CT coronary angiography
Cardiovascular diseases are the first cause of morbidity and mortality in developed countries. An early diagnosis with the lowest costs it was necessary, which led to the development of both imaging examination techniques as well as medical devices, focusing lately on computer tomography examination and on the cardiac magnetic resonance.
Examination of multislice CT angiography is an imaging, last generation, non-invasive method which highlights the coronary arteries. This was possible after the introduction of ECG gating, and the emergence of the “multislice” technology. The method reveals the anatomy of the coronary arteries and any coronary anomalies of origin, the presence and the degree of coronary stenosis, parietal calcifications (calcium score), bypass evaluation and patent stents, left ventricular function evaluation, cardiac malformations, and prosthetic valve function.
Studies made by various authors have shown that the method has 96% sensitivity, 74% specificity, 83% positive predictive value, but 94% negative predictive value.
CT coronary angiography is indicated in asymptomatic, cardiovascular, those with family history of coronary disease, in bypass study and stent patency, in patients with atypical symptoms or inconclusive stress test. Like any method of investigation have absolute contraindications and limitations: increased heart rate 70 beats / min, atrial fibrillation, pregnancy, massive parietal calcifications (calcium score greater than 1000), uncooperative patients who do not maintain apnea required by the examination or if allergy occurs to iodinated contrast agents.
A special role in the positive results it has the correct preparation of the patient for this examination: 24 hours before the examination are contraindicated coffee, beverages containing caffeine, black tea and energizing juices. The patient should not eat 4 hours before the examination is administered orally 32 mg Medrol 12 hours before the examination, repeated dose 2 hours before. Venous approach is also important because the iodine solution was injected at a rate greater than 5 ml / sec, 70-90 ml. Medical history is also important, the presence of stents or grafts involving choice examination protocol.
This is an indirect marker of coronary atherosclerotic load, coronary calcification is an early sign of coronary artery disease (calcium score with diagnostic value before the appearance of the first signs or symptoms of myocardial ischemia). Agatston score is calculated according to the extent and density of the lesions in relation to the CT area examined. It is determined by native CT scan, is a simple method, non-invasive, short-term and minimal radiation, useful in patients with intermediate risk of heart attack or death (1-20% risk by Framingham score). The method is not justified in patients at risk below 10%, does not evaluate soft plaques, does not distinguish stable and unstable plaques and is not proportional with the severity of stenosis.
The interpretation of the calcium score
0: no identifiable atherosclerotic plaques in present. Decreased risk of heart incidents in the next 2-5 years.
1-10: Presence of very early changes of coronary artery disease with minimal risk of developing cardiac incidents.
11-100: There are early changes of the coronary arteries, moderate risk of developing heart incidents in the next 2-5 years.
101-400: The presence of significant changes in coronary artery disease, the risk of developing medium to large cardiac incident in the next 2-5 years.
Over 401: The presence of advanced coronary artery disease changes with high risk of cardiac incidents. Major symptoms of significant coronary obstruction.
The negative value of calcium score is associated with an extremely low probability of stenosis (less than 1%), but is not excluded.
A very special indication of CT coronary angiography is in patients whom cannot be made that invasive classic coronary angiography or is uncertain.