Posterior Right Ventricular Outflow Tract Research Articles

Usefulness of the synthesized 18-lead ECG in premature ventricular contractions from near the HIS bundle.

Isolated premature ventricular complexes (PVCs) are the most common arrhythmias observed in patients even if without structural heart disease.1 Although most PVCs originate from the right ventricular outflow tract (RVOT), there are some PVCs that originate near the HIS bundle.2 The synthesized 18-lead ECG consists of right-sided thoracic (V3R, V4R, V5R) and dorsal (V7, V8, V9) ECG leads derived from a mathematical calculation of the 12-lead ECG, and the detailed mathematical formula is shown in Figure 1. The synthesized 18-lead ECG has been reported to be effective for PVCs of an RVOT origin, but the rest remains to be elucidated.3 The aim of this study was to investigate the characteristics of the synthesized 18-lead ECG in patients with PVCs originating from near the HIS bundle. The synthesized 18-lead ECGs of 13 consecutive patients who underwent radiofrequency catheter ablation (RFCA) of idiopathic PVCs from near the HIS bundle at the Japan Community Healthcare Organization Osaka Hospital, Osaka General Medical Center, and Nara Prefectural Seiwa Medical Center from January 2018 to December 2020 were included in this retrospective analysis. The origin of the PVCs was identified by a cardiologist using a 3D mapping system (CARTO 3: Biosense Webster Inc or EnSite: Abbott Medical Inc). We analyzed the QRS morphology pattern of the synthesized 18-lead ECG analyzed in those patients. This study was approved by the Ethics Committee of each hospital in accordance with the Declaration of Helsinki. The synthesized 18-lead ECG and ECG characteristics in 13 patients with PVCs from near the HIS bundle are shown in Figure 2 and Table 1. The mean QRS duration of the ECG was 142.5 ± 26.9 ms. In 12 of 13 patients, a left bundle branch block pattern (92.3%) was present, and 11 of 13 patients had inferior axis deviation (84.6%). Regarding the right-sided chest leads of the synthesized 18-lead ECG, in all patients, a QS pattern in lead V5R (100%) was observed, and in 12 of 13 patients, a QS pattern in leads V3R, V4R, and V5R (92.3%) was present. A comparison showed that the synthesized ECGs recorded during sinus rhythm and during PVCs were not consistent, as shown in Table 2. Several studies have shown that identifying PVCs originating from the vicinity of the ventricular septum remains complicated,4 and it is difficult to identify the origin of PVCs originating from near the HIS bundle based on the characteristics of the 12-lead ECG. Noteworthy among our results was that there was a QS pattern in lead V5R in 100.0%. Igarashi et al reported that in the synthesized 18-lead ECG recorded by pace mapping in the outflow tract, a QS pattern in lead V5R was observed in about 80% at the right coronary cusp (RCC), about 20% in the posterior RVOT, and nothing at the other sites.3 Combining the above study3 with our results, a QS pattern in lead V5R might have been specific to PVCs originating from near the HIS bundle and RCC. QRS morphology changes after RFCA are often observed in patients with idiopathic PVCs.5 In such cases, the use of the synthesized 18-lead ECG's right-sided chest leads may assist in the re-mapping process. Regarding the mechanism of the QS pattern in lead V5R, in general the HIS bundle is anatomically closer to the RCC, and electrical conduction may propagate with a vector away from the right-sided chest leads such as lead V5R. Based on the characteristics of the ECG, only case 7 was considered to have a PVC from the HIS bundle. An identification of PVCs originating from near the HIS bundle or from the HIS bundle was attempted based on the characteristics of the synthesized ECG, but was not possible due to an insufficient number of cases. Although a 3D mapping system was used in this study, the distance between the HIS bundle and the ablation site was not measured, and it was considered necessary to include the distance in future studies. A QS pattern recorded in lead V5R of the synthesized 18-lead ECG was characteristic of PVCs originating from near the HIS bundle. This observation might assist in identifying the origin of PVCs during RFCA. H Kida, R Nakanishi, and N Ogasawara participated in the design of the study and coordination and helped draft the manuscript. All authors read and approved the final manuscript. We would like to express our gratitude to Mr. John Martin for his linguistic revision of the manuscript. All authors declare no conflicts of interest associated with this manuscript. This study was approved by the Ethics Committee of Japan Community Healthcare Organization Osaka Hospital, Osaka General Medical Center, and Nara Prefectural Seiwa Medical Center in accordance with the Declaration of Helsinki. Since this study was a retrospective study, we used the opt-out system according to the ethics guidelines on human medical research by the Japanese government.

