Exit Block Around a Junctional Pacemaker

Recurrent loss of pacemaker capture following premature ventricular contractions

“…Local pacemaker exit block occurs when capture of myocardium immediately at the cathode fails to conduct to the surrounding myocardium, and may be divided into 2 types: “type 1,” in which there is a progressive delay in conduction prior to loss of capture, and “type 2” in which loss of capture occurs without warning. 7 To date, the literature has only described nearby myocardial fibrosis and inflammation as etiologies of local pacemaker exit block. 4 This novel case elucidates a unique etiology of pacemaker exit block—PVCs.…”

Atrioventricular junctional tachycardia with exit block in an adolescent

“…Exit block is described as type I, or Wenckebach, with a progressive delay in conduction that is apparent by grouped beating or a decreasing P-P (atrial) or R-R (junctional or ventricular) interval before the blocked beat; or type II, which is characterized by a blocked beat that occurs in the absence of preliminary signs with a length that is a multiple of the basic interval. ECG diagnosis of an exit block is based on intermittent P-P interval prolongation in multiples (doubling, tripling, etc) of the normal P-P interval 7 …”

“…Few cases have strong parallels to our particular case presentation. One report described at 72-year-old previously healthy man with complete AV block and AV junctional tachycardia with exit block 7 . Another report described a 52-year-old previously healthy man with a negative workup who in the absence of digoxin demonstrated on His-bundle electrogram a junctional ectopic rhythm with exit block that blocked the sinus P wave.…”