Biotelemetry of cardiovascular hemodynamic measurements in miniswine

A three-channel biotelemetry system has been designed and implemented for use in a chronically instrumented animal model of cardiovascular disease. A dual-channel ultrasonic transit-time micrometer allows monitoring of left-ventricular wall motion for the regions perfused by the left circumflex and left anterior descending coronary arteries. A third channel provides left ventricular blood pressure obtained from a high-fidelity blood pressure transducer implanted in the left ventricle. The biotelemetry system features a high voltage dc-dc converter for improved ultrasonic signal strength, a time-to-voltage converter that is highly immune to synchronization frequency variations, low power consumption (approx. 100 mW), small size (4 x 6 x 12 cm), and low weight (approx. 200 g). This three-channel system has enabled our laboratory to continuously monitor untethered animals for 24-h periods. Data obtained from this miniature biotelemetry system can be utilized to quantify myocardial oxygen demand and regional left-ventricular wall thickening.