The filtered esophageal left heart electrogram is a semi-invasive electrocardiographic method. This technique is able to provide additional information about left atrial and left ventricular activities. Application of a bipolar esophageal electrode Recording of the esophageal left heart electrograms requires a bipolar esophageal electrode. For example, the TOslim electrode (Osypka AG, Rheinfelden, Germany) can be used. It has to be applied perorally or transnasally either with or without any mild sedation. To record left atrial electrograms in adults of medium size, the electrodes are placed at a position of about 38-cm measured from the upper row of teeth. At this height, the maximum amplitude of the left atrial deflection can be expected, which is achieved by careful correction of the lead position. Then the electrode should be fixated at the chin of the patient with a plaster. Filtered bipolar esophageal electrogram To eliminate artifacts in the esophageal left atrial electrogram and to improve the differentiation of the left atrial deflection from the ventricular complex, filtering with a Butterworth highpass is recommended. For instance, the Rostockfilter (Osypka AG Rheinfelden) can be used as separate electronic supplement for electrocardiographs for this purpose. It is not necessary to interconnect different devices in order to record a filtered esophageal electrogram if the programmer ICS3000 (Biotronik GmbH Berlin, Germany) is used. The esophageal electrogram recording feature of the ICS3000 offers a filtered Butterworth high-pass esophageal left atrial electrogram. In combination with the surface ECG, filtered bipolar esophageal left atrial electrogram (LAE) recording can be of advantage in all situations requiring doubtless recognition of the atrial activities. Maximal left ventricular deflection can be found about 3 to 5 cm deeper than maximal left ventricular deflection. The lead position should be carefully adjusted in order to record maximal left atrial or left ventricular deflections, respectively. To eliminate artifacts in the esophageal left atrial electrogram and to improve the differentiation of the left atrial deflection from the ventricular complex, a high-pass filtering is recommended. Good results can be obtained using Butterworth 15 Hz high-pass filtering. In position of maximal left atrial deflection, to achieve maximal suppression of the QRS amplitude, the lower high-pass filter frequency should be switched to 40 Hz. Utilization Filtered bipolar esophageal left atrial electrogram for rhythm analysis In combination with the surface ECG, filtered bipolar esophageal left atrial electrogram (LAE) recording can be of advantage in all situations requiring doubtless recognition of the atrial