Emergency Medical Services Agency

This ECG demonstrates a 2^nd degree AV block, Mobitz Type II. There is a non-conducting p-wave every other beat indicating 2:1 conduction.

The nonconducting p-waves are shown under the arrows in this image.  Notice that the interval between each p-wave is constant but no QRS follows the p-wave every other beat.

Mobitz II heart blocks are more common with patients with structural damage to the heart resulting in failure of conduction below the AV node. In a Mobitz II heart block, the His-Purkinje cells fail to conduct the supraventricular impulse generated from the AV node.  Patients with Mobitz II AV blocks are often symptomatic. Mobitz II heart blocks can degenerate to a 3^rd degree heart block.

This patient should be managed in accordance with TP 1212, Cardiac Dysrhythmia – Bradycardia. Since the patient shows signs of poor perfusion – weakness, pallor, and hypotension – you initiate treatment with Atropine 1mg (10mL) IV push.  If the HR was ≤40 for this patient,  if paramedics were unable to establish an IV, or if the patient did not respond to atropine, paramedics would be advised to proceed immediately to transcutaneous pacing (TCP) and should consider midazolam for sedation and/or fentanyl or morphine for analgesia. If the initial hypotension discourages sedation or pain medication administration, these can be initiated as the blood pressure improves.

Prior to establishing IV access, the patient became more bradycardic, with HR 38, continued weakness and worsening blood pressure.  Transcutaneous pacing is initiated en route to the MAR. A transvenous pacer is placed in the emergency department and the patient is admitted to the hospital for pacemaker placement.

• A Mobitz II AV block is a 2nd degree AV block in which there are intermittent non-conducted P waves without progressive prolongation of the PR interval
• Patients with Mobitz II AV blocks are often symptomatic and can degenerate to a 3rd degree heart block
• Patients with symptomatic bradycardia and evidence of poor perfusion should be treated with Atropine or with TCP if heart rate ≤40, unable to establish IV, or no improvement with atropine.