Origin Of Ventricular Arrhythmias Research Articles

Ventricular parasystole as a new indicator suggesting ventricular arrhythmias in cardiac sarcoidosis

Abstract Background In cardiac sarcoidosis (CS), it is considered that inflammation occurs in localized areas such as the basal septum. Inflammation has been suggested to be associated with ventricular fibrillation (VF). Meanwhile, ventricular parasystole is strongly associated with VF in non-ischemic cardiomyopathy. However, the relationship between CS and ventricular parasystole remains unclear. Purpose The purpose is to examine the frequency of parasystole in cases of VF and ventricular tachycardia (VT) in CS, and whether there is a correlation between the inflammatory activity of sarcoidosis and the origin of ventricular parasystole. Methods We evaluated ventricular arrhythmias (VA) in a cohort of 213 consecutive cases diagnosed with CS from 1989 to 2021 (median age 69 years, 104 males, median LVEF 36%) in our center. We investigated parasystole in cases that developed VA, using 5,313 electrocardiograms, 94 Holter electrocardiograms, and 3,174 ICD interrogation records. Classic parasystole is defined as three ventricular ectopic beats with the same morphology at a fixed interval but different coupling intervals (CI) in a 10-second continuous ECG. A new definition of parasystole requires two ventricular ectopic beats with a CI difference of more than 120ms. We also investigated the correlation of the inflammation site with ECG morphology. Results VAs were observed in 95 individuals (33.7%), and 22 developed VF (23.2%). In the VF group, parasystole was observed in 12 of 22 individuals (classic: 5, new: 7), and in the VT group observed in 20 of 73 individuals (classic: 5, new: 15), with parasystole being significantly more frequent in the VF group (P=0.018) and classic parasystole (P=0.033). In VF patients with recorded 12-lead ECGs of parasystole, the inflammation site on PET within 3 months of the VA and PVC origin matched in all 4 out of 4 cases, but no VF starting from ventricular parasystole ectopic beats was recorded. Conclusion Ventricular parasystole was detected in 54.5% of CS patients with VF. There is a possibility that the presence of parasystole and the inflammatory activity in the CS can predict the occurrence of VF.

Study on the feasibility of distinguishing ventricular and pre-excited arrhythmia rhythms by a new algorithm

BackgroundThe differentiation and diagnosis of ventricular tachycardia (VT) and pre-excited tachycardia (PXT) remains a challenging task, especially when typical AV dissociation is not present. The purpose of this article is to study the feasibility of a new theoretical algorithm for identifying ventricular arrhythmias (VA) and pre-excited arrhythmias (PA) rhythms (which can be used to distinguish VT from PXT, etc.). MethodThis study involved the deduction of a new algorithm by combining knowledge of cardiac anatomy, vectorcardiography, and cardiac electrophysiology. The new algorithm evaluated the diagnostic value through intracardiac electrophysiology in 205 cases of VA and PA. The new algorithm diagnoses VA based on the following 4-step process:1.The QRS complex in leads II, III, and aVF shows a unidirectional R wave, and lead aVR shows a QS pattern.2.S waves are predominant in two or more of leads I, aVF, and V6.3.Lead V2 shows ≥3 phase waves or returning branch notching (note: returning branch refers to the band of QRS complexes returning to the baseline).4.Lead V5 shows a negative wave in the initial portion or returning branch notching.If none of these criteria are met, the diagnosis is PA. The diagnostic value of the new algorithm is compared with the Steurer algorithm and the Vereckei algorithm (diagnosed based on the QRS waveform characteristics of the two algorithms during electrophysiological verification, excluding the diagnosis of atrioventricular dissociation). ResultsThe new algorithm showed significant advantages in terms of AUC value (0.83 vs. 0.61 vs. 0.57), sensitivity (83.6 % vs. 23.3 % vs. 24.8 %), and accuracy (82.9 % vs. 48.3 % vs. 46.3 %) compared to the Steurer algorithm and Vereckei algorithm based on QRS waveform characteristics for diagnosing VA (137 cases) and PA (68 cases). This indicates that the new algorithm is more accurate in identifying idiopathic VA. While there was a significant difference in specificity between the New algorithm and Steurer algorithm (82.3 % vs. 98.5 %, p < 0.05), the difference with Vereckei algorithm (82.3 % vs. 89.7 %) was not significant.In the New algorithm, the sensitivity and specificity for each step are as follows:-Step 1: Sensitivity 34.3 %, Specificity 94.1 %.-Step 2: Sensitivity 24.1 %, Specificity 98.5 %.-Step 3: Sensitivity 18.3 %, Specificity 100 %.-Step 4: Sensitivity 6.6 %, Specificity 89.7 %.Step 1 had the highest AUC value, indicating the best overall diagnostic performance among all steps. Step 2 and Step 3 also performed well, while Step 4 had relatively poorer diagnostic performance. ConclusionThe new algorithm is suitable for identifying the origin of VA and PA rhythms.

