Atrial Surface Area Research Articles

Severity of anemia is correlated with the prevalence of left atrial low-voltage areas in patients with atrial fibrillation ablation

Abstract Background Although left atrial low-voltage areas (LVAs) are well-known indicator of atrial fibrosis and atrial fibrillation (AF) recurrence after catheter ablation, the association between anemia and prevalence of LVAs has not been clarified. We hypothesized that LVAs were more frequently found in patients with anemia than in those with normal hemoglobin levels. Purpose The purpose of this study was to investigate the association between hemoglobin levels and the prevalence of LVAs in patients with AF ablation. Methods In total, 1,473 (age, 68±10 years; female, 492 [33%]; persistent AF, 895 [61%]; CHA2DS2-VASc score, 2.5±1.5 points) consecutive patients who underwent initial AF ablation were enrolled in this study. Hemoglobin levels were measured before the ablation procedure, and anemia was defined as hemoglobin levels < 13.5 g/dL in male and < 12.0 g/dL in female. LVAs was defined as areas with bipolar voltage of <0.5 mV covered ≥5 cm² of left atrial surface area. Results Of 1,473 patients, LVAs existed in 348 (24%) patients. Hemoglobin levels was significantly lower in patients with LVAs than those without (13.4 ± 1.7 vs. 14.2 ± 1.5 g/dL, p <0.001). On classification by gender, only in male, hemoglobin levels were significantly lower in patients with LVAs than those without (Figure 1). The prevalence of LVAs increased with decreasing hemoglobin levels (Figure 2). On multivariate analysis including gender as a variable, anemia was an independent predictor of LVAs (odds ratio, 1.6; 95% confidence interval: 1.1–2.3; p=0.03). Conclusions The prevalence of LVAs increased with decreasing hemoglobin levels in patients with AF ablation. In particular, hemoglobin levels < 13.5 g/dL in male and < 12.0 g/dL in female was an independent predictor of LVA presence.Hemoglobin levels and LVAs presenceHemoglobin and the prevalence of LVAs

Relationship between left atrial isolated surface area and early-term recurrence in patients with persistent atrial fibrillation after cryoballoon ablation

ObjectiveTo investigate the effect of pulmonary vein antrum enlargement combined with left atrial roof cryoballoon ablation in patients with persistent atrial fibrillation (PeAF) by analyzing the relationship between left atrial isolation area surface area (ISA) and early postoperative recurrence.Methods93 patients with PeAF were classified into recurrence and non-recurrence groups according to the results of the 1-year follow-up. Three-dimensional electroanatomical labeling map was constructed and merged with that of the left atrial pulmonary vein CTA, and the ISA and the left atrial surface area (LASA) were measured and analyzed to determine the relationship between ISA/LASA in relation to early postoperative recurrence.Results93 patients were included and followed up for 1 year with AF-free recurrence rate of 75.3%. The ISA of the recurrence group was lower than that of the non-recurrence group. Left atrial internal diameter (LAD), left common pulmonary vein, the ISA, the ISA/LASA and early-term recurrence had statistical significance in both groups. The factors that significantly predicted early-term recurrence were left common pulmonary vein and the ISA/LASA. ISA/LASA (HR 0, 95% CI 0–0.005, P = 0.008) and left common pulmonary vein trunk (HR 7.754, 95% CI 2.256–25.651, P = 0.001) were the independent risk factors for early recurrence. ROC curve analysis showed that ISA/LASA predicted the best early recurrence after operation with a cut-off value of 15.2%.ConclusionA greater ISA/LASA reduces early recurrence after cryoablation in patients with PeAF. An ISA/LASA of 15.2% may be the best cut-off value for predicting early recurrence after cryoablation for PeAF.

Conduction velocity-based functional substrate mapping during atrial fibrillation (AF) enhances identification of AF drivers compared to mapping during sinus rhythm

Abstract Background Conduction velocity (CV) heterogeneity is known to play a role in the initiation and maintenance of atrial fibrillation (AF) [1,2]. CV has been shown to decrease with cycle lengths (CLs) <600ms in low voltage areas (LVAs) [3,4], and with CLs <300ms in non-LVAs [4]. Yet, the impact of rhythm and CL on voltage-independent, CV-based atrial substrate mapping remains uncertain. Purpose This study evaluates CV differences based on mapping protocol and explores the relationship between CV and AF pathologic conduction patterns (PCPs) identified through global, non-contact, charge density mapping (CDM) [5]. Methods CDM was performed in twelve patients with persistent AF, presenting for de novo ablation. All mapping was performed prior to any ablation. Sinus rhythm (SR) CV was assessed during atrial pacing at two CLs (380ms and 800ms). To mitigate the impact of wavefront direction, pacing was performed at three sites: mid coronary sinus, left atrial appendage, and right atrial appendage. AF CV was determined from a 20-second continuous recording of global propagation. PCPs were identified as: focal firing (FF), rotational propagation (Localised Rotational Activation [LRA]), and pivoting propagation (Localised Irregular Activity [LIA]) [5]. Patients’ left atrial geometries consisted of approximately 3000 vertices, facilitating paired comparisons of spatial data. At each vertex, values for median CV dependent on mapping protocol and frequency of PCPs were utilised for analysis. Variables are presented as mean±standard deviation, median (interquartile range), and count (percentage) as appropriate. All analyses were performed using R (version 4.1.2). CV distributions were compared using the Analysis of Variance test. Results Mean age was 64±12 years, eight (67%) were male, median time since AF diagnosis was 3.1 (2-3.5) years, and median CHA2DS2-VASc score was 2 (2-4). Median CV across our cohort was significantly lower during AF than SR with either long or short CL pacing (0.37mm/ms vs 0.66mm/ms vs 0.61mm/ms, p<0.001). Histograms of CV vs left atrial surface area demonstrated similar distributions for both CLs. However, there was poor overlap with AF, which was prominently skewed towards slower CVs (Figure 1). Slower CVs during AF were associated with an increased frequency of PCPs (Figure 2), particularly FF with CVs <0.2mm/ms, and LRA and LIA with CVs <0.4mm/ms. This association was absent during SR. Conclusions Rhythm has a significant impact on CV-based functional substrate mapping. Slower CVs observed during AF likely result from the presence of CLs shorter than 300ms, which impact both LVA and non-LVA areas. Crucially, areas of slow CV during AF were associated with the location of PCPs. Mapping performed during AF may improve identification of areas where functional remodelling has preceded structural. Such areas, characterised by CV heterogeneity, may serve as promising targets for catheter ablation.Figure 1.Figure 2.

