Noise Quantification and Noise Reduction for Unipolar and Bipolar Electrograms

Intracardiac electrograms (EGMs) form the basis for the diagnosis of arrhythmia mechanisms. Bipolar EGMs dominate clinical practice despite major disadvantages over unipolar EGMs since noise strongly distorts the latter.In this study, we quantified and reduced the noise level of uni- and bipolar EGMs recorded with Rhythmia HDx and the Orion catheter. Distinct noise frequencies in the power spectral density (PSD) were detected with a sliding window of variable width and subsequently removed by notch filtering. The absolute peak to peak voltage remaining in the inactive segments after baseline removal quantified the noise level of the system. An international, multi-center selection of 33 patients served as a broad sample cohort.The case-specific detection and removal of noise peaks reduced the noise level in unipolar EGMs by 30 % to 0.076 mV compared to standard clinical filtering. With a bipolar noise level of 0.01 mV, we saw that Rhythmia HDx meets the low noise floor claimed in the system specifications. Certain noise frequencies presented permanently in all cases whereas others showed up only intermittently or in individual cases.The suggested extension of filter settings lowers the noise level, enhances the detailed segmentation of low voltage areas, and encourages to exploit the advantages of unipolar over bipolar EGMs in clinical practice.