冠状动脉血流储量可确认心脏风险低的年长者


  【24drs.com】根据发表于SNM 2012年会的研究,使用正子断层造影(PET)对75岁以上年长者测量冠状动脉血流储量(CFR)发现,有些人保有冠状动脉血管功能,心脏方面的死亡风险较低。
  
  布莱根妇女医院、哈佛医学院心血管医学暨影像研究员Venkatesh Murthy博士表示,加入量化的CFR使得可以确认低风险的年长者,并对临床变项提供更多层次的风险类别,对缺血性和疤痕、以及左心室射出分率提供半量化测量。
  
  Murthy博士表示,将75岁以上和75岁以下者比较时,发现其心脏方面死亡率大幅增加。
  
  他表示,我们想探究这是否是老龄化时的不可避免后果、是否可以确认某些病患未具此一趋势,并有比同龄者更健康的血管;事实证明,我们可以找到一组年纪大但是有健康血管者,且这组人超出我们的预期。
  
  Murthy博士等人追踪了704名75岁以上患者,这些人被转诊以rubidium (Rb)-82 PET进行休息时和压力时的心肌灌注影像;追踪这些病患,追踪期间中位数为1.2年(4分位距:0.5-2.1年)。
  
  PET灌注异常的范围和严重度使用半量化可视化分析评估。
  
  初级终点是心脏方面死亡,根据社会安全死亡指标、国家死亡指标、病历纪录等确认。
  
  整体而言,66的病患(9.4%)死于心脏方面原因。研究世代中,每年的心因性死亡率逐渐增加。对于正常PET扫描的病患,每年的心因性死亡率为3.5%,对于轻微到中度异常PET扫描者则是5.6%,对于严重异常PET扫描者则是11.3% (P= .0001)。
  
  纳入年纪、性别、出现胸痛与相关特征、心肌梗塞病史、抽菸、高胆固醇、糖尿病、心电图异常、休息时左心室射出分率以及在压力下的改变、疤痕和缺血性的范围及严重度等临床风险因素之后,研究者发现,CFR小于等于中位数1.5者,心因性死亡风险增加几乎2倍(风险比,1.92 vs CFR >1.5;P= .02)。
  
  Murthy博士表示,即便纳入临床风险因素和传统的压力检测结果之后,低CFR和心因性死亡风险增加92%有关;再者, 分析Cox部分风险显示,CFR增加了临床和PET变项之外的渐进式预后价值。
  
  对于正常心肌灌注影像检查的病患,每年的心因性死亡率为6.5%(CFR小于等于1.5者),如果CFR大于1.5则是仅1.8% (P= .01)。
  
  Murthy医师表示,他希望这篇研究可以帮助我们更佳地筛选可受益于更积极处置冠状动脉疾病的患者。
  
  他指出,这将可以帮助预防未能受益病患的过度治疗,因而避免并发症和降低费用;其次,研究发现Rb-82 PET可以确认极佳心脏预后的一大组年长者,不论年纪与其它风险因素;为研究者打开减少老化之心血管后遗症的新方法。
  
  Murthy医师表示,对于许多需要压力检测的年长者,PET影像有优于其它压力检测方式的优势;此外,令人鼓舞的是,PET检查发现血管健康良好者有相当好的预后。
  
  加州医学中心心血管核子医学主任Elias H. Botvinick医师表示,这是个新的参数,让我们有新观点,我们一直注意于狭窄的冠状动脉血管,现在,我们了解预后不必然和这些相关,但是和比较小的血管有关。
  
  我们的治疗目标在预防和治疗大冠状动脉的狭窄,但是现在我们有更大、似乎超越所有界线的一个问题,我们该如何预防储量降低并加以治疗?或许以类似于治疗和预防主要血管狭窄的方法,我们在治疗心外膜血管方面并没有太多成功经验,我认为,对于治疗储量异常,将会是更严厉的挑战。
  
  资料来源:http://www.24drs.com/professional/list/content.asp?x_idno=6857&x_classno=0&x_chkdelpoint=Y
  

Coronary Flow Reserve Identifies Seniors at Low Cardiac Risk

By Fran Lowry
Medscape Medical News

June 18, 2012 (Miami Beach, Florida) — Measuring coronary flow reserve (CFR) with positron emission tomography (PET) in patients 75 years and older reveals that some of them have preserved coronary vascular function and are at low risk for cardiac death, according to research presented here at the SNM 2012 Annual Meeting.