PO-02-205 ELECTROGRAPHIC FLOW CONSISTENCY CORRELATES WITH HIGH-DENSITY BIPOLAR VOLTAGE MAPS IN SINUS RHYTHM AND ATRIAL FIBRILLATION

In patients with atrial fibrillation (AF), left atrial scar revealed by low voltage areas on 3D electroanatomic mapping have been correlated with scar on late gadolinium enhanced cardiac magnetic resonance imaging, which is recognized as a surrogate for fibrosis. Electrographic Flow (EGF) mapping reconstructs global atrial wavefront propagations in near real-time. Electrographic flow consistency (EGFC) quantifies concordance of observed wavefront patterns and may provide insight into the nature of atrial substrate where diseased substrate shows more chaotic wavefront propagation and lower FC. Correlate EGFC with regional bipolar voltage values in patients during AF and sinus rhythm (SR). FLOW EVAL-AF is a single-center, prospective study of 10 AF patients who underwent concomitant high-density bipolar voltage mapping with HD Grid and EGF mapping with 64-pole basket catheter. Biatrial voltage maps and 1-minute EGF maps from 2-3 standard basket positions per atria were made prior to any induction or ablation. Atrial surface area with voltage >0.5 mV was computed from 2D voltage map projections. EGF fields computed per 2-sec segment of recording. Overall EGFC per atrium computed as average of the modulus of individual EGF vectors, where vector length represents consistency of flow patterns in arbitrary units. We compared % atrial surface area with normal voltage v. mean EGFC across EGF recordings per atria in a given rhythm. Data from 8 patients (2 AF; 6 SR) was analyzed; 2 excluded for non-comparable voltage map acquisition parameters. Mean age 70±11 years; 1 female; mean LA size 4.5±0.35 cm. Surface area % with voltage >0.5 mV was 0.24±0.08 in AF v. 0.36±0.05 in SR. Mean EGFC in AF 0.74±0.14 and in SR 1.0±0.11. Intraprocedural rhythm change occurred in 5 (3 induced into AF; 2 converted to SR post-PVI), and all had higher voltage values overall and higher mean EGFC in SR v. AF. Pooling data from all pre-procedure voltage maps and EGF maps revealed overall correlation between EGFC and bipolar voltage from both atria and in both rhythms (r=0.67, p=4.8x10-3). Both EGFC and bipolar voltage values were higher in SR v. AF. EGFC correlated with voltage across both atria and in both SR and AF. Global EGFC can be obtained with 1-minute recordings in 2-3 basket positions per atria and may provide another measure of the degree of atrial myopathy similar to the information gained from high-density bipolar voltage mapping.

PO-02-065 CATHETER ABLATION WITH TERMINATION OF PERSISTENT ATRIAL FIBRILLATION USING SPATIOTEMPORAL DISPERSION

Several strategies of electrogram (EGM) guided catheter ablation of atrial fibrillation (AF) have been previously described. A spatiotemporal dispersion (SD) ablation strategy targeting AF drivers with very high termination rates has been reported; however, these sites have not been well characterized. The purpose of this study is to validate the prior experience with SD ablation in the persistent AF cohort and further characterize the regions of AF termination. Consecutive patients with persistent AF undergoing radiofrequency catheter ablation were included. Electroanatomic mapping of SD areas was performed during AF. Ablation was delivered initially at sites of continuous SD, followed by pulmonary vein isolation in all patients. If AF did not terminate, additional regions of intermittent SD were ablated. If AF terminated to atrial tachycardia or flutter, additional electroanatomic mapping and ablation was performed to achieve sinus rhythm. Representative EGMs at sites of continuous SD, intermittent SD, and no SD are shown in Figures 1A, 1B, and 1C, respectively. Left atrial (LA) volume and surface area, termination sites, and procedural characteristics are reported. A total of 20 consecutive patients (13 male, 67 ± 9 years) with persistent AF (median time from diagnosis 5 years) undergoing ablation were included in the study. The majority of continuous SD was seen on the anterior wall (18/20 patients) and septum (15/20 patients) and occasionally on the posterior wall (8/20 patients). 17/20 (85%) patients successfully terminated to sinus rhythm during the procedure. The majority of the termination sites were on the septum and anterior wall (12/17) with none on the posterior wall. LA volume by echocardiography was smaller in the termination group (84 vs. 105 mL, p < 0.01) and fluoroscopy use was less in the termination group (2.3 vs. 4.8 min, p = 0.03). There was no difference in ejection fraction, LA surface area, radiofrequency time, or procedure time (p = NS). A very high termination rate of persistent AF was achievable with ablation of SD regions. These regions likely represent drivers of AF and seem to localize predominantly on the septum and anterior wall of the LA, and rarely on the posterior wall. Ablation incorporating SD mapping may allow for patient-tailored approach to AF ablation.

