Intrathoracic Far‐Field Electrocardiogram Allows Continuous Monitoring of Ischemia After Total Coronary Occlusion

Introduction: Recording of intrathoracic far‐field electrocardiograms (FF‐ECG) via can and electrodes of implantable cardioverter‐defibrillators (ICD) is a promising method for continuous monitoring of myocardial ischemia. We assessed the hypothesis that experimentally induced ischemia provokes segment changes in the FF‐ECG that can be detected by the ICD.Methods and Results: In seven pigs with an ICD implanted in the left pectoral region and electrodes placed in the right ventricle and the superior vena cava, we occluded all major coronary arteries in proximal and distal locations for 180 s each. Surface and FF‐ECGs were compared for presence and time course of ischemic ST segment changes. Reliable detection of ischemia by ST segment analysis was possible in all (38/38) experiments. Maximum deviation from baseline was larger in FF‐ECG (1.21 mV) than surface ECG leads (0.23 mV, P < 0.01) for all occlusion sites. Ischemia could be detected earlier (P < 0.05) in the FF‐ECG, with a sensitivity of 100%, 93%, and 100% after occlusions in the left anterior descending, left circumflex, and right coronary arteries, respectively.Conclusion: Intrathoracic FF‐ECG allows reliable and reproducible detection of experimentally induced ischemia originating from all major coronary arteries and therefore could be an interesting tool for clinicians in monitoring high risk patients.