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CT Predicts Heart Attack More Accurately Than Framingham, Conventional Risk Factors - The St. Francis Heart Study, the largest long-term study of its kind, demonstrates that fast CT scanning of the coronary arteries predicts coronary events such as heart attack independently of and more accurately than conventional risk factors such as age, smoking, blood pressure and cholesterol, and C-reactive protein (CRP), a more recently identified risk factor.
The study, conducted by researchers at St. Francis Hospital, The Heart Center(R), used fast computed tomography (CT) scanning to measure the calcium scores of 4,903 apparently healthy patients and followed the patients for 4.3 years. Fast CT scanning shows the amount of calcification in the coronary arteries, which is related to the severity of underlying coronary artery disease.
The St. Francis Heart Study received expedited review and will be published in the July 5 edition of the Journal of the American College of Cardiology. A companion paper on the effect of atorvastatin (Lipitor®), vitamin C, and vitamin E on study participants with elevated calcium scores will be published in the same issue.
"As the largest, population-based study to date, the St. Francis Heart Study shows that CT scanning of coronary arteries can be used to refine the standard risk categories, known as the Framingham risk index," said Alan D. Guerci, M.D., lead study author and President and Chief Executive Officer of St. Francis Hospital, The Heart Center, in Roslyn, New York. "Our study creates a very strong argument for scanning all patients at intermediate risk according to the Framingham criteria."
Approximately one-third of Americans ages 40-70 are at intermediate risk for coronary artery disease, as defined by the Framingham risk index, which calculates a patient's risk for a heart attack or stroke in the next 10 years based on factors such as age, cholesterol, hypertension, smoking and diabetes.(1) The National Heart, Lung and Blood Institute has made available an online risk assessment tool which uses Framingham Heart Study data to estimate 10-year risk for heart attacks:
Heart disease is the leading cause of death for both men and women in the United States. More than 1.5 million heart attacks occur in the United States annually, resulting in up to 500,000 deaths each year. In up to 50 percent of all heart attacks, the heart attack itself is the first symptom of heart disease. Early detection and intervention is the single best way to improve the likelihood of effective treatment.
"Increasing the accuracy of risk stratification through the use of fast CT scanning provides a very direct benefit to patients. Many patients classified at intermediate risk with clear signs of underlying disease can get potentially life-saving treatment, while others with no signs of disease can be spared an unnecessary and expensive regimen of medications," Dr. Guerci added.
Study Design and Results
The St. Francis Heart Study compared the prognostic accuracy of electron beam computed tomography-derived coronary calcium scoring with that of standard coronary artery disease (CAD) risk factors and C-reactive protein (CRP) in apparently healthy adults.
Between July 1996 and March 1999, 4,903 asymptomatic men and women ages 50 to 70 underwent electron beam CT scanning of the coronary arteries. At 4.3 years, follow-up was available in 4,613, or 94 percent of participants. Of these, 119 had sustained at least one atherosclerotic cardiovascular disease event (ASCVD). End points included coronary death, nonfatal myocardial infarction (MI), surgical or percutaneous coronary revascularization procedures, non-hemorrhagic stroke and peripheral vascular surgery.
Subjects with ASCVD events had higher baseline coronary calcium scores than those without events. The coronary calcium score predicted CAD events independently of standard risk factors and CRP (p=0.004), was superior to the Framingham risk index in the prediction of events (p=0.0006) and enhanced stratification of those falling into the Framingham categories of low, intermediate and high risk (p<0.0001).
Subjects with coronary calcium scores above the 80th percentile for age and gender (n=1005) were invited to participate in a double-blind, placebo-controlled trial of atorvastatin and vitamins E and C. Study participants were randomized to atorvastatin 20 mg daily, vitamin C 1 g daily and vitamin E 1,000 U daily (n=490), versus placebo (n=515). All participants also received aspirin 81 mg daily.
Treatment reduced total cholesterol by 26.5 to 30.4 percent (p<0.0001), low-density lipoprotein cholesterol by 39.1 to 43.4 percent (p<0.0001) and triglycerides by 11.2 to 17.0 percent (p≤0.02). Treatment reduced ASCVD events by 28 to 45 percent (0.04< p <0.14). A higher dose of atorvastatin would probably have produced even greater reductions in events.
The study also showed that cholesterol reduction did not retard the rate of progression of the coronary calcium score. This means that fast CT scanning of the coronary arteries is not an effective method of monitoring the response to treatment.
