CHICAGO (EGMN) – New American College of Cardiology/American Heart Association guidelines on cardiovascular risk assessment in asymptomatic adults may be better remembered for the tests and procedures that received a thumbs-down rather than for those endorsed for routine use.
For example, genetic testing was among the newer, often glamorous tests that have captured intense public and physician interest, yet they were classified as class III – meaning they’re deemed not useful and may be harmful. In other words, don’t do them in people without symptoms of heart disease.
“Genetic testing is a sexy area right now, but we didn’t see it as being ready or as having shown added value,” Dr. Sidney C. Smith Jr. said in a press briefing on the new guidelines held during the annual scientific sessions of the American Heart Association.
Other tests that were rated class III included advanced lipid testing with measurement of apolipoproteins and particle size and density, MRI for the detection of arterial plaque, measurement of natriuretic peptide levels, and coronary CT angiography.
“You’ll hear a lot of discussion about the value of coronary CT angiography in people who come into the emergency department with chest pain, but that’s a very different population,” said Dr. Smith, a member of the risk assessment guideline writing committee and immediate past chair of the ACC/AHA task force on practice guidelines.
Stress echocardiography, measures of arterial stiffness, and assessment of flow-mediated dilation also received class III status, noted Dr. Smith, professor of medicine and director of the center for cardiovascular science and medicine at the University of North Carolina, Chapel Hill.
In his Ancel Keys Memorial Lecture delivered at the AHA conference, Dr. Philip Greenland, chair of the guideline writing committee, explained that new diagnostic tests have to clear a high bar: They must show evidence of added value beyond that provided by the Framingham Risk Score or another global cardiovascular risk score plus assessment of family history, which are the only class I recommendations in the new report, meaning they should be performed in all adults.
The family history is a new class I recommendation. A positive family history under the Framingham definition is a first-generation male relative with a cardiovascular event at age 50 or younger, or by age 60 or younger in a female relative.
The new guidelines state that a global cardiovascular risk score and family history are essential for everyone, preferably starting at age 20, and should be repeated every 5 years.
For a new risk marker to be considered as useful for risk prediction, it must be shown to be a statistically independent predictor after an accounting for established risk factors. Beyond that, it must also be shown to change predictive risk sufficiently to alter recommended therapy. And then it must be demonstrated that using the novel marker to sort patients and treat them accordingly would actually yield better clinical outcomes than if the marker had not been employed, explained Dr. Greenland, professor of medicine and preventive medicine at Northwestern University in Chicago.
“This is a big question for almost all of our biomarkers in cardiovascular medicine, where we can perhaps show improvement in prediction, but it’s not quite so clear we can show improvement in clinical outcomes,” he said. “Generally speaking, we haven’t seen much evidence of improvement of risk prediction with the new markers when you look at the whole picture. The one exception, I would say, is measurement of coronary artery calcium. I came to this as a major skeptic about coronary calcium, and only after seeing some data did I come to believe that coronary calcium might actually have clinical impact. But even with coronary calcium, I think we’re too early in the evaluation process to recommend routine use beyond standard risk measurement.”
Indeed, coronary artery calcium scoring gets a class IIa recommendation (meaning it’s reasonable for cardiovascular risk assessment) only in asymptomatic adults who are at intermediate risk, as defined by their global Framingham-type risk assessment, with an estimated 10%-20% risk of a cardiovascular event in the next 10 years. Coronary calcium scoring gets a lesser IIb rating (meaning it ‘may be considered appropriate’) in patients who are at low to intermediate risk, as defined by an estimated 6%-10% risk of an event over 10 years. In patients with less than a 6% 10-year risk, it gets a class III rating.
Investigators in MESA (Multi-Ethnic Study of Atherosclerosis) found that adding coronary artery calcium scores to standard cardiovascular risk factors improved risk discrimination from 77% to 82%, which the committee deemed clinically meaningful, Dr. Smith noted.
Measurement of C-reactive protein, another hot topic, is rated class III (no benefit) in asymptomatic adults who are defined as high-risk by the Adult Treatment Panel III standard of a greater than 20% 10-year risk. Similarly, CRP is class III in low-risk men younger than age 50 and in low-risk women younger than age 60.
