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Right ventricular outflow tract ablation close to an anomalous right coronary artery: When imaging meets electrophysiology

Open AccessPublished:December 28, 2022DOI:https://doi.org/10.1016/j.hrcr.2022.12.016

      Keywords

      Key Teaching Points
      • Anomalous coronary arteries are rare and, owing to their unfamiliar course, can significantly increase risk of coronary injury when ablating around the ventricular outflow tracts.
      • Computerized tomography coronary angiography can be merged with 3D electroanatomical mapping via the CARTO-Segmentation module (Biosense Webster), and this provides important insight into the proximity of coronary arteries to the ablation target. This can be further augmented with intracardiac echocardiography.
      • This case report shows how CARTO-Segmentation was effective in locating the path of an anomalous coronary artery with excellent spatial resolution during outflow tract ablation, and without the need for invasive coronary angiography.

      Introduction

      Catheter ablation is a commonly undertaken and highly effective treatment for symptomatic right ventricular outflow tract (RVOT) ventricular ectopy / ventricular tachycardia (VT).
      • Joshi S.
      • Wilber D.J.
      Ablation of idiopathic right ventricular outflow tract tachycardia: current perspectives.
      Despite the high chance of cure with ablation, caution is required to avoid collateral injury to coronary arteries in certain well-described locations. Anomalous coronary arteries are rare
      • Angelini P.
      • Velasco J.A.
      • Flamm S.
      Coronary anomalies: incidence, pathophysiology, and clinical relevance.
      and may have an unfamiliar path involving the outflow tracts, posing a significantly increased risk with ablation. The approach to outflow tract ablation in a patient with an anomalous coronary artery has not been previously reported. Imaging is crucial. We present a case of successful RVOT VT ablation guided by a merged cardiac computerized tomography (CT) and intracardiac echocardiography (ICE), where an anomalous right coronary artery (RCA) resided 1 mm from the posterior RVOT.

