Right Ventricular Outflow Tract Arrhythmias Research Articles

AP-452681-3 VENTRICULAR TACHYCARDIA ORIGINATING NEAR THE HIS-BUNDLE: ELECTROCARDIOGRAPHIC, CATHETER ABLATION CHARACTERISTICS AND LONG-TERM OUTCOME

Ventricular Arrhythmias (VAs) not uncommonly originate from the Para Hisian (PH) region. The clinical and electrophysiological (EP) characteristics of these VAs are important to recognize given risk of injury to the conduction system. Define the clinical and EP characteristics of these VAs and long-term outcome of catheter ablation. 43 patients (Pts.) had VAs activation mapped to the PH region. The electrocardiographic and EP characteristics of these PH VAs were compared in 50 patients with VAs originating from right ventricular outflow tract (RVOT). Mean QRS width was narrower in PH VAs (P=0.02) and the R wave amplitude was lower in the inferior leads (P = 0.01) as compared to RVOT VAs. PH VAs had an R wave amplitude greater in lead I (P= 0.001) and lead aVL (P= 0.02) than RVOT VAs. For PH VAs earliest in RV, the R wave amplitude ratio in leads II/III was greater than those in LV (P= 0.02). All left sided PH VAs (12pts) had early transition (≤Lead V2) and were infra-hisian in location. 27/31 Right sided VAs had later transition (≥ Lead V3), 22 (70%) were infra-hisian and 9 (30%) were supra-hisian in location. Inferior Lead discordance was seen in 75% of all pts and was similar in left and right sided VAs. Radiofrequency ablation (RFA) was used upfront in 39 pts. Cryo-ablation used upfront in 2 pts and after RFA in 1 pt. In 30 pts (70%) VAs were eliminated; 9 (21%) had significant suppression (≤5% total residual burden) and 3 (9%) had acute recurrence (<48 hours) and 1 pt. ablation was not attempted given immediate proximity to HB. During follow up of 46±8 months, EF normalized in 37/43 (85%). 2 Pts. developed transient heart block with no treatment needed and 1 with pre-existing pacemaker (PM) had complete heart block. 2 required PM implantations at 39 ± 2 months post ablation due to conduction system disease unrelated to ablation. VAs originating near the His-bundle have distinctive ECG characteristics which aid in recognition and mapping. Catheter ablation can generally be performed safely and effectively.

Efficacy and safety of zero-fluoroscopy ablation of ventricular arrhythmias originating from the right ventricular outflow tract: Comparison with fluoroscopy-guided ablation without a three-dimensional electroanatomic mapping system.

Radiofrequency catheter ablation is the preferred treatment choice for ventricular arrhythmias (VAs) originating from right ventricular outflow tract (RVOT) in symptomatic patients and is usually performed under fluoroscopy guidance. Zero-fluoroscopy (ZF) ablations using 3D mapping system applied for treatment of various types of arrhythmias are trending and practiced in many centers around the world, but rarely done in Vietnam. The objective of this study was to evaluate the efficacy and safety of zero-fluoroscopy ablation of RVOT VAs, compared with fluoroscopy-guided ablation without a 3D electroanatomic mapping (EAM) system. We conducted a nonrandomized, prospective single-center study including 114 patients with RVOT VAs that had electrocardiographic features of typical left bundle branch block, inferior axis QRS morphology, and a precordial transition ≥ V3, from May 2020 to July 2022. The patients were assigned (without randomization) to two different approaches of either zero-fluoroscopy ablation under the guidance of the Ensite system (ZF group) or fluoroscopy-guided ablation without a 3D EAM (fluoroscopy group) in a 1:1 ratio. After a follow-up time of 5.0 ± 4.9 months and 6.9 ± 9.3 months in the ZF and fluoroscopy groups, respectively, the results showed a higher success rate in the fluoroscopy group than in the complete ZF group (87.3% vs 86.8%), although the difference was not statistically significant. No major complication was noted in both the groups. ZF ablation for RVOT VAs can be done safely and effectively using the 3D electroanatomic mapping system. The results of ZF approach are comparable to that of the fluoroscopy-guided approach without a 3D EAM system.

