PMC9845550_01
Electrocardiogram and echocardiographic findings. A: Electrocardiogram showing premature ventricular contraction with right bundle branch block pattern and right inferior axis. B: Echocardiography showing a long-axis image of the left ventricle in the diastolic phase. Relatively thick anterolateral papillary muscle chordae tendineae attached to anterior mitral leaflet were observed.
gr1.jpg
PMC9845550_01_gr1.jpg
fig1
Based on the previous report, ALPM was suspected as the origin (Figure 1A). Echocardiography revealed a 60.4% ejection fraction, no enlargement of chamber size or valvular disease, and relatively thick ALPM chordae tendineae attached to the AML (Figure 1B).
Findings during catheter ablation. A: A trabeculated structure that continuously binds to the anterior mitral leaflet (AML) was confirmed by intracardiac ultrasound. Along this structure, discrete prepotential was recorded from the aortomitral fibrous continuity (AMFC) to the anterolateral papillary muscle (ALPM). B: The activation map of the premature ventricular contraction (PVC) exhibited the earliest activation site at the AMLAMFC region. The exit site of the PVC was on the basal side of the ALPM. C: The discrete prepotential recorded at the distal electrodes of ablation catheter leading to PVC was observed up to 84 ms earlier than the onset of QRS. This potential was observed as a delayed potential behind the QRS during sinus rhythm. D: The pace mapping score was the highest on the ALPM basal side, but very low in the AMFC region. E: PVC was not eliminated and QRS morphology did not change during radiofrequency ablation at the ALPM, which was considered the exit site. When RF ablation was applied to the AMLAMFC, accelerated PVC was observed. The QRS morphology of the accelerated PVC was identical to that of clinical PVC. ABL = ablation catheter; CS = coronary sinus HBE = His bundle electrogram; LVOT = left ventricular outflow tract; MV = mitral valve; PASOTM = pace mapping software (CARTO3; Biosense Webster, Inc, Irvine, CA), RV = right ventricle. Yellow tag: pace mapping points; purple tag: prepotential points; red or pink tag: radiofrequency application points.
gr2.jpg
PMC9845550_01_gr2.jpg
fig2
A trabeculated structure was noted from the ALPM to the AML (Figure 2A). Contrary to what we anticipated, the earliest activation was at the AMLAMFC (Figure 2B), where a discrete prepotential preceded the QRS onset of the PVC by 84 ms (Figure 2C). This site coincided with the trabeculated structure noted by the intracardiac ultrasound (Figure 2A). The discrete potential noted during PVC could be observed after the offset of the QRS during sinus rhythm, which suggested the retrograde conduction via the trabeculated structure (Figure 2C). Pace mapping score obtained by the PaSoTM module (Biosense Webster, Inc) was the best at the base of the ALPM; however, the score was low at the AMLAMFC (Figure 2D). Radiofrequency (RF) ablation was first applied using a 3.5 mm irrigation catheter (THERMOCOOL SMARTTOUCHTM SF; Biosense Webster, Inc) at the ALPM where the best pace mapping score was obtained (Figure 2E). RF application at the AMLAMFC successfully eliminated the PVC after accelerated PVCs with the same morphology (Figure 2E).