      Case report

      A 46-year-old lorry driver, with no prior cardiac symptoms or history, presented to a local general hospital with repetitive bursting monomorphic outflow tract–type VT, associated with chest pressure and presyncope. Intravenous amiodarone in their emergency department settled the VT with persisting ventricular ectopics. The ectopic electrocardiography (ECG) morphology and VT were identical (Figure 1) and suggested an RVOT origin (left bundle branch block type, inferior axis, R-wave transition V4). Cardiac magnetic resonance imaging demonstrated a structurally normal heart with no scar.
      Figure thumbnail gr1
      Figure 1Electrocardiogram strips of the “bursting monomorphic ventricular tachycardia” and subsequent unifocal ectopy.
      An ECG-gated contrast enhanced CT coronary angiogram was also performed at the local hospital, as the presentation was associated with a small troponin rise, revealing an unobstructed anomalous RCA. This was seen to arise from the left coronary cusp, taking a low interarterial course, below the pulmonary valve, hugging the posterior aspect of the RVOT with 1 mm distance (Figure 2 and Supplementary Video 1). An invasive coronary angiogram was undertaken owing to some mid–left anterior descending artery (LAD) disease seen on CT, which was found to be nonobstructive. The cardiac interventionalists were unable to engage the RCA with multiple catheters. The case was reviewed by electrophysiologists in our center; as radiofrequency ablation was felt to pose an additional unknown risk of iatrogenic coronary injury, conservative treatment with beta-blockade was favored, especially as we would be unlikely to engage the RCA with a coronary catheter in the event of an iatrogenic occlusion. The patient was unfortunately prohibited from driving (his livelihood) pending further evaluation.
      Figure thumbnail gr2
      Figure 2Left: Computerized tomography (CT) coronary angiogram. Note the anomalous origin of the right coronary artery (RCA) from the left coronary cusp taking a low interarterial course between the ascending aorta (AA) and posterior aspect of the right ventricular outflow tract (RVOT); the distance between the RCA and RVOT was 1 mm. Top right: 3D volume–rendered reconstruction of the coronary anatomy. Bottom right: Cardiac CT was imported into CARTO (Biosense Webster) and an automated 3D reconstruction of the cardiac geometry and coronary anatomy was created using CARTOSEG. DA = descending aorta; LA = left atrium; LAD = left anterior descending artery, LMS = left main stem.
      The patient presented again a few weeks later with the same VT and presyncope. Following discussion in a multidisciplinary team heart rhythm meeting, potentially curative ablation was considered reasonable if cardiac imaging allowed sufficient visualization of the vessel, with >5 mm distance between the vessel and ablation target.
      • Aliot E.M.
      • Stevenson W.G.
      • Almendral-Garrote J.M.
      • et al.
      EHRA/HRS expert consensus on catheter ablation of ventricular arrhythmias.
      This was discussed in detail with the patient, who preferred a potentially curative approach to stand a better chance of driving again. He understood there was an element of added risk that we could not quantify.
      The contrast-enhanced cardiac CT was imported as a DICOM file into the 3D electroanatomical CARTO mapping system (Biosense Webster, Irvine, CA), and a semiautomatic 3D reconstruction of the cardiac geometry and coronary anatomy was created (CARTO-CT Segmentation module [CARTOSEGTM]), and was available for display during the case using the CARTOMERGE module (Figure 2 and Supplementary Video 1). This was achieved by registering landmark tomographic points around the ascending aorta on CARTO, along with corresponding points on the mesh reconstruction.
      • Imanli H.
      • Bhatty S.
      • Jeudy J.
      • et al.
      Validation of a novel CARTOSEGTM segmentation module software for contrast-enhanced computed tomography-guided radiofrequency ablation in patients with atrial fibrillation.
      The patient presented in sinus rhythm with frequent RVOT ectopy (Figure 3A). An ultrasound-guided reconstruction of the contours of the cardiac chambers was created using ICE via the CARTOSOUND module, with particular attention paid to the RVOT, pulmonary artery, coronary cusps, and aortic root. The origin of the anomalous vessel was carefully imaged. This was merged with the reconstructed cardiac geometry depicted using CARTOSEG (Figure 3B and 3C) against these defined landmarks (particularly the ascending aorta). Importantly, the live display of the origin of the anomalous coronary artery seen with ICE entirely collocated with the path of the vessel on CARTOSEG. This gave us the assurance that the vessel depicted on our mapping system was accurate in location. No further attempts to visualize the RCA with invasive angiography were thus made.
      Figure thumbnail gr3
      Figure 3A: At top, 12-lead electrocardiogram of the ectopic (left bundle branch block type, inferior axis, R-wave transition V4); at bottom, earliest bipolar (blue) and corresponding unipolar (white) electrogram, 30 ms pre-QRS with a QS unipole. B: Cardiac geometry collected using intracardiac echocardiography and CARTOSOUND (Biosense Webster) merged with the geometry created using CARTOSEG. The origin of the anomalous right coronary artery (RCA) on ICE (CARTOSOUND RCA) collocated with the origin on CARTOSEG. Earliest activation was on the septal aspect of the right ventricle (RV) outflow tract, away from the anomalous RCA. It was in proximity to the proximal left anterior descending artery (LAD; a well-recognized location). C: The ascending aorta was used to register the computerized tomography (blue) and ultrasound (purple) cardiac reconstructions. A closer view of the origin and proximal anomalous RCA with CARTOSOUND (brown) collocated with the artery on CARTOSEG. D: ICE image of the origin of the anomalous vessel. E: Radiofrequency (RF) ablation (RF on) eliminated the ectopic, with no ST change. LV = left ventricle., LMS = left main stem.
      Earliest activation was seen on the septal aspect of the RVOT (30 ms pre-QRS with a QS morphology on unipolar electrogram) (Figure 3A and 3B). This was just underneath the pulmonary valve and fortunately away from the anomalous coronary artery. This site is recognized to be close to the proximal LAD, readily apparent in the image; hence only 25–30 W of irrigated ablation was delivered (ThermoCool SmartTouch D-F; Biosense Webster), with <10 g contact force, and for no more than 30 seconds. This eliminated the ectopic focus (Figure 3E), with no ST change on 12-lead ECG. Subsequent VT stimulation protocols with isoprenaline, including 2 drive trains and double extrastimuli, resulted in no inducible ectopy or ventricular arrhythmia. Postoperative recovery was uneventful and no further sustained VT has recurred in 6-month follow-up. An exercise test revealed no signs of inducible myocardial ischemia or sustained VT recurrence, allowing the patient to return to professional driving.

