Electrophysiological study prior to planned pulmonary valve replacement in patients with repaired tetralogy of Fallot.

AIM: Ventricular arrhythmias (VAs) are the most common cause of death in patients with repaired Tetralogy of Fallot (rTOF). However, risk stratifying remains challenging. We examined outcomes following programmed ventricular stimulation (PVS) with or without subsequent ablation in patients with rTOF planned for pulmonary valve replacement (PVR). METHODS: We included all consecutive patients with rTOF referred to our institution from 2010 to 2018 aged ≥18 years for PVR. Right ventricular (RV) voltage maps were acquired and PVS was performed from two different sites at baseline, and if non-inducible under isoproterenol. Catheter and/or surgical ablation was performed when patients were inducible or when slow conduction was present in anatomical isthmuses (AIs). Postablation PVS was undertaken to guide implantable cardioverter-defibrillator (ICD) implantation. RESULTS: Seventy-seven patients (36.2 ± 14.3 years old, 71% male) were included. Eighteen were inducible. In 28 patients (17 inducible, 11 non-inducible but with slow conduction) ablation was performed. Five had catheter ablation, surgical cryoablation in 9, both techniques in 14. ICDs were implanted in five patients. During a follow-up of 74 ± 40 months, no sudden cardiac death occurred. Three patients experienced sustained VAs, all were inducible during the initial EP study. Two of them had an ICD (low ejection fraction for one and important risk factor for arrhythmia for the second). No VAs were reported in the non-inducible group (p < .001). CONCLUSION: Preoperative EPS can help identifying patients with rTOF at risk for VAs, providing an opportunity for targeted ablation and may improve decision-making regarding ICD implantation.

Prevalence and risk factors of cardiac thrombus prior to ventricular tachycardia catheter ablation in structural heart disease.

AIMS: Assess prevalence, risk factors, and management of patients with intra-cardiac thrombus referred for scar-related ventricular tachycardia (VT) ablation. METHODS AND RESULTS: Consecutive VT ablation referrals between January 2015 and December 2019 were reviewed (n = 618). Patients referred for de novo, scar-related VT ablation who underwent pre-procedure cardiac computed tomography (cCT) were included. We included 401 patients [61 ± 14 years; 364 male; left ventricular ejection fraction (LVEF) 40 ± 13%]; 45 patients (11%) had cardiac thrombi on cCT at 49 sites [29 LV; eight left atrial appendage (LAA); eight right ventricle (RV); four right atrial appendage]. Nine patients had pulmonary emboli. Overall predictors of cardiac thrombus included LV aneurysm [odds ratio (OR): 6.6, 95%, confidence interval (CI): 3.1-14.3], LVEF < 40% (OR: 3.3, CI: 1.5-7.3), altered RV ejection fraction (OR: 2.3, CI: 1.1-4.6), and electrical storm (OR: 2.9, CI: 1.4-6.1). Thrombus location-specific analysis identified LV aneurysm (OR: 10.9, CI: 4.3-27.7) and LVEF < 40% (OR: 9.6, CI: 2.6-35.8) as predictors of LV thrombus and arrhythmogenic right ventricular cardiomyopathy (OR: 10.6, CI: 1.2-98.4) as a predictor for RV thrombus. Left atrial appendage thrombi exclusively occurred in patients with atrial fibrillation. Ventricular tachycardia ablation was finally performed in 363 including 7 (16%) patients with thrombus but refractory electrical storm. These seven patients had tailored ablation with no embolic complications. Only one (0.3%) ablation-related embolic event occurred in the entire cohort. CONCLUSION: Cardiac thrombus can be identified in 11% of patients referred for scar-related VT ablation. These findings underscore the importance of systematic thrombus screening to minimize embolic risk.

Advanced Imaging Integration for Catheter Ablation of Ventricular Tachycardia.

