B-PO04-195 IDENTIFICATION OF LOW-VOLTAGE AREAS: A UNIPOLAR, BIPOLAR AND OMNIPOLAR PERSPECTIVE

Abstract

Low-voltage areas (LVA) are commonly considered a surrogate marker for arrhythmogenic tissue with slow conduction, thereby representing potential target sites for ablation therapy. As unipolar electrograms (EGM) comprise a larger region of myocardial electrical activity, bipolar EGM are mainly used to detect scar tissue. However, the efficacy of these strategies remains controversial due to mainly technical disadvantages. Therefore, a so-called omnipolar mapping technique has been recently developed which mathematically extracts maximal bipolar voltage from a collection of EGM. However, it remains unknown whether omnipolar voltages are complementary or contradictory to unipolar and bipolar voltages in classifying LVA. To examine similarities and dissimilarities in omnipolar, unipolar and bipolar voltage distribution and to explore the relation between various types of voltages and conduction velocity (CV). Intra-operative epicardial mapping (interelectrode distance 2mm) was performed during sinus rhythm in 21 patients (48±13 years, 9 male) with atrial volume overload. Cliques of 4 electrodes (2x2 mm) were used to define maximal omnipolar (Vomni,max), unipolar (Vuni,max) and bipolar (Vbi,max) voltages and mean CV. LVA were defined as Vbi,max or Vomni,max ≤0.5 mV. Vuni,max was larger than both Vbi,max and Vomni,max (7.08 [4.22-10.59] mV vs. 5.27 [2.39-9.56] mV and 5.77 [2.58-10.52] mV, P<0.001). The largest bipolar voltage was on average 1.66 (range: 1.0 - 59.0) times larger than the corresponding perpendicular bipolar voltages. LVA identified by a bipolar or omnipolar threshold were characterized by a large range of unipolar voltages and, even though CV was generally decreased, still high CVs and large unipolar voltages were found in these areas. In patients with congenital heart disease, considerable discrepancies regarding LVA were found, which are particularly important as LVA are considered a surrogate marker for arrhythmogenic tissue. Even using directional independent omnipolar voltage to identify LVA, high CVs and large unipolar voltages could still be found within these areas. Therefore, a combination of low unipolar and low omnipolar voltage may be more indicative of ‘true’ LVA.