Unfolding the transition ratio: insight into the diagnostic criteria for the diagnosis of the origin of outflow tract ventricular arrhythmias

Abstract Background algorithms for the diagnosis of the site of origin of ventricular outflow tract arrhythmias (OTVA) share the rationale that more posterior structures (LVOT) produce a greater vector approaching the precordial leads than anterior structures (RVOT), i.e. R waves in V1-V3 of greater amplitude and duration, a transition generally earlier than the QRS in sinus rhythm (SR), and vice-versa. Methods in a retrospective cohort of 45 patients (53.3% LVOT, 46.7% RVOT) with OTVA (left bundle branch block morphology, transition in lead V3, absence of conduction aberrancy in SR, who underwent successful catheter ablation were retrospectively analyzed, comparing the diagnostic yield of the main literature criteria. a) The V2 transition ratio, (TR) calculated with the formula [(R\R+S)PVC : (R\R+S)SR] (LVOT if &amp;gt; 0.6) [1]. b) The V1-V2 S-Rd, calculated as [(V1S + V2S) – (V1R + V2R)] (LVOT if &amp;lt; 1.625) [2]. c) The V2S\V3R amplitude ratio (LVOT if &amp;lt; 1.5) [3]. d) The transition zone index (TZI), obtained by subtracting the transition zone of the PVC with that of the SR (LVOT if &amp;lt; 0) [4]. We extended the use of these criteria to the precordial leads V1 to V3; for TR the equation was applied to amplitude as well as duration measurements. Results Comparison of PVC QRS morphology with that of SR. 1. The diagnostic accuracy of the TR showed incremental values moving from lead V1 to V3, both using amplitude and duration measurements; compared to the modest accuracy of the V2 TR (AUC 0.630, 0.727), the V3 TR (LVOT if &amp;gt; 1) showed an accuracy of 85.3% (AUC 0.804, 0.855). 2. Simplifying the complex TR equation, comparing R or S waves of the PVC with those of the SR, we again found incremental values of accuracy moving from lead V1 to V3, with better results for the SVT\SSR compared to the RVT\RRS; the V3 SVT\SRS) (LVOT if &amp;lt; 1) showed an accuracy of 86.6% (AUC 0.917). 3. The TZI showed in our series a lower diagnostic yield compared to that of the literature (AUC 0.748, accuracy 73.3%) Comparison of PVC QRS morphology between two contiguous leads: 4. Compared to the V1-V2 S-Rd (AUC 0.830), the V2-V3 S-Rd (AUC 0.855), calculated as [(V2S + V3S) – (V2R + V3R)] showed greater accuracy (82.2%). 5. Similarly, compared to the V1S\V2R amplitude ratio (AUC 0.774), the V2S\V3R (AUC 0.930) showed the greatest accuracy (88.8%, with a more balanced sensitivity and specificity moving the cut-off for the diagnosis of origin from LVOT to &amp;lt; 2), resulting the criterion with the highest diagnostic yield. Conclusions variables that compare the morphology of the QRS of the PVC of two contiguous leads have greater accuracy than those that compare the morphology of the QRS of the PVC with that of the SR, with greater diagnostic yield when applied from lead V1 to V3; the V2S\V3R ratio represents the best criterion, with high sensitivity, like the V3 transition ratio; the simple ratio (SVT\SSR) can virtually replace the more complex TR, with similar accuracy but high specificity.

