Left atrial voltage mapping: defining and targeting the atrial fibrillation substrate

Abstract

Low atrial endocardial bipolar voltage, measured during catheter ablation for atrial fibrillation (AF), is a commonly used surrogate marker for the presence of atrial fibrosis. Low voltage shows many useful associations with clinical outcomes, comorbidities and has links to trigger sites for AF. Several contemporary trials have shown promise in targeting low voltage areas as the substrate for AF ablation; however, the results have been mixed. In order to understand these results, a thorough understanding of voltage mapping techniques, the relationship between low voltage and the pathophysiology of AF, as well as the inherent limitations in voltage measurement are needed. Two key questions must be answered in order to optimally apply voltage mapping as the road map for ablation. First, are the inherent limitations of voltage mapping small enough as to be ignored when targeting specific tissue based on voltage? Second, can conventional criteria, using a binary threshold for voltage amplitude, truly define the extent of the atrial fibrotic substrate? Here, we review the latest clinical evidence with regard to voltage-based ablation procedures before analysing the utility and limitations of voltage mapping. Finally, we discuss omnipole mapping and dynamic voltage attenuation as two possible approaches to resolving these issues.

Impact of Left Atrial Bipolar Electrogram Voltage on First Pass Pulmonary Vein Isolation During Radiofrequency Catheter Ablation

“…In this context, low atrial bipolar voltage as a marker of left atrial fibrosis is proposed as a potential contributor that may affect the biophysics of energy delivery during RFA. Specific voltage thresholds to define atrial scarring have not been histologically validated (Sim et al, 2019). In a study of 20 patients with paroxysmal AF, Kapa et al (2014) evaluated thresholds for atrial scarring and reported different cut offs for different segments of the left atrium.…”

Left atrial scar identification and quantification in sinus rhythm and atrial fibrillation

“…Wider or narrower electrode spacing distances influences travel time (or along the same lines, lesser or greater velocity of the depolarization respectively) and will result in differences in amplitude and thus morphology of recording. 27 There is also evidence to show that increasing interelectrode distance leads to increased voltages but only in select patients. 28 Furthermore, larger sized electrodes which cover greater area may potentially demonstrate increased voltage readings, such as those elicited by Marcus et al 29 although this is not the case universally.…”

Electroanatomic bipolar mapping for detection of arrhythmogenic substrate in catheter ablation of atrial fibrillation

“…Поэтому, вместо гистологического определения, в большинстве современных исследований определена амплитуда сигнала рубца <0,05 мВ как значение, которое первоначально возникло из базового шума ранних электроанатомических систем картирования [15]. Кроме того, значение 0,5 мВ, которое широко используется для определения низкого вольтажа, хотя и удобно, но не обосновано наличием подтверждённых патологических изменений в структуре или функции предсердий [19].…”