"The addition of quantitative CFR enables the identification of low-risk cohorts among elderly patients and provides incremental risk stratification over clinical variables, semiquantitative measures of ischemia and scar, and left ventricular ejection fraction," said lead author, Venkatesh Murthy, MD, PhD, cardiovascular medicine and imaging fellow at Brigham and Women's Hospital and Harvard Medical School, in Boston, Massachusetts.

"There is a dramatic increase in rates of cardiac death when you compare patients older than age 75 with those younger than 75," Dr. Murthy told Medscape Medical News.

"We were interested in investigating whether this is an unavoidable consequence of aging and whether we could identify a subset of patients who defy this trend and have much healthier blood vessels than their peers. It turns out we can identify a group of patients who are older chronologically but who have healthy blood vessels; this group is larger than we expected," he said.

Dr. Murthy and his team followed 704 consecutive patients 75 years and older who were referred for rest and stress myocardial perfusion imaging with rubidium (Rb)-82 PET. The patients were followed for a median of 1.2 years (interquartile range, 0.5 to 2.1 years).

The extent and severity of PET perfusion abnormalities were assessed with a semiquantitative visual analysis.

Cardiac death was the primary end point and was determined from the Social Security Death Index, the National Death Index, and medical records.

Overall, 66 patients (9.4%) died from cardiac causes. There was a stepwise increase in annualized cardiac mortality rates in the study cohort. For patients with normal PET scans, the annualized cardiac mortality rate was 3.5%, for those with mild to moderately abnormal PET scans, the rate was 5.6%, and for those with severely abnormal PET scans, the rate was 11.3% (P = .0001).

After accounting for clinical risk factors, including age, sex, presence and character of chest pain, history of myocardial infarction, smoking, high cholesterol, diabetes, electrocardiography abnormalities, resting left ventricular ejection fraction and its change during stress, and the combined extent and severity of scar and ischemia, the researchers found that CFR at or below the median of 1.5 was associated with an almost 2-fold increased risk for cardiac death (hazard ratio, 1.92 vs CFR >1.5; P = .02).

"Low CFR was associated with a 92% increase in the risk of cardiac death, even after accounting for clinical risk factors and traditional stress test findings," Dr. Murthy said.

Further, analysis of the Cox proportional hazards showed that the CFR added incremental prognostic value beyond clinical and PET variables, he said.

In patients with a normal myocardial perfusion imaging test, the annualized cardiac mortality rates were 6.5% if their CFR was 1.5 or below, and just 1.8% if their CFR was above 1.5 (P = .01).

Dr. Murthy said he hopes that this research will allow the better selection of patients who will benefit from more aggressive management of their coronary disease.

He added that this will help prevent the overtreatment of "patients who won't benefit, thereby avoiding complications and maybe decreasing costs. Second, the finding that Rb-82 PET can identify a large subset of older patients with an excellent cardiac prognosis, despite age and other risk factors, opens new avenues for investigations into novel ways to limit the adverse cardiovascular consequences of aging."

PET imaging might have meaningful advantages over competing types of stress tests in many older patients who need stress testing, Dr. Murthy said.

"Plus, it is encouraging to find that patients who have good vascular health on PET have a very good prognosis," he said.

Medscape Medical News asked Elias H. Botvinick, MD, professor of medicine and director of cardiovascular nuclear medicine at San Francisco, California Medical Center, to comment on this study.

"It's a new parameter; it gives us new eyes. We have been looking and focused on narrowings of the epicardial coronary vessels. Now we're learning that prognosis is not necessarily or completely tied to that, but to the reactivity of the smaller vessels," said Dr. Botvinick, who cochaired the oral session.

"Our therapy has been aimed at preventing and treating the narrowing of the major coronary vessels, but now we have a bigger enemy, one that seems to go across all boundaries. How are we going to prevent the loss of flow reserve and how are we going to treat it? Probably in a way similar to the way we approach treating and preventing the narrowings of the main blood vessel. We haven't been too successful in treating epicardial disease, and I think it is going to be even tougher treating abnormalities of flow reserve."

Dr. Murthy and Dr. Botvinick have disclosed no relevant financial relationships.

SNM 2012 Annual Meeting: Abstract 22. Presented June 10, 2012.

    
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