Vein of Marshall chemical ablation decreases atrial fibrillation drivers detected by CARTOFINDER.

INTRODUCTION: This study sought to elucidate the impact of vein of Marshall (VOM) chemical ablation on atrial fibrillation (AF) drivers by investigating the changes in CARTOFINDER mappings before and after VOM chemical ablation in patients with persistent AF. METHODS: This study included 23 consecutive patients undergoing catheter ablation for long-persistent AF (>18 months). VOM chemical ablation was performed following pulmonary vein isolation. CARTOFINDER and AF cycle length (AFCL) maps were created in the left atrium (LA) before and after VOM chemical ablation. The LA was divided into 8 segments, and the number of focal activation points with 6 or more repetitions was counted in each segment. RESULTS: The number of focal activation points was largest in the LA appendage (LAA). After VOM chemical ablation, the number of focal activation points in the LA decreased significantly (37 [interquartile range, IQR: 19-55] vs. 15 [IQR: 7-21], p < .001), and median AFCL was significantly prolonged (159 [147-168] vs. 164 [150-173] ms, p < .001). In the assessment of each segment, significant decreases in focal activation points were observed in the inferior, lateral, and anterior segments and LAA. Among the focal activation points disappearing after chemical ablation, the number in the non-ethanol-affected area was significantly larger than that in the affected area (13 [8-25] vs. 4 [1-10], p < .001). CONCLUSIONS: VOM chemical ablation decreases AF drivers detected by CARTOFINDER. Mechanisms other than direct myocardial damage are considered to contribute the attenuation of AF drivers.

Delivery catheter system carries more physiological right ventricular septal pacing than stylet system.

INTRODUCTION: The Mt. FUJI multicenter trial demonstrated that a delivery catheter system had a higher rate of successful right ventricular (RV) lead deployment on the RV septum (RVS) than a conventional stylet system. In this subanalysis of the Mt. FUJI trial, we assessed the differences in electrocardiogram (ECG) parameters during RV pacing between a delivery catheter system and a stylet system and their associations with the lead tip positions. METHODS: Among 70 patients enrolled in the Mt FUJI trial, ECG parameters, RV lead tip positions, and lead depth inside the septum assessed by computed tomography were compared between the catheter group (n = 36) and stylet group (n = 34). RESULTS: The paced QRS duration (QRS-d), corrected paced QT (QTc), and JT interval (JTc) were significantly shorter in the catheter group than in the stylet group (QRS-d: 130 ± 19 vs. 142 ± 15 ms, p = .004; QTc: 476 ± 25 vs. 514 ± 20 ms, p < .001; JTc: 347 ± 24 vs. 372 ± 17 ms, p < .001). This superiority of the catheter group was maintained in a subgroup analysis of patients with an RV lead tip position at the septum. The lead depth inside the septum was greater in the catheter group than in the stylet group, and there was a significant negative correlation between the paced QRS-d and the lead depth. CONCLUSION: Using a delivery catheter system carries more physiological depolarization and repolarization during RVS pacing and deeper screw penetration in the septum in comparison to conventional stylet system. The lead depth could have a more impact on the ECG parameters rather than the type of pacing lead.

Unidirectional conduction characterizing epicardial connections in patients with atrial tachyarrhythmias.

