Sinus Node Dysfunction Differential Diagnoses

Updated: Nov 30, 2018
  • Author: Bharat K Kantharia, MD, FRCP, FAHA, FACC, FESC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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Diagnostic Considerations

Conditions to consider in the differential diagnosis of sinus node dysfunction (SND) include the following:

  • Carotid sinus hypersensitivity

  • Neurocardiogenic syncope with a predominant cardioinhibitory component

  • Physiologic normal bradycardia, especially among highly conditioned athletes

Clinical approach to the diagnosis

There are no standardized criteria for establishing a diagnosis of SND, and the initial clues to the diagnosis are most often gleaned from the patient’s history. However, the symptoms of SND are nonspecific and the electrocardiographic (ECG) findings may not be diagnostic. Hence, the key to making a diagnosis of SND is to establish a correlation between the patient's symptoms and the underlying rhythm at the time of the symptoms.

Patients may present with symptoms of fatigue, lightheadedness, presyncope, syncope, dyspnea on exertion, chest discomfort, and/or palpitations. A routine ECG and/or ambulatory ECG monitoring may confirm the diagnosis if typical ECG findings (eg, one or more periods of sinus bradycardia; sinus pause, arrest, and sinoatrial [SA] exit block; or alternating bradycardia and atrial tachyarrhythmias) can be correlated with the symptoms. In some patients, however, additional diagnostic testing may be required, and SND should not be diagnosed until any potentially reversible causes have been identified and treated.

Following a comprehensive history and physical examination, a resting 12-lead ECG, review of previous medical records and ECG tracings, and exercise stress testing are the keys to making a diagnosis of SND and establishing a symptom-rhythm correlation. A detailed history and ECG findings during symptoms are often sufficient to diagnose SND. Careful review of prior records, in particular previous ECG tracings, can provide subtle clues to changes in the ECG over time. For patients with clinically suspected SND in whom the diagnosis remains uncertain following the initial ECG, exercise stress testing is advised.

Carefully evaluate for potentially reversible causes and medication use to exclude remediable etiologies for apparent SND. In patients with medication use (eg, beta blockers, calcium channel blockers, digoxin, antiarrhythmics, and acetylcholine esterase inhibitors) suspected to result in symptomatic bradycardia, the patient should remain on an ECG monitor while the medications are withdrawn. If symptoms and ECG abnormalities persist following the withdrawal of the medications (ie, after 3-5 half-lives), then SND/sick sinus syndrome (SSS) may be diagnosed. 

If the diagnosis of SND cannot be definitively diagnosed following a thorough history and physical examination, an initial 12-lead ECG, and/or an ambulatory ECG monitoring [Holter] for 1 to 14 days, perform an event monitor for up to 4 weeks to identify symptomatic episodes of arrhythmias and to monitor average heart rates over extended periods of surveillance.

Differential Diagnoses