Cannabinoid receptor agonist attenuates angiotensin II-induced enlargement and mitochondrial dysfunction in rat atrial cardiomyocytes.

Pathological remodeling of atrial tissue renders the atria more prone to arrhythmia upon arrival of electrical triggers. Activation of the renin-angiotensin system is an important factor that contributes to atrial remodeling, which may result in atrial hypertrophy and prolongation of P-wave duration. In addition, atrial cardiomyocytes are electrically coupled via gap junctions, and electrical remodeling of connexins may result in dysfunction of coordinated wave propagation within the atria. Currently, there is a lack of effective therapeutic strategies that target atrial remodeling. We previously proposed that cannabinoid receptors (CBR) may have cardioprotective qualities. CB13 is a dual cannabinoid receptor agonist that activates AMPK signaling in ventricular cardiomyocytes. We reported that CB13 attenuates tachypacing-induced shortening of atrial refractoriness and inhibition of AMPK signaling in the rat atria. Here, we evaluated the effects of CB13 on neonatal atrial rat cardiomyocytes (NRAM) stimulated by angiotensin II (AngII) in terms of atrial myocyte enlargement and mitochondrial function. CB13 inhibited AngII-induced enhancement of atrial myocyte surface area in an AMPK-dependent manner. CB13 also inhibited mitochondrial membrane potential deterioration in the same context. However, AngII and CB13 did not affect mitochondrial permeability transition pore opening. We further demonstrate that CB13 increased Cx43 compared to AngII-treated neonatal rat atrial myocytes. Overall, our results support the notion that CBR activation promotes atrial AMPK activation, and prevents myocyte enlargement (an indicator that suggests pathological hypertrophy), mitochondrial depolarization and Cx43 destabilization. Therefore, peripheral CBR activation should be further tested as a novel treatment strategy in the context of atrial remodeling.

Deep learning estimation of three-dimensional left atrial shape from two-chamber and four-chamber cardiac long axis views.

Left atrial volume is commonly estimated using the bi-plane area-length method from two-chamber (2CH) and four-chamber (4CH) long axes views. However, this can be inaccurate due to a violation of geometric assumptions. We aimed to develop a deep learning neural network to infer 3D left atrial shape, volume and surface area from 2CH and 4CH views. A 3D UNet was trained and tested using 2CH and 4CH segmentations generated from 3D coronary computed tomography angiography (CCTA) segmentations (n = 1700, with 1400/100/200 cases for training/validating/testing). An independent test dataset from another institution was also evaluated, using cardiac magnetic resonance (CMR) 2CH and 4CH segmentations as input and 3D CCTA segmentations as the ground truth (n = 20). For the 200 test cases generated from CCTA, the network achieved a mean Dice score value of 93.7%, showing excellent 3D shape reconstruction from two views compared with the 3D segmentation Dice of 97.4%. The network also showed significantly lower mean absolute error values of 3.5 mL/4.9 cm2 for LA volume/surface area respectively compared to the area-length method errors of 13.0 mL/34.1 cm2 respectively (P < 0.05 for both). For the independent CMR test set, the network achieved accurate 3D shape estimation (mean Dice score value of 87.4%), and a mean absolute error values of 6.0 mL/5.7 cm2 for left atrial volume/surface area respectively, significantly less than the area-length method errors of 14.2 mL/19.3 cm2 respectively (P < 0.05 for both). Compared to the bi-plane area-length method, the network showed higher accuracy and robustness for both volume and surface area.

Interatrial conduction time is associated with left atrial low voltage area and predicts the recurrence after single atrial fibrillation ablation.

