Sinus Rhythm Electrogram Research Articles

Comparison of voltages between atria: differences in sinus rhythm and atrial fibrillation

BackgroundUltra high-density mapping systems allow for comparison of atrial electroanatomical maps in unprecedented detail. Atrial scar determined by voltages and surface area between atria, rhythm and atrial fibrillation (AF) types was assessed.MethodsLeft (LA) and right atrial (RA) maps were created using Rhythmia HDx in patients listed for ablation for paroxysmal (PAF, sinus rhythm (SR) maps only) or persistent AF (PeAF, AF and SR maps). Electrograms on corresponding SR/AF maps were paired for direct comparison. Percentage surface area of scar was assigned low- (LVM, ≤ 0.05 mV), intermediate- (IVM, 0.05–0.5 mV) or normal voltage myocardium, (NVM, > 0.5 mV).ResultsThirty-eight patients were recruited generating 96 maps using 913,480 electrograms. Paired SR-AF bipolar electrograms showed fair correlation in LA (Spearman’s ρ = 0.32) and weak correlation in RA (ρ = 0.19) and were significantly higher in SR in both (LA: 0.61 mV (0.20–1.67) vs 0.31 mV (0.10–0.74), RA: 0.68 mV (0.19–1.88) vs 0.47 mV (0.14–1.07), p < 0.0005 both). Voltages were significantly higher in patients with PAF over PeAF, (LA: 1.13 mV (0.39–2.93) vs 0.52 mV (0.16–1.49); RA: 0.93 mV (0.24–2.46) vs 0.57 mV (0.17–1.69)). Minimal differences were seen in electrogram voltages between atria.Significantly more IVM/LVM surface areas were seen in AF over SR (LA only, p < 0005), and PeAF over PAF (LA: p = 0.01, RA: p = 0.04). There was minimal difference between atria within patients.ConclusionsUltra high-density mapping shows paired electrograms correlate poorly between SR and AF. SR electrograms are typically (but not always) larger than those in AF. Patients with PeAF have a lower global electrogram voltage than those with PAF. Electrogram voltages are similar between atria within individual patients.

Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: a dual-center experience

Abstract Funding Acknowledgements Type of funding sources: None. Background The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. Objective we conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). Methods We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n=14) or recurrent VT (n=7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n=9). The associations of peak-to-peak maximum standard bipolar (BVc) and minibipolar (PentaRay, BVp) with microbipolar (BVμMax) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. Results BVμMax was moderately associated with both BVc (β=0.85, p&amp;lt;0.01) and BVp (β=0.56, p&amp;lt;0.01). BVμMax was 0.98 (95% CI, 0.93-1.04, p&amp;lt;0.01) mV larger than corresponding BVc, and 0.27 (95% CI, 0.16-0.37, p&amp;lt;0.01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm2, p&amp;lt;0.01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm2, p=0.03) regions in microbipolar maps compared to standard bipolar maps. At sites of VT termination (n=14), μBE were of higher amplitude (0.9 [0.8] mV versus 0.4 [0.2] mV, p&amp;lt;0.01), longer duration (117 [66] ms versus 74 [38] ms, p&amp;lt;0.01), and with greater number of peaks (4 [2] versus 2 [1], p&amp;lt;0.01) in sinus rhythm compared to BE. Conclusions Microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for catheter ablation.

Microelectrode voltage mapping for substrate assessment in catheter ablation of ventricular tachycardia: A dual-center experience.

The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. We conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n = 14) or recurrent VT (n = 7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n = 9). The associations of peak-to-peak maximum standard bipolar (BVc ) and minibipolar (PentaRay, BVp ) with microbipolar (BVμMax ) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. BVμMax was moderately associated with both BVc (β = .85, p < .01) and BVp (β = .56, p < .01). BVμMax was 0.98 (95% CI: 0.93-1.04, p < .01) mV larger than corresponding BVc , and 0.27 (95% CI: 0.16-0.37, p < .01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm2 , p < .01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm2 , p = .03) regions in microbipolar maps compared to standard bipolar maps. Late potentials areas were nonsignificantly greater in microelectrode maps, compared to standard electrode maps. At sites of VT termination (n = 14), μBE were of higher amplitude (0.9 [0.8] vs. 0.4 [0.2] mV, p < .01), longer duration (117 [66] vs. 74 [38] ms, p < .01), and with greater number of peaks (4 [2] vs. 2 [1], p < .01) in sinus rhythm compared to BE. microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for CA.

