesia
Renal artery and vein angiogram

10. Methods Quadripolar catheter (4mm tip, 2mm electrode spacing)
Unilateral renal vein
High frequency stimulation ( pps, 10V, s, Grass stimulator)

11. BP During Renal Vein Stimulation in the Canine
100
200
Blood Pressure (mmHg)
Stimulation
Rapid and sustained rise in blood pressure

12. Change in Systolic Blood Pressure during Renal Vein Stimulation

13. Renal Vein Stimulation: Change in Blood Pressure
Systolic BP
Diastolic BP
Median (IQ) 11(5 – 22) mmHg
Median (IQ) 6 (-2 – 16) mmHg

14. Conclusions
Electrical stimulation of renal nerves through the renal vein
Sustained ↑ in systolic BP in the canine and baboon
Proposed mechanism
↑ Central sympathetic output
Potential applications
Neurocardiogenic syncope
Other reflex syncope
Postoperative vasoplegia
Diabetic dysautonomia leading to orthostatic hypotention
Hypotensive states in the critically ill

15. Future Directions: Novel Device for Neurocardiogenic Syncope