Interatrial conduction time (IACT) prolongs in fibrotic left atrium. We tested the hypothesis that IACT is related to left atrial low voltage area (LVA) and predicts the recurrence after single atrial fibrillation (AF) ablation. One hundred sixty-four consecutive AF patients (79 non-paroxysmal) who underwent initial ablation in our institute were analyzed. IACT and LVA were defined as interval from the onset of P-wave to the basal left atrial appendage (P-LAA) activation, and area with bipolar electrogram < 0.5mV covering over 5% of the total left atrial surface area during sinus rhythm, respectively. Pulmonary vein antrum isolation, non-PV foci ablation, and atrial tachycardia (AT) ablation were performed without substrate modification. LVA was frequently identified in patients with prolonged P-LAA ≥ 84 ms (n = 28) compared with patients with P-LAA < 84 ms (n = 136). Patients with P-LAA ≥ 84 ms were older (71 ± 10 vs. 65 ± 10 years, p = .0061), and had more frequent non-paroxysmal AF (75% vs. 43%, p = .0018), larger left atrial diameter (43.5 ± 4.5 vs. 39.3 ± 5.7 mm, p = .0003), and higher E/e' ratio (14.4 ± 6.5 vs. 10.5 ± 3.7, p < .0001) compared with P-LAA < 84 ms patients. After a mean follow-up period of 665 ± 153 days, Kaplan-Meier curve analysis showed that AF/AT recurrences was more frequently observed in patients with prolonged P-LAA (Log-rank p = .0001). Additionally, univariate analysis revealed that P-LAA prolongation (OR=1.055 per 1ms, 95% CI: 1.028-1.087, p < .0001) and the existence of LVA (OR=5.000, 95% CI: 1.653-14.485 p = .0053) were predictors of AF/AT recurrences after single AF ablation. Our results suggested that prolonged IACT as measured by P-LAA was associated with LVA and predicts AT/AF recurrence after single AF ablation.

The impact of sacubitril/valsartan on outcome in patients suffering from heart failure with a concomitant diabetes mellitus.

Guidelines classify sacubitril/valsartan as a significant part of medical treatment of heart failure with reduced ejection fraction (HFrEF). Data have shown that the HbA1c levels in patients with diabetes mellitus could be impacted by sacubitril/valsartan. A possible positive effect in diabetes patients treated with sacubitril/valsartan on outcome and echocardiography parameters is not well studied yet. The aim of the present study was to compare the impact of sacubitril/valsartan on life-threatening arrhythmias, atrial fibrillation, different echocardiography parameters and congestion rate in patients suffering from HFrEF according to the diagnosis diabetes mellitus or no diabetes mellitus. Consecutive 240 patients with HFrEF from 2016 to 2020 were treated with sacubitril/valsartan and separated to concomitant diabetes mellitus (n=87, median age 68years interquartile range (IQR) [32-87]) or no diabetes mellitus (n=153, median age 66year IQR [34-89]). Different comorbidities and outcome data were evaluated over a follow-up period of 24months. Arterial hypertension (87% vs. 64%; P<0.01) and coronary artery disease (74% vs. 60%; P=0.03) were more often documented in patients with diabetes mellitus compared with patients without diabetes mellitus. Over the follow-up of 24months several changes were noted in both subgroups: Median left ventricular ejection fraction (EF) increased significantly in non-diabetes (27% IQR [3-44] at baseline to 35% IQR [13-64]; P<0.001), but not in diabetic patients (29% IQR [10-65] at baseline to 30% IQR [13-55]; P=0.11). Accordingly, NT-proBNP and troponin-I levels decreased significantly in non-diabetes patients (NT-brain natriuretic peptide [NT-proBNP] from median 1445pg/mL IQR [12.6-74676] to 491pg/mL IQR [13-4571]; P<0.001, troponin-I levels from 0.099ng/mL IQR [0.009-138.69] to 0.023ng/mL IQR [0.006-0.635]; P<0.001), but not in diabetic patients (NT-proBNP from 1395pg/mL IQR [100-29924] to 885pg/mL IQR [159-4331]; P=0.06, troponin-I levels from 0.05ng/mL IQR [0.013-103.0] to 0.020ng/mL IQR [0.015-0.514]; P=0.27). No significant change of laboratory parameters e. g. glomerular filtration rate, potassium level and creatinine levels were found in diabetes or non-diabetes patients. Comparing further echocardiography data, left atrial surface area, right atrial surface area, E/A ratio did not show a significant change either in the diabetes or non-diabetes group. However, the tricuspid annular plane systolic excursion was significantly increased in non-diabetes mellitus patients (from 17mm IQR [3-31] to 18mm [2.5-31]; P=0.04), and not in diabetic s patients (17.5mm IQR [8-30] to 18mm IQR [14-31]; P=0.70); the systolic pulmonary artery pressure remained unchanged in both groups. During follow-up, a similar rate of ventricular tachyarrhythmias was observed in both groups. The congestion rate decreased significantly in both groups, in diabetes patients (44.4% before sacubitril/valsartan and 13.5% after 24months treatment; P=0.0009) and in non-diabetic patients (28.4% before sacubitril/valsartan and 8.4% after 24months treatment; P=0.0004). The all-cause mortality rate was higher in patients with diabetes mellitus as compared with those without diabetes (25% vs. 8.1%; P<0.01). Sacubitril/valsartan reverses cardiac remodelling in non-diabetes patients. However, it reduces the congestion rate in diabetes and non-diabetes patients. The rates of ventricular tachyarrhythmias were similar in DM compared with non-DM over follow-up. The mortality rate remained to be over follow-up higher in diabetes patients compared with non-diabetes; however, it was lower compared with published data on diabetes and concomitant HFrEF not treated with sacubitril/valsartan.

Impact of CPAP on the Atrial Fibrillation Substrate in Obstructive Sleep Apnea: The SLEEP-AF Study.