INTRODUCTION: Electrophysiological characteristics of epicardial connections (ECs) in atria and pulmonary veins (PVs) are unclear despite their important contributions to atrial fibrillation (AF). Unidirectional conduction associated with source-sink mismatch can occur in ECs due to their fine fibers with abrupt changes in orientation. We detailed the prevalence and electrophysiological characteristics of unidirectional conduction in the atria and investigated its association with the clinical manifestation of AF. METHODS: This study retrospectively reviewed electrophysiological studies and radiofrequency catheter ablation in 261 consecutive patients with AF. RESULTS: Unidirectional conduction was observed during ablation encircling the PVs in eight (3.1%) patients, and all occurred in the suspected (N = 4) or definitively (N = 4) recognized ECs. These ECs included three intercaval bundles, four septopulmonary bundles, and one Marshall bundle, and were first manifested in a second procedure in 6 (75%) patients. The unidirectional property was from PV to atrium (exit conduction) in all intercaval bundles and three septopulmonary bundles, and from atrium to PV (entrance conduction) in the remaining two bundles. Intercaval bundles acted as a limb of bi-atrial macro-reentrant tachycardia (50%, three of the six including previous cases). Ablation of the exit outside the PVs, including the right atrium, eliminated ECs in three (38%) patients. All patients remain free from arrhythmia recurrence after a mean 13-month follow-up. CONCLUSION: A unidirectional conduction property was closely associated with the EC, as estimated by histological findings. Recognition of this fact by electrophysiologists may help to clarify mechanisms for AF and atrial tachycardia and guide the creation of efficient and safe ablation lesion sets.

Usefulness of delivery catheter on accurate right ventricular septal pacing: Mt FUJI trial.

AIMS: Although the delivery catheter system for pacemaker-lead implantation is a new alternative to the stylet system, no randomized controlled trial has addressed the difference in right ventricular (RV) lead placement accuracy to the septum between the stylet and the delivery catheter systems. This multicentre prospective randomized controlled trial aimed to prove the efficacy of the delivery catheter system for accurate delivery of RV lead to the septum. METHODS AND RESULTS: In this trial, 70 patients (mean age 78 ± 11 years; 30 men) with pacemaker indications of atrioventricular block were randomized to the delivery catheter or the stylet groups. Right ventricular lead tip positions were assessed using cardiac computed tomography within 4 weeks of pacemaker implantation. Lead tip positions were classified into RV septum, anterior/posterior edge of the RV septal wall, and RV free wall. The primary endpoint was the success rate of RV lead tip placement to the RV septum. RESULTS: Right ventricular leads were implanted as per allocation in all patients. The delivery catheter group had higher success rate of RV lead deployment to the septum (78 vs. 50%; P = 0.024) and narrower paced QRS width (130 ± 19 vs. 142 ± 15 ms P = 0.004) than those in the stylet group. However, there was no significant difference in procedure time [91 (IQR 68-119) vs. 85 (59-118) min; P = 0.488] or the incidence of RV lead dislodgment (0 vs. 3%; P = 0.486). CONCLUSION: The delivery catheter system can achieve a higher success rate of RV lead placement to the RV septum and narrower paced QRS width than the stylet system. TRIAL REGISTRATION NUMBER: jRCTs042200014 (https://jrct.niph.go.jp/en-latest-detail/jRCTs042200014).

Impact of Interatrial Epicardial Connections on the Dominant Frequency of Atrial Fibrillation.

BACKGROUND: An epicardial connection (EC) between the right-sided pulmonary venous (RtPV) carina and right atrium (RA) may preclude PV isolation, but its electrophysiological role during atrial fibrillation (AF) remains unknown.Methods and Results: This prospective observational study included 98 consecutive patients undergoing catheter ablation for AF, subdivided into the EC group (n=17) and non-EC group (n=80) based on observation of RA posterior wall breakthrough during RtPV pacing. Mean left atrial (LA) dominant frequency (mean DFLA) was defined as the averaged DFs at the right and left PVs and LA appendage. The regional DF was higher in the EC group vs. the non-EC group except at the left PV antrum. The DF at the RA appendage (RAA) and mean DFLAwere equivocal (6.5±0.7 vs. 6.6±0.7 Hz) in the EC group, but the mean DFLAwas significantly higher than that at the RAA (5.8±0.6 vs. 6.1±0.5 Hz, P=0.001) in the non-EC group, suggesting an LA-to-RA DF gradient. A significant correlation of DF between the RtPV antrum and RAA was observed in the EC group (P<0.001, r=0.84) but not in the non-EC group. CONCLUSIONS: An electrophysiological link via interatrial ECs might attenuate the hierarchical nature of activation frequencies of AF, leading to advanced electrical remodeling of the atria.

A simple pacing maneuver to unmask an epicardial connection involving the right-sided pulmonary veins.

