From the Guidelines
Sick sinus syndrome is a disorder where the heart's natural pacemaker (sinus node) doesn't work properly, causing abnormal heart rhythms, and the most recent and highest quality study 1 suggests that it typically affects older adults and can present with symptoms like fatigue, dizziness, fainting, shortness of breath, and palpitations.
Definition and Causes
Sick sinus syndrome refers to a broad array of abnormalities in sinus node and atrial impulse formation and propagation, including persistent sinus bradycardia and chronotropic incompetence without identifiable causes, paroxysmal or persistent sinus arrest with replacement by subsidiary escape rhythms in the atrium, AV junction, or ventricular myocardium 1.
Clinical Manifestations
The clinical manifestations of sick sinus syndrome are diverse, reflecting the range of typical sinoatrial rhythm disturbances, and can include syncope, dyspnea on exertion caused by chronotropic incompetence, lightheadedness, and chronic fatigue 1.
Diagnosis and Treatment
The diagnosis of sick sinus syndrome is often accompanied by uncertainty that arises from incomplete linkage between sporadic symptoms and ECG evidence of coexisting bradycardia, and the decision to implant a pacemaker for sick sinus syndrome is crucial to distinguish between physiological bradycardia due to autonomic conditions or training effects and circumstantially inappropriate bradycardia that requires permanent cardiac pacing 1.
Key Points
- Sick sinus syndrome is a progressive condition related to age-associated fibrosis and degeneration of the heart's electrical system, particularly the sinus node tissue 1.
- The only effective treatment for symptomatic bradycardia is permanent cardiac pacing 1.
- Medications like beta-blockers or calcium channel blockers may need to be adjusted or discontinued as they can worsen the slow heart rate 1.
- Underlying conditions such as heart disease, high blood pressure, or electrolyte abnormalities should be addressed 1.
- Regular follow-up with a cardiologist is essential for monitoring and adjusting treatment as needed 1.
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, resulting in various arrhythmias, including bradyarrhythmias with or without accompanying tachyarrhythmias 2. It is a set of diseases with abnormal cardiac pacing, which manifests as diverse cardiac arrhythmias, especially bradycardia 3.
Causes of Sick Sinus Syndrome
The causes of sick sinus syndrome can be intrinsic or extrinsic. Intrinsic causes include degenerative fibrosis, ion channel dysfunction, and remodeling of the sinoatrial node 2. Extrinsic factors can be pharmacologic, metabolic, or autonomic 2. Age-related interstitial fibrosis is considered to be the common pathophysiological mechanism between sick sinus syndrome and atrial fibrillation 3.
Symptoms and Diagnosis
The symptoms of sick sinus syndrome are often subtle early on and become more obvious as the disease progresses, commonly related to end-organ hypoperfusion 2. Cerebral hypoperfusion is most common, with syncope or near-fainting occurring in about one-half of patients 2. Diagnosis may be challenging, and is ultimately made by electrocardiographic identification of the arrhythmia in conjunction with the presence of symptoms 2. Other diagnostic tools include inpatient telemetry monitoring, outpatient Holter monitoring, event monitoring, or loop monitoring 2.
Treatment Options
Treatment of sick sinus syndrome includes removing extrinsic factors, when possible, and pacemaker placement 2. Pacemakers do not reduce mortality, but they can decrease symptoms and improve quality of life 2. Pacemaker implantation is the first-line treatment for symptomatic patients with sick sinus syndrome and documented bradycardia history 3. Catheter ablation may also be used as an alternative second-line therapy for some patients with sick sinus syndrome and atrial fibrillation 3.
Key Features
- Sick sinus syndrome is a collection of disorders marked by the heart's inability to perform its pacemaking function 2
- It is a set of diseases with abnormal cardiac pacing, which manifests as diverse cardiac arrhythmias, especially bradycardia 3
- Intrinsic causes include degenerative fibrosis, ion channel dysfunction, and remodeling of the sinoatrial node 2
- Extrinsic factors can be pharmacologic, metabolic, or autonomic 2
- Symptoms are often subtle early on and become more obvious as the disease progresses, commonly related to end-organ hypoperfusion 2
- Diagnosis is ultimately made by electrocardiographic identification of the arrhythmia in conjunction with the presence of symptoms 2
- Treatment options include removing extrinsic factors, when possible, and pacemaker placement 2