PROJECT SUMMARY/ABSTRACT Myocardial infarction (MI) predisposes patients to ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death. After MI, alterations within the cardiac sympathetic nervous system (SNS) have been tightly linked to VT/VF. These alterations include inflammation, structural and functional remodeling within the stellate ganglion, and heterogeneous remodeling of intramyocardial sympathetic nerves in the scar-border zone. These result in enhanced and dysfunctional cardiac sympathetic neurotransmission that lead to VT/VF. Although spinal afferent signaling is enhanced after MI, the arrhythmogenic potential of spinal afferents (via maladaptive interactions with cardiac sympathetic nerves) has not been explored. Based on novel data from our group, the goal of this proposal is to test the hypothesis that chronic enhanced cardiac afferent signaling is the primary driver of sympathetic neural remodeling and dysfunction that causes VT/VF. Pilot studies from our group using epicardial resiniferatoxin (RTX) to deplete cardiac TRPV1 afferents in porcine support the rationale that persistent afferent signaling (beyond the acute ischemic phase) plays a central role in shaping the neural and cardiac substrates that lead to VAs. We will test our hypotheses using novel tools from a multidisciplinary team of investigators in 3 aims, in porcine with MI. In aim 1, we will determine whether post-MI structural, neuroinflammatory, and functional neuronal remodeling within stellate ganglia are caused by persistent TRPV1 afferent signaling. In aim 2, we will determine whether persistent cardiac TRPV1 activation amplifies intramyocardial neurotransmitter release to increase VT/VF risk. This will be accomplished using simultaneous cardiac electrophysiologic mapping and real time in vivo detection of intramyocardial Norepinephrine and neuropeptide Y levels. We will determine whether TRPV1 afferent depletion attenuates arrhythmogenicity by normalizing neurotransmitter release patterns. In aim 3, we will define the optimal site of RTX delivery for clinical management of VT/VF [Epicardial vs. Stellate Ganglion vs. Epidural application]. This will guide clinical translation of afferent neuromodulation. The results of this proposal may shift how arrhythmogenesis is approached after MI, and guide the development of new therapies that prevent altered afferent signaling after MI to fill a major clinical gap.