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Vol. 69. Issue 12.
Pages 1218 (December 2016)
Vol. 69. Issue 12.
Pages 1218 (December 2016)
ECG Contest
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Response to ECG, November 2016
Respuesta al ECG de noviembre de 2016
Ricardo Salgado Aranda
Corresponding author

Corresponding author:
, Francisco Javier García Fernández, Francisco Javier Martín González
Unidad de Arritmias, Hospital Universitario de Burgos, Burgos, Spain
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Rev Esp Cardiol. 2016;69:110110.1016/j.rec.2016.05.034
Ricardo Salgado Aranda, Francisco Javier García Fernández, Francisco Javier Martín González
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This is a case of a real malfunction due to a defect in ventricular sensing (option 3, correct). During the sensing tests, the reference for sensitivity utilized by the pacemaker was the R wave of the premature ventricular contractions, which is approximately 13mV (Figure 1). According to the nominal settings of this pacemaker model, the sensing threshold is established automatically in 50% of the mean R wave sensed (approximately 6.5mV). The conducted native ventricular electrogram has a voltage<6mV and thus is undersensed (arrows). For this reason, a sensing defect is produced despite the normal parameters found on the interrogation of the device (option 1, incorrect).

Figure 1

Although the tracing may initially indicate that fusion beats are being produced, the ventricular spike appears very late with respect to the initiation of QRS, a circumstance that impedes capture of the pace and the fusion (option 2, incorrect).

As this is a case of sensing failure, increasing the ventricular pulse amplitude would not modify this situation (option 4, incorrect). The device was reprogrammed, the automatic sensing threshold was deactivated, and a fixed threshold of 2.5mV was established. With this adjustment, the pacemaker correctly sensed all the ventricular electrograms (Figure 2).

Figure 2
Copyright © 2016. Sociedad Española de Cardiología
Revista Española de Cardiología (English Edition)

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