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Researchers Argue Imaging Has Role in Assessing Cardiovascular Disease Risk

Researchers Argue Imaging Has Role in Assessing Cardiovascular Disease Risk Orlando, Fla—Nearly two-thirds of individuals who experience out-of-hospital cardiac arrest in the United States had no prior symptoms nor realized that they had cardiovascular disease, underscoring the urgent need to improve heart risk assessment in asymptomatic patients. Currently, the standard for evaluating patients is the National Cholesterol Education Program's (NCEP’s) risk assessment, which predicts likelihood that an individual will have a myocardial infarction or die of a coronary event within 10 years. This risk assessment, based on decades-long epidemiological research from the Framingham Heart Study, uses a group of factors—age, sex, cholesterol levels, systolic blood pressure, smoking status, and use of hypertension medications—to calculate an individual's risk of a cardiac event. Using computed tomography to identify coronary artery calcification (arrowhead) can help physicians decide whether to proceed with treatment for asymptomatic patients. Asymptomatic patients at low risk of a cardiac event (a 10-year risk of less than 10%) are given pats on their backs by their physicians and told to keep up the good work. Patients at high risk (a 10-year risk greater than 20%) are aggressively treated with medications and counseled to adopt appropriate lifestyle interventions to improve those risk factors that are modifiable. The conundrum facing physicians is what to do with patients at intermediate risk. For some physicians, the answer is found in further risk exploration through standard or nuclear stress testing. Also being considered is imaging, using computed tomography (CT), ultrasound, magnetic resonance, and positron emission tomography to augment risk prediction and disease detection. At the forefront of these imaging tools is CT scanning of coronary arteries for calcium deposits. “When you are measuring risk factors, you are measuring atherosclerotic risk,” said Allen J. Taylor, MD, codirector of noninvasive imaging for the cardiology division at Washington Hospital Center in Washington, DC. “Why just predict it, why not measure it?” Interest is growing in the use of CT imaging for improved assessment of cardiovascular risk to allow timely intervention. According to Taylor, the science supporting the use of calcium measurement has improved greatly in the last few years. Such improvement has moved the discipline beyond the early days of coronary imaging, when stand-alone facilities offered full-body CT scans that produced calcium scores (usually stated as Agatston scores) that physicians could not interpret. While many physicians remain hesitant to use the technology, “we know very confidently, the approach works,” said Taylor, who chaired a session at the scientific meeting of the American College of Cardiology (ACC), held here in March, on where imaging fits in the arsenal of tools available to physicians for assessing cardiovascular disease risk. A scientific statement on cardiovascular imaging and intervention issued in 2006 by the American Heart Association (AHA) suggested that it “may be reasonable” to use CT to measure the atherosclerosis burden in asymptomatic patients to refine risk prediction and select those for more aggressive use of lipid-lowering therapies (Budoff MJ et al. Circulation. 2006;114[16]:1761-1791). Results from the Heinz Nixdorf Recall Study, presented by German researchers during a late-breaking clinical trials session of the ACC meeting, provide further support of CT imaging to assess cardiovascular risk in asymptomatic patients. The study enrolled 4487 randomly selected individuals (aged 45-75 years; 52% were women) without known coronary disease who were followed up for an average of 5 years. Of the 4137 individuals who completed the trial, 64 had nonfatal myocardial infarctions (30% women) and 29 had a coronary death (31% women). The investigators said that when establishing coronary calcium scores using electron-beam CT, the relative risk of a nonfatal myocardial infarction or coronary death among trial participants scoring in the highest quartile (with an Agatston score exceeding 239.2) was 3.16 for women and 11.09 for men compared with those in the lowest quartile (with an Agatston score of 4.4 or less). The researchers also demonstrated that CT imaging did a better job than NCEP criteria in assessing risk. For trial participants considered to be at intermediate risk based on the NCEP assessment protocol, CT imaging of their coronary arteries showed that 14% should be reclassified as high risk and 60% should be reclassified as low risk. Some doubt However, some experts are not convinced that imaging will improve risk assessment, noting that there are no published trials showing that treatment strategies based on the results of imaging decrease cardiovascular morbidity or mortality. (The goal of imaging or any other risk evaluation strategy remains assessment of modifiable factors that can be targeted for intervention, such as hypertension or hypercholesterolemia.) Skeptics also note that the test involves exposure to radiation (equivalent to the amount one gets as normal background radiation living in the United States for 3 