乳房鈣化可能可以反映出腎臟病的心血管風險


  【24drs.com】January 20, 2011 — 對於末期腎臟疾病(end-stage renal disease,ESRD)婦女,例行性乳房X光攝影可能可發現重要但難以偵測的心血管風險標記。
  
  Emory大學的研究人員發現,相較於沒有ESRD的對照組婦女,ESRD婦女更可能會有乳房動脈鈣化(breast arterial calcification,BAC);不同於心血管疾病中常見、發生於動脈內膜的粥狀動脈血栓,BAC是發生在動脈壁中間層。如同新聞稿中所指出的,動脈鈣化可能會導致ESRD患者的心臟病高死亡率,動脈中間層鈣化會造成難以偵測的動脈硬化。
  
  第一作者Valerie Duhn醫師等人寫道,該研究首次詳細檢視BAC及其與慢性腎臟病(chronic kidney disease,CKD)的關係。
  
  作者們解釋,中間層鈣化與動脈粥狀硬化或發炎無關,除了大動脈之外,也在小動脈發生,是因為血管順應性降低而造成損傷;它在腎衰竭、糖尿病與年長者特別明顯,但是它的病理生理學與自然史尚未被充分瞭解,這些鈣化被視為造成增加與腎衰竭有關的心血管疾病風險。
  
  根據組織學與血管大小,乳房X光攝影偵測的動脈鈣化位於中間層,但是這尚未有所定論。作者們指出,ESRD病患的BAC盛行率也不清楚,他們假設,BAC應可作為一般醫療分類的一項標記,乳房X光攝影可幫助確認腎病婦女之中間層鈣化的風險因素和盛行率。
  
  作者們回溯檢視了71名ESRD婦女,在過去10年內於Emory健康照護體系接受過乳房X光攝影,每位病患被隨機與一名腎功能正常、在2007-2009年間接受過乳房X光攝影篩檢的對照組配對,對照組的年紀(差距在1歲之內)、種族和糖尿病狀態皆與其相仿,由一位研究者在不知道研究對象的特徵之下回顧所有的乳房X光攝影。
  
  在ESRD婦女中,45人(63%)有BAC,對照組有12人(17%;P <. 001),有ESRD但有或沒有BAC也被比較,相較於有ESRD但無BAC的病患,有ESRD和BAC的病患明顯比較年長(P = .013)且進行透析的期間比較久(P = .024)。BAC組也傾向有較高的糖尿病盛行率(62% vs 39%;P = .053),在邏輯多變項模式中,只有年紀和ESRD是鈣化的顯著預測因子。
  
  為了確認BAC是否可作為一般中間層鈣化的標記,其中一位作者(不知道乳房X光攝影結果)回顧了62名ESRD病患的X光照片,看看在他們的手、腕、下肢、腳踝或腳有無動脈中間層鈣化。在發現有中間層鈣化的21名病患中,19人(90%)有BAC,在無BAC的31名病患中,只有2人(6%)有周邊動脈鈣化。
  
  此外,在發生ESRD之前5.5 ± 0.7年,有36%的乳房X光攝影出現BAC(相較於健康對照組,P < .05 ),但是其中只有14%的第3期CKD患者在發現該病之前即在乳房X光攝影出現BAC。
  
  作者們指出,此研究有三個重要的研究發現,第一,乳房動脈沒有內層的鈣化或其他粥狀動脈硬化徵兆 ;第二,鈣化僅限於中間或內彈性層;第三,乳房X光攝影出現的早期鈣化,在樣本的X光影片並不明顯,顯示中間層鈣化的盛行率大於X光攝影所見。
  
  由於多數CKD婦女都還不到建議每年進行乳房X光攝影的年紀,乳房X光攝影或許也有助於研究中間層鈣化的發展病程,作者們建議,進行後續研究,以確認各CKD階段時的BAC盛行率,確認更多風險因素與適當的治療,乳房電腦斷層也可用來更精準地確認這些病灶的特徵。
  
  這項研究限制的包括,樣本數少、使用回溯分析、根據乳房X攝影偵測BAC的主觀本質;不過,研究結果顯示,可利用乳房X光攝影作為慢性腎臟病患檢查中間血管鈣化的特定工具。
  
  作者們皆宣告沒有相關資金上的往來。
  
  Clin J Am Soc Nephrol. 線上登載於2011年1月20日。

Breast Calcifications May Reflect Cardiovascular Risk in Kidney Disease

By Norra MacReady
Medscape Medical News

January 20, 2011 — Routine mammography may reveal an important, but difficult to detect, marker of possible cardiovascular risk in women with end-stage renal disease (ESRD), according to investigators at Emory University in Atlanta, Georgia.

