Low Bipolar Voltage Research Articles

Find Me If You Can: First Clinical Experience Using the Novel CARTOFINDER Algorithm in a Routine Workflow for Atrial Fibrillation Ablation.

Aims: The CARTOFINDER module allows for simultaneous and automated detection of repetitive focal and rotational activations in patients with atrial arrhythmias. This study aimed to validate the CARTOFINDER algorithm for the detection of potential drivers for atrial fibrillation (AF) and to access their potential impact on individual arrhythmia substrates. Methods: Fifty consecutive patients underwent AF ablation for persistent AF (PERS), using a 3D-mapping system with the integrated CARTOFINDER module. Regions of interest (ROIs) were identified before and after ablation, and their spatial and temporal relationship was correlated with areas of fibrosis. Results: Procedural success was achieved in all patients and 42% received ablation beyond pulmonary vein isolation (PVI). AF termination was observed in 6 patients (12%). The mean procedure duration was 134 ± 29 min. ROIs were revealed in all patients (mean n = 77 ± 52) and there was no statistical evidence for a predilection site. There was no significant anatomical correlation between ROIs and bipolar low voltage. Remapping confirmed the elimination of ROIs in relation to the individual ablation site, a limited reproducibility of rotational ROIs and persistent focal activity over time in some anatomical segments. ROIs were not a predictor for AF recurrence during following ablation. Conclusions: CARTOFINDER mapping can be integrated into a routine workflow for AF ablation. ROIs could be discriminated in all patients and an ablation effect was observed in some patients, whereas persistent activity was found in certain anatomical segments, even after ablation. ROIs might be an additional ablation target when we are able to understand the individual substrate.

Relations between voltage mapping and diagnosis and genetics in patients with arrhythmogenic right ventricular cardiomyopathy

Relations between voltage mapping and diagnosis or genetic background in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) have not been investigated so far. We investigate if diagnosis or genetic background were linked to voltage mapping in ARVC. Seventy patients with proved or suspected ARVC undergoing 3D endocardial voltage mapping and genetic testing have been retrospectively included. Localisation and extension of bipolar low voltage areas were correlated to ARVC diagnosis and presence of a culprit mutation. Forty-four over seventy fulfilled ARVC Task Force criteria and 25/70 had culprit mutations. Endocardial (38/44 vs. 16/26, P = 0.02) and especially infero-lateral scars (31/44 vs. 9/26, P = 0.003) were more often present in patients fulfilling Task force criteria vs. suspected ARVC, with larger scars (area 23 ± 27 vs. 8 ± 11 cm2, P = 0.04, perimeter 17 ± 10 vs. 11 ± 7 cm, P = 0.03) (sensitivity 86%). Mutated patients had more infero-lateral (19/25 vs. 21/45, P = 0.01), multiple (12/20 vs. 11/34, P = 0.04) and larger scars (perimeter 21 ± 10 vs. 12 ± 7 cm, P = 0.01) vs. non-mutated patients. In patients with ARVC diagnosed according to the Task Force criteria, there was a trend toward more infero-lateral (P = 0.09) and larger scars (P = 0.08) in mutated cases. PKP2-mutated cases tended to have less ourflow tract (P = 0.08) and less multiple scars (P = 0.09) vs. other mutations (Fig. 1). 3D endocardial mapping could have an important role for ARVC diagnosis and may be able to detect minor forms with otherwise insufficient criteria for diagnosis. More frequent and larger infero-lateral scars are present in mutated patients with borderline differences according to the mutated genes.

Relations between voltage mapping and diagnosis and genetics in patients with arrhythmogenic right ventricular cardiomyopathy

Abstract Introduction Relations between voltage mapping and diagnosis or genetic background in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) have not been investigated so far. Objective We investigate if diagnosis or genetic background were linked to voltage mapping in ARVC. Method 70 patients with proved or suspected ARVC undergoing 3D endocardial mapping and genetic testing have been retrospectively included. Localisation and extension of bipolar low voltage areas were correlated to ARVC diagnosis and presence of a culprit mutation. Results 44/70 fulfilled ARVC Task Force criteria and 25/70 had culprit mutations. Endocardial (38/44 vs 16/26, p=0.02) and especially infero-lateral scars (31/44 vs 9/26, p=0.003) were more often present in patients fulfilling Task force criteria vs suspected ARVC, with larger scars (area 23±27 vs 8±11 cm2, p=0.04, perimeter 17±10 vs 11±7 cm, p=0.03) (sensitivity 86%). Mutated patients had more infero-lateral (19/25 vs 21/45, p=0.01), multiple (12/20 vs 11/34, p=0.04) and larger scars (perimeter 21±10 vs 12±7 cm, p=0.01) vs non mutated patients. In patients with ARVC diagnosed according to the Task Force criteria, there was a trend toward more infero-lateral (p=0.09) and larger scars (p=0.08) in mutated cases. PKP2-mutated cases tended to have less ourflow tract (p=0.08) and less multiple scars (p=0.09) vs other mutations. Conclusion 3D endocardial mapping could have an important role for ARVC diagnosis and may be able to detect minor forms with otherwise insufficiant criteria for diagnosis. More frequent and larger infero-lateral scars are present in mutated patients with bordeline differences according to the mutated genes. Funding Acknowledgement Type of funding source: None

