Study results show laser imaging is an effective tool for improving cardiac surgery

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Cardiac researchers at Sunnybrook & Women’s Schulich Heart Centre have validated a novel Canadian-made diagnostic imaging technology that will for the first time provide cardiac surgeons with a clinical quality control tool for bypass grafts before they leave the operating room.

The technique is a simple angiography (a visualization of blood vessels used for diagnosing) that is done during surgery. The technique allows the surgeon to check the quality of the bypass graft (a surgical joining of arteries or veins) to ensure that it is functioning properly.

Since the ability of a graft to function properly after surgery is the major determinant of a patient’s survival and freedom from recurrent heart disease after bypass surgery, the joining of the vessels to create a graft must be as technically perfect as possible.

“The information from these angiograms will now provide surgeons with the opportunity to make any required changes to the graft that would have otherwise gone unrecognized and we can do this before the chest is closed up,” said Dr. Nimesh Desai, co-lead investigator of the study and Fellow in cardiac surgery at Sunnybrook and Women’s College Health Sciences Centre. “The outcome is a reduction in the likelihood of graft problems, which should translate to less complications after heart surgery, decreasing the need for additional heart surgeries for the patient, and potentially even improving the survival rate.”

One of the first in the world to use this technology in 2001, Sunnybrook & Women’s is the only centre in Canada to offer this level of quality assurance to their heart surgery patients. The study presents the initial use of the technique and provides strong evidence for its reliability, validating it as superior to any other existing technique for assuring the quality of the heart bypass operation.

“These findings represent a significant advancement in quality assurance of bypass surgery,” says Dr. Stephen Fremes, head of cardiovascular surgery at Sunnybrook & Women’s, lead investigator of the study, and one of the first cardiac surgeons to apply the technique worldwide. “Until now, there was no accurate way for surgeons to verify that the heart bypass was functioning well in the operating room. Verification of quality of heart bypass with this technique may represent a new standard of patient care.”

The SPY system, created by Canadian company Novadaq Technologies, is an angiography device consisting of an imaging head that transmits a laser light that can penetrate up to one to two millimeters of soft tissue, and also houses a mini video camera. The technique involves positioning the imaging head over the exposed heart and using the laser to activate a fluorescent green dye that is injected into the graft. The fluorescence shows illumination of the area as the dye passes through, providing images of the blood vessels on the heart (coronary arteries) and the heart bypass grafts that can be viewed in real time. The technique only takes approximately two minutes to perform per graft, and it shows excellent reliability and sensitivity in detecting technical errors in coronary bypass grafts.

A total of 120 patients were recruited in this pioneering study and the investigators found that 4.2 per cent of patients had significant graft problems requiring major revision or new graft construction. Other recent coronary bypass reports indicate post-operative graft closure rates to be as high as 12 per cent, and post-operative mortality in patients with unrecognized graft problems to be over nine per cent.

Traditionally, imaging techniques such as x-ray coronary angiography, thermal angiography, Doppler flow measurement, electromagnetic flow measurement and transit-time ultrasound flow measurement were attempted to study bypass grafts in the operating room but only with limited success.

The study is published in the October 18 issue of the Journal of the American College of Cardiology, and was presented earlier this year at the American College of Cardiology Scientific Sessions in Orlando, Florida.

Schulich Heart Centre at Sunnybrook and Women’s College Health Sciences Centre is one of Canada’s leading cardiac care centres with an international reputation as a leading-edge provider for the prevention, treatment and care of heart disease. Schulich Heart Centre delivers a full spectrum of in-hospital and ambulatory cardiovascular care, significantly improving the quality of life for patients with heart conditions in Canada.