PMC9039091_01
Left (LAO, on the left panel) and right (RAO, on the right panel) anterior oblique projections of the electroanatomical map obtained with the diagnostic decapolar catheter, using the Abbott EnSite Precision mapping system (Abbott Inc, St Paul, MN). In the central panel, the His bundle potential is shown (green electrogram), together with baseline spontaneous QRS complex morphology. Yellow dots indicate His bundle cloud. Color-coded structures: yellow = superior vena cava; lilac = inferior vena cava; gray = right atrium; green = right atrial appendage; red = coronary sinus; purple = right ventricle; blue = right ventricular outflow tract.
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fig1
Special care was applied to depict the area where His bundle potentials were found (Figure 1). The continuous unipolar connection of the cathode during lead rotations was made possible by cutting away the alligator clip of the cathode cable and wrapping the resulting wires around the corresponding lead pin electrode in such a way as to obtain a kind of revolving adapter, as previously described by Jastrzebski and Moskal (Supplemental Figure 1A). After atrial lead sleeve suture, before the catheters were connected to a dual-chamber pacemaker (Azure S DR; Medtronic, Minneapolis, MN), the patient was centered in the fluoroscopy field to acquire a single-shot (less than 1 s) X-ray evaluation of the leads' slacks (Supplemental Figure 1B).
A: Paced QRS morphology at the initial screwing point on the right ventricular surface of the septum; a "W" pattern in V1 is seen. B: Paced QRS morphology at the end of screwing, with nonselective left bundle branch capture; stimulus-to-R-wave peak time in lead V6 is 64 ms. C: Programmed unipolar tip stimulation of the left bundle branch area lead, showing an abrupt change in paced QRS morphology at the coupling interval of 300 ms, suggesting transition to left ventricular septal myocardial capture (thus confirming nonselective left bundle branch capture obtained).
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Screwing was stopped once the unipolar-paced QRS showed a right bundle branch block morphology (Qr complex in lead V1), with a constantly short R-wave peak time in lead V6 (64 ms), both with high and low outputs (capture threshold = 0.5 V at 0.4 ms pulse width) (Figure 2B). Programmed unipolar tip stimulation was also performed and confirmed the nonselective left bundle branch capture obtained (effective refractory period of the left bundle branch = 300 ms) (Figure 2C).
A, B: Right anterior oblique projection (RAO, A) and a cranial view of the left anterior oblique projection (LAO, B) of the electroanatomical map, showing the final positions of the implanted atrial and left bundle branch area pacing lead tips (RA and LBBAP, respectively), in bipolar visualization, together with the bipolar electrogram of the LBBAP lead, showing a small sharp potential anticipating local ventriculogram of 15 ms. Yellow dots indicate His bundle cloud. Color-coded structures: yellow = superior vena cava; lilac = inferior vena cava; gray = right atrium; green = right atrial appendage; red = coronary sinus; purple = right ventricle; blue = right ventricular outflow tract.
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At this point the lead body was readvanced in such a way as to obtain an appropriate, J-shaped slack, as presumed observing the subsequent variations in the anode position (Figure 3).