Intraoperative detection of intimal lipid in the radial artery predicts degree of postoperative spasm.

BACKGROUND: The radial artery's (RA) tendency to spasm when used as a bypass graft may relate to features of the RA itself. We imaged RA conduits before and after CABG in order to characterize intimal abnormalities that might relate to the risk of spasm. METHODS: RA conduits from thirty-two CABG patients were imaged intraoperatively using catheter-based optical coherence tomography (OCT) and again on day 5 using 64-channel MDCT angiography. The change in luminal diameter between timepoints was measured in the proximal, mid and distal RA. "Spasm" was defined as focal or diffuse luminal narrowing to a diameter less than the target coronary. Lipid content in the RA was quantified by the degree of light attenuation on the OCT image. RESULTS: Postoperative spasm was diagnosed in 18 of 32 (56%) RA grafts with the distal RA showing the most severe change versus the mid and proximal portions (-24.1+/-43.2% vs. -15.3+/-40.7%, -9.0+/-42.5% change in diameter respectively, p<0.01). The degree of attenuation of the OCT signal produced by the RA was strongly correlated with % diameter change (R=0.64, p=0.0005) and was significantly more pronounced in grafts with spasm versus no spasm (-1.97+/-0.61mm(-1) vs. -0.81+/-0.57mm(-1), p<0.0001). Histology confirmed lipid deposits in areas of RA with strong attenuation. CONCLUSIONS: RA conduits otherwise considered acceptable for bypass grafting were often found by OCT imaging to have a substantial amount of lipid, which in turn strongly relates to the risk of postoperative spasm. Screening conduits based on characteristics of intimal quality may improve results following RA grafting.

Optical coherence tomography imaging as a quality assurance tool for evaluating endoscopic harvest of the radial artery.

BACKGROUND: Concerns about intimal disruption and spasm have limited enthusiasm for endoscopic radial artery harvest (ERAH), although the risk of these problems after this procedure remains uncertain. Radial artery conduits were screened intraoperatively before and after ERAH vs open harvest using catheter-based high-resolution optical coherence tomography (OCT) imaging. METHODS: Twenty-four cadavers and 60 coronary artery bypass graft (CABG) patients scheduled to receive a RA graft underwent OCT imaging before (in situ) and after (ex vivo) open harvest or ERAH. Spasm was quantified by the percentage change in luminal volume between images. Intimal disruption was classified as minor or severe depending on whether the defect was confined to branch ostia or involved the luminal surface. Histology was used to confirm OCT findings. RESULTS: Luminal volume significantly declined after harvest in all RAs from CABG patients, but there was no difference between groups: -43% +/- 29% vs -35% +/- 38% change after ERAH (n = 21) vs open harvest (n = 39; p = 0.342). Significantly more intimal injury was noted after ERAH vs open harvest (34/41 vs 9/43, intimal tears/total evaluated RAs, p < 0.0001). Most intimal injury was minor: only 2 tears involved the luminal surface of the RA (both after ERAH). Serial imaging in cadavers revealed that 86% of ostial tears occur in ERAH during the initial blunt dissection step using the endoscope. CONCLUSIONS: Although branch injury is a pitfall of ERAH, OCT imaging documented that the quality of RA procured is acceptable and comparable with open harvest. Catheter-based OCT provides an important quality assurance tool for RA harvest.

Strategies to reduce intraluminal clot formation in endoscopically harvested saphenous veins.

OBJECTIVE: Residual clot strands within the excised saphenous vein are an increasingly recognized sequela of endoscopic vein harvest. We hypothesized that endoscopic visualization facilitated by sealed carbon dioxide insufflation causes stagnation of blood within the saphenous vein. In the absence of prior heparin administration, this stasis provokes clot formation. METHODS: Forty consecutive patients having coronary artery bypass grafting underwent endoscopic vein harvest using sealed (Guidant VasoView, n = 30; Guidant Corp, Minneapolis, Minn) or open (Datascope ClearGlide, n = 10; Datascope Corp, Montvale, NJ) carbon dioxide insufflation followed by ex vivo assessment of intraluminal saphenous vein clot via optical coherence tomography. In the sealed carbon dioxide insufflation groups, clot formation was compared with (preheparinized, n = 20) and without (control, n = 10) heparin administration before endoscopic vein harvest, either at a fixed dose or titrated to an activated clotting time greater than 300 seconds. Risk factors for clot formation were assessed. RESULTS: Residual saphenous vein clot was a universal finding in control veins (sealed carbon dioxide insufflation endoscopic vein harvest without preheparinization). At either dose used, heparin given before endoscopic vein harvest significantly decreased saphenous vein clot burden. A similar reduction in clot was observed when using open carbon dioxide insufflation endoscopic vein harvest without preheparinization. Intraoperative blood loss and blood product requirements were similar in all groups. Patient age and preoperative maximum amplitude of the thrombelastography tracing showed a linear correlation with saphenous vein clot volume. CONCLUSION: By enabling the quantification of this issue as never before possible, optical coherence tomography screening revealed that intraluminal saphenous vein clot is frequently found after endoscopic vein harvest. Systemic heparinization before harvest or an open carbon dioxide endoscopic vein harvest system are benign changes in practice that can significantly lessen this complication.