Cardiorespiratory fitness and electroanatomical remodelling in patients with atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Atrial fibrillation (AF) is the most common clinically-relevant arrhythmia. Its initiation and maintenance is linked to the presence cardiovascular risk factors such as hypertension and obesity. Higher cardiorespiratory fitness (CRF) has been associated with a better prognosis. However, specific electroanatomical features associated with baseline CRF have not been described. Purpose Compare electroanatomical substrate across exercise capacity levels in patients with AF Methods Patients referred for de novo AF radiofrequency ablation at the Centre for Heart Rhythm Disorders from August 2017 until June 2020 were screened for inclusion and CRF was evaluated in metabolic equivalents (METs) by a symptom-limited maximal treadmill exercise test using the standard Bruce protocol prior to ablation. Predicted CRF was calculated based on established equations and patients were categorized according to the percentage of predicted CRF achieved; low (&amp;lt;85%), adequate (85-100%) and high (&amp;gt;100%). Total mean and regional peak-to-peak bipolar voltages, percent of low voltage areas (% LVA), conduction velocity (CV) and percent of complex fractionated electrograms (% CFE) in sinus rhythm were compared across groups. Results There were no between-group differences in baseline characteristics, medication use or echocardiographic features. Total mean voltage was significantly lower in the low CRF group compared to both adequate and high CRF. Compared to the high CRF group, roof (3.25 ± 1.2 mV vs 1.9 ± 1.3 mV, p &amp;lt; 0.05), posterior (3.8 ± 1.8 mV vs 1.7 ± 0.9 mV, p &amp;lt; 0.001) and inferior mean voltages (3.4 ± 2 mV vs 1.6 ± 0.7 mV, p &amp;lt; 0.05) were significantly lower in the low CRF group (figure 1A). Furthermore, compared with the adequate CRF group, mean voltages were significantly lower in the posterior (3.7 ± 1.5 mV vs 1.7 ± 0.9 mV, p &amp;lt; 0.001), inferior (3.4 ± 1 mV vs 1.6 ± 0.7 mV, p &amp;lt; 0.001) and lateral (4.2 ± 2.2 mV vs 2.1 ± 1.4 mV, p &amp;lt; 0.05) walls of the low CRF group. Anterior and septal mean voltages were not significantly different across CRF groups (P for trend = 0.07, 0.3 and 0.15, respectively). Conduction velocities were not significantly different across groups. The inferior %LVA was significantly higher in the low CRF (5.6 ± 6%) compared to adequate CRF group (23 ± 18%) (p &amp;lt; 0.05) (figure 1B). Total and regional % CFE was higher in the low CRF compared to adequate and high CRF. Conclusion Participants in the lower baseline CRF category showed significant reductions in regional voltages along with higher fractionation with preserved conduction velocities. Research on the effect of physical activity and CRF on left atrial arrhythmogenic substrate is required. Abstract Figure. Global and regional mV and % LVA by CRF

First-degree atrioventricular block in patients with atrial fibrillation and atrial flutter: the prevalence of intra-atrial conduction delay

PurposePR interval prolongation > 200 ms resulting in the diagnosis of first-degree atrioventricular block (AVB1) is caused by a delay in the AV nodal/His conduction and/or the right intra-atrial conduction (RIAC). The aim of the study was to assess the prevalence of AVB1 due to RIAC delay (AVB1 with normal AH and HV) in patients with atrial fibrillation (AF) and atrial flutter (AFlu).MethodsWe included 1067 consecutive patients (33% female, age 63 ± 13 years) referred for catheter ablation of AF (AF-group) (453 patients), AF and AFlu (136 patients), AFlu (292 patients), and AVNRT/AVRT (186 patients). AH-, HV-, PR-interval, and P-wave duration were measured on the 12-lead ECG and the intracardiac electrograms in sinus rhythm. RIAC delay was defined as a prolonged PR interval > 200 ms with normal AH and HV intervals.ResultsThe prevalence of AVB1 is higher in patients with AFlu (41%) and AF (21%) and patients with both arrhythmias (30%) as compared with a reference group (8%) of patients with AVNRT/AVRT. AVB1 was due to RIAC delay in 42 of 67 patients (63%) in the AF-group, in 37 of 96 patients (39%) in the AFlu-group, and in 17 of 36 patients (47%) in the AF/AFlu group, respectively. AV nodal conduction delay was more common in AFlu patients compared with AF patients.ConclusionRIAC delay is a common underlying cause of AVB1 in patients with AF and AFlu. These findings may impact the prescription of antiarrhythmic and AV-nodal blocking drugs.

