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.

6. How is FFR used to guide coronary stenting?

    In patients with angina, if the “culprit” lesion is visually estimated to be intermediate (50% to 70% stenosis) in severity, FFR may be used to guide management in determining if the lesion is physiologically significant. When evaluating whether a lesion warrants revascularization, use of FFR has been shown to be a clinically useful tool. Revascularization may be safely deferred for lesions with FFR greater than 0.75 to 0.80. If the FFR is less than 0.75, revascularization with percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) is appropriate if clinically indicated.

7. During cardiac catheterization, how is aortic or mitral regurgitation graded?

    For aortic regurgitation, an aortogram is performed in the ascending thoracic aorta above the aortic valve and the amount of contrast that regurgitates into the left ventricle is noted. For mitral regurgitation, a left ventriculogram is performed and the amount of contrast that regurgitates into the left atrium is noted. The systems used to grade the degree of regurgitation are similar for the two valvular abnormalities, and based on a 1+ to 4+ system, where 1+ is little if any regurgitation and 4+ is profound or severe regurgitation. Regurgitation of 3+ or 4+ is often considered “surgical” regurgitation, although the criteria for surgery are more complex than this (see Chapters 30 and 31 on aortic valve disease and on mitral valve disease, respectively). Table 14-2 summarizes the grading of regurgitant lesions as assessed by cardiac catheterization and “ballpark” regurgitant fractions for each degree of regurgitation.

8. What is thrombolysis in myocardial infarction (TIMI) flow grade?

    TIMI flow grade is a system for qualitatively describing blood flow in a coronary artery. It was originally derived to describe blood flow down the infarct-related artery in patients with STEMI. Reportedly, it was originally written down on a napkin or the back of an envelope during an airplane flight. The grades are based on observing contrast flow down the coronary artery after injection of the contrast agent, and are as follows:

9. What is IVUS?

    IVUS is the direct assessment of coronary arterial wall using a flexible catheter with a miniature ultrasound probe at its tip. Upon insertion into the coronary artery, IVUS provides true cross-sectional images of the vessel, delineating the three layers of the vessel wall (Fig 14-3). IVUS may aid in the assessment of coronary stenosis, plaque morphology, and optimal stent expansion when angiographic imaging is inadequate or indeterminate.

10. What are the different methods of describing the aortic transvalvular gradient in a patient undergoing cardiac catheterization for the evaluation of aortic stenosis?

    Three terms used to describe the gradient are illustrated in Figure 14-4 and are:

11. Which patients should be premedicated to prevent allergic reactions to iodine-based contrast agents?

    In patients with a history of prior true allergic reaction (e.g., hives, urticaria, or bronchoconstriction) to iodine-based contrast agents, the risk of repeat anaphylactoid reaction to contrast agents is reported to be 17% to 35%. Such patients should be premedicated before angiography. The standard regimen is 50 mg of prednisone orally (PO), 13 hours, 7 hours, and 1 hour before the procedure, and 50 mg PO of diphenhydramine 1 hour before the procedure, although a regimen of 60 mg PO of prednisone the night before and morning of the procedue, along with 50 mg PO of diphenhydramine the morning of the procedure, is also used by some. The 2011 American College of Cardiology Foundation/American Heart Association/Society for Cardiovascular Angiography and Interventions (ACCF/AHA/SCAI) guidelines do not consider allergy to fish or shellfish an indication for steroid pretreatment.

12. What are the major risk factors for contrast nephropathy?

    Preexisting renal disease and diabetes are the two major risk factors for the development of contrast nephropathy. The risk of contrast nephropathy is also related to the amount of iodine-based contrast used during the catheterization procedure. Preprocedure and postprocedure hydration is the most established method of reducing the risk of contrast nephropathy. The 2011 ACCF/AHA/SCAI PCI guidelines suggest a regimen of isotonic crystalloid (e.g., normal saline) 1.0 to 1.5 ml/kg/hr for 3 to 12 hours before the procedure and continuing for 6 to 24 hours after the procedure. Those same guidelines conclude that treatment with N-acetylcysteine does not reduce the risk of contrast nephropathy and is not indicated. Measures of other treatments to decrease the risk of contrast nephropathy, such as sodium bicarbonate infusion or ultrafiltration, have produced heterogeneous and conflicting data.

13. What are the major vascular complications with cardiac catheterization?

    In general, major vascular complications are uncommon with diagnostic cardiac catheterization and more common with PCI, which may require larger sheath placement, venous sheath placement, and more intense or prolonged anticoagulation. Nevertheless, practitioners and patients should be aware of the following potential vascular complications:

14. What are vascular closure devices?

    Vascular closure devices are hemostatic devices that obviate the need for prolonged compression at the arterial access site following angiography. These devices decrease the duration of bed rest and afford earlier mobility after the procedure. Vascular closure devices have not been convincingly demonstrated to decrease the risk of vascular complications, including bleeding.

15. What is the difference between radial and femoral access in cardiac catheterization?

    Left heart catheterization and coronary angiography are commonly performed using catheters inserted through either the femoral or radial arteries. Radial access is associated with a lower incidence of vascular complications such as bleeding.

16. What is intracardiac echo (ICE)?

    ICE is the direct imaging of cardiac structures via transvenous insertion of a miniaturized echo probe. Most commonly, the device is inserted via the femoral vein and threaded up to the right atrium. ICE is used to visualize the interatrial septum and fossa ovalis, aiding with transseptal puncture, percutaneous treatment of atrial septal defect (ASD) or patent foramen ovale (PFO), and during electrophysiologic procedures, and imaging the fossa ovalis and pulmonary veins.

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