PURPOSE OF REVIEW: Imaging plays a crucial role in the therapy of ventricular tachycardia (VT). We offer an overview of the different methods and provide information on their use in a clinical setting. RECENT FINDINGS: The use of imaging in VT has progressed recently. Intracardiac echography facilitates catheter navigation and the targeting of moving intracardiac structures. Integration of pre-procedural CT or MRI allows for targeting the VT substrate, with major expected impact on VT ablation efficacy and efficiency. Advances in computational modeling may further enhance the performance of imaging, giving access to pre-operative simulation of VT. These advances in non-invasive diagnosis are increasingly being coupled with non-invasive approaches for therapy delivery. This review highlights the latest research on the use of imaging in VT procedures. Image-based strategies are progressively shifting from using images as an adjunct tool to electrophysiological techniques, to an integration of imaging as a central element of the treatment strategy.

Distribution of atrial low voltage induced by vein of Marshall ethanol infusion.

INTRODUCTION: Systematic and quantitative descriptions of vein of Marshall (VOM)-induced tissue ablation are lacking. We sought to characterize the distribution of low voltage observed in the left atrium (LA) after VOM ethanol infusion. METHODS AND RESULTS: The distribution of ethanol-induced low voltage was evaluated by comparing high-density maps performed before and after VOM ethanol infusion in 114 patients referred for atrial fibrillation ablation. The two most frequently impacted segments were the inferior portion of the ridge (82.5%) and the first half of the mitral isthmus (pulmonary vein side) (92.1%). Low-voltage absence in these typical areas resulted from inadvertent ethanol infusion in the left atrial appendage vein (n = 3), initial VOM dissection (n = 3), or a "no branches" VOM morphology (n = 1). Visible anastomosis of the VOM with roof or posterior veins more frequently resulted in low-voltage extension beyond typical areas, toward the entire left antrum (19.0% vs. 1.9%, p = .0045) or the posterior LA (39.7% vs. 3.8%, p < .001) but with a limited positive predictive value ranging from 29.4% to 43.5%. Ethanol-induced low voltage covered a median LA surface of 3.6% (1.9%-5.0%) and did not exceed 8% of the LA surface in 90% of patients. CONCLUSION: VOM ethanol infusion typically locates at the inferior ridge and the adjacent half of the mitral isthmus. Low-voltage extensions can be anticipated but not guaranteed by the presence of visible anastomosis of the VOM with roof or posterior veins.

Strategy for repeat procedures in patients with persistent atrial fibrillation: Systematic linear ablation with adjunctive ethanol infusion into the vein of Marshall versus electrophysiology-guided ablation.

INTRODUCTION: The optimal strategy after a failed ablation for persistent atrial fibrillation (perAF) is unknown. This study evaluated the value of an anatomically guided strategy using a systematic set of linear lesions with adjunctive ethanol infusion into the vein of Marshall (Et-VOM) in patients referred for second perAF ablation procedures. METHODS AND RESULTS: Patients with perAF who underwent a second procedure were grouped according to the two strategies. The first strategy was an anatomically guided approach using systematic linear ablation with adjunctive Et-VOM, with bidirectional blocks at the posterior mitral isthmus (MI), roof, and cavotricuspid isthmus (CTI) as the procedural endpoint (Group I). The second one was an electrophysiology-guided strategy, with atrial tachyarrhythmia termination as the procedural endpoint (Group II). Arrhythmia behavior during the procedure guided the ablation strategy. Groups I and II consisted of 96 patients (65 ± 9 years; 71 men) and 102 patients (63 ± 10 years; 83 men), respectively. Baseline characteristics were comparable. In Group I, Et-VOM was successfully performed in 91/96 (95%), and procedural endpoint (bidirectional block across all three anatomical lines) was achieved in 89/96 (93%). In Group II, procedural endpoint (atrial tachyarrhythmia termination) was achieved in 80/102 (78%). One-year follow-up demonstrated Group I (21/96 [22%]) experienced less recurrence compared to Group II (38/102 [37%], Log-rank p = .01). This was driven by lower AT recurrence in Group I (Group I: 10/96 [10%] vs. Group II: 29/102 [28%]; p = .002). CONCLUSION: Anatomically guided strategy with adjunctive Et-VOM is superior to an electrophysiology-guided strategy for second procedures in patients with perAF at 1-year follow-up.

