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Cardiac Catheterization

By Michael J. Shea, MD, University of Michigan Health Systems

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Cardiac catheterization is the passage of a catheter through peripheral arteries or veins into cardiac chambers, the pulmonary artery, and coronary arteries and veins.

Cardiac catheterization can be used to do various tests, including

  • Angiography

  • Intravascular ultrasonography

  • Measurement of cardiac output (CO)

  • Detection and quantification of shunts

  • Endomyocardial biopsy

  • Measurements of myocardial metabolism

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 be npo for 4 to 6 h 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

  • Cardiac anatomy

Left heart catheterization is also used to assess

  • Aortic blood pressure

  • Systemic vascular resistance

  • Aortic valve function

  • Mitral valve function

  • Left ventricular pressure and function

The procedure is done via femoral, subclavian, radial, or brachial artery puncture, with a catheter passed into the coronary artery ostia or across the aortic valve into the 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

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 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 RA, through the tricuspid valve, into the RV, 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.

The phases of the cardiac cycle are atrial systole (a), isometric contraction (b), maximal ejection (c), reduced ejection (d), protodiastolic phase (e), isometric relaxation (f), rapid inflow (g), and diastasis, or slow LV filling (h). For illustrative purposes, time intervals between valvular events have been modified, and the z point has been prolonged.

AO = aortic valve opening; AC = aortic valve closing; LV = left ventricle; LA = left atrium; RV = right ventricle; RA = right atrium; MO = mitral valve opening.

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.

Ventriculographyis 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 severity and determine its pathophysiology. After LV mass and volume are determined from single planar or biplanar ventricular angiograms, end-systolic and end-diastolic volumes and ejection fraction can be calculated.

Intravascular ultrasonography

Miniature ultrasound transducers on the end of coronary artery catheters can produce images of coronary vessel lumina and walls and delineate blood flow. This technique is being increasingly used at the same time as coronary angiography.

Optical coherence tomography

Optical coherence tomography (OCT) 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:

  • The pulmonary artery and right ventricle: 0.5 mL/dL

  • The right ventricle and right atrium: 0.9 mL/dL

  • The right atrium and superior vena cava: 1.9 mL/dL

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/min). Techniques used to calculate CO include.

  • Fick cardiac output technique

  • Indicator-dilution technique

  • Thermodilution techniques (see Table: Cardiac Output Equations)

Cardiac Output Equations

Fick technique

equation

Numerator is O2 absorbed by lungs (mL/min).

Indicator-dilution technique

equation

Denominator is the sum of dye concentrations (C) at each time interval (t).

Thermodilution technique

equation

TB – TI is the difference between body and injectate temperatures; injectate is usually dextrose or saline. Denominator is the sum of changes in temperature at each time interval (t).

SaO2 = arterial O2 saturation (%); SvO2= mixed venous O2 saturation (%), measured in the pulmonary artery.

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/min/m2 (ie, CI = CO/BSA—see Table: Normal Values for Cardiac Index and Related Measurements). BSA is calculated using DuBois height (ht)-weight (wt) equation:

equation

Normal Values for Cardiac Index and Related Measurements

Measurement

Normal Value

SD

Oxygen uptake

143 mL/min/m2*

14.3

Arteriovenous oxygen difference

4.1 dL

0.6

Cardiac index

3.5 L/min/m2

0.7

Stroke index

46 mL/beat/m2

8.1

Total systemic resistance

1130 dynes-sec-cm-5

178

Total pulmonary resistance

205 dynes-sec-cm-5

51

Pulmonary arteriolar resistance

67 dynes-sec-cm-5

23

*Varies with body mass index.

SD = standard deviation.

Adapted from Barratt-Boyes BG, Wood EH: Cardiac output and related measurements and pressure values in the right heart and associated vessels, together with an analysis of the hemodynamic response to the inhalation of high oxygen mixtures in healthy subjects. Journal of Laboratory and Clinical Medicine 51:72–90, 1958.

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.

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; lesions with FFR > 0.8 do not seem to benefit from stenting. 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).

Contraindications to Cardiac Catheterization

Relative contraindications to cardiac catheterization include

  • Renal insufficiency

  • Coagulopathy

  • Fever

  • Systemic infection

  • Uncontrolled arrhythmia or hypertension

  • Uncompensated heart failure

  • Radiopaque contrast agent allergies in patients who have not been appropriately premedicated

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

  • Increasing age

  • Heart failure

  • Valvular heart disease

  • Peripheral arterial disease

  • COPD

  • Chronic kidney disease

  • Insulin-dependent diabetes

Most complications are minor and can be easily treated. Serious complications (eg, cardiac arrest, anaphylactic reactions, shock, seizures, cyanosis, 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 yr.

In general, complications involve

  • The contrast agent

  • Effects of the catheter

  • The access site

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 CO, 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-type contrast reactions

  • Contrast nephropathy

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 epinephrine 0.3 to 0.4 mL sc. 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 po 13 h, 7 h, and 1 h before injection of contrast) and diphenhydramine (50 mg po or IM 1 h before the injection). If patients require imaging immediately, they can be given diphenhydramine 50 mg po or IM 1 h before injection of contrast and hydrocortisone 200 mg IV q 4 h 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 increase in absolute value) within 48 to 72 h of