INTRODUCTION: An epicardial connection (EC) between the right-sided pulmonary venous (PV) carina and right atrium (RA) is one of the mechanisms for which carinal ablation is required for right-sided PV isolation. The purpose of the study was to devise a simple pacing maneuver to differentiate an EC from a residual conduction gap on the antral ablation line during radiofrequency catheter ablation. METHODS AND RESULTS: This study included 133 consecutive patients. After one round of ablation, electrograms at the posterior antrum outside the ablation line were recorded during sinus rhythm (SR) and coronary sinus (CS) pacing, and intervals between the antral and PV potentials were measured in each rhythm. The ΔintervalSR-CS was calculated as the difference between the interval during SR and that during CS pacing. Presence of an EC was confirmed by observation of a RA posterior wall breakthrough during right-sided PV pacing, which was then targeted for ablation. Patients with nonachievement of first-pass isolation (N = 35) and with PV reconnection during the procedure (N = 9) were classified into the EC-group (N = 20) and gap-group (N=24), respectively. The prevalence of carina breakthrough during SR was higher in the EC-group than the gap-group (18 [95%] vs. 1 [4%] patients, p < .0001). The ΔintervalSR-CS was larger in the EC-group versus gap-group (71 [interquartile range, 57-97] vs. 6 [2-9] ms, p < .0001). In all patients with an EC, RA ablation resulted in delay (32 [20-40] ms) (N = 15) or elimination of PV potentials (N = 5). CONCLUSION: An EC can be efficiently discriminated from a conduction gap by a simple pacing maneuver.

Oral caffeine intake amplifies the effect of isoproterenol in patients with frequent premature ventricular contractions.

AIMS: Infrequent appearance and failed induction of premature ventricular contractions (PVCs) at catheter ablation make their localization difficult and are associated with a poor procedural outcome. This study aimed to assess the effect of preprocedural oral caffeine intake on induction of PVCs during catheter ablation. METHODS AND RESULTS: Seventy patients (age: 54 ± 14 years, 37 men) undergoing catheter ablation for monofocal PVCs were randomized to receive oral caffeine (5 mg/kg) or placebo. Before ablation, PVC counts for 5 min were performed at baseline and during isoproterenol infusion and the isoproterenol washout period. PVC count fluctuation was defined as the difference between the highest and lowest 5-min count among the three-time periods. The 5-min PVC counts during baseline and isoproterenol infusion were equivalent between the groups. However, those during the isoproterenol washout period and PVC count fluctuation were significantly higher in the caffeine group than the control group (73.1 ± 73.2 vs. 38.9 ± 28.9 beats/5 min, P = 0.012 and 69.3 ± 61.3 vs. 37.7 ± 30.9 beats/5 min, P = 0.008, respectively). The procedure and ablation times were significantly shorter in the caffeine group than the control group (105.0 ± 23.4 vs. 136.9 ± 43.2 min, P < 0.01 and 219.1 ± 104.7 vs. 283.5 ± 136.0 sec, P < 0.01, respectively). CONCLUSION: Oral caffeine intake amplified the effect of isoproterenol infusion on PVC induction during catheter ablation. The combined use of oral caffeine intake and isoproterenol infusion can be an option to increase intraprocedural PVCs.

Difference in epicardial adipose tissue distribution between paroxysmal atrial fibrillation and coronary artery disease.

