Abstract Body (Do not enter title and authors here): 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. However, the interrelationship between unipolar and omnipolar voltages and the added value of either technique with respect to SAN mapping is unknown. Therefore, we performed epicardial high-resolution voltage mapping of the SAN area in pediatric CHD patients.
Methods: Intra-operative mapping (128 electrodes; interelectrode distance 2mm) was performed in 45 patients (0.6[0.4-3.1] years). Unipolar morphology characteristics were computed, including peak-to-peak voltages and R/S ratios. Bipolar potentials were constructed from unipolar potentials in both horizontal and vertical directions. Omnipolar potentials were constructed from each orthogonal bipolar pair. Omnipolar peak-to-peak voltages were compared to the corresponding unipolar voltages. Low-voltage areas were defined as unipolar voltage <1 mV (U-LVA) and omnipolar voltage <0.5 mV (O-LVA).
Results: In total, 2313 unipolar electrograms were recorded from which 7831 omnipolar electrograms 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). O-LVAs near the SAN were identified in only 9 patients (20%), while U-LVAs were present in 34 patients (76%); 8 patients had combined U/O-LVAs. U-LVAs were larger than O-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, unipolar potentials at the SAN exit site consistently consisted of full S-waves (R/S ratio: 0.99[0.94-1]), while omnipolar potential morphology was highly variable.
Conclusions: At the SAN area, a considerable amount of U-LVAs could be identified. These unipolar potentials typically consisted of full S-waves, which were easily recognizable but probably led to an overidentification of U-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.