Slow uniform electrical activation during sinus rhythm is an indicator of reentrant VT isthmus location and orientation in an experimental model of myocardial infarction

BackgroundTo validate the predictability of reentrant circuit isthmus locations without ventricular tachycardia (VT) induction during high-definition mapping, we used computer methods to analyse sinus rhythm activation in experiments where isthmus location was subsequently verified by mapping reentrant VT circuits. MethodIn 21 experiments using a canine postinfarction model, bipolar electrograms were obtained from 196-312 recordings with 4mm spacing in the epicardial border zone during sinus rhythm and during VT. From computerized electrical activation maps of the reentrant circuit, areas of conduction block were determined and the isthmus was localized. A linear regression was computed at three different locations about the reentry isthmus using sinus rhythm electrogram activation data. From the regression analysis, the uniformity, a measure of the constancy at which the wavefront propagates, and the activation gradient, a measure that may approximate wavefront speed, were computed. The purpose was to test the hypothesis that the isthmus locates in a region of slow uniform activation bounded by areas of electrical discontinuity. ResultsBased on the regression parameters, sinus rhythm activation along the isthmus near its exit proceeded uniformly (mean r2= 0.95±0.05) and with a low magnitude gradient (mean 0.37±0.10mm/ms). Perpendicular to the isthmus long-axis across its boundaries, the activation wavefront propagated much less uniformly (mean r2= 0.76±0.24) although of similar gradient (mean 0.38±0.23mm/ms). In the opposite direction from the exit, at the isthmus entrance, there was also less uniformity (mean r2= 0.80±0.22) but a larger magnitude gradient (mean 0.50±0.25mm/ms). A theoretical ablation line drawn perpendicular to the last sinus rhythm activation site along the isthmus long-axis was predicted to prevent VT reinduction. Anatomical conduction block occurred in 7/21 experiments, but comprised only small portions of the isthmus lateral boundaries; thus detection of sinus rhythm conduction block alone was insufficient to entirely define the VT isthmus. ConclusionsUniform activation with a low magnitude gradient during sinus rhythm is present at the VT isthmus exit location but there is less uniformity across the isthmus lateral boundaries and at isthmus entrance locations. These factors may be useful to verify any proposed VT isthmus location, reducing the need for VT induction to ablate the isthmus. Measured computerized values similar to those determined herein could therefore be assistive to sharpen specificity when applying sinus rhythm mapping to localize EP catheter ablation sites.

Signature signal strategy: Electrogram-based ventricular tachycardia mapping

Multiple decades of work have recognized complexities of substrates responsible for ventricular tachycardia (VT). There is sufficient evidence that 3 critical components of a re-entrant VT circuit, namely, region of slow conduction, zone of unidirectional block, and exit site, are located in spatial vicinity to each other in the ventricular scar. Each of these components expresses characteristic electrograms in sinus rhythm, at initiation of VT, and during VT, respectively. Despite this, abnormal electrograms are widely targeted without appreciation of these signature electrograms during contemporary VT ablation. Our aim is to stimulate physiology-based VT mapping and a targeted ablation of VT. In this article, we focus on these 3 underappreciated aspects of the physiology of ischemic scar-related VT circuits that have practical applications during a VT ablation procedure. We explore the anatomic and functional elements underlying these distinctive bipolar electrograms, specifically the contribution of tissue branching, conduction restitution, and wave curvature to the substrate, as they pertain to initiation and maintenance of VT. We propose a VT ablation approach based on these 3 electrogram features that can be a potential practical means to recognize critical elements of a VT circuit and target ablation.

Septal Coronary Venous Mapping to Guide Substrate Characterization andAblation of Intramural Septal Ventricular Arrhythmia.

