||Rolling Oaks Radiology’s
At Rolling Oaks, we have been performing cardiac exams for many years and have special fellowship training in reading cardiac CTA studies. Our cardiac program consists of various diagnostic cardiac tests including, but not limited to, Calcium Scoring, CT Coronary Artery Angiography, Cardiac MRI, Nuclear Medicine Cardiac Studies i.e. Sestamibi Stress Study and MUGA scan, and Cardiac PET exams such as Rubidium Stress Test and PET viability scans.
One of the goals of cardiac testing is to help stratify patients thought to be at risk for symptomatic coronary artery disease specifically for short-term complications such as myocardial infarction (MI) or sudden cardiac death. The gold standard for determining coronary artery disease is cardiac testing using invasive coronary angiography by placing a catheter into an artery, usually the femoral artery in your groin, and directing the catheter into an artery feeding the heart (coronary artery). Even though this may be considered the “gold standard”, it is invasive and therefore associated with some potential complications. It also has some major limitations as it only evaluates the lumen, the opening, of the coronary artery for narrowing and does not evaluate the degree of plaque that may be inside the artery. Since many heart attacks (myocardial infarctions) or sudden cardiac death happen even in patients without significant narrowing of their coronary arteries, a test that only evaluates the lumen diameter, such as a conventionally angiogram, will not detect many patients at risk of future coronary events. The benefit of some other noninvasive studies such as a Calcium Score or Coronary CT Angiography (CCTA) is that it gives prognostic information about future coronary events even if the lumen of the vessel is not narrowed, as it evaluates the plaque buildup in the coronary arteries regardless of the degree of narrowing of the lumen.
There are many different tests available for diagnosing cardiac disease and the particular study you may need is based on multiple factors including your history, symptoms, and physical examination. Your physician and our radiologists will work together to provide you with the best test available to help answer the clinical question posed by your doctor. Some information about these individual tests are given below.
Calcium scoring and Coronary CT Angiography (CCTA) have different clinical indications. Calcium scoring is primarily used for risk assessment of patients without symptoms and can be used to predict future coronary events in these patients. Plaque may occur at a relatively young age and can even be seen in patients as young as their teens. As the plaques mature, they tend to calcify. Measuring the calcium score gives an idea of how much total plaque is present in the coronary arteries. While risk factors such as hypertension, elevated cholesterol level, and tobacco use all predispose a patient to future cardiac events, the addition of a calcium score gives independent cardiac risk information that is actually more predictive of future coronary events than the use of traditional risk factors.
Cardiac CTA (CCTA)
CCTA uses intravenous contrast material to provide direct visualization of the coronary lumen and also evaluates the entire wall of the coronary artery for calcified or non-calcified (soft) plaque. Using various techniques we are now able to keep the radiation dose as low as that for performing a nuclear medicine cardiac stress study (<10 mSv). CCTA has been shown to have good correlation with the “gold standard” of invasive conventional coronary angiography in many different studies.
A low and regular heart rate is necessary for optimal imaging and it may be necessary to administer beta-blockers to achieve an adequately low heart rate (preferably 60 beats per minute or less). We also administer nitroglycerine by spray or by a pill taken under the tongue to try and dilate the size of the coronary arteries making it easier to visualize. When the study is performed for both anatomy and function, we also evaluate the heart’s motion and determine the thickness of the walls and diameters of the chambers of the heart.
The following indications are appropriate indications for coronary CT angiography:
• Evaluation of chest pain in patients with intermediate pretest probability of Coronary Artery Disease and uninterpretable electrocardiogram (ECG) or inability to exercise
• Evaluation of chest pain in patients with uninterpretable or equivocal stress test (exercise, Nuclear Stress test, or stress echocardiogram)
• Evaluation of acute chest pain in patients with intermediate pretest probability of CAD and no ECG changes and serial enzymes negative
• Evaluation of coronary arteries in patients with new-onset heart failure
• Evaluation of suspected coronary anomalies
The majority of studies indicate that a negative CCTA can effectively rule out obstructive coronary artery disease. . In a 2008 meta-analysis of 64-slice CCTA, a sensitivity of greater than 98% and a negative predictive value (NPV) of close to 100% for patient-based detection of significant CAD was found. However the specificity has been lower than the sensitivity in most studies, and false-positive results are possible, particularly in patients with high calcium scores. The ACCURACY trial suggests that, compared with other noninvasive modalities such as stress echocardiography and stress nuclear testing, CCTA has comparable specificity but superior sensitivity and NPV.
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