Impact of Closed Minimal Extracorporeal Circulation on Microvascular Tissue Perfusion during Surgical Aortic Valve Replacement: Intravital Imaging in a Prospective Randomized Study

OBJECTIVES:

Closed minimal extracorporeal circulation (MECC) systems currently do not represent the standard of surgical care for open-heart surgery. Yet, considering the beneficial results reported for coronary artery bypass graft (CABG) surgery, we used an MECC system in aortic valve replacement (AVR) and analysed the effects on intraoperative microvascular perfusion in comparison with conventional open extracorporeal circulation (CECC).

METHODS:

In the current study, we analysed alterations in microvascular perfusion at 4 predefined time points (T1-T4) during surgical
AVR utilizing orthogonal polarization spectral (OPS) imaging. Twenty
patients were randomized for being operated on utilizing either MECC or
CECC. Changes in functional capillary density (FCD, cm/cm2), mircovascular blood flow velocity (mm/s) and vessel diameter (μm) were analysed by a blinded investigator.

RESULTS:

After
the start of extracorporeal circulation and aortic cross-clamping (T2),
both groups showed a significant drop in FCD, but with a significantly
higher FCD in the MECC group (153.1 ± 15.0 cm/cm² in the CECC
group vs 160.8 ± 12.2 cm/cm² in the MECC group, P = 0.034).
During the late phase of the cardiopulmonary bypass (CPB) (T3), the FCD
was still significantly depressed in both treatment groups (153.5 ± 14.6
cm/cm² in the CECC group, P <0.05 vs 'T1'; 159.5 ± 12.4 cm/cm² in the MECC group, P <0.05 versus 'T1'). After termination of CPB (T4), the FCD recovered in both groups to baseline values. Microvascular blood flow velocity tended to remain at a higher level in the MECC group, whereas haemodilution during CPB was significantly reduced in the MECC group.

CONCLUSIONS:

The
use of MECC in AVR did not affect procedural safety and, resulted in
beneficial preservation of microvascular blood flow velocity and
significantly reduced haemodilution during CPB. In contrast to CABG surgery, the use of MECC did not improve FCD during surgical
AVR. Clinical advantages possibly resulting from attenuated
haemodilution and preservation of microvascular blood flow velocity
require further validation in larger patient cohorts.