Catheter ablation of papillary muscle arrhythmias: procedural characteristics and long term outcome

Abstract Background Ventricular arrhythmias (VA) originating from the papillary muscles can occur both in patients with and without structural heart disease. Although catheter ablation is the treatment of choice, ablation success remains challenging and long-term outcomes for this origin of VA are still unsatisfactory. Methods and Results All patients undergoing catheter ablation for premature ventricular contractions or ventricular tachycardia between june 2009 and november 2022 were analyzed. 66 patients (26 female (39%), mean age 60±15 years) undergoing catheter ablation of VA originating from the papillary muscle were identified. 21/66 (32%) patients had a reduced or mildly reduced left ventricular ejection fraction at time of initial presentation. While mitral valve regurgitation was present in 32/66 (48%) patients, mitral valve prolapse was observed in only 2/66 (3%) patients. 6/66 (9%) patients presented with non-sustained ventricular tachycardia (VT) and 1/66 (2%) patient presented with sustainend VT prior to catheter ablation. 61/66 (92%) patients underwent ablation of PVCs of the left ventricular papillary muscles (22/66 (33%) patients anterolateral; 39 (59%) patients posteromedial). 5/66 patients underwent ablation of premature ventricular complex (PVC) originating from the papillary muscles of the right ventricle. In 13/66 (19.7%) patients only a retrograde approach was used, in 26/66 (39.5%) patients a retrograde and an additional transeptal approach and in only 10/66 (15.2%) patients solely a transeptal approach. Mean PVC QRS duration was 152.5 ± 3.5 msec. Ablation was acutely successful in 44/66 (67%) patients. Mean procedure time was 145.8 ± 63.7 minutes and mean number of radiofrequency applications was 21.3 ± 16.7 (25 to 55 Watts, 37764.2 ± 27824.1 Joules). Overall, procedural complications occurred in 4/66 (6%) patients Follow up data were obtained from Holter ECGs, review of medical records, patient consultation, or via structured follow-up within the prospective TRUST registry. All information was combined to assess recurrence of PVC/VT. Recurrence of VA originating from the papillary muscles occurred in 11/66 (17%) patients. 9/66 patients (14%) underwent re-ablation due to recurrence of VA originating from the papillary muscles after previous ablation procedures. Conclusion Catheter ablation of papillary muscle arrhythmias is associated with a single procedural success rate of 67% with a procedural complication rate of 6%. 14% of patients underwent re-ablation due to recurrence of papillary muscle arrhythmias.

Activation pattern of the coronary sinus facilitates the differentiation for ventricular outflow tract arrhythmias.

The accuracy of surface ECG algorithms for predicting the origin of outflow tract ventricular arrhythmias (OT-VAs) might be questioned. Intracardiac electrograms recorded at anatomic landmarks could provide new predictive insights. We aim to evaluate the efficacy of a novel criterion utilizing the activation pattern of the coronary sinus (CS) in localizing OT-VAs, including VAs originating from the right ventricular outflow tract (RVOT), endocardial left ventricular outflow tract (Endo-LVOT), and epicardial left ventricular outflow tract (Epi-LVOT). We measured the ventricular activation time of the mitral annulus (MA) from the onset of the earliest QRS complex of VAs to the initial deflection over the isoelectric line at local signals, namely the QRS-MA interval. The activation at 3 and 12 o'clock of the MA was recorded as the QRS-MA3 and QRS-MA12 intervals, respectively. Their predictive values were compared to previous ECG algorithms. A total of 68 patients with OT-VAs were enrolled (51 for development and 17 for validation). From early to late, the ventricular activation sequences at MA12 were as follows: Epi-LVOT, Endo-LVOT, and RVOT. In LBBB morphology OT-VAs, the QRS-MA12 interval was significantly earlier for LVOT origins than RVOT origins. In the combined cohort of development and validation cohort, a cut-off value of ≤10 ms predicted the LVOT origin with a sensitivity of 100% and specificity of 78%. The QRS-MA12 interval ≤ -24 ms additionally predicted epicardial LVOT sites of origin. The QRS-MA interval could accurately differentiate the OT-VAs localization.

Prevalence and electrocardiographic and electrophysiological characteristics of idiopathic ventricular arrhythmias originating from the septal left ventricular summit.

