Simplified esophageal electrocardiography using bipolar recording leads.

Diagnosing cardiac arrhythmias is easier if the P wave can be identified clearly. Esophageal electrocardiography with a unipolar recording lead attached to the V1 terminal of an ECG machine has been used in the past to show P waves. We used both bipolar and unipolar recording leads and standard ECG equipment to record the esophageal ECG and then compared the results obtained with both leads. Twenty-two cardiac rhythms were evaluated in 15 patients. The unipolar lead recorded a P wave that was smaller than the QRS complex (0.83 +/- 0.47 mV and 1.28 +/- 0.79 mV, respectively, p less than 0.01) and was obscured when the two depolarizations were nearly simultaneous. The bipolar lead recorded a P wave that was larger than the QRS complex (0.93 +/- 0.62 mV and 0.33 +/- 0.3 mV, respectively, p less than 0.001) and was never obscured. The unipolar lead recorded a P-to-QRS ratio that was smaller than that recorded by the bipolar lead (0.8 +/- 0.5 and 3.3 +/- 1.8, respectively, p less than 0.001). A bipolar esophageal lead can be recorded simply at the bedside using a standard ECG machine and is superior to the conventional unipolar lead.