Renal nerve stimulation for the treatment of neurocardiogenic syncope

Abstract

Neurocardiogenic syncope is a common disorder resulting from a transient increase in vagal tone and central sympathetic withdrawal leading to varying degrees of vasodilation and bradycardia. Hence an effective treatment should address both the bradycardia and vasodilation. We hypothesized that, stimulation of the renal sympathetic nerves using high frequency stimulation in the renal vein will increase blood pressure through an increase in sympathetic output and therefore may be of use in treating neurocardiogenic syncope. Renal nerve stimulation was performed under Isoflurane anesthesia in 5 dogs and 1 baboon using a 4mm quadripolar catheter in unilateral renal vein using a Grass stimulator (square wave, 120V, 900pps, 30-200s). A consistent increase in arterial systolic BP [mean (SD) pre- vs peak-stimulation 103 (±27) vs. 122 (±41) mmHg] and diastolic BP [69 (±19) vs. 82 (±31) mmHg] was noted during stimulation. Median interquartile change in systolic BP was 11 (5-22) mmHg and 6 (-2-16) mmHg in diastolic BP. To conclude, renal nerve stimulation through the renal vein increased BP. Potential applications include treatment of vasodilatory component of neurocardiogenic syncope and confirmation of successful renal nerve ablation for the treatment of hypertension.