PMC10244670_01
(A) VVI pacing led to repetitive VA retrograde conduction and the subsequent atrial activation conducted to capture the ventricle. The bigeminy led to short-long cycles and resulted in multiple Torsade de Pointes (TdP) shown in (B and C). (D) The EGM recorded the onset of one episode of the TdP, indicating the sequential relationship between the bigeminy and the malignant arrhythmia.
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F1
However, telemetric ECG monitoring and EGM demonstrated Torsade de Pointes induced by the bigeminy result from repetitive retrograde ventriculoatrial (VA) activation in VVI pacing and sequential atrial impulses conducted to the ventricles through intact conduction systems (Figure 1).
(A) Baseline 12-lead ECG of the patient before the single-chamber pacemaker implantation showed significant sinus bradycardia, junctional escape rhythm, and long QTc of 543 ms. (B) Replacement for a dual-chamber implantable cardiac defibrillator and intentionally higher atrial base rate of 70 bpm resulted in eliminating VA retrograde conduction and shortened QTc of 483 ms.
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F2
In the scenario of previously unidentified LQTs (Figure 2A), the bigeminy pattern created short-long cycles which contributed to the malignant arrhythmia attacks. Also, the higher base rate of 70 bpm helps to shorten the QTc (Figure 2B).