Evaluation of five algorithms in predicting the sublocalisation of right ventricular outflow tract arrhythmia (RVOTA) when compared to 3D electroanatomical mapping origin

Cíl: Srovnat predikční přesnost pěti různých algoritmů, ověřených úspěšnou ablací s použitím 3D elektroanatomického bezkontaktního mapování, u pacientů se symptomatickými i asymptomatickými tachykardiemi výtokového traktu pravé komory (right ventricular outflow tract, RVOT) a vysoce zatížených těmito aryt- miemi. Metody: Do studie bylo zařazeno 28 po sobě následujících pacientů přijatých pro radiofrekvenční katetrizační ablaci pro symptomatické, případně asymptomatické, idiopatické předčasné komorové stahy (premature ventricular contractions, PVC) znamenající vysokou zátěž pro srdeční komory. Všichni pacienti již dříve absolvovali neúspěšnou terapii beta-blokátory a/nebo alespoň jedním antiarytmikem třídy IC (případně takovou léčbu nesnášeli); měli normální ejekční frakci levé komory. U všech pacientů byly prokázány monomorfní PVC s morfologií blokády levého Tawarova raménka s průběhem výsledného vektoru směrem dolů inferior axis. Následně se hodnotila shoda mezi místem vzniku arytmie podle EKG algoritmu a místa určeného pomocí 3D mapování. Z pěti algoritmů byly pro srovnání použity dva pro snadnost použití a zapamatovatelnost (Dixit, Joshi) a tři složitější a přesnější (Ito, Zhang, Pytkowski). Výsledky: Posouzení diagnostické přesnosti prokázalo pouze středně kvalitní přesnost všech algoritmů, přičemž nejpřesnější byl podle kardiologů algoritmus navržený Pytkowským a při hodnocení elektrofyziologem algoritmy navržené Dixitem a Pytkowským. Při srovnání jejich přesnosti, specificity a senzitivity nicméně nebyly nalezeny žádné významné rozdíly (p = 0,99). Závěry: Všech pět publikovaných algoritmů pro určení místa RVOT pomocí 12svodového EKG záznamu bylo z hlediska diagnostické přesnosti, specificity a senzitivity podobných. V naší studii vykázal největší přesnost a specificitu v predikci místa algoritmus Pytkowského, pokud jej hodnotili elektrofyziologové a/nebo kardio- logové. &#169; 2022, ČKS.

Evaluation of five algorithms in predicting the sublocalisation of right ventricular outflow tract arrhythmia (RVOTA) when compared to 3D electroanatomical mapping origin

Abstract Introduction The majority of idiopathic ventricular arrythmias arise from the right ventricular outflow tract (RVOT) and they represent nearly 10% of all ventricular tachycardia (VT) admissions. It is paramount to precisely predict the origin of RVOT arrhythmias to define the appropriate approach before the ablation procedure. Conventional 12-lead electrocardiogram (ECG) is a useful tool for analysing cardiac arrhythmias, and numerous ECG algorithms for predicting the origin of RVOT arrhythmias have been reported. Purpose To compare the predictive accuracy of five different algorithms as verified by successful ablation site using 3D electroanatomical non-contact mapping in patients with symptomatic and asymptomatic but high ventricular burden right ventricular outflow tract (RVOT) tachycardias. Methods 28 consecutive patients admitted for radiofrequency catheter ablation for symptomatic and asymptomatic, but high ventricular burden idiopathic premature ventricular contractions (PVC) were recruited for this study. All patients had previous failed or intolerant to beta-blocker and/or at least one class IC anti-arrhythmic agents, and they had normal left ventricular ejection fraction. All patients had documented monomorphic PVC with left bundle branch block morphology and an inferior axis. Concordance of the arrhythmia origin based on ECG algorithm and 3D mapping system site were further evaluated. Of the five algorithms, two algorithms with easy-applicability and having a memorable design (Dixit and Joshi) and three algorithms with more complex and detailed design (Ito, Zhang, Pytkowski) were selected for comparisons. Results Assessment of the diagnostic accuracy showed that each of the five algorithms had only moderate accuracy, and the greatest accuracy was observed in the algorithm proposed by Pytkowski algorithm when assessed by a general cardiologist and Dixit and Pytkowski algorithms when evaluated by the electrophysiologist. However, when the algorithms were compared for their accuracy, specificity, sensitivity, no significant differences were found (p=0.99). Conclusions All the five published 12-lead ECG algorithms for RVOT location were similar in terms of the diagnostic accuracy, specificity, and sensitivity. In our study, Pytkowski algorithm exhibits the best accuracy and sensitivity among the algorithms, while predicting a precise location and when evaluation is performed by electrophysiologists and/or cardiologists. Funding Acknowledgement Type of funding sources: None.

