Directed networks as a novel way to describe and analyze cardiac excitation : directed graph mapping

Networks provide a powerful methodology with applications in a variety of biological, technological and social systems such as analysis of brain data, social networks, internet search engine algorithms, etc. To date, directed networks have not yet been applied to characterize the excitation of the human heart. In clinical practice, cardiac excitation is recorded by multiple discrete electrodes. During (normal) sinus rhythm or during cardiac arrhythmias, successive excitation connects neighboring electrodes, resulting in their own unique directed network. This in theory makes it a perfect fit for directed network analysis. In this study, we applied directed networks to the heart in order to describe and characterize cardiac arrhythmias. Proof-of-principle was established using in-silico and clinical data. We demonstrated that tools used in network theory analysis allow determination of the mechanism and location of certain cardiac arrhythmias. We show that the robustness of this approach can potentially exceed the existing state-of-the art methodology used in clinics. Furthermore, implementation of these techniques in daily practice can improve the accuracy and speed of cardiac arrhythmia analysis. It may also provide novel insights in arrhythmias that are still incompletely understood

Development and validation of an algorithm to predict the success of the ablation of macroreentrant atrial tachycardia.

Ablation of macroreentrant atrial tachycardia (MRAT) is challenging because of complex anatomy and multiple reentrant loops. In order to define an effective ablation strategy, 3-dimensional electroanatomic mapping proved very useful. To identify predictors of ablation procedure failure may be helpful for patients treatment. In the first part of our study we analyzed into details the electroanatomical features of the reentry circuit in MRAT and we compared the characteristics of successfully versus unsuccessfully consecutive treated patients undegoing electroanatomic mapping and ablation of MRAT in order to identify variables predicting the ablation outcome. Ablation was linearly placed at the mid-diastolic isthmus (MDI) to achieve arrhythmia interruption and conduction block. Variables were analyzed for predictors of both procedural failure and cumulative failure. We demonstrated a significant difference as to the electroanatomic mapping characteristics: successfully treated cases showed a narrower target isthmus with a slower conduction velocity across the isthmus itself. In the second part of our research, we analyzed the relation between the strongest predictors of procedure outcome identified in part I (MDI width and conduction velocity across the MDI) and the chance of success of the ablation procedure. In order to analyze this relation and to predict the difficulty of the ablation procedure, we developed an algorithm and we validated prospectively the accuracy of the developed model in a second patient series

Development and validation of an algorithm to predict the success of the ablation of macroreentrant atrial tachycardia.

Ablation of macroreentrant atrial tachycardia (MRAT) is challenging because of complex anatomy and multiple reentrant loops. In order to define an effective ablation strategy, 3-dimensional electroanatomic mapping proved very useful. To identify predictors of ablation procedure failure may be helpful for patients treatment. In the first part of our study we analyzed into details the electroanatomical features of the reentry circuit in MRAT and we compared the characteristics of successfully versus unsuccessfully consecutive treated patients undegoing electroanatomic mapping and ablation of MRAT in order to identify variables predicting the ablation outcome. Ablation was linearly placed at the mid-diastolic isthmus (MDI) to achieve arrhythmia interruption and conduction block. Variables were analyzed for predictors of both procedural failure and cumulative failure. We demonstrated a significant difference as to the electroanatomic mapping characteristics: successfully treated cases showed a narrower target isthmus with a slower conduction velocity across the isthmus itself. In the second part of our research, we analyzed the relation between the strongest predictors of procedure outcome identified in part I (MDI width and conduction velocity across the MDI) and the chance of success of the ablation procedure. In order to analyze this relation and to predict the difficulty of the ablation procedure, we developed an algorithm and we validated prospectively the accuracy of the developed model in a second patient series

Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates

The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates

Signal-Averaged ECG: Basics to Current Issues

Signal-averaged ECG (SAECG) is a high-resolution, noninvasive electrocardiographic method enabling detection of late ventricular potentials (LVP), which are low-amplitude and high-frequency signals, predicting reentry ventricular arrhythmias, and sudden cardiac death (SCD). Three criteria are used to detect late ventricular potentials as follows: signal-average ECG QRS duration (SAECG-QRS), the duration of the terminal part of the QRS complex with an amplitude below 40 μV (LAS40) and the root mean square (RSM) signal amplitude of the last 40 ms of the signal < 20 μV (RMS40). Late ventricular potentials can be detected not only at the end of a QRS complex but also as intra-QRS (IQRS) potentials. Signal-averaged ECG was modified to enable the analysis of the P-wave and to detect atrial late potentials (ALPs), low-amplitude potentials at the terminal part of the filtered P-wave, and predictors of atrial fibrillation (AF). Late atrial and ventricular potentials originate from areas of delayed, fragmented, and heterogenous conduction within atrial or ventricular myocardium. This chapter reviews the most important mechanisms explaining the occurrence of late ventricular, intra-QRS, and atrial potentials; their predictive value for arrhythmia, focusing on recent clinical data, long-term follow-up, and outcome; and analysis of SAECG variables in cardiac and noncardiac diseases