double counting of the R wave from ventricular extrasystole

Tracing
N° 3
Manufacturer Biotronik Device Remote monitoring Field Periodic Egm
Patient

This 54-year-old man underwent implantation of a Lumax 540 HF-T triple chamber defibrillator in the context of ischemic cardiomyopathy with left bundle branch block; periodical EGM; 

Graph and trace

Telecardiology tracing

The 4 available channels are the markers with the time intervals, the atrial sensing channel, and the right and left ventricular sensing channels, each for 30 seconds.

  1. sinus rhythm with biventricular stimulation;
  2. ventricular pair;
  3. VES, probably originating from the right ventricle, sensed first in the right then in the left ventricular channel;
  4. VES with oversensing in the right ventricular channel of a supernumerary ventricular electrogram, corresponding to the double counting of the R wave at the end of the ventricular blanking period;
  5. further VES oversensing.
Comments

This patient had to be seen in a face-to-face consultation to resolve several issues. The main one was the double counting of the R wave, limited to some VES of right ventricular origin. Should ventricular tachycardia develop, the risks associated with double counting were: 1) erroneous classification of tachycardia at 300 bpm (in the VF zone) instead of 150 bpm; 2) unnecessarily forceful therapies, such as electrical shocks instead of anti-tachycardia pacing. As in the case of the previous patient, the programming of the blanking period (80 ms) was probably too short, and a lengthening of the programmed value to 110 ms resolved the issue.

Ventriculo-atrial crosstalk requires a lengthening of the post-ventricular stimulation atrial blanking period to prevent possible erroneous diagnoses of atrial arrhythmias with mode switch to DDI pacing, which might cause a loss of biventricular resynchronization as long as the device is in mode switch.

From a clinical perspective, the VES were frequent at the time of the recording of the periodic EGM. A careful surveillance of their occurrence on the successive reports of telecardiology, and an understanding of their clinical consequences was in order. If frequent, a search for a metabolic abnormality and a surveillance of the evolution of left ventricular function were required in this patient suffering from heart failure.

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