Micro-Magnetocardiography System with a Single-Chip SQUID Magnetometer Array for QT Analysis and Diagnosis of Myocardial Injury in Small Animals

Development of drugs needs electrophysiological studies of small animals like mice, rats or guinea pigs. Electrocardiography (ECG) of hirsute animals is time-consuming. We have developed a micro magnetometer array with 9-channel superconducting quantum interference device (SQUID) with 2.5-mm diameter pickup-coil for non-contact measurement of magnetocardiogram (MCG) in small animals. The micro-MCG successfully recorded PQRST complex in mice, rats and guinea pigs. Regional myocardial injury was made with cryoinjury probe in rat hearts, and the injured pattern in MCG was recorded. Anterior myocardial injury created QS pattern in MCG, and posterior myocardial injury created QR pattern in MCG. Quinidine-induced QT prolongation was successfully detected by micro MCG in mice and rats. Simultaneous recording of ECG and MCG after intraperitoneal administration of quinidine (60 mg/kg) in guinea pigs. Both QTc in ECG and MCG correlated well. Newly developed micro MCG may facilitate the research process of electrophysiological studies of small animals, and may enable high throughput screening of drug-induced QT abnormality.