Assisted venous drainage on cardiopulmonary bypass for minimally invasive aortic valve replacement: is it necessary, useful or desirable?

Assisted venous drainage (AVD) is considered an essential component of the cardiopulmonary bypass (CPB) circuit for minimal access aortic valve replacement (mAVR). The rationale/necessity for AVD in every patient has not been fully elucidated. Data from consecutive patients undergoing isolated first-time mAVR by a single surgeon from March 2006 to October 2008 was prospectively collected. All cases were cannulated centrally. Venous drainage was by a three-stage cannula (Medtronic MC2X) via the right atrial appendage. AVD was utilised intraoperatively at the discretion of the perfusionist and/or surgeon to maintain the required flow rate. Pre- and perioperative data were compared between the two groups. Fifty-seven patients underwent mAVR. Twenty-nine did not require assistance (AVD-), 28 did (AVD+). There were no significant differences between the two groups' age, sex distribution, body mass index and risk stratification data. Patients who required AVD had significantly higher body surface areas (BSAs) [1.93 m(2) (1.56-2.46) vs. 1.79 m(2) (1.41-2.26), P=0.03] and consequent higher CPB flow required [4.62 l/min (3.74-5.90) vs. 4.29 l/min (3.38-5.42), P=0.03]. Patients who required AVD tended to have longer ischaemic times [79.5 min (48-135) vs. 69 min (47-126), P=0.06]. AVD during mAVR is not necessary in every patient. We found it to be necessary in patients with higher BSA (consequently requiring a higher flow rate on CPB).