Echocardiographic Comparison of the Standard End-Hole Cannula, the Soft-Flow Cannula and the Dispersion Cannula

Backgroud:

Dislodgement of aortic arch atheroma caused by a perfusion “jet” from the aortic cannula may be a major cause of atheroemboli during coronary artery surgery when using cardiopulmonary bypass (CPB). Two very different cannulas, the Soft-Flow aortic cannula and the Dispersion cannula, which have been designed to reduce exit velocity (cm/s) during perfusion, are compared with a standard steel tip cannula and to each other.

Methods:

To demonstrate any significant differences transesophageal echocardiography (TEE) was used to measure exit velocity of each cannula at a distance of 1, 2, and 3 cm from the tip and compare flow morphology within the aortic arch. Nine patients in whom the cannula tip could be identified and colored Doppler imaging could demonstrate representative morphology were randomly assigned into one of three groups of 3 patients each: group I, a standard steel-tip end-hole cannula (7.3 mm); group II, the Soft-Flow cannula (8.0 mm); and group III, the Dispersion cannula (8.0 mm).

Results:

The standard steel tip cannula demonstrated a long narrow perfusion jet. The Soft-Flow cannula morphology was made up of multiple smaller exiting jets. The Dispersion cannula demonstrated a broad wedge-shaped perfusion pattern. Perfusion hemodynamics (cardiopulmonary bypass hematocrit in d/L, cardiopulmonary bypass blood flow in L/m, mean arterial pressure during cardiopulmonary bypass mm Hg, and perfusion line pressure in mm Hg) were not significantly different between each group. The mean velocities between group I (318 +/- 63 cm/s at 1 cm, 296 +/- 60 cm/s at 2 cm, 271 +/- 85 cm/s at 3 cm) and group II (351 +/- 31 cm/s at 1 cm, 240 +/- 103 cm/s at 2 cm, 171 +/- 120 cm/s at 3 cm) were not statistically different. Group III (the Dispersion cannula) demonstrated significantly reduced velocities (174 +/- 22 cm/s at 1 cm, 138 +/- 23 cm/s at 2 cm, 90 +/- 36 cm/s at 3 cm) when compared with the other two groups (p < 0.05, analysis of variance). Conclusions:

The Dispersion cannula is significantly different with a lower perfusion velocity and the elimination of the exiting jet or jets. This cannula warrants further clinical study as it may reduce atheroemboli during cardiopulmonary bypass.