BACKGROUND: An increase in epicardial adipose tissue (EAT) volume is associated with the development of atrial fibrillation (AF) and coronary artery disease (CAD), but little is known about differences in its distribution. METHODS AND RESULTS: We included 50 patients with paroxysmal AF (PAF), 50 patients with CAD, and 50 control patients. Using multidetector computed tomography, EAT volumes surrounding the whole heart (total EAT), the atrium (atrial-EAT), and the ventricle (ventricular-EAT) were measured. EAT atrial/ventricular (A/V) ratio was calculated by dividing atrial- by ventricular-EAT volume. The total EAT volume indexes in the PAF and CAD groups were significantly larger than those in the control group. The atrial-EAT volume index in the PAF group was significantly larger than that in the CAD and control groups, whereas the ventricular-EAT volume index in the CAD group was significantly larger than that in the PAF and control groups. Thus, EAT A/V ratio was smaller in the CAD and control group than that in the PAF group (0.28 ± 0.12 vs. 0.38 ± 0.13 vs. 0.54 ± 0.33, P < .001). Univariate and multivariate linear regression analysis showed EAT A/V ratio to be independently associated with cardiovascular disease type (PAF vs. CAD; P < .001, ß = .463). CONCLUSIONS: Atrial- and ventricular-dominant distribution of EAT was observed in the PAF and CAD groups, respectively. Uneven distribution of EAT may imply the direct contribution of EAT-related inflammation to the pathogenesis of AF or CAD.

Predictors of Recurrence after Catheter Ablation of Paroxysmal Atrial Fibrillation in Different Follow-Up Periods.

Background and objectives: Pulmonary vein (PV) reconnection is a major reason for recurrence after catheter ablation of paroxysmal atrial fibrillation (PAF). However, the timing of the recurrence varies between patients, and recurrence >1 year after ablation is not uncommon. We sought to elucidate the characteristics of atrial fibrillation (AF) that recurred in different follow-up periods. Materials and Methods: Study subjects comprised 151 consecutive patients undergoing initial catheter ablation of PAF. Left atrial volume index (LAVi) and atrial/brain natriuretic peptide (ANP/BNP) levels were systematically measured annually over 3 years until AF recurred. Results: Study subjects were classified into four groups: non-recurrence group (n = 84), and short-term- (within 1 year) (n = 30), mid-term- (1-3 years) (n = 26), and long-term-recurrence group (>3 years) (n = 11). The short-term-recurrence group was characterized by a higher prevalence of diabetes mellitus (hazard ratio 2.639 (95% confidence interval, 1.174-5.932), p = 0.019 by the Cox method), frequent AF episodes (≥1/week) before ablation (4.038 (1.545-10.557), p = 0.004), and higher BNP level at baseline (per 10 pg/mL) (1.054 (1.029-1.081), p < 0.0001). The mid-term-recurrence group was associated with higher BNP level (1.163 (1.070-1.265), p = 0.0004), larger LAVi (mL/m2) (1.033 (1.007-1.060), p = 0.013), and longer AF cycle length at baseline (per 10 ms) (1.194 (1.058-1.348), p = 0.004). In the long-term-recurrence group, the ANP and BNP levels were low throughout follow-up, as with those in the non-recurrence group, and AF cycle length was shorter (0.694 (0.522-0.924), p = 0.012) than those in the other recurrence groups. Conclusions: Distinct characteristics of AF were found according to the time to first recurrence after PAF ablation. The presence of secondary factors beyond PV reconnections could be considered as mechanisms for the recurrence of PAF in each follow-up period.

Structural relation between the superior vena cava and pulmonary veins in patients with atrial fibrillation.

The superior vena cava (SVC) is a main source of non-pulmonary vein (PV) ectopies that initiate atrial fibrillation (AF). Although the critical role of structural remodeling of the left atrium (LA) in the occurrence of AF was extensively investigated by atrial voltage mapping, that of PVs and the SVC has been less explored. Study subjects comprised 47 patients undergoing catheter ablation of lone AF. During sinus rhythm, PV, SVC, and atrial voltage maps were acquired, and sleeve length of each PV and SVC was determined by an electroanatomical mapping system. The sleeves of the superior PVs were significantly longer than those of the inferior PVs (left superior PV (LSPV): 21 ± 5, left inferior PV: 14 ± 4, right superior PV (RSPV): 19 ± 5, right inferior PV: 15 ± 5, and SVC: 23 ± 10 mm, p < 0.0001). The LSPV sleeve was longer in men than in women (22 ± 6 vs. 19 ± 4 mm, p < 0.05). The sleeve length in the LSPV correlated positively with the body surface area (BSA) (p = 0.003, R = 0.42). Of note, there was a significant correlation in sleeve length between the RSPV and SVC (p < 0.0001, R = 0.64). In conclusion, not right- but left-sided PV sleeves were associated with the BSA of the patients, whereas a structural relation between the right-sided PVs and the SVC was implied based on sleeve mapping. This novel finding may provide mechanistic implications for the development of AF in future studies.