or 4 months). Rita F. Redberg, MD, professor of clinical medicine and director of women's cardiovascular services at the University of California, San Francisco Medical Center, does not see any benefit in determining coronary calcium scores in asymptomatic patients. “These are people who are perfectly well to start with, but once they get a coronary calcium score, it can lead to a cascade of testing,” Redberg said. “So let's say you find an obstruction of a coronary artery, you give the patient a stent—which does not prevent heart attack or make them live longer—a stent alleviates symptoms, but these patients do not have symptoms to begin with.” Some could argue that patients want to know their calcium score for peace of mind or to signal that they need lifestyle modification. But the evidence is scant that showing a picture to patients of progressing heart disease will induce them to make such lifestyle changes or improve their adherence to medications, said James H. Stein, MD, professor of medicine at the University of Wisconsin School of Medicine in Madison. “For some patients, they have to interpret the picture as a threat to them before they make lifestyle changes,” said Stein. Taylor thinks using images to convince patients to alter their lives misses the point. Expecting a test result to change behavior is overreaching because patient behavior is “incredibly recalcitrant to change,” he said. Instead, he added, it is much easier to use imaging guidelines to change the behavior of physicians responsible for enacting good medical decisions. Coverage lacking Another barrier to increased use of coronary imaging is a lack of data regarding its cost effectiveness. In the absence of evidence of improved outcomes in patients who have undergone coronary CT scanning, insurers are hesitant to pay for the test—a test that may lead to patients being prescribed potentially expensive lifelong medication regimens—so that patients themselves must pay for imaging that can cost $500. “Insurers will pay $2000 for someone to have a colonoscopy, but colon cancer is far less prevalent than heart disease,” Taylor said. On the other hand, Taylor added, life insurance companies appear to be starting to require the test; the companies are adjusting their premiums to reflect lifetime risk of events emerging from subclinical cardiovascular disease, although patients who adhere to treatment may receive a discount, he said. Being labeled with subclinical atherosclerosis based on coronary imaging could lead to problems with insurers, but insurers should view it as analogous to measuring bone density for osteoporosis, said Roger S. Blumenthal, MD, director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease in Baltimore and a coauthor of the AHA imaging guidelines. “We do bone density absorptiometry to pick up those who should get pharmacological therapy; the same principles could hold for atherosclerosis imaging.” Ncep percentages questioned Proponents of coronary imaging are also concerned with the whole premise of using the NCEP assessment tool to assign high, intermediate, and low risk levels for their patients. They note the risk assessment only offers a 10-year event horizon, while patients and their physicians really should be concerned about lifetime risk. “Intermediate risk is artificially based on a 10-year prediction,” Stein said. “The more you image, the more you find that people are not at intermediate risk; it is not about deciding who needs treatment as it is about when to start.” Blumenthal would also prefer to see the definition of 10-year intermediate risk, as defined by NCEP, changed to include those with as little as a 6% risk, thus making certain vulnerable populations eligible for imaging. “If you leave the threshold at 10%, you potentially miss a good number of people with family heart disease who may have heart disease but who do not qualify to undergo imaging,” Blumenthal said. “And for women, about 90% who are less than age 70 will not get to that 10% risk level. So if you follow the [imaging] guidelines to test for subclinical atherosclerosis, you will not utilize it in these women when you have an opportunity to offer treatment before they actually have cardiovascular disease.” Imaging proponents have come up with an Internet-based risk assessment tool that combines Agatston scoring and elements of NCEP risk assessment numbers. This tool uses information gathered through the Multi-Ethnic Study of Atherosclerosis (MESA) trial, which created a database of average coronary artery calcium levels, based on age, gender, and race or ethnicity, by imaging 6110 individuals free of clinical cardiovascular disease (McClelland RL et al. Circulation. 2006;113[1]:30-37). Physicians and individuals can log onto the MESA site (http://www.mesa-nhlbi.org), enter Agatston scores along with NCEP numbers, and get “arterial ages” (such as a 50-year-old man having arteries similar to a 74-year-old man). “It is a communication tool that puts risk in the form of chronological age so that people understand that their level of risk is the same as someone of that age,” Stein said. Taylor said the ACC is currently revising its guidelines on testing in prevention, which should, in part, address coronary calcium scoring. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA American Medical Association

