A 58-year-old man is brought to the ED for a syncopal episode at dinner. His wife states that he was well until she found him suddenly slumping in the chair and losing consciousness for a minute. The patient recalls having some chest discomfort and shortness of breath prior to the episode. His rhythm strip, obtained by EMS, is shown below. Which of the following best describes these findings?
Mobitz type I
Mobitz type II
First-degree atrioventricular (AV) block
Atrial flutter with premature ventricular contractions (PVCs)
Sinus bradycardia
(Tintinalli, pp 148-149.) The rhythm strip shows second-degree AV block type II or Mobitz type II. Mobitz II presents with a prolonged PR interval (PR > 0.2 second) and random dropped beats (ie, P wave without QRS complex). The PR intervals are always the same duration. The block is below the level of the AV node, generally the His-Purkinje system. This heart block reflects serious cardiac pathology and may be seen with an anterior wall MI, which is the case with this patient.
Mobitz type I (a) (also called Wenckebach phenomenon) shows progressive prolongation of PR interval with each beat until AV conduction is lost causing a dropped beat. First-degree AV block (c) presents with prolonged PR interval (PR > 0.2 second) without loss of AV conduction. This block is asymptomatic. Atrial flutter (d) is a tachydysrhythmia with rapid atrial beat and variable AV block. It has a characteristic "sawtooth" appearance of atrial flutter waves. Sinus bradycardia (e) is similar to sinus rhythm except that the rate is less than 60 and generally greater than 45. There are several etiologies of sinus bradycardia; some are normal (eg, young person, well-trained athlete) and some pathologic (eg, β-blocker overdose, cardiac ischemia).