Cardiac catheterization can be used to do various tests, including
These tests define coronary artery anatomy, cardiac anatomy, cardiac function, and pulmonary arterial hemodynamics to establish diagnoses and help select treatment.
Cardiac catheterization is also the basis for several therapeutic interventions (see Percutaneous Coronary Interventions).
Procedure
Patients must fast for 4 to 6 hours before cardiac catheterization. Most patients do not require overnight hospitalization unless a therapeutic intervention is also done.
Left heart catheterization
Left heart catheterization is most commonly used to assess
Left heart catheterization is also used to assess
The procedure is done via femoral, subclavian, radial, or brachial artery puncture, with a catheter passed into the coronary artery ostia and/or across the aortic valve into the left ventricle (LV).
Catheterization of the left atrium (LA) and LV is occasionally done using transseptal perforation during right heart catheterization.
Right heart catheterization
Right heart catheterization is most commonly used to assess
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Right atrial pressure
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Right ventricular pressure
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Pulmonary artery pressure
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Pulmonary artery occlusion pressure (PAOP—see figure Diagram of the cardiac cycle)
PAOP approximates left atrial and left ventricular end-diastolic pressure. In seriously ill patients, PAOP helps assess volume status and, with simultaneous measurements of cardiac output, can help guide therapy.
Right heart catheterization is also useful for assessing cardiac filling pressures, pulmonary vascular resistance, tricuspid or pulmonic valve function, intracardiac shunts, and right ventricular pressure.
Right heart pressure measurements may help in the diagnosis of cardiomyopathy, constrictive pericarditis, and cardiac tamponade when noninvasive testing is nondiagnostic, and it is an essential part of the assessment for cardiac transplantation or mechanical cardiac support (eg, use of a ventricular assist device).
The procedure is done via femoral, subclavian, internal jugular, or antecubital vein puncture. A catheter is passed into the right atrium, through the tricuspid valve, into the right ventricle, and across the pulmonary valve into the pulmonary artery.
Selective catheterization of the coronary sinus can also be done.
Diagram of the cardiac cycle, showing pressure curves of the cardiac chambers, heart sounds, jugular pulse wave, and the ECG
Specific Tests During Cardiac Catheterization
Angiography
Injection of radiopaque contrast agent into coronary or pulmonary arteries, the aorta, and cardiac chambers is useful in certain circumstances. Digital subtraction angiography is used for nonmoving arteries and for chamber cineangiography.
Coronary angiography via left heart catheterization is used to evaluate coronary artery anatomy in various clinical situations, as in patients with suspected coronary atherosclerotic or congenital disease, valvular disorders before valvular replacement, or unexplained heart failure.
Pulmonary angiography via right heart catheterization can be used to diagnose pulmonary embolism. Intraluminal filling defects or arterial cutoffs are diagnostic. Radiopaque contrast agent is usually selectively injected into one or both pulmonary arteries and their segments. However, computed tomographic pulmonary angiography (CTPA) has largely replaced right heart catheterization for diagnosis of pulmonary embolism.
Aortic angiography via left heart catheterization is used to assess aortic regurgitation, coarctation, patent ductus arteriosus, and dissection.
Ventriculography is used to visualize ventricular wall motion and ventricular outflow tracts, including subvalvular, valvular, and supravalvular regions. It is also used to estimate severity of mitral valve regurgitation and determine its pathophysiology. After left ventricular mass and volume are determined from single planar or biplanar ventricular angiograms, end-systolic and end-diastolic volumes and ejection fraction can be calculated.
Coronary artery flow measurements
Coronary angiography shows the presence and degree of stenosis but not the functional significance of the lesion (ie, how much blood flows across the stenosis) or whether a specific lesion is likely to be causing symptoms.
Extremely thin guidewires are available with pressure sensors or Doppler flow sensors. Data from these sensors can be used to estimate coronary artery blood flow, which is expressed as fractional flow reserve (FFR). FFR is the ratio of maximal flow through the stenotic area to normal maximal flow; an FFR of < 0.75 to 0.8 is considered abnormal.
These flow estimates correlate well with the need for intervention and long-term outcome; patients with lesions with FFR > 0.8 do not seem to benefit from placement of a stent. These flow measurements are most useful with intermediate lesions (40 to 70% stenosis) and with multiple lesions (to identify those that are clinically most significant).
Intravascular ultrasonography (IVUS)
Optical coherence tomography (OCT)
Optical coherence tomography is an optical analog of intracoronary ultrasound imaging that measures the amplitude of backscattered light to determine the temperature of coronary plaques and can help determine whether lesions are at high risk of future rupture (leading to acute coronary syndromes).
Tests for cardiac shunts
Measuring blood oxygen content at successive levels in the heart and great vessels can help determine the presence, direction, and volume of central shunts. The maximal normal difference in oxygen content between structures is as follows:
If the blood oxygen content in a chamber exceeds that of the more proximal chamber by more than these values, a left-to-right shunt at that level is probable. Right-to-left shunts are strongly suspected when LA, LV, or arterial oxygen saturation is low (≤ 92%) and does not improve when pure oxygen (fractional inspirational O2 = 1.0) is given. Left heart or arterial desaturation plus increased oxygen content in blood samples drawn beyond the shunt site on the right side of circulation suggests a bidirectional shunt.