Observational studies report that obstructive sleep apnea (OSA) is associated with an increasingly remodeled atrial substrate in atrial fibrillation (AF). However, the impact of OSA management on the electrophysiologic substrate has not been evaluated. In this study, the authors sought to determine the impact of OSA management on the atrial substrate in AF. We recruited 24 consecutive patients referred for AF management with at least moderate OSA (apnea-hypopnea index [AHI]≥15). Participants were randomized in a 1:1 ratio to commence continuous positive airway pressure (CPAP) or no therapy (n=12 CPAP; n=12 no CPAP). All participants underwent invasive electrophysiologic study (high-density right atrial mapping) at baseline and after a minimum of 6months. Outcome variables were atrial voltage (mV), conduction velocity (m/s), atrial surface area<0.5mV (%), proportion of complex points (%), and atrial effective refractory periods (ms). Change between groups over time was compared. Clinical characteristics and electrophysiologic parameters were similar between groups at baseline. Compliance with CPAP therapy was high (device usage: 79% ± 19%; mean usage/day: 268 ± 91min) and resulted in significant AHI reduction (mean reduction: 31 ± 23 events/h). There were no differences in blood pressure or body mass index between groups over time. At follow-up, the CPAP group had faster conduction velocity (0.86 ± 0.16 m/s vs 0.69 ± 0.12 m/s; P(time× group)=0.034), significantly higher voltages (2.30 ± 0.57mV vs 1.94 ± 0.72mV; P< 0.05), and lower proportion of complex points (8.87% ± 3.61% vs 11.93% ± 4.94%; P = 0.011) compared with the control group. CPAP therapy also resulted in a trend toward lower proportion of atrial surface area<0.5mV (1.04% ± 1.41% vs 4.80% ± 5.12%; P=0.065). CPAP therapy results in reversal of atrial remodeling in AF and provides mechanistic evidence advocating for management of OSA in AF.

Impact of Adenosine on Wavefront Propagation in Persistent Atrial Fibrillation: Insights From Global Noncontact Charge Density Mapping of the Left Atrium.

BackgroundAdenosine shortens action potential duration and refractoriness and provokes atrial fibrillation. This study aimed to evaluate the effect of adenosine on mechanisms of wavefront propagation during atrial fibrillation.Methods and ResultsThe study included 22 patients undergoing catheter ablation for persistent atrial fibrillation. Left atrial mapping was performed using the AcQMap charge density system before and after administration of intravenous adenosine at 1 or more of 3 time points during the procedure (before pulmonary vein isolation, after pulmonary vein isolation, and after nonpulmonary vein isolation ablation). Wave‐front propagation patterns were evaluated allowing identification and quantification of localized rotational activation (LRA), localized irregular activation, and focal firing. Additional signal processing was performed to identify phase singularities and calculate global atrial fibrillation cycle length and dominant frequency. A total of 35 paired maps were analyzed. Adenosine shortened mean atrial fibrillation cycle length from 181.7±14.3 to 165.1±16.3, (mean difference 16.6 ms; 95% CI, 11.3–21.9, P<0.0005) and increased dominant frequency from 6.0±0.7 Hz to 6.6±0.8 Hz (95% CI, 0.4–0.9, P<0.0005). This was associated with a 50% increase in the number of LRA occurrences (16.1±7.6–24.2±8.1; mean difference 8.1, 95% CI, 4.1–12, P<0.0005) as well as a 20% increase in the number of phase singularities detected (30.1±7.8–36.6±9.3; mean difference 6.5; 95% CI, 2.6–10.0, P=0.002). The percentage of left atrial surface area with LRA increased with adenosine and 42 of 70 zones (60%) with highest density of LRA coincided with high density LRA zones at baseline with only 28% stable across multiple maps.ConclusionsAdenosine accelerates atrial fibrillation and promotes rotational activation patterns with no impact on focal activation. There is little evidence that rotational activation seen with adenosine represents promising targets for ablation aimed at sites of stable arrhythmogenic sources in the left atrium.

PO-710-02 PATIENT COMORBIDITIES AND ABLATION TECHNIQUE ARE IMPORTANT DETERMINANTS OF FIRST PASS PULMONARY VEIN ISOLATION

First pass isolation (FPI) of the pulmonary veins (PVs) is a good predictor of durability of PV isolation and success rate of AF ablation. Systematic analysis of predictors of FPI has not previously been performed. To investigate how variations in ablation technique and patient comorbidities influence acute durable isolation during PVI. Raw data was exported from first time PVIs performed using the CARTO system for 62 consecutive patients. Cases were imported into Matlab using openEP and lesion characteristics and locations were extracted. Separate multivariate logistic regression analyses for both ablation technique and patient characteristics were performed for each vein. Left sided FPI was achieved in 42 patients (68%) and right sided FPI in 31 (50%). The commonest sites needing reinforcement were carina and anterior left superior (LS)PV on the left and the carina and posterior right inferior (RI)PV on the right (Figure). In terms of predictors of FPI for the LIPV, increased patient weight predicted reduced success (OR 0.93, p=0.018) and closer lesion-ostium distance posteriorly predicted increased success (OR 0.88, p=0.037). For the LSPV, larger atrial surface area in comparison to area ablated predicted reduced success (OR 0.83, p=0.024). For the RSPV, the presence of hypertension (OR 0.20, p=0.039) and coronary disease (OR 0.29, p=0.033) significantly reduced the chance of FPI. In addition, lower lesion-ostium distance anteriorly increased the chance of FPI (OR 0.87, p=0.024). For the RIPV, an enhanced impedance drop in the posterior (OR 1.61, p=0.004) and anterior (OR 1.12, p=0.03) segments, significantly increased success. The acute success of AF ablation in terms of FPI is affected by ablation technique and comorbidities. It seems particularly important to ablate closer to the ostium to achieve FPI in the anterior RSPV and posterior LIPV. At the posterior and anterior RIPV it is of particular importance to obtain a good impedance drop during ablation. Increased patient weight appears to increase the difficulty of isolating the LIPV while hypertension and coronary disease are associated with reduced chance of FPI at the RSPV. It is possible that the operator being mindful of these associations could increase success rates and/or durability of PVI.

