Reentry Circuit Research Articles

Reconstruction of right ventricular outflow tract stenosis and right ventricular failure after Ross procedure \u2013 comprehensive assessment of adult congenital heart disease with four-dimensional imaging: a case report

BackgroundRe-intervention after Ross procedure into the right ventricular outflow tract might be needed in patients in the long term. However, right ventricular outflow tract re-intervention indications are still unclear. Comprehensive assessment of total hemodynamics is needed.Case summaryA 42-year-old Japanese woman was referred to our hospital for moderately severe pulmonary regurgitation and severe tricuspid regurgitation after a Ross–Konno procedure. Thirteen years after surgery, she developed atrial fibrillation and atrial flutter and complained of dyspnea. Electrophysiological studies showed re-entry circuit around the low voltage area of the lateral wall on the right atrium. Four-dimensional flow magnetic resonance imaging revealed moderate pulmonary regurgitation, severe tricuspid regurgitation, and a dilated right ventricle. Flow energy loss in right ventricle calculated from four-dimensional flow magnetic resonance imaging was five times higher than in normal controls, suggesting an overload of the right-sided heart system. Her left ventricular ejection fraction was almost preserved. Moreover, the total left interventricular pressure difference, which shows diastolic function, revealed that her sucking force in left ventricle was preserved. After the comprehensive assessments, we performed right ventricular outflow tract reconstruction, tricuspid valve annuloplasty, and right-side Maze procedure. A permanent pacemaker with a single atrial lead was implanted 14 days postoperatively. She was discharged 27 days postoperatively. Echocardiography performed 3 months later showed that the size of the dilated right ventricle had significantly reduced.DiscussionA four-dimensional imaging tool can be useful in the decision of re-operation in patients with complex adult congenital heart disease. The optimal timing of surgery should be considered comprehensively.

Successful epicardial ablation for ventricular tachycardia originating from the true apex of apical aneurysm associated with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) with apical aneurysm (AA) is rare, but has been reported to be associated with refractory ventricular tachycardias (VTs). Majority of such cases had a central isthmus of the reentry circuit on the border zone of AA. In this report, we describe a rare case of the successful epicardial ablation for a refractory VT originating from a true apex of the aneurysm in a HCM patient. Mid-diastolic potential during sustained VT was recorded at the isolated epicardial myocardium surround by the gross unexcitable scar in AA, and radiofrequency current application rendered VT non-inducible.

P957Characteristics of atrial tachycardia after mitral surgey via biatrial trans-septal approach using high density mapping system

Abstract Background The biatrial trans-septal approach (BTSa) ameliorates mitral valve (MV) exposure in difficult cases when routine left atriotomy doesnt"t allow it. Main steps are an oblique incision on the right atrium (RA), reaching medially the right pulmonary veins (PV), a septal incision from the fossa ovalis, extended up to reach the first incision, then on the left atrium (LA). Purpose We aim to study the arrhythmic burden in this post-surgical context, focusing on atrial tachycardia (AT), to investigate the complexity of several possible circuits. Methods All patients (>18yo) with previous MV surgery via BTSa for MV repair or replacement, who underwent ablation of AT from January 2017 to September 2019, were enrolled. Patients ablated for persistent or paroxysmal AF, or with AF during the index procedure were excluded. Patients with associated surgery on other valves or congenital defects, coronary, surgical or percutaneous rhythm interventions weren’t excluded. Electroanatomical mapping was created using 2 different high-density mapping system. Substrate and activation map and radio-frequency (RF) ablation (25-50W, Ablation Index target 400) were realized. Cartographies were analysed to evaluate AT re-entry circuit, critical isthmus (CI) location and characterization, atrial vulnerability. Procedural outcomes (AT termination, sinus rhythm (SR) restoration, anti-arrhythmic drugs (AAD) withdrawal), and peri-procedural complications were also evaluated. Results We enrolled 49 patients (median age 57 ± 15), finding a maximum of 5 AT per procedure (2 ± 1). A total of 112 AT were mapped: the majority (72%) were persistent AT, 8,2% common atrial flutter. Cycle length was 314 ± 74 msec, with proximal-distal activation of coronary sinus (78%). A multiple re-entry circuit was observed in 70% of index AT. We identified 152 critical isthmus (maximum 5 per procedure). Only 27,9% of our patients had a single CI; CTI was the most frequent one (n = 37), envolved in 33% of all AT, while BTS scars altogether were envolved in 65% AT. A complete AT circuit was mapped in the RA, the LA and both atria in respectively 49%, 11,5% and 39%AT. The distribution of CIs is shown in figure 1. Biatrial and left AT leads to superior procedure, RF and fluoroscopy duration (p <0,05). SR was restored in 93,4%of patients, requiring a DC shock in 4 cases. Immediate AAD withdrawal was achieved after 41%procedures. No pericardial, oesophageal, vascular or phrenic complication occurred. 4 pace-maker implantations were realized because of 3 interatrial, 2 AV block and a sinus node dysfunction. Conclusions AT occurring after a BTSa have a high prevalence of multiple re-entry circuits with multiple critical isthmus. Ablation in this context is feasible and safe but often requires a left atrial access. Mapping of both atria should be considered to identify critical isthmus and tailored ablation strategy. Abstract Figure 1. Critical Isthmus Distribution