Evaluation of five algorithms in predicting the sublocalisation of right ventricular outflow tract arrhythmia (RVOTA) when compared to 3D electroanatomical mapping origin

PurposeTo compare the predictive accuracy of five different algorithms as verified by successful ablation site using 3D electroanatomical non-contact mapping in patients with symptomatic and asymptomatic but high ventricular burden RVOT tachycardias.Methods28 Consecutive patients admitted for radiofrequency catheter ablation for symptomatic and asymptomatic, but high ventricular burden idiopathic VPC were recruited for this study. All patients had previous failed or intolerant to beta-blocker and/or at least one class IC anti-arrhythmic agents, and they had normal left ventricular ejection fraction. All patients had documented monomorphic VPC with left bundle branch block morphology and an inferior axis. Concordance of the arrhythmia origin based on ECG algorithm and 3D mapping system site were further evaluated. Of the five algorithms, two algorithms with easy‐applicability and having a memorable design (Dixit and Joshi) and three algorithms with more complex and detailed design (Ito, Zhang, Pytkowski) were selected for comparisons.ResultsAssessment of the diagnostic accuracy showed that each of the five algorithms had only moderate accuracy, and the greatest accuracy was observed in the algorithm proposed by Pytkowski algorithm when assessed by a general cardiologist and Dixit algorithm when evaluated by the electrophysiologist. However, when the algorithms were compared for their accuracy, specificity, sensitivity, no significant differences were found (p = 0.99).ConclusionsThe ECG based algorithms for precise localising RVOTA origin simplify the mapping process, reduce the procedural and fluoroscopic time, and improve clinical outcomes, resulting in greater clinical utility. All the five published 12-lead ECG algorithms for ROTVA differentiation were similar in terms of the diagnostic accuracy, specificity, sensitivity and LRs.

Cardiac magnetic resonance imaging in right ventricular outflow tract arrhythmia: a retrospective analysis from a tertiary care centre in South India

Introduction Arrhythmia arising from right ventricular outflow tract (RVOT) is the most common cause of idiopathic ventricular arrhythmia. Previous studies involving cardiac magnetic resonance imaging (MRI) in these patients are known to show abnormalities in up to 60% of patients. Methodology This was a retrospective descriptive analysis of patients having idiopathic RVOT arrhythmia who underwent cardiac MRI between January 2010 and December 2020. Clinical and demographic details were recorded from the electronic medical records and cardiac MRI of all patients were reviewed. Results Among 214 patients with RVOT arrhythmia, 64 underwent cardiac MRI. A total of 41 patients, who did not have any abnormality on baseline echocardiogram were included in the study. There was male preponderance (56.1%), with median age of 43 years. About 43.9% had syncope. Twenty-four-hour Holter study revealed a premature ventricular complex (PVC) burden of 26.3 ± 11.7%. MRI showed structural abnormalities in 51.2% of patients, which commonly included RV sacculations and aneurysms. Late gadolinium enhancement (LGE) was seen in six patients, which was mostly seen in RV free wall. Right ventricular (RV) systolic dysfunction was evident in 29.3%. About 9.8% fulfilled the criteria for arrhythmogenic RV cardiomyopathy (ARVC). Out of 23 patients with baseline abnormalities on ECHO, 87% had structural abnormalities on MRI, and 43.5% fulfilled the criteria for ARVC. Conclusions Additional imaging by cardiac MRI helps to identify structural abnormalities in 51.2% of patients with RVOT arrhythmias, even with normal baseline echocardiogram and electrocardiogram (ECG). It is useful tool to rule out ARVC in this subset of patients, and can help in increasing the diagnostic yield in the early stages.

Novel strategy of remote magnetic navigation-guided ablation for ventricular arrhythmias from right ventricle outflow tract

The optimized strategy to further increase the success rate of ablation for ventricular arrhythmias (VAs) from the right ventricular outflow tract (RVOT) is challenging. Recent studies have shown that the pulmonary sinus cusp (PSC) region may be the origin of certain RVOT VAs. We evaluated the efficacy of preferential ablation below the pulmonary valve (PV) and alternated radiofrequency delivery in the PSC using remote magnetic navigation (RMN). Sixty-five (65) consecutive patients experiencing VAs with RVOT-like appearance were included in this study. Mapping and ablation were preferentially performed below the PV. Ablation in the PSC would only be attempted when intensified ablation below the PV could not eliminate VAs. Finally, if ablation in the RVOT region failed, the aortic sinus cusp (ASC) would be mapped. Sixty-one (61) of 65 (93.8%) patients achieved procedural success. Except 7 cases of which the VAs were ablated in the ASC, the rest 54 VAs were thought to be originate from the RVOT region. Fifty (50) of 54 VAs were successfully ablated below the PV, and in the presence of a local special signal in the bipolar electrogram a more aggressive ablation was required. Subsequent ablation in the PSC with assistance of the RMN system achieved success in the remaining 4 patients. No complications occurred in this study. Our strategy of using RMN-guided ablation below the PV for VAs of RVOT origin was proved to be effective. PSC mapping and ablation using a magnetic catheter may provide the optimal strategy for treating these types of arrhythmias.