Differences in the structural characteristics and distribution of epicardial adipose tissue between left and right atrial fibrillation.

Aims: Right atrial (RA) fibrillation (RAF) was previously characterized by initiation from RA ectopies, presence of a right-to-left dominant frequency gradient during atrial fibrillation (AF), and augmentation of the gradient by adenosine triphosphate infusion. We investigated structural characteristics of the bi-atria and epicardial adipose tissue (EAT) volume in patients with RAF. Methods and results: By using multidetector computed tomography, RA, left atrial (LA), right and LA appendage (RAA and LAA, respectively) volumes, pulmonary vein (PV) sizes, and EAT volumes were compared between the RAF group (n = 8) and LA fibrillation (LAF) group (n = 32). Compared with the LAF group, the LA volume was smaller (median 81.3 [95% CI, 74.2-88.5] vs. 64.5 [54.8-74.2] mL/m2; P = 0.04), the LAA volume was smaller (10.1 [9.0-11.3] vs. 6.5 [4.5-8.5] mL/m2; P = 0.008), and the RAA volume was larger (10.8 [9.1-12.4] vs. 14.1 [11.6-16.6] mL/m2; P = 0.044) in the RAF group. The RA volume was not significantly different between the groups (73.6 [66.8-80.3] vs. 68.1 [57.1-79.1] mL/m2; P = 0.47). The RAF group had smaller PVs (1.44 [1.33-1.55] vs. 1.12 [0.94-1.30] cm2/m2 for the left inferior PV; P = 0.01). Both the LA-EAT and RA-EAT volumes were smaller in the RAF group than the LAF group (4.2 [2.8-5.6] vs. 9.1 [7.8-10.4] mL/m2; P < 0.001 and 5.3 [4.3-6.3] vs. 9.5 [8.4-10.6] mL/m2; P < 0.001, respectively). Conclusion: RAF was structurally characterized by predominant RAA enlargement, small left atrium, and less EAT surrounding the atria. Electrical properties that determine the features of AF (RAF vs. LAF) may be genetically linked to structural properties.

Multiple pacemaker lead breakages due to clavicle dislocation following clavicle fracture.

A 58-year-old man undergoing cardiac resynchronization therapy with a defibrillator in his right subcostal area fell from his bed, leading to fracture of the right clavicle. Serial radiographs showed dislocation of the distal clavicle 2 months after the initial fracture. Lead parameters dramatically changed after dislocation of the distal clavicle. Radiography indicated that the device leads seemed to be compressed by the distal clavicle in certain positions of the right upper limb. It was likely that various movements of the right upper limb during his daily life insidiously damaged the device leads, leading to the lead breakages.

Trade-off between elimination of premature ventricular complexes and loss of synchronized left ventricular pacing improved cardiac function in a patient with heart failure.

Synchronized left ventricular pacing (sLVP) via adaptive cardiac resynchronization therapy (aCRT) algorithm might enhance the efficacy of CRT. A 71-year-old female was admitted with the diagnosis of heart failure. Electrocardiograms revealed left bundle branch block with QRS width of 144 ms, and frequent premature ventricular complexes (PVCs). A CRT device was implanted, and sLVP via a CRT algorithm was provided. Frequent PVCs arising from the His-bundle suppressed effective sLVP percentage. Radiofrequency application at the His-bundle successfully eliminated the PVCs, but induced complete atrioventricular (AV) block, leading to loss of sLVP. These procedures remarkably improved the patient's cardiac function, suggesting the advantage of PVC elimination overweighed the disadvantage of loss of sLVP.

Uncoupling endocardial bundles coupled by an epicardial bundle in the left atrium and pulmonary veins.