129Magnetic resonance predictors of ventricular tachycardia recurrence after radiofrequency substrate ablation: septal and transmural channels

Abstract Ventricular tachycardia (VT) substrate-based ablation has become a gold standard in patients with structural heart disease. Success of VT ablation is related with mortality reduction. Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) is a powerful technique to assess substrate of VT. Myocardial fibrosis is electrically inert (Core) but it is surrounded by a ‘‘border-zone (BZ)’’ where normal cardiomyocytes intermingle with dense bundles of fibrosis. Slow impulse conduction in the BZ allows for the re-entry circuits leading to VT. Both the presence and extent of LGE have been associated with VT and SCD risk. LGE-CMR tissue characterization can be depicted as pixel signal intensity (PSI) maps and can guide VT ablation. The aim of this study was to analyze possible VT recurrence predictors in a long term follow-up of patients that underwent VT ablation (endo and/or epicardial) related with LGE-CMR PSI maps. We analyzed 234 consecutive patients (age: 63.2 ± 14 years, follow-up: 3.14 years ±1.8) undergoing VT ablation with scar-dechannelling technique at a single center from 2013 to 2018. 110 patients underwent a preprocedural LGE-CMR, and in 94 patients (85,5%) a CMR-aided ablation using the PSI maps was performed. All LGE-CMR images were semi-automatically processed using a dedicated software. PSI-based algorithm was applied to characterize the hyperenhanced area as core or BZ, using fixed threshold of the maximum intensity. A LV 3D shell was obtained and were imported into the navigation system. In the PSI maps, heterogenous tissue channels were defined as a continuous corridor of BZ surrounded by scar core or an anatomic barrier that connects 2 areas of healthy tissue. Results Overall recurrence of VT was 41.8 %. There was ICD shock reduction, from 43,6% to a 28,2% (ICD shocks before ablation 2,23 ± 7,32, after: 1,10 ± 2,92). Left ventricle mass predicted significantly VT recurrence (Mean 168,3 ± 53,3 vs 152,3 ± 46,4 g, HR 1,02 [1,01-1,02], p < 0.001). LGE distribuition was predictive of VT recurrence when a more than 40% of the interventricular septum was involved (62,5% vs 37,8%; HR 1,6 [1,01-1,02]; p = 0,044). No differences in recurrence were found among the patterns of LGE distribution (transmural/epicardial/subendocardial or peculiar segments localizations). The amount of BZ and the total amont of Core + BZ was related with VT recurrence (BZ 26,6 ± 13,9 vs 19,56 ± 9,69 g, HR 1,03 [1,01-1,06], p = 0,012; total Core + BZ 37,1 ± 18,2 vs 29,0 ± 16,3 g, HR 1,02 [1,00-1,04], p = 0,033). Finally VT recurrence was higher in patients with channels with transmural path (66,7% vs 31,4%, HR 3,25 [1,70-6,23], p < 0,001) or midmural channels (54,3% vs 27,6%, HR 2,49 [1,21–5,13], p = 0,013). CMR-aided scar dechanneling is a helpful and feasible technique which could identify patients with high risk of VT recurrence. High left ventricular mass, septal LGE distribution, transmural and midmural heterogeneous tissue channels were predictive factors of post ablation VT recurrence. Abstract Figure. VTchannel & heterogeoneus tissue channel