High-density mapping of de novo focal atrial tachycardias using a new software: Protected low-voltage areas by zones of conduction delay.

BackgroundThe pathophysiological mechanism of focal atrial tachycardias (AT) remains obscure.MethodsFifteen patients (6 males, age 45 ± 18) with focal AT underwent high‐density activation mapping using a new software called extended early‐meets‐late (EEML).ResultsIrrespective of the arrhythmia mechanism, low bipolar voltage fractionated signals (0.14 ± 0.10 mV) were seen at the earliest activation site. The mean low‐voltage area (LVA) at the earliest activation site was 3.2 ± 1.0 cm2. EEML mapping revealed zones of conduction delay at the borders of LVAs.ConclusionsLVAs protected by zones of slow conduction appears to play an important role in the initiation and maintenance of focal ATs.

P383Epicardial voltage fingerprinting of sinus rhythm in patients with mitral valve disease

Abstract Funding Acknowledgements CVON-AFFIP [grant number 914728], NWO-Vidi [grant number 91717339], Biosense Webster USA [ICD 783454] and Medical Delta Background Voltage mapping is increasingly used for identifying the substrate of cardiac arrhythmias like atrial fibrillation (AF). Low bipolar voltage areas are regarded as indicators of structurally remodeled tissue. However, non-substrate related factors such as wavefront activation direction also influence voltages of bipolar EGMs. Unipolar electrograms (U-EGMs), on the other hand, are independent of the electrode orientation and atrial wavefront direction. It is for these reasons that U-EGMs are increasingly used in electrophysiological studies and newly developed mapping systems guiding ablation procedures. Objective The goal of this study is to examine U-EGM voltages at a high resolution scales during sinus rhythm (SR) in patients with mitral valve disease (MVD). Methods Intra-operative epicardial mapping (interelectrode distance 2mm) of the right and left atrium (RA, LA), Bachmann’s Bundle (BB) and pulmonary vein area (PVA) was performed during SR in 67 patients (27 male, 67 ± 11 years) with or without a history of paroxysmal atrial fibrillation (PAF). U-EGMs were analyzed according to their potential type and peak-to-peak voltage. Low voltage was defined as the proportion of potentials with an amplitude below 1.0 mV. Results In all patients, there was a considerable variation in voltage distribution between all atrial regions and clear inter-individual differences were found. In patients without AF, there were no statistical differences in median potential voltages between the various atrial regions (P = 0.869). In the PAF group, however, unipolar voltages of BB potentials were lower compared to RA potentials (3.30 [2.25–4.57] mV vs. 4.64 [3.85–6.08] mV, P = 0.006) and LA potentials (3.30 [2.25–4.57] mV vs. 4.86 [3.72–5.86] mV, P = 0.009). In addition, unipolar voltages at BB were lower in the patients with PAF compared to those without AF (no AF: 4.94 [3.56–5.98] mV, PAF: 3.30 [2.25–4.57] mV, P = 0.006). A larger number of low voltage potentials were recorded at BB in the PAF group (no AF: 2.13 [0.52–7.68] %, PAF: 12.86 [3.18–23.59] %, P = 0.001). In addition, a higher number of fractionated potentials was found in patients with PAF at the PVA (12.81 [9.19–18.03] % vs. 20.94 [13.54–27.37] %, P < 0.001) and LA (11.47 [7.30–18.30] % vs. 17.80 [12.93–21.34] %, P = 0.045). Lower voltages were found in potentials with a progressively higher degree of fractionation (R=-0.76, P < 0.001). Conclusions Even in SR, patients with MVD and AF episodes are characterized by decreased potential voltages at BB and a higher degree of low voltage potentials. Both considerable intra- and inter-individual variation in potential voltages were found in our study population, which underlines the interest of an individualized electrical signal profile which can be used to characterize complex conduction disorders. Abstract Figure. Epicardial voltage maps

Electroanatomical Voltage Mapping to Distinguish Right-Sided Cardiac Sarcoidosis From Arrhythmogenic Right Ventricular Cardiomyopathy.