Distinguishing Ventricular Arrhythmias Originating from the Posterior Right Ventricular Outflow Tract, or Near the Right Coronary Cusp or Near the His-Bundle

Differentiation of outflow tract ventricular arrhythmias (OT-VAs) which originate from the posterior right ventricular outflow tract (RVOT), right coronary cusp (RCC) or near the His-bundle are still a challenge until now. This study was aimed to develop a stepwise electrocardiogram (ECG) algorithm to distinguish their locations. Seventy-five consecutive patients with VAs successfully ablated from the posterior RVOT (n = 57), near the His-bundle (n = 5) or RCC (n = 13) were enrolled in our study. Measurements with highest diagnostic performance were chosen to develop a diagnostic algorithm. Of all these ECG measurements, the R-wave amplitude in lead I and V2S/V3R index showed the best diagnostic performance to discriminate these anatomical sites. The optimal ECG discriminators were different combination of lead I and V2S/V3R index as follows: the posterior RVOT, Lead I R-wave amplitude <0.65 mV and V2S/V3R index>1.5 (96.2% sensitivity, 69.6% specificity); the near the His-bundle, lead I R-wave amplitude ≥0.65 mV and V2S/V3R index>1.5 (100% sensitivity, 70% specificity); RCC, lead I R-wave amplitude<0.65 mV and V2S/V3R index ≤1.5 (52.9% sensitivity, 93.1% specificity). Sequential algorithmic application of these criteria resulted in an overall accuracy of 83% in predicting site of OT-VA origin. A predominantly positive R-wave in lead I is seen in OT-VAs originated near the His-bundle. A stepwise ECG algorithm of combination with R-wave amplitude in lead I and V2S/V3R index could localize the origins of OT-VAs from the posterior RVOT, near the His-bundle and the RCC with a high accuracy.

Unipolar voltage mapping criteria for right ventricular septum: Influence of the aortic root.

Unipolar voltage mapping through its wider "field of view" can identify substrate deeper to the endocardium on the right ventricular (RV) free wall and left ventricle. The reference value(s) for normal endocardial (ENDO) unipolar voltage (UNI) for the septal aspect of the right ventricle (RV) and the effect of the aortic root that is directly opposed to the posterior septal plane of the RV outflow tract (RVOT) have not been established. We performed detailed (185 ± 70, range 127-342 points) RV ENDO UNI maps in 9 patients without structural heart disease; 6 had magnetic resonance (MR) imaging; 5 were males; the mean age was 49 ± 11 years. For MR analysis, the location of the aortic root was defined and its effect on unipolar voltage determined. The UNI voltage on posterior RVOT was lower (mean 6.56 ± 2.33mV, 95% CI 6.08-7.05), compared to the rest of the septal aspect of RV (mean 8.33 ± 2.34mV, P<0.001, 95% CI 7.84-8.84). MR analysis confirmed that the lowest voltage region was opposite to MR-defined aortic root. Using a cutoff for UNI abnormality of 6.0mV for the posterior aspect of the RVOT opposite to the aortic root and 7.5mV for the rest of the septal aspect of the RV, there was no confluent area of unipolar abnormality in any patient. We defined normal ENDO UNI cutoffs as 7.5mV for the septal aspect of the RV with adjustment to 6.0mV over the posterior RVOT opposite to the aortic root.

Transient Elimination of Posterior Right Ventricular Outflow Tract Ectopy by Sternal Pressure

Ventricular ectopy (VE) originating in the right ventricular outflow tract (RVOT) is a common arrhythmia. Mechanisms triggering or eliminating VE from RVOT are not entirely understood. A patient with frequent, symptomatic VE underwent an electrophysiologic study: VE origin was mapped by NavX 3D navigation (St. Jude Medical, Inc., St. Paul, MN, USA). Incidental pressure applied manually to the sternum reproducibly eliminated VE for the time of exposure. Radiofrequency-ablation was successfully performed in the posterior RVOT. The mechanism resulting in VE suppression remains speculative, since a mechanical alteration of the substrate for VE in the posterior RVOT by sternal pressure seems unlikely. "Mechano-electrical feedback" might have been the mechanism operative in this case.

Ventricular tachycardia originating from the “Bermuda Triangle”

Summary Idiopathic ventricular tachycardia originates from the right ventricular outflow tract (RVOT) in the majority of cases, but origins from structures adjacent to the RVOT are well known. The proximity of the posterior RVOT, the aortic cusps and the distal coronary s inus can render localisation of the true arrhythmia origin challenging. Although the diagnostic accuracy of the 12-lead ECG in localising the arrhythmia origin is i mperfect, it can be helpful in clinical practice. We d escribe a 25-year-old woman with tachycardia recurrence after an initially successful radiofrequency ablation (RFA) in the RVOT. The recurrent tachycardia had a slightly different morphology, with a larger R-wave in V1/V2 and an earlier R/S transition. The arrhythmia exit site, which had been presumed to be located b etween the RVOT and the distal coronary sinus, had been altered by the first RFA, and the focus was permanently eliminated by ablation from both sites (RVOT and distal coronary sinus) during the second procedure.

