PMC9845553_01
Electrophysiological study. A: Twelve-lead electrocardiogram (ECG) prior to ablation. B: Orthodromic atrioventricular reentrant tachycardia with right bundle branch block QRS morphology and QRS complex duration of 120 ms. C: Local electrograms at successful ablation site of the right posteroseptal accessory pathway from the cryo-catheter (FRZ dist and uni) with ventricular signal coinciding with delta wave onset. The strictly negative ventricular signal from the ablation catheter tip (FRZ uni) is in favor of correct placement at the ventricular insertion site of the posteroseptal pathway. D: Local electrograms after posteroseptal pathway ablation (FRZ dist) with clear division of the atrial and ventricular electrogram at the ablation site. E: Twelve-lead ECG showing different QRS morphology after posteroseptal pathway ablation with a delta wave evident especially in leads I and V4. F: Local electrograms at the site of the second unsuccessfully ablated right posterior pathway (FRZ dist) with ventricular signal clearly preceding delta wave onset. G: Three-dimensional electroanatomical map of the earliest ventricular activation on the tricuspid annulus (delineated by the black line) during sinus rhythm. First manifest pathway could be successfully ablated in the right posteroseptal region (green arrow). The second manifest pathway could be mapped to the posterior tricuspid annulus (blue arrow) and could not be ablated. The distance between the 2 mapping sites was estimated to be 10 mm (white line) and is in favor of 2 distinct pathways rather than 1 broad pathway, although this cannot be definitely proven. FRZ dist indicates distal bipolar signal from the ablation catheter; FRZ uni, unipolar signal from the ablation catheter tip; CS, signals from the coronary sinus catheter from proximal to distal. Vertical lines depict delta wave onset.
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Her resting electrocardiogram revealed a sinus and low right atrial rhythm with ventricular preexcitation compatible with a right posteroseptal-to-posterior manifest accessory pathway (Figure 1A). During electrophysiological study using the EnSite Precision  3D cardiac mapping system, an orthodromic atrioventricular reentrant tachycardia with right bundle branch block QRS morphology was easily inducible by single atrial extrastimuli (Figure 1B). Initially, successful cryoablation of a right posteroseptal manifest accessory pathway was performed, resulting in a change of the preexcitation pattern and separation of local atrial and ventricular electrograms (Figure 1C-1E). Another right posterior manifest pathway could not be ablated successfully (Figure 1F and 1G). The distance of approximately 10 mm between both mapping sites (Figure 1G) is in favor of the presence of 2 distinct pathways rather than 1 broad pathway, although this could not be definitely proven.
A: Twelve-lead electrocardiogram after right ventricular cardiac resynchronization therapy (RV-CRT) showing narrow QRS complex (=70 ms) with absence of right bundle branch block. B: Longitudinal strain imaging of the right ventricle during baseline rhythm with right bundle branch block. Significant RV mechanical dyssynchrony is evident with early septal contraction (green arrow) accompanied by RV free wall pre-stretch (yellow arrow) followed by late free wall contraction (red arrow) and septal rebound stretch (orange arrow). Peak basal RV free wall contraction occurs 57 ms after pulmonary valve closure (PVC; green line), thus not contributing to RV ejection. RV septal-to-free wall mechanical delay is 97 ms. C: During RV-CRT RV dyssynchrony is abolished with synchronous contraction of the septum and RV free wall. Peak basal RV free contraction occurs almost simultaneously with pulmonary valve closure. RV contraction efficiency is restored.
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Permanent RV-CRT was implemented by implanting a dual-chamber pacemaker with an epicardial right atrial and RV free wall lead, respectively, programmed to DDD mode with AV delay optimized to achieve complete fusion of the paced and spontaneous ventricular activation and narrow pseudo-normalized QRS complex without signs of right bundle branch block (Figure 2A). Immediate resynchronization effect was tested on the 14th postoperative day by switching RV-CRT on and off, showing narrow QRS complex and lasting acute improvement of multiple hemodynamic parameters, including RV contraction synchrony and efficiency, as reflected by decreased RV systolic stretch fraction (Table 1, Figure 2B and 2C).