This study describes the use of septal coronary venous mapping to facilitate substrate characterization and ablation of intramural septal ventricular arrhythmia (VA). Intramural septal VA represents a challenge for substrate definition and catheter ablation. Between 2015 and 2018, 12 patients with structural heart disease, recurrent VA, and suspected intramural septal substrate underwent a septal coronary venous procedure in which mapping was performed by advancement of a wire into the septal perforator branches of the anterior interventricular vein. A total of 5 patients with idiopathic VA were also included as control subjects to compare substrate characteristics. Patients were 63 ± 14 years of age, and 11 (92%) were men. Most patients with structural heart disease had nonischemic cardiomyopathy (83%). Six patients underwent ablation for premature ventricular contractions (PVC) and 6 for ventricular tachycardia. All patients had larger septal unipolar voltage abnormalities than bipolar voltage abnormalities (mean area 35.3 ± 16.8cm2 vs. 10.7 ± 8.4cm2, respectively; p= 0.01), Patients with idiopathic VA had normal voltage. Septal coronary venous mapping revealed low-voltage, fractionated, and multicomponent electrograms in sinus rhythm in all patients with substrate compared to that in patients with idiopathic VA (amplitude 0.9 ± 0.9mV vs. 4.4 ± 3.7mV, respectively; p= 0.007; and duration 147 ± 48ms vs. 92 ± 10ms, respectively; p= 0.03). Ablation targeted early activation, pace map match, and/or good entrainment sites from intraseptal recording. Over a mean follow-up of 339 ± 240days, the PVC and insertable cardioverter-defibrillator therapies burden were significantly reduced (from a mean of 22 ± 11% to 4 ± 8%; p= 0.005; and a mean 5 ± 2 to 1 ± 1; p= 0.001, respectively). Most patients (80%) with idiopathic VA remained arrhythmia free. In patients with suspected intramural septal VA, mapping of the septal coronary veins may be helpfulto characterize the arrhythmia substrate, identify ablation targets, and guide endocardial ablation.

Information theory to tachycardia therapy: electrogram entropy predicts diastolic microstructure of reentrant ventricular tachycardia.

There is no known strategy to differentiate which multicomponent electrograms in sinus rhythm maintain reentrant ventricular tachycardia (VT). Low entropy in the voltage breakdown of a multicomponent electrogram can localize conditions suitable for reentry but has not been validated against the classic VT activation mapping. We examined whether low entropy in a late and diversely activated ventricular scar region characterizes and differentiates the diastolic path of VT and represents protected tissue channels devoid of side branches. Intraoperative bipolar electrogram (BiEGM) activation and entropy maps were obtained during sinus rhythm in 17 patients with ischemic cardiomyopathy and compared with diastolic activation paths of VT (total of 39 VTs). Mathematical modeling of a zigzag main channel with side branches was also used to further validate structural representation of low entropy in the ventricular scar. A median of one region per patient (range: 1-2 regions) was identified in sinus rhythm, in which BiEGM with the latest mean activation time and adjacent minimum entropy were assembled together in a high-activation dispersion region. These regions accurately recognized diastolic paths of 34 VTs, often to multiple inducible VTs within a single individual arrhythmogenic region. In mathematical modeling, side branching from the main channel had a strong influence on the BiEGM composition along the main channel. The BiEGM obtained from a long unbranched channel had the lowest entropy compared with those with multiple side branches. In conclusion, among a population of multicomponent sinus electrograms, those that demonstrate low entropy and are delayed colocalize to critical long-protected channels of VT. This information is pertinent for planning VT ablation in sinus rhythm. NEW & NOTEWORTHY Entropy is a measure to quantify breakdown in information. Electrograms from a protected tissue channel can only possess a few states in their voltage and thus less information. In contrast, current-load interactions from side branches in unprotected channels introduce a number of dissimilar voltage deflections and thus high information. We compare here a mapping approach based on entropy against a rigorous reference standard of activation mapping during VT and entropy was assessed in sinus rhythm.

348 A feasibility pilot study to identify select pulmonary vein antral sinus rhythm electrograms as targets for catheter ablation in patients with atrial fibrillation using 3D electroanatomical mapping

348 A feasibility pilot study to identify select pulmonary vein antral sinus rhythm electrograms as targets for catheter ablation in patients with atrial fibrillation using 3D electroanatomical mapping

Spectral characteristics of atrial electrograms in sinus rhythm correlates with sites of ganglionated plexuses in patients with paroxysmal atrial fibrillation