This study sought to investigate the value of electroanatomical voltage mapping (EAVM) to distinguish cardiac sarcoidosis (CS) from arrhythmogenic right ventricular cardiomyopathy (ARVC) in patients with ventricular tachycardia from the right ventricle (RV). CS can mimic ARVC. Because scar in ARVC is predominantly subepicardial, this study hypothesized that therelative sizes of endocardial low bipolar voltage (BV) to low unipolar voltage (UV) areas may distinguish CS from ARVC. Patients with CS affecting the RV (n=14), patients with gene-positive ARVC (n=13), and a reference group of patients without structural heart disease (n=9) who underwent RV endocardial EAVM were included. RV region-specific BV and UV cutoffs were derived from control subjects. In CS and ARVC, segmental involvement was determined and low-voltage areas were measured, using<1.5mV for BV and<3.9mV,<4.4mV, and<5.5mV for UV. The ratio between low BV and low UV area was calculated generating 3 parameters: Ratio3.9, Ratio4.4 and Ratio5.5, respectively. In control subjects, BV and UV varied significantly among RV regions. The basal septum was involved in 71% of CS patients and in none of ARVC patients. Ratio5.5 discriminated CS from ARVC the best. An algorithm including Ratio5.5≥0.45 and basal septal involvement identified CS with 93% sensitivity and 85% specificity. This was validated in a separate population (CS [n=6], ARVC [n=10]) with 100% sensitivity and 100% specificity. EAVM provides detailed information about scar characteristics and scar distribution in the RV. Analgorithm combining Ratio5.5 (area BV<1.5mV/area UV<5.5mV) and bipolar basal septal involvement allows accurate diagnosis of (isolated) CS in patients presenting with monomorphic ventricular tachycardia from the RV.

Association of Left Atrial High-Resolution Late Gadolinium Enhancement on Cardiac Magnetic Resonance With Electrogram Abnormalities Beyond Voltage in Patients With Atrial Fibrillation.

Conflicting data have been reported on the association of left atrial (LA) late gadolinium enhancement (LGE) with atrial voltage in patients with atrial fibrillation. The association of LGE with electrogram fractionation and delay remains to be examined. We sought to examine the association between LA LGE on cardiac magnetic resonance and electrogram abnormalities in patients with atrial fibrillation. High-resolution LGE cardiac magnetic resonance was performed before electrogram mapping and ablation in atrial fibrillation patients. Cardiac magnetic resonance features were quantified using LA myocardial signal intensity Z score (SI-Z), a continuous normalized variable, as well as a dichotomous LGE variable based on previously validated methodology. Electrogram mapping was performed pre-ablation during sinus rhythm or LA pacing, and electrogram locations were coregistered with cardiac magnetic resonance images. Analyses were performed using multilevel patient-clustered mixed-effects regression models. In the 40 patients with atrial fibrillation (age, 63.2±9.2 years; 1312.3±767.3 electrogram points per patient), lower bipolar voltage was associated with higher SI-Z in patients who had undergone previous ablation (coefficient, -0.049; P<0.001) but not in ablation-naive patients (coefficient, -0.004; P=0.7). LA electrogram activation delay was associated with SI-Z in patients with previous ablation (SI-Z: coefficient, 0.004; P<0.001 and LGE: coefficient, 0.04; P<0.001) but not in ablation-naive patients. In contrast, increased LA electrogram fractionation was associated with SI-Z (coefficient, 0.012; P=0.03) and LGE (coefficient, 0.035; P<0.001) only in ablation-naive patients. The association of LA LGE with voltage is modified by ablation. Importantly, in ablation-naive patients, atrial LGE is associated with electrogram fractionation even in the absence of voltage abnormalities.

P5651Association of left atrial fibrosis extent with left ventricular geometric remodeling and diastolic dysfunction in patients with paroxysmal atrial fibrillation