P1377Substrate-based ablation in patients with frequent appropriate ICD therapy and dilated cardiomyopathy: long-term experience with high-density mapping

Abstract Recurrent ventricular tachydisrhythmias (VT) episodes have a negative impact in the outcome of patients (P) already with an implantable cardioverter-defibrillator (ICD). Elimination of arrhythmic reentry circuits represents a difficult challenge, mainly due to the induction of intolerable VTs, with multiple ECG morphologies, requiring rapid interruption. Substrate guided ablation has been used as a promising approach strategy to treat recurrent VTs. Aim: to assess long-term results of a VT substrate-based ablation using high-density mapping in P with an ICD, severe left ventricular (LV) dysfunction and recurrent appropriate ICD therapy. Methods: 16P (12 men, non-ischemic cardiomyopathy 67%, 55 ± 13 years, LV ejection fraction 32 ± 6%) and recurrent appropriate shocks despite antiarrhythmic drug therapy and optimal heart failure medication. All P underwent a protocol of ventricular programmed stimulation (600 ms/S3) to obtain baseline VT documentation. A sinus rhythm (SR) voltage map was created using a 3D electroanatomic mapping system (CARTO) with a high-density mapping catheter (PentaRay) to delineate areas of scarred myocardium (ventricular bipolar voltage ≤0,5 mV – dense scar; 0,5-1,5 mV – border zone; ≥1,5 mV – healthy tissue) and provide high-resolution electrophysiological mapping. The substrate modification included catheter elimination of local abnormal ventricular activities (LAVA) - fractionated, splited, low-amplitude/long-lasting, late potentials, pre-systolic potentials - and linear ablation to obtain scars homogenization and scar dechanneling. Pace-mapping techniques were used when capture was possible. LV approach was retrograde in 6 cases, transeptal in 4 and endo-epicardial in 2 cases. In 2P the ablation was performed in the right ventricle. Results: VTs were induced and interrupted with bursts or external DC shocks. LAVA were identified and ablated in all P. Eleven P underwent modification of scar areas. The mean duration of the procedure was 153 mn (103-218 mn), with radiofrequency ranging from 18 to 60 mn (mean 33 min), and a mean fluoroscopy time of 16 mn. Non-inducibility was achieved in 75% of the cases. There was 1 pericardial tamponade drained successfully. During a follow-up of 48 ± 18 months, 75% had no VT recurrences, 2P underwent redo ablation, 1P died from stroke. Conclusion: Catheter ablation of VT based on substrate modification guided by high-density mapping is feasible and safe in P with LV dysfunction. This approach may be of clinical relevance, with potential benefits in reducing VT burden.

Characterization of Complex Atrial Tachycardia in Patients With Previous Atrial Interventions Using High-Resolution Mapping.

This study systematically evaluated mechanisms of atrial tachycardia (AT) by using ultra-high-resolution mapping in a large cohort of patients. An incomplete understanding of the mechanism of AT is a major determinant of ablation failure. Consecutive patients with≥1 AT (excluding cavotricuspid isthmus-dependent flutter) were included. Mapping was performed with a 64-pole mapping catheter. The AT mechanism was defined based on activation mapping and confirmed by entrainment in selected cases. A total of 132 patients were included (60 ± 12 years; 31 [23%] female; 111 [84%] previous atrial fibrillation [AF] ablation; 5 [4%] previous left atriotomy). One hundred four (94%) of the 111 post-AF ablation AT patients had substrate-based ablation during the index AF ablation. A total of 214 ATs were mapped, with complete definition of the AT mechanism in 206 (96%). A total of 129 (60%) had anatomic macro-re-entry (circuit diameter 44.2 ± 9.6mm), 57 (27%) had scar-related localized re-entry (circuit diameter 25.8 ± 12.2mm), and 20 (9%) had focal AT. Fifty-eight (45%) patients had multiple ATs (27 [20%] dual-loop re-entry; 60 [43%] sequential AT) with complex and highly variable transitions between AT circuits. A total of 116 (90%) of 129 macro-re-entrant ATs, 56 (98%) of 57 localized AT, and 20 (100%) of 20 focal ATs terminated after radiofrequency ablation. After a mean follow-up of 13 ± 9months, 57 (46%) patients experienced recurrence of AT. Among patients with AT in the context of previous atrial interventions, particularly post-AF ablation patients, multiple complex AT circuits are common. Despite complete delineation of arrhythmia circuits using ultra-high-resolution mapping and high acute ablation success rates, long-term freedom from AT is modest.

