From the Guidelines
Sick sinus syndrome is a disorder where the heart's natural pacemaker, the sinoatrial (SA) node, malfunctions and fails to generate or conduct electrical impulses properly, typically causing abnormally slow heart rates, pauses in the heart rhythm, or alternating episodes of fast and slow heart rates. This condition occurs most commonly in older adults due to age-related fibrosis and degeneration of the SA node tissue, though it can also result from heart disease, medications, or prior cardiac surgery 1. Patients may experience symptoms like fatigue, dizziness, fainting, shortness of breath, chest pain, or palpitations, though some remain asymptomatic. Diagnosis involves electrocardiogram (ECG) monitoring to capture the abnormal rhythms, often requiring extended monitoring with Holter monitors or event recorders. Some key points to consider in the diagnosis and management of sick sinus syndrome include:
- The clinical manifestations of SND are diverse, reflecting the range of typical sinoatrial rhythm disturbances, with the most dramatic presentation being syncope 1.
- The natural history of untreated SND may be highly variable, with the majority of patients who have experienced syncope due to a sinus pause or marked sinus bradycardia likely to have recurrent syncope 1.
- The only effective treatment for symptomatic bradycardia is permanent cardiac pacing, with the decision to implant a pacemaker for SND often accompanied by uncertainty that arises from incomplete linkage between sporadic symptoms and ECG evidence of coexisting bradycardia 1.
- Management may also include adjusting or discontinuing medications that slow heart rate, such as beta-blockers, calcium channel blockers, or digoxin 1.
- Correlation between symptoms and bradycardia is considered to be the “gold standard” of diagnosis, although it may be difficult to establish this correlation in some cases due to the presence of competing etiologies of symptoms or limitations in monitoring 1. The condition is significant because if left untreated, it can lead to serious complications including heart failure, stroke, or sudden cardiac death, emphasizing the importance of prompt diagnosis and treatment. In terms of treatment, the most recent guidelines recommend implantation of a permanent pacemaker to regulate the heart rhythm, especially for symptomatic patients 1. Overall, sick sinus syndrome is a complex condition that requires careful diagnosis and management to prevent serious complications and improve patient outcomes.
From the Research
Definition of Sick Sinus Syndrome
Sick sinus syndrome refers to a collection of disorders marked by the heart's inability to perform its pacemaking function, predominantly affecting older adults 2. It comprises various arrhythmias, including bradyarrhythmias with or without accompanying tachyarrhythmias. The term sick sinus syndrome should be reserved for patients with symptomatic sinus-node dysfunction 3.
Key Characteristics
- Sick sinus syndrome results from intrinsic causes, such as degenerative fibrosis, ion channel dysfunction, and remodeling of the sinoatrial node, or may be exacerbated or mimicked by extrinsic factors 2.
- At least 50 percent of patients with sick sinus syndrome develop alternating bradycardia and tachycardia, also known as tachy-brady syndrome 2.
- Symptoms are often subtle early on and become more obvious as the disease progresses, commonly related to end-organ hypoperfusion, with cerebral hypoperfusion being the most common 2.
- Syncope or near-fainting occurs in about one-half of patients 2.
Diagnosis and Treatment
- Diagnosis may be challenging and is ultimately made by electrocardiographic identification of the arrhythmia in conjunction with the presence of symptoms 2.
- Treatment of sick sinus syndrome includes removing extrinsic factors, when possible, and pacemaker placement 2.
- Cardiac pacing is the most powerful therapy, with physiologic pacing (atrial or dual-chamber) shown to be superior to ventricular pacing 3.