Abstract Introduction Whether left atrial fibrosis (LAf) in patients with atrial fibrillation (AF) is a consequence of left ventricular (LV) diastolic dysfunction or primary atrial pathology continues to be a debatable issue. Electroanatomical mapping (EAM) allows to image and to define LAf as a substrate of AF. Purpose To study the relationship of LAf extent with LV diastolic function and geometric remodeling in patients (pts) with paroxysmal AF. Methods 56 pts with paroxysmal AF (mean age 57.1±8.4 years, 31 males), undergone catheter ablation, were enrolled in the study, including 30 pts with arterial hypertension (AH), 15 – with coronary artery disease (CAD) and AH. Comprehensive transthoracic echocardiography was carried out in all pts to assess chamber volumes, systolic and LV diastolic functions and geometry patterns according to Recommendations of ASE and EACVI. Before ablation, EAM was performed in sinus rhythm. The bipolar low voltage areas of LAf were identified with the cut-off &lt;0.5 mV. For the LAf quantification following indicators were calculated: total square of LAf (Sf, cm2) and LAf degree, estimated as an analog of the UTAH staging system, by selection of UTAH I: &lt;5% fibrosis; II: 5–19%; III: 20–35% and IV: &gt;35%. Results All patients had preserved systolic LV function. To assess the influence of LV geometry on LAf extent all pts were distributed in accordance to LV geometry patterns (p): normal geometry (pI) – 27 pts, concentric remodeling (pII) – 13, eccentric hypertrophy (pIII) – 10, concentric hypertrophy (pIV) – 6. Pts with pIII were older than pI pts: 60.8±6.4 vs 53.9±10.4 (p=0.048). All pts with pIII and pIV had AH. From 11 pts without AH, 10 had pI of LV geometry. PIII was revealed more often in CAD pts compared to those without CAD: 29.2 vs 10.5% (p=0.04). PIII pts had bigger LA volume compared to pI pts (74.3±22.5 vs 58.8±19.4 ml, p=0.019) and pII pts (61.9±14.9, p=0.05), but LA volume of pIII pts didn't differ from pIV pts (71.9±14.5, p=0.78). PIII pts had more extent Sf than pI pts (28.32±8.9 vs 13.4±6.5, p=0.05), while Sf of pII (17.3±8.7, p=0.495) and pIV pts (16.4±9.5, p=0.699) didn't differ significantly from Sf of pI pts. As for the degree of LAf, UTAH I was absent in pts with pIII and UTAH IV was revealed in 40% of these pts, while in pts with pI UTAH I was in 26% and UTAH IV - in 14.8% (p=0.049). However, Sf and UTAH degree did not depend on age, CAD and heart failure presence. As for diastolic dysfunction, in pIII and pIV pts e∼septal and e∼lateral were lower compared to pI pts: 6.3±1.9, 5.5±2.4 vs 8.5±2.2 (p&lt;0.01) and 8.2±2.7, 8.0±3.8 vs 11.3±2.9 (p&lt;0.01), respectively, while E/e∼ in pIII pts didn't differ from pI pts (8.0±1.6 vs 7.2±1.6, p=0.17), but in pIV was more than in pI pts (10.4±2.8, p=0.003). Conclusion LAf extent in paroxysmal AF is associated more with such LV geometry pattern as eccentric hypertrophy, than with diastolic disorders, which accompany both eccentric and concentric hypertrophy.

Right ventricular outflow tract low-voltage areas identify the site of origin of idiopathic ventricular arrhythmias: A high-density mapping study.

Electronatomical mapping allows direct and accurate visualization of myocardial abnormalities. This study investigated whether high-density endocardial bipolar voltage mapping of the right ventricular outflow tract (RVOT) during sinus rhythm may guide catheter ablation of idiopathic ventricular arrhythmias (VAs). Forty-four patients (18 males, mean age: 38.1 ± 13.8 years) with idiopathic RVOT VAs and negative cardiac magnetic resonance imaging underwent a stepwise mapping approach for the identification of the site of origin (SOO). High-density electronatomical mapping (1096.6 ± 322.3 points) was performed during sinus rhythm and identified at least two low bipolar voltage areas less than 1 mV (mean amplitude of 0.20 ± 0.10 mV) in 39 of 44 patients. The mean low-voltage surface area was 1.4 ± 0.8 cm2 . Group 1 consisted of 28 patients exhibiting low-voltage areas and high-arrhythmia burden during the procedure. Pace match to the clinical VAs was produced in one of these low-voltage areas. Activation mapping established the SOO at these sites in 27 of 28 cases. Group 2 comprised 11 patients exhibiting abnormal electroanatomical mapping, but very low-arrhythmia burden during the procedure. Pace mapping produced a near-perfect or perfect match to the clinical VAs in one of these areas in 9 of 11 patients which was marked as potential SOO and targeted for ablation. During the follow-up period, 25 of 28 patients from group 1 (89%) and 7 of 9 patients from group 2 (78%) were free from VAs. Small but detectable very low-voltage areas during mapping in sinus rhythm characterize the arrhythmogenic substrate of idiopathic RVOT VAs and may guide successful catheter ablation.

