Z. Ihara

Evaluation of ablation patterns using a biophysical model of atrial fibrillation

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Surgical/Radiofrequency (RF) ablation is a therapeutic procedure that consists of creating lines of conduction block to interrupt AF. The present study evaluated 13 different ablation patterns by means of a biophysical model of the human atria. In this model, ablation lines were abruptly applied transmurally during simulated sustained AF, and success rate, time to AF termination and average beat-to-beat interval were documented. The gold standard Cox’s Maze III procedure was taken as reference. The effectiveness of twelve less invasive patterns was compared to it. In some of these incomplete lines (entailing a gap) were simulated. Finally, the computer simulations were compared to clinical data. The results show that the model reproduces observations made in vivo: (1) the Maze III is the most efficient ablation procedure; (2) less invasive patterns should include lines in both right and left atrium; (3) incomplete ablation lines between the pulmonary veins and the mitral valve annulus lead to uncommon flutter; (4) computer simulations of incomplete lines are consistent with clinical results of non-transumural RF ablation. Biophysical modeling may therefore be considered as a useful tool for understanding the mechanisms underlying AF therapies.

Suppression of Ventricular Activity in the Surface Electrocardiogram of Atrial Fibrillation

The analysis of the surface electrocardiogram is potentially useful for the study of atrial fibrillation. Since the ventricular activity is much stronger than the atrial activity, one has to suppress it. To this end, we applied two ICA algorithms to a data set of surface electrocardiogram signals recorded in clinical conditions. We also propose a procedure to judge the quality of the suppression of ventricular activity and the extraction of atrial activity. We apply this procedure to our extracted activities and discuss our results.

Adaption of the standard 12-lead ECG system focusing on atrial electrical activity

An adaptation is presented of the positioning of some of the electrodes of the standard 12-lead ECG, aimed at extracting more information on atrial activity. It uses new positions for four of the six precordial electrodes, anchored to the remaining two. Its performance was tested by applying it to ECG signals during atrial fibrillation, simulated by means of a biophysical model of human atria and thorax. This enabled the analysis to be carried out without the interference of the ventricular activity. The signals simulated on each of the two lead systems, denoted here as ECG and ACG (atriocardiogram), were compared by studying the singular values of the data matrix (size 9timesN) representing the independent information in the data. After normalization with respect to the first singular value, the singular value spectrum of the ACG lied well above that of the ECG data. The results indicate that the ACG lead system provides more information on the atrial electric activity than the standard 12-lead ECG configuration

Evaluation of ablation patterns by means of a computer model of human atria

Atrial fibrillation is the most common form of arrhythmia. Consequences for patients are discomfort, blood clot formation and a high risk of embolic stroke. The choice of therapy is patient-dependent and is usually based on the degree of disability and the associated symptoms. Surgical/catheter ablation is a therapeutical procedure, which consists in creating lines of conduction block to interrupt maintenance of atrial fibrillation. The purpose of this paper is to evaluate different ablation patterns by means of a computer model of human atria. The importance of ablation lines in the right or left atrium is studied and compared to Maze-type procedures, which represent the standard in ablation therapy.