Guidance
2 The procedure
2.1 Indications
2.1.1 Coronary artery bypass grafting is one of the most common cardiac surgical interventions. In this procedure, a section of vessel from another part of the body is used to reroute (bypass) blood around a blocked coronary artery and improve blood flow to the heart. Early blockage of the graft and poor blood flow may be a significant cause of morbidity and mortality in patients who have undergone coronary artery bypass grafting.
2.1.2 Several techniques are used intraoperatively to assess graft patency. These include digital palpation, electromagnetic flow measurement, Doppler studies, and conventional and thermal coronary angiography techniques. A limitation with many of the imaging techniques is that they provide poor resolution and definition of the grafts.
2.2 Outline of the procedure
2.2.1 Intraoperative fluorescence angiography allows confirmation of the location of the coronary arteries and assessment of bypass graft function during coronary artery bypass procedures. The intraoperative fluorescence imaging system consists of a video camera and a laser diode that emits monochromatic light. The camera, guided by a range-detector diode, is positioned a safe distance above the heart. A small amount of indocyanine green (ICG) dye is then administered as a central venous injection. This dye fluoresces when illuminated using laser energy and the images are recorded digitally. Currently the technique is only semiquantitative, in that it permits assessment of graft flow as 'excellent', 'satisfactory' or 'poor' – it cannot provide an exact measure of graft flow. The penetrating depth of the laser beam is only around 1 mm, limiting the use of this technique to certain grafts. For more details, refer to the Sources of evidence section.
2.3 Efficacy
2.3.1 The evidence on efficacy is based on four case series studies, with three studies reporting on clinically relevant results. In one study, intraoperative graft patency was assessed in 200 patients: graft patency was confirmed in 192 patients (96%), and the additional information provided by the procedure resulted in graft revision of these eight patients. Similar results were reported in two other studies with 1.4% (4/290) to 3.7% (4/107) of grafts revised after the procedure. No other outcomes were reported. For more details, refer to the Sources of evidence section.
2.3.2 One Specialist Advisor considered there to be too little information available regarding efficacy.
2.4 Safety
2.4.1 Complications associated with this procedure appear to be uncommon. There were no reports of adverse events associated with the use of the ICG dye in evaluating the patency of coronary bypass grafts. Six additional papers were identified that described complications following the administration of ICG dye for indications other than coronary graft patency. Most of these were reports of patients developing anaphylactoid reactions, with an incidence ranging from 0.02% to 0.3%. For more details, refer to the Sources of evidence section.
2.4.2 One Specialist Advisor stated that anaphylactic/allergic reactions might occur very rarely as a result of this procedure.
Andrew Dillon
Chief Executive
October 2004