Left atrial imaging and registration of fibrosis with conduction voltages using LGE-MRI and electroanatomical mapping

Background and purposeAbnormal electrical conduction and excitability associated with fibrosis in the left atrium (LA) may serve as a substrate for atrial fibrillation (AF). Electroanatomical voltage mapping systems (EAMs) have become a dominant facilitator to treat AF with catheter ablation assisted by additional diagnostic imaging modalities. Importantly, AF has been associated with structural changes to the extracellular matrix of the myocardium, including increased collagen deposition—a process known as fibrosis. Late gadolinium enhancement-magnetic resonance imaging (LGE-MRI) may aid in guiding AF cardiac ablation therapy by determination of location of fibrosis in the LA. To locate fibrosis for cardiac ablation, however, accurate registration between EAMs and LGE-MRI data is crucial. The purpose of this work was to develop a method for registering EAMs with late gadolinium enhancement-magnetic resonance (LGE-MR) images of fibrosis. MethodsTwenty patients with persistent AF, who underwent magnetic resonance imaging scanning and EAMs prior to first-time catheter ablation, participated in the study. In our registration pipeline, LGE-MR images were registered to the left atrial surface on EAMs using manual alignment followed by iterative closest point (ICP), and non-rigid ICP (NICP) algorithm. Results and conclusionsThe results demonstrate that NICP provided a substantial reduction in registration error when compared to the use of affine ICP alone. Regions of fibrosis on LGE-MR images identified using the signal threshold to reference mean threshold demonstrated the most regional overlap with low bipolar voltage points on EAMs. Successful co-registration of LGE-MR images to EAMs may assist electro-physiologists in selecting candidate targets for ablation and ultimately, reduce the rate of AF recurrence for patients.

Substrate mapping for scar-related ventricular tachycardia in patients with resynchronization therapy-the importance of the pacing mode.

Targets for substrate-based catheter ablation of scar-related ventricular tachycardia (VT) include sites with fractionated and late potentials (LPs). We hypothesized that in patients with cardiac resynchronization therapy (CRT), the pacing mode may influence the timing of abnormal electrograms (EGMs) relative to the surface QRS complex. We assessed bipolar EGM characteristics in left ventricular low bipolar voltage areas (< 1.5mV) from 10 patients with coronary disease and a CRT device undergoing catheter ablation for VT. EGMs at 81 sites were analyzed during three different pacing modes (biventricular (BiV), right ventricular (RV)-only, and left ventricular (LV)-only) pacing. Stimulus to end of local electrogram duration (Stim-to-eEGM) depended significantly on the stimulation site (BiV, LV, or RV, p = 0.032). Single-chamber pacing unmasked LPs, not present during BiV pacing, in three patients. In another three patients, a concomitant increase in stimulus to end of surface QRS duration caused by single-site pacing compensated for the increase in Stim-to-eEGM duration, thereby prohibiting LP unmasking. The sequence of ventricular activation, as determined by the pacing site in patients with CRT devices, has a major influence on the detection of late potentials during substrate-guided ablation. Further study is warranted to define the optimal approaches, including the rhythm, for substrate mapping, but our findings suggest that BiV pacing may be most likely to obscure detection of late potentials as compared to single-site pacing.

Feasibility and utility of intraoperative epicardial scar characterization during left ventricular assist device implantation.

Ventricular arrhythmias (VA) after left ventricular assist device (LVAD) placement are associated with increased morbidity and mortality. We sought to assess epicardial voltage characteristics at the time of LVAD implantation and investigate relationships between scar burden and postimplant VA. Consecutive patients underwent open chest epicardial electroanatomic mapping immediately before LVAD implantation. Areas of low voltage and sites with local abnormal potentials were identified. Patients were followed prospectively for postimplant VA and clinical outcomes. Between 2015 and 2017, 36 patients underwent high-density intraoperative epicardial voltage mapping; 15 had complete maps suitable for analysis. Mapping required a median of 11.8 (interquartile range [IQR], 8.5-12.7) minutes, with a median of 2650 (IQR, 2139-3191) points sampled per patient. Over a median follow-up of 311 (IQR, 168-469) postoperative days, four patients (27%) experienced sustained VA. Patients with postimplant VA were more likely to have had preimplant implantable cardioverter defibrillator shocks (100% vs 27%; P = 0.03), ventricular tachycardia storm (75% vs 9%; P = 0.03), and lower ejection fraction (13.5 vs 19.0%, P = 0.05). Patients with postimplant VA also had a significantly higher burden of epicardial low bipolar voltage points: 55.4% vs 24.9% of points were less than 0.5 mV (P = 0.01), and 88.9% vs 63.7% of points less than 1.5 mV (P = 0.004). Intraoperative high-density epicardial mapping during LVAD implantation is safe and efficient, facilitating characterization of a potentially arrhythmogenic substrate. An increased burden of the epicardial scar may be associated with a higher incidence of postimplant VA. The role of empiric intraoperative epicardial ablation to mitigate risk of postimplant VA requires further study.

