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Table 39.3

Differential Diagnosis of Bradycardia and AV Block

DiagnosisECG features
Sinus bradycardia

Constant PR interval <200ms

QRS regular

Junctional bradycardiaP wave absent or position constant either after, immediately before or hidden in the QRS complex
First-degree AV blockConstant PR interval >200ms
Second-degree AV block, Mobitz type 1Progressively lengthening PR interval followed by dropped beat
Second-degree AV block, Mobitz type 2Constant PR interval with dropped beats
Third-degree (complete) AV blockRelationship of P wave to QRS varies randomly

AV, atrioventricular.