CT technology is evolving at a rapid pace, with introduction of multidetector row CT scanners (MDCT) and electrocardiographic (ECG) gating resulting in increasing numbers of heart scans CTCA (CT Coronary Angiography). CTCA provides a noninvasive alternative to conventional invasive coronary angiography (ICA), which is considered the gold standard in the investigation of coronary disease. There has been a gradual increase in the utilization of CTCA for primary assessment of low and intermediate risk patients. However concerns regarding radiation exposure and diagnostic accuracy, especially in the highrisk group, have prevented its widespread dissemination.

To achieve best possible temporal resolution (minimize cardiac motion artifacts) and spatial resolution (provide diagnostic accuracy) relatively high radiation exposure is required, as a result of its inverse relationship with image noise and resolution. However radiation (X-ray) is associated with increased risk of cancer in exposed patients and it is therefore essential to continually devise strategies to reduce radiation exposure whilst maintaining image quality.

A state-of-art CT scanner (Discovery CT750 HD, General Electric (GE) Healthcare), has been installed at Derriford hospital for further research on CTCA. It uses novel method of scanning, High Definition Computed Tomographic Coronary Angiography(HD-CTCA), analogous to high definition television) and image reconstruction (Adaptive Statistical Iterative Reconstruction ASIR)as opposed to conventional CT scanners using Filtered Back Projection (FBP)reconstruction. HD-CTCA enables acquisition of sharper images and ASIR offsets the resultant increase in radiation exposure. This is likely to result in images of higher diagnostic quality with an equivalent or slightly lower radiation exposure compared to present technology. Although initial results are encouraging, this needs further assessment before being applied to routine clinical practice. To assess this we have designed a study to perform HD-CTCA on 300 consecutive patients undergoing diagnostic ICA at Derriford hospital, directly comparing the accuracy of HD-CTCA to ICA (presently considered the gold standard).

Hypotheses:

There is no significant difference in the sensitivity and specificity of HD-CTCA for the detection of coronary artery stenosis of 50% or greater compared to conventional ICA.

Inclusion Criteria:

• Patients > 40 years of age.
• Suspected or known coronary artery disease
• Admitted for diagnostic ICA

Exclusion Criteria:

• Consent cannot be obtained
• Age <40 years
• New York Heart Association (NYHA) Functional Classification - class III or IV heart failure
• Emergency imaging required (not enough time to consider the trial)
• Allergy to iodinated contrast or previous contrast induced nephropathy
• Intolerance to betablockers
• Uncontrolled rhythm disturbances (not suitable for CTCA)
• Serum Creatinine >200 micro mol/L within two weeks prior to procedure or chronic renal failure on dialysis