From the Guidelines
Sick sinus syndrome is a disorder where the heart's natural pacemaker (sinus node) doesn't function properly, causing abnormally slow heart rates, pauses in the heart rhythm, or alternating slow and fast rhythms, and the definitive management for most patients with symptomatic sick sinus syndrome involves implanting a permanent pacemaker to regulate the heart rate. The condition occurs because of degenerative fibrosis of the sinus node tissue, often related to aging, though it can also result from coronary artery disease, inflammatory conditions, or infiltrative diseases [ 1 ]. Symptoms include fatigue, dizziness, syncope, shortness of breath, and palpitations, but some patients may be asymptomatic despite significant bradycardia.
Diagnosis and Treatment
The diagnosis of sick sinus syndrome is based on the correlation of symptoms with the specific arrhythmias, which may be difficult due to the intermittent nature of the episodes [ 1 ]. Treatment typically involves implanting a permanent pacemaker to regulate the heart rate. Before pacemaker implantation, medications like atropine may be used temporarily for bradycardia in emergency situations. If the patient has associated atrial fibrillation, anticoagulation with warfarin or direct oral anticoagulants (DOACs) like apixaban or rivaroxaban is often necessary to prevent stroke [ 1 ]. Patients should avoid medications that can worsen bradycardia, such as beta-blockers, calcium channel blockers, and certain antiarrhythmics.
Pacemaker Therapy
Cardiac pacemaker therapy is indicated and has proved highly effective in patients with sinus node dysfunction when bradyarrhythmia has been demonstrated to account for syncope [ 1 ]. Permanent pacing frequently relieves symptoms but may not affect survival. Atrial-based pacing (AAI or DDD) is recommended as an alternative to conventional DDDR (dual chamber rate-adaptive pacemaker) pacing in patients essentially needing atrial support [ 1 ]. Physiological pacing (atrial or dual-chamber) has been definitely shown to be superior to VVI pacing, as it lowers the risk of developing atrial fibrillation and improves quality of life [ 1 ].
Follow-up and Management
Regular cardiac follow-up is essential after diagnosis, even with a pacemaker in place. The management of sick sinus syndrome should focus on relieving symptoms, preventing syncope, and improving quality of life. Elimination of offending agents that can exacerbate or unmask underlying susceptibility to bradycardia is an important element in preventing syncope recurrence [ 1 ]. Percutaneous cardiac ablative techniques for atrial tachyarrhythmia control may be considered in selected patients with the bradycardia-tachycardia form of sick sinus syndrome [ 1 ].
From the Research
Diagnosis of Sick Sinus Syndrome (SSS)
- The diagnosis of SSS is made by electrocardiographic identification of the arrhythmia in conjunction with the presence of symptoms 2, 3
- Electrocardiography (ECG) shows severe sinus bradycardia, sinus arrest, or sinoatrial block 2
- Continuous electrocardiographic monitoring, exercise testing, and electrophysiologic investigations may be useful in detecting transient or latent sinus-node abnormalities 2
- Inpatient telemetry monitoring, outpatient Holter monitoring, event monitoring, or loop monitoring may be used if ECG does not yield a diagnosis 3
Treatment of Sick Sinus Syndrome (SSS)
- Treatment should be aimed at controlling morbidity and relieving symptoms 2
- Cardiac pacing is the most powerful therapy, with physiologic pacing (atrial or dual-chamber) shown to be superior to ventricular pacing 4, 2
- Dual-chamber pacemaker therapy is associated with a lower incidence of heart failure and syncope compared to no treatment or oral theophylline 5
- Single-lead atrial pacing (AAIR) is associated with a higher incidence of paroxysmal atrial fibrillation and a two-fold increased risk of pacemaker reoperation compared to dual-chamber pacing (DDDR) 4
- Beta blockers like pindolol may be used to prevent supraventricular arrhythmias, systemic hypertension, and myocardial ischemia, with less sinus node depression compared to propranolol 6
- Removing extrinsic factors, when possible, is also an important part of treatment 3