Performance of surface electrocardiographic vectors in differentiating ventricular arrhythmia originating from coronary cusp, peri-pulmonic valve and right ventricular outflow tract

Introduction: Symptomatic outflow tract ventricular arrhythmia (OTVA), including ventricular tachycardia and premature ventricular complexes, can be readily treated with catheter ablation. Outflow tract anatomy is complex and differentiating aortic, pulmonary and subvalvular origin is important for planning approach to mapping and ablation. We investigated whether surface ECG characteristics of OTVA can accurately discriminate between right coronary cusp (RCC), peri-pulmonic valve (PV) and right ventricular outflow tract (RVOT) origin. Methods: Thirty-six consecutive patients (mean age 41±14 years, 13 male) undergoing catheter ablation for OTVA were studied. Site of OTVA origin were determined from intracardiac electrogram tracings, electroanatomical maps and ablation reports. Observers blinded to these results manually measured PVC waveform amplitude and duration from standard 12-lead ECG tracings. Measurements with highest diagnostic performance were modelled into an algorithm designed to discriminate between predefined sites of origin within the outflow tract. Results: Sites of successful ablation were anterior RVOT (n=6), posterior RVOT (n=4), PV (≤1cm below, at or above pulmonary valve, n=18) and RCC (n=8). RCC origin was best discriminated by lead I R-wave ≥ 1.5 mV AND V1 R-wave ≥2.0mV (PPV 39%, NPV 94%, accuracy 67%). Posterior RVOT origin was best discriminated by lead I R/(R+S) ≥ 0.1 AND V1 R-wave > 0mV (PPV 33%, NPV 96%, accuracy 81%). Anterior RVOT origin was best discriminated by V1 R-wave = 0mV AND aVR/aVL S-wave ratio > 1 (PPV 100%, NPV 94%, accuracy 94%). Origin from PV was best discriminated by lead II/III R-wave ratio ≤0.95 OR lead I R/(R+S) < 0.08 (PPV 68%, NPV 86%, accuracy 75%). Sequential algorithmic application of these criteria resulted in an overall accuracy of 80% in predicting site of OTVA origin. Conclusions: Application of simple surface ECG criteria in sequential algorithmic fashion can discriminate between coronary cusp, peri-pulmonic and RVOT origin of outflow tract ventricular arrhythmia.

Idiopathic ventricular arrhythmia originating from the para-Hisian area: Prevalence, electrocardiographic and electrophysiological characteristics

BackgroundWe investigated the prevalence and the electrocardiographic and electrophysiological characteristics of ventricular arrhythmias (VAs) originating from the para-Hisian area. MethodsAmong 250 patients with idiopathic VAs, 8 (3.2%) had an ablation site in the para-Hisian region. For comparison with right ventricular (RV) para-Hisian VAs (n=6), 27 patients with VAs originating from the posterior RV outflow tract (RVOT) were studied. ResultsPara-Hisian VAs had an R wave in leads I and aVL. The VAs originating from the site below the His bundle region were determined to have a superior axis (n=4, 50%). A His potential was recorded at the proximal bipole of the successful ablation site in 6 patients. RV para-Hisian VAs had a narrower QRS width (114±12ms vs. 139±12ms, P=0.003), as well as a higher incidence of R waves in lead aVL (83.3% vs. 0%, P<0.001) and QS waves in lead V1 (83.3% vs. 22.2%, P=0.004) compared to posterior RVOT VAs. A greater R wave amplitude in lead I (1.15±0.34mV vs. 0.34±0.18mV, P=0.001) and a smaller R wave amplitude in the inferior leads (0.68±0.23mV vs. 1.58±0.55mV, P<0.001), with a higher R wave amplitude ratio in leads II/III (4.2±2.0 vs. 1.1±0.2, P=0.01) were the major ECG characteristics. ConclusionsPara-Hisian VAs have distinctive electrocardiographic features and can be successfully eliminated without disturbance of atrioventricular conduction.

Supravalvular Arrhythmia

Supravalvar ablation has now been well documented to be the ideal mode for ablating specific forms of ventricular tachycardia, atrial tachycardia, and accessory pathways. A studied appreciation of the anatomy of the supravalvar region is a prerequisite for electrophysiologists to safely and effectively approach these arrhythmias. In addition, the consistent ability to correlate the recorded electrograms with fluoroscopic anatomy and intracardiac ultrasound images enhances the chance of successful elimination of supravalvar arrhythmias.