Mutual Arrangements of Coronary Blood Vessels within the Right Atrial Appendage Vestibule

Background: The aim of our study was to investigate the presence and mutual relationships of coronary vessels within the right atrial appendage (RAA) vestibule. Methods: We examined 200 autopsied hearts. The RAA vestibule was cross-sectioned along its isthmuses (superior, middle, and inferior). Results: The right coronary artery (RCA) was present in 100% of the superior RAA isthmuses but absent in 2.0% of hearts within the middle isthmus and in 6.5% of hearts within the inferior RAA isthmus. Its diameter was quite uniform along the superior (2.6 ± 0.8 mm), middle (2.9 ± 1.1 mm), and inferior (2.7 ± 0.9 mm) isthmuses (p = 0.12). The location of the RCA varied significantly, and it was sometimes accompanied by other accessory coronary vessels. In all the isthmuses, the RCA ran significantly closer to the endocardial surface than to the epicardial surface (p < 0.001). At the superior RAA isthmus, the artery was furthest from the right atrial endocardial surface and this distance gradually decreased between the middle RAA isthmus and the inferior RAA. Conclusions: This study was the most complex analysis of the mutual arrangements and morphometric characteristics of coronary blood vessels within the RAA vestibule. Awareness of additional blood vessels within the vestibule can help clinicians plan and perform safe and efficacious procedures in this region.

In-vivo endocardial and epicardial quantitative comparison of multi-wave based non-invasive inverse electrocardiography

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by the Dutch Heart Foundation Introduction Non-invasive mapping of ventricular activation using inverse electrocardiography (iECG) in patients with cardiomyopathy during sinus rhythm, may improve risk stratification for sudden cardiac death. However, iECG is complicated by multiple simultaneous endocardial activation waves (multi-wave) mediated by the His-Purkinje system, especially when the QRS complex is narrow. The activation estimation should be based on a realistic physiological model of the His-Purkinje system combining multiple waves initiated at His-Purkinje associated endocardial locations. Equivalent double layer based iECG provides an estimation of both the endocardial and epicardial surface. To improve accuracy, equivalent double layer based iECG was supplemented with electro-anatomical structures associated with the His-Purkinje system to test initial ventricular activation (Figure, Panel C). Multi-wave iECG local activation timing (LAT) maps and invasive LAT maps during sinus rhythm were quantitatively compared. Purpose Quantitative comparison of multi-wave iECG in His-Purkinje mediated cardiac activation using invasive activation maps in patients. Methods Thirteen patients referred for invasive electro-anatomical mapping (EAM) of the endocardial and epicardial surface were included. Prior to EAM, each subject underwent 64 electrode body surface potential mapping, cardiac computed tomography (CT) imaging, and 3D imaging of electrode positions. Anatomical models of the ventricles, lungs and thorax were created using CT images and supplemented with electrode positions (Figure, Panel A-B). Electro-anatomical structures associated with the His-Purkinje system were incorporated in ventricular anatomical models (Figure, Panel C) and multiple simultaneous activation waves were simulated. Invasive endocardial and epicardial LAT maps were quantitatively compared to iECG LAT maps. Invasive EAM LAT maps were quantitatively compared to estimated iECG LAT maps (Figure, Panel D) using inter-map correlation coefficients (CC, Pearson’s) and absolute differences (AD). Results Mean inter-map CC and AD were 0.54 ± 0.19 and 18 ± 7 ms respectively for the epicardial surface (n = 13). Similar to the RV endocardial surface (n = 10, CC = 0.50 ± 0.29, AD = 20 ± 8 ms) and the LV endocardial surface (n = 4, CC = 0.44 ± 0.26, AD = 25 ± 7 ms). Conclusion(s): Quantitative comparison of the multi-wave iECG method showed overall moderate performance. This novel iECG method provides a physiologically more realistic and more robust estimation of sinus rhythm and may serve as a tool for detection of electro-anatomical substrates and risk stratification. Compared to other available non-invasive ECG methods, multi-wave iECG captures His-Purkinje mediated ventricular activation better. This method might also be useful for the accurate detection and localization of structural conduction disorders. Abstract Figure. Multi-Wave inverse electrocardiography

Mutual arrangements of coronary blood vessels within the right atrial appendage vestibule.

