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Original Investigation |

Pressure Control During Preparation of Saphenous Veins

Fan Dong Li, PhD1; Susan Eagle, MD2; Colleen Brophy, MD3; Kyle M. Hocking, MEng3; Michael Osgood, MD3; Padmini Komalavilas, PhD3; Joyce Cheung-Flynn, PhD3
[+] Author Affiliations
1General Hospital of Jinan Military District, Jinan, China
2Division of Cardiothoracic Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee
3Division of Vascular Surgery, Vanderbilt University Medical Center, Nashville, Tennessee
JAMA Surg. 2014;149(7):655-662. doi:10.1001/jamasurg.2013.5067.
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Published online

Importance  Long-term patency of human saphenous veins (HSVs) used as autologous conduits for coronary artery bypass grafting (CABG) procedures remains limited because of vein graft failure (VGF). Vein graft failure has been reported to be as high as 45% at 12 to 18 months after surgery and leads to additional surgery, myocardial infarction, recurrent angina, and death. Preparation of HSVs before implantation leads to conduit injury, which may promote VGF.

Objectives  To investigate whether pressure distension during vein graft preparation leads to endothelial injury and intimal thickening and whether limiting intraluminal pressure during pressure distension by using a pressure release valve (PRV) preserves endothelial function and prevents neointima thickening.

Design, Setting, and Participants  Segments of HSVs were collected in a university hospital from 13 patients undergoing CABG procedures immediately after harvest (unmanipulated [UM]), after pressure distension (after distension [AD]), and after typical intraoperative surgical graft preparation (after manipulation [AM]). Porcine saphenous veins (PSVs) from 7 healthy research animals were subjected to manual pressure distension with or without an in-line PRV that prevents pressures of 140 mm Hg or greater. Endothelial function of the HSVs and PSVs was determined in a muscle bath, endothelial integrity was assessed, and intimal thickening in PSVs was evaluated after 14 days in organ culture.

Main Outcomes and Measures  Endothelial function was measured in force, converted to stress, and defined as the percentage relaxation of maximal phenylephrine-induced contraction. Endothelial integrity was assessed by immunohistologic examination. Neointimal thickness was measured by histomorphometric analysis.

Results  Pressure distension of HSVs led to decreased mean (SEM) endothelial-dependent relaxation (5.3% [2.3%] for AD patients vs 13.7% [2.5%] for UM patients; P < .05) and denudation. In the AM group, the function of the conduits was further decreased (−3.2% [3.2%]; P < .05). Distension of the PSVs led to reduced endothelial-dependent relaxation (7.6% [4.4%] vs 61.9% [10.2%] in the control group; P < .05), denudation, and enhanced intimal thickening (15.0 [1.4] µm vs 2.2 [0.8] µm in the control group; P < .05). Distension with the PRV preserved endothelial-dependent relaxation (50.3% [9.6%]; P = .32 vs control), prevented denudation, and reduced intimal thickening (3.4 [0.8] µm; P = .56 vs controls) in PSVs.

Conclusions and Relevance  Use of a PRV during graft preparation limits intraluminal pressure generated by manual distension, preserves endothelial integrity, and reduces intimal hyperplasia. Integration of this simple device may contribute to improved long-term vein graft patency.

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Figure 1.
Impairment of Contractility and Vasorelaxation of Human Saphenous Vein (HSV) Graft by Intraoperative Manual Distension and Graft Preparation

HSVs were collected after harvest (unmanipulated [UM]), after pressure distension (after distension [AD]), and after typical intraoperative surgical graft preparation (after manipulation [AM]). Phenylephrine (PE)-induced contraction (A), endothelial-dependent relaxation (B), and endothelial-independent relaxation (C) were determined in the muscle bath. Error bars indicate SEM.

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Figure 2.
Distortion of Luminal Area and Disruption of Endothelial Integrity of Human Saphenous Veins by Intraoperative Manual Distension

Unmanipulated (A and C) and after-distension (B and D) segments were immunostained for CD31 (original magnification ×50 [A and B] and ×200 [C and D]). L indicates lumen; M, media.

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Figure 3.
Reduction of Intraluminal Pressure During Manual Distension of Human Saphenous Veins With a Pressure Release Valve (PRV)

Intraluminal pressure was measured by connecting the distal end of the conduits to a manometer during manual distension in the absence (manual) or presence of the PRV. Inset: Photograph of the PRV.

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Figure 4.
Preservation of Contractility and Vasorelaxation of Porcine Saphenous Veins With the Pressure Release Valve (PRV) During Manual Distension

The porcine saphenous veins were left undistended (control) or subjected to pressure distension in the absence (distended) or presence of the PRV. Phenylephrine (PE)-induced contraction (A), endothelial-dependent relaxation (B), and endothelial-independent relaxation (C) were determined in the muscle bath. Error bars indicate SEM.

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Figure 5.
Preservation of Endothelial Integrity and Prevention of Intimal Hyperplasia In Vitro in Porcine Saphenous Veins (PSVs) With a Pressure Release Valve (PRV) During Manual Distension

A, Immediately after distension, PSVs were fixed for endothelial nitric oxide synthase (eNOS) and CD31 immunostaining. B, Organ cultured PSVs were fixed for the Verhoeff-van Gieson stain (VVG) to measure intimal thickness. Arrowheads indicate areas of disruption. Error bars indicate SEM. Scale bar = 100 µm.

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