Feasibility of continuous transthoracic cardiac imaging using a novel ultrasound transducer

The feasibility of hands-free transthoracic continuous ultrasonic cardiac imaging has not been demonstrated previously. We developed a 2.5-MHZ spherical transducer mounted in an external housing to permit steering in 360 degrees (CONTISON). The external housing was attached to the chest wall using an adhesive patch.

The transducer was placed in the third or fourth interspace at the left sternal border to permit imaging of the left ventricle (LV) in its short axis and attached to the chest wall. The transducer then was attached to an ultrasound machine. Ten normal subjects and 20 patients with previous myocardial infarction were studied. The following maneuvers were performed at the beginning of the study: (1) The patient was rotated from the supine position (0 degrees ) in 20 degrees increments to the left lateral decubitus position (90 degrees ). The echocardiogram was displayed continuously and was recorded on videotape (parasternal short-axis view) at 0 degrees, 20 degrees, 40 degrees, 60 degrees, 80 degrees, and 90 degrees. (2) The patient was returned to the supine position and an echocardiogram was obtained. The patient was then seated up 20 degrees, 40 degrees, 60 degrees, 80 degrees, and 90 degrees by using the controls on the bed. (3) The patient then was returned to the supine position and the echocardiogram was displayed continuously on the monitor. The echocardiogram was recorded every 15 minutes for a period of 4 hours. All segments of the LV were visualized in the supine position and during lateral rotation (0 degrees -90 degrees ). Thus, body position did not affect the image. All segments of the LV were visualized during sitting up (0 degrees -90 degrees ), and all segments were visualized during the 4 hours of imaging. The patients were able to move around without distortion of the image.

The CONTISON transducer permitted continuous imaging of LV wall motion. Body position did not affect interpretation of wall motion. This device has potential applicability in monitoring LV function in the intensive care setting.