Chapter 15 - Bradyarrhythmias

Abstract

Bradyarrhythmias encompass a number of rhythm disturbances including sinus node dysfunction (SND) and atrioventricular block (AVB). Bradyarrhythmia may be asymptomatic and detected during routine electrocardiographic (ECG) examination or presented with dizziness, fatigue, syncope, presyncope, exercise intolerance, and poor concentration. Symptomatic SND is called sick sinus syndrome (SSS). ECG presentations of SND are sinus bradycardia, sinus pause or arrest, sinoatrial exit block, chronotropic incompetence, and tachy-brady syndrome. Symptom–rhythm correlation is highly important in SSS diagnosis. The initial clues to the diagnosis of SSS are most often gleaned from the patient's history, and the diagnosis is confirmed by a 12-lead surface ECG, ambulatory ECG recording, or exercise stress testing. In SND, treatment should be limited to those patients with a good symptom–rhythm correlation. Asymptomatic patients do not need any treatment. AVB is traditionally classified as first-, second-, or third-degree (complete) AV block. On the basis of intracardiac recordings, supra-, intra-, or infra-Hisian block can be differentiated. Diagnosis of AVB can be established in most cases noninvasively by the 12-lead ECG. In intermittent AVB, ambulatory ECG monitoring and exercise testing are important to establish a symptom–rhythm correlation. Except for asymptomatic first-degree AVB, type 1 second-degree AVB, and reversible types, other types of AVBs need a pacemaker, irrespective of associated symptoms.