Atrioventricular Block Clinical Presentation
- Author: Chirag M Sandesara, MD, FACC; Chief Editor: Jeffrey N Rottman, MD more...
History
First-degree atrioventricular (AV) block is generally not associated with any symptoms and is usually an incidental finding on electrocardiography (ECG). People with newly diagnosed first-degree AV block may be healthy individuals with high vagal tone (eg, well-conditioned athletes), or they may have a history of myocardial infarction or myocarditis. First-degree AV block also may represent the first sign of a degenerative process of the AV conduction system.
Second-degree AV block usually is asymptomatic. However, in some patients, sensed irregularities of the heartbeat, presyncope, or syncope may occur. The latter usually is observed in more advanced conduction disturbances, such as Mobitz II second-degree AV block. A history of medications that affect atrioventricular node (AVN) function (eg, digitalis, beta-blockers, and calcium channel blockers) may be contributory and should be obtained.
Third-degree AV block frequently is associated with symptoms such as fatigue, dizziness, lightheadedness, presyncope, and syncope most commonly. Syncopal episodes due to slow heart rates are called Morgagni-Adams-Stokes (MAS) episodes, in recognition of the pioneering work of these researchers on syncope. Patients with third-degree AV block may have associated symptoms of acute myocardial infarction either causing the block or related to reduced cardiac output from bradycardia in the setting of advanced atherosclerotic coronary artery disease.
Any level of atrioventricular block leading to profound bradycardia may also lead to life-threatening torsades de pointes.
Physical Examination
Routine physical examination does not lead to the diagnosis of first-degree AV block. Second-degree AV block may manifest on physical examination as bradycardia (especially Mobitz II), irregularity of heart rate (especially Mobitz I [Wenckebach]), or both.
Third-degree AV block is associated with profound bradycardia unless the site of the block is located in the proximal portion of the AVN. Exacerbation of ischemic heart disease or congestive heart failure caused by AV block–related bradycardia and reduced cardiac output may lead to specific clinically recognizable symptoms (eg, chest pain, dyspnea, confusion, and pulmonary edema). Cannon a waves may be observed intermittently in the jugular venous pulsation when the right atrium contracts against a closed tricuspid valve due to atrioventricular dissociation.
Complications
Complications include the following:
- Sudden death due to asystole or secondary to polymorphic ventricular tachyarrhythmias
- Cardiovascular collapse with syncope, aggravation of ischemic heart disease, congestive heart failure, and exacerbation of renal disease
- Head and musculoskeletal injuries during syncopal episodes
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