Intracardiac Recordings Research Articles

Pseudo-elevation of conduction system pacing threshold through parallel connection of an intracardiac electrogram recording system.

Parallel connection of an electrophysiology recording system (EP system) to equipment for conduction system pacing (CSP) has been widely used for fine monitoring of intracardiac electrograms and pacing evaluation. We experienced a case showing unexpected pacing threshold exacerbation under specific conditions when the EP system was connected in parallel. We evaluated the underlying mechanism using an ex vivo model. An ex vivo pacing and intracardiac electrogram monitoring model was generated using an oscilloscope, pacing system analyzer (PSA), EP system, and simulated heart. The discrepancy between expected output at the PSA and the actual measured output value at the simulated heart was measured under various conditions and using various combinations of pacing equipment. Parallel connection of the EP system was associated with reduced electrical output from the PSA as recorded at the simulated heart. The unexpected adverse effects were particularly noticeable when using an RMC-5000 EP system with the pacing function on. The trouble is completely resolved by simply turning off the pacing function of the system. There is a possibility that the EP system might increase the pacing threshold in CSP when the PSA and EP system is are deployed in parallel. The issue may provoke pseudo failure of CSP due to the high pacing threshold. When the RMC-5000 is used for conduction system pacing in parallel with a PSA for the pacing test, the pacing function of RMC-5000 should be turned off.

Activin receptor-like kinase 4 haplodeficiency alleviates the cardiac inflammation and pacing-induced ventricular arrhythmias after myocardial infarction.

Background: Inflammation process is an important determinant for subsequent changes in cardiac function and remodeling after acute myocardial infarction (MI). Recent studies have implicated that ALK4 haplodeficiency improves cardiac function after MI. However, it remains unknown if the beneficial effects are partly attributed to ALK4 haplodeficiency-induced modulation on inflammatory response in the inflammatory phase of MI. In this research, we aimed to explore the mechanism of ALK4 haplodeficiency in the inflammatory stage of MI.Methods: ALK4, CD16, and CD14 were detected in peripheral blood mononuclear cells (PBMCs) isolated from MI patients and healthy volunteers. ALK4 haplodeficiency (ALK4+/-) mice and wild-type (WT) littermates were randomly divided into the sham group and the MI group. Inflammation cytokines and chemokines were measured. Echocardiography and intracardiac electrophysiological recordings were performed on the 3rd day and the 7th day after MI operation. ALK4 expression and inflammation cytokines were also detected in LPS- or IL-4-stimulated bone marrow-derived macrophages (BMDM) from the ALK4+/- mice and WT littermates.Results: ALK4 gene expression in circulating monocytes of MI patients was higher than that in those of healthy volunteers. Cardiac inflammation and vulnerability of ventricular arrhythmia after acute myocardial injury are significantly alleviated in ALK4+/- mice as compared to WT littermates. On the 3rd day post-MI, the level of M1 macrophages were decreased in ALK4+/- mice as compared to WT littermates, while the level of M2 macrophages were increased on the 7th day post-MI. BMDM isolated from ALK4+/- mice displayed reduced secretion of pro-inflammation cytokines after stimulation by LPS in hypoxic condition and increased secretion of anti-inflammation cytokines after stimulation by IL-4. As a result, the haplodeficiency of ALK4 might be responsible for reduced inflammation response in the post-MI stage.Conclusions: ALK4 haplodeficiency reduces cardiac inflammation, improves cardiac function, and finally reduces the vulnerability of ventricular arrhythmia in the inflammatory stage after MI.

Efficacy of Patient-Specific Strategy: Catheter Ablation Strategy of Persistent Atrial Fibrillation Based on Morphological Repetitiveness by Periodicity and Similarity

Efficacy of Patient-Specific Strategy: Catheter Ablation Strategy of Persistent Atrial Fibrillation Based on Morphological Repetitiveness by Periodicity and Similarity

Automatic reconstruction of the left atrium activation from sparse intracardiac contact recordings by inverse estimate of fibre structure and anisotropic conduction in a patient-specific model.

