Bradyarrhythmias

Bradyarrhythmias arise from (1) failure of impulse initiation (sinoatrial node dysfunction) or (2) impaired electrical conduction (e.g., AV conduction blocks).



SINOATRIAL (SA) NODE DYSFUNCTION 

Etiologies are either intrinsic [degenerative, ischemic, inflammatory, infiltrative (e.g., senile amyloid), or rare mutations in sodium channel or pacemaker current genes] or extrinsic [e.g., drugs (beta blockers, Ca++ channel blockers, digoxin), autonomic dysfunction, hypothyroidism]. Symptoms are due to bradycardia (fatigue, weakness, lightheadedness, syncope) and/or episodes of associated tachycardia (e.g., rapid palpitations, angina) in pts with sick sinus syndrome (SSS).

Diagnosis 

Examine ECG for evidence of sinus bradycardia (sinus rhythm at <60 beats/ min) or failure of rate to increase with exercise, sinus pauses, or exit block. In pts with SSS, periods of tachycardia (i.e., atrial fibrillation/flutter) occur. Prolonged ECG monitoring (24-h Holter or 30-day loop event monitor) aids in identi fying these abnormalities. Invasive electrophysiologic testing is rarely necessary to establish diagnosis.

Sinoatrial Node Dysfunction TREATMENT

Remove or treat extrinsic causes such as contributing drugs or hypothyroidism. Otherwise, symptoms of bradycardia respond to permanent pacemaker placement. In SSS, treat associated atrial fibrillation or flutter .