The ratio of main pulmonary artery to ascending aorta diameter is associated with the right ventricular outflow tract ventriculararrhythmias.

Although outflow tract (OT) ventricular arrhythmias (VAs) are generally regarded as benign, the relationship between circulation pressure and VAs has received considerable attention in recent years. Previous studies have shown that the ratio of main pulmonary artery (MPA) to ascending aorta (AA) diameter is associated with pulmonary pressure. Here, we investigated whether an elevated MPA/AA ratio is associated with right ventricular OT (RVOT) VAs. A total of 67 patients with OT VAs (47 patients with RVOT and 20 patients with LVOT) who underwent cardiac multidetector computed tomography and radiofrequency ablation were enrolled in this study. MPA and AA diameters were measured at the level of the bifurcation of the pulmonary artery. According to the MPA/AA ratio, patients were further divided into two groups: the MPA/AA ratio abnormal group (n = 19), which is defined as MPA/AA ratio ≥ 0.9, and the MPA/AA ratio normal group (n = 48) consisting of patients with an MPA/AA ratio < 0.9. Patients with RVOT VAs exhibited an elevated MPA/AA ratio (0.84 ± 0.11 vs. 0.75 ± 0.11, p = 0.006). Furthermore, this MPA/AA ratio was shown to be an independent predictor for RVOT VAs (p = 0.013, 95% confidence interval: 1.016-1.145), with an abnormal MPA/AA ratio increasing the odds of RVOT VAs 5.1-fold in patients with OT VAs. Patients with RVOT VAs exhibited significantly higher MPA/AA ratios compared with those LVOT VAs. The MPA/AA ratio was showed to be an independent predictor RVOT VAs.

Contact- versus noncontact-guided ablation of the right ventricular outflow tract arrhythmias: A propensity score matched analysis.

There are unique advantages and disadvantages in the choice of contact mapping (CM) versus noncontact mapping (NCM) systems during ablation of right ventricular outflow tract (RVOT) arrhythmias. This study compared acute procedural success and clinical outcomes in matched patients undergoing CM- versus NCM-guided RVOT ablation. A total of 167 consecutive patients with idiopathic RVOT ventricular arrhythmias underwent NCM- or CM-guided ablation. Propensity scoring was used to match each patient undergoing NCM-guided ablation to one control patient undergoing CM-guided ablation. A total of 120 patients were included in this final analysis. If initial ablation was acutely unsuccessful in either group, patients crossed over to the other group. Ablation was acutely successful in 47 of 60 (78.3 %) patients in the NCM group and 55 of 60 (91.7%) in the CM group (P=.002). Thirteen NCM patients required CM and two CM patients crossed over to utilize NCM (P=.002). Procedural duration, fluoroscopy time, and dose in NCM were greater than that in CM (P<.05, respectively). However, procedural complications were not different between two groups. During a mean follow-up of 51 ± 20.6 months, 51 of the 60 NCM patients remained free of arrhythmia, while 48 of the 60 CM patients had no recurrent arrhythmias (P=.47). Contact mapping, compared to NCM, is the superior initial technique to guide RVOT arrhythmia ablation due to a higher procedural success without the need to switch to alternative mapping techniques and shorter procedural and fluoroscopic times.

Right ventricular outflow tract low-voltage areas identify the site of origin of idiopathic ventricular arrhythmias: A high-density mapping study.

