A case of premature ventricular contraction originating at the aortomitral fibrous continuity and exiting from the anterolateral papillary muscle due to muscular chordae tendineae

Figures

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  Figure 1. 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.

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  Figure 2. 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…

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  Figure 3. Cardiac computed tomography image, schematic views of the premature ventricular contraction (PVC) conduction pathway, and peripheral structure and development of the papillary muscle. A: Reconstructed cardiac computed tomography images confirmed myocardial bundle tissue connected to the AMLAMFC. B: PVC originated at the AMLAMFC region and was assumed to exit from the left ventricle via the muscular chordae tendineae and ALPM. C: After epithelial-mesenchymal transition, papillary muscles, chordae tendineae, and atrioventricular valve are formed via myocardial delamination approximately 5–15 weeks after embryogenesis. The leaflets and chordae tendineae are formed from a basal layer of laminin-positive cells and a cell layer of collagen III and fibronectin-positive cells. Myocardium remaining in this area gradually retracted toward the annulus and papillary muscles and finally disappeared. In this case, it is suggested that residual myocardium remained in the chordae tendineae. It has been reported that the residual myocardium can be anatomically observed as a “muscular chordae tendineae,” which is much thicker than any other chordae. ALPM = anterolateral papillary muscle; AMFC =…