| Summary: | The ultimate success of bypass surgery depends on the construction of a technically perfect bypass graft to an appropriate coronary vessel using a conduit which will remain durable for the lifetime of the patient. This thesis explores methods to improve coronary surgery by enhancing intraoperative imaging and conduit selection in the operating room.
It is known that technical errors in graft construction cause failure of up to 12% of coronary bypass grafts in the operating room. We performed investigations of a new technique of intraoperative fluorescence angiography using indocyanine green dye to determine graft patency. We developed optimal methods of obtaining images and preliminary investigations revealed the technique was highly reproducible. In a follow-up trial, we demonstrated that over 80% of technical errors which would otherwise have been missed were identifiable with indocyanine green angiography, while only 25% of these errors were identified by transit-time ultrasonic flow measurement, the current clinical standard. We also determine that coronary surgery with indocyanine green angiographic graft patency verification was associated with less perioperative myocardial injury than bypass surgery without graft patency assessment.
The long term graft patency of saphenous vein grafts is sub-optimal, with over 40% of such grafts totally occluded and a further 30% significantly diseased at ten years. We attempted to improve these outcomes by increasing the use of arterial grafts, which are less prone to intimal hyperplasia. In a multicentre clinical trial, we demonstrated a 40% relative risk reduction in graft occlusion at one year when radial arteries were used as bypass conduits versus saphenous veins. We identified that women and patients with small coronary vessels maximally benefited from radial artery bypass grafts. Conversely, in settings of less severe target vessel stenosis or concomitant peripheral vascular disease, saphenous veins performed as well as radial arteries.
We have demonstrated that high quality imaging to identify technical errors during the operation, increased use of radial artery grafts and careful consideration of individual patient and target vessel characteristics can all improve graft patency. Future studies will be aimed at identifying the role of intraoperative imaging and arterial grafting in improving long-term clinical outcomes.
|
|---|