Electronatomical mapping allows direct and accurate visualization of myocardial abnormalities. This study investigated whether high-density endocardial bipolar voltage mapping of the right ventricular outflow tract (RVOT) during sinus rhythm may guide catheter ablation of idiopathic ventricular arrhythmias (VAs). Forty-four patients (18 males, mean age: 38.1 ± 13.8 years) with idiopathic RVOT VAs and negative cardiac magnetic resonance imaging underwent a stepwise mapping approach for the identification of the site of origin (SOO). High-density electronatomical mapping (1096.6 ± 322.3 points) was performed during sinus rhythm and identified at least two low bipolar voltage areas less than 1 mV (mean amplitude of 0.20 ± 0.10 mV) in 39 of 44 patients. The mean low-voltage surface area was 1.4 ± 0.8 cm2 . Group 1 consisted of 28 patients exhibiting low-voltage areas and high-arrhythmia burden during the procedure. Pace match to the clinical VAs was produced in one of these low-voltage areas. Activation mapping established the SOO at these sites in 27 of 28 cases. Group 2 comprised 11 patients exhibiting abnormal electroanatomical mapping, but very low-arrhythmia burden during the procedure. Pace mapping produced a near-perfect or perfect match to the clinical VAs in one of these areas in 9 of 11 patients which was marked as potential SOO and targeted for ablation. During the follow-up period, 25 of 28 patients from group 1 (89%) and 7 of 9 patients from group 2 (78%) were free from VAs. Small but detectable very low-voltage areas during mapping in sinus rhythm characterize the arrhythmogenic substrate of idiopathic RVOT VAs and may guide successful catheter ablation.

Late fractionated potentials in catheter ablation for right ventricular outflow tract ventricular arrhythmias.

Endocardial late fractionated potentials during sinus rhythm mapping may reflect abnormal "subendocardial" substrates associated with right ventricular outflow tract (RVOT) ventricular arrhythmias (VAs). The aim of this study was to explore the clinical outcomes of catheter ablation guided by these late fractionated potentials for RVOT VAs in patients without structural heart disease. From January 2016 to March 2018, 28 patients underwent catheter ablation for RVOT premature ventricular contractions (PVCs) or ventricular tachycardia (VT), guided by the EnSite NavX or Velocity V5.0 three-dimensional mapping system (Abbott, St. Paul, MN, USA). Among them, 10 patients (35.7%) were found to have endocardial late fractionated potentials during sinus rhythm mapping (Group 1). Group 2 was composed of 18 patients in whom no endocardial late fractionated potentials were seen. The burden of VAs, acute procedural success, and 3-month clinical outcomes were analyzed. The average duration of late fractionated potentials after the end of QRS during sinus rhythm mapping in group 1 was 45.00±17.15 ms. Baseline demographics and morphology and burden of PVCs were similarly distributed between both groups. Group 1 had higher acute procedural success compared to group 2 (100%vs 66.7%; P=.039). Moreover, at 3-month follow-up, group 1 had lower total PVCs (49 (1-5986) versus 4316 (1-23231); P=.048), PVC burden (0% (0-5.9) vs 4.3% (0-18.9); P=.055), and higher clinical success (100%vs 55.6%; P=.025) compared to group 2. The identification and elimination of endocardial late fractionated potentials during sinus rhythm mapping could improve the acute success and short-term outcomes of ablation for RVOT VAs.

Analysis on the factors related to the immediate success rate of radiofrequency catheter ablation on patients with idiopathic right ventricular outflow tract ventricular arrhythmia

Objective: To analyze the clinical characteristics of patients with idiopathic right ventricular outflow tract (RVOT) ventricular arrhythmias (VA) and factors related to the immediate success rate of radiofrequency ablation. Methods: Patients diagnosed as idiopathic RVOT arrhythmia in Fuwai Hospital from February 2009 to January 2013 were retrospectively screened. Patients with structural heart disease or inherited arrhythmia were excluded. All patients underwent endocardial electrophysiological study and radiofrequency catheter ablation. Baseline clinical and operation records were collected and analyzed. Immediate success rate was defined as no inducible ventricular arrhythmia by isoprinosine and electrophysiological induction at the end of ablation. The origins of idiopathic RVOT were classified as septal, anterior, posterior, free wall site, epicardial and RVOT-aorta root site. Results: A total of 468 patients were finally included, and the age was (40.4±13.3) years old and 60.5%(283/468) patients were female. Immediate radiofrequency success rate was 89.3%(418/468). Patients were divided into ablation success group (n=418) and ablation failure group (n=50). Percent of female patients and patients with interventricular septal origin was significantly higher in the ablation success group than in ablation failure group (261(62.4%) vs. 22 (44.0%) , P=0.01, and 233(55.7%) vs. 18(36.0%), P=0.005), while percent of patients with epicardial origin was significantly lower in the ablation success group than in ablation failure group (17(4.1%) vs. 11(22.0%), P<0.001). Immediate success rate was the highest for patients with the septal origin and the lowest for patients with epicardial origin (92.8%(233/251) vs. 60.7%(17/28), P<0.05). Multivariate analysis showed that the origin site of VAs was the most important independent factor related to the success rate of ablation. Compared with the septal origin patients, patients with RVOT-aorta root and epicardial origin VAs faced with 1.82-fold and 8.26-fold increased risk of failed ablation, respectively (OR=2.82, 95%CI 1.05-7.57, and OR=9.26, 95%CI 3.60-23.86). Sex category was not the independent risk factor for failed ablation(OR=1.76, 95%CI 0.93-3.33, P=0.08) . Conclusions: The immediate success rate of radiofrequency catheter ablation for idiopathic RVOT ventricular arrhythmia is relative high, however, immediate success rate of radiofrequency catheter ablation is relatively low for patients with epicardial and RVOT-aorta root origin arrhythmia and VAs origin is an independent risk factor of immediate ablation success rate.

