1. d. The only absolute contraindication to cardiac catheterization is a patient’s refusal to undergo the procedure. Acute renal failure, decompensated congestive heart failure, and severe hypokalemia are all relative contraindications. The risks and potential benefits for cardiac catheterization should be assessed prior to pursuing the procedure in these circumstances. Additional scenarios that pose an increased risk of cardiac catheterization include active bleeding, acute stroke, malignant hypertension, untreated active infection, digitalis toxicity, aortic valve endocarditis, severe anemia or coagulopathy, and reduced life expectancy.

2. b. Metformin should be held the day prior to the procedure and restarted 2 days after the procedure if renal function remains unchanged. Metformin is eliminated primarily via the kidneys and therefore accumulates among patients with renal insufficiency (glomerular filtration rate <70 mL/min, or serum creatinine >1.6 mg/dL). Contrast media can impair renal function and lead to further retention of metformin, which is known to precipitate the onset of lactic acidosis. The incidence of lactic acidosis associated with metformin, regardless of exposure to contrast media, is 0.03 cases per 1,000 patients per year, and 50% result in death. There is no conclusive evidence to indicate that contrast media precipitates the development of metformin-induced lactic acidosis among patients with normal serum creatinine (<1.5 mg/dL). This complication is almost exclusively observed among non-insulin dependent diabetic patients with abnormal renal function before injection of contrast media.

In patients who are candidates for percutaneous coronary intervention after diagnostic angiography, aspirin 325 mg should be administered on the day of the procedure. The use of clopidogrel (600 mg loading dose) prior to catheterization may be indicated in patients who are likely to undergo percutaneous coronary intervention. This must be weighed against the possibility that they will require coronary artery bypass graft surgery, which often must be postponed for several days after administration of clopidogrel. Warfarin should be stopped several days before the procedure. Ideally, the international normalized ratio should be less than 1.5 to 1.8 prior to catheterization, depending on operator comfort and acuity of the indication. Heparin (3,000 to 5,000 units IV) should be considered for patients undergoing cardiac catheterization via an arm approach. It is also reasonable to pursue cardiac catheterization in patients on unfractionated heparin; however, great care must be taken to achieve an anterior artery wall arteriotomy in order to minimize the risk of bleeding.

3. False. Renal dysfunction can result from administration of contrast agents, which is reported to occur in approximately 5% patients, or from renal athero-embolic disease, which is significantly less common. Renal atheroembolic disease complicates approximately 0.15% of cardiac catheterizations and should be suspected when acute renal failure occurs in conjunction with other clinical signs of embolization such as discolored toes, livedo reticularis, systemic or urinary eosinophilia, and abdominal pain.

4. False. A great deal of controversy exists regarding the exact mechanism of contrast reactions, but it is thought that the majority of reactions are not mediated by immunoglobin E, and thus are not truly allergic. Multiple investigators have demonstrated conclusively, however, that immediate reactions involve the granular release of histamine by mast cells and basophils, producing an anaphylactoid response. Regardless of the mechanism, the risk of a reaction to contrast is increased twofold in patients with a strong history of allergy or atopy such as asthma. A common misconception is that a prior reaction to seafood confers a greatly elevated risk of an adverse reaction with contrast exposure. In reality, patients with allergies to seafood have a similar risk of contrast reactions as those who have a strong history of other allergic reactions. Patients with a previous adverse reaction to contrast have about a sixfold increased risk of an adverse reaction upon repeat exposure to contrast when compared with individuals without a prior adverse reaction. This elevated risk justifies pharmacologic prophylaxis with steroids and histamine blockade prior to planned repeat contrast exposure for patients with a history of moderate or severe reactions, although it should be noted that data is very limited on the efficacy of these preventive pharmacologic measures when modern-day nonionic low osmolar contrast media (LOCM) or iso-osmolar contrast media (IOCM) is used. Physicians should also note that serious life-threatening reactions have been reported despite the use of steroid and antihistamine prophylaxis.

5. c. The main source of radiation exposure for the operator is scatter from the patient. A secondary, less significant, source is escape of x-rays through the shielding of the x-ray tube. Protection for the operator consists of shielding, proper positioning from the radiation source, and adjusting the fluoroscopic controls in an attempt to minimize radiation exposure while maintaining a high-quality image.

6. d. Personal shielding involves lead aprons, thyroid collars, and lead glasses. Lead aprons should have shielding properties equivalent to 0.5 mm of lead, which shields the covered areas of the operator from roughly 90% of scatter radiation. Lead glasses protect the operator from possible radiation-induced cataracts and should have side shields to decrease radiation from the lateral direction. Thyroid shields prevent large cumulative doses of radiation that could lead to thyroid cancer. These items should be checked annually with fluoroscopy to inspect for possible cracks, holes, and other signs of deterioration. The catheterization table will commonly have two lead shields: one which is a table side drape that protects the lower body of the operator, and one which is an adjustable lead acrylic shield that is suspended from the ceiling to aid in the protection of the operator’s head and upper torso.

The inverse square law addresses the important concept that radiation dose drops rapidly by the inverse square of the relative increase of distance from the radiation source. Operators can decrease their radiation exposure by taking a step back from the irradiated area before engaging in fluoroscopy. Moving the image intensifier, which is located above the patient, to as close to the patient as possible also reduces scatter radiation by reducing geometric magnification (radiation dose usually increases with the square of the magnification). Placing hands in the direct beam of radiation should only be done in cases of emergency.

Modifying fluoroscopic controls can also decrease radiation exposure for both the operator and the patient; however, these modifications may occasionally reduce image quality. One of the “golden rules” for minimizing radiation exposure is keeping beam-on time to an absolute minimum. Fluoroscopy or cineangiography should not be engaged if the image on the monitor is not being used. Most fluoroscopic machines have an option that allows the operator to select the level of image quality (low, normal, high). Low image quality reduces radiation dose rate, but often produces a noisy image. These images may be acceptable in certain situations such as checking position of a guidewire or catheter. Most fluoroscopic machines have pulsed fluoroscopy which results in x-rays being produced in short bursts instead of a continuous stream as in conventional fluoroscopy. Reducing the pulse frequency to 15 or 7.5 pulses of x-rays/second will reduce radiation exposure at the cost of producing a somewhat flickering, choppy image. A similar result is seen when one reduces the cine frame rate. Applying collimators (blades outside the x-ray tube that block x-rays) to the area of interest not only reduces scatter radiation to the operator but also improves image quality.

7. e. The posterior descending artery, which courses in the posterior interventricular groove, determines coronary dominance. In 85% of the cases, the posterior descending artery arises from the right coronary artery, making the coronary circulation right-dominant. In 7% of the cases, the circulation is codominant, with the posterior interventricular groove being supplied by both the right coronary artery and the left circumflex coronary artery. In 8% of the cases, the posterior descending artery arises from the left circumflex, making it the dominant artery.

8. e. A dampened pressure waveform (drop in the catheter tip systolic pressure) or a ventricularized pressure waveform (drop in the catheter tip diastolic pressure) usually indicates that the catheter tip is either deep-seated, restricting coronary inflow, or the tip is against the wall. It also indicates the possibility of significant left main stenosis. This can be a dangerous situation that needs to be recognized quickly. The catheter tip should be immediately withdrawn from the ostium. The ostium can be re-engaged cautiously. If a small injection of dye reveals significant ostial left main stenosis (another clue may be the absence of dye reflux into the aortic root with the injection), two short cine runs aimed at visualizing distal targets for bypass surgery should promptly be performed, and the catheter then immediately pulled back from the ostium. Care must be taken to avoid multiple engagements of the left main trunk as this can lead to abrupt vessel closure. In cases where significant left main trunk stenosis is suspected, the operator can take nonselective angiograms of the left main trunk by injecting dye with the catheter tip positioned in left sinus. Catheter damping may also be seen in cases of spasm of the left main trunk. In such instances, intracoronary nitroglycerin can be injected (200 μg) and follow-up picture can be taken to document relief of spasm.

9. a. To minimize the risk of coronary dissection when using the Amplatz catheters, the operator should rotate the catheter counterclockwise to disengage it from the coronary ostium prior to removing the catheter. Withdrawing the Amplatz catheters straight back will cause the catheter to “dive” into the coronary artery and increase the risk of dissection.

10. g. The various coronary anomalies in order of frequency are as follows: left anterior descending and left circumflex arteries arising from separate ostia (0.5%); origin of the left circumflex coronary artery from the right sinus of Valsalva (0.5%); origin of the right coronary artery from the ascending aorta above the right sinus of Valsalva (0.2%); origin of the right coronary artery from the left sinus of Valsalva (0.1%); AV fistula (0.1%); origin of the left main trunk from the right sinus of Valsalva (0.02%).

11. d. The Hakki formula calculates valve area (in cm²) by dividing the cardiac output (in L/min) by the square root of the peak pressure gradient across the valve (in mm Hg). This method does not require the assessment of the systolic ejection time or the transvalvular flow, and the peak systolic gradient instead of the mean gradient may be entered into the formula. However, in the presence of tachycardia, the formula is less accurate because the percentage of time/minute in systole and diastole changes markedly at higher heart rates. In order to account for this, the result should be divided by 1.35 for heart rates >90 (Angel adjustment).

12. b. The Fick principle assumes that the rate at which oxygen is consumed is a function of the rate of blood flow and the rate of oxygen pick up by the red blood cells. In the cath lab, it is used to determine cardiac output by the difference in oxygen concentration in blood before it enters and after it leaves the lungs, and from the rate at which oxygen is consumed. Three variables need to be identified:

From these, cardiac output can be calculated:

CO = O₂ Uptake / ([Arterial O₂] – [Venous O₂])

While considered to be the most accurate method for cardiac output measurement, Fick measurement is invasive, requires time, and the attainment of reliable oxygen samples. Quantitative ventriculography is a rather crude estimation of cardiac output and is infrequently used. Pulmonary artery thermodilution calculates cardiac output by quantifying a “temperature curve”; a small amount (typically 10 mL) of cold saline is injected into the pulmonary artery and the temperature a known distance away (6 to 10 cm) is attained, using the same catheter. Higher cardiac outputs will change the temperature rapidly, whereas lower cardiac outputs will change the temperature slowly. The technique is liable to gross errors unless certain requirements are strictly adhered to, and in certain clinical circumstances.

13. d. Mixed venous blood in a well patient at rest is about 75% saturated, which indicates that under normal conditions tissues extract 25% of the oxygen delivered. In general, any clinical condition which leads to an Svo₂ <60% threatens tissue oxygenation, and an Svo₂ <30% should be viewed as a medical emergency. True mixing of venous blood (in the absence of shunt) occurs in the pulmonary artery; therefore, slow aspiration from the distal lumen of a pulmonary artery catheter can provide a sample.

14. e. Other relative contraindications include decompensated heart failure, presence of left ventricular thrombus, acute coronary syndrome, mechanical aortic prosthesis, or endocarditis of left-sided valves. For all these reasons, ventriculography is more sparingly performed, especially given the myriad other noninvasive imaging options available.

15. b. The balloon should be inflated either in the terminal end of the inferior vena cava, or in the right atrium. In the femoral vein, the balloon or vein might be traumatized due to the relatively narrow diameter. The balloon should always be inflated before entering the right ventricle in order to reduce the risk of ventricular ectopy or free wall perforation.

16. a. The LAO projection is ideal for visualizing and “opening” the aortic arch, thereby delineating the origins of the innominate, left carotid, and left subclavian arteries. It is also useful for identifying the origin and extent of type A aortic dissection. The RAO view can be particularly useful when searching for aorto-coronary bypass grafts to the left coronary system.

17. b. Dyskinetic wall motion refers to paradoxical wall motion during systole. Aneurysmal dyskinesis is frequently appreciated after a transmural myocardial infarction and is a particular risk for development of mural thrombus. With time, dyskinetic injury will heal into akinetic scar.