The researchers found that women with end-stage renal disease (ESRD) were significantly more likely to have breast arterial calcification (BAC) than a control group of women without ESRD. Unlike the atherosclerotic plaques commonly associated with cardiovascular disease, which occur in the arterial intima, BAC develops in the medial layer of the arterial walls. As described in a press release, arterial calcium may contribute to the high rate of death from heart disease in those with ESRD. Arterial calcium in the medial layers contributes to arterial stiffness, but it is difficult to detect.

This study is the first to examine BAC and its relationship to chronic kidney disease (CKD) in detail, lead author Valerie Duhn, MD, and colleagues write.

"Calcification in the medial layer is independent of atherosclerosis or inflammation, occurs in small arteries in addition to large arteries, and is thought to be detrimental by decreasing arterial compliance," the authors explain. "It is observed specifically in renal failure, diabetes, and aging, but its pathophysiology and natural history are otherwise poorly understood." These calcifications are thought to contribute to the increased risk for cardiovascular disease associated with renal failure.

Mammography detects arterial calcifications that should be located in the media, based on their histology and vessel size, but this has never been conclusively demonstrated. The prevalence of BAC in ESRD also has been unclear, the authors note. They hypothesized that BAC could serve as a marker of generalized medial calcification, and that mammography could help determine the prevalence and risk factors for medial calcification in women with kidney disease.

The authors retrospectively identified 71 women with ESRD who had undergone screening mammography within the Emory healthcare system within the last 10 years. Each patient was randomly paired with a control patient with normal renal function who had undergone screening mammography between 2007 and 2009. The controls were matched for age (to within 1 year), race, and diabetes status. One individual reviewed all of the mammograms without knowing the characteristics of the participants.

Of the women with ESRD, 45 (63%) had BACs compared with 12 of the control patients (17%; P <. 001). Patients with ESRD with and without BAC were also compared. Patients with ESRD with BAC were significantly older (P = .013) and had been on dialysis longer (P = .024) than the patients with ESRD without BAC. There was also a trend toward a higher prevalence of diabetes in the BAC group (62% vs 39%; P = .053). In a logistic multivariate model, only age and ESRD were significant predictors of calcification.

To determine whether BAC could act as a marker of generalized medial calcification, one of the authors, who was unaware of the mammography findings, reviewed radiographs from 62 participants with ESRD for medial calcification in the arteries of their hands, wrists, lower legs, ankles, or feet. Of 21 patients with findings indicative of medial calcification, 19 had BAC (90%). Peripheral arterial calcification was present in only 2 (6%) of 31 patients without BAC.

Also of note, BAC was present in 36% of mammograms 5.5 ± 0.7 years before the onset of ESRD (P < .05 compared with healthy control patients), but only 14% of those with stage 3 CKD had BAC on mammogram before onset of the disease.

Three important findings emerged from this study, the authors point out. First, no intimal calcification or other signs of atherosclerosis were seen in the breast arteries; second, calcification was limited to the media or the internal elastic lamina; and third, "early stages of calcification were detected [on mammography] that were not apparent on the specimen radiographs, indicating that the prevalence of medial calcification is greater than that indicated by radiography."

Because most women with CKD are at an age where yearly mammograms are recommended, mammograms may also help in studying the development and progression of medial calcifications. The authors suggest that future studies determine the prevalence of BAC at different stages of CKD and identify more risk factors, as well as optimal treatment. Computed tomography of the breast should allow for even more precise characterization of these lesions.

Limitations to this study included the small sample size, the use of retrospective analysis, and the subjective nature of detecting BAC on the mammograms. Nevertheless, the authors write, "the results demonstrate the utility of mammography as a specific tool for examining medial vascular calcification in chronic kidney disease."

The authors have disclosed no relevant financial relationships.

Clin J Am Soc Nephrol. Published online January 20, 2011.

    
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