Ontario Multidetector Computed Tomographic (MDCT) Coronary Angiography Study (OMCAS)

Inclusion Criteria: Group 1 * Valvular heart disease (mitral stenosis, mitral regurgitation, aortic stenosis or aortic insufficiency) or * Congenital heart disease (i.e. VSD, ASD, PDA) or * Cardiomyopathy OR Group 2 * Intermediate probability of coronary artery disease (probability of 10-90%) after clinical evaluation and traditional non-invasive testing Exclusion Criteria: * Age \< 18 years * Lack of consent * Renal Insufficiency (GFR \< 60 mL/min) * Allergy to contrast agent * Refractory angina requiring urgent/emergent coronary angiography (as per treating physician) * Pregnancy or breast feeding * Uncontrolled heart rate * Previous CABG or PCI/Stent * Chronic atrial fibrillation * History of acute myocardial infarction, as defined by a creatine kinase (CK) level greater than 2 times normal with a troponin level above 4. * Unable to perform 20 second breath-hold