Coronary CT Angiography

Coronary CT Angiography

1. Coronary CT Angiography Dr Awadhesh Kr Sharma LPS Institute of Cardiology Kanpur

2. Coronary CT angiography : N oninvasive The overall accuracy of 64-row CT angiography included a sensitivity of 87% to 99% and specificity of 93% to 96%. F or evaluating CAD - most useful in low- to intermediate-risk patients with angina or anginal equivalent. The negative predictive value of coronary CT angiography is uniformly high in studies, approaching 93% to 100 % . in other words, coronary CT angiography is an excellent modality for ruling out coronary disease .

3. CT Angiography The basic principle of CT technology is the use of ionizing radiation within a gantry rotating around the patient in which x-rays are detected on a detector array and converted through reconstruction algorithms to images.

4. MDCT Multidetector CT (MDCT) scanners produce images by rotating an x-ray tube around a circular gantry through which the patient advances on a moving table.

5. Indications: Evaluation of chest pain in patients at low to intermediate pretest probability of disease . Suspicion of coronary artery anomalies. Pulmonary vein evaluation . Evaluation of cardiac masses. Evaluation of pericardial disease . Assessment of anatomy in complex congenital heart disease. Pre surgical evaluation, particularly before redo open heart surgery . Assessing graft patency after prior bypass surgery. Evaluation of aortic disease. Evaluation of suspected pulmonary embolism.

6. CONTRAINDICATIONS: Absolute contraindications : Renal insufficiency. Given the potential for contrast nephropathy, patients with significant renal insufficiency (i.e., Cr > 1.6 mg/dL) should not undergo contrast-enhanced CT . Known history of anaphylactic contrast reactions . A prior anaphylactic response to contrast is generally felt to be an absolute contraindication to intravenous iodinated contrast administration at many institutions. Pregnancy Clinical instability Contrast enhanced imaging : Administration of iodinated contrast media

7. Relative contraindications Contrast (iodine) allergy. Patients with allergic reactions to contrast should be pretreated with diphenhydramine and steroids before contrast administration. Recent intravenous iodinated contrast administration. Patients who have received an intravenous dose of iodinated contrast should avoid contrast-enhanced CT scanning for 24 hours to reduce the risk of contrast nephropathy. Hyperthyroidism. Iodinated contrast is contraindicated in the setting of uncontrolled hyperthyroidism due to possible precipitation of thyrotoxicosis. Atrial fibrillation or any irregular heart rhythm , is a contraindication to coronary CT angiography due to image degradation from suboptimal ECG gating. Inability to breath hold for at least 10 seconds. Image quality will be significantly reduced due to respiratory motion artifact if the patient cannot comply with breath hold instructions. Morbid obesity Severe coronary calcium

8. SAFETY A. Radiation exposure : Radiation doses of cardiac CT scans vary greatly depending on the scan parameter settings, scan range (cranial-caudal length of the scan), gender (women receive more radiation due to breast tissue), and patient body habitus (obesity increases exposure). chest x-ray is 0.04 to 0.10 mSv, average annual background radiation 3 to 3.6 mSv. Invasive diagnostic coronary angiography 2.1 to 4 mSv. coronary CT angiography 4 to 11 mSv.

9. B. Contrast nephropathy : Iodinated contrast media can cause renal ischemia by reducing renal blood flow or increasing oxygen demand and may also have a direct toxic effect on tubular epithelial cells. If a contrast-enhanced CT study is necessary in patients with significant renal insufficiency, prophylactic measures should be taken saline hydration n-acetylcysteine use of low osmolar agents sodium bicarbonate infusion

10. BREATH HOLDING During the test, a breath hold of 15–20 s will need to be performed Before the scan, practicing breath holding helps.

11. ECG GATING First , the skin is cleaned. Up to 12 self-adhesive electrodes will be attached to select locations of the skin on the arms, legs and chest. Three ECG leads are attached to obtain an adequate ECG tracing for CT. A noise-free ECG signal is important to synchronize the ECG signal to the raw image data.

12. CLINICAL APPLICATIONS A. Coronary calcium scoring Coronary calcium is a surrogate marker for coronary atherosclerotic plaque. Coronary artery calcium score is directly proportional to the overall extent of atherosclerosis . Complete absence of coronary artery calcium makes the presence of significant coronary luminal obstruction highly unlikely and indicates a very low risk of future coronary events. Men , CKD, diabetics tend to have higher coronary calcium scores. Contrast is not necessary because calcium is readily identified secondary to its very high x-ray attenuation coefficient (high Hounsfield unit score).

13. The Agatston coronary artery calcium (CAC) score is the most frequently used scoring system . It is derived by measuring the area of each calcified coronary lesion and multiplying it by a coefficient of 1 to 4, depending on the maximum CT attenuation within that lesion. The CAC score can be classified into five groups: zero, no coronary calcification; 100, mild coronary calcification; > 100 to 399, moderate calcification; >400 to 999, severe calcification; > 1000, extensive calcification.

14. CORONARY ARTERY Coronary artery is a vasa vasorum that supplies the heart. The coronary artery arises just superior to the aortic valve and supply the heart The aortic valve has three cusps – left coronary (LC), right coronary (RC) posterior non-coronary (NC) cusps. 16

15. Originates from right coronary sinus of Valsalva Courses through the right AV groove between the right atrium and right ventricle to the inferior part of the septum 17 RIGHT CORONARY ARTERY

16. Right coronary artery Conus artery Sinu nodal artery Marginal artery Post. Descending IV artery Conus branch SINU NODAL BRANCH 18 BRANCHES OF RCA AV Nodal artery

17. Right coronary anatomy AO LA RCA CONUS BR RCA S A N 1 2 3 4 AM RCA 13

18. RCA AM AM 20

19. LEFT CORONARY ARTERY 18

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22. DOM I NA N CE Determined by the arrangement that which artery reaches the crux & supply posterior descending artery The right coronary artery is dominant in 85% cases. 8% cases - circumflex br of the left coronary artery 7% both rt & lt coronary artery supply posterior IVseptum & inferior surface of the left ventricle- codominance 21

23. 91 LIMITATIONS OF CARDIAC CT Extensive calcifications Stents : spatial resolution Heart rate: temporal resolution Radiation risk Small branches/ septal branches

24. Stent patency: Image artifact from metallic stents limits the application in patients with prior coronary stent procedures. Small stents are difficult to evaluate and prone to noninterpretability. However , 90% accuracy can be obtained in stents 3 mm or greater in diameter with the use of sharp kernel and wide display window. Quantitative assessment of within-stent contrast density may assist in the diagnosis.

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