Uncoupling of the endocardial bundles in the left atrium was suggested during modified posterior wall isolation. Although this fact may not be observed because of the possible bridging conduction by epicardial bundles in humans, partially failed transmural ablation in the atrial roof may have iatrogenically unveiled this fact.

Mid-term outcomes of delivery catheter-based and stylet-based right ventricular septal pacing: Follow-up results from a multicenter, prospective, randomized study.

Background: The Mt FUJI study was a multicenter, prospective, randomized, single-blind, controlled trial comparing delivery catheter-based and stylet-based right ventricular (RV) lead placement at the RV septum. This study extended the follow-up duration to 1 year after implantation. Methods: Seventy patients with pacemaker indications for atrioventricular block were randomly assigned to the delivery catheter and stylet groups. We compared the mid-term efficacy and safety between the two groups at 1 year after implantation. The primary outcome was the change in the left ventricular ejection fraction (LVEF), and the secondary outcomes were changes in brain natriuretic peptide (BNP) levels, lead parameters, paced QRS duration, and the incidence of adverse events. Results: At the 1-year follow-up, no significant differences were observed in the changes in the LVEF (+1.0% ± 8.6% vs. +3.1% ± 8.1%, p = .332), BNP levels (+8.0 [-11.1, 26.5] pg/mL vs. -8.7 [-15.3, 13.2] pg/mL, p = .193), or lead performance between the delivery catheter and stylet groups. The QRS duration was significantly shorter in the delivery catheter group than in the stylet group (128 ± 23 ms vs. 146 ± 17 ms, p < .001). All-cause death, hospitalization for heart failure, new development of atrial fibrillation, and pacing-induced cardiomyopathy occurred in seven patients in the delivery catheter group and five in the stylet group. Conclusion: The delivery catheter system was similarly useful and safe compared to the stylet system in the mid-term follow-up from the Mt FUJI trial. Further long-term evaluations are warranted.

Inter-atrial epicardial muscular fibers as a possible source of atrial tachyarrhythmias.

A 22-year-old woman without structural heart disease underwent catheter ablation of frequent premature atrial contractions (PACs). Radiofrequency applications from both the right and left atrium were effective in suppressing or eliminating these PACs. The distance between the right atrial ablation site and the successful ablation site at the right-sided pulmonary venous carina measured 18 mm on the CARTO map, and no cardiac structure, i.e. the inter-atrial septum, was present between those sites. Taken together, the epicardial muscular fibers in the inter-atrial groove were considered to play a role as an arrhythmogenic source of this atrial tachyarrhythmia. Learning objective: Epicardial muscular fibers connecting the right atrium and right-sided pulmonary venous carina are known to preclude isolation of the veins. This epicardial connection in the interatrial groove can be an arrhythmogenic source or part of a reentrant circuit of atrial tachyarrhythmias.

Impact of catheter ablation and subsequent recurrence of atrial fibrillation on glucose status in patients undergoing continuous glucose monitoring.

Although glucose metabolism and atrial fibrillation (AF) have complex interrelationships, the impact of catheter ablation of AF on glucose status has not been well evaluated. Continuous glucose monitoring (CGM) with a FreeStyle Libre Pro (Abbott) was performed for 48 h pre-procedure, during the procedure, and for 72 h post-procedure in 58 non-diabetes mellitus (DM) patients with symptomatic AF and 20 patients with supraventricular or ventricular arrhythmias as a control group. All ablation procedures including pulmonary vein isolation were performed successfully. Glucose levels during procedures consistently increased in the AF and control groups (83.1 ± 16.1 to 110.0 ± 20.5 mg/dL and 83.3 ± 14.7 to 98.6 ± 16.3 mg/dL, respectively, P < 0.001 for both), and Δ glucose levels (max minus min/procedure) were greater in the AF group than control group (P < 0.001). There was a trend toward higher mean glucose levels at 72 h after the procedures compared with those before the procedures in both the AF and control groups (from 103.4 ± 15.6 to 106.1 ± 13.0 mg/dL, P = 0.063 and from 100.2 ± 17.1 to 102.9 ± 16.9 mg/dL, P = 0.052). An acute increase in glucose level at the time of early AF recurrence (N = 9, 15.5%) could be detected by simultaneous CGM and ECG monitoring (89.7 ± 18.0 to 108.3 ± 30.5 mg/dL, P = 0.001). In conclusion, although AF ablation caused a statistically significant increase in the glucose levels during the procedures, it did not result in a pathologically significant change after ablation in non-DM patients. Simultaneous post-procedure CGM and ECG monitoring alerted us to possible acute increases in glucose levels at the onset of AF recurrence.

