ECG Triggered Dual Source CT for Non-invasive Pre-operative Cardiac Imaging in Morbid Obese Patients

Coronary arterial disease is a risk factor for bariatric surgery and might be a predictor for later major adverse coronary events. Diagnosis of coronary arterial disease would thus be desirable for obese patients, however percutaneous angiography is an invasive procedure and associated with a certain morbidity in obese patients. In this study the investigators would like to assess whether dual source CT angiography can be used for diagnosis of coronary arterial disease in severely obese patients and which settings yield the best image quality.

Obesity is a major health problem in many countries and a major risk factor for cardiovascular disease. Extreme obesity can be treated with surgery, however these procedures are associated with a certain surgery-related morbidity which increases with comorbidities, in particular coronary diseases. Thus, preoperative cardiac risk assessment would be desirable, however percutaneous coronary angiography is an invasive procedure with problems and complications in obese patients. A non-invasive alternative would be coronary dual-.source CT angiography (CCTA), however little experience exists in the application of CCTA in morbid obese patients. This study would like to address the following issues: Comparison of image quality of coronary CT angiography using a dual source CT from obese patients using a special protocol (140 kV, 350 mAs) with images from historical controls from normal weight patients with a standard protocol (120 kV, 330 mAs). Prediction of major adverse coronary events. Patients with a coronary stenosis in CCTA will be followed for any major adverse coronary events (details see Outcomes) Is it possible to detect myocardial fat by a reduced CT density. Images from obese patients will be compared to historical controls from normal patients. Furthermore, is the myocardial CT density correlated with the BMI of obese patients? Optimisation of scan protocol. Increasing the scanning angle beyond the standard 90° will reduce the signal noise at the cost of temporal resolution. Various scanning angles with be tested for an optimal combination of signal noise and temporal resolution. Does the long QT-syndrome improve after bariatric surgery? It is assumed that the long QT-syndrome is a consequence of fattening of the myocardia. Is it possible to see a reduction of myocardial fattening and thus an improvement of the long QT-syndrome with CT during the follow-up after bariatric surgery?

obesity, dual source CT, coronary CT angiography, prognosis, bariatric surgery, gastric bypass surgery, coronary arterial disease, major adverse coronary event

tube voltage: 120 kV current time product: 350 mAs/rotation rotation: 90° (with two detectors in a 90° angle)

tube voltage: 140 kV current time product: 350 mAs/rotation rotation: 90° (with two detectors in a 90° angle)

tube voltage: 140 kV current time product: 350 mAs/rotation rotation: 180° (with two detectors in a 90° angle)

Coronary arteries (with at least 1 mm diameter at their origin) were segmented according to the 15-segment model of the American Heart Association (Austen 1975). Subjective image quality was judged for each coronary artery segment on a 4-point scale (Leschka 2007) : = excellent; = good, minor artifacts; = fair, moderate artifacts but still diagnostic; = non-diagnostic

Significant coronary artery stenosis was defined as more than 50% narrowing of luminal diameter. Stenosis assessment was performed by a radiologist not involved in image quality assessment.

Image noise was determined as the standard deviation of the attenuation value in a region of 1 sq cm that was placed in the ascending aorta. The average of the attenuation in the left and right coronary artery were used for further calculations.

Vessel contrast was calculated as the difference in the mean attenuation (in Hounsfield units) between the contrast-enhanced vessel lumen and the mean attenuation in the adjacent perivascular tissue. Attenuations were measured in a region in the proximal segment of the right coronary artery and in the left main artery, and were defined as large as possible, whereas avoiding calcifications and plaques. CNR was calculated as vessel contrast divided by image noise (Husmann 2006, Lembcke 2004).

Any of the following events: death non fatal myocardial infarction late revascularization with percutaneous coronary intervention coronary artery bypass grafting

Inclusion Criteria: morbid obesity (BMI >35 kg/m²) intention to undergo bariatric surgery increased risk for coronary artery disease (based on PROCAM score) Exclusion Criteria: kidney insufficiency (serum creatinine >100 µmol/l, creatinine clearance <50 ml/min) allergy to iodine containing contrast agents hyperthyroidism metformin medication pregnancy

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