About St. Francis Hospital
St. Francis Hospital, The Heart Center is New York State’s only specialty designated cardiac center and is one of the five busiest heart centers in the United States. A recognized leader in the diagnosis, treatment and prevention of cardiac disease, St. Francis Hospital is one of only eight hospitals in New York State with risk-adjusted mortality rates significantly below the statewide average for all cardiac surgery: valve replacement and coronary bypass.(3)
Physicians at St. Francis Hospital offer unparalleled experience in the most innovative medical and surgical techniques and non-invasive imaging, including cardiac magnetic resonance and nuclear imaging, three-dimensional echocardiography, catheter-based treatment of congenital heart defects, radiofrequency cardiac ablation, pacemaker and defibrillator implantation, and a broad array of coronary, carotid and peripheral arterial angioplasty.
A leader in cardiovascular care for more than 50 years, St. Francis Hospital is a member of Catholic Health Services of Long Island (CHS).
(1)Wilson PWF, D'Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of coronary heart disease using risk factor categories. Circulation 1998;97:1837-1847.
(2)National Institutes of Health, National Heart, Lung and Blood Institute Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III)
(3)New York State Department of Health RAMR for Valve and Valve/CABG 2000-2002
Please note that although these studies will be published in the July 5 issue of JACC, there is no embargo because they received expedited review and were made available on Cardiosource.
J Am Coll Cardiol, 1998; 32:673-679
Comparison of electron beam computed tomography scanning and conventional risk factor assessment for the prediction of angiographic coronary artery disease
Alan D. Guerci, MD, FACC*, Louise A. Spadaro, MD, FACC*, Ken J. Goodman, MD{dagger}, Alfonso Lledo-Perez, MD{dagger}, David Newstein, MS*, Gail Lerner, MS* and Yadon Arad, MD*
* Research Department, St. Francis Hospital, Roslyn, New York, USA {dagger} Department of Radiology, St. Francis Hospital, Roslyn, New York, USA
Manuscript received August 27, 1997; revised manuscript received April 22, 1998, accepted May 11, 1998.
Objective. To determine whether electron beam computed tomography (CT) adds to conventional risk factor assessment in the prediction of angiographic coronary artery disease.
Background. Electron beam CT scanning can be used to predict the severity of coronary atherosclerosis, but whether it does so independently of conventional risk factors is unclear.
Methods. Electron beam CT scans were performed and conventional risk factors were measured in 290 men and women undergoing coronary arteriography for clinical indications. The association of the electron beam CT-derived coronary artery calcium score and conventional risk factors with the presence and severity of angiographically defined coronary atherosclerosis was analyzed by logistic regression and receiver-operator characteristics analysis.
Results. Age, the ratio of total cholesterol to high-density lipoprotein (HDL) cholesterol and the coronary calcium score were significantly and independently associated with the presence of any coronary disease and obstructive coronary disease. In association with any coronary disease, odds ratios for age, the ratio of total cholesterol to HDL cholesterol and calcium score, highest quartile vs. lowest quartile, were 6.01 (95% confidence interval 2.87 to 12.56), 3.14 (1.56 to 6.31) and 94.08 (21.06 to 420.12), respectively. For obstructive coronary disease, highest quartile vs. lowest quartile, the respective odds ratios for age, the ratio of total cholesterol to HDL and calcium score were 3.86 (1.86 to 8.00), 4.11 (1.98 to 8.52) and 34.12 (12.67 to 91.86). Male gender was also significantly associated with any coronary disease (odds ratio 2.19, p = 0.04) and obstructive coronary disease (odds ratio 2.07, p = 0.04). Cigarette smoking was significantly associated with any coronary disease (odds ratio = 2.74, p = 0.004), and diabetes was significantly associated with obstructive disease (odds ratio 3.16, p = 0.01). After adjustment for the coronary calcium score and other risk factors, it was determined that triglycerides, family history and hypertension were not significantly associated with any disease state. A coronary calcium score ≥80 (Agatston method) was associated with an increased likelihood of any coronary disease regardless of the number of risk factors, and a coronary calcium score ≥170 was associated with an increased likelihood of obstructive coronary disease regardless of the number of risk factors (p < 0.001).
Conclusion. Electron beam CT scanning offers improved discrimination over conventional risk factors in the identification of persons with any angiographic coronary disease or angiographic obstructive coronary disease.
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