CT血管造影篩選可決定是否進行侵犯性血管造影術


  Dec. 3, 2004 (芝加哥) - 北美放射線醫學會第90屆年會中,一項研究結果顯示,利用多層電腦斷層掃描(CT)對心臟進行血管造影,可以對已產生症狀的患者作篩選,並決定是否需要進行侵犯性的血管造影手術;在不增加患者風險的情況下,可以藉此降低侵犯性血管造影手術的次數達三分之一。
  
  克里夫蘭Philips Medical Systems的資深科學家Peter John醫師,在替德國慕尼黑的Ralph Haberl醫師作發表時表示,Haberl醫師無法前來參加本會議,Philips Medical Systems贊助了本研究部分的經費。
  
  Johnson醫師表示,這項研究在單一的醫學中心進行,研究對象一共有135位患者,這些都是冠狀動脈疾病的疑似患者,患有急性動脈異狀、及曾有心肌梗塞病史的患者,都會被排除在本研究之外;根據研究準則,所有患者皆須接受CT鈣指數測量,如果鈣指數超過1000,那CT就會停止運作,並立刻進行侵犯性的血管造影手術;一共有16位患者因為鈣指數過高,而被本研究排除。
  
  CT血管造影法所使用的儀器為一16片螺旋式的CT掃描儀(型號Philips MX8000,多片螺旋式,掃描時間250ms,單片厚度1.0mm,顯影劑100cc,流速4 cc/sec,回復性呼吸),閉氣時間為18到26秒,瞬時分辨率以心跳作依據,介於53到210ms之間,所有患者在進行CT前一個小時皆使用了100 mg的metoprolol。
  
  CT血管造影法和侵犯性的血管造影術,分別由兩位不同的研究人員,以美國心臟協會(AHA)的15-區塊模式作比較;Johnson醫師表示,本研究一共檢視了1755個區塊,他承認,這個數量並不足以代表AHA模式的所有區塊,因為遠端區塊的造影很困難,這些包含第3、10、12及第13區塊;所分析的1755個區塊中,1601個的造影品質足以作為診斷用,這些是屬於較好的區塊。
  
  CT造影術排除了59位患者的狹窄症狀,但是在侵犯性血管造影手術時發現,這59位當中,有7位出現了狹窄的跡象,這7位中,有2位需要對冠狀動脈進行經皮的血管再造手術;相對的,鈣指數所排除的25位患者中,有6位出現明顯的狹窄症狀,其中的4位需要介入性的治療。
  
  根據研究人員的分析,CT血管造影的敏感度為71%,特定性為98%。
  
  任教於史丹福大學醫學院的Geogffrey Rubin醫師表示,這些研究的結果具有激勵性,但是我們必須要問自己,98%的負面預測值是否足夠;也就是說,50位患者中,有一位回家後還會有明顯的病症,這樣可以嗎?
  
  Rubin醫師並未參與該項研究,但他在研究摘要的發表會上擔任主持人。

CT Angiography Useful in Ident

By Peggy Peck
Medscape Medical News

Dec. 3, 2004 (Chicago) — Cardiac computed tomography (CT) angiography using multislice CT as a filter to select symptomatic patients for invasive angiography may reduce the number of diagnostic angiographies by more than one third without increasing risk to patients, according to results presented here at the Radiological Society of North America 90th scientific assembly and annual meeting.

Peter Johnson, MD, a senior scientist at Philips Medical Systems in Cleveland, Ohio, presented the study results for Ralph Haberl, MD, a professor of interventional radiology at Krankenhaus Munchen-Pasing in Munich, Germany. He said Dr. Haberl was unable to attend the meeting. Philips Medical Systems provided partial funding for the study.

The single-center study enrolled 135 consecutive symptomatic patients with suspected coronary artery disease. Patients with acute coronary syndrome or with a history of myocardial infarction were excluded from the study. According to protocol, all patients underwent CT calcium scoring but if the calcium score was "more than 1,000, the CT was stopped and patients went immediately to invasive angiography," Dr. Johnson said. Sixteen patients were excluded on the basis of calcium scores.

CT angiography was conducted with a 16-slice spiral CT (Philips MX8000 multislice spiral CT, scan time 250 ms, slice width 1.0 mm, 100 cc of contrast medium, 4 cc/sec, retrospective gating) using an 18- to 26-second breath hold. Temporal resolution was conducted at 53 to 210 msec and was heart-rate dependent. All patients received 100 mg metoprolol one hour prior to CT.

The CT angiography and invasive angiography were directly compared by two independent investigators using the American Heart Association 15-segment model. "A total of 1,755 segments were studied," Dr. Johnson said. During the discussion period he acknowledged that 1,755 "did not represent all segments in the AHA model because there was difficulty imaging distal segments (segments 3, 10, 12, and 13)." Of the 1755 segments included in the analysis "1,601 were diagnostic quality, good segments," he said.

CT angiography ruled out stenosis in 59 patients but "seven of these patients had stenosis by invasive angiography and two of those seven required percutaneous transluminal coronary angioplasty." By contrast, 25 of 135 patients were ruled out by calcium score but "six of those had significant stenosis and four required interventions."

According to the researchers' analysis, the sensitivity of CT angiography was 71% and the specificity 98%.

Geoffrey Rubin, MD, an associate professor of radiology at Stanford University School of Medicine in Stanford, California, said that while the results were encouraging, "I think we have to ask ourselves if a 98% negative predictive value is good enough. That means that one in fifty patients that we send home would have a significant lesion. Are we ready for that?"

Dr. Rubin was not involved in the study, but he served as a moderator for the oral abstract session at which the paper was presented.

RSNA 90th Scientific Assembly and Annual Meeting: Abstract SSQ08-02. Presented Dec. 2, 2004.

Reviewed by Gary D. Vogin, MD

    
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