Epicardial ventricular tachycardia in ischemic cardiomyopathy: Prevalence, electrophysiological characteristics, and long-term ablation outcomes.

The characteristics of the epicardial (EPI) substrate responsible for ventricular tachycardia (VT) in ischemic cardiomyopathy (ICM) are undefined, and data on the long-term outcomes of EPI catheter ablation limited. We evaluated the prevalence, electrophysiologic features, and outcomes of catheter ablation of EPI VT in ICM. From December 2010 to June 2013, a total of 13 of 93 (14%) patients with ICM underwent catheter ablation at our institution and had conclusive evidence of critical EPI substrate demonstrated to participatein VT with activation, entrainment and/or pace mapping during sinus rhythm (two other patients underwent EPI mapping but had no optimal ablation targets). The electrophysiologic substrate characteristics and activation/entrainment mapping data were compared with a reference group of ICM patients without evidence of critical EPI substrate (N = 44), defined as a complete procedural success (noninducibility of any VT at programmed stimulation) after endocardial (ENDO)-only ablation. Patients with failed EPI access (N = 2) or history of cardiac surgery (N = 92) were excluded from the study. All 13 patients had evidence of abnormal EPI substrate with fractionated/late/split electrograms and low-bipolar voltage areas. The critical VT ablation sites were all located within the EPI bipolar "dense" scar (<1.0 mV) opposite the ENDO bipolar scar in 77% of cases and extending beyond the ENDO bipolar scar (within the ENDO unipolar low-voltage area) in the remaining patients. Compared with the reference ENDO-only group, patients with EPI VT had a smaller ENDO bipolar scar area, 54.0 (37.1-84) vs 86.7 (55.6-112) cm2 ; P = 0.0159, with a similar extent of ENDO unipolar low voltage. No other substrate characteristics or location differed between the two groups. After 35.2 ± 24.2 months of follow-up, VT-free survival was 73% in patients with EPI VT compared with 66% in the ENDO-only group (log-rank P = 0.56). The presence of the critical EPI substrate responsible for VT can be demonstrated in at least 14% of patients with ICM. The majority of EPI critical ablation sites are distributed oppositethe ENDO bipolar scar area and catheter ablation is effective in achieving long-term arrhythmia control.

Unipolar Endocardial Voltage Mapping in the Right Ventricle: Optimal Cutoff Values Correcting for Computed Tomography-Derived Epicardial Fat Thickness and Their Clinical Value for Substrate Delineation.

Low endocardial unipolar voltage (UV) at sites with normal bipolar voltage (BV) may indicate epicardial scar. Currently applied UV cutoff values are based on studies that lacked epicardial fat information. This study aimed to define endocardial UV cutoff values using computed tomography-derived fat information and to analyze their clinical value for right ventricular substrate delineation. Thirty-three patients (50±14 years; 79% men) underwent combined endocardial-epicardial right ventricular electroanatomical mapping and ablation of right ventricular scar-related ventricular tachycardia with computed tomographic image integration, including computed tomography-derived fat thickness. Of 6889 endocardial-epicardial mapping point pairs, 547 (8%) pairs with distance <10 mm and fat thickness <1.0 mm were analyzed for voltage and abnormal (fragmented/late potential) electrogram characteristics. At sites with endocardial BV >1.50 mV, the optimal endocardial UV cutoff for identification of epicardial BV <1.50 mV was 3.9 mV (area under the curve, 0.75; sensitivity, 60%; specificity, 79%) and cutoff for identification of abnormal epicardial electrogram was 3.7 mV (area under the curve, 0.88; sensitivity, 100%; specificity, 67%). The majority of abnormal electrograms (130 of 151) were associated with transmural scar. Eighty-six percent of abnormal epicardial electrograms had corresponding endocardial sites with BV <1.50 mV, and the remaining could be identified by corresponding low endocardial UV <3.7 mV. For identification of epicardial right ventricular scar, an endocardial UV cutoff value of 3.9 mV is more accurate than previously reported cutoff values. Although the majority of epicardial abnormal electrograms are associated with transmural scar with low endocardial BV, the additional use of endocardial UV at normal BV sites improves the diagnostic accuracy resulting in identification of all epicardial abnormal electrograms at sites with <1.0 mm fat.

Myocardial voltage ratio in arrhythmogenic right ventricular dysplasia/cardiomyopathy.