However, CRP is beneficial in fine-tuning risk assessment in individuals who are at intermediate 10-year risk based upon their global assessment. CRP gets a class IIa recommendation as a guide to deciding on statin therapy in men aged 50 or older and in women aged 60 and older with an LDL cholesterol level of less than 130 mg/dL. It gets a class IIb recommendation in asymptomatic men and women aged 50 and 60 years, respectively, or younger.
Other tests that are rated class IIa or IIb under various circumstances in intermediate-risk people include ankle-brachial index testing for peripheral artery disease, a resting ECG in patients with hypertension or diabetes, conventional echocardiography in hypertensive patients, an exercise ECG before the start of a vigorous exercise program, carotid intima-media thickness measurement when performed by an expert operator, and measurement of hemoglobin A1c. Testing for microalbuminuria gets a class IIa recommendation in asymptomatic adults with diabetes or hypertension, and is class IIb for intermediate-risk adults without those comorbidities.
The full 54-page guideline was released online in Circulation during the conference and is available at http://circ.ahajournals.org/cgi/reprint/CIR.0b013e3182051b4cv1.
Dr. Smith declared having no relevant financial interests. Dr. Greenland disclosed serving as a consultant to Pfizer, General Electric, and Toshiba.
Copyright (c) 2010 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
芝加哥(EGMN)——美国心脏病学院/美国心脏学会新近公布的无症状成人心血管风险评估指南，检测项目易于记忆，但在日常应用方面并没获得好评。新的指南在线发表者《循环》杂志上http://circ.ahajournals.org/cgi/reprint/CIR.0b013e3182051b4cv1。
基因检测、载脂蛋白测定及颗粒大小和密度检查的强化血脂检查、动脉斑块的MRI检查、利钠肽水平检测、CT冠脉造影、负荷超声心动图、动脉僵硬度检测以及血流介导性扩张被列为III级推荐检测项目。指南撰写小组专家认为此类检测并无益处而且可能有害，即不推荐用于无心脏病症状人群。
整体风险评估和家族史列为I级推荐项目。指南规定，所有无症状成人均应接受整体心血管风险评分和家族史评估，最好从20岁开始，每5年1次。整体风险评估显示未来10年心血管事件风险为10%~20%的中度风险无症状成人，冠脉钙化评分为IIa级推荐(意味着用于心血管风险评估是合理的) ；对于未来10年心血管事件风险为6%~10%的低至中度风险人群，冠脉钙化评分为IIb级推荐(意味着可能认为是适当的)；对于风险小于6%的人群，冠脉钙化评分为III级推荐。
按照成人治疗专家组III标准，10年风险大于20%的高危无症状成人，年龄小于50岁低风险男性以及小于60岁的低风险女性， C-反应蛋白(CRP)被评为III级。然而，专家认为CRP有益于基于整体风险评估10年风险为中度人群的最终风险评估。对于LDL-C<130 mg/dL且年龄≥50岁男性和年龄≥60岁女性，CRP作为决定选择接受他汀类治疗的依据获得IIa级推荐，而对于年龄≤50岁男性和年龄≤60岁女性的无症状人群，CRP为IIb级推荐。
对于不同情况的中度风险人群，IIa 或 IIb级推荐检测项目还包括：踝臂指数(外周动脉疾病患者)、静息心电图(高血压、糖尿病患者)、常规超声心动图(高血压患者)、运动心电图(强度锻炼项目之前)、颈动脉内膜中层厚度(专家测定)以及HbA1c，尿微量白蛋白(无症状的糖尿病、高血压成人患者为IIa级，无糖尿病和高血压的无症状中度风险成人为IIb级)。
指南撰写小组专家认为，作为有益的风险预测指标，应在调整已知风险因素之后仍为独立预测因素。除此之外，还应能够提高风险预测，改善推荐治疗，并且证明通过新的预测指标并采取相应治疗措施的确能够获得更佳临床效果。
部分专家披露与医药企业存在经济利益关系。
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