Pacemaker ventricular block

Pacemaker ventricular block

First degree, second degree and third degree block can occur at the lead – myocardial interface. It is also known as pacemaker exit block.  Pacemaker exit block can be due to fibrosis as a result of local tissue reaction. Steroid eluting leads reduce the local tissue reaction and prevent increase in pacing threshold which can occur due to fibrosis.

First degree pacemaker exit block is manifested as a delay between the pacing artifact and the QRS complex. In second degree pacemaker exit block, the interval progressively increases culminating in a non capture. In third degree pacemaker exit block there is total loss of capture [1]. This can occur in either terminal illness or severe hyperkalemia [2].

The delay between the pacemaker spike and the depolarization of the chamber is also known as latency. Normal latency for right ventricular endocardial pacing is less than 40 milliseconds. ECG of first degree pacemaker exit block at the atrial level has also been reported [3].

Reference

  1. Kistler PM, Mond HG, Vohra JK. Pacemaker ventricular block. Pacing Clin Electrophysiol. 2003 Oct;26(10):1997-9.
  2. Barold SS, Herweg B. The effect of hyperkalaemia on cardiac rhythm devices. Europace. 2014 Apr;16(4):467-76.
  3. Johnson Francis. First degree pacemaker exit block. BMH Med. J. 2016;3(4):113-114.