This study aimed to analyze the influence of scar distribution between the endocardium and the epicardium in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). Electroanatomical mapping data were derived from our ARVD/C registry. Myocardial voltage distribution between the endocardium and the epicardium was analyzed in 28patients (18men, 49.9± 13.0years) with previous ventricular tachycardia (VT) ablation and complete right ventricular maps. During the follow-up period of 28± 22months after ablation, 18 of 28patients (64.3%) remained free from VT recurrence. In univariate analysis, five variables associated with VT recurrence, i. e., advanced age, right ventricular (RV) myocardial voltage ratio ≥0.58, inducibility of VT after ablation, and longer procedure and fluoroscopy time. In binary logistic regression analysis only RV myocardial voltage ratio ≥0.58 (hazard ratio 11.667, 95% confidence interval 1.487-91.543, p= 0.012) remained associated with an increased risk of VT recurrence. The myocardial voltage ratio (bipolar low voltage area/unipolar low voltage area) as apotential surrogate parameter for scar distribution between the endocardium and the epicardium is significantly associated with the outcome after VT ablation in ARVD/C.

12-Lead Electrocardiogram to Localize Region of Abnormal Electroanatomic Substrate in Arrhythmogenic RightVentricular Cardiomyopathy.

The purpose of this study was to evaluate the relationship between electrocardiogram (ECG) QRS fragmentation (fQRS) and right ventricular (RV) endocardial (ENDO) and epicardial (EPI) electroanatomic substrate abnormalities in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). fQRS is frequently observed in patients with ARVC and reflects delayed conduction due to RV fibrosis. A total of 30 consecutive patients met the task force criteria for ARVC (19 men, mean age 41.1 ± 14.3 years) presenting for ventricular tachycardia ablation with detailed RV ENDO and EPI electroanatomic maps were included. Of these, 25 patients had depolarization abnormalities (fragmentation during and/or immediately after the QRS complex [fQRS]) in≥2 contiguous ECG leads. Inferior (II, III, aVF) fQRS was identified in 23 patients, anterior (V1 to V3) in 15patients,and basal superior (I/aVR) in 11 patients. The surface area and anatomic distribution of ENDO and EPI bipolar low-voltage regions (ENDO≤1.5 mV,<0.5 mV "dense scar"/EPI≤1.0 mV) and degree of isolated late potential activity consistent with a marked substrate abnormality were compared to the location of region-specific fQRS. In fQRS patients, ENDO very low bipolar voltage area (27.4 ± 24.9 cm2 [median 19 cm2] vs. 5.8 ± 5.4 cm2 [median 5 cm2]; p= 0.02) and EPI late potential percentage (22.6 ± 9.6% [median 24%] vs. 6.8 ± 3.9% [median 8%]; p= 0.002) were significantly larger than in patients without fQRS. Overall, ENDO and EPI bipolar low voltage area andlate potential density increased as the number of fQRS ECG regions (0 to 3) increased. Inferior fQRS most frequently identified EPI inferior substrate (82% sensitivity, 100% specificity), anterior fQRS identified RV EPI mid-free wall substrate (55% sensitivity, 100% specificity), and basal superior fQRS identified ENDO (45.8% sensitivity, 100% specificity) and EPI (52% sensitivity, 100% specificity) RV outflow tract substrate abnormalities. The extent and distribution of RV voltage substrate abnormalities can be predicted by region-specific ECG depolarization changes in patients with ARVC and ventricular tachycardia.

Mitigation of voltage unbalance by using static load transfer switch in bipolar low voltage DC distribution system

In this paper, a method is proposed to mitigate voltage unbalance and to reduce power loss due to neutral current in a bipolar Low-Voltage DC (LVDC) distribution system by using a static load transfer switch (SLTS). Furthermore, an algorithm to determine the proper position of loads by using the SLTS is presented; this algorithm is developed by considering the neutral current at each load point. The underlying strategy of the SLTS method is that a local substation generates switching signals by using the proposed algorithm on the basis of data measured by a DC/DC converter; thereafter, SLTSs, which are placed in the DC/DC converter, are operated to reconfigure the structure of loads. To evaluate the performance of the proposed method, the conventional method for calculating the percent voltage unbalance for an AC system is modified and made applicable for a DC system. The modeling of a 1500V bipolar LVDC distribution system carried out using the ElectroMagnetic Transients Program (EMTP) is also presented herein. Finally, a simulation carried out by employing the SLTS method under various load conditions is presented; the results show a decrease in power loss and mitigation of voltage unbalance.

