Are heart palpitations part of the autonomic nervous system?

Heart Palpitations and the Autonomic Nervous System

Yes, heart palpitations are fundamentally regulated by and often triggered through the autonomic nervous system, which continuously modulates heart rate, rhythm, and contractility through both sympathetic and parasympathetic pathways.

Autonomic Control of Cardiac Function

The autonomic nervous system serves as the primary regulator of cardiac rhythm and the sensation of heartbeat:

• The cardiovascular branch of the autonomic nervous system is responsible for regulation of heart rate, blood pressure, and maintaining homeostasis during physiological stress 1
• Parasympathetic preganglionic neurons originate from the nucleus ambiguus and dorsal motor nucleus in the brainstem, projecting to postganglionic neurons in ganglionated plexi on the heart 2
• Vagal efferents reduce heart rate by slowing sinus node automaticity and AV nodal conduction 2
• The sympathetic system increases heart rate and contractility, while the parasympathetic (vagal) system decreases both 3

Autonomic Triggers of Palpitations

Changes in autonomic tone directly precipitate palpitations through multiple mechanisms:

• Autonomic influences play an important role in the initiation of atrial fibrillation, with fluctuations in autonomic tone occurring prior to arrhythmia development 4
• The balance between sympathetic and vagal influences is as important as absolute sympathetic or parasympathetic tone as a predictor of arrhythmias 4
• Vagally mediated arrhythmias occur at night or after meals, while adrenergically induced arrhythmias typically occur during daytime in patients with organic heart disease 4

The Neurocardiology of Palpitation Perception

Palpitations represent a complex brain-heart axis phenomenon:

• Cardiac afferents provide beat-to-beat sensory information to the spinal cord, brainstem, and higher brain centers, with palpitations representing a pathway extending from the heart to the brain 5
• The right insula, cingulate gyrus, somatomotor and somatosensory cortices, nucleus accumbens, left subthalamic nucleus, and left ventral capsule/striatum are implicated in both palpitations and heartbeat detection 5
• The hypothalamus integrates visceral sensory information and generates coordinated patterns of autonomic responses to internal or social stressors 6
• Palpitations reflect an individual's cardioception awareness, which is modulated by body size, percentage of body fat, and psychological conditions 5

Clinical Classification by Autonomic Pattern

The ACC/AHA/ESC guidelines recognize distinct autonomic subtypes:

• Vagal predominance in the minutes preceding arrhythmia onset has been observed in some patients with structurally normal hearts, while in others there is a shift toward sympathetic predominance 4
• Changes in autonomic tone are listed as a specific etiology predisposing patients to atrial fibrillation, including both increased parasympathetic and increased sympathetic activity 4
• Vagal AF is characterized by occurrence at night, during rest, after eating, or after alcohol ingestion with antecedent progressive bradycardia 4
• Adrenergic AF has onset predominantly during daytime, provocation by exercise or emotional stress, and typically occurs at a specific sinus rate threshold 4

Therapeutic Implications

Treatment selection depends on identifying the dominant autonomic pattern:

• For AF of the adrenergic type, beta blockers are the initial treatment of choice 4
• In vagally mediated AF, adrenergic blocking drugs or digitalis sometimes worsen symptoms, and anticholinergic agents such as disopyramide are sometimes helpful to prevent recurrent AF 4
• Beta-blockers reduce heart rate and contractility by blocking sympathetic effects at cardiac beta-1 receptors 2
• Central alpha-2 agonists and transcranial repetitive magnetic stimulation should be considered for palpitations unrelated to cardiac arrhythmias or anxiety disorders 5

Important Clinical Caveats

Several pitfalls exist in evaluating autonomic-mediated palpitations:

• AF may be immediately recognized by sensation of palpitations or follow an asymptomatic period of unknown duration, with ambulatory ECG recordings revealing that individuals may experience periods of both symptomatic and asymptomatic AF 4
• The more marked the autonomic nervous system dependence of tachyarrhythmias, the less obvious its evidence—termed the "adrenergic paradox" 7
• In the presence of heart disease and heart failure, autonomic nervous system behavior is more difficult to assess than in the absence of structural heart disease, though its role remains crucial 7
• Classification of AF as either vagal or adrenergic form has only limited impact on management in most cases 4