Researchers Argue Imaging Has Role in Assessing Cardiovascular Disease Risk

Mitka, Mike
JAMA , Volume 301 (19) – May 20, 2009
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Publisher
American Medical Association
Copyright
Copyright © 2009 American Medical Association. All Rights Reserved.
ISSN
0098-7484
eISSN
1538-3598
DOI
10.1001/jama.2009.670
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Abstract

Orlando, Fla—Nearly two-thirds of individuals who experience out-of-hospital cardiac arrest in the United States had no prior symptoms nor realized that they had cardiovascular disease, underscoring the urgent need to improve heart risk assessment in asymptomatic patients. Currently, the standard for evaluating patients is the National Cholesterol Education Program's (NCEP’s) risk assessment, which predicts likelihood that an individual will have a myocardial infarction or die of a coronary event within 10 years. This risk assessment, based on decades-long epidemiological research from the Framingham Heart Study, uses a group of factors—age, sex, cholesterol levels, systolic blood pressure, smoking status, and use of hypertension medications—to calculate an individual's risk of a cardiac event. Using computed tomography to identify coronary artery calcification (arrowhead) can help physicians decide whether to proceed with treatment for asymptomatic patients. Asymptomatic patients at low risk of a cardiac event (a 10-year risk of less than 10%) are given pats on their backs by their physicians and told to keep up the good work. Patients at high risk (a 10-year risk greater than 20%) are aggressively treated with medications and counseled to adopt appropriate lifestyle interventions to improve those risk factors that are modifiable. The conundrum facing physicians is what to do with patients at intermediate risk. For some physicians, the answer is found in further risk exploration through standard or nuclear stress testing. Also being considered is imaging, using computed tomography (CT), ultrasound, magnetic resonance, and positron emission tomography to augment risk prediction and disease detection. At the forefront of these imaging tools is CT scanning of coronary arteries for calcium deposits. “When you are measuring risk factors, you are measuring atherosclerotic risk,” said Allen J. Taylor, MD, codirector of noninvasive imaging for the cardiology division at Washington Hospital Center in Washington, DC. “Why just predict it, why not measure it?” Interest is growing in the use of CT imaging for improved assessment of cardiovascular risk to allow timely intervention. According to Taylor, the science supporting the use of calcium measurement has improved greatly in the last few years. Such improvement has moved the discipline beyond the early days of coronary imaging, when stand-alone facilities offered full-body CT scans that produced calcium scores (usually stated as Agatston scores) that physicians could not interpret. While many physicians remain hesitant to use the technology, “we know very confidently, the approach works,” said Taylor, who chaired a session at the scientific meeting of the American College of Cardiology (ACC), held here in March, on where imaging fits in the arsenal of tools available to physicians for assessing cardiovascular disease risk. A scientific statement on cardiovascular imaging and intervention issued in 2006 by the American Heart Association (AHA) suggested that it “may be reasonable” to use CT to measure the atherosclerosis burden in asymptomatic patients to refine risk prediction and select those for more aggressive use of lipid-lowering therapies (Budoff MJ et al. Circulation. 2006;114[16]:1761-1791). Results from the Heinz Nixdorf Recall Study, presented by German researchers during a late-breaking clinical trials session of the ACC meeting, provide further support of CT imaging to assess cardiovascular risk in asymptomatic patients. The study enrolled 4487 randomly selected individuals (aged 45-75 years; 52% were women) without known coronary disease who were followed up for an average of 5 years. Of the 4137 individuals who completed the trial, 64 had nonfatal myocardial infarctions (30% women) and 29 had a coronary death (31% women). The investigators said that when establishing coronary calcium scores using electron-beam CT, the relative risk of a nonfatal myocardial infarction or coronary death among trial participants scoring in the highest quartile (with an Agatston score exceeding 239.2) was 3.16 for women and 11.09 for men compared with those in the lowest quartile (with an Agatston score of 4.4 or less). The researchers also demonstrated that CT imaging did a better job than NCEP criteria in assessing risk. For trial participants considered to be at intermediate risk based on the NCEP assessment protocol, CT imaging of their coronary arteries showed that 14% should be reclassified as high risk and 60% should be reclassified as low risk. Some doubt However, some experts are not convinced that imaging will improve risk assessment, noting that there are no published trials showing that treatment strategies based on the results of imaging decrease cardiovascular morbidity or mortality. (The goal of imaging or any other risk evaluation strategy remains assessment of modifiable factors that can be targeted for intervention, such as hypertension or hypercholesterolemia.) Skeptics also note that the test involves exposure to radiation (equivalent to the amount one gets as normal