KLINIČNI pRIMER/CASE REPORT
Radiofrequency catheter ablation of idiopathic ventricular ectopy originating from the pulmonary artery trunk
Radiofrekvenčna katetrska abLacija idiopatske prekatne ektopije z izvorom iz debLa pljučne arterije
Matevž Jan,1 Petr PeichL,2 Josef Katuzner2
1	Department of Cardiology, University Clinical Centre Ljubljana, Ljubljana, Slovenia
2	Department of Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
Korespondenca/ Correspondence:
Matevž Jan, MD, Department of Cardiology, UCC Ljubljana, Zaloška 7, 1000 Ljubljana E-maiL: janmatevz@ hotmaiL.com
Ključne besede:
radiofrekvenčna katetrska abLacija, idiopatska prekatna ektopija, debLo pljučne arterije
Key words:
radiofrequency catheter abLation, idiopathic ventricuLar ectopy, puLmonary artery trunk
Citirajte kot/Cite as:
Zdrav Vestn 2013; 82: 123-6
Abstract
Idiopathic ventricular ectopy with left bundle branch block morphology and inferior axis commonly originates from the right ventricular outflow tract. It is very unusual for this ectopy to originate from the pulmonary artery trunk. This unusual origin can be recognized by mapping above the pulmonary valve in search of endo-cardial signals that consist of the near field low amplitude multicomponent signal preceding the far field ventricular signal. Pacemapping is often unsuccessful in this setting.
Izvleček
Idiopatska prekatna ektopija z morfologijo le-vokračnega bloka in navzdol obrnjeno osjo navadno izvira iz iztočnega dela desnega prekata. Zelo nenavadno je, da takšna ektopična aktivnost izvira iz debla pljučne arterije. Ta nenavaden izvor lahko najdemo s kartografijo nad pulmonal-no zaklopko, kjer iščemo značilne endokardialne električne signale, ki so sestavljeni iz začetnega nizko-amplitudnega večfaznega dela ter sledečega značilnega prekatnega signala. Kartografija s stimulacijo je na tem mestu pogosto neučinkovita.
Introduction
Ventricular extrasystoles or tachycardia with left bundle branch block morphology and inferior axis usually indicate that the origin of the ectopy is in the right ventricular outflow tract (RVOT). Although specific sites within the RVOT have been associated with typical electrocardiographic (ECG) patterns, localization of the ectopy above the pulmonary valve is more challenging.1-3 Although pulmonary artery trunk was pre-
viously considered a rare origin of ventricular ectopy, in selected studies it has been described to occur in up to 10 and 25 % in patients refered for the ablation of the ventricular ectopy presumably originating within the RVOT.4'5
We present a case of a patient with idiopathic ventricular ectopy with ECG characteristics corresponding to RVOT origin with subsequent successful ablation in the pulmonary artery trunk.
Prispelo: 29. mar. 2012, Sprejeto: 28. maj 2012
Figure 1: Panel A: initial ventricular ectopy, Panel B: a good pacemap, Panel C: early endocardial signal by -35 ms at the location of the good pacemap.
Case report
The patient was a 50-year-old woman, who besides a history of being a smoker had no additional risk factors for cardiovascular diseases. She was symptomatic for palpitations for three years with slow progression of symptoms over time. There was documented ventricular bigeminy originating from the RVOT on the ECG taken during palpitations. Treatment with metoprolol and propafenone was ineffective.
The 12-lead ECG with ectopy (Figure 1, Panel A) showed left bundle branch morphology with inferior axis, with notching in leads III and aVF, low voltage RSr in lead I, QS in leads Vi, aVL and aVR, R/S transition in V3 and small R in V2. According to transthoracic echocardiographic examination, she had no obvious structural heart disease.
