Sick sinus syndrome: Clinical manifestations, diagnosis, and evaluation
- Munther K Homoud, MD
Munther K Homoud, MD
- Associate Professor of Medicine
- Tufts University School of Medicine
Sick sinus syndrome (SSS) is characterized by dysfunction of the sinoatrial (SA) node that is often secondary to senescence of the SA node and surrounding atrial myocardium. Patients with SSS are typically symptomatic with fatigue, lightheadedness, palpitations, presyncope, and/or syncope, although the occasional patient may be identified during electrocardiography (ECG) or ambulatory ECG monitoring performed for another indication.
The clinical manifestations, evaluation, and approach to diagnosis of SSS will be reviewed here. The causes, natural history, and management of SSS, along with the appropriate timing of referral to a specialist, are discussed in detail separately. (See "Sick sinus syndrome: Epidemiology, etiology, and natural history" and "Sick sinus syndrome: Treatment" and "Arrhythmia management for the primary care clinician", section on 'Referral to a specialist'.)
Sick sinus syndrome is a clinical syndrome characterized by chronic sinoatrial (SA) node dysfunction, a sluggish or absent SA nodal pacemaker after electrical cardioversion, and/or depressed escape pacemakers in the presence or absence of atrioventricular (AV) nodal conduction disturbances [1-3]. SSS may also manifest as chronotropic incompetence with inappropriate heart rate responses to physiological demands during activity. SSS can also be accompanied by AV nodal conduction disturbances and by atrial tachyarrhythmias as part of the tachycardia-bradycardia syndrome. (See "Sick sinus syndrome: Epidemiology, etiology, and natural history", section on 'Definition of SSS'.)
Sick sinus syndrome (SSS) is defined by electrocardiogram (ECG) abnormalities (eg, bradycardia, sinus pauses, sinus arrest) that occur in association with clinical signs and symptoms. Most patients with SSS present with one or more of the following nonspecific symptoms: fatigue, lightheadedness, palpitations, presyncope, syncope, dyspnea on exertion, or chest discomfort. Symptoms are frequently intermittent with gradual progression in frequency and severity, although some patients may present with profound, persistent symptoms at the initial visit. Rarely, SSS may be asymptomatic and identified on routine ECG or ambulatory ECG monitoring.
Symptoms — Patients with symptomatic SSS are primarily older and frequently have comorbid diseases. Patients with SSS often seek medical attention with symptoms of lightheadedness, presyncope, syncope, and, in patients with alternating periods of bradycardia and tachycardia, palpitations and/or other symptoms associated with a rapid heart rate. Patients with coexisting cardiac pathology may notice increasing dyspnea on exertion or worsening chest discomfort related to lower heart rate and the resulting reduction in cardiac output. Because symptoms may be variable in nature, nonspecific, and frequently transient, it may be challenging at times to establish this symptom-rhythm relationship.
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- CLINICAL PRESENTATION
- ECG findings
- APPROACH TO THE DIAGNOSIS
- DIAGNOSTIC TESTING
- Ambulatory ECG monitoring and event recording
- Pharmacologic challenge
- Calculating the intrinsic heart rate
- Electrophysiologic testing
- DIFFERENTIAL DIAGNOSIS
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS