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.
- Class III-IV angina despite medical treatment or intolerance of medical therapy
- High-risk results on noninvasive stress testing
- Sustained (more than 30 seconds) monomorphic ventricular tachycardia or nonsustained (less than 30 seconds) polymorphic ventricular tachycardia
- Sudden cardiac death survivors
- Most patients with non–ST-segment elevation acute coronary syndrome (NSTE-ACS) who have high-risk features and no contraindications to early cardiac catheterization and revascularization
- Systolic dysfunction and stress testing results suggesting multivessel disease and potential benefit from revascularization
- Recurrent typical angina within 9 months of percutaneous coronary revascularization
- For assessment of valvular dysfunction or other hemodynamic assessment when the results of echocardiography are indeterminate
- As part of primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI)
- Patients s/p STEMI (with or without thrombolytic therapy) with high-risk features, depressed ejection fraction, or high-risk results on subsequent stress testing
- Within 36 hours of STEMI in appropriate patients who develop cardiogenic shock
- In select patients who are to undergo valve replacement/repair
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 approximately 2%. These risks are summarized in Table 12-1.
3. How are coronary lesions assessed?
Coronary lesions are most commonly assessed in day-to-day practice based on subjective visual impression (Fig. 12-1). 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 ‘‘ocular judgment’’ but is not commonly used in day-to-day practice. QCA generally grades lesions as less severe than 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 ocular judgment or QCA. IVUS is often used when the results of angiography alone still leave doubt as to the ‘‘significance’’ of the lesion (Fig. 12-2).
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Figure 12-1. Coronary angiography of the left coronary artery demonstrates an approximate 90% lesion (arrow) in the left coronary artery.
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Figure 12-2. Intravascular ultrasound (IVUS) demonstrating plaque occluding greater than 60% of the arterial lumen. Coronary angiography had demonstrated only mild narrowing in this segment of coronary artery.
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. During cardiac catheterization, how is aortic or mitral regurgitation graded?
6. What is TIMI flow grade?
Thrombolysis in myocardial infarction (TIMI) flow grade is a system for qualitatively describing blood flow down a coronary artery. It was originally derived to describe blood flow down the
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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, and are as follows:
- TIMI grade 3: normal flow down the entire artery
- TIMI grade 2: contrast (blood) flows through the entire artery but at a delayed rate compared with flow in a normal (TIMI grade 3 flow) artery
- TIMI grade 1: contrast (blood) flows beyond the area of vessel occlusion but without perfusion of the distal coronary artery and coronary bed
- TIMI grade 0: complete occlusion of the infarct-related artery
7. 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 are variably used. Figure 12-3 illustrates these terms and what they imply.
- Peak instantaneous gradient: The maximal pressure difference between the left ventricular pressure and aortic pressure assessed at the exact same time
- Peak-to-peak gradient: The difference between the maximal left ventricular pressure and the maximal aortic pressure
- Mean gradient: The integral of the pressure difference between the left ventricle and the aorta during systole
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Figure 12-3. Various methods of describing the aortic transvalvular gradient. (From Bashore TM: Invasive cardiology: principles and techniques, Philadelphia, 1990, BC Decker, p. 258.)
8. Which patients should be premedicated to prevent allergic reactions to iodine-based contrast?
In patients with a history of prior true allergic reaction (e.g., hives, urticaria, bronchoconstriction) to iodine-based contrast, the risk of repeat anaphylactoid reaction to contrast agents is reported to be 17% to 35%. Such patients should be premedicated before angiography. The usual regimen is 60 mg orally (PO) of prednisone the night before and morning of the procedure and 50 mg oral diphenhydramine the morning of the procedure. There is actually a surprising dearth of data supporting the belief that previous adverse reactions to shellfish or seafood are associated with increased risk of future anaphylactoid reactions to iodine-based contrast.
9. 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. Preprocedure and postprocedure hydration is the most established method of reducing the risk of contrast nephropathy. Regimens vary, but one suggested regimen is ½ normal saline at 1 ml/kg of body weight beginning 12 hours preprocedure and continuing until 12 hours postprocedure. Acetylcysteine (Mucomyst) probably has at best modest protective effects (if any at all). However, given its low risk of side effects, many practitioners will use it in high-risk patients. The most common dosing regimen is 600 mg PO twice a day (BID) the day before and day of the procedure. Small studies have suggested that sodium bicarbonate infusion or ultrafiltration may be of benefit in select high-risk patients.
10. What are the major vascular complications with cardiac catheterization?
In general, major vascular complications are uncommon with diagnostic cardiac catheterization and more common with percutaneous coronary intervention, which often requires 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:
- Retroperitoneal hematoma: This should be suspected in cases of flank, abdominal, or back pain, with unexplained hypotension, or with a marked decrease in hematocrit. Diagnosis is by computed tomography (CT) scan.
- Pseudoaneurysm: A pseudoaneurysm results from the failure of the puncture site to seal properly. Pseudoaneurysm is a communication between the femoral artery and the overlying fibromuscular tissue, resulting in a blood-filled cavity. Pseudoaneurysm is suggested by the finding of groin tenderness, palpable pulsatile mass, or new bruit in the groin area. Pseudoaneurysm is diagnosed by Doppler flow imaging.
- Arterovenous (AV) fistula: An AV fistula can result from sheath-mediated communication between the femoral artery and the femoral vein. AV fistula is suggested by the presence of a systolic and diastolic bruit in the groin area. Diagnosis is confirmed by Doppler ultrasound.
- Stroke: Stroke may be due to many factors. A proportion of strokes may be due to embolization of atherosclerotic material in the aorta.
- Cholesterol Emboli Syndrome: This is a rare and potentially catastrophic complication that results from plaque disruption in the aorta, with distal embolization in to the kidneys, lower extremities, and other organs.
11. What is intracardiac echo?
Intracardiac echo (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 electrophysiolgocial procedures, imaging the fossa ovalis and pulmonary veins.
