A 67-Year-Old Man With Palpitations and Syncope

Nazem Akoum, MD, MS; Steven A. Lubitz, MD, MPH; Zachary D. Goldberger, MD, MSc, FACC

Disclosures

February 19, 2019

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Discussion

The patient's episodes are not suggestive of volume depletion or neurocardiogenic etiologies. Volume depletion typically causes positional symptoms, which were not present in this case. In the case of neurocardiogenic syncope, excessive vagal stimulation leads to significant bradycardia, vasodilatation, or both. Vagal stimulation is classically associated with triggers such as painful stimuli, which were notably absent in this case. Atypical triggers can be present. Of note, after an episode of neurocardiogenic syncope, a period of fatigue or feeing confused may follow, even for hours. The patient's history of Gilbert disease is unrelated to this presentation. Gilbert disease does not typically cause liver cirrhosis and the patient's symptoms are also not suggestive of advanced liver cirrhosis, transient ischemic attacks, or stroke. Therefore, the most likely diagnosis explaining this patient's symptoms is a cardiac arrhythmia.

Arrhythmic causes of syncope include both bradycardic (sinus node or atrioventricular conduction disease) and tachycardic (supraventricular or ventricular) etiologies. As the ambulatory cardiac monitoring suggests, the patient's symptoms of palpitations are due to tachycardia associated with atrial fibrillation (note the irregularly irregular rhythm that dominates most of the strip shown above), whereas his near syncope as well as recent history of true transient loss of consciousness and syncope are likely due to bradycardia and prolonged pauses observed upon termination of the paroxysms of atrial fibrillation.

The patient is manifesting classic findings of tachycardia-bradycardia, or "tachy-brady," syndrome, one of the common findings in sinus node dysfunction and a common cause of arrhythmia-related syncope. The tachycardia in this setting is usually due to atrial fibrillation or atrial flutter, and the bradycardia is due to a prolonged sinus node recovery following cessation of the tachyarrhythmia. In addition to tachy-brady syndrome, sinus node dysfunction also includes a broad spectrum of diagnoses, including symptomatic sinus bradycardia, chronotropic incompetence, sinoatrial exit block, and sinus arrhythmia.

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