The Da Silva cone operation after the Starnes procedure for Ebstein's anomaly: New surgical strategy and initial results.

The Da Silva cone operation after the Starnes procedure for Ebstein's anomaly: New surgical strategy and initial results.

Unique electrophysiological properties of fast-slow atrioventricular nodal reentrant tachycardia characterized by a shortening of retrograde conduction time via a slow pathway manifested during atrial induction.

Electrophysiological properties of reentry circuits of fast-slow atrioventricular nodal reentrant tachycardia (F/S-AVNRT) may contribute to cyclic variability after atrial induction. In 156 atrial inductions of 33 patients with F/S-AVNRT, we measured the atrio-His (AH) and His-atrial (HA) intervals in the first cycle after the induction (AH[1] and HA[1], respectively), those in the second cycle (AH [2] and HA [2], respectively), and those during tachycardia that maintained a stable cycle length AH[T] and HA[T], respectively), and calculated the value of AH(1) minus AH(T) [ΔAH] and the value of HA(1) minus HA(T) [ΔHA] in each induction. According to the sum of ΔAH and ΔHA, tachycardia variability was classified as incremental (<-20), balanced (-20 to 20), or decremental (>20). ΔAH and ΔHA were significantly different between the three responses: 6 ± 28 and -67 ± 39 in 55 inductions (35%) with an incremental response, 20 ± 10 and -23 ± 28 in 59 (38%) with a balanced response, and 54 ± 44 and 4 ± 50 in 42 (27%) with a decremental response, respectively. Incremental response was reproducibly and consistently observed in 33% of patients. HA(2) was similar to HA(T) in inductions with an incremental response. These results suggest that incremental response can be manifested only in the first cycle when HA(1) is excessively shortened, approximating a retrograde conduction time over a slow pathway, in contrast, and far superior to a decremental delay of AH(1). In specific patients with F/S-AVNRT, poorly recognized, electrophysiological properties of shortening a retrograde conduction time over a slow pathway was manifested during atrial induction.

2019 APHRS expert consensus statement on three-dimensional mapping systems for tachycardia developed in collaboration with HRS, EHRA, and LAHRS.

2019 APHRS expert consensus statement on three-dimensional mapping systems for tachycardia developed in collaboration with HRS, EHRA, and LAHRS.

Demonstration of the Anatomical Tachycardia Circuit in Sinoatrial Node Reentrant Tachycardia: Analysis Using the Entrainment Method.

BackgroundThe anatomical tachycardia circuit of sinoatrial node reentrant tachycardia (SANRT) has not been well clarified. This study aimed to elucidate the tachycardia circuit of SANRT.Methods and ResultsExit and entrance of the intranodal sinoatrial node conduction (I‐SANC) of the reentry circuit were identified in 15 SANRT patients. After identifying the earliest atrial activation site (EAAS) during the tachycardia (EAAS‐SANRT), rapid atrial pacing was delivered from multiple atrial sites to identify the entrainment pacing site where manifest entrainment and orthodromic capture of the EAAS‐SANRT were demonstrated. Radiofrequency energy was then delivered starting at a site 2 cm proximal to the EAAS‐SANRT in the direction of the entrainment pacing site and gradually advanced toward the EAAS‐SANRT until tachycardia termination to localize the I‐SANC entrance. The EAAS‐SANRT was orthodromically captured by pacing delivered from the distal coronary sinus (n=7), high posteroseptal right atrium (n=2), low posteroseptal right atrium (n=2), low anterolateral right atrium (n=2), or coronary sinus ostium (n=2). Radiofrequency energy delivery to the entrance of the I‐SANC, 10.4±2.8 mm away from the EAAS‐SANRT, terminated tachycardia immediately after onset of energy delivery (3.4±2.3 seconds). The successful ablation site was located further from the EAAS during sinus rhythm (EAAS‐sinus) than the EAAS‐SANRT (12.8±4.5 versus 7.2±3.1 mm; P<0.0001).ConclusionsThe reentry circuit of SANRT was composed of the entrance and exit of the I‐SANC being located at distinctly different anatomical sites. SANRT was eliminated by radiofrequency energy delivered to the I‐SANC entrance, which was further from the EAAS‐sinus than I‐SANC exit.

