TORSO MAPPING CAN IDENTIFY CHANGES IN VENTRICULAR ACTIVATION-RECOVERY INTERVALS DURING REGIONAL ISCHAEMIA THAT ARE NOT DETECTED USING THE STANDARD ECG

Diagnosing myocardial ischaemia with a standard 12 lead ECG may result in false negatives due to its poor spatial resolution. We correlated changes in epicardial and torso electrograms (EGs) during regional ventricular ischaemia in a 29 kg anaesthetised pig that was artificially ventilated and thoracotomised. A suture snare was used to ligate the left anterior descending (LAD) coronary artery and an elasticized sock containing 127 unipolar stainless steel contact electrodes (inter-electrode spacing approximately 7 mm) was placed over the epicardium. The chest was re-closed and a vest containing 256 ECG electrodes (inter-electrode spacing approximately 15 mm) was fitted to the torso. Simultaneous arrays of epicardial and torso EGs (sampled at 2 kHz using a UnEmap data acquisition system1) were recorded at 20 s intervals during four minutes of LAD occlusion, followed by a period of reperfusion. Activation-recovery intervals (ARIs) and Q-T intervals (QTIs) were calculated from the EGs. Data were fitted to anatomically accurate computational models of the porcine ventricular epicardium (obtained using 3D echocardiography) and thorax (obtained by customizing a generic thorax model, derived from computerised tomography imaging)2. LAD occlusion caused the minimum ventricular epicardial ARI to steadily decrease (see table), whilst the location of this minimum shifted from the posterio-basal ventricular muscle (control) to the middl