Unipolar and omnipolar voltage mapping of the pediatric sino-atrial node

Abstract Introduction Sinus node dysfunction (SND) commonly occurs in pediatric patients with congenital heart disease (CHD). It includes disturbances in sino-atrial node (SAN) impulse generation and/or its propagation from SAN exit sites towards the atrial myocardium. Various voltage mapping techniques, i.e. unipolar, bipolar and omnipolar, are available to explore the degree of electrical remodeling. While each technique offers specific advantages and disadvantages, their roles in SAN mapping are not yet fully understood. Purpose 1) to perform epicardial high-resolution voltage mapping of the SAN area in pediatric CHD patients undergoing primary surgical correction and 2) to investigate the interrelationship between unipolar and omnipolar voltages and the added value of either technique with respect to SAN mapping. Methods Intra-operative mapping (192 electrodes (8x24); interelectrode distance 2 mm) of the right atrium (RA) was performed in 45 pediatric patients (0.6 [0.4-3.1] years). Unipolar potential morphology characteristics were computed, including peak-to-peak voltages and relative R/S ratios. Bipolar electrograms (EGM) were constructed from the unipolar potentials in both horizontal and vertical directions. Omnipolar EGMs were constructed from each orthogonal bipolar EGM pair. Omnipolar peak-to-peak voltages were compared to the corresponding unipolar potential voltages. Low-voltage areas (LVA) were defined as unipolar voltage <1 mV and omnipolar voltage <0.5 mV. Results In total, 2313 unipolar EGMs were recorded from which 7831 omnipolar EGMs were derived. Omnipolar voltages surrounding the SAN area were larger than unipolar voltages (6.2 [4.8-7.6] vs 5.2 [3.6-6.3] mV, p<0.001). There was also a strong linear correlation between omnipolar and unipolar voltages (r=0.890, p<0.001). Omnipolar LVAs near the SAN were identified in only 9 patients (20%), while unipolar LVAs were present in 34 patients (76%); 8 patients had combined unipolar and omnipolar LVAs. Unipolar LVAs were larger than omnipolar LVAs (6.5 [4.6-10.5] vs 0.7 [0.5-2.2] %, p<0.001). At the SAN exit site, there were no differences between unipolar and omnipolar voltages (4.1 [2.8-5.7] vs 3.7 [2.6-5.5] mV, p=0.453). However, the morphology of unipolar potentials at the SAN exit site consistently consisted of full S-wave potentials, while the morphologies of omnipolar potentials were highly variable (peak dominance ratio: 0.92 [0.89-0.95] vs 0.38 [0.18-.052], p<0.001). Conclusions At the SAN area, a considerable amount of LVAs could be identified using unipolar voltage mapping. These unipolar potentials typically consisted of full S-wave potentials, which were easily recognizable but probably led to an overidentification of unipolar LVAs. By utilizing combined omnipolar voltage mapping, LVAs near the SAN may be more accurately identified and used to identify patients at risk for developing SND.Examples of SAN mapping