Introduction: The aim of our study was to investigate the presence and mutual relationships of coronary vessels within the right atrial appendage RAA vestibule. Methods and Results: We examined 200 autopsied hearts. The RAA vestibule was cross sectioned along its isthmuses (superior, middle, and inferior). We assessed the presence and mutual relationships between coronary blood vessels. The right coronary artery (RCA) was present in 100% of the superior RAA isthmuses but absent in 2.0% of hearts within the middle isthmus and in 6.5% of hearts within the inferior RAA isthmus. Its diameter was quite uniform along the superior (2.6±0.8mm), middle (2.9±1.1mm) and inferior (2.7±0.9mm) isthmuses (p=0.12). The location of the RCA varied significantly, and it was sometimes accompanied by other accessory coronary vessels. In all the isthmuses, the RCA ran significantly closer to the endocardial surface than to the epicardial surface (p<0.001). At the superior RAA isthmus, the artery was furthest from the right atrial endocardial surface and this distance gradually decreased between the middle RAA isthmus and the inferior RAA isthmus (9.0±4.0 vs. 6.2±3.0 vs. 4.8±2.3mm, respectively; p<0.001). The interposed RCA was found in 7.0% of cases within the superior isthmus, in 2.5% within the middle isthmus and in 1.5% within the inferior isthmus. Conclusions: This study was the most complex analysis of the mutual arrangements and morphometric characteristics of coronary blood vessels within the RAA vestibule. Awareness of additional blood vessels within the vestibule can help clinicians plan and perform safe and efficacious procedures in this region.

Evaluation of 99mTechnetium-Vancomycin Imaging Potential in Experimental Rat Model for the Diagnosis of Infective Endocarditis

Background: Infective endocarditis (IE) is an infection of the heart’s endocardial surface. In recent years, nuclear imaging methods have gained importance in the diagnosis of IE. The present study aims to investigate the imaging potential of 99mTc-labeled vancomycin ( 99mTc-Vancomycin) as a new agent that would enable the diagnosis of IE in its early stages when it is difficult to diagnose or has small vegetation, in the experimental rat model. Methods: 99mTc-Vancomycin scintigraphy was evaluated for its accumulation in IE with Staphylococcus aureus performed in an experimental rat model. Serial planar scintigraphic and biodistribution analysis of infected vegetations are compared to rats with sterile vegetations. The heart was identified as an infected organ, the liver was identified as a noninfected organ and the heart/liver uptake ratio (T / NT ratio) was compared between infective endocarditis and sterile endocarditis groups. Results: Planar scintigrams (in vivo measurements) showed more uptake in the heart of rats in the infective endocarditis group, compared to the uptake in the heart of rats in the sterile endocarditis group but this difference was not statistically significant (p>0.05). From the ex vivo measurements, the 99mTc-Vancomycin heart uptake increased significantly (p = 0.016), liver uptake was significantly decreased (p = 0.045) and the T/NT ratio was significantly higher (p = 0.014) in the infective endocarditis group compared to the sterile endocarditis group. Conclusions: In this experimental study, 99mTc-Vancomycin scintigraphy ensured the detection of ex vivo infected tissue in a rat model of IE. In addition, the absence of significant 99mTc-Vancomycin uptake in the sterile endocarditis group indicates that this agent targeted the infected tissue instead of the sterile inflammatory tissue. Finally, this agent should also be evaluated with animal-specific imaging devices.