Association of left atrial epicardial adipose tissue with electrogram bipolar voltage and fractionation: Electrophysiologic substrates for atrial fibrillation

Epicardial adipose tissue (EAdT) is metabolically active and likely contributes to atrial fibrillation (AF) through the release of inflammatory cytokines into the myocardium or through its rich innervation with ganglionated plexi at the pulmonary vein ostia. The electrophysiologic mechanisms underlying the association between EAdT and AF remain unclear. The purpose of this study was to investigate the association of EAdT with adjacent myocardial substrate. Thirty consecutive patients who underwent cardiac computed tomography as well as electroanatomic mapping in sinus rhythm before an initial AF ablation procedure were studied. Semiautomatic segmentation of atrial EAdT was performed and registered anatomically to the voltage map. In multivariable regression analysis clustered by patient, age (-0.01 per year) and EAdT (-0.29) were associated with log bipolar voltage as well as low-voltage zones (<0.5 mV). Age (odds ratio [OR]: 1.02 per year), male gender (OR: 3.50), diabetes (OR: 2.91), hypertension (OR: 2.55), and EAdT (OR: 8.56) were associated with fractionated electrograms, and age (OR: 2.80), male gender (OR: 3.00), and EAdT (OR: 7.03) were associated with widened signals. Age (OR: 1.03 per year) and body mass index (OR: 1.06 per kg/m2) were associated with atrial fat. The presence of overlaying EAdT was associated with lower bipolar voltage and electrogram fractionation as electrophysiologic substrates for AF. EAdT was not a statistical mediator of the association between clinical variables and AF substrate. Body mass index was directly associated with the presence of EAdT in patients with AF.

High-Resolution Mapping of Ventricular Scar

Mapping resolution is influenced by electrode size and interelectrode spacing. The aims of this study were to establish normal electrogram criteria for 1-mm multielectrode-mapping catheters (Pentaray) in the ventricle and to compare its mapping resolution within scar to standard 3.5-mm catheters (Smart-Touch Thermocool). Three healthy swine and 11 swine with healed myocardial infarction underwent sequential mapping of the left ventricle with both catheters. Bipolar voltage amplitude in healthy tissue was similar between 3.5- and 1-mm multielectrode catheters with a 5th percentile of 1.61 and 1.48 mV, respectively. In swine with healed infarction, the total area of low bipolar voltage amplitude (defined as <1.5 mV) was 22.5% smaller using 1-mm multielectrode catheters (21.7 versus 28.0 cm2; P=0.003). This was more evident in the area of dense scar (bipolar amplitude <0.5 mV) with a 47% smaller very low-voltage area identified using 1-mm electrode catheters (7.1 versus 15.2 cm(2); P=0.003). In this region, 1-mm multielectrode catheters recorded higher voltage amplitude (0.72±0.81 mV versus 0.30±0.12 mV; P<0.001). Importantly, 27% of these dense scar electrograms showed distinct triphasic electrograms when mapped using a 1-mm multielectrode catheter compared with fractionated multicomponent electrogram recorded with the 3.5-mm electrode catheter. In 8 mapped reentrant ventricular tachycardias, the circuits included regions of preserved myocardial tissue channels identified with 1-mm multielectrode catheters but not 3.5-mm electrode catheters. Pacing threshold within the area of low voltage was lower with 1-mm electrode catheters (0.9±1.3 mV versus 3.8±3.7 mV; P=0.001). Mapping with small closely spaced electrode catheters can improve mapping resolution within areas of low voltage.

Electrogram analysis and pacing are complimentary for recognition of abnormal conduction and far-field potentials during substrate mapping of infarct-related ventricular tachycardia.

Mapping to identify scar-related ventricular tachycardia re-entry circuits during sinus rhythm focuses on sites with abnormal electrograms or pace-mapping findings of QRS morphology and long stimulus to QRS intervals. We hypothesized that (1) these methods do not necessarily identify the same sites and (2) some electrograms are far-field potentials that can be recognized by pacing. From 12 patients with coronary disease and recurrent ventricular tachycardia undergoing catheter ablation, we retrospectively analyzed electrograms and pacing at 546 separate low bipolar voltage (<1.5 mV) sites. Electrograms were characterized as showing evidence of slow conduction if late potentials (56%) or fractionated potentials (76%) were present. Neither was present at (13%) sites. Pacing from the ablation catheter captured 70% of all electrograms. Higher bipolar voltage and fractionation were independent predictors for pace capture. There was a linear correlation between the stimulus to QRS duration during pacing and the lateness of a capturing electrogram (P<0.001), but electrogram and pacing markers of slow conduction were discordant at 40% of sites. Sites with far-field potentials, defined as those that remained visible and not captured by pacing stimuli, were identified at 48% of all pacing sites, especially in areas of low bipolar voltage and late potentials. Initial radiofrequency energy application rendered 74% of targeted sites electrically unexcitable. Far-field potentials are common in scar areas. Combining analysis of electrogram characteristics and assessment of pace capture may refine identification of substrate targets for radiofrequency ablation.