Diffuse Saphenous Vein Graft Spasm

Case Report. A 53-year-old man presented with a history of angina at rest, a small troponin rise and ischaemic inferior ECG changes. He had undergone aortocoronary bypass operation for triple vessel disease 3 years before this admission. The left internal mammary (LIMA) was implanted to the left anterior descending (LAD). Two segments of the saphenous vein were grafted to the first obtuse marginal (OM1) and the right coronary artery (RCA). Cardiac catheterisation from the right femoral artery demonstrated extensive atheromatous disease of the native vessels. Both the LIMA to LAD and the SVG to OM1 were patent. However, the SVG to the RCA showed an angiographic “string sign”¹ with diffuse narrowing and TIMI 1 flow (Figures 1A–1F). Five-hundred micrograms of glyceryl trinitrate (GTN) was selectively injected in the lumen of the graft. This resulted in TIMI 3 flow within the graft, but still impaired native vessel filling (Figures 2A and 2B). Then, high-dose intragraft diltiazem (5 mg over 1 minute) was selectively injected, resulting in an improvement of flow through the graft and good native vessel replenishment (Figure 2C). No percutaneous coronary intervention (PCI) was performed. The patient was discharged on oral long-acting nitrates and 360 mg of oral diltiazem daily, and has remained asymptomatic for over 1 year. Discussion. Native coronary artery spasm is a well known phenomenon.² Saphenous vein graft spasm post-coronary artery bypass graft (CABG) operation has also been previously described^3–5 and different pharmacological agents have been shown to be effective in preventing post-harvesting early graft spasm.⁶ The use of nitrate combined with a calcium channel blocker has been demonstrated to have a rapid onset and longer duration of action in the saphaneous vein grafts than other pharmacological agents.^7,8 In our case, the combined administration of the two drugs acutely improved the angiographic appearance of the graft and native vessel, while long-term use relieved angina, highlighting the important contribution of an increased graft vascular tone in the pathogenesis of patients’ symptoms. While we cannot totally exclude the fact that the spasm occurred at the level of the native vessel, we observed a “string sign” in the saphenous vein graft with very slow progression of the contrast agent, even after disengagement of the catheter (Figures 1C–1F). Minor contrast filling was present in the native bed, thus excluding distal occlusive spasm (Figures 1E–1F, arrows).² This phenomenon resolved almost totally after intragraft injection of nitrates and diltiazem, indicating preserved vascular reactivity of the graft, which has clearly dilated in Figure 2 compared to Figure 1. The observed “string sign” has been demonstrated in other conduits such as radial or internal mammary grafts, and has been linked to various causes, including spasm of the vessel.¹ Saphenous vein graft spasm, although very rare, may constitute one of the differential diagnoses in assessing a post-CABG patient presenting with angina.

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