Preoperative personalization of atrial fibrillation ablation strategy to prevent esophageal injury: Impact of changes in esophageal position.

INTRODUCTION: Due to changes in esophageal position, preoperative assessment of the esophageal location may not mitigate the risk of esophageal injury in catheter ablation for atrial fibrillation (AF). This study aimed to assess esophageal motion and its impact on AF ablation strategies. METHODS AND RESULTS: Ninety-seven AF patients underwent two computed tomography (CT) scans. The area at risk of esophageal injury (AAR) was defined as the left atrial surface ≤3 mm from the esophagus. On CT1, ablation lines were drawn blinded to the esophageal location to create three ablation sets: individual pulmonary vein isolation (PVI), wide antral circumferential ablation (WACA), and WACA with linear ablation (WACA + L). Thereafter, ablation lines for WACA and WACA + L were personalized to avoid the AAR. Rigid registration was performed to align CT1 onto CT2, and the relationship between ablation lines and the AAR on CT2 was analyzed. The esophagus moved by 3.6 [2.7 to 5.5] mm. The AAR on CT2 was 8.6 ± 3.3 cm2 , with 77% overlapping that on CT1. High body mass index was associated with the AAR mismatch (standardized ß 0.382, p < .001). Without personalization, AARs on ablation lines for individual PVI, WACA, and WACA + L were 0 [0-0.4], 0.8 [0.5-1.2], and 1.7 [1.2-2.0] cm2 . Despite the esophageal position change, the personalization of ablation lines for WACA and WACA + L reduced the AAR on lines to 0 [0-0.5] and 0.7 [0.3-1.0] cm2 (p < .001 for both). CONCLUSION: The personalization of ablation lines based on a preoperative CT reduced ablation to the AAR despite changes in esophageal position.

Pause-dependent mitral isthmus conduction block during ablation of the mitral isthmus: What is the mechanism?

Mitral isthmus (MI) ablation is commonly performed as an adjunct therapy to pulmonary isolation during the treatment for persistent atrial fibrillation. Confirmation of complete MI block is essential because an incomplete MI block may result in iatrogenic atrial tachycardia. However, there are several pitfalls in the diagnosis of an MI line block. We herein report a case of transient pause-dependent MI block during MI ablation.

Characteristics of macroreentrant atrial tachycardias using an anatomical bypass: Pseudo-focal atrial tachycardia case series.

INTRODUCTION: Human atria comprise distinct layers. One layer can bypass another, and lead to a downstream centrifugal propagation at their interface. We sought to characterize anatomical substrates, electrophysiological properties, and ablation outcomes of "pseudo-focal" atrial tachycardias (ATs), defined as macroreentrant ATs mimicking focal ATs. METHODS AND RESULTS: We retrospectively analyzed left atrial ATs showing centrifugal propagation with postpacing intervals (PPIs) after entrainment pacing suggestive of a macroreentrant mechanism. A total of 22 patients had pseudo-focal ATs consisting of 15 perimitral and 7 roof-dependent flutters. A low-voltage area was consistently found at the collision site and colocalized with distinct anatomical structures like the: (1) coronary sinus-great cardiac vein bundle (27%), (2) vein of Marshall bundle (18%), (3) Bachmann bundle (27%), (4) septopulmonary bundle (18%), and (5) fossa ovalis (9%). The mean missing tachycardia cycle length (TCL) was 65 ± 31 ms (22%) on the endocardial activation map. PPI was 0 [0-15] ms and 0 [0-21] ms longer than TCL at the breakthrough site and the opposite site, respectively. While feasible in 21 pseudo-focal ATs (95%), termination was better achieved by blocking the anatomical isthmus than ablating the breakthrough site [20/21 (95%) vs. 1/5 (20%); p < .001]. CONCLUSION: Perimitral and roof-dependent flutters with centrifugal propagation are favored by a low-voltage area located at well-identified anatomical structures. Comprehensive entrainment pacing maneuvers are crucial to distinguish pseudo-focal ATs from true focal ATs. Blocking the anatomical isthmus is a better therapeutic option than ablating the breakthrough site.

Accuracy of automatic abnormal potential annotation for substrate identification in scar-related ventricular tachycardia.

