Response to ECG, February 2017
a Servicio de Cardiología, Complejo Hospital Juan Ramón Jiménez, Huelva, Spain
The correct answer is number 4. This dual-chamber pacemaker is functioning normally. There are 2 leads, 1 for pacing the Bachmann interatrial bundle and the other for pacing the bundle of His. The resulting bipolar physiological Hisian pacing does not lead to any changes in QRS morphology (Figure 1).
Given the particular features of pacing in this case, there is no loss of capture (answers 1 and 2) because all the spikes are still present in the QRS complex. Twiddler syndrome (answer 3) is ruled out by chest x-ray (Figure 2).
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