The left ventricular summit (LVS) is the highest point on the epicardial surface of the left ventricle. A part of the LVS that is located between the left coronary arteries (lateral-LVS) is one of the major sites of idiopathic ventricular arrhythmia (VA) origins. Some idiopathic epicardial VAs can be ablated at endocardial sites adjacent to the epicardial area septal to the lateral-LVS (septal-LVS). This study examined the prevalence and electrocardiographic and electrophysiological characteristics of septal-LVS VAs. We studied consecutive patients with idiopathic VAs originating from the LVS (67 patients) and aortic root (93 patients). Based on the ablation results, among 67 LVS VAs, 54 were classified as lateral and 13 as septal-LVS VAs. As compared with the lateral-LVS VAs, the septal-LVS VAs were characterized by a greater prevalence of left bundle branch block with left inferior-axis QRS pattern, later precordial transition, lower R-wave amplitude ratio in leads III to II, lower Q-wave amplitude ratio in leads aVL to aVR, and later local ventricular activation time relative to the QRS onset during VAs (V-QRS) in the great cardiac vein. The electrocardiographic and electrophysiological characteristics of the septal-LVS VAs were similar to those of the aortic root VAs. However, the V-QRS at the successful ablation site was significantly later during the septal-LVS VAs than aortic root VAs (p < .0001). The precordial transition was significantly later during the septal-LVS VAs than aortic root VAs (p < .05). Septal-LVS VAs are considered a distinct subgroup of idiopathic VAs originating from the left ventricular outflow tract.

Mapping and ablation of ventricular arrhythmias arising from the left ventricular summit.

The left ventricular summit (LVS) refers to the highest portion of the left ventricular outflow tract (LVOT). It is an epicardially delimited triangular area by the left coronary arteries and the coronary venous circulation. Its deep myocardium correlates closely with the left coronary cusp, aortic-mitral continuity, and right ventricular outflow tract (RVOT), complicating the anatomical relationship. Ventricular arrhythmias (VAs) originating from this area are common, accounting for 14.5% of all VAs origin from left ventricle. Specific electrocardiogram (ECG) characteristics may assist in locating LVS-VAs pre-procedure and facilitate procedure planning. However, catheter ablation of LVS-VAs remains challenging because of anatomical constraints. This paper reviews the recent understanding of LVS anatomy, concludes ECG characteristics, and summarizes current mapping and ablation methods for LVS-VAs.

Mid-term outcome of catheter ablation of idiopathic non-outflow tract ventricular arrhythmias

BackgroundCatheter ablation is recommended in patients with frequent and symptomatic ventricular arrhythmias (VAs) in an otherwise normal heart. Right or left outflow tract (OT) are the most common origins, and catheter ablation is highly effective with low complication rates. However, outcome of catheter ablation of VAs other than the OT (non-OTVAs) is limited. The aim of this single-center study was to assess the safety and mid-term outcome of catheter ablation for non-OTVAs.Method and ResultsFrom 2013 to 2018, 251 patients who underwent catheter ablation for idiopathic non-OTVAs were enrolled and grouped according to the origins including His-Purkinje system (HPS, n = 108), papillary muscle / moderator band (PM/MB, n = 47), tricuspid annulus (TA, n = 70), and mitral annulus (MA, n = 26), 244 (97.2%) had acute elimination of VAs. The time of VAs recurrence of the single procedure was 1.69 (0.12,9.72) months, with 66% occurring within the first 3 months. The recurrence rate was significantly higher in the PM/MB group than in the TA (p = 0.025) and MA groups (p = 0.023). The single procedure success rate in all patients was 70.1%, in which 66.7%, 59.6%, 80%, and 76.9% were achieved in the HPS, PM/MB, TA, and MA groups, respectively (p = 0.284). After multiple procedures, the total success rate was 76.5% at the follow-up of 4.38 ± 2.42 years. The rate was significantly lower in the PM/MB group than in the TA group (p = 0.035). In subgroup analysis, no significant difference was observed in the recurrence rate of single procedure in patients with different VA origins within the PM/MB (log-rank test, p = 0.546).ConclusionDespite a certain percentage of recurrences observed in the mid-term follow-up, catheter ablation remained feasible and effective for idiopathic non-OTVAs.

