Functional characterization of atrial electrograms in sinus rhythm delineates sites of parasympathetic innervation in patients with paroxysmal atrial fibrillation.
ABSTRACT This study sought to characterize left atrial (LA) sinus rhythm electrogram (EGM) patterns and their relationship to parasympathetic responses during atrial fibrillation (AF) ablation.
The mechanistic basis of fractionated LA EGMs in patients with paroxysmal AF is not well understood.
We analyzed 1,662 LA ablation sites from 30 patients who underwent catheter ablation for paroxysmal AF. Pre-ablation EGM characteristics (number of deflections, amplitude, and duration) were measured in sinus rhythm. Parasympathetic responses during radiofrequency application (increase of atrial-His interval by > or =10 ms or decrease of sinus rate by > or =20%) were assessed at all sites. We also prospectively studied the effect of adenosine, a pharmacological agent mimicking acetylcholine signaling in myocytes, on LA EGMs. Finally, we performed mathematical simulations of atrial tissue to delineate possible mechanisms of fractionated EGMs in sinus rhythm.
A specific pattern of pre-ablation sinus rhythm EGM (deflections > or =4, amplitude > or =0.7 mV, and duration > or =40 ms) was strongly associated with parasympathetic responses (sensitivity 72%, specificity 91%). The sites associated with these responses were found to be located mainly in the posterior wall of the LA. Adenosine administration and mathematical simulation of the effect of acetylcholine were able to reproduce a similar EGM pattern.
Parasympathetic activation during AF ablation is associated with the presence of pre-ablation high-amplitude fractionated EGMs in sinus rhythm. Local acetylcholine release could potentially explain this phenomenon.
Article: Investigation of atrial vulnerability by analysis of the sinus node EG from atrial fibrillation models using a phase synchronization method.[show abstract] [hide abstract]
ABSTRACT: Atrial fibrillation (AF) can result in life-threatening arrhythmia, and a clinically convenient means for detecting vulnerability remains elusive. We investigated atrial vulnerability by analyzing the sinus electrogram (EG) from AF animal models using a phase synchronization method. Using acetylcholine (ACh)-induced acute canine AF models (n= 4), a total of 128 electrical leads were attached to the surface of the anterior and posterior atria, and the pulmonary veins to form an electrocardiological mapping system. ACh was injected at varying concentrations with ladder-type adjustments. Sinus EGs and induced AF EGs that pertain to specific ACh concentrations were recorded.We hypothesize that the atrial vulnerability may be correlated with the Shannon entropy (SE) of the phase difference matrix that is extracted from the sinus EG. Our research suggests that the combination of SE with the synchronization method enables the sinus node EG to be analyzed and used to estimate atrial vulnerability.IEEE transactions on bio-medical engineering 08/2012; 59(9):2668-76. · 2.15 Impact Factor
Article: Electrogram fractionation: the relationship between spatiotemporal variation of tissue excitation and electrode spatial resolution.[show abstract] [hide abstract]
ABSTRACT: Fractionated electrograms are used by some as targets for ablation in atrial and ventricular arrhythmias. Fractionation has been demonstrated to result when there is repetitive or asynchronous activation of separate groups of cells within the recording region of a mapping electrode(s). Using a computer model, we generated tissue activation patterns with increasing spatiotemporal variation and calculated virtual electrograms from electrodes with decreasing resolution. We then quantified electrogram fractionation. In addition, we recorded unipolar electrograms during atrial fibrillation in 20 patients undergoing atrial fibrillation ablation. From these we constructed bipolar electrograms with increasing interelectrode spacing and quantified fractionation. During modeling of spatiotemporal variation, fractionation varied directly with electrode length, diameter, height, and interelectrode spacing. When resolution was held constant, fractionation increased with increasing spatiotemporal variation. In the absence of spatial variation, fractionation was independent of resolution and proportional to excitation frequency. In patients with atrial fibrillation, fractionation increased as interelectrode spacing increased. We created a model for distinguishing the roles of spatial and temporal electric variation and electrode resolution in producing electrogram fractionation. Spatial resolution affects fractionation attributable to spatiotemporal variation but not temporal variation alone. Electrogram fractionation was directly proportional to spatiotemporal variation and inversely proportional to spatial resolution. Spatial resolution limits the ability to distinguish high-frequency excitation from overcounting. In patients with atrial fibrillation, complex fractionated atrial electrogram detection varies with spatial resolution. Electrode resolution must therefore be considered when interpreting and comparing studies of fractionation.Circulation Arrhythmia and Electrophysiology 12/2011; 4(6):909-16. · 6.46 Impact Factor
Conference Proceeding: Electrogram fractionation caused by microfibrosis: insights from a microstructure model[show abstract] [hide abstract]
ABSTRACT: Fractionated electrograms have long been associated with non-uniform propagation in the atria, owing to a heterogeneous substrate marked by fibrosis. It is not known, however, whether the features of the electrograms can be used to quantify the degree of fibrosis in the heart. A computer model of a monolayer of cells was developed to investigate how progression of microfibrosis impacts electrogram morphology and the degree of fractionation. The analysis of unipolar electrograms simulated in the model revealed that more pronounced microfibrosis was associated with slow conduction and electrogram waveforms featuring a higher degree of fractionation and a larger spatial variability in morphology. This modeling framework forms a basis to better understand the genesis of fractionated electrograms and for developing a strategy to use the electrogram features to quantify fibrosis in patients with atrial fibrillation, possibly impacting the target sites for catheter ablation.Computers in Cardiology, 2008; 10/2008