Electric conduction in the atria is direction-dependent, being faster in fibre direction, and possibly heterogeneous due to structural remodelling. Intracardiac recordings of atrial activation may convey such information, but only with high-quality data. The aim of this study was to apply a patient-specific approach to enable such assessment even when data are scarce, noisy, and incomplete. Contact intracardiac recordings in the left atrium from nine patients who underwent ablation therapy were collected before pulmonary veins isolation and retrospectively included in the study. The Personalized Inverse Eikonal Model from cardiac Electro-Anatomical Maps (PIEMAP), previously developed, has been used to reconstruct the conductivity tensor from sparse recordings of the activation. Regional fibre direction and conduction velocity were estimated from the fitted conductivity tensor and extensively cross-validated by clustered and sparse data removal. Electrical conductivity was successfully reconstructed in all patients. Cross-validation with respect to the measurements was excellent in seven patients (Pearson correlation r > 0.93) and modest in two patients (r = 0.62 and r = 0.74). Bland-Altman analysis showed a neglectable bias with respect to the measurements and the limit-of-agreement at -22.2 and 23.0 ms. Conduction velocity in the fibre direction was 82 ± 25 cm/s, whereas cross-fibre velocity was 46 ± 7 cm/s. Anisotropic ratio was 1.91±0.16. No significant inter-patient variability was observed. Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps correctly predicted activation times in late regions in all patients (r = 0.88) and was robust to a sparser dataset (r = 0.95). Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps offers a novel approach to extrapolate the activation in unmapped regions and to assess conduction properties of the atria. It could be seamlessly integrated into existing electro-anatomic mapping systems. Personalized Inverse Eikonal model from cardiac Electro-Anatomical Maps also enables personalization of cardiac electrophysiology models.

Variation of P-wave indices in paroxysmal atrial fibrillation patients before and after catheter ablation

The effects of pulmonary vein isolation in the surface electrocardiogram of patients with paroxysmal atrial fibrillation are analyzed in this paper using non-invasive markers for early detection of the arrhythmia recurrences.Several features have been extracted on P-waves of V1 lead for paroxysmal atrial fibrillation patients who underwent catheter ablation of pulmonary veins for restoring sinus rhythm permanently. Surface ECG was simultaneously recorded along with intracardiac recordings starting from the beginning of the intervention until half an hour after the catheter ablation successfully ended. Significant difference between the means before and after catheter ablation have been observed for the cross-correlation index, kurtosis and amplitude dispersion of P-waves.A logistic regression has been applied to all the descriptors and pointed to the amplitude dispersion index, as well as the minimum gradient joint with kurtosis of P-waves prior to catheter ablation as good predictors of recurrence of atrial fibrillation (78% accuracy). It is important to note how using a few descriptors good classification results are achieved. This study opens a door to early detection of atrial fibrillation recurrences using markers obtained by non-invasive methods.

Relationship between atrial fibrillatory rate based on analysis of a modified base-apex surface electrocardiogram analysis and the results of transvenous electrical cardioversion in horses with spontaneous atrial fibrillation

ObjectivesTo compare the atrial fibrillatory rate (AFR) derived from a local right atrial intracardiac recording (RA-FR) and from a single-lead surface electrocardiogram (ECG) during atrial fibrillation (AF) and to evaluate the correlation with transvenous electrical cardioversion (TVEC) threshold (in Joules), number of shocks and cardioversion success rate in horses. AnimalsECGs and clinical records of horses with AF treated by TVEC. Horses were included if a simultaneous recording of the right atrial intracardiac electrogram and a modified base-apex ECG were available. Materials and methodsClinical records of horses with AF treated by TVEC were reviewed. Three-minute long episodes of simultaneous electrograms and surface ECG during AF were selected for analysis and compared using Bland-Altman analysis. The mean RA-FR was measured from the deflections on the intracardiac electrogram, while the AFR was extracted from the surface ECG using spatiotemporal QRS and T-wave cancellation. ResultsSeventy-three horses satisfied the inclusion criteria. The mean difference between RA-FR and AFR was −13 fibrillations per minute (fpm), the 95% limits of agreement were between −66 and 40 fpm, and there was a moderate (ρ = 0.65) correlation between RA-FR and AFR (p < 0.001). Neither RA-FR nor AFR appeared to influence the TVEC cardioversion threshold or the number of TVEC shocks applied. ConclusionsThe AFR may allow non-invasive long-term monitoring of AF dynamics. Neither RA-FR nor AFR could be used to predict the minimal defibrillation threshold for TVEC.

