الفهرس 
CT anatomy of the coronary arteriesOnly 14 pages are availabe for public view
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Abstract
Multislice CT is a recent development in the spiral CT. The MSCT scanners are equipped with multiple and thinner detector rows, and has a faster tube rotation speed creating two major advantages; high spatial resolution and short acquisition time that enable high-quality examinations. It is only with this immense increase in the data acquisition volume per unit time, that CT assessment of the coronary arteries has become possible.
Challenges in evaluating the coronary arteries at CT are the small size and tortuous courses of the vessels and their continuous movements being intimately related to the cardiac chambers. Controlled heart rate and good breath-holding help to reduce cardiac and respiratory motion artifacts respectively. Retrospective ECG gating and proper choice of the reconstruction window would significantly improve the examination quality.
To date, the central rationale of CT angiography has been the noninvasive detection and grading of coronary artery stenosis, assessment of coronary artery anomalies and follow up after coronary bypass surgery. Contraindications to CTCA include irregular heart beats (arrhythmias), contra-indications to iodinated contrast material including allergy, renal insufficiency and hyperthyroidism, contra-indications to radiation exposure; pregnancy, respiratory impairment and marked heart failure.
Atypical angina is chest pain or discomfort that lacks one of the characteristics of typical angina. It can arise from a variety of etiologies including cardiac and non-cardiac causes. Cardiac chest pain may be caused by either coronary artery disease (CAD) or non-CAD related etiologies. The latter includes ischemic syndromes in the absence of as well as non-ischemic cardiac pain.
MDCT plays an important role in the assessment of acute thoracic disease involving the great vessels such as pulmonary embolism and aortic dissection as well as non-cardiac causes of acute chest pain. CT based evaluation for significant coronary artery stenosis has been shown to decrease the number of unnecessary hospital admissions without reducing the rates of appropriate admissions by ruling out the absence of acute coronary syndrome.
The aim of this study was to evaluate the role of multi-detector row CT angiography in patients presenting with atypical chest pain and to detect its ability to exclude significant CAD and thus avoid unnecessary coronary angiograms in this groups of patients.
This study included 50 patients, presenting with atypical chest pain showing initial negative ECG and troponin enzyme. Out of the 50 cases 9 (18%) patients were normal, 18 (32%) cases showed non-significant CAD and 19 (38%) cases showed significant coronary artery disease and 7 (14%) cases showed anomalous coronary arteries. Zero calcium score was detected in 16 cases (32%) including one case showing significant CAD. Calcium score below 100 in 20 cases (40%) and above 100 in 14 cases (28%).
Conventional angiography was considered the reference standard technique for 20 cases. Results of both modalities were compared on per-segment basis. MDCT coronary angiography compared to CCA as reference standard showed sensitivity, specificity, positive predictive value, negative predictive value & accuracy; 98%, 97.7%, 90.5%, 99.5, 97.7% respectively.
Heavy calcification of vessel walls is an important cause for both false positive and false negative CT results. Heavy calcification of a coronary segment leads to overestimation of the stenosis degree in the lesion. It was responsible for 3 false positive results and in overestimation of the stenosis in further 4 segments.
In conclusion, our results show that noninvasive 64-slice as well as dual source CT coronary angiography is a reliable technique to detect coronary stenoses in patients presenting with atypical chest pain and suggest that this noninvasive technique can now be considered an alternative to invasive diagnostic coronary angiography in this group of patients.
Recommended protocol for a case of atypical chest pain
Full history taking, clinical examination with special emphasis on risk factors for CAD, laboratory investigations including cardiac biomarkers, tests for diabetes and hyperlipidemia as well as resting electrocardiography.
Estimation of the patient’s probability of CAD using TIMI score.
-Patients with high probability of coronary artery disease including ischemic changes in resting ECG and positive troponin enzyme should undergo CCA.
-Patients with low probability of coronary artery disease should be investigated for other causes of chest pain such as GERD using manometeric study or Barium swallow, chest pathology using CT chest or plain x-ray or cholecystitis using abdominal US.
-Patients with intermediate probability of coronary artery disease including negative resting ECG and initial troponin enzyme should perform MDCT coronary angiography, and based on its results:
• Cases showing significant CAD should undergo CCA to confirm the significant lesion and for interventional purposes if possible.
• Cases showing non-significant CAD and anomalous coronary arteries are subjected to conservative treatment and follow up.
• Cases showing normal or nearly normal coronary arteries with other findings suggesting the cause of the chest pain as non CAD cardiac causes, pericardial, thoracic or large blood vessel disease will undergo further detailed investigations according to the pathology discovered.
• Cases which show completely normal study should be further evaluated for an alternative cause of chest pain.