Contrast echocardiography — a historical perspective

Abstract

Nearly 25 years ago, Dr Raymond Gramiak and I embarked on a study, using M-mode echocardiographic recordings of the aortic valve to estimate stroke volume from extent and duration of aortic cusp separation. We proceeded to record the aortic valve and root echo simultaneously with measurements of cardiac outputs using the indicator dilution technique in the cardiac catheterization laboratory. It was then a routine practice at the University of Rochester to place a catheter in the left atrium by the trans-septal technique and measure cardiac output by injection of indocyanine green into the left atrium with peripheral arterial sampling. During these a striking enhancement of echo signals was observed: this was termed contrast echocardiography following an analogy with the term ‘contrast angiography’ applied to radiographic procedures. We observed this contrast echo effect with indocyanine green injections, as well as with saline or dextrose in water flush of the catheters. This observation reminded Dr Gramiak of a passing comment by Dr Claude Joyner at the First International Course on Diagnostic Ultrasound, that echo enhancement could be observed with saline injections. Although his observation was not in print, our first published report in 1968 [1] dealing with the M-mode echocardiography of the aortic root credited Dr Joyner with the observation. We utilized contrast echocardiography in order to validate the echo recordings of the aortic root and valve.