To verify whether spectral components of atrial electrograms (AE) during sinus rhythm (SR) correlate with cardiac ganglionated plexus (GP) sites. Thirteen patients undergoing atrial fibrillation (AF) ablation were prospectively enrolled. Prior to radio frequency application, endocardial AE were recorded with a sequential point-by-point approach. Electrical stimuli were delivered at 20 Hz, amplitude 100 V, and pulse width of 4 ms. A vagal response was defined as a high-frequency stimulation (HFS) evoked atrioventricular block or a prolongation of RR interval. Spectral analysis was performed on single AE during SR, sampling rate of 1000 Hz, Hanning window. Overall, 1488 SR electrograms were analysed from 186 different left atrium sites, 129 of them corresponding to negative vagal response sites, and 57 to positive response sites. The electrogram duration and the number of deflections were similar in positive and negative response sites. Spectral power density of sites with vagal response was lower between 26 and 83 Hz and higher between 107 and 200 Hz compared with negative response sites. The area between 120 and 170 Hz normalized to the total spectrum area was tested as a diagnostic parameter. Receiver operating characteristic curve analysis demonstrated that an area 120-170/area(total) value >0.14 identified vagal sites with 70.9% sensitivity and 72.1% specificity. Spectral analysis of AE during SR in sites that correspond to the anatomical location of the GP is feasible and may be a simpler method of mapping the cardiac autonomic nervous system, compared with the HFS technique.

Time‐ and Frequency‐Domain Characteristics of Atrial Electrograms During Sinus Rhythm and Atrial Fibrillation

Complex fractionated atrial electrograms (CFAE) have been considered to be helpful during catheter ablation of atrial fibrillation (AF). The purpose of this study was to analyze the characteristics of CFAEs recorded during sinus rhythm (SR) and AF, and to determine their relationship to perpetuation of AF and clinical outcome. Antral pulmonary vein isolation (APVI) was performed in 34 consecutive patients (age = 59 ± 10 years) with paroxysmal AF who presented in SR. Time- and frequency-domain characteristics of electrograms recorded from the same sites in the coronary sinus (CS) were analyzed during SR and AF, before and during isoproterenol infusion. There was a modest correlation in fractionation index (FI: change in the direction of depolarization, r = 0.40, P = 0.001) and complexity index (CI: change in the polarity of depolarization, r = 0.41, P = 0.001), but not in the dominant frequency (DF) between SR and AF. There was no relationship between the DF and CI or FI during AF. Isoproterenol was associated with an increase in DF during AF (6.6 ± 0.9 vs 5.1 ± 0.6 Hz, P < 0.001) but had no effect on CI or FI (P = 0.6). A higher CI (58.3 ± 21.0/s vs 38.0 ± 21.0/s, P < 0.01), and FI (123.5 ± 44.8/s vs 75.6 ± 44.6/s, P < 0.01) during AF were associated with a lower likelihood of termination of AF during APVI and a higher probability of recurrent AF after ablation. Ratio of FI during AF to SR was also higher when AF persisted than terminated after APVI (29.7 ± 12.4 vs 19.1 ± 9.7, P = 0.002). However, time- or frequency-domain parameters during SR were not predictive of termination or clinical outcome. Structural and functional properties of the atrial myocardium during AF contribute to electrogram complexity, which may indicate the presence of extra-PV mechanisms of AF that are not eliminated by APVI. Mapping of complex electrograms in SR is not likely to be sufficient to identify drivers of AF.

Foreword

This study sought to characterize left atrial (LA) sinus rhythm electrogram (EGM) patterns and their relationship to parasympathetic responses during atrial fibrillation (AF) ablation.The mechanistic basis of fractionated LA EGMs in patients with paroxysmal AF is not well understood.We analyzed 1,662 LA ablation sites from 30 patients who underwent catheter ablation for paroxysmal AF. Pre-ablation EGM characteristics (number of deflections, amplitude, and duration) were measured in sinus rhythm. Parasympathetic responses during radiofrequency application (increase of atrial-His interval by ≥10 ms or decrease of sinus rate by ≥20%) were assessed at all sites. We also prospectively studied the effect of adenosine, a pharmacological agent mimicking acetylcholine signaling in myocytes, on LA EGMs. Finally, we performed mathematical simulations of atrial tissue to delineate possible mechanisms of fractionated EGMs in sinus rhythm.A specific pattern of pre-ablation sinus rhythm EGM (deflections ≥4, amplitude ≥0.7 mV, and duration ≥40 ms) was strongly associated with parasympathetic responses (sensitivity 72%, specificity 91%). The sites associated with these responses were found to be located mainly in the posterior wall of the LA. Adenosine administration and mathematical simulation of the effect of acetylcholine were able to reproduce a similar EGM pattern.Parasympathetic activation during AF ablation is associated with the presence of pre-ablation high-amplitude fractionated EGMs in sinus rhythm. Local acetylcholine release could potentially explain this phenomenon.

