冠狀動脈血流儲量可確認心臟風險低的年長者


  【24drs.com】根據發表於SNM 2012年會的研究,使用正子斷層造影(PET)對75歲以上年長者測量冠狀動脈血流儲量(CFR)發現,有些人保有冠狀動脈血管功能,心臟方面的死亡風險較低。
  
  布萊根婦女醫院、哈佛醫學院心血管醫學暨影像研究員Venkatesh Murthy博士表示,加入量化的CFR使得可以確認低風險的年長者,並對臨床變項提供更多層次的風險類別,對缺血性和疤痕、以及左心室射出分率提供半量化測量。
  
  Murthy博士表示,將75歲以上和75歲以下者比較時,發現其心臟方面死亡率大幅增加。
  
  他表示,我們想探究這是否是老齡化時的不可避免後果、是否可以確認某些病患未具此一趨勢,並有比同齡者更健康的血管;事實證明,我們可以找到一組年紀大但是有健康血管者,且這組人超出我們的預期。
  
  Murthy博士等人追蹤了704名75歲以上患者,這些人被轉診以rubidium (Rb)-82 PET進行休息時和壓力時的心肌灌注影像;追蹤這些病患,追蹤期間中位數為1.2年(4分位距:0.5-2.1年)。
  
  PET灌注異常的範圍和嚴重度使用半量化可視化分析評估。
  
  初級終點是心臟方面死亡,根據社會安全死亡指標、國家死亡指標、病歷紀錄等確認。
  
  整體而言,66的病患(9.4%)死於心臟方面原因。研究世代中,每年的心因性死亡率逐漸增加。對於正常PET掃描的病患,每年的心因性死亡率為3.5%,對於輕微到中度異常PET掃描者則是5.6%,對於嚴重異常PET掃描者則是11.3% (P= .0001)。
  
  納入年紀、性別、出現胸痛與相關特徵、心肌梗塞病史、抽菸、高膽固醇、糖尿病、心電圖異常、休息時左心室射出分率以及在壓力下的改變、疤痕和缺血性的範圍及嚴重度等臨床風險因素之後,研究者發現,CFR小於等於中位數1.5者,心因性死亡風險增加幾乎2倍(風險比,1.92 vs CFR >1.5;P= .02)。
  
  Murthy博士表示,即便納入臨床風險因素和傳統的壓力檢測結果之後,低CFR和心因性死亡風險增加92%有關;再者, 分析Cox部分風險顯示,CFR增加了臨床和PET變項之外的漸進式預後價值。
  
  對於正常心肌灌注影像檢查的病患,每年的心因性死亡率為6.5%(CFR小於等於1.5者),如果CFR大於1.5則是僅1.8% (P= .01)。
  
  Murthy醫師表示,他希望這篇研究可以幫助我們更佳地篩選可受益於更積極處置冠狀動脈疾病的患者。
  
  他指出,這將可以幫助預防未能受益病患的過度治療,因而避免併發症和降低費用;其次,研究發現Rb-82 PET可以確認極佳心臟預後的一大組年長者,不論年紀與其他風險因素;為研究者打開減少老化之心血管後遺症的新方法。
  
  Murthy醫師表示,對於許多需要壓力檢測的年長者,PET影像有優於其他壓力檢測方式的優勢;此外,令人鼓舞的是,PET檢查發現血管健康良好者有相當好的預後。
  
  加州醫學中心心血管核子醫學主任Elias H. Botvinick醫師表示,這是個新的參數,讓我們有新觀點,我們一直注意於狹窄的冠狀動脈血管,現在,我們了解預後不必然和這些相關,但是和比較小的血管有關。
  
  我們的治療目標在預防和治療大冠狀動脈的狹窄,但是現在我們有更大、似乎超越所有界線的一個問題,我們該如何預防儲量降低並加以治療?或許以類似於治療和預防主要血管狹窄的方法,我們在治療心外膜血管方面並沒有太多成功經驗,我認為,對於治療儲量異常,將會是更嚴厲的挑戰。
  
  資料來源: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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