Use of chronically-implanted ultrasonic crystals in the intact heart of the cat.

Methodology has been developed for utilising ultrasonic crystals in closed chest cats to measure alterations in regional left ventricular function. The technique is a modification of one previously utilised to monitor regional left ventricular length and thickness changes in closed chest dogs. The ultrasonic crystals we have utilised in the cat heart can monitor regional left ventricular epicardial length changes chronically and are able to identify changes in inotropic state produced by the administration of either isoprenaline or propranolol. These ultrasonic crystals should be useful in the acute and chronic monitoring of left ventricular function in closed chest and relatively small experimental animals that might be studied in a variety of different protocols.