INTRODUCTION: Ultrahigh-density mapping for ventricular tachycardia (VT) is increasingly used. However, manual annotation of local abnormal ventricular activities (LAVAs) is challenging in this setting. Therefore, we assessed the accuracy of the automatic annotation of LAVAs with the Lumipoint algorithm of the Rhythmia system (Boston Scientific). METHODS AND RESULTS: One hundred consecutive patients undergoing catheter ablation of scar-related VT were studied. Areas with LAVAs and ablation sites were manually annotated during the procedure and compared with automatically annotated areas using the Lumipoint features for detecting late potentials (LP), fragmented potentials (FP), and double potentials (DP). The accuracy of each automatic annotation feature was assessed by re-evaluating local potentials within automatically annotated areas. Automatically annotated areas matched with manually annotated areas in 64 cases (64%), identified an area with LAVAs missed during manual annotation in 15 cases (15%), and did not highlight areas identified with manual annotation in 18 cases (18%). Automatic FP annotation accurately detected LAVAs regardless of the cardiac rhythm or scar location; automatic LP annotation accurately detected LAVAs in sinus rhythm, but was affected by the scar location during ventricular pacing; automatic DP annotation was not affected by the mapping rhythm, but its accuracy was suboptimal when the scar was located on the right ventricle or epicardium. CONCLUSION: The Lumipoint algorithm was as/more accurate than manual annotation in 79% of patients. FP annotation detected LAVAs most accurately regardless of mapping rhythm and scar location. The accuracy of LP and DP annotations varied depending on mapping rhythm or scar location.

High-risk atrioventricular block in Brugada syndrome patients with a history of syncope.

BACKGROUND: Determining the etiology of syncope is challenging in Brugada syndrome (BrS) patients. Implantable cardioverter defibrillator placement is recommended in BrS patients who are presumed to have arrhythmic syncope. However, arrhythmic syncope in BrS patients can occur in the setting of atrioventricular block (AVB), which should be managed by cardiac pacing. The clinical characteristics of BrS patients with high-risk AVB remain unknown. METHODS: This study included 223 BrS patients with a history of syncope from two centers. The clinical characteristics of patients with high-risk AVB (Mobitz type II second-degree AVB, high-degree AVB, or third-degree AVB) were investigated. RESULTS: During the 99 ± 78 months of follow-up, we identified six BrS patients (2.7%) with high-risk AVB. Three of the six patients (50%) with AVB presented with syncope associated with prodromes or specific triggers. Four patients (67%) were found to have paroxysmal third-degree AVB during the initial evaluation for BrS and syncope, while two patients developed third-degree AVB during the follow-up period. The incidence of first-degree AVB was significantly higher in AVB patients than in non-AVB patients (83% vs. 15%; p = .0005). There was no significant difference in the incidence of ventricular fibrillation between AVB and non-AVB patients (AVB [17%], non-AVB [12%]; p = .56). CONCLUSION: High-risk AVB can occur in BrS patients with various clinical presentations. Although rare, the incidence is worth considering, especially in BrS patients with first-degree AVB.

Pulsed field ablation selectively spares the oesophagus during pulmonary vein isolation for atrial fibrillation.

AIMS: Extra-atrial injury can cause complications after catheter ablation for atrial fibrillation (AF). Pulsed field ablation (PFA) has generated preclinical data suggesting that it selectively targets the myocardium. We sought to characterize extra-atrial injuries after pulmonary vein isolation (PVI) between PFA and thermal ablation methods. METHODS AND RESULTS: Cardiac magnetic resonance (CMR) imaging was performed before, acutely (<3 h) and 3 months post-ablation in 41 paroxysmal AF patients undergoing PVI with PFA (N = 18, Farapulse) or thermal methods (N = 23, 16 radiofrequency, 7 cryoballoon). Oesophageal and aortic injuries were assessed by using late gadolinium-enhanced (LGE) imaging. Phrenic nerve injuries were assessed from diaphragmatic motion on intra-procedural fluoroscopy. Baseline CMR showed no abnormality on the oesophagus or aorta. During ablation procedures, no patient showed phrenic palsy. Acutely, thermal methods induced high rates of oesophageal lesions (43%), all observed in patients showing direct contact between the oesophagus and the ablation sites. In contrast, oesophageal lesions were observed in no patient ablated with PFA (0%, P < 0.001 vs. thermal methods), despite similar rates of direct contact between the oesophagus and the ablation sites (P = 0.41). Acute lesions were detected on CMR on the descending aorta in 10/23 (43%) after thermal ablation, and in 6/18 (33%) after PFA (P = 0.52). CMR at 3 months showed a complete resolution of oesophageal and aortic LGE in all patients. No patient showed clinical complications. CONCLUSION: PFA does not induce any signs of oesophageal injury on CMR after PVI. Due to its tissue selectivity, PFA may improve safety for catheter ablation of AF.