Successful case of complex atrial flutter occurring in a patient with congenitally corrected transposition of the great arteries, aberrant left atrial appendage, and situs inversus

BackgroundCongenitally corrected transposition of great arteries (ccTGA) is a rare congenital cardiac defect with atrioventricular and ventriculoarterial discordance which leads to heart failure and limits patients’ lifespan. The extremely aberrant cardiac structure makes electrophysiological procedure and radiofrequency ablation very difficult to be performed in such patients. Until now, there were only sporadical cases that have reported the successful ablation of atrial flutter in ccTGA patients.Case presentationWe report a case of a 36-year-old male who was diagnosed with dextrocardia, atrial septal defect and congenitally corrected transposition of great arteries (ccTGA) at a young age and received atrial septal defect repair and morphological tricuspid valve plasty in 2014. As for reasons of heart failure and atrial flutter, he frequently suffered from progressively worsening dyspnea and recurrent episodes of palpitations. Cardiac anatomic imaging reconstruction before electrophysiological test revealed an unusually huge left atrial appendage in this patient. After high-density mapping of both right atrium and left atrium, activation mapping showed reentry circuit loops were located in left atrium. Successful ablation strategy was performed under the guidance of high-density mapping and entrainment.ConclusionThis is a clinical case showing high-density mapping and successful ablation of a complex dual-loop atrial flutter in a patient with ccTGA and aberrant left atrial appendage. The successful procedure corroborates clinical utility of high-density mapping approach in the treatment of the patients with complex congenital heart disease accompanied by rapid arrhythmia, can be simpler, safer and more effective.

Missing pouches in high-density mapping of atrial tachyarrhythmia in congenital heart diseases.

BackgroundThe use of high‐density electroanatomical mapping in the Chinese population for congenital heart disease (CHD) is not well reported.MethodsRetrospective review of consecutive transcatheter ablation of atrial tachyarrhythmia using high‐density mapping for CHD patients (at least moderate complexity) in the only tertiary congenital heart center in the territory from January 2017 to January 2019 was conducted. Orion mapping catheter in Rhythmia system (Boston Scientific) was used to create activation and voltage maps. Parameters including mechanism of arrhythmia, acute success, and follow‐up data were recorded.ResultsEight patients were identified (median age 35.5 years) who underwent transcatheter ablation of atrial arrhythmia. More than one reentry circuits of IART were identified in five patients. It took a median of 32.4 minutes with 15,952 (IQR 13,395‐18,530) mapping points per map. Cavo‐annulus isthmus‐dependent mechanism was the predominant reentry mechanism. Acute success with the elimination of all inducible tachycardia was achieved in six patients (75%), and partial success in two patients. There was recurrence of atrial arrhythmia in four patients (50%), in which three patients could be maintained in sinus rhythm with low‐dose antiarrhythmic medication. Targeted substrate ablation was performed in six patients with multiple IART circuits. Critical anatomical pouches were identified in three patients, which were missed in the initial mapping using Orion basket mapping catheter.ConclusionsHigh acute success rate of atrial arrhythmia ablation can be achieved using high‐density anatomical mapping in CHD. Substrate ablation was required with multiple IART circuits identified. Vigilance should be sought to identify anatomical pouches.