Preoperative mitral annulus size - Can we get it right?

Objective:We looked for a correlation between the surgically measured mitral valve size and the cardiac dimensions (left ventricle internal diameter, left atrial size, aorta size, and body surface area) measured by preoperative and intraoperative echocardiography. We also assessed to see if we could predict the mitral prosthesis size based on the correlation data obtained.Methods:The hospital records of 180 patients who underwent mitral valve replacement (MVR) with TTK Chitra valve between January 2008 and December 2012 at our hospital, were studied. The correlation between surgically measured mitral annulus size to left ventricular internal diameter systolic (LVIDS) and diastolic (LVIDD), left atrial size (linear measurement), and aorta size on echocardiography and body surface area was calculated using Pearson correlation coefficient. Mean LVIDS was calculated for each valve prosthesis size separately and the correlation was studied.Results:The correlation between mitral valve prosthesis size and left ventricular internal diameter (systolic) showed a Pearson coefficient of 3.3 with significance at the level 0.01. Mitral valve size and left atrial size showed a correlation coefficient of 2.7 with significance at the level 0.01. The correlation coefficient for mitral valve size with left ventricular internal diameter diastolic, aorta and body surface area were 2.5, 1.9, and 1.8, respectively. There was a gradual increase in the mean LVIDS with increase in the prosthetic valve size. Box plot and scatter plot showed linear correlation between valve size and mean LVIDS.

Impact of the size of non-ablated left atrial posterior wall area on outcomes after extensive encircling pulmonary vein isolation.

The aim of this study was to evaluate the impact of the size of the isolated surface area and non-ablated left atrial posterior area after extensive encircling pulmonary vein isolation (EEPVI) for non-paroxysmal atrial fibrillation (AF) on arrhythmia recurrence. This study included 132 consecutive persistent AF patients who underwent EEPVI guided by Ablation Index (AI). The isolated antral surface area (IASA) excluding the pulmonary veins, the non-ablated left atrial (LA) posterior wall surface area (PWSA), the ratio of IASA to LA surface area (IASA/LA ratio), and the ratio of PWSA to LA surface area (PWSA/LA ratio) were assessed using CARTO3 and the association with AF and atrial tachycardia (AT) recurrence was examined. At a mean follow-up of 13.2 ± 7.3months, sinus rhythm was maintained in 115 (87%) patients. In the univariate Cox regression analysis, the factors that significantly predicted AT/AF recurrence were a history of heart failure, a higher CHA2DS2-VASc score, a larger LA diameter, and a larger PWSA/LA ratio. Multivariate Cox regression analysis revealed that the independent predictors of AT/AF recurrence were LA diameter [hazard ratio (HR) 1.120 per 1mm increase; 95% confidence interval (CI) 1.006-1.247; P = 0.039] and PWSA/LA ratio (HR 1.218 per 1% increase; 95% CI 1.041-1.425; P = 0.014). Receiver operating characteristics curve analysis yielded an optimal cut-off value of 8% for the PWSA/LA ratio. The Kaplan-Meier survival curve showed that patients with a larger PWSA/LA ratio had poorer clinical outcomes (Log-rank P = 0.001). A larger PWSA/LA ratio was associated with a high AT/AF recurrence rate in patients with non-paroxysmal atrial fibrillation.

Using machine learning to identify local cellular properties that support re-entrant activation in patient-specific models of atrial fibrillation.

AimsAtrial fibrillation (AF) is sustained by re-entrant activation patterns. Ablation strategies have been proposed that target regions of tissue that may support re-entrant activation patterns. We aimed to characterize the tissue properties associated with regions that tether re-entrant activation patterns in a validated virtual patient cohort.Methods and resultsAtrial fibrillation patient-specific models (seven paroxysmal and three persistent) were generated and validated against local activation time (LAT) measurements during an S1–S2 pacing protocol from the coronary sinus and high right atrium, respectively. Atrial models were stimulated with burst pacing from three locations in the proximity of each pulmonary vein to initiate re-entrant activation patterns. Five atria exhibited sustained activation patterns for at least 80 s. Models with short maximum action potential durations (APDs) were associated with sustained activation. Phase singularities were mapped across the atria sustained activation patterns. Regions with a low maximum conduction velocity (CV) were associated with tethering of phase singularities. A support vector machine (SVM) was trained on maximum local conduction velocity and action potential duration to identify regions that tether phase singularities. The SVM identified regions of tissue that could support tethering with 91% accuracy. This accuracy increased to 95% when the SVM was also trained on surface area.ConclusionIn a virtual patient cohort, local tissue properties, that can be measured (CV) or estimated (APD; using effective refractory period as a surrogate) clinically, identified regions of tissue that tether phase singularities. Combing CV and APD with atrial surface area further improved the accuracy in identifying regions that tether phase singularities.