The autonomic neural mechanism of right ventricular outflow tract tachycardia.

Ventricular tachycardia (VT) and ventricular premature complexes (VPCs) originating from the right ventricular outflow tract (RVOT) are generally considered as benign arrhythmias, with ECG morphology showing LBBB pattern and inferior axis. Pathogenic mechanisms in the genesis of RVOT VT/VPC remain largely unknown. We aimed to investigate the neural mechanism in RVOT ventricular arrhythmias in canine model. Twelve mongrel dogs (13.7 ± 1.3 kg, 5 male dogs) were studied through midline thoracotomies. High-frequency stimulation (HFS) was applied to the proximal pulmonary artery (PA) to induce RVOT VT/VPC. An EnSite Array and a mapping catheter were used for electroanatomical mapping. The RVOT and PA were surgically excised for immunohistochemistry studies, including tyrosine hydroxylase (TH) stain for sympathetic nerves and choline acetyltransferase (ChAT) stain for parasympathetic nerves. In nine (75%) out of twelve dogs, HFS of the proximal PA induced RVOT VT/VPC. The density of TH-positive nerves was significantly higher than that of ChAT-positive nerves (6803 ± 700 vs. 670 ± 252 μm2/mm2, p < 0.001). Furthermore, the density of TH-positive nerves was also significantly higher in the VT/VPC origin sites than that in the non-origin sites (18,044 ± 2866 vs. 5554 ± 565 μm2/mm2, p = 0.002). Catheter ablation of the proximal PA eliminated the inducibility of RVOT VT/VPC successfully. HFS of the proximal PA could induce RVOT VT/VPC. The sympathetic nerves were densely innervated to the origin of RVOT VT/VPC, indicating the critical role of sympathetic hyperactivity in the initiation and perpetuation of RVOT VT/VPC.

Centrifugal Wave Front Propagation Speed for Localizing the Origin of Ventricular Arrhythmias: Investigation Using a New Ultra-High-Resolution MappingSystem.

The aim of this study was to assess the use of wave front propagation speed on a right ventricular map for determining the earliest activation site as the origin of outflow tract ventricular arrhythmias (VAs). VAs with centrifugal right ventricular outflow tract (RVOT) activation can be from an RVOT focus or a focus outside the RVOT. This prospective observational study included 23 patients with idiopathic outflow tract VAs. Mapping of theRVOT was performed using a new ultra-high-resolution electroanatomic mapping system. The wave front propagation speed was estimated from the area surrounded by a propagated wave front at 5, 10, 15, and 20 ms after the earliest activation. VAs disappeared following ablations in the RVOT in 15 patients (RVOT origin). The remaining 8 patients hadVAs of non-RVOT origin determined by ablation success at another site or ablation failure. The areas surrounded by apropagated wave front were significantly smaller in VAs of RVOT origin than non-RVOT VAs at 5 ms (1.0 [0.7 to 1.1]cm2vs. 2.2 [1.6 to 4.4] cm2), 10 ms (1.9 [1.4 to 2.2] cm2 vs. 4.5 [3.2 to 5.8] cm2), 15 ms (3.2 [2.3 to 4.4] cm2 vs. 7.1[6.3to 9.8] cm2), and 20 ms (5.0 [3.0 to 6.6] cm2 vs. 9.8 [9.3 to 14.8] cm2). A propagated area of<5.0 cm2 at 15 ms predicted RVOT VAs with 87% sensitivity, 100% specificity, and 91% predictive accuracy. VAs with slow wave front propagation speed on the right ventricular map indicate an RVOT origin.