background radiation living in the United States for 3 or 4 months). Rita F. Redberg, MD, professor of clinical medicine and director of women's cardiovascular services at the University of California, San Francisco Medical Center, does not see any benefit in determining coronary calcium scores in asymptomatic patients. “These are people who are perfectly well to start with, but once they get a coronary calcium score, it can lead to a cascade of testing,” Redberg said. “So let's say you find an obstruction of a coronary artery, you give the patient a stent—which does not prevent heart attack or make them live longer—a stent alleviates symptoms, but these patients do not have symptoms to begin with.” Some could argue that patients want to know their calcium score for peace of mind or to signal that they need lifestyle modification. But the evidence is scant that showing a picture to patients of progressing heart disease will induce them to make such lifestyle changes or improve their adherence to medications, said James H. Stein, MD, professor of medicine at the University of Wisconsin School of Medicine in Madison. “For some patients, they have to interpret the picture as a threat to them before they make lifestyle changes,” said Stein. Taylor thinks using images to convince patients to alter their lives misses the point. Expecting a test result to change behavior is overreaching because patient behavior is “incredibly recalcitrant to change,” he said. Instead, he added, it is much easier to use imaging guidelines to change the behavior of physicians responsible for enacting good medical decisions. Coverage lacking Another barrier to increased use of coronary imaging is a lack of data regarding its cost effectiveness. In the absence of evidence of improved outcomes in patients who have undergone coronary CT scanning, insurers are hesitant to pay for the test—a test that may lead to patients being prescribed potentially expensive lifelong medication regimens—so that patients themselves must pay for imaging that can cost $500. “Insurers will pay $2000 for someone to have a colonoscopy, but colon cancer is far less prevalent than heart disease,” Taylor said. On the other hand, Taylor added, life insurance companies appear to be starting to require the test; the companies are adjusting their premiums to reflect lifetime risk of events emerging from subclinical cardiovascular disease, although patients who adhere to treatment may receive a discount, he said. Being labeled with subclinical atherosclerosis based on coronary imaging could lead to problems with insurers, but insurers should view it as analogous to measuring bone density for osteoporosis, said Roger S. Blumenthal, MD, director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease in Baltimore and a coauthor of the AHA imaging guidelines. “We do bone density absorptiometry to pick up those who should get pharmacological therapy; the same principles could hold for atherosclerosis imaging.” Ncep percentages questioned Proponents of coronary imaging are also concerned with the whole premise of using the NCEP assessment tool to assign high, intermediate, and low risk levels for their patients. They note the risk assessment only offers a 10-year event horizon, while patients and their physicians really should be concerned about lifetime risk. “Intermediate risk is artificially based on a 10-year prediction,” Stein said. “The more you image, the more you find that people are not at intermediate risk; it is not about deciding who needs treatment as it is about when to start.” Blumenthal would also prefer to see the definition of 10-year intermediate risk, as defined by NCEP, changed to include those with as little as a 6% risk, thus making certain vulnerable populations eligible for imaging. “If you leave the threshold at 10%, you potentially miss a good number of people with family heart disease who may have heart disease but who do not qualify to undergo imaging,” Blumenthal said. “And for women, about 90% who are less than age 70 will not get to that 10% risk level. So if you follow the [imaging] guidelines to test for subclinical atherosclerosis, you will not utilize it in these women when you have an opportunity to offer treatment before they actually have cardiovascular disease.” Imaging proponents have come up with an Internet-based risk assessment tool that combines Agatston scoring and elements of NCEP risk assessment numbers. This tool uses information gathered through the Multi-Ethnic Study of Atherosclerosis (MESA) trial, which created a database of average coronary artery calcium levels, based on age, gender, and race or ethnicity, by imaging 6110 individuals free of clinical cardiovascular disease (McClelland RL et al. Circulation. 2006;113[1]:30-37). Physicians and individuals can log onto the MESA site (http://www.mesa-nhlbi.org), enter Agatston scores along with NCEP numbers, and get “arterial ages” (such as a 50-year-old man having arteries similar to a 74-year-old man). “It is a communication tool that puts risk in the form of chronological age so that people understand that their level of risk is the same as someone of that age,” Stein said. Taylor said the ACC is currently revising its guidelines on testing in prevention, which should, in part, address coronary calcium scoring.

Journal

JAMA – American Medical Association

Published: May 20, 2009

Keywords: cardiovascular disease risk factors,diagnostic imaging

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