Localizing the Origin of Idiopathic Ventricular Arrhythmias From ECG Using a Recurrent Convolutional Neural Network With Attention

Localizing the Origin of Idiopathic Ventricular Arrhythmias From ECG Using a Recurrent Convolutional Neural Network With Attention

Differentiating Origins of Outflow Tract Ventricular Arrhythmias: The Correction of Transitional Zone Index Is Not Superior to the Original One

Introduction: Our team once proposed a correction of transitional zone index (CTZI) based on the transitional zone index (TZI) in view of achieving a more precise prediction of outflow tract ventricular arrhythmia (OTVA). The predictive accuracy of these two electrocardiogram (ECG) algorithms has not been validated and compared. The purpose of this study was to compare the predictive accuracy of TZI and CTZI in a much larger population with idiopathic OTVA. Methods: The predictive accuracy of TZI and CTZI was compared in 695 individuals with idiopathic premature ventricular complex or ventricular tachycardia which exhibited a left bundle branch block pattern and inferior axis QRS morphology. Receiver operating characteristic curve analysis, decision curve analysis, and calibration curve were used to compare the predictive accuracy of TZI and CTZI. Results: TZI and CTZI manifested the similar area under the curve. While a TZI of <0 predicted a left ventricular outflow tract (LVOT) origin with a high specificity of 88.2% but a low sensitivity of 67.1%, a CTZI of <0 yielded a high sensitivity of 84.3% but a low specificity of 59.5% in the overall analysis. Similar results were yielded in the sub-analysis of participants with a precordial transition occurring at lead V3. In the sub-analysis of participants with a TZI = 0, CTZI demonstrated a bit higher but not satisfactory predictive accuracy than TZI. Conclusion: Based on the scientific spirit of self-criticism and seeking truth from facts, our team disproves the correction of TZI proposed previously.

Abstract 16985: Spatial Accuracy of Non-Invasive Activation Mapping Modalities for Complex Ventricular Arrhythmias: A Direct Comparison of Electromechanical Wave Imaging (EWI) Using High Frame Rate Transthoracic Echocardiography and Electrocardiographic Imaging (ECGi) With Cardiac CT

Background: Non-invasive identification of the site of origin (SOO) of ventricular arrhythmias is vital in informing ablation strategy. ECGi is an established method to generate 3D activation maps with a multielectrode vest combined with cardiac CT. EWI is an emerging echocardiography based modality that provides a low cost &amp; non-ionizing mapping alternative. Hypothesis: EWI more precisely localises SOO of Complex Ventricular Ectopy (VEs) &amp; intramural location than commercial ECGi. Aim: Compare spatial accuracy of EWI and ECGi to estimate SOO and validate against contact mapping. Methods: VE-ablation patients underwent preprocedural EWI &amp; ECGi to estimate SOO on the AHA segment-model. A commercial ECGi system with cardiac CT was used for reconstruction of epicardial VE activation maps. EWI was performed using a research ultrasound acquiring B-mode and high frame rate (2000fps) images with simultaneous ECG. Local electromechanical activation was defined as time-point of the downward zero-crossing on the incremental axial strain curve (250 strain curves/view) and displayed on 3D rendered maps. The site of earliest activation &amp; successful VE ablation was defined as ground truth for VE SOO. Results: 10 patients were enrolled: 50% male, age 40.8 +/- 18.1 years, LV EF 41+/-15%, 50% with scar on MRI. CT ECGi correctly identified the VE AHA segment in 8/10 (80%) cases (misclassified 2 papillary muscle (PM) VEs) but did not afford transmural localization. After excluding 1 patient with insufficient VE’s for EWI, EWI correctly identified the VE-SOO segment in 8/9 (88%) cases locating 2 subepicardial, 2 septal intramural &amp; 3 VEs at the base or intramural segment adjacent to a PM. It misclassified 1 PM VE. Conclusion Both EWI &amp; ECGI identified the VE-SOO segment in at least 80% of cases irrespective of presence of scar. EWI also correctly determined the transmural VE origin which cannot be located using commercial ECGI. This has important implications in planning ablation procedures.

Abstract 18177: Novel Pre-Operative Non-Invasive Computational 12-Lead ECG Mapping to Facilitate Surgical Ablation of Ventricular Arrhythmias

