The patient was a 53-year-old woman with congenital heart disease consisting of partial atrioventricular septal defect, corrected in infancy. In light of severe symptomatic mitral valve regurgitation, the mitral valve was replaced with a mechanical prosthetic valve. During the postoperative period, complete atrioventricular block occurred. As this persisted 6 days after the intervention, it was decided to implant a dual-chamber pacemaker, initially programmed in DDDR mode at a minimum frequency of 60 bpm.

Immediately after implantation, the Arrhythmias Unit was alerted due to a paced rhythm at 45 bpm, with the following ECG recorded (figure 1).

Figure 1

(0.19MB).

What do you think was the most likely diagnosis?

• 1.

  T-wave oversensing

• 2.

  Switch to DDI mode due to detection of atrial tachyarrhythmia

• 3.

  Wenckebach behavior on exceeding the maximum tracking rate

• 4.

  Sinus tachycardia with 2:1 ventricular pacing due to atrial sensing during the postventricular atrial refractory period

Submit your answer to http://www.revespcardiol.org/es/electroreto/73/04. The answer will be published in the next issue (May 2020). #RetoECG.