SAMPLE IMAGES AND SIGNIFICANCE OF RESULTSCAUTION: The discussion which follows is general in nature. The information provided herein should not be used to diagnose individual cases. Every case is unique and only a doctor is qualified to diagnose and prescribe treatment. Furthermore, it's important to realize that no test in medicine should be viewed in isolation. The patient obtains the greatest benefit when test results are place in the context of an overall medical profile, and typically, it is the patient's personal physician who is best able to do this.
A negative scan is the best possible test result. It means that no calcium was found in the coronary arteries. Accordingly, it is highly unlikely that the patient has a significant (greater than 50%) coronary artery narrowing. While a negative test result does not guarantee that the patient will never experience any cardiac problems, it should prove greatly comforting that advanced atherosclerotic plaque is not yet present. Patients with negative scans should, of course, understand that this excellent test result does not provide a license for irresponsible behavior with respect to diet, exercise, smoking, weight, blood pressure and cholesterol control, etc. Adopting and/or maintaining excellent health habits increases the likelihood that the coronary arteries will remain "clean" for as long as possible. Small amounts of calcified plaque have been found in the coronary arteries, which means that the disease process has begun. This is not a reason to panic. Most individuals in Western Civilization will build some level of disease as they age. While it should always be the goal to stabilize or reverse this disease process, the reality is that slowing its progression and preventing it from reaching an excessive level is often sufficient to allow one to live a long and healthy life free of cardiac problems. Patients with this level of disease are advised to consult with their physician to develop a risk modification program to include adopting a low-fat diet, cardiovascular exercise, stress management and smoking cessation programs, and achieving optimal weight, blood pressure and cholesterol levels. In addition, aspirin therapy should be considered. Scores in this range indicate that mild atherosclerotic plaques are present. The likelihood that significant coronary disease is present is low. Active risk factor modification in these patients is critical to prevent the disease from progressing to a more advanced state. In addition to general public health guidelines for prevention of cardiovascular disease (adopting a low-fat diet, cardiovascular exercise, stress management and smoking cessation programs), strict adherence to National Cholesterol Education Program guidelines for cholesterol-lowering should be followed (total cholesterol should be reduced to less than 200 mg/dl and LDL cholesterol should be reduced to less than 130 mg/dl). In addition, aspirin therapy should be considered. Scores in this range indicate the likely presence of moderate non-obstructive coronary stenoses (narrowings). Very aggressive risk factor management in a physician-supervised program is strongly recommended. In addition to general public health guidelines for prevention of cardiovascular disease (adopting a low-fat diet, cardiovascular exercise, stress management and smoking cessation programs), strict adherence to National Cholesterol Education Program guidelines for cholesterol-lowering should be followed (total cholesterol should be reduced to less than 200 mg/dl and LDL cholesterol should be reduced to less than 130 mg/dl). In addition, aspirin therapy and exercise testing to rule out ischemia should be considered. Scores in this range indicate the presence of advanced atherosclerosis. There is a high likelihood of the presence of at least one coronary stenosis (narrowing) greater than 50%, and the patient is at a high risk of having an acute coronary event or developing symptomatic heart disease. In addition to general public health guidelines for prevention of cardiovascular disease (adopting a low-fat diet, cardiovascular exercise, stress management and smoking cessation programs), strict adherence to National Cholesterol Education Program guidelines for patients with established coronary artery disease should be followed (LDL cholesterol should be reduced to less than 100 mg/dl). In addition, stress testing with either nuclear imaging or echocardiography to rule out ischemia should be strongly considered, as should the institution of aspirin therapy. ACCURACYNumerous papers have been published in major medical journals attesting to the accuracy of Electron Beam CT Coronary Artery Scanning. Perhaps the most widely quoted statistic is the approximate 95% reliability of this procedure in ruling out obstructive coronary artery disease. This means that a negative scan (no coronary calcium) indicates with 95% reliability that the patient does not have a significant coronary artery obstruction. It should be noted that the older the patient, the higher the degree of reliability of a negative scan. With respect to positive scans (those finding coronary calcium), it has been demonstrated in numerous studies that (1) the amount of calcium correlates very highly with the overall volume of plaque and (2) the overall plaque volume correlates very highly with event risk (heart attacks, bypass surgeries, angioplasties). In other words, the higher the calcium score, the greater the risk of an event. One of the leading researchers in this field, Alan D. Guerci, M.D., Executive Vice President and Director of Research at St. Francis Hospital (Roslyn, N.Y.), was quoted as follows in The Wall Street Journal on September 27, 1996: "Our data indicate that the electron beam CT-derived coronary artery calcium score predicts fatal and nonfatal heart attacks, as well as the need for coronary bypass surgery and coronary (balloon) angioplasty, with unprecedented accuracy." IMAGE QUALITY INFORMATIONRecently, you may have heard other imaging centers claim that they can also perform coronary artery scans. However, many of these centers use spiral (a.k.a. helical) CT scanners that are not as accurate or reliable for cardiac purposes as the Electron Beam CT scanners used at Heart Check America affiliated centers. While in general, spiral CT is excellent imaging technology and very reputable firms manufacture the scanners these centers use, they are clearly inferior for cardiac imaging. The reason is quite simple. When you attempt to take pictures of a moving object such as the beating heart, the shutter speed of the camera becomes of paramount importance. If the camera is too slow, the images are very blurry. The acquisition time for Electron Beam CT images is 100 msec (1/10 second), whereas the acquisition time for spiral scanners typically ranges from 400 - 700 msec. The effect on the quality of images of various shutter speeds can be seen in the visual example below.
Above left: the apparatus configuration designed to approximate the speed of the heart muscle (approximately 25 mm/sec). Photo acquisition was triggered such that all pictures were taken at approximately the same position. Above right: a photograph taken at rest. Below: Photographs acquired with indicated shutter speeds
SAFETYDuring the course of a Coronary Artery Scan, the patient is exposed to radiation approximately equal to that received in an abdominal x-ray. Robert G. Gould, Professor in the Department of Radiology at the University of California San Francisco has concluded: "In summary, an Ultrafast CT scan for detection of coronary artery calcium is a safe procedure. It exposes a limited portion of the body to a small amount of radiation. No hazardous effect of x-rays has ever been demonstrated at the dose levels that result from this procedure." COMPARISON TO OTHER CARDIAC TESTSThere are numerous tests in addition to a Coronary Artery Scan which a physician can use to assess the condition of a patient's heart: an EKG, a stress test (in all its different varieties - regular treadmill, thallium, echo), a PET scan and angiography. When there are so many different ways to examine the heart, it's natural to wonder which is best. The relevant question however is which is the best test for the specific patient at the specific time. The Coronary Artery Scan is a screening test for the early detection of heart disease. It's capable of detecting the heart disease process years before any of the above mentioned tests. Typically, once it's established by a Coronary Artery Scan that an asymptomatic (no symptoms) individual is building plaque at a greater than expected rate, it would be appropriate to perform some form of exercise testing to study cardiac function. If a significant functional abnormality is revealed, then the patient will often proceed to angiography. Cholesterol tests merely measure the amount of cholesterol in your bloodstream. They tell you nothing about the physical condition of your coronary arteries. You can have low cholesterol and still have serious coronary artery disease, or you can have high cholesterol and no heart disease at all. | ||||||||||||||||||||
|
Copyright 2001© | ||||||||||||||||||||