Abstract 14725: Image-based Virtual-heart Predictions Co-localize With ECG-based Automated Localization of Scar-related Ventricular Tachycardias

Introduction: We previously developed an LGE-MRI-based virtual-heart arrhythmia ablation targeting (VAAT) methodology to non-invasively determine potential ablation targets for infarct-related VT. However, it is unknown whether VAAT’s predictions correspond with surface ECG predictions. Hypothesis: We hypothesized that the VAAT predicted VT circuits and potential ablation lesions would co-localize with ECG-based VT-exit predictions from a previously validated population-derived automated VT exit localization (PAVEL) system. Methods: We retrospectively enrolled 5 post-infarct patients who underwent LV endocardial VT ablation and had pre-procedural 2D LGE-MRIs. The PAVEL system based on a population-derived statistical method was used to localize VT-exit sites onto one of 238 triangles on the patient-specific virtual-heart LV endocardial surface using 8 independent ECG leads (I, II, V1-V6). The VAAT methodology incorporating patient-specific scar and infarct border zone distributions was used to identify potential VT circuits and find ablation lesions. Results: Eleven induced VTs were analyzed. Ten VT-exit sites were localized onto the patient-specific virtual-heart LV endocardial surface by the PAVEL system, and were used for the comparisons. One VT-exit site was too basal to be localized onto the virtual-heart geometry. The spatial resolution of the 10 predicted VT-exit sites was 13.8 ± 1.8 mm. VAAT-predicted VT circuits and ablation lesions correlated well with all 10 predicted VT-exit sites. Lastly, VAAT ablation lesions fell within the regions ablated clinically. Conclusions: The VAAT-predicted VT circuits and ablation lesions matched VT-exit sites predicted by the surface ECG-based PAVEL system. Combining these two complementary technologies may improve accuracy for non-invasively identifying optimal ablation targets to increase ablation efficacy.

Evaluation of noninvasive electrophysiological imaging accuracy for focal atrial arrhythmias

Background High accuracy of noninvasive electrocardiographic imaging (ECGI) has recently been shown for topical diagnostics of ventricular arrhythmias. However, the precision of diagnostics of atrial focal arrhythmias requires clarification. To estimate the accuracy of ECGI for premature atrial contraction (PAC) we performed atrial pacing in patients with CRT system and compared early activation zone (EAZ) with pacemaker's tip location. Purpose To determine the accuracy of ECGI for focal atrial arrhythmias using atrial pacing. Methods Twenty-six patients (m/f – 18/9), age (min–max) 52 (26–78) with CRT system and pacemaker's tip location in the right atrium (RA) appendage underwent ECGI (“Amycard 01C”) in combination with CT or MR imaging. Thirty-four atrial pacing (mono- and bipolar) was performed in all patients using standard amplitude 1.5–3.8 mV. Epi-/endocardial polygonal heart models were created and isopotential maps were calculated. The distance between EAZ and the pacemaker's tip were measured for ECG recordings without using the isoline filter on endocardial surface (Fig. 1) as well as for epicardial surface. The time between epicardial and endocardial EAZ breakthrough was calculated also. Results On endocardial surface the EAZ was located in RA appendage, the base of superior cava vena or superior lateral RA wall. The distance (mm) (Me (min; max)) between EAZ and the pacemacer's tip was 28 (6; 68). For epicardial surface in most cases the EAZ was also located in RA appendage, the base of superior cava vena or superior lateral RA wall. In two cases the EAZ was located in inferior septal RA wall, in one case - in superior septal RA wall and in five cases the EAZ was undetectable. The distance between EAZ and the pacemacer's tip was 22 (6; 48). The time (ms) (Mean; Me (min; max)) between EAZ of the endocardial and epicardial surfaces was 16; 7 (0; 68). Conclusion ECGI allows to assess the location of focal atrial arrhythmias on endocardial surface and sometimes on epicardial surface also within the three segments. The results of this study revealed that accuracy of ECGI for atrial arrhythmias is worse than for ventricular arrhythmias. However, it is better on epicardial surface of atrium when EAZ can be determined. Funding Acknowledgement Type of funding source: None

