Autonomic Nervous System Dysfunction: JACC Focus Seminar

Abstract

Autonomic nervous system control of the heart is a dynamic process in both health and disease. A multilevel neural network is responsible for control of chronotropy, lusitropy, dromotropy, and inotropy. Intrinsic autonomic dysfunction arises from diseases that directly affect the autonomic nerves, such as diabetes mellitus and the syndromes of primary autonomic failure. Extrinsic autonomic dysfunction reflects the changes in autonomic function that are secondarily induced by cardiac or other disease. An array of tests interrogate various aspects of cardiac autonomic control in either resting conditions or with physiological perturbations from resting conditions. The prognostic significance of these assessments have been well established. Clinical usefulness has not been established, and the precise mechanistic link to mortality is less well established. Further efforts are required to develop optimal approaches to delineate cardiac autonomic dysfunction and its adverse effects to develop tools that can be used to guide clinical decision-making.

Keywords: arrhythmia; autonomic; heart failure; myocardial infarction.

FIGURE 1. Autonomic Neural Control of the Heart

Autonomic neural control of the heart. Modified with permission from Shivkumar et al. (4). DRG= dorsal root ganglion; ICNS = intrinsic nervous system; SG = stellate ganglion.

FIGURE 2. Functional Organization of Cardiac Neural Control

The shaded areas (yellow = sympathetic fibers, grey = parasympathetic fibers [vagal trunk]) roughly correspond to the anatomical sympathetic and parasympathetic nerve fibers that are seen macroscopically. The afferent neural fibers run along with nerves anatomically referred to as sympathetic and parasympathetic trunks. Modified with permission from Shivkumar et al. (4). Aff = afferent; LCN = local circuit neuron; other abbreviation as Figure 1.

FIGURE 3. Diagram of the QT-RR Relationship

The QT-RR relationship in the early post-exercise recovery period without autonomic blockade (baseline [orange]), with beta-blockade (green), with parasympathetic blockade (atropine [grey]), and double blockade with propranolol and atropine (blue). Original data from Sundaram et al. (160).