Comparison of flow differences among venous cannulas.
1. Double caval cannulas with snares provide maximum venous decompression, especially of the superior vena cava. Decompression of the right side of the heart is passive and in the heart being perfused requires venting of the right atrium by release of tapes or atrial suction. 2. Double caval cannulas without snares provide good and consistent venous and atrial decompression. The ventricle is decompressed well except when the perfused heart is in the circumflex position. 3. A large single cannula (e.g., USCI 40F) can decompress both the venous system and right side of the heart, although venous and atrial drainage are much less efficient when the heart is in the circumflex position. 4. The Sarns 51F cavoatrial cannula decompressed the venous system as efficiently as the double caval cannulas. In fact, decompression of the atrium and ventricle were consistently much better with the cavoatrial cannula than with any of the other methods. 5. Efficient venous and myocardial decompression using the 51F cavoatrial cannula requires the atrial drainage ports to be positioned in the upper middle section of the atrium. Clinically, the cannula position is correct when both the single and double marking bands on the cannula are outside the atrium.