Background: In patients undergoing cardiac surgery who have ventricular arrhythmias (VAs) such as VT, VF, or PVCs, concurrent surgical ablation is an attractive therapeutic strategy. However, electrophysiologic mapping systems are not routinely available in the OR and it may be difficult to localize the VA origin. We developed a workflow incorporating novel 12-lead ECG computational model-based mapping to localize VAs. Hypothesis: We hypothesized that use of pre-operative computational ECG mapping can help guide surgical ablation of VAs in patients undergoing cardiac surgery. Methods: Patients undergoing cardiac surgery with pre-existing VT, VF or PVCs were enrolled with informed consent. A standard 12-lead ECG of the VA was recorded in the clinic or during non-invasive programmed stimulation in the EP lab. ECG mapping localized the VA and visualized on a 3D model. During circulatory arrest, surgical ablation was performed using either cryoablation or irrigated RF ablation probe. Follow-up was performed with event monitors or ICD monitoring. Results: A total of 7 patients (mean age 55±15 years, female 29%, EF 31%±20%) were enrolled (Table). Surgical indications included mitral annuloplasty (Pt 1), pulmonary thromboendoarterectomy + CABG (Pt 2), coronary artery unroofing (Pt 3), left ventricular assist device (Pt 4-6, Fig 1), and CABG (Pt 7). In this cohort, 5 PVCs, 3 monomorphic VT and 1 VF morphologies were localized using ECG mapping and surgically ablated at time of cardiac surgery. There was a 100% (18 to 0) decrease in VT/VF episodes and 97.2 ± 0.03% reduction in PVC burden at median 9.5 month (IQR 3.7-29.5) follow-up. No intra- or post-operative complications occurred. Conclusions: This case series illustrates feasibility and excellent efficacy of a novel preoperative ECG mapping workflow using a forward-solution algorithm to guide successful and safe concomitant ventricular arrhythmia ablation during cardiac surgery.

A novel ECG algorithm to differentiate between ventricular arrhythmia from right versus left ventricular outflow tract.

The aim of this study was to evaluate the accuracy of the diagnostic criteria for determining the origin of outflow tract ventricular arrhythmia (OTVA) and develop an ECG algorithm to predict its origin. We analyzed the ECGs of 100 patients with OTVA who underwent successful ablation. The QRS complex was measured during sinus rhythm and ventricular arrhythmia. After the ECG algorithm was developed, it was validated in an additional 100 patients from two different hospitals. In this retrospective study, among the parameters without restrictions in the transition lead, the V2S/V3R index (AUC = 0.96) was significantly better in predicting ventricular arrhythmia originating from the right ventricular outflow tract (RVOT). Further, the larger initial r wave surface area (ISA) in V1 and V2 (AUC = 0.06) was significantly better in predicting ventricular arrhythmias originating from the left ventricular outflow tract (LVOT). Among the parameters with the transition lead in V3, the V2S/V3R index (AUC = 0.82) was significantly better in predicting VAs originating from the RVOT. On the contrary, the V3 R-wave deflection interval (AUC = 0.19) was significantly better in predicting ventricular arrhythmias originating from the LVOT. The algorithm combining the V2S/V3R index and the larger ISA in V1 and V2 could predict OTVA origin with an accuracy of 95.00%, a sensitivity of 87.18%, a specificity of 100.00%, a positive predictive value (PPV) of 100.00%, and a negative predictive value (NPV) of 92.42%. In the validation study, the algorithm exhibited excellent accuracy (95.00%) and AUC (AUC = 0.95), with a sensitivity of 94.12%, a specificity of 95.45%, a PPV of 91.43%, and an NPV of 96.92%. Our developed algorithm can reliably predict OTVA origin without restrictions in the transition lead.

Adenosine monophosphate-regulated protein kinase inhibition modulates electrophysiological characteristics and calcium homeostasis of rabbit right ventricular outflow tract.

Metabolic stress predisposes to ventricular arrhythmias and sudden cardiac death. Right ventricular outflow tract (RVOT) is the common origin of ventricular arrhythmias. Adenosine monophosphate-regulated protein kinase (AMPK) activation is an important compensatory mechanism for cardiac remodeling during metabolic stress. The purpose of this study was to access whether AMPK inhibition would modulate RVOT electrophysiology, calcium (Ca2+ ) regulation, and RVOT arrhythmogenesis or not. Conventional microelectrodes were used to record electrical activity before and after compound C (10 µM, an AMPK inhibitor) in isoproterenol (1 µM)-treated rabbit RVOT tissue preparations under electrical pacing. Whole-cell patch-clamp and confocal microscopic examinations were performed in baseline and compound C-treated rabbit RVOT cardiomyocytes to investigate ionic currents and intracellular Ca2+ transients in isolated rabbit RVOT cardiomyocytes. Compound C decreased RVOT contractility, and reversed isoproterenol increased RVOT contractility. Compound C decreased the incidence, rate, and duration of isoproterenol-induced RVOT burst firing under rapid pacing. Compared to baseline, compound C-treated RVOT cardiomyocytes had a longer action potential duration, smaller intracellular Ca2+ transients, late sodium (Na+ ), peak L-type Ca2+ current density, Na+ -Ca2+ exchanger, transient outward potassium (K+ ) current, and rapid and slow delayed rectifier K+ currents. AMPK inhibition modulates RVOT electrophysiological characteristics and Ca2+ homeostasis, contributing to lower RVOT arrhythmogenic activity. Accordingly, AMPK inhibition might potentially reduce ventricular tachyarrhythmias.

