Scalable and reversible axonal neuromodulation of the sympathetic chain for cardiac control

Maladaptation of the sympathetic nervous system contributes to the progression of cardiovascular disease and risk for sudden cardiac death, the leading cause of mortality worldwide. Axonal modulation therapy (AMT) directed at the paravertebral chain blocks sympathetic efferent outflow to the heart and maybe a promising strategy to mitigate excess disease-associated sympathoexcitation. The present work evaluates AMT, directed at the sympathetic chain, in blocking sympathoexcitation using a porcine model. In anesthetized porcine (n = 14), we applied AMT to the right T1-T2 paravertebral chain and performed electrical stimulation of the distal portion of the right sympathetic chain (RSS). RSS-evoked changes in heart rate, contractility, ventricular activation recovery interval (ARI), and norepinephrine release were examined with and without kilohertz frequency alternating current block (KHFAC). To evaluate efficacy of AMT in the setting of sympathectomy, evaluations were performed in the intact state and repeated after left and bilateral sympathectomy. We found strong correlations between AMT intensity and block of sympathetic stimulation-evoked changes in cardiac electrical and mechanical indices (r = 0.83-0.96, effect size d = 1.9-5.7), as well as evidence of sustainability and memory. AMT significantly reduced RSS-evoked left ventricular interstitial norepinephrine release, as well as coronary sinus norepinephrine levels. Moreover, AMT remained efficacious following removal of the left sympathetic chain, with similar mitigation of evoked cardiac changes and reduction of catecholamine release. With growth of neuromodulation, an on-demand or reactionary system for reversible AMT may have therapeutic potential for cardiovascular disease-associated sympathoexcitation. NEW & NOTEWORTHY Autonomic imbalance and excess sympathetic activity have been implicated in the pathogenesis of cardiovascular disease and are targets for existing medical therapy. Neuromodulation may allow for control of sympathetic projections to the heart in an on-demand and reversible manner. This study provides proof-of-concept evidence that axonal modulation therapy (AMT) blocks sympathoexcitation by defining scalability, sustainability, and memory properties of AMT. Moreover, AMT directly reduces release of myocardial norepinephrine, a mediator of arrhythmias and heart failure.