Non-invasive Spatial Mapping of Frequencies in Atrial Fibrillation: Correlation With Contact Mapping.

Introduction: Regional differences in activation rates may contribute to the electrical substrates that maintain atrial fibrillation (AF), and estimating them non-invasively may help guide ablation or select anti-arrhythmic medications. We tested whether non-invasive assessment of regional AF rate accurately represents intracardiac recordings.Methods: In 47 patients with AF (27 persistent, age 63 ± 13 years) we performed 57-lead non-invasive Electrocardiographic Imaging (ECGI) in AF, simultaneously with 64-pole intracardiac signals of both atria. ECGI was reconstructed by Tikhonov regularization. We constructed personalized 3D AF rate distribution maps by Dominant Frequency (DF) analysis from intracardiac and non-invasive recordings.Results: Raw intracardiac and non-invasive DF differed substantially, by 0.54 Hz [0.13 – 1.37] across bi-atrial regions (R2 = 0.11). Filtering by high spectral organization reduced this difference to 0.10 Hz (cycle length difference of 1 – 11 ms) [0.03 – 0.42] for patient-level comparisons (R2 = 0.62), and 0.19 Hz [0.03 – 0.59] and 0.20 Hz [0.04 – 0.61] for median and highest DF, respectively. Non-invasive and highest DF predicted acute ablation success (p = 0.04).Conclusion: Non-invasive estimation of atrial activation rates is feasible and, when filtered by high spectral organization, provide a moderate estimate of intracardiac recording rates in AF. Non-invasive technology could be an effective tool to identify patients who may respond to AF ablation for personalized therapy.

The Wenckebach Phenomenon

Medicine has many great pioneers, and in 1899, one such pioneer - Karel Frederik Wenckebach made a discovery which, even to this day, remains one of the fundamental concepts within electrophysiology.Since the Wenckebach Phenomenon was first described, the field of electrophysiology has developed at a rapid pace, allowing us to observe this behaviour, and its complexities, in many new ways. In a similar way, this chapter will illustrate Wenckebach behaviour across a spectrum of modalities from the 12 lead ECG, through to the intra-cardiac recordings from both electrophysiological studies and implantable cardiac devices. In doing so, we continue to shed light on the phe-nomenon first identified through Wenckebach’s meticulous attention to detail some 120 years ago.

Electrocardiographic imaging including intracardiac information to achieve accurate global mapping during atrial fibrillation

Atrial fibrillation (AF) is characterized by complex and irregular propagation patterns. Noninvasive electrocardiographic imaging (ECGI) has been tested during AF conditions with promising results. However, current regularization methods face important challenges in this type of unstable electrical activity scenarios. Combination of intracardiac and non-invasive simultaneous recordings could improve ECGI performance and allow real-time global mapping of complex AF patterns. In this work, we propose an ECGI method that incorporates intracardiac measurements as a constraint in a reformulation of the classical Tikhonov method. We used realistic mathematical models of atria and torso that simulates a wide number of epicardial electrical activity patterns. Body surface potentials were obtained from simulated electrograms (EGMs) by using Boundary Element Method and corrupted with Gaussian noise. Epicardial potentials were estimated using inverse problem with Tikhonov regularization, including intracavitary information as a second constraint. Results showed that first-order Constrained Tikhonov formulation provided more reliable reconstructions than the classical Tikhonov approach in AF conditions using at least 32 uniformly distributed endocardial EGMs (CC between 0.87 and 0.28, depending on the AF complexity). Constrained Tikhonov provided more accurate spatial mass functions (SMF) of PS locations (CCSMF between 0.24 and 0.86). This methodology was tested on real patient data, obtaining a mean DF RMSE of 0.85 Hz, outperforming the classical Tikhonov approach. Limitations of this study include the fact that the model considered endocardium and epicardium as a single layer. Further research will include endocardium–epicardium bilayer model approximations and validation using more real patient data.