Pulsed field ablation prevents chronic atrial fibrotic changes and restrictive mechanics after catheter ablation for atrial fibrillation.

AIMS: Pulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation. METHODS AND RESULTS: Cardiac magnetic resonance was performed pre-ablation, acutely (<3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P < 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA. CONCLUSION: Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions.

Ligament of Marshall ablation for persistent atrial fibrillation.

Beyond pulmonary vein isolation, the two main additional strategies: Cox-Maze procedure or targeting of electrical signatures (focal bursts, rotational activities, meandering wavelets), remain controversial. High-density mapping of these arrhythmias has demonstrated firstly that a patchy lesion set is highly proarrhythmogenic, favoring macro-re-entry through conduction slowing and providing pivots for localized re-entry. Secondly, discrete anatomical structures such as the Vein or Ligament of Marshall (VOM/LOM) and the coronary sinus (CS) have epicardial muscular bundles that are more frequently involved in re-entry than previously thought. The Marshall Bundle can be ablated at any point along its course from the mid-to-distal coronary sinus to the left atrial appendage. If necessary, the VOM may be directly ablated using ethanol infusion to eliminate PV contributions and produce conduction block across the mistral isthmus. Ethanol ablation of the VOM, supplemented with RF ablation, may be more effective in producing conduction block at the mitral isthmus than repeat RF ablation alone.

Local abnormal ventricular activity detection in scar-related VT: Microelectrode versus conventional bipolar electrode.

BACKGROUND: Conventional bipolar electrodes (CBE) may be suboptimal to detect local abnormal ventricular activities (LAVAs). Microelectrodes (ME) may improve the detection of LAVAs. This study sought to elucidate the detectability of LAVAs using ME compared with CBE in patients with scar-related ventricular tachycardia (VT). METHODS: We included consecutive patients with structural heart disease who underwent radiofrequency catheter ablation for scar-related VT using either of the following catheters equipped with ME: QDOTTM or IntellaTip MIFITM. Detection field of LAVA potentials were classified as three types: Type 1 (both CBE and ME detected LAVA), Type 2 (CBE did not detect LAVA while ME did), and Type 3 (CBE detected LAVA while ME did not). RESULTS: In 16 patients (68 ± 16 years; 14 males), 260 LAVAs electrograms (QDOT = 72; MIFI = 188) were analyzed. Type 1, type 2, and type 3 detections were 70.8% (QDOT, 69.4%; MIFI, 71.3%), 20.0% (QDOT, 23.6%; MIFI, 18.6%) and 9.2% (QDOT, 6.9%; MIFI, 10.1%), respectively. The LAVAs amplitudes detected by ME were higher than those detected by CBE in both catheters (QDOT: ME 0.79 ± 0.50 mV vs. CBE 0.41 ± 0.42 mV, p = .001; MIFI: ME 0.73 ± 0.64 mV vs. CBE 0.38 ± 0.36 mV, p < .001). CONCLUSIONS: ME allow to identify 20% of LAVAs missed by CBE. ME showed higher amplitude LAVAs than CBE. However, 9.2% of LAVAs can still be missed by ME.

Narrowing QRS by ventricular over drive pacing during a wide-QRS complex tachycardia; What is the mechanism?

