A NEW HIGH-RESOLUTION ESOPHAGEAL ELECTROCARDIOGRAPHY RECORDING TECHNIQUE - AN EXPERIMENTAL APPROACH FOR THE DETECTION OF MYOCARDIAL-ISCHEMIA

Criteria for ischemic changes in the esophageal electrocardiograph (E- ECG) have not been standardized and validated. The main goal of this s tudy was to evaluate the experimental esophageal recording of myocardi al ischemia and to assess the association between ST segment alternans in the E-ECG and ischemia. Experiments were performed on 18 anestheti zed sheep with occlusion of a branch of the left anterior descending a rtery. The bipolar signals were recorded via an esophageal lead contai ning three chloridized silver electrodes. Electrical signals were ampl ified in a self-designed, battery-supported preamplifier (gain 1000, f requency range 0.01-2000 Hz, common mode rejection 140 dB, signal nois e 5-7 mu V P-P), then sent to a digital oscilloscope for display and t o a pulse code-modulated recorder. Surface electrocardiography (S-ECG) data were also recorded. Ischemia E-ECG revealed homogenous ST segmen ts without any beat-to-beat alternans. Two minutes after occlusion, 14 of 15 sheep (93%) showed repetitive beat-to-beat fluctuations within the ST segment on the E-ECG. Of the 15 sheep, 7 (47%) showed ischemia in the S-ECG (P < 0.01). For calculation of the dynamic changes in the ST segment in the E-ECG, the difference in the amplitudes of the ST s egment of five successive beats to the next beat, performed for 200 co nsecutive beats, was calculated. The central tendency of the sum of th ese values before versus during ischemia was 2000 mV/ms versus 5000 mV /ms (Hodges-Lehmann point estimator) (95% confidence intervals 1700/25 00 versus 3350/9250 [lower limit/upper limit]). The authors have estab lished a close temporal relationship between the magnitude of ST segme nt alternans recorded via E-BCG and myocardial ischemia. Implications: The study presents the use of an esophageal electrocardiograph for de tection of progressive changes of myocardial ischemia and infarction. During acute myocardial ischemia and infarction in sheep, the esophage al electrocardiograph has visually apparent ST alternans of amplitude in the millivolt range, in part due to a special amplifier (0.01-2000 Hz). This is therefore one very promising technique for better evaluat ion of electrocardiographic changes of ischemia.