A Clinical Review of Ventricular Arrhythmias in Patients with Congestive Heart Failure

Heart failure is an increasingly prevalent condition, which is associated with ventricular arrhythmias. The reduction in cardiac pumping efficiency leads to the activation of several compensatory mechanisms. These mechanisms eventually lead to cardiac remodelling and a decline in haemodynamic status, contributing to the formation of a substrate conducive to arrhythmias, including increased automaticity, triggered activity, and, most commonly, re-entry circuits. In turn, ventricular arrhythmias can lead to the worsening of heart failure. A diagnosis of heart failure and ventricular arrhythmias is obtained using the patient’s history, examination findings, and investigation results. A key tool in this is echocardiogram imaging, which visualises the cardiac chambers, determines ventricular ejection fraction, and identifies structural abnormalities. A reduction in ejection fraction is a significant risk factor for the development of ventricular arrhythmias. Arrhythmias are diagnosed by ECG, Holter monitoring, and telemetry or event monitoring, and should initially be treated by optimising the medical management of heart failure. Anti-arrhythmic drugs, including beta-blockers, are usually the first-line therapy. Sudden cardiac death is a significant cause of mortality in heart failure patients, and implantable cardioverter defibrillator devices are used in both primary and secondary prevention. Anti-arrhythmic drugs and catheter ablation are important adjunctives for minimising shock therapy. In addition, autonomic modulation may offer a novel method of controlling ventricular arrhythmias. The objective of this review is to provide a practical overview of this rapidly developing field in relation to current evidence regarding the underlying pathophysiology, burden of disease, and management strategies available.

A Clinical Review of Ventricular Arrhythmias in Patients with Congestive Heart Failure

Heart failure is an increasingly prevalent condition, which is associated with ventricular arrhythmias. The reduction in cardiac pumping efficiency leads to the activation of several compensatory mechanisms. These mechanisms eventually lead to cardiac remodelling and a decline in haemodynamic status, contributing to the formation of a substrate conducive to arrhythmias, including increased automaticity, triggered activity, and, most commonly, re-entry circuits. In turn, ventricular arrhythmias can lead to the worsening of heart failure. A diagnosis of heart failure and ventricular arrhythmias is obtained using the patient’s history, examination findings, and investigation results. A key tool in this is echocardiogram imaging, which visualises the cardiac chambers, determines ventricular ejection fraction, and identifies structural abnormalities. A reduction in ejection fraction is a significant risk factor for the development of ventricular arrhythmias. Arrhythmias are diagnosed by ECG, Holter monitoring, and telemetry or event monitoring, and should initially be treated by optimising the medical management of heart failure. Anti-arrhythmic drugs, including beta-blockers, are usually the first-line therapy. Sudden cardiac death is a significant cause of mortality in heart failure patients, and implantable cardioverter defibrillator devices are used in both primary and secondary prevention. Anti-arrhythmic drugs and catheter ablation are important adjunctives for minimising shock therapy. In addition, autonomic modulation may offer a novel method of controlling ventricular arrhythmias. The objective of this review is to provide a practical overview of this rapidly developing field in relation to current evidence regarding the underlying pathophysiology, burden of disease, and management strategies available.

Stereotactic radiosurgery for ablation of ventricular tachycardia.

Stereotactic body radiotherapy (SBRT) for ventricular tachycardias (VTs) could be an option after failed catheter ablation. In this study, we analysed the long-term efficacy and toxicity of SBRT applied as a bail-out procedure. Patients with structural heart disease and unsuccessful catheter ablations for VTs underwent SBRT. The planning target volume (PTV) was accurately delineated using exported 3D electroanatomical maps with the delineated critical part of re-entry circuits. This was defined by detailed electroanatomic mapping and by pacing manoeuvres during the procedure. Using the implantable cardioverter-defibrillator lead as a surrogate contrast marker for respiratory movement compensation, 25 Gy was delivered to the PTV using CyberKnife. We evaluated occurrences of sustained VT, electrical storm, antitachycardia pacing, and shock; time to death; and radiation-induced events. From 2014 until March 2017, 10 patients underwent radiosurgical ablation (mean PTV, 22.15 mL; treatment duration, 68 min). After radiosurgery, four patients experienced nausea and one patient presented gradual progression of mitral regurgitation. During the follow-up (median 28 months), VT burden was reduced by 87.5% compared with baseline (P = 0.012) and three patients suffered non-arrhythmic deaths. After the blanking period, VT recurred in eight of 10 patients. The mean time to first antitachycardia pacing and shock were 6.5 and 21 months, respectively. Stereotactic body radiotherapy appears to show long-term safety and effectiveness for VT ablation in structural heart disease inaccessible to catheter ablation. We report one possible radiation-related toxicity and promising overall survival, warranting evaluation in a prospective multicentre clinical trial.