We describe a case where ventricular overdrive pacing during a wide QRS complex supraventricular tachycardia demonstrated constant fusion by narrowing the QRS complex duration and diagnosing the tachycardia mechanism.

Evaluation of the QT interval in patients with drug-induced QT prolongation and torsades de pointes.

BACKGROUND: Data on the optimal location of the electrocardiogram (ECG) leads for the diagnosis of drug-induced long QT syndrome (diLQTS) with torsades de pointes (TdP) are lacking. METHODS: We systematically reviewed the literature for the ECGs of patients with diLQTS and subsequent TdP. We assessed T wave morphology in each lead and measured the longest QT interval in the limb and chest leads in a standardized fashion. RESULTS: Of 84 patients, 61.9% were female and the mean age was 58.8 years. QTc was significantly longer in chest versus limb leads (mean (SD) 671 (102) vs. 655 (97) ms, p = .02). Using only limb leads for QT interpretation, 18 (21.4%) ECGs were noninterpretable: 10 (11.9%) due to too flat T waves, 7 (8.3%) due to frequent, early PVCs and 1 (1.2%) due to too low ECG recording quality. In the chest leads, ECGs were noninterpretable in nine (10.7%) patients: six (7.1%) due to frequent, early PVCs, one (1.2%) due to insufficient ECG quality, two (2.4%) due to missing chest leads but none due to too flat T waves. The most common T wave morphologies in the limb leads were flat (51.0%), broad (14.3%), and late peaking (12.6%) T waves. Corresponding chest lead morphologies were inverted (35.5%), flat (19.6%), and biphasic (15.2%) T waves. CONCLUSIONS: Our results indicate that QT evaluation by limb leads only underestimates the incidence of diLQTS experiencing TdP and favors the screening using both limb and chest lead ECG.

Electrogram morphology discriminators in implantable cardioverter defibrillators: A comparative evaluation.

BACKGROUND: Morphology algorithms are currently recommended as a standalone discriminator in single-chamber implantable cardioverter defibrillators (ICDs). However, these proprietary algorithms differ in both design and nominal programming. OBJECTIVE: To compare three different algorithms with nominal versus advanced programming in their ability to discriminate between ventricular (VT) and supraventricular tachycardia (SVT). METHODS: In nine European centers, VT and SVTs were collected from Abbott, Boston Scientific, and Medtronic dual- and triple-chamber ICDs via their respective remote monitoring portals. Percentage morphology matches were recorded for selected episodes which were classified as VT or SVT by means of atrioventricular comparison. The sensitivity and related specificity of each manufacturer discriminator was determined at various values of template match percentage from receiving operating characteristics (ROC) curve analysis. RESULTS: A total of 534 episodes were retained for the analysis. In ROC analyses, Abbott Far Field MD (area under the curve [AUC]: 0.91; P < .001) and Boston Scientific RhythmID (AUC: 0.95; P < .001) show higher AUC than Medtronic Wavelet (AUC: 0.81; P < .001) when tested for their ability to discriminate VT from SVT. At nominal % match threshold all devices provided high sensitivity in VT identification, (91%, 100%, and 90%, respectively, for Abbott, Boston Scientific, and Medtronic) but contrasted specificities in SVT discrimination (85%, 41%, and 62%, respectively). Abbott and Medtronic's nominal thresholds were similar to the optimal thresholds. Optimization of the % match threshold improved the Boston Scientific specificity to 79% without compromising the sensitivity. CONCLUSION: Proprietary morphology discriminators show important differences in their ability to discriminate SVT. How much this impact the overall discrimination process remains to be investigated.

Causes of impaired biventricular pacing in cardiac resynchronization devices with left ventricular sensing.

