Methods

This brief review is intended to be used as a "horizon scan" to inform Centers for Medicare & Medicaid Services (CMS) about the current concept of so-called vulnerable plaque (VP) and how it might affect the usage of existing or developing diagnostic and therapeutic technologies. As such, this report is not a detailed technology assessment based on a systematic review of the literature. It does not synthesize or evaluate the results of individual clinical studies and it does not make clinical recommendations.

It should be noted that because the concept of VP is still evolving, it is not an established medical diagnosis. Therefore, any reference to VP in this report concerning its natural history, diagnostic methods, and treatments is by necessity inferential. It refers to conditions that might fall under the current concept of VP and it is not specifically about VP per se. We have taken this broad approach in our review in order to include potentially relevant articles that would otherwise be overlooked in answering these questions. In this report, we will use the term "VP" in quotes to denote that the entity being discussed is yet to be defined and that it refers to conditions related to the current concept of VP. This approach is taken to avoid the awkwardness of repeating these caveats every time the VP concept is mentioned.

Thus, the objective of this review is to retrieve and examine recent publications that describe the current concept of VP and to collect basic information about diagnostic tests and treatments that have been proposed or used to evaluate patients with "VP."

Literature Search Strategy

A literature search was conducted on October 8, 2003 to address the aims of this report. The MEDLINE® and MEDLINE® In-Process & Other Non-Indexed Citations databases (formally PreMEDLINE®) were searched to identify English language publications. Because VP is an emerging concept, there are no specific medical subject headings (MeSH terms). Text words were therefore used exclusively. The MEDLINE® search strategies used are listed below:

The results of the MEDLINE® search from 1966 through the search date produced 1,173 abstracts. Search results of the MEDLINE® In-Process & Other Non-Indexed Citations database yielded 61 additional abstracts. We selected abstracts published since 1998 to understand the current thinking about the VP concept. We also selectively retrieved articles of special interest or relevance published before 1998.

Selecting and Reporting Relevant Studies

We retrieved and reviewed about 150 articles. We selected review articles, commentaries, and editorials to review the concept of VP. We used clinical studies that reported original data as well as review articles to gather information about diagnostic tests, treatments, and the natural history of "VP." Because none of the clinical studies that reported original data explicitly defined the term "vulnerable plaque" and used it as the inclusion criterion, we used our judgment to select studies in clinical settings that are within the broad range of the current concept of VP.

The results of the literature review are organized into the following sections in this report according to the aims. Section 3 summarizes the current concept. Section 4 reviews data on the natural history. Section 5 summarizes diagnostic tests that have been proposed or used. Section 6 reviews proposed treatments. Section 7 discusses how the existence of methods for identifying VP might change the types of treatments or the types of patients who receive treatment for carotid or coronary artery occlusions.

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