Validation of a clinical model for predicting left versus right ventricular outflow tract origin of idiopathic ventricular arrhythmias.

Prediction of the chamber of origin in patients with outflow tract ventricular arrhythmias (OTVA) remains challenging. A clinical risk score based on age, sex and presence of hypertension was associated with a left ventricular outflow tract (LVOT) origin. We aimed to validate this clinical score to predict an LVOT origin in patients with OTVA. In a two-center observational cohort study, unselected patients undergoing catheter ablation (CA) for OTVA were enrolled. All procedures were performed using an electroanatomical mapping system. Successful ablation was defined as a ≥80% reduction of the initial overall PVC burden after 3 months of follow-up. Patients with unsuccessful ablation were excluded from this analysis. We included 187 consecutive patients with successful CA of idiopathic OTVA. Mean age was 52±15 years, 102 patients (55%) were female, and 74 (40%) suffered from hypertension. A LVOT origin was found in 64 patients (34%). A score incorporating age, sex and presence of hypertension reached 73% sensitivity and 67% specificity for a low (0-1) and high (2-3) score, to predict an LVOT origin. The combination of one ECG algorithm (V2 S/V3 R-index) with the clinical score resulted in a sensitivity and specificity of 81% and 70% for PVCs with R/S transition at V3 . The published clinical score yielded a lower sensitivity and specificity in our cohort. However, for PVCs with R/S transition at V3, the combination with an existing ECG algorithm can improve the predictability of LVOT origin.

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis.

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Improving localization accuracy for non-invasive automated early left ventricular origin localization approach.

Background: We previously developed a non-invasive approach to localize the site of early left ventricular activation origin in real time using 12-lead ECG, and to project the predicted site onto a generic LV endocardial surface using the smallest angle between two vectors algorithm (SA). Objectives: To improve the localization accuracy of the non-invasive approach by utilizing the K-nearest neighbors algorithm (KNN) to reduce projection errors. Methods: Two datasets were used. Dataset #1 had 1012 LV endocardial pacing sites with known coordinates on the generic LV surface and corresponding ECGs, while dataset #2 included 25 clinically-identified VT exit sites and corresponding ECGs. The non-invasive approach used "population" regression coefficients to predict the target coordinates of a pacing site or VT exit site from the initial 120-m QRS integrals of the pacing site/VT ECG. The predicted site coordinates were then projected onto the generic LV surface using either the KNN or SA projection algorithm. Results: The non-invasive approach using the KNN had a significantly lower mean localization error than the SA in both dataset #1 (9.4 vs. 12.5mm, p < 0.05) and dataset #2 (7.2 vs. 9.5mm, p < 0.05). The bootstrap method with 1,000 trials confirmed that using KNN had significantly higher predictive accuracy than using the SA in the bootstrap assessment with the left-out sample (p < 0.05). Conclusion: The KNN significantly reduces the projection error and improves the localization accuracy of the non-invasive approach, which shows promise as a tool to identify the site of origin of ventricular arrhythmia in non-invasive clinical modalities.

Implications of the anatomy of papillary muscle connections for mapping and ablation of focal ventricular arrhythmias