BACKGROUND: Loss of biventricular stimulation can result in nonresponse to cardiac resynchronization therapy (CRT). Problems associated with the left ventricular (LV) lead and LV sensing can be challenging to detect and their incidence is unclear. The purpose of this study was to investigate mechanisms of loss of biventricular pacing due to LV lead- and LV sensing-associated problems. METHODS: In this bicentric study, CRT patients were surveilled using a novel remote monitoring algorithm from Biotronik (Germany) that registers LV electrograms (EGMs) during intermittent loss of resynchronization. The episodes were analyzed to assess the mechanisms of resynchronization interruptions. RESULTS: We analyzed 582 EGMs from 61 patients. During a median follow-up of 6 months, 59% of the patients had such episodes. The majority of the episodes (61%) were related to inappropriate inhibition of LV pacing, mostly due to upper rate lock-in caused by LV sensing (58%). In contrast, 8% of episodes showed intermittent loss of LV capture, which was identified thanks to LV sensing. The remaining 31% of episodes were due to physiological reasons for resynchronization interruptions (eg, supraventricular tachycardia [18%], premature beats [8%], and others [5%]). Patients with CRT interruption episodes had lower resynchronization rates (median: 98.5% vs 100%, P = .044). CONCLUSIONS: Inadequate programming (active LV sensing with T-wave protection) is the main cause of impaired resynchronization in devices with LV sensing. In general, we recommend the deactivation of the LV T-wave protection function.

Left ventricular sensing in cardiac resynchronization devices-opportunities and pitfalls for device programming.

INTRODUCTION: Some cardiac resynchronization therapy (CRT) device manufacturers (Biotronik, Germany; Boston Scientific, United States) have implemented left ventricular (LV) sensing functionality to prevent pacing into the vulnerable phase. Physicians are only partially aware of programming pitfalls related to LV sensing and general programming advice is lacking. METHODS AND RESULTS: We provide an illustrative case-series-based review of the variety of potential problems with LV sensing. LV sensing may inappropriately impair CRT delivery due to LV-sensing issues or improper device programming. This can cause beat-wise loss of resynchronization but also ongoing desynchronization. On the other hand, LV sensing provides additional diagnostic information, which may reveal intermittent problems of the LV lead such as capture loss. We summarize the available evidence to provide manufacturer-specific recommendations on device programming and troubleshooting for daily clinical practice. CONCLUSION: CRT devices with LV sensing may suffer from impaired resynchronization due to programming pitfalls. If LV sensing is active (nominal setting in Biotronik and Boston Scientific devices), careful lookout for related problems and resynchronization percentage is required. Optimization is mandatory and even deactivation of LV sensing may have to be considered.

Local VA index for the differential diagnosis of supraventricular tachycardia.

BACKGROUND: Differentiating between atypical atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia utilizing a septal accessory pathway is a complex challenge. OBJECTIVE: The purpose of this study was to describe the "local VA index," a straightforward method based on signals from the coronary sinus catheter, to distinguish between these arrhythmias during tachycardia and entrainment. The ventriculoatrial (VA) interval on the coronary sinus catheter is measured during tachycardia and entrainment, at the site of earliest atrial activity. The difference between these 2 situations defines the "local VA index." We also propose a mechanism to clarify the limitations of historical pacing maneuvers, such as postpacing interval minus tachycardia cycle length (PPI-TCL) and stimulus-atrial interval minus ventriculoatrial interval (SA-VA), by examining nodal decrement and intraventricular conduction delay. METHODS: In a retrospective study of 75 patients referred for supraventricular tachycardia evaluation, 37 were diagnosed with atrioventricular reentrant tachycardia (AVRT) with orthodromic reciprocating tachycardia, and 38 with AVNRT (27 typical, 11 atypical). RESULTS: In comparison to AVRT patients, AVNRT patients exhibited longer PPI-TCL (176 ± 47 ms vs 113 ± 42 ms; P <.01) and SA-VA (138 ± 47 ms vs 64 ± 28 ms; P <.01). The AVRT group had mean local VA index of -1 ± 13 ms, whereas the AVNRT group had a significantly longer index of 91 ± 46 ms (P <.01). An optimal threshold for differentiation was a local VA index of 40 ms. Importantly, there was no significant correlation between pacing cycle length and nodal decrement as well as intraventricular delay related to pathway location. This interindividual variability might explain misleading interpretations of PPI-TCL and SA-VA. CONCLUSION: This novel approach is advantageous because of its simplicity and effectiveness, requiring only 2 diagnostic catheters. A local VA interval difference <40 ms provides a clear distinction for AVRT.