Vijay G. Divakaran, MD, MPH and Glenn N. Levine, MD

1. What are generally accepted indications for cardiac catheterization?

    Although recommendations are consistently evolving, those listed here are generally accepted as reasonable indications for cardiac catheterization. Cardiac catheterization is a relatively safe procedure; however, life-threatening complications can rarely occur (see later), so there needs to be a clearly thought out and documented indication for catheterization and a plan for how to use the information obtained during catheterization for patient management.

2. What are the risks of cardiac catheterization?

    The risks of cardiac catheterization will depend to some extent on the individual patient. For “all comers,” the risk of death is approximately 1 in 1000, with the risk of myocardial infarction or stroke rarer than 1 in 1000. The risk of any major complication in “all comers” is less than 1%. These risks are summarized in Table 14-1.

3. How are coronary lesions assessed?

    Coronary lesions are most commonly assessed in day-to-day practice based on subjective visual impression (Fig. 14-1). Lesions are subjectively given a percent stenosis, ideally based on ocular assessment of at least two orthogonal images of the lesion. Studies have shown interobserver and intraobserver variability in judging coronary stenosis from as little as 7% to as much as 50%. Quantitative coronary angiography (QCA) more objectively assesses the lesion severity than does “ocular judgment,” but is not commonly used in day-to-day practice. QCA generally grades lesions as less severe than does subjective ocular judgment of a lesion’s severity. Intravascular ultrasound (IVUS) can more accurately assess the total plaque burden and severity of a lesion than can ocular judgment or QCA. Fractional flow reserve (FFR) is increasingly being used to measure the severity of a lesion from a physiologic standpoint (see later).

4. What is considered a “significant” stenosis?

    The classification of significant stenosis depends on the clinical context and what one considers “significant.” Coronary flow reserve (the increase in coronary blood flow in response to agents that lead to microvascular dilation) begins to decrease when a coronary artery stenosis is 50% or more of the luminal diameter. However, basal coronary flow does not begin to decrease until the lesion is 80% to 90% of the luminal diameter.

5. What is fractional flow reserve (FFR)?

    Physiologic assessment of blood flow through a stenotic lesion can be safely and reliably performed in the catheterization laboratory using a coronary wire with a pressure sensor at its tip. The wire is advanced across the lesion of interest, and the ratio of distal coronary pressure to proximal aortic pressure is assessed after maximal hyperemia is achieved (Fig 14-2). This ratio is called FFR. Normal values are close to 1, and a ratio less than 0.75 to 0.80 is taken as indicating a “physiologically significant stenosis.” Adenosine is typically used as a pharmacologic agent to achieve maximal hyperemia.