Endocardial electrograms were analyzed using the Cardiolab system (Prucka Engineering Inc., Houston, Texas, USA), Filter for endocardial electrograms was set to 30-500 Hz, paper speed was set to 200 mm/s. A 3D
electroanatomic mapping system (EnSite NavX, St. Jude Medical, St. Paul, Minnesota, USA) was also used. Navistar ThermoCool, 7Fr, 3.5 mm irrigated tip catheter (Biosense Webster, Diamond Bar, CA, USA) was used for mapping and radiofrequency ablation. Radiofrequency ablation parameters were set to 25-30 W with an upper limit of temperature at 45 °C.
After introduction of the catheter via the right femoral vein, the procedure was started by creation of a 3D anatomical reconstruction of the right ventricle. Locations of the His bundle and the pulmonary valve were annotated according to endocardial electro-grams (Figure 2). Ablation site was selected by a combination of activation mapping and pace mapping. Using this approach, the site with pacemap match 12/12 and the earliest endocardial bipolar signal (-35ms) was allocated into the anteroseptal part of the RVOT just below the pulmonary valve (Figure 1, Panel B and C). Ablation at that location did not result in termination of ventricular ectopy, however, there was a change in the morphology of the QRS (Figure 3, Panel A).
Figure 2: 3-D anatomical reconstruction of the right ventricle from posteroanterior (Panel A) and left lateral (Panel B) views showing the position of the pulmonary valve (uppermost border), the His bundle (yellow dot), ablation attempts in the RVOT (red dots), ablation attempt that resulted in the modified morphology of the ectopic beats (lower green dot), and successful ablation in the pulmonary artery trunk (upper green dot).
The R wave amplitude became larger in the inferior leads and R waves became more prominent in V2 and V3. After several additional unsuccessful ablation attempts within the RVOT, mapping was performed in the pulmonary artery trunk, where low-amplitude multicomponent signal preceeding the QRS complex by 53 ms during ventricular extrasystoles was found on the septal wall of the pulmonary artery trunk (Figure 3, Panel B). The pacemap was not performed due to inability to capture even with the highest pacing energy. Radiofrequency ablation at the site of the earliest low amplitude multicom-ponent signal resulted in immediate termination of the ventricular ectopy. Further ec-topy was not inducible despite isoprenaline challenge.
Discussion
In the course of the described mapping and ablation procedure we found a distinct pattern of endocardial electrograms in the pulmonary artery trunk that were also described and studied by Yamashina et al.5 These signals consist of the near field low amplitude multicomponent signal preceding the far field ventricular signal. These characteristic low amplitude multicom-ponent signals could be due to myocardial extensions in the pulmonary artery trunk that are probably the result of incomplete myocardial regression during the development of the heart and were discovered
B
in humans and animals.6-8 Yamashina et al. discovered that they were able to do a pace map in the pulmonary artery trunk in 5 of 8 studied patients, whereas Sekiguchi et al. could only perform pace mapping by high voltage pacing in 63 % of patients/'4 Thus, according to our own experience and the data from the literature it is reasonable to rely on the activation mapping and the specific endocardial electrogram pattern rather than on the pace mapping when attempting ablation of the ventricular ectopy in the pulmonary artery trunk. Thermal mapping might be useful, but was not yet tested in this setting.9'10 We also found a change in the QRS morphology of ventricular extrasystoles after unsuccessful ablation in the RVOT. Similar observation was made by Timmer-mans et al." A probable explanation for this phenomenon is that we initially ablated one of the exit points of the ectopy and that the following exit point was more cranial and posterior as indicated by higher amplitude of R waves in inferior leads and more prominent R waves in V2 and V3.
Conclusion
We conclude that in patients with idio-pathic ventricular ectopy presumably originating in the RVOT it has to be kept in mind that the actual source of the ectopy might be in the pulmonary artery trunk. So, if initial ablation attempts in the RVOT prove to be unsuccessful, the next step should include
Figure 3: Panel. A: modified morphology of the ectopic beats, Panel B: earliest endocardial activity by -53ms above the pulmonary valve.
mapping the area above the pulmonary valve in search for characteristic endocardial electrograms during the ectopy.
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