case_images: PMC10031013_01
case_images: Eighteen-channel surface ECG. ECG on admission showed transient loss of ventricular pacing capture.
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case_images: F1
case_images: ECG (Figure 1) showed a transient loss of ventricular pacing capture.
case_images: Pacing test. Testing showed stable impedance and sensing in the atria and ventricle, with no ventricular sensing data after October 2021 (A). There was a clear increase in the ventricular capture threshold in early January 2022 (red arrows) and this gradually decreased to normal after 1 month of anticoagulant therapy (green arrows) (B).
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case_images: F2
case_images: Pacemaker testing revealed both stable impedance and stable sensing in the atria and ventricles (Figure 2A) and a normal atrial output threshold (0.5 to 0.75 volts under a 0.4-ms pulse width) but a clear increase in ventricular capture threshold at outputs 2 months previously (Figure 2B).
case_images: Chest x-ray. X-ray after the first pacemaker operation on September 12, 2019 (A) and on February 16, 2022 (B). This showed correct lead position on admission.
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case_images: F3
case_images: However, an anteroposterior chest x-ray showed correct atrial and ventricular pacing lead positions (Figures 3A, B).
case_images: PMC10031013_02
case_images: CT scan of the pulmonary artery. (A) CTA on admission showed pulmonary embolism (PE) in the right lower pulmonary arterial branch. Perfusion defects are identified by yellow arrows. (B) CTA was normal after 1 month of anticoagulant therapy. (C, D) show the positions of the RV and atrial leads (blue arrows) on PA view on admission (C) and 1 month later (D).
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case_images: F4
case_images: Therefore, a computerized tomography (CT) scan of the pulmonary artery was performed in view of the presenting symptoms; this showed PE in the right lower pulmonary arterial branch (Figure 4A). After 1 month, the ventricular capture threshold gradually fell back to the normal range; a reexamination CT scan of the pulmonary artery indicated no evidence of PE (Figure 4B), and arterial oxygen pressure (PaO2 82 mmHg) and D-dimer levels (0.2 mg/L) were normal. Figures 4C, D depict the positions of the right ventricular and atrial leads, respectively, from a posteroanterior view, at the time of admission and 1 month later.