      Discussion

      Catheter ablation carries a class I indication for patients with symptomatic RVOT VT in the European Society of Cardiology (ESC) guidelines and is considered first line ahead of drug therapy.
      • Zeppenfeld K.
      • Tfelt-Hansen J.
      • de Riva M.
      • et al.
      2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death.
      To the best of our knowledge, this is the first case report of attempted RVOT ablation in a patient with an anomalous RCA.
      Anomalous coronary arteries are rare, occurring in less than 1% of the population.
      • Angelini P.
      • Velasco J.A.
      • Flamm S.
      Coronary anomalies: incidence, pathophysiology, and clinical relevance.
      Multiple forms are recognized. Our patient had an anomalous interarterial RCA arising from the left anterior sinus, which has a prevalence of around 0.1%.
      • Kim S.Y.
      • Seo J.B.
      • Do K.H.
      • et al.
      Coronary artery anomalies: classification and ECG-gated multi–detector row CT findings with angiographic correlation.
      An important distinction is whether the interarterial course is high (between the great vessels) or low (between the aortic root and RVOT).
      • Wu G.R.
      • Saini A.
      • Ahmed I.
      • Finch C.
      Interarterial course of anomalous right coronary artery: pathophysiology, diagnosis, and treatment.
      The high course is associated with a risk of sudden cardiac death, usually during exercise, and may relate to compression of the anomalous orifice by aortic dilatation, or compression of the RCA between the great vessels.
      • Kim S.Y.
      • Seo J.B.
      • Do K.H.
      • et al.
      Coronary artery anomalies: classification and ECG-gated multi–detector row CT findings with angiographic correlation.
      The ESC guidelines give a class Ic recommendation for surgery in patients with angina and evidence of stress-induced ischemia,
      • Baumgartner H.
      • de Backer J.
      • Babu-Narayan S.V.
      • et al.
      2020 ESC Guidelines for the management of adult congenital heart disease.
      which our patient did not have. Our patient had a low interarterial course, which, while a lower-risk scenario, can significantly increase the risk of iatrogenic myocardial infarction if radiofrequency catheter ablation is considered within its vicinity.
      Ablating near to the coronary arteries carries a risk of inducing acute coronary spasm and iatrogenic myocardial infarction. The distance from a coronary artery at which it is safe to ablate is not well understood. Expert consensus, based upon the available evidence, suggests >5 mm, though this is in the setting of epicardial ablation.
      • Aliot E.M.
      • Stevenson W.G.
      • Almendral-Garrote J.M.
      • et al.
      EHRA/HRS expert consensus on catheter ablation of ventricular arrhythmias.
      In our case, the anomalous vessel hugged the posterior aspect of the RVOT with 1 mm distance. The risk was further increased as the interventionalists had been unable to engage the RCA at invasive angiography, meaning any intervention in the case of iatrogenic coronary occlusion may have required emergency bypass grafting. Integrated imaging using a combination of cardiac CT (CARTOSEG) and ICE allowed precise delineation of the anomalous coronary artery during the procedure and assured us that our ablation site in the RVOT was much greater than 5 mm from the RCA.
      The efficacy of ICE and CARTOSOUND is well known and used routinely in clinical practice in many labs. While it allows direct visualization of the left main coronary ostium, the right coronary ostium is more difficult to image, and no visualization of the complete epicardial course of the coronaries is possible. In the setting of an anomalous RCA, operator confidence identifying the vessel in real time may be reduced owing to unfamiliarity of the vessel course. Merging of CT imaging into 3D electroanatomical mapping systems has been previously described and used to avoid injury to extracardiac structures, such as the phrenic nerve and—as in our case—the epicardial coronary arteries.
      • Yamashita S.
      • Sacher F.
      • Mahida S.
      • et al.
      Role of high-resolution image integration to visualize left phrenic nerve and coronary arteries during epicardial ventricular tachycardia ablation.
      Several advanced centers have developed bespoke software for coronary visualization, though this can incur long processing times and is generally unavailable in clinical practice.
      • Cochet H.
      • Komatsu Y.
      • Sacher F.
      • et al.
      Integration of merged delayed-enhanced magnetic resonance imaging and multidetector computed tomography for the guidance of ventricular tachycardia ablation: a pilot study.
      Prior commercial software for image integration had lower resolution, limiting precise anatomical depiction. CARTOSEG offers 1 mm spatial resolution of all heart chambers and coronary arteries based on contrast-enhanced cardiac CT. The system uses a semi-automatic “single-button” algorithm to reconstruct endocardial cardiac surface anatomy (including trabeculations and papillary muscles) from a contrast-enhanced CT scan within CARTO, and without additional manual input. In the only published study using this module, average segmentation time was <5 minutes and ablation was performed safely near the coronary arteries without the need for invasive coronary angiography.
      • Tovia-Brodie O.
      • Belhassen B.
      • Glick A.
      • et al.
      Use of new imaging CARTO® segmentation module software to facilitate ablation of ventricular arrhythmias.
      To the best of our knowledge, its application has not previously been described in a case of an anomalous coronary artery.
      Septal regions of the RVOT can be in proximity to the proximal LAD, as was apparent in our case. Acute LAD occlusion after RVOT ablation has been reported.
      • Benhayon D.
      • Nof E.
      • Chik W.W.
      • Marchlinski F.
      Catheter ablation in the right ventricular outflow tract associated with occlusion of left anterior descending coronary artery.
      Reassuringly, while RVOT radiofrequency ablation is commonly performed, iatrogenic thermal LAD injury is rare, perhaps owing to convective cooling of nearby coronary blood flow and catheter instability in the outflow tract.
      • Vaseghi M.
      • Cesario D.A.
      • Mahajan A.
      • et al.
      Catheter ablation of right ventricular outflow tract tachycardia: value of defining coronary anatomy.
      In our case, CARTOSEG elegantly highlighted the relationship of the LAD to the site of earliest activation in the septal RVOT and encouraged us to use lower power, contact force, and duration of energy delivery.
      Preprocedural coronary imaging is not routinely performed before outflow tract ventricular ectopy ablation in our center. The plan to undertake a cardiac CT was made by our local general hospital given the accompanying troponin leak. This report highlights how advanced cardiac imaging techniques (CARTOSEG and ICE) can help operators overcome the challenge of proximity to an anomalous coronary vessel when such an unusual circumstance is encountered. Given the rarity of such anomalies, routine preprocedural imaging of the coronary arteries is unlikely to be beneficial.

      Conclusion

      We describe the first reported case of successful RVOT VT ablation in a patient with an anomalous RCA in close proximity to the RVOT. Integrated imaging was crucial, with direct visualization of the vessel achievable using intracardiac echo and the recently implemented CARTOSEG module to rapidly delineate the vessel with high accuracy.

      Appendix. Supplementary Data

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