Infective Endocarditis: A Case Series

Infective endocarditis (IE) is an infection of the endocardial surface of the heart. The incidence of IE worldwide is approximately 3 to 10 per 100,000 people annually. Twenty percent of patients die during the hospital stay, and the mortality may reach 25 to 30% six months postinfection. We hereby present our experience of six patients, of whom five survived. The cause of one death was late presentation and lack of coverage for Burkholderia in the prescribed empirical antibiotic therapy. One of our patients, with culture-negative endocarditis, responded to doxycycline and did not require any surgery. Five out of six patients who underwent surgery had vegetations more than 10 mm in size, and one patient had an aortic valve abscess (caused by Staphylococcus haemolyticus). Both prosthetic endocarditis and native valve endocarditis can be treated successfully with antimicrobial agents and surgery (when indicated). A high index of suspicion is required to diagnose IE caused by fungus and atypical bacteria.

A Two-Stage Purkinje Network for More Accurate ECG Representations

In this manuscript we propose a method to generate Purkinje networks that are anatomically and physiologically plausible, for use with in-silico modeling. Purkinje networks play a fundamental role in shaping cardiac electrical activation patterns and their corresponding clinical electrocardiograms (ECGs). Despite a known variability in ventricular activation sequences, certain sites of early activation within the left and right ventricles have been identified in the literature for normal electrical excitation patterns. Nevertheless, in-vivo imaging of Purkinje networks cannot at present yield detailed information on their structure, so there is a genuine need for in-silico models that can construct Purkinje networks that are both anatomically and physiologically plausible, in particular networks that can exhibit correctly situated early activation sites in the ventricles. Of special interest to this manuscript is the method of representation of Purkinje networks by line-like electrical elements that are generated by means of a fractal-tree algorithm (1–3) to overlay the irregular endocardial surfaces. A known drawback to a direct implementation of this approach in complex geometries relates to its incorrect modeling of clinically observed ECGs and electrical activation sequences for a human heart (4). Our aim was thus to correct this deficiency by generating Purkinje networks that leverage a pre-knowledge of the location of early activation sites. At every such site we first generate a Purkinje sub-network. These sub-networks are linked together and to the bundle of His, setting up our first stage of the Purkinje network. Subsequently, we spawn a second stage to the Purkinje network from one or more tips of any given sub-network, to cover the full endocardial surface with Purkinje elements. Our resulting activation sequences and ECGs compare favorably to those of a population of 39 healthy male individuals (the PTB diagnostic database), and our corresponding mechanical markers of cardiac function also match well with the literature.

Endocardial and endo-epicardial substrate mapping and ablation of ventricular arrhythmia in patients with arrhythmogenic right ventricular cardiomyopathy

Purpose: to compare epicardial and endocardial surface area of local abnormal ventricular activity (LAVA) and low voltage zone (LVZ) and effectiveness of endocardial versus combined endo-epicardial ablation of ventricular arrhythmias in ARVC patients.Methods: a prospective observational “case-control” study comprised 20 patients with ARVC and ventricular arrhythmias referred to catheter ablation. The study group with epicardial approach (EPI group) comprised 10 patients with sustained VT, who signed informed consent for the epicardial access. The control group (ENDO group) comprised 10 patients with sustained VT or frequent symptomatic premature ventricular contractions (PVC). Electroanatomical voltage mapping and LAVA ablation was performed.Results: the patient mean age was 41.4±13.8 years, 70% males; 90% patients in the EPI group had sustained VT, 50% - in the ENDO group. In the EPI group the endocardial unipolar low voltage zone area (LVZ) significantly prevailed over the bipolar endocardial LVZ area: 75.4 cm2 [IQR: 23.2; 211.9] vs 6.7 cm2 [IQR: 4.4; 35.5] (Р=0.009). In the ENDO group the LVZ area on unipolar map had a trend toward the prevalence over the bipolar area, but was not statistically different: 12.7 cm2 (IQR: 0; 46.3) vs 3.65 cm2 (IQR: 0; 46.3) (Р>0.05). The epicardial bipolar LVZ area prevailed over unipolar epicardial LVZ area: 65.3 cm2 [IQR: 55.6; 91.3] vs 6.7 cm2 [IQR: 4.4; 35.3] (Р=0.005). Non-inducibility of any ventricular arrhythmia was achieved in 90% of EPI patients and in 80% of ENDO cases. The median follow-up period was 22.3±10.5 months. During a mean follow-up period freedom of ventricular arrhythmia recurrence was 70% in the EPI group and 100% in the control group (Р>0.05).Conclusion: Although there was a significant difference in bipolar LVZ areas between endo- and epicardial maps, our series showed that endocardial only ablation is an effective strategy in ventricular arrhythmia management in ARVC patients.