Ventricular arrhythmias (VAs) originating from papillary muscles (PAPs) can be challenging when targeted with catheter ablation. Reasons may include premature ventricular complex pleomorphism, structurally abnormal PAPs, or unusual origins of VAs from PAP-myocardial connections (PAP-MYCs). The purpose of this study was to correlate PAP anatomy with mapping and ablation of PAP VAs. In a series of 43 consecutive patients with frequent PAP arrhythmias referred for ablation, the anatomy and structure of PAPs and VA origins were analyzed using multimodality imaging. Successful ablation sites were analyzed for location on the PAP body or a PAP-MYC. In a total of 17 of 43 patients (40%), VAs originated from a PAP-MYC (in 5 of 17 patients, the PAP inserted into the mitral valve anulus); and in 41 patients, VAs originated from a PAP body. VAs from a PAP-MYC more often had delayed R-wave transition than did other PAP VAs (69% vs 28%; P < .001). Patients with failed procedures had more PAP-MYCs (24.8 ± 8 PAP-MYCs per patient vs 16 ± 7 PAP-MYCs per patient; P < .001). Multimodality imaging identifies anatomic details of PAPs that facilitate mapping and ablation of VAs. In more than a third of patients with PAP VAs, VAs originate from connections between PAPs and the surrounding myocardium or between other PAPs. VA electrocardiographic morphologies are different when VAs originate from PAP-connection sites as compared with VAs originating from the PAP body.

Is it possible to determine arrhythmogenic focus localization of ventricular ectopic complexes detected by ambulatory electrocardiogram monitoring?

Aim. To study the possibility of using algorithms (developed using resting ECG as a mapping tool) for localization arrhythmogenic focus of ventricular arrhythmias (VA) detected by ambulatory 12-lead ECG monitoring (AECGM) with the identification of predominant origins of VA.Material and methods. The study included 54 patients aged 45 to 80 years with high frequency VA evaluated during AECGM: 29 — with coronary artery disease (CAD), 25 — w ithout CAD, who underwent radiofrequency ablation (RFA). The study included patients with effective ablation based on AECGM performed 6 months after RFA. Verification localization of VA exit site was carried out during endocardial mapping and AECGM («Cardiotechnika-04, СT-07», «Incart»). The following algorithms were considered in the study: D. Kuchar; O. Segal; J. Miller; A. S. Revishvili, R. Y. Snegur (2006, 2007); A. B. Weinstein; M. V. Noskova. It was assessed the percentage of matches applying the comparative analysis of results of the invasive and non-invasive methods, and it was revealed the predominant localization of VA.Results. The following algorithms had the highest percentage of matches: D. Kuchar in patients with CAD; A. S. Revishvili, R. Y. Snegur (2007) and M. V. Noskova in patients without CAD. The predominant origins of VA in patients without CAD were the left sinus of Valsalva, right ventricular outflow tract, and in patients with CAD — b asal inferior left ventricular wall, right ventricular outflow tract.Conclusion. Algorithms for arrhythmogenic focus localization of VA, developed using resting ECG, can be used to determine the origin of VA detecting by 12-lead AECGM, taking into account patient’s medical history (CAD, myocardial infarction).

Non-invasive electrocardiographic mapping using an endo-epicardial system based on extracellular potentials shows better accuracy for atrial arrhythmias than ventricular arrhythmias

Abstract Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Learning Health Background and aim Electrocardiographic imaging (ECGI) is capable of performing an activation map with a single beat. The endo-epicardial system based on extracellular potentials allows for the reconstruction of endo-epicardial potentials both in the ventricles and the atria. The aim of this study was to compare the accuracy of the system to predict the site of origin (SOO) of ventricular focal arrhythmias (VAs) versus atrial focal arrhythmias (AAs). Methods We studied 55 consecutive patients referred for ablation of VAs or AAs that had an ECGI performed before ablation. Ablations were performed with remote magnetic navigation or manually. The localization of the VAs and AAs based on the ECGI and invasive electroanatomic mapping was performed using a segmental model of the atria and the ventricles. A perfect match (PM) was defined as a predicted location within the same anatomic segment, whereas a near match (NM) as a predicted location within the same segment or a contiguous one. The number of leads used for ECGI mapping, the agreement between the ECGI and the invasive map, and the success of the procedure were evaluated. Results Ablation was performed in 49 patients. We mapped 54 arrhythmias, 37 VAs (37 patients) and 17 AAs (12 patients). The results according to the atrial or ventricular origin of the arrhythmia are depicted in the table. Patients with AAs were older, no other differences were significant. The ECGI system correctly identified the SOO of both VAs and AAs in the same segment or a contiguous one in 100% of AAs and 97% of VAs, p=1.000. However, the percentage of a PM (Figure) was higher for AAs than for VAs (100% vs 76%, p=0.044). Conclusions The endo-epicardial ECGI correctly identified the origin of both ventricular and atrial arrhythmias. However, the accuracy was higher for the latter.