Abstract 14738: Classification of Atrial Fibrillation by Deep Learning of Electrogram Shapes versus Rate and Regularity

Introduction: It is unclear whether atrial fibrillation (AF) is best identified on intracardiac recordings by varying shape, rapid rate or extent of irregularity. Prioritizing these features may improve device diagnosis of AF. Hypothesis: AF can be separated from organized atrial flutter (AFL) by electrogram shape, independent of the contributions of rate or regularity. Methods: In 86 patients (25 female, age 65±11 years) we trained a convolutional neural network (CNN) to classify AF or AFL from 64 unipolar electrograms of persistent AF recorded for 60 seconds. In cases labelled as AF, we modified inputs by progressively regularizing (a) electrogram shape; (b) rate or (c) regularity in timing, to define which switched the classification to AFL. Results: The CNN provided a c-statistic of 0.95 ± 0.05 to identify AF or AFL in independent test cohorts not used for training, using 10-fold cross validation. Fig A shows AF in which progressive regularization of shape and timing from #1 to #4 flipped CNN classification into AFL in 45%. EGMs with 100% consistent shape and timing were classified by their cycle length (CL=1/rate): ~90% AF for CL &lt; 175 ms, ~80% AFL for CL from 200-280 ms. Fig. B shows sequences simulated from patient-specific EGMs of AF that were classified as AF in 91 ± 12% of cases even if regular with CL of 200-280 ms, showing AF classification based on EGM shape alone. Figure B illustrates some ‘AF pathognomic’ electrogram shapes in red. Conclusions: AF may be identified by specific EGM shape patterns independent of regularity or rate. Regularity in shape and timing contribute ~45% to AFL classification, and adding CL explains up to 80%. Studies are required to study the mechanistic basis and clinical implications of specific AF-electrogram shapes.

Incremental benefit of a novel signal recording system during mapping and ablation.

Current electrophysiology signal recording and mapping systems have limited dynamic range (DR) and bandwidth, which causes loss of valuable information during acquisition of cardiac signals. We evaluated a novel advanced signal processing platform with the objective to obtain and assess additional information of clinical importance. Over 10 canines, we compared intracardiac recordings within all cardiac chambers, in various rhythms, in pacing and during radiofrequency (RF) ablation across two platforms; a conventional system and the PURE EP™ [(PEP); Bio Sig Technologies, Inc., Los Angeles, CA, USA]. Recording cardiac signals with varying amplitudes were consistently and reproducibly observed, without loss of detail or introduction of artefact. Further the amplitude of current of injury (COI) on the unipolar signals correlated with the instantaneous contact force (CF) recorded on the sensing catheter in all the animals (r2 = 0.94 in ventricle). The maximum change in the unipolar COI correlated with the change in local electrogram amplitude during non-irrigated RF ablation (r2 = 0.61 in atrium). Reduction in artefact attributable to pacing (20 sites) and noise during ablation (48 sites) was present on the PEP system. Within the PEP system, simultaneous display of identical signals, filtered differently, aided the visualization of discrete conduction tissue signals. Compared to current system, the PEP system provided incremental information including identifying conduction tissue signals, estimates of CF and a surrogate for lesion formation. This novel signal processing platform with increased DR and minimal front-end filtering may be useful in clinical practice.

An intriguing case of regular RR and QRS alternans during idiopathic left posterior fascicle ventricular tachycardia

This study represents a case of idiopathic left posterior fascicle ventricular tachycardia (LPF-VT), which is intriguing due to regular alternation of short-long RR intervals and QRS morphology. Transthoracic echocardiogram analysis did not detect any structural heart disease. A baseline electrophysiological study was performed. Intracardiac recording during tachycardia showed V-A dissociation, confirming the final diagnosis of idiopathic LPF-VT. No regularity in the monomorphic VT was recorded. Previous relevant studies suggested that a single focus with two exits in distal branches of the left posterior fascicle or two different foci localized in the Purkinje-myocardial network of the left posterior fascicle can clarify the mechanisms. Our team proposed an additional explanation that combines the physiological refractory period with the Ashman phenomenon in individual reentrant LPF-VT circuit.

