Approximately half of the acute coronary syndromes that recur within 3 years of an index ACS treated percutaneously involve a different lesion that was visualized on angiography at that time but was not severe enough to require treatment, according to a report in the Jan. 20 issue of the New England Journal of Medicine.
The rate of recurrent major adverse cardiovascular events was 20% in this multicenter prospective study involving 697 patients with ACS who were successfully treated with PCI and medical therapy, then followed for 3 years, said Dr. Gregg W. Stone of Columbia University Medical Center/New York Presbyterian Hospital and the Cardiovascular Research Foundation, New York, and his associates.
They conducted the Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study using new imaging tools that help characterize the content of coronary lesions, to identify factors that raise the risk for recurrent ACS.
The study, conducted at 37 medical centers in the United States and Europe, was funded by Abbott Vascular and Volcano. Abbott participated in the study design, site selection, data collection, and data analysis.
Study subjects were enrolled after undergoing successful and uncomplicated PCI for all coronary lesions thought to be responsible for their index ACS. At that time, the subjects underwent angiography, then conventional gray-scale intravascular ultrasonography and the newly available radiofrequency intravascular ultrasonography of the left main coronary artery and the proximal 6-8 cm of each of the major epicardial coronary arteries.
Unlike the other imaging techniques, radiofrequency intravascular ultrasonography provides data about tissue composition. It allowed the investigators to classify coronary lesions as thin-cap fibroatheroma, thick-cap fibroatheroma, pathologic intimal thickening, fibrotic plaque, or fibrocalcific plaque.
The median age of the study subjects was 58 years; 24% were women, and 17% had diabetes.
“We found that approximately one in five patients with [ACS] ... had recurrent major adverse cardiovascular events within 3 years. Events were nearly equally divided between those related to initially treated lesions and those related to previously untreated lesions,” Dr. Stone and his colleagues said.
“Most events were rehospitalizations for unstable or progressive angina; death from cardiac causes, cardiac arrest, and MI were less common,” they noted.
Radiofrequency intravascular ultrasonography at baseline revealed that most of the “nonculprit” coronary lesions – those that had been considered mild on the index angiography and were not treated at that time – were characterized by a large plaque burden, a small luminal area, or both. Half of them also were thin-cap fibroatheromas. These traits had not been visible on conventional angiography.
In contrast, no major events arose from arterial segments with a plaque burden that blocked less than 40% of the lumen. And nonfibroatheromas rarely caused such events, regardless of their plaque burden or the luminal area they blocked.
These study findings suggest that thin-cap fibroatheromas, lesions with a large plaque burden, and lesions with a small luminal area are particularly prone to cause recurrent ACS.
However, “there are several reasons why the methods we have used are not currently suitable for clinical application as a means of identifying sites in the coronary vasculature for potential intervention,” the investigators noted (N. Engl. J. Med. 2011:364:226-35).
First, this method lacks specificity at present. Radiofrequency intravascular ultrasonography identified a total of 595 thin-cap atheromas in these subjects, but only 26 of them caused recurrent ACS. Similarly, fewer than 10% of the lesions that carried plaque burdens of 70% or more and the lesions with a 4-mm or smaller luminal area caused recurrent ACS.
“Even when all three predictive variables were present, the event rate rose to only 18%,” they said.
Second, catheters used for this type of ultrasonography could only access the proximal 6-8 cm of the coronary tree. This meant that only 51 of the 106 “nonculprit” lesions seen on angiography could be evaluated by radiofrequency intravascular ultrasonography.
Third, the technique was associated with very serious adverse events in 11 patients in this study: 10 coronary dissections and 1 perforation, which in turn caused 4 nonfatal MIs.
And fourth, it is still unclear what therapies should be used when the technique identifies these high-risk lesions.
Copyright (c) 2010 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
《新英格兰医学杂志》1月20日刊载的一项研究表明，首次急性冠状动脉综合征(ACS)经皮治疗3年内复发的病例, 半数是由首次发病时血管造影观察到的不需治疗的轻微病变引起。
PROSPECT是一项多中心前瞻性研究，在美国和欧洲的37个医疗中心进行，纳入697例经PCI和药物治疗成功的ACS患者。患者的中位年龄为58岁，24%为女性，17%患糖尿病。该研究采用新型影像工具即射频血管内超声来定性冠状动脉病变的内容物及识别增加ACS复发风险的因素。与其他影像技术不同，射频血管内超声可检查组织成分，使研究者能够将冠状动脉病变分为薄帽的纤维粥样斑块、厚帽的纤维粥样斑块、病理性内膜增厚、纤维化斑块或纤维钙化斑块。
在首次发病时，通过血管造影、传统灰度血管内超声和新型射频血管内超声检查左主冠状动脉及各条主要心外膜冠状动脉近端6~8 cm节段。基线射频血管内超声检查显示，多数“非罪犯”冠状动脉病变(即首次发病时血管造影检出的、未予治疗的轻微病变)具有斑块负荷大、管腔面积小或两者兼有的特性。这些特性无法通过传统血管造影观察到。这些轻微病变半数为薄帽的纤维粥样斑块。
研究显示，在首次发病后3年内，每5例ACS患者中就有1例复发主要不良心血管事件(复发率为20%)。一半事件是由经过初治的病变引起，另一半是由此前未治疗的病变引起。多数事件为不稳定型或进展型心绞痛导致的再次入院；心源性死亡、心脏骤停和MI较为少见。
研究结果表明，薄帽纤维粥样斑块、斑块负荷大的病变、以及管腔面积小的病变特别易引起ACS复发。相比之下，斑块负荷小(管腔阻塞面积小于40%)的动脉节段未引起主要事件。非纤维粥样斑块很少引起此类事件，不管其斑块负荷或阻塞的管腔面积如何。
不过研究者指出，虽然新型射频血管内超声具有上述诸多优势，但由于其缺乏特异性、所用的导管仅能到达冠状动脉树近端6~8 cm处等原因，目前尚不适用于识别冠状动脉血管结构中哪些部位适宜作介入治疗(N. Engl. J. Med. 2011:364:226-35)。
这项研究获雅培血管部和Volcano公司资助。雅培参与研究设计、试验场所的选取、数据收集和数据分析。
爱思唯尔 版权所有