Functional Characterization of Atrial Electrograms in Sinus Rhythm Delineates Sites of Parasympathetic Innervation in Patients With Paroxysmal Atrial Fibrillation

This study sought to characterize left atrial (LA) sinus rhythm electrogram (EGM) patterns and their relationship to parasympathetic responses during atrial fibrillation (AF) ablation. The mechanistic basis of fractionated LA EGMs in patients with paroxysmal AF is not well understood. We analyzed 1,662 LA ablation sites from 30 patients who underwent catheter ablation for paroxysmal AF. Pre-ablation EGM characteristics (number of deflections, amplitude, and duration) were measured in sinus rhythm. Parasympathetic responses during radiofrequency application (increase of atrial-His interval by > or =10 ms or decrease of sinus rate by > or =20%) were assessed at all sites. We also prospectively studied the effect of adenosine, a pharmacological agent mimicking acetylcholine signaling in myocytes, on LA EGMs. Finally, we performed mathematical simulations of atrial tissue to delineate possible mechanisms of fractionated EGMs in sinus rhythm. A specific pattern of pre-ablation sinus rhythm EGM (deflections > or =4, amplitude > or =0.7 mV, and duration > or =40 ms) was strongly associated with parasympathetic responses (sensitivity 72%, specificity 91%). The sites associated with these responses were found to be located mainly in the posterior wall of the LA. Adenosine administration and mathematical simulation of the effect of acetylcholine were able to reproduce a similar EGM pattern. Parasympathetic activation during AF ablation is associated with the presence of pre-ablation high-amplitude fractionated EGMs in sinus rhythm. Local acetylcholine release could potentially explain this phenomenon.

Injury potential as a diagnostic tool for implantable cardioverter-defibrillator lead perforation

An implantable cardioverter-defibrillator (ICD) was placed in 64-year-old man with hypertrophic cardiomyopathy who had nducible ventricular arrhythmias during electrophysiology study. t routine 6-week follow-up, the patient had fatigue but no comlaints of chest pain. Clinical examination was unremarkable. entricular lead functions were normal (impedance 728 , hreshold 0.5 V at 0.3 ms and R-wave sensed at 5.5 mV). Howver, the sinus rhythm electrogram (EGM), recorded between the ead tip to adjacent ring electrode, showed an injury current (Figre 1B) compared with day 1 postimplant (Figure 1A). This nding raised the suspicion of lead perforation. Two-dimensional chocardiography showed trivial pericardial effusion with the pos-

AB36-3: Iso-duration mapping during ventricular pacing as a tool to ablate unmappable ventricular tachycardia after remote myocardial infarction

VT after MI is usually due to reentry through a protected isthmus bounded by functional lines of block (LoB). When VT is not inducible or not tolerated (unmappable VT) there is a need to unmask the isthmus by sinus mapping or pacing maneuvers. Experimental data suggest that sinus rhythm electrograms (EGM) along the central common pathway have a short duration compared to longer EGMs along LoBs. Using Carto® we aimed at identifying these isthmus-related LoBs by mapping the EGM duration during RV pacing.

Analysis of implantable cardioverter defibrillator signals for non conventional cardiac electrical activity characterization

Implantable cardioverter defibrillators (ICDs) can store intracardiac electrograms (EGMs) in sinus rhythm (SR), at the onset of spontaneous ventricular tachyarrhythmias (VT) or during their course. This allows the investigation of unknown features of the heart electrical activity associated with different cardiac rhythms. In this study we propose a non conventional cardiac electrical activity characterization (CEAC) that extracts quantitative information about the power spectrum wideness and variability of the beat-by-beat morphology. We analyze 293 EGMs from 40 patients who underwent implantation of St Jude Medical-Ventritex ICDs that allow the storage of EGMs with two different modes of recording: bipolar (BIP) and unipolar or far-field (FF). The EGMs are studied with this CEAC by (1) exploring differences between the CEAC measured from FF and BIP EGMs during similar cardiac rhythms, and (2) investigating the mode of recording that allows a better separation between SR and VT rhythms. Results show that, with similar cardiac rhythm, the CEACs from FF or BIP recordings are different (for SR rhythm: sensitivity 81.5%, specificity 93.6%; for VT rhythm: sensitivity and specificity 100%); thus FF and BIP EGMs analyze different aspects of cardiac activity. The CEAC applied to FF EGMs distinguishes better EGMs obtained during SR from VT rhythms (VT vs SR with sensitivity 92.7% and specificity 79.7%) than when it is applied to BIP signals (VT vs SR with sensitivity 60% and specificity 73.3%).