The role of Marshall bundle epicardial connections in atrial tachycardias after atrial fibrillation ablation

Atrial tachycardias (ATs) are often seen in the context of atrial fibrillation (AF) ablation. To evaluate the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density 3-dimensional mapping. A total of 199 ATs were mapped in 140 patients (112 male, mean age: 61.8 years); 133 (66.8%) were macroreentrant and 66 (33.2%) were scar-related reentry circuits. MB-dependent ATs were suggested by activation mapping analysis and confirmed with entrainment along the circuit. The MB network participated in 60 (30.2%) reentrant ATs: 31 perimitral ATs (PMATs) and 29 localized reentry circuits. Of 60 MB-related ATs, 49 (81.6%) terminated with radiofrequency (RF) ablation: 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-coronary sinus (CS) junction, while 9 (15%) terminated after 2.5-5 cc of ethanol infusion inside the vein of Marshall (VOM). Of the 31 PMATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction, and 7 (22.6%) with ethanol infusion. Of the 29 localized reentry circuits using the MB, 27 (93.1%) terminated at the MB-LA junction, none at the MB-CS junction, and 2 (6.9%) after ethanol infusion. Recurrences were mostly observed after RF ablation (18 of 37 patients, 49%) compared to ethanol infusion (1 of 9 patients, 11%) (P = .06). MB reentrant ATs accounted for up to 30.2% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or ethanol infusion inside the VOM is required to treat these arrhythmias.

Mechanisms of torsade de pointes tachycardia in patients with spontaneous high-degree atrioventricular block: A modern look at old data

IntroductionThe mechanisms of torsade de pointes tachycardia (TdP) are incompletely understood. We aimed to investigate the mechanisms underlying TdP tachycardia in patients with spontaneous high-degree atrioventricular block (AVB). Methods and resultsThis retrospective study reviewed old TdP recordings after ventricular temporary pacing interruption in 16 patients with spontaneous high-degree AVB. Five of them had also bipolar endocardial right ventricular (RV) apex recordings. The QT interval during AVB at a mean heart rate of 38.9 ± 7.5 bpm was 653.0 ± 67.2 ms. The critical coupling interval (CCI) between the last escape QRS during AVB and the first premature ventricular complex (PVC) was significantly shorter before the onset of TdP than before single PVCs and couplets. A morphologic crescendo of the escape T wave was observed before the onset of TdP, followed by a rhythmic and morphologic crescendo of PVCs. The escape RV apex electrograms (EGMs) showed the constant pattern of a rapid deflection similar to a Purkinje potential 40 to 80 ms after the onset of the QRS, superimposed on a smooth low amplitude signal in 4 out of 5 patients. ConclusionsThe major endocardial T wave prolongation and augmentation (morphologic crescendo) of the escape beat prior to the first PVC suggests a phase 2 reentry mechanism due to early afterdepolarization. The induced TdP can be due to the changing outputs from one or two simultaneous RV moving reentry circuits between depressed fibers and fast conducting ones, possibly located in the thin crista supraventricularis structure which has several connections with the septum and the RV free wall.

Bundle branch reentrant tachycardia treated with cardiac resynchronization therapy in a patient with dilated cardiomyopathy

A 66 years old woman with known dilated cardiomyopathy and severely reduced ejection fraction presented with bundle branch reentrant tachycardia. Bundle branch reentrant tachycardia is an uncommon form of ventricular tachycardia incorporating both bundle branches into the reentry circuit. The diagnosis is based on electrophysiological findings and pacing maneuvres that prove participation of the His- Purkinje system in the tachycardia mechanism. Radiofrequency ablation of right bundle is proposed as the first line therapy. In our patient, the ablation imposed a high risk of complications in view of the existing conduction defects. We decided to proceed with a CRT – D implantation, which improved patient’s symptoms and diminished ventricular tachycardia episodes. As a result, biventricular pacing may serve as an alternative method to ablation treatment.