Pulmonary sinus cusp mapping and ablation: A new concept and approach for idiopathic right ventricular outflow tract arrhythmias

Right ventricular outflow tract (RVOT) ventricular arrhythmias (VAs) may originate from the pulmonary sinus cusps (PSCs) far more frequently than previously recognized. The purpose of this study was to assess whether mapping and ablation in PSCs might be an appropriate first-choice treatment in unselected patients with idiopathic RVOT VAs. Ninety consecutive patients with VAs of RVOT-type origin were prospectively enrolled at our institution between August 2015 and September 2016. Pulmonary valve (PV) and PSCs were precisely localized by pulmonary arteriography. Activation and pace-mapping were performed in the PSCs and RVOT region below the PV, and ablation was preferentially performed in PSCs. In 81 patients (90%), earliest activation of VAs was found in PSCs, and ablation resulted in elimination of VAs without any additional ablation in the RVOT region underneath the PV. The best pace-map was obtained at successful ablation sites in PSCs in 96.3% of patients. In the remaining 9 patients, final successful ablation sites were in the aortic coronary cusps in 5 and at the lowest and most posterior part of the RVOT in 4. During mean follow-up of 15.2 ± 9.5 months, single procedural success rate was 96.7%. In this single-center, prospective study, a strategy based on PSC mapping and ablation eliminated 90% (81/90) of unselected idiopathic RVOT-type VAs with favorable mid-term effectiveness.

Pulmonary artery: A pivotal site for catheter ablation in idiopathic RVOT ventricular arrhythmias.

In patients without associated myocardial diseases, characterized by left bundle branch block and inferior axis morphologies, repetitive idiopathic right ventricular tachycardias and ventricular premature contractions typically arise from right ventricular outflow tract (RVOT). Accumulated evidences have shown that radiofrequency catheter ablation is a useful treatment for patients with RVOT ventricular arrhythmias (VAs). Interestingly, several medical centers have shown that pulmonary artery (PA) is a potential novel site for catheter ablation in RVOT-like VAs, particularly in patients where termination of RVOT VAs at the usual site fails. In this review, we comprehensively demonstrated that RVOT VAs were successfully terminated at the site of PA, analyzed the characteristics of surface electrocardiogram and endocardial potentials, and explored the underlying mechanisms for these cases.

Electrocardiographic differentiation of idiopathic right ventricular outflow tract ectopy from early arrhythmogenic right ventricular cardiomyopathy.

AimsThe differentiation between idiopathic right ventricular outflow tract (RVOT) arrhythmias and early arrhythmogenic right ventricular cardiomyopathy (ARVC) can be challenging. We aimed to assess whether QRS morphological features and coupling interval of ventricular ectopic beats (VEBs) can improve differentiation between the two conditions.Methods and ResultsTwenty desmosomal-gene mutation carriers (13 females, mean age 43 years) with no or mild ARVC phenotypic expression and 33 age- and sex-matched subjects with idiopathic RVOT arrhythmias were studied. All patients exhibited isolated monomorphic VEBs with left bundle branch block/inferior axis morphology. The predictive value of ectopic QRS morphology and coupling interval was evaluated. Five ectopic QRS features were significantly more common in desmosomal-gene mutation carriers than in idiopathic RVOT-ventricular arrhythmia patients: maximal QRS duration >160 ms (60 vs. 27%, P = 0.02), intrinsicoid deflection time >80 ms (65 vs. 24%, P = 0.01), initial QRS slurring (40 vs. 12%, P = 0.04), QS pattern in lead V1 (90 vs. 36%, P < 0.001), and QRS axis >90° in limb leads (60 vs. 24%, P = 0.01). In the multivariate analysis, intrinsicoid deflection time >80 ms [odds ratio (OR) = 9.9], QS pattern in lead V1 (OR = 28), and QRS axis >90° (OR = 5.7) remained independent predictors of early ARVC. The coupling interval did not differ between the two groups.ConclusionsIn patients with RVOT VEBs and no major electrocardiographic or echocardiographic abnormalities, the ectopic QRS morphology aids in the differential diagnosis between idiopathic RVOT arrhythmias and early ARVC.

Efficacy of radiofrequency catheter ablation of outflow tract ventricular arrhythmias in children