The impact of an empiric superior vena cava isolation added to pulmonary vein isolation for non-paroxysmal atrial fibrillation associated with left atrial low voltage areas

Abstract Introduction Left atrial low-voltage areas (LVAs) are associated with recurrence after radiofrequency catheter ablation of atrial fibrillation (AF). However, the impact of LVAs on recurrence after an empiric pulmonary vein isolation (PVI) plus superior vena cava isolation (SVCI) strategy for non-Paroxysmal AF (PAF) patients remains unclear. Purpose We evaluated the impact of LVAs on the recurrence of atrial tachyarrhythmias (ATs)/AF in patients who underwent an empiric SVCI added to the PVI for non-PAF. Methods We enrolled 153 consecutive patients with non-PAF who underwent a PVI alone (PVI group; n=51) or empiric PVI plus SVCI (PVI+SVCI group; n=102). Left atrial voltage maps were constructed during sinus rhythm to identify the LVAs (&amp;lt;0.5 mV). No patients underwent a substrate modification of the LVAs. We divided the patients into two groups based on the LVAs (with or without an LVA &amp;gt;5% of the left atrial surface area) and investigated the ATs/AF free survival rate after the initial and multiple procedures. Results LVAs were identified in 65% and 73% of the PVI and PVI + SVCI groups, respectively (P=0.319). In the PVI group, the 18-month ATs/AF-free survival was 61% of the patients without LVAs and 27% of patients with LVAs after the initial session (P=0.018) (Figure 1-A). Seventy-two percent of the patients without LVAs and 46% of those with LVAs were free from ATs/AF after multiple sessions (P=0.083) (Figure 1-B). In the PVI+SVCI group, 50% of the patients with LVAs and 61% of those without LVAs had no recurrence after the initial session (P=0.374) (Figure 2-A). Moreover, there was no significant difference in the 18-month ATs/AF-free survival between the patients with and without LVAs after multiple sessions (73% vs. 79%; P=0.520) (Figure 2-B). Conclusion A PVI alone strategy for non-PAF patients with LVAs had limited efficacy for the outcomes, even with multiple procedures. However, an SVCI may have the potential to compensate for an impaired outcome in patients with LVAs. Funding Acknowledgement Type of funding source: None

P935Can we predict the occurrence of persistent atrial fibrillation in large animal models to improve study efficiency?

Abstract Funding Acknowledgements British Heart Foundation Project Grant FS/17/54/33126 Background A key consideration when using animals in research is maximising experimental efficiency to minimise the number of animals required. Large animal models have proven an invaluable tool for establishing pathophysiological mechanisms underpinning atrial fibrillation (AF) and testing novel therapeutics, however animals may be resistant to developing the arrhythmias required. While the relationships between atrial refractory periods, conduction velocity, surface area, and vulnerability to fibrillation have been established in clinical practice, these parameters are not regularly used to design animal studies of persistent AF (PsAF). Purpose We investigated whether routinely collected baseline parameters could be used to improve experimental efficiency in an ovine model, by predicting the development of PsAF as opposed to arrhythmia resistance. The aims were to: reduce the number of animals used in future studies, and avoid prolonged experiments in animals likely to be resistant to AF. Methods All procedures were conducted with respect to the Animals [Scientific Procedures] Act, UK, 1986; and were approved by the local ethical review board. The ovine model consisted of healthy adult Welsh mountain sheep that underwent implantation of a neurostimulator connected via an endocardial pacing lead to the right atrial appendage. The device was programmed to deliver intermittent 30 second bursts of 50Hz and sheep were monitored over an eight week period for PsAF. Eight variables were collected at time of implant including weight (kg), left atrial diameter (LAD; cm), P wave duration (msec), PR interval (msec), atrial effective refractory period (ERP; msec), atrial conduction velocity (CV; m/s), AF inducibility with 50Hz bursts (secs), and rate threshold of atrial action potential alternans (msec). Analysis of the data was performed using multiple logistic regression and receiver-operator characteristic (ROC) curves. Regression coefficients are presented as natural logarithm of odds ratios (OR) with 95% confidence intervals (CI). Results Seventeen sheep were included in this study. Five (29%) developed PsAF whereas twelve (71%) were resistant (non-sustained or no AF). Univariate analysis found none of the parameters alone could predict PsAF, however ERP (OR -0.05, CI -.01 to 0.01, p = 0.089) and LAD (OR 8.1, CI -1.6 to 17.5, p = 0.095) suggested a combination may be predictive. A multivariate analysis using Fibrillation number (calculated as LAD / [ERP X CV]) was predictive (OR 26.9, CI 1.1 to 52.7; p = 0.04], with an area under ROC curve of 0.85 (p = 0.027). Conclusions Fibrillation number can predict the development of PsAF in healthy sheep. Practically speaking, this means animals with: a larger LAD, shorter ERP and slower CV are more likely to develop PsAF. These findings can be used to optimise the design of future studies, particularly by reducing the number of animals required.