Measurement of cardiac output and flow
Cardiac output (CO) is the volume of blood ejected by the heart per minute (normal at rest: 4 to 8 L/minute). Techniques (see table Cardiac Output Equations) used to calculate CO include
Cardiac Output Equations
With the Fick technique, CO is proportional to oxygen consumption divided by arteriovenous oxygen difference.
Dilution techniques rely on the assumption that after an indicator is injected into the circulation, it appears and disappears proportionately to CO.
Usually, CO is expressed in relation to body surface area (BSA) as the cardiac index (CI) in L/minute/m2 (ie, CI = CO/BSA—see table Normal Values for Cardiac Index and Related Measures). BSA is calculated using DuBois height (ht)–weight (wt) equation:
Normal Values for Cardiac Index and Related Measurements
Endomyocardial biopsy
Endomyocardial biopsy helps assess transplant rejection and myocardial disorders due to infection or infiltrative diseases. The biopsy catheter (bioptome) can be passed into either ventricle, usually the right. Three to 5 samples of myocardial tissue are removed from the septal endocardium. The main complication of endomyocardial biopsy, cardiac perforation, occurs in 0.3 to 0.5% of patients; it may cause hemopericardium leading to cardiac tamponade. Injury to the tricuspid valve and supporting chordae may also occur and can lead to tricuspid regurgitation.
Contraindications to Cardiac Catheterization
Relative contraindications to cardiac catheterization include
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Fever
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Systemic infection
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Uncontrolled arrhythmia
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Uncontrolled hypertension
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Uncompensated heart failure
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Radiopaque contrast agent allergies in patients who have not been appropriately premedicated
Relative contraindications balance the urgency of the procedure (eg, in an acute myocardial infarction vs an elective case) and the severity of the contraindicating disorder. Periprocedural management of anticoagulants or antiplatelet drugs is individualized based on the type of procedure (ie, arterial vs venous access), the urgency of the procedure, the indication for the drug, and the patient's risk of bleeding. Catheterization laboratories frequently have policies for the periprocedural management of these drugs.
Complications of Cardiac Catheterization
The incidence of complications after cardiac catheterizations ranges from 0.8 to 8%, depending on patient factors, technical factors, and the experience of the operator. Patient factors that increase risk of complications include
Most complications are minor and can be easily treated. Serious complications (eg, cardiac arrest, anaphylactic reactions, shock, seizures, renal toxicity) are rare. Mortality rate is 0.1 to 0.2%. Myocardial infarction (0.1%) and stroke (0.1%) may result in significant morbidity. Incidence of stroke is higher in patients > 80 years.
In general, complications involve
Contrast agent complications
Injection of radiopaque contrast agent produces a transient sense of warmth throughout the body in many patients. Tachycardia, a slight fall in systemic pressure, an increase in cardiac output, nausea, vomiting, and coughing may occur. Rarely, bradycardia occurs when a large amount of a contrast agent is injected; asking the patient to cough often restores normal rhythm.
More serious reactions (see also Radiographic Contrast Agents and Contrast Reactions) include
Allergic reactions may include urticaria and conjunctivitis, which usually respond to diphenhydramine 50 mg IV. Anaphylaxis, with bronchospasm, laryngeal edema, and dyspnea are rare reactions; they are treated with inhaled albuterol or subcutaneous 1:1000 epinephrine 0.3 to 0.4 mL. Anaphylactic shock is treated with epinephrine and other supportive measures. Patients with a history of allergic reaction to contrast may be premedicated with prednisone (50 mg orally 13 hours, 7 hours, and 1 hour before injection of contrast) and diphenhydramine (50 mg orally or IM 1 hour before the injection). If patients require imaging immediately, they can be given diphenhydramine 50 mg orally or IM 1 hour before injection of contrast and hydrocortisone 200 mg IV every 4 hours until imaging is completed.
Contrast nephropathy is defined as impairment of renal function (either a 25% increase in serum creatinine from baseline or a 0.5 mg/dL [44 micromole/L] increase in absolute value) within 48 to 72 hours of IV contrast administration. For patients at risk, use of lowest possible dose of low-osmolar or iso-osmolar contrast, avoidance of multiple contrast studies within a short period of time, and infusion of a total 10 to 15 mL/kg normal saline IV beginning 4 to 6 hours before angiography and 6 to 12 hours afterward reduces this risk substantially. In patients at risk of impaired renal function, assess serum creatinine 48 hours after injection of contrast.
Catheter-related complications
If the catheter tip contacts the ventricular endocardium, ventricular arrhythmias commonly occur, but ventricular fibrillation is rare. If it occurs, direct current cardioversion (DC cardioversion) is administered immediately.
Disruption of an atherosclerotic plaque by the catheter can release a shower of atheroemboli. Emboli from the aorta may cause stroke or nephropathy. Emboli from proximal to distal coronary arteries may cause myocardial infarction.
Coronary artery dissection is also possible.
Access site complications
Access site complications include
Bleeding from the access site may occur and usually resolves with compression. Mild bruises and small hematomas are common and do not require specific investigation or treatment.
A large or enlarging lump should be investigated using ultrasonography to distinguish hematoma from pseudoaneurysm. A bruit at the site (with or without pain) suggests an AV fistula, which can be diagnosed using ultrasonography. Hematomas usually resolve with time and do not require specific therapy. Pseudoaneurysms and AV fistulas usually resolve with compression; those that persist may require surgical repair.
Radial artery access is in general more comfortable for the patient and carries a much lower risk of hematoma or pseudoaneurysm or AV fistula formation when compared with femoral artery access.
