4.2.8 Contrast echocardiography
Contrast echocardiography is a useful technique, particularly if Doppler is not available. Selective studies can be performed with the use of intra-cardiac catheters; however, non-selective echo-contrast studies are also useful and are simpler to perform. Non-selective investigations can be used to show movement of regurgitant blood across the tricuspid valve, or jets of blood flowing through congenital shunts. A video recording is very helpful for later replay and analysis.
A number of different contrast agents have been used, but a convenient medium which provides very good contrast is a plasma volume expander such as Haemaccel (Hoechst UK Ltd.). This must be agitated to produce microbubbles. This is easily achieved by repeatedly passing the solution from one syringe to another via a three-way tap. Around 10-15 ml of agitated solution are injected rapidly through a catheter into the jugular vein. Contrast is seen filling the right side of the heart with a dense white cloud. It does not pass through the pulmonary capillaries and therefore does not opacify the left side of the heart unless a right-to-left shunt is present.