Tri-axial graphics as an aid to understanding left ventricular function in conscious dogs

Ultrasonic distance gauges were implanted in the left ventricle of dogs to measure continuously ventricular wall thickness and small axis diameter. A miniature transducer was implanted to measure intraventricular pressure. The circumflex artery could be occluded mechanically to mimic coronary spasm. Recordings were made on tape after allowing eight days post-operative recuperation. The taped signals were digitised and processed to show graphical relationships between selected variables. We found that triaxial (3D) graphics greatly enhanced our ability to interpret moment by moment changes in these relationships, and recommend this procedure to others.