652The effect of varying irrigation flow rate during irrigated radiofrequency ablation on optimising lesion shape

Funding Acknowledgements Investigator Sponsored Research grant from Boston Scientific Introduction Irrigated catheters are the standard tool for radiofrequency (RF) ablation in the left atrium and ventricles. However, pathological studies of irrigated RF lesions show a "tear-drop" shape, with the widest diameter some depth below the endocardial surface and relative endocardial sparing. This requires overlap of lesions to achieve contiguity at the endocardial surface. There has been little investigation into the effect of altering irrigation rate on lesion shape and volume. Purpose To test the hypothesis that varying the irrigation flow rate would optimise lesion shape by minimising endocardial sparing while maintaining lesion depth. Methods In an ex vivo animal heart model, irrigated ablation lesions were performed in porcine ventricular tissue at 30W using an Intellatip MiFi OI catheter with 5 different irrigation protocols: A. fixed rate (30ml/min); B. continuous reduction (30 to 2ml/min over 30s); C. continuous increase (2 to 30ml/min over 30s); D. stepwise reduction (30ml/min (10s) to 16ml/min (10s) to 2ml/min (10s)); E. stepwise increase (2ml/min (10s) to 16ml/min (10s) to 30ml/min (10s). Contact force (10g) and ablation duration (30s) were constant. Steam pops during ablation were recorded. Tissue sections were stained with triphenyltetrazolium chloride (TTC) after ablation to allow accurate measurement of lesion boundaries. Surface diameter, lesion depth, maximum diameter, and depth at maximum diameter were measured using Vernier Calipers to calculate lesion volume. Pictures of lesions were analysed further by ImageJ software to measure the degree of endocardial sparing. The optimal protocol was further tested against fixed-rate irrigation at 20W – 40W. Results 10-20 lesions were performed for each irrigation protocol. Of the 4 experimental protocols, continuous reduction (protocol B) resulted in the most optimal lesion shape (Figure). With this protocol, endocardial sparing area was significantly reduced compared to fixed-rate irrigation (1.61 vs. 2.64mm2, P &lt; 0.0001), with a trend towards an increase in surface diameter (9.25 vs. 8.46mm, P = 0.08). There was no significant difference in lesion depth (5.35 vs. 4.77mm), lesion volume (374 vs. 332mm3) or maximum diameter (10.3 vs. 10.8mm). Steam pop occurred in 1 of 20 (5%) lesions in each of protocols A and B. Significantly reduced endocardial sparing with preserved volume/depth was consistent for continuous reduction when compared to fixed-rate irrigation across power settings of 20W (17ml/min), 30 W (17ml/min or 30ml/min) and 40W (30ml/min) (P &lt; 0.0001). Conclusions Continuous reduction in irrigation flow rate from 30 to 2ml/min during irrigated RF ablation results in reduced endocardial sparing with preserved lesion depth and volume when compared to fixed-rate irrigation across power settings of 20 – 40W. This may allow for greater lesion spacing while maintaining endocardial contiguity and merits further investigation to improve irrigated RF ablation efficiency. Abstract Figure