PMC10192706_01
Twelve-lead ECG of case 1 taken at 10 mm/mV and 25 mm/s. (A) Sinus arrest and AV junctional rhythm at a rate of 42 beats per minute with a QRS of 140 ms and bifascicular block, with no evidence of atrial activity. (B) 2.3 s pause during sinus arrest. (C) Post-procedure chest x-ray. (D) 12-lead ECG with nonselective left bundle branch stimulation. ECG, electrocardiogram.
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F1
Electrocardiogram (ECG) documented sinus arrest, with pauses of up to 2.3 s and junctional0 rhythm at 37 bpm with hemodynamic compromise requiring temporary PM placement (Figures 1A, B). The final ECG showed a narrower QRS with a right bundle branch image compared to the baseline QRS (from 140 to 115 ms) with the same axis as the intrinsic rhythm (Figure 1D).
PMC10192706_02
(A) 12-lead ECG of case 2 taken at 10 mm/mV and 25 mm/s. Complete AV block with normal axes. The mean atrial rate is 70 bpm, and the mean ventricular rate is 40 bpm. (B) 12-lead ECG taken at 10 mm/mV and 25 mm/s. Unipolar dual-chamber pacing with heart rate at 63 bpm, normal P-wave, and QRS axes. After ventricular stimulation, an immediate onset of the QRS with pseudodelta (black arrow) is observed, which was measured at 90 ms at II, III, aVF, and V6. (C) Venography shows an absent connection of the brachiocephalic vein and a direct connection of the left venous system to the coronary sinus. The final position of the leads in (D) anteroposterior view, (E) right oblique 30 , and (F) left oblique 30  are shown. ECG, electrocardiogram; AV, atrioventricular.
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F2
The final ECG showed a QRS of 90 ms when measured in II, III, aVF, and V6, with a pseudodelta wave and a normal axis (Figure 2B).
(A) Initial 12-lead ECG of case 3 taken at 10 mm/mV and 25 mm/s. PM rhythm with single-chamber pacing. AV dissociation (black arrows point to P waves) with a mean atrial rate of 90 bpm, QRS of 160 ms with inferior and right axis, and late transition. (B) QRS notch progression during the first three turns observed in multiple surface ECG leads (arrows point to V1) during advancement of the ventricular electrode through the interventricular septum. (C) QRS notch progression during the last two turns was observed in V2 during the advancement of the ventricular electrode through the interventricular septum. (D) Dual-chamber pacing in the final position of the ventricular electrode with right bundle branch image. (E) Selective stimulation of the left bundle branch of His. Final ECG with normal P-wave and QRS axes, 80 ms final QRS with right bundle branch image, and late transition. (F) Final position of pacemaker, atrial and ventricular endocardial leads. As it can be seen, the epicardial leads were placed in an unusual position, near the AV junction. ECG, electrocardiogram; AV, atrioventricular.
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F3
The admission ECG showed PM rhythm with single-chamber stimulation and atrioventricular dissociation (Figure 3A). Two more turns were given to the electrode without presenting ventricular extrasystoles with right bundle branch morphology and observing notch displacement in V1 and V2 to the right, finally showing in V1 and V2 with r' (Figures 3B, C); the position was confirmed using contrast. The final ECG showed a narrow QRS (80 ms), with normal axes and a right bundle branch image in V1 (Figure 3E).
PMC10192706_03
(A) Initial 12-lead ECG of case 3 taken at 10 mm/mV and 25 mm/s. PM rhythm with single-chamber pacing. AV dissociation (black arrows point to P waves) with a mean atrial rate of 90 bpm, QRS of 160 ms with inferior and right axis, and late transition. (B) QRS notch progression during the first three turns observed in multiple surface ECG leads (arrows point to V1) during advancement of the ventricular electrode through the interventricular septum. (C) QRS notch progression during the last two turns was observed in V2 during the advancement of the ventricular electrode through the interventricular septum. (D) Dual-chamber pacing in the final position of the ventricular electrode with right bundle branch image. (E) Selective stimulation of the left bundle branch of His. Final ECG with normal P-wave and QRS axes, 80 ms final QRS with right bundle branch image, and late transition. (F) Final position of pacemaker, atrial and ventricular endocardial leads. As it can be seen, the epicardial leads were placed in an unusual position, near the AV junction. ECG, electrocardiogram; AV, atrioventricular.
fped-11-1160335-g003.jpg
PMC10192706_03_fped-11-1160335-g003.jpg
F3
The admission ECG showed PM rhythm with single-chamber stimulation and atrioventricular dissociation (Figure 3A). Two more turns were given to the electrode without presenting ventricular extrasystoles with right bundle branch morphology and observing notch displacement in V1 and V2 to the right, finally showing in V1 and V2 with r' (Figures 3B, C); the position was confirmed using contrast. The final ECG showed a narrow QRS (80 ms), with normal axes and a right bundle branch image in V1 (Figure 3E).