Diagnosis and treatment of atrioventricular nodal reentrant tachycardia: a case report illustrating clinical management and ablation strategy.

BackgroundAtrioventricular nodal reentrant tachycardia (AVNRT) is a common supraventricular arrhythmia that is frequently encountered in an otherwise healthy patient population. Recent guidelines of the European Society of Cardiology underline the role of catheter ablation in the long-term management of these patients.Case summaryThis case describes the clinical presentation and treatment options in a patient with typical slow/fast AVNRT, the most common subform of AVNRT, where antegrade conduction occurs over the slow pathway and retrograde conduction over the fast pathway. The ablation strategy in these patients is illustrated based on intracardiac recordings in combination with per-procedural three-dimensional imaging.DiscussionAtrioventricular nodal reentrant tachycardia is a common arrhythmia with good prognosis but significant impact on quality of life of affected patients. Catheter ablation should be considered early as it can be performed safely and with a very high success rate.

Improved real-time recordings using the fourth-generation cryoballoon technology-detection of dual fascicle electrograms.

We aimed to analyze the rate of visualization of real-time (RT) recordings and dual fascicle electrograms in our first series of patients treated with the fourth-generation cryoballoon (CB) device. All consecutive patients who underwent CB ablation using the fourth-generation technology were included in the analysis. In all procedures, we used a 28-mm CB placed via a single transseptal puncture guided by intracardiac ultrasound. A 20-mm octapolar intraluminal circular catheter was used for intracardiac recordings. A single 180-s freeze strategy was employed. A total of 129 patients (72.9% male, mean age 60.1 ± 10.9 years) were enrolled in the study. RT recordings were detected in 445 (86.2%) pulmonary veins (PVs). Specifically, RT recordings were visualized in 115 left superior PVs (89.2%), 107 left inferior PVs (82.9%), 118 right superior PVs (91.4%), and 105 right inferior PVs (81.3%). Dual fascicle electrograms could be observed only in patients in sinus rhythm, in 23 of 396 PVs (5.8%). They were most commonly observed in the left superior PV (8.1%), somewhat less in both inferior veins (6.1%), while this phenomenon was least frequent in the right superior PV (3.0%). By using the fourth-generation CB, we report a specific pattern of isolation represented by a sequential isolation of two apparently distinct PV fascicles during a single CB freeze delivery. This phenomenon occurred in 5.8% of PV ablations. Of note, the rate of visualization of RT isolation with this novel CB was very high and could be documented in 86.2% of PVs.

Implication of the distinctive bipolar intracardiac electrograms for ventricular arrhythmias arising from different regions of ventricular outflow tract.

To investigate the characteristics of bipolar intracardiac electrograms (bi-EGMs) in target sites of ventricular arrhythmias (VAs) originating from different regions of ventricular outflow tract (VOT). Two hundred and seventy patients undergoing first-time ablation for VAs originated from distal great cardiac vein (DGCV), aortic sinus cusps (ASCs), or pulmonary sinus cusps (PSCs) were enrolled in present study. Local intracardiac bipolar recordings on 243 successful sites and 506 attempted but unsuccessful ablation sites were analysed. Specific potentials in bi-EGMs on successful sites were more common compared with unsuccessful sites (76.95%, 187/243 vs. 25.49%, 129/506, P < 0.05). A total of 60.00% (81/135) patients in ASCs group presented a presystolic short-duration fractionated potential, higher than 23.21% (13/56) in DGCV and 23.08% (12/52) in PSCs (all P < 0.05); 44.23% (23/52) patients in PSC group showed a presystolic high-amplitude discrete potential, while 1.79% (1/56) in DGCV and 2.22% (3/135) in ASCs (all P < 0.05); 41.07% (23/56) patients in DGCV group showed bi-EGMs of presystolic long-duration multicomponent fractionated potential, which was significantly higher than 3.85% (2/52) in PSCs and 4.44%(6/135) in ASCs (all P < 0.05). Distinctive morphology of bi-EGMs during VAs can be found in different regions of VOT, which probably due to changes in the arrangements of myocardial sleeves. Correct identification and better understanding of the distinctive features of these bi-EGMs with regards to the anatomic location was important, the presence of specific potentials may add help in successful ablation.