Method to predict isthmus location in ventricular tachycardia caused by reentry with a double-loop pattern

Method to Predict Isthmus Location. Background: During electrophysiologic study, induction and mapping of clinical reentrant ventricular tachycardia can be difficult. Hence, analysis of sinus-rhythm electrograms for reentry localization is of potential clinical relevance. Herein is described a method of sinus-rhythm electrogram shape analysis, that does not require arbitrary threshold values, for localization of double-loop reentrant circuits that drive clinical tachycardias. Methods and Results: Reentrant ventricular tachycardia was induced by premature stimulation in 23 postinfarction canine hearts 4-5 days after left anterior descending (LAD) ligation. Sinus-rhythm activation maps were constructed from bipolar electrograms acquired at 196-312 sites in the epicardial border zone. The timing of all electrogram peak deflections during one cycle of sinus rhythm was determined, and the mean (MPD) and deviation (DPD) were taken, respectively, as estimates of the time of activation wavefront crossing, and the duration of local electrical activity. These variables were then mapped on a computerized grid. The line of most uniform and sharp MPD gradient predicted the propagation direction through the double-loop reentrant circuit isthmus that would occur upon tachycardia induction. The sharpest transitions in DPD bounding this line predicted the positions of arcs of block that would border the reentrant circuit isthmus during tachycardia. The actual and estimated isthmuses overlapped by a mean of 84.1 ′ 3.8%. In six experiments lacking inducible reentrant tachycardia, no line of sharp MPD gradient was present in the MPD maps. Conclusions: Analysis of multiple sinus-rhythm deflections can localize the reentrant ventricular tachycardia isthmus without introduction of arbitrary threshold points and peak choices that may lead to error.

Localization of the critical isthmus of post-infarct re-entrant ventricular tachycardia using sinus rhythm electrogram characteristics

We sought to assess the performance of sinus rhythm (SR) electrogram (EGM) characteristics to unmask critical ventricular tachycardia (VT) isthmuses (CRIS) in patients with post-infarct re-entrant VT.

Ventricular Tachycardia Duration and Form Are Associated with Electrical Discontinuities Bounding the Core of the Reentrant Circuit

Successful prediction of reentrant ventricular tachycardia duration and form from sinus-rhythm electrogram signals in canine hearts is relevant to clinical studies, to potentially improve catheter ablation treatment during EP study. Following LAD ligation of canine hearts, activation maps were constructed from 312 border zone sites 4-5 days postinfarction. When reentrant ventricular tachycardia was inducible via programmed stimulation, the core of the circuit was defined on the maps as the enclosed area formed by the adjoining lines of slowest conduction and block bounding the protected region of the reentrant circuit. The number, location, and width of points of entrance or exit of the activation wavefront about the core were determined. Core perimeter location was then marked on the sinus-rhythm activation map, and the difference in activation time at opposite recording sites along the core perimeter was measured. Mean sinus-rhythm activation was highly discontinuous along the core perimeter in 10 transient reentry experiments (30.1 +/- 4.4 ms), moderately discontinuous in 13 sustained experiments (16.7 +/- 1.8 ms), and only slightly discontinuous in 5 noninducible experiments (9.7 +/- 1.7 ms). For transient versus sustained experiments, the entrance/exit points were narrower (mean: 6.5 +/- 1.0 mm vs 9.5 +/- 1.8 mm) with larger sinus-rhythm discontinuity across them (mean: 23.8 +/- 6.0 ms vs 11.8 +/- 2.1 ms). As core size increased, so did the number of entrance/exits present during reentry (P < 0.001). With increasing core size, four-loop (quatrefoil) reentry was frequently observed. Whether reentrant ventricular tachycardia will be inducible in the canine infarct border zone, and its duration and form, is associated with the characteristics of electrical discontinuities present about the core perimeter.