005 Impact of Continuous Positive Airway Pressure on the Atrial Substrate in Patients With Obstructive Sleep Apnoea and Atrial Fibrillation: The SLEEP-AF Substrate Sub-Study

Obstructive sleep apnoea (OSA) is associated with an increasingly remodeled atrial substrate in atrial fibrillation (AF). Management of OSA has also been linked with improved management outcomes of AF. However, the impact of OSA management on the electrophysiologic atrial substrate has not been evaluated. To determine the impact of OSA management on the atrial substrate in AF. We recruited 24 consecutive patients having catheter ablation for AF with at least moderate OSA (AHI ≥15). Participants were randomised in a 1:1 ratio to receive continuous positive airway pressure (CPAP) or no therapy. At baseline, all participants underwent invasive electrophysiologic study comprising high density right atrial mapping and evaluation of effective refractory periods (ERP). After minimum of 6 months, the electrophysiologic protocol was repeated. Data was blinded and analysed offline. Outcome variables were atrial voltage (mV), conduction velocity (m/s), atrial surface area <1.5mV (%), atrial surface area <0.5mV (%), complex points (%) and atrial ERP (ms). There were no differences in baseline characteristics between groups and electrophysiologic parameters were comparable at baseline. Participants having CPAP were highly compliant (device usage: 79±19%, usage time: 268±91mins) resulting in significant AHI reduction (mean reduction: 31±23). There were no differences in blood pressure or body mass index between groups over time. The table presents data showing that CPAP results in marked reverse atrial remodelling. CPAP therapy results in reversal of atrial remodelling, providing mechanistic evidence advocating for management of OSA in AF.

Blood pressure-related electrocardiographic findings in healthy young individuals

Purpose: Elevated blood pressure induces electrocardiographic changes and is associated with an increase in cardiovascular disease later in life compared to normal blood pressure levels. The purpose of this study was to evaluate the association between normal to high normal blood pressure values (90–139/50–89 mmHg) and electrocardiographic parameters related to cardiac changes in hypertension in healthy young adults.Methods: Data from 1449 volunteers aged 18–30 years collected at our centre were analyzed. Only subjects considered healthy by a physician after review of collected data with systolic blood pressure values between 90 and 139 mmHg and diastolic blood pressure values between 50 and 89 mmHg were included. Subjects were divided into groups with 10 mmHg systolic blood pressure increment between groups for analysis of electrocardiographic differences. Backward multivariate regression analysis with systolic and diastolic blood pressure as a continuous variable was performed.Results: The mean age was 22.7 ± 3.0 years, 73.7% were male. P-wave area, ventricular activation time, QRS-duration, Sokolow–Lyon voltages, Cornell Product, J-point–T-peak duration corrected for heart rate and maximum T-wave duration were significantly different between systolic blood pressure groups. In the multivariate model with gender, body mass index and cholesterol, ventricular rate (standardized coefficient (SC): +0.182, p < .001), ventricular activation time in lead V6 (SC= +0.065, p = .048), Sokolow–Lyon voltage (SC= +0.135, p < .001), and Cornell product (SC= +0.137, p < .001) were independently associated with systolic blood pressure, while ventricular rate (SC= +0.179, p < .001), P-wave area in lead V1 (SC= +0.079, p = .020), and Cornell product (SC= +0.091, p = .006) were independently associated with diastolic blood pressure.Conclusion: Blood pressure-related electrocardiographic changes were observed incrementally in a healthy young population with blood pressure in the normal range. These changes were an increased ventricular rate, increased atrial surface area, ventricular activation time and increased ventricular hypertrophy indices on a standard 12 lead electrocardiogram.

Association between nonalcoholic fatty liver disease and cardiac function and structure-a meta-analysis.

Nonalcoholic fatty liver disease is increasingly recognized as the hepatic counterpart of metabolic syndrome. It is hypothesized that structural and functional cardiac changes may be associated with this metabolic disease. We aimed to gather the existing information on the association of nonalcoholic fatty liver disease with cardiac alterations, and to evaluate a possible correlation between them. Systematic review of Medline searching results for original articles studying NAFLD and cardiac parameters until August 2018. A meta-analysis was conducted to each parameter of cardiac structure and function selected, using Review Manager 5.3 software. This study was conducted according to preferred reporting items for systematic reviews and meta-analysis (PRISMA). A total of 16 studies met the eligibility criteria and were included in the meta-analysis. There was a significant association between nonalcoholic fatty liver disease and (1) higher left ventricle mass and ratios between left ventricle mass and both height and body surface area; (2) higher LVEDD; (3) higher left atrium diameter and ratio between left atrial volume and body surface area; (4) higher posterior wall and septum thickness; (5) lower E/A wave ratio; (6) higher E/E' ratio; (7) longer deceleration time and (8) longer relaxation time. NAFLD associates with adverse structural alterations and cardiac dysfunction. Our results highlight the importance of identifying NAFLD in patients with metabolic dysfunction as this may represent an additional contributor to cardiovascular risk.