Evidence of structural and functional plasticity occurring within the intracardiac nervous system of spontaneously hypertensive rats.

Plasticity is a fundamental property of neurons in both the central and peripheral nervous systems, enabling rapid changes in neural network function. The intracardiac nervous system (ICNS) is an extensive network of neurons clustered into ganglionated plexi (GP) on the surface of the heart. GP neurons are the final site of neuronal control of heart rhythm, and pathophysiological remodeling of the ICNS is proposed to feature in multiple cardiovascular diseases, including heart failure and atrial fibrillation. To examine the potential role of GP neuron plasticity in atrial arrhythmia and hypertension, we developed whole cell patch clamp recording techniques from GP neurons in isolated ICNS preparations from aged control (Wistar-Kyoto) and spontaneously hypertensive rats (SHRs). Anesthetized SHRs showed frequent premature ventricular contractions and episodes of atrial arrhythmia following carbachol injection, and isolated SHR atrial preparations were susceptible to pacing induced atrial arrhythmia. Whole cell recordings revealed elevated spontaneous postsynaptic current frequency in SHR GP neurons, as well as remodeled electrophysiology, with significant decreases in action potential amplitude and half-width. SHRs also showed a parallel increase in the number of cholinergic neurons and adrenergic glomus cells in cardiac ganglia, a higher proportion of synaptic α7-subunit but not β2-containing nicotinic receptors, and an elevation in the number of synaptic terminals onto GP neurons. Our data show that significant structural and functional plasticity occurs in the intracardiac nervous system and suggest that enhanced excitability through synaptic plasticity, together with remodeling of cardiac neuron electrophysiology, contributes to the substrate for atrial arrhythmia in hypertensive heart disease.NEW & NOTEWORTHY We have developed intracardiac neuron whole cell recording techniques in atrial preparations from control and spontaneous hypertensive rats. This has enabled the identification of significant synaptic plasticity in the intracardiac nervous system, including enhanced postsynaptic current frequency, increased synaptic terminal density, and altered postsynaptic receptors. This increased synaptic drive together with altered cardiac neuron electrophysiology could increase intracardiac nervous system excitability and contribute to the substrate for atrial arrhythmia in hypertensive heart disease.

Noninvasive Assessment of Complexity of Atrial Fibrillation: Correlation With Contact Mapping and Impact of Ablation.

It is difficult to noninvasively phenotype atrial fibrillation (AF) in a way that reflects clinical end points such as response to therapy. We set out to map electrical patterns of disorganization and regions of reentrant activity in AF from the body surface using electrocardiographic imaging, calibrated to panoramic intracardiac recordings and referenced to AF termination by ablation. Bi-atrial intracardiac electrograms of 47 patients with AF at ablation (30 persistent, 29 male, 63±9 years) were recorded with 64-pole basket catheters and simultaneous 57-lead body surface ECGs. Atrial epicardial electrical activity was reconstructed and organized sites were invasively and noninvasively tracked in 3-dimension using phase singularity. In a subset of 17 patients, sites of AF organization were targeted for ablation. Body surface mapping showed greater AF organization near intracardially detected drivers than elsewhere, both in phase singularity density (2.3±2.1 versus 1.9±1.6; P=0.02) and number of drivers (3.2±2.3 versus 2.7±1.7; P=0.02). Complexity, defined as the number of stable AF reentrant sites, was concordant between noninvasive and invasive methods (r2=0.5; CC=0.71). In the subset receiving targeted ablation, AF complexity showed lower values in those in whom AF terminated than those in whom AF did not terminate (P<0.01). AF complexity tracked noninvasively correlates well with organized and disorganized regions detected by panoramic intracardiac mapping and correlates with the acute outcome by ablation. This approach may assist in bedside monitoring of therapy or in improving the efficacy of ongoing ablation procedures.

