The fundamental basis of palpitations: a neurocardiology approach.

BACKGROUND AND OBJECTIVE Palpitations are a common symptom that may indicate cardiac arrhythmias, be a somatic complaint in anxiety disorders, and can be present in patients without either condition. The objective of this review was to explore the pathways and fundamental mechanisms through which individuals appreciate palpitations. OBSERVATIONS Cardiac afferents provide beat-to-beat sensory information on the heart to the spinal cord, brain stem, and higher brain centers. Cardioception, a subset of interoception ('the physiological sense of the condition of the body'), refers to sensing of the heartbeat. High cardioception is present in persons with lower body mass index, lower percentages of body fat, and anxiety disorders. Low cardioception (lower interoceptive awareness) is associated with psychiatric disorders, such as depression, personality disorders, and schizophrenia. CNS sites associated with heartbeat detection have been identified by functional magnetic resonance imaging studies and heartbeat-evoked electroencephalogram potentials. 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. Involvement of the brain as a primary modulator of palpitations rests on the data that various areas of the brain are activated in association with cardioception, the ability of focal brain stimulation to induce palpitations, the ability of central alpha receptor agonists and antagonists to modulate palpitations, and suppression of palpitations by transcranial repetitive magnetic stimulation (rTMS). CONCLUSIONS Palpitations should be viewed as a pathway extending from the heart to the brain. Palpitations are, in part, a reflection of an individual's cardioception awareness, which is modulated by body size, percentage of body fat, and psychological or psychiatric conditions. Palpitations can originate in the brain and involve central neurotransmitters. Treatment of palpitations unrelated to cardiac arrhythmias or anxiety disorders should consider the use of central alpha-2 agonists and possibly rTMS.