This type of AV block is rare. The block occurs distal to the bundle of His (infra-His) and is a precursor of chronic complete AV block. Patients often experience syncope. Mobitz type II leads to serious complications if left untreated. Most patients are candidates for cardiac pacing. 

Second-degree AV block, Mobitz type II is characterized by an intermittent complete AV block of one or more atrial impulses. An escape beat or escape rhythm is often absent for one or more cycles, resulting in dropped beats. 

P waves occur at a regular rate. The PR interval is often normal with no increase in duration. Second-degree AV block is often accompanied by a bundle-branch block or a bilateral bifascicular block.

Second-degree AV block, Mobitz type II ECG ¹⁴

Related Video – ECG Rhythm Review – Second-Degree Heart Block (type 2)

Case 3

80-year-old man who slipped and sustained a hip fracture.

80-Year-Old Man Hip Fracture ECG ¹⁵

Case 4

60-year-old woman with COPD, coronary artery disease, bladder cancer, hyperkalemia, diabetes mellitus, and hypothyroidism.

60-Year-Old Woman With COPD ECG ¹⁶

Case 3 is an ECG taken from a 60-year-old female patient with COPD, coronary artery disease, and bladder cancer who presented to the ED with altered mental status, hypotension, hypoxia, and bradycardia. 

The orange arrows in figure 4 point out the regular atrial rhythm. The atrial rhythm has a rate of 100 bpm. The presence of a PR interval prior to the QRS complex makes the ECG diagnosis of second-degree AV block, Mobitz II.

Second-degree AV block may be confounded by certain clinical situations, such as in postoperative patients with a decreased heart rate secondary to vagal stimulation.