Para-Hisian Pacing: New InsightsofanOldPacingManeuver.

More than 2 decades ago, para-Hisian pacing was introduced to assess the pattern of retrograde conduction during electrophysiological studies. Although there is no ideal maneuver for every patient and condition, para-Hisian pacing is a valuable and handy strategy to differentiate between retrograde conduction over the atrioventricular node and the accessory pathways. The dynamic behavior of para-Hisian pacing, in a region with unique anatomical features, can produce various activation patterns and intriguing electrophysiological phenomena. Although the demonstration of a retrograde nodal activation pattern during para-Hisian pacing does not rule out the presence of an accessory pathway, evidence of retrograde conduction over an accessory pathway does not prove its active role in the culprit tachycardia. Multipolar His bundle recordings, detailed atrial mapping, and recognition of the truly captured structures and the impact of temporal changes of autonomic tone or pacing rates, are essential keys for accurate interpretation of this maneuver that may ultimately guide judicious catheter ablation of the arrhythmic substrate. This review aims to summarize the practical usefulness and potential pitfalls of the para-Hisian pacing maneuver, focusing on the interpretation of electrocardiograms and intracardiac recordings.

A novel pacing maneuver to verify the postpacing interval minus the tachycardia cycle length while adjusting for decremental conduction: Using “dual-chamber entrainment” for improved supraventricular tachycardia discrimination

The postpacing interval (PPI) minus the tachycardia cycle length (TCL) is frequently used to investigate tachycardias. However, a variety of issues (eg, failure to entrain, decremental conduction, and oscillating TCLs) can make interpretation of the PPI-TCL challenging. The purpose of this study was to investigate a novel maneuver to confirm the PPI-TCL value without using either the ventricular PPI or the TCL interval and to assess the ability of this maneuver to identify decremental conduction and differentiate supraventricular tachycardias. We analyzed 77 intracardiac recordings from patients (age 25 ± 20 years; 40 female) who underwent catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) or orthodromic reciprocating tachycardia (ORT) with a concealed pathway. We calculated the PPI-TCL, the AH-corrected PPI-TCL, and estimated the PPI-TCL using "dual-chamber entrainment" calculated as [PPIV - TCL = Stim(A→V) + Stim(V→A) - PPIA]. The PPI-TCL calculated by dual-chamber entrainment highly correlated with the observed and AH-corrected PPI-TCL (R2= 0.79 and 0.96, respectively; P <.001]. A dual-chamber entrainment PPI-TCL value of 80 ms correctly differentiated all AVNRT from septal ORT cases, whereas the standard PPI-TCL and AH-corrected PPI-TCL methods were incorrect in 14% and 6% of cases, respectively. Dual-chamber entrainment identified 3 ± 10 ms of additional decremental conduction beyond AH prolongation, including 4 pathways with significant (>10 ms) decrement. Dual-chamber entrainment estimates the PPI-TCL value without using either the ventricular PPI or the TCL interval. This maneuver adjusts for all decremental conduction, including within concealed pathways, where a dual-chamber entrainment PPI-TCL value >80 ms favors AVNRT over ORT. This maneuver can be used to verify the observed PPI-TCL value in challenging cases.

Analytical approaches for analysis of intracardiac bipolar electrograms during atrial fibrillation

Atrial fibrillation is the most common type of cardiac arrhythmias encountered in clinical practice, in which heart muscles shows chaotic atrial depolarization and uncoordinated contraction. Underlying mechanisms of atrial fibrillation are incompletely understood and widely discussed in the scientific community. The abnormal electrical discharges in atrial repolarization is associated with localized drivers and multiple wavefronts that support the asynchronous heart rhythm. In this paper, a briefly overview of conventional techniques focus on mapping drivers of myocardial fibrillation and their application are discussed. We also introduce a novel mapping algorithm which is aimed to identity features of wavefront propogation and analyze the relative changes of generalized instantaneous dominant frequency calculated from intracardiac recordings. Our clinical trials showed that proposed algorithm provides insightful and useful information about triggered abnormal activity during atrial fibrillation, that potentially can be used for catheter ablation therapy.