To explore the features of outflow tract ventricular arrhythmias (OTVA) in children and evaluate the efficacy and experiences of radiofrequency catheter ablation (RFCA). Data were collected and analyzed on 53 consecutive pediatric patients who underwent RFCA for OTVA from January 2012 to July 2015 in the First Hospital of Tsinghua University. These children included 34 male and 19 female, whose average age was (8±3) years and body weight was (33±13) kg. All the children met the indication criteria for RFCA of OTVA in children. Data were analyzed about the onset age, the forms and ablation efficacy and strategies of OTVA. The average age of onset was (8±4) years. Of these children, 68% (36/53) had frequent premature ventricular complex which was the main arrhythmia pattern.The proportion of 66%(35/53) were of right ventricular outflow tract (RVOT). The vast majority of RVOT ventricular arrhythmias originates from myocardium with in the first 1 cm beneath the pulmonary valve(89%, 31/35) or the septal region(77%, 27/35). The total acute success rate was 98%(52/53), the recurrence rate on follow-up was 10% (5/52) and the complications of the procedure was 2%(1/53). The X-ray exposure dose was(743±323) mGay·cm(2). However, for 6 of the children RFCA on both sides of outflow tract was necessary for success. OTVA in children originates mostly from RVOT. RFCA can be used for ablation of pediatric OTVA effectively and safely. In some cases, successful RFCA should be performed on both sides of outflow tract.

Right Ventricular Strain and Dyssynchrony Assessment in Arrhythmogenic Right Ventricular Cardiomyopathy: Cardiac Magnetic Resonance Feature-Tracking Study.

Analysis of right ventricular (RV) regional dysfunction by cardiac magnetic resonance (CMR) imaging in arrhythmogenic RV cardiomyopathy (ARVC) may be inadequate because of the complex contraction pattern of the RV. Aim of this study was to determine the use of RV strain and dyssynchrony assessment in ARVC using feature-tracking CMR analysis. Thirty-two consecutive patients with ARVC referred to CMR imaging were included. Thirty-two patients with idiopathic RV outflow tract arrhythmias and 32 control subjects, matched for age and sex to the ARVC group, were included for comparison purpose. CMR imaging was performed to assess biventricular function; feature-tracking analysis was applied to the cine CMR images to assess regional and global longitudinal, circumferential, and radial RV strains and RV dyssynchrony (defined as the SD of the time-to-peak strain of the RV segments). RV global longitudinal strain (-17±5% versus -26±6% versus -29±6%; P<0.001), global circumferential strain (-9±4% versus -12±4% versus -13±5%; P=0.001), and global radial strain (18 [12-26]% versus 22 [15-32]% versus 27 [20-39]%; P=0.015) were significantly lower and SD of the time-to-peak RV strain in all 3 directions were significantly higher among patients with ARVC compared with patients with RV outflow tract arrhythmias and controls. RV global longitudinal strain >-23.2%, SD of the time-to-peak RV longitudinal strain >113.1 ms, and SD of the time-to-peak RV circumferential strain >177.1 ms allowed correct identification of 88%, 75%, and 63% of ARVC patients with no or only minor CMR criteria for ARVC diagnosis. Strain analysis by feature-tracking CMR helps to objectively quantify global and regional RV dysfunction and RV dyssynchrony in patients with ARVC and provides incremental value over conventional cine CMR imaging.

0305 : Heterogeneous conduction properties in the pig right ventricle

The right ventricular outflow tract (RVOT) has a distinct embryological origin and is a common anatomical source of arrhythmias in the healthy and diseased myocardium. We hypothesised that specific RVOT activation and conduction properties may underlie the preferential RVOT origin of arrhythmias. Pig right ventricular (RV) wedge preparations were perfused via the left anterior descending and right coronary arteries. Electrical activation and conduction properties were obtained by optical mapping of the epicardial surface (di-4- ANEPPS 10μM) upon electrical stimulation of the preparation. Transmural needles were inserted in the RV free wall and RVOT and unipolar electrograms (EGMs) were recorded. Fiber orientation was obtained by diffusion tensor MRI. Regional mRNA expression was determined by RT-PCR and fibrosis was assessed histologically. Longitudinal and transverse conduction velocities were significantly reduced in RVOT compared to RV free wall (P<0.01). A different direction of propagation was observed in the RVOT compared to the RV free wall and a line of slowed propagation was found at the interface between the 2 regions. This was consistent with a 135±2° change in fiber orientation observed between the 2 regions within a restricted distance (<6cm). The RVOT showed more sites with fractionated EGMs (P<0.01) and more deflections per electrode (P<0.001) than the RV free wall. In line with these findings, a decreased expression of Scna5 and Gja1 was found in the RVOT compared to the RV free wall (P<0.001). Moreover, the RVOT was characterized by an upregulation of type I collagen mRNA, a higher collagen content (P<0.05) and the presence of fat infiltrations which were absent in the free wall. Conduction is slower in the pig RVOT and is associated with fractionated unipolar electrograms. Conduction slowing was related to (i) reduced connexin and sodium channel expression and (ii) region-specific structural properties which may generate a substrate for RVOT arrhythmias.