A 45-year-old gentleman presented to our Cardiology Department with persistent palpitations and concerning fatigue. Despite a thorough investigation involving multiple imaging exams, such as a 2D-echocardiogram, cardiac MRI, and CT scans, no remarkable abnormalities were discerned. However, during a 24-h EKG Holter monitoring 16,000 premature ventricular contractions (PVCs) were unveiled, accounting for a 15 % burden. These PVCs displayed a distinctive morphology with a left bundle branch block (LBBB) pattern and a left superior axis (Fig. 1, Panel A). Unfortunately, the conventional treatment approach with beta-blockers was ineffective in suppressing the arrhythmias. Thus, patient was scheduled for electrophysiology study involving mapping and eventual ablation of the ectopic focus. On the base of EKG morphology, we employed a meticulous anatomical reconstruction method utilizing intracardiac echocardiography (ICE) to scan all intracavitary structures within the right ventricle (RV) [1]. The ICE probe was initially introduced into the right atrium, providing a rapid visualization of the tricuspid valve and the external contours of the RV, including the apex, diaphragmatic wall, and RV outflow tract. Continuing the procedure, the probe was advanced into the right ventricle, allowing a more comprehensive view of the intracavitary structures. With gentle rotations and precise movements, we were able to visualize critical anatomical landmarks, including the septo-marginal trabecula (SMT), inferior papillary muscle, anterior papillary muscle, moderator band (MB), and apical trabeculation (Fig. 1, Panel B). To enhance our precision, we utilized the CARTOSOUND module to create a detailed 3D map incorporating these structures (Fig. 1, Panel C). With this map as our guide and without the use of fluoroscopy, we skillfully navigated an irrigated ablator catheter to the exact location from which the PVCs originated. The activation map and pace map pinpointed the source of the PVCs at the intersection between the moderator band and the base of the anterior papillary muscle (Fig. 2). The irrigated ablator (thermocool smarttouch™|Biosense Webster) was stabilized with a long deflectable sheath and radiofrequency energy was precisely delivered to this specific site, resulting in the abolition of the mapped arrhythmias (video 1). PVCs originating by intracavitary structures pose a challenge for ablation because of the known limitations of fluoroscopy and 3D electro-anatomical systems [2]. The RV is a chamber of the heart where papillary muscles and apical trabeculation are highly prominent, and their anatomy can be variable. Furthermore, it contains accessory structures like MB, which is the direct continuation of the SMT [3]. These distinctive features significantly complicate both navigation and contact within the camber. In our case using a contact-force radiofrequency catheter trough a long deflectable sheet offered improved stability. However, cryoablation in this highly unstable location could improve efficacy in terms of lower recurrences [4]. Throughout our procedure real-time intracardiac echocardiography played an indispensable role in ensuring the success and safety of the ablation, providing us with invaluable guidance and assurance.
Fig. 1.
Panel A: 12-lead EKG of clinical PVC with left bundle branch block (LBBB) pattern and a left superior axis and late transition in precordial leads. Panel B: Intracavitary anatomy of the right ventricle obtained by multiple 2D scans with the ICE probe. The ICE probe is in the right ventricle (tricuspid valve has been passed) and is directed towards the anterior wall of the chamber where the intersection between the moderator band and the anterior papillary muscle is discerned (red arrow: successful ablation point). Panel C: The 3D-cartosound reconstruction of the whole chamber is exposed where all the intracavitary structures visualized with the 2D-echo scans are reconstructed into the tridimensional map. APM: anterior papillary muscle, MB: moderator band, TV: tricuspid valve, IPM: inferior papillary muscle, SMT: septo-marginal trabecula.
Fig. 2.
Panel A: 3D-cartosound shell (in transparency) of the right ventricle. Inside the chamber mapping is focused point-by-point on the moderator band. The color scale displays the activation mapping spreading from the distal attachment (red) to the medial part (other colors). Panel B: 12-lead EKG morphology of the PVC ablated with activation mapping recording an earlier potential of 21 before the 12-lead-surface activation in the successful point of ablation. Panel C: The pace mapping in the successful point resulted in a 90 % corresponding morphology with the 12-lead EKG morphology.
Ethical statement
The patient regularly signed written informed consent.
Funding
This research received no external funding.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Footnotes
Peer review under responsibility of Indian Heart Rhythm Society.
Supplementary data to this article can be found online at https://doi.org/10.1016/j.ipej.2024.01.007.
Appendix A. Supplementary data
The following is the Supplementary data to this article:
Video 1 = Ablation was carried out under the guidance of the intracardiac echocardiography. The ablator catheter was stabilized at the intersection between the moderator band and the anterior papillary muscle. Radiofrequency applications at this level abolished all the arrhythmias.
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