Postinfarction Myocardial Calcifications on Cardiac Computed Tomography: Implications for Mapping and Ablation in Patients With Nontolerated Ventricular Tachycardias.

Postinfarction ventricular tachycardia (VT) generally involves myocardial fibers surrounded by scar. Calcification of scar tissue has been described, but the relationship between calcifications within endocardial scar and VTs is unclear. The purpose of this study was to assess the prevalence of myocardial calcifications as detected by cardiac computed tomography (CT) and the benefit for mapping and ablation focusing on nontolerated VTs. Fifty-six consecutive postinfarction patients had a cardiac CT performed before a VT ablation procedure. Another 56 consecutive patients with prior infarction without VT who had cardiac CTs served as a control group. Myocardial calcifications were identified in 39 of 56 patients (70%) in the postinfarction group with VT, compared with 6 of 56 patients (11%) in the control group without VT. Calcifications were associated with VT when compared with a control group. A calcification volume of 0.538 cm3 distinguished patients with calcification-associated VT from patients without calcification-associated VTs (area under the curve, 0.87; sensitivity, 0.87; specificity, 0.88). Myocardial calcifications corresponded to areas of electrical nonexcitability and formed a border for reentry circuits for 49 VTs (33% of all VTs for which target sites were identified) in 24 of 39 patients (62%) with myocardial calcifications. A nonconfluent calcification pattern was associated with VT target sites independent of calcification volume ( P=0.01). Myocardial calcifications detected by cardiac CT in patients with prior infarction are associated with VT. The calcifications correspond to areas of unexcitability and represent a fixed boundary of reentry circuits that can be visualized by CT. Calcifications correspond to effective ablation sites in >1/3 of patients with postinfarction VT.

Evaluation using a four-dimensional imaging tool before and after pulmonary valve replacement in a patient with tetralogy of Fallot: a\xa0case report

BackgroundPulmonary regurgitation is a common complication after tetralogy of Fallot repair, resulting in right ventricular dysfunction, arrhythmia, and sudden death. However, the indications and optimal timing for pulmonary valve replacement are not fully known. We describe a case in which a four-dimensional imaging tool was useful in the decision to re-operate, thus resulting in decreased energy loss and improved right ventricular function after the re-operation for tetralogy of Fallot.Case presentationA 54-year-old Japanese woman visited our hospital due to palpitations and wide QRS tachycardia with persistent tiredness for several months. She underwent repair of tetralogy of Fallot when she was 2-years old. An electrocardiogram showed prolonged QRS duration (199 msec) with a complete right bundle branch block and an echocardiograph demonstrated that her right ventricle was highly enlarged and had poor contraction, and severe pulmonary valve regurgitation with one leaflet flail. Four-dimensional flow magnetic resonance imaging demonstrated that regurgitant volumes and regurgitant fractions of pulmonary regurgitation were calculated as 63.12 ml and 54.0%, respectively. Right ventricular end-diastolic/end-systolic volume index was 169.54/99.76 mL/m2, and the cardiac index was 1.78 L/minute per m2. Flow energy loss was 2.93 mW, which is estimated to be three times higher than normal controls. An electrophysiological study showed an intact anterior internodal pathway and a slow pathway just through the outside of the right atriotomy line scar, which is supposed to cause a re-entry circuit. We decided to perform a pulmonary valve replacement and a right maze procedure. A 27 mm bioprosthetic valve was implanted in the native pulmonary annulus with a supra-annular position. Concomitantly, the right maze procedure was performed. A four-dimensional flow magnetic resonance imaging done 3 months later showed that right ventricular end-diastolic/end-systolic volume index had significantly reduced to 85.24/55.41 mL/m2 and the cardiac index had increased from 1.78 to 2.58 L/minute per m2. Energy loss had greatly improved from 2.93 to 1.48 mW.ConclusionsA four-dimensional imaging tool was useful in the decision to re-operate, thus resulting in decreased energy loss and improved right ventricular function after the re-operation for tetralogy of Fallot.