A system for simultaneous esophageal atrial pacing and ventricular recording in computer analysis of posterior ischemia

Abnormalities of the posterior cardiac wall are often small and obscured by electrical activity of the anterior wall of the left ventricle or by right ventricular hypertrophy. The posterior wall is hidden from the precordial leads by the anterior wall, and electrodes placed on the back are of little use because of their distance from the heart and of the intervening high-resistivity lungs. In contrast to the body surface, the esophagus provides a unique perspective of the posterior aspects of the heart at close range. The authors employed a noninvasive approach to produce cardiac stress and simultaneously record posterior cardiac electrical activity via the esophagus. A new esophageal electrode and instrumentation were developed for acquiring a high-quality esophageal electrocardiogram (ECG) during transesophageal atrial pacing stress. They present their technique for combining stress testing and computer analysis of ST-segment changes in the esophageal ECG as well as preliminary results from one normal subject and one patient with known posteroinferior ischemia.