Surgery for blocked arteries in the heart (coronary artery bypass grafting) can be accomplished using veins from the leg sewn onto the heart to provide an alternate path for blood flow, i.e. ‘bypassing’ the blockages. These veins themselves can block over time. This may result in part simply from the trauma from the surgery, in other words, by removing the vein from the leg and then sewing it to the heart.

Another mechanism may be the abnormal metabolic processes within the body responsible for the plaque build-up of the heart arteries in the first place – this may lead to the blockages of the veins used for bypass. In the present era of heart bypass surgery, this incidence of veins blocking remains high despite advances in blood thinners and cholesterol medications.

The SUPERIOR SVG study was designed to determine whether two new interventions may potentially reduce the incidence of blockages in the veins used for heart bypass surgery. One is a surgical technique significantly reducing the trauma associated with removing the leg vein prior to use as a bypass graft onto the heart. The second intervention is the use of a nutritional supplement before and after surgery which is composed of fish oils.

The study recruited sufficient patients to provide strong and relevant conclusions regarding both study questions. It will be highly applicable also because it will include approximately 1,550 patients from approximately 50 hospitals across many countries. We believe these techniques will result in significantly less vein blockages in patients one year after heart bypass surgery.

Primary Outcome:

Surgical Arm: Proportion of study SVGs which are totally (100%) occluded on cardiac CT angiography at one-year post-CABG and death due to cardiovascular or unknown causes.

Pharmacological Arm: Proportion of patients with greater than or equal to one graft (saphenous or arterial) totally (100%) occluded on cardiac CT angiography at one-year post-CABG and death due to cardiovascular or unknown causes, comparing the fish-oil to placebo groups.

The Principal Investigator of this study was Stephen Fremes, scientist, Sunnybrook Health Sciences Centre, Toronto.

Study Type

Interventional - Procedure

Study Design

Randomized, controlled 2×2 factorial

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Study Period




Heart & Stroke Foundation


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