DTS årsmøde 2016
Leila Louise Benhassen
Evaluation of Saphenous Vein comparing two harvesting techniques:
Conventional- and novel “no-touch” technique for Coronary Artery Bypass Grafting
(CABG)
LL Benhassen1,2, LP Vestergaard1, IS Modrau2, F de Paoli1,2, E Bødkjer1
1
Department of Biomedicine, Aarhus University, Denmark
2
Department of Cardiothoracic Surgery, Aarhus University Hospital, Denmark
Background
The saphenous vein (SV) is the most commonly used conduit for CABG. Its superficial location makes it easy
to harvest, and it can provide for multiple grafts. Despite of its wide use for revascularization, the long-term
patency of the saphenous vein graft is limited, with an occlusion rate of 10 to 20% in the first year and almost
50% after 10 years. Graft failure is often due to thrombosis, intimal hyperplasia and accelerated atherosclerosis.
In the later years a novel harvesting technique, the No-touch technique (NT), has been introduced. The SV
is harvested atraumatically from the leg with a pedicle of perivascular tissue with preserved vasa vasorum and
tunica adventitia. With the use of this technique, Souza et al. have found superior graft patency of NT SV
compared to conventional technique (CT) SV after 8.5 years with angiographic patency of 90 and 76%,
respectively.
The reasons for higher patency rate of NT SV is speculative and, indeed, many factors have been purposed;
atraumatic surgical technique, structural support of surrounding tissue, humoral factors of perivascular tissue
and intact vasa vasorum, and previous studies have found intact endothelium and medial vascular smooth
muscle cells. The aim of this study is to investigate the functional properties of the two types of vein grafts.
Methods
The study is a clinical analytical experimental study of humane SV segments obtained from CABG
operations at Aarhus University Hospital, Skejby. The tissue was transported to the experimental facilities at
Institute of Biomedicine, Aarhus University. Isometric- and pressure myography was used to investigate the
functional properties of SV. Myogenic responsiveness to noradrenalin, serotonin, L-NAME and
depolarization with high extracellular potassium concentration was examined at different transmural
pressures. Furthermore, the effects of distention and perivascular tissue were examined as well.
Results
There was a significantly larger contractile response to serotonin (p<0,0001), high extracellular potassium
concentration (p<0,0001) and noradrenaline (p<0,01) at a transmural pressure of 20 mmHg for NT SV
compared to CT SV. Furthermore, we found a significantly larger myogenic response at a transmural
pressure of 100 mmHg to serotonin (p<0,0001) and high extracellular potassium concentration (p<0,01) for
NT SV compared to CT SV. There was no significant difference by removing the perivascular tissue from
1
DTS årsmøde 2016
Leila Louise Benhassen
CT SV and NT SV or by avoiding the distention of CT SV. Moreover, the length-tension relationship for NT
SV was a classically inversed parabolic relation compared to a less physiological linear relation in the CT SV
group.
Discussion and conclusion
Our results show that NT SV exhibits significantly larger myogenic response compared to CT SV when
exposed to different vasoconstrictors. This observation argues for its viability, functionality and higher
sensitivity to stimuli in its surroundings, compared to CT SV, and is further supported by the classically
inversed parabolic length-tension relation. The significance of the perivascular tissue in these acute settings is
difficult to establish, but our data suggest that the perivascular tissue does not play a significant role acutely.
It is very likely that the effects of the perivascular tissue and the vasa vasorum may have long-term effects,
which cannot be demonstrated in an acute setting. Further studies are needed to examine NT SV and CT SV
in a long-term setting to investigate the effect the perivascular tissue could have on SV myogenic response and
reaction to different stimuli. However, this study, indeed support the use of conduit of higher viability and
functionality in CABG.
2