Potential benefit of Bachmann's bundle pacing on left ventricular performance in patients with cardiac resynchronized therapy.

BACKGROUND: Right atrial (RA) appendage (RAA) pacing is reported to impair hemodynamic benefits of cardiac resynchronization therapy (CRT) through a considerable delay of left atrial (LA) contraction, which compromises appropriate balance of atrioventricular (AV) and left ventricular (LV) synchrony. Potential usefulness of Bachmann's bundle (BB) pacing to solve the problem remains to be confirmed. METHODS AND RESULTS: Atrial synchrony and LV performance was investigated by echocardiography in 25 patients undergoing pacemaker implantation with preserved AV conduction and LV function (Group I), and 15 patients receiving CRT (Group II). In Group I, RAA pacing (AAI mode, n=10) increased P-wave duration (PWD) and RA-to-LA contraction delay (IAMD) compared with sinus rhythm (132±14 and 35±12 ms vs. 108±16 and 13±13 ms, P<0.001). The delayed LA contraction was associated with early interruption of LV filling, leading to an impairment of LV performance (Tei index: 0.43±0.12 vs. 0.34±0.09, P<0.01). BB pacing (AAI, n=15) did not cause such undesirable effects. In Group II, RA (BB)-paced biventricular pacing (DDD) reduced PWD and IAMD compared with RA-sensed biventricular pacing (VDD) (102±14 and -3±13 ms vs. 117±10 and 21±18 ms, P<0.001). This restoration of atrial synchrony was associated with significant improvement of LV performance (Tei index: 0.56±0.18 vs. 0.62±0.16, P<0.05). CONCLUSIONS: BB pacing preserves atrial synchrony, and might be more favorable than RAA pacing for maximizing hemodynamic efficacy of CRT.

Conversion to partial isthmus-dependent flutter during cavotricuspid isthmus ablation: The utility of Advisor HD grid in identifying local fragment electrograms.

Complete block creation by radiofrequency (RF) ablation at the cavotricuspid isthmus (CTI) is a highly successful procedure for the treatment of typical atrial flutter (AFL). Occasionally, a rare type of AFL, such as lower or upper loop reentry, or partial isthmus-dependent flutter, can coexist with typical right AFL. A 73-year-old man underwent CTI ablation for a clockwise CTI-dependent typical atrial flutter. During the ablation procedure, the morphology of the flutter wave changed in the surface electrocardiogram and endocardial atrial activation sequence, suggesting that the typical AFL had converted to another AFL (AFL2). High-density mapping using the HD grid catheter could not reveal the reentrant circuit of AFL2 but detected a critical conduction gap at the boundary between the inferior vena cava and CTI. There was also an impulse collision in the remaining CTI. The RF application at the gap terminated the AFL2 and completed the block line of the CTI. Based on these findings, AFL2 was comparable with partial isthmus-dependent flutter. The present case demonstrates the utility of high-density mapping with a HD grid for the identification of small amplitude high-frequency electrograms at critical sites of the arrhythmia. Learning objective: A rare type of atrial flutter (AFL) can coexist with typical AFL. In such cases, a high-density mapping is useful to identify the critical portion of the reentrant circuit. The Advisor HD grid multipolar catheter (Abbott, St Paul, MN, USA) is unique in that it allows bipolar recording perpendicular and parallel to the splines via 16 electrodes. In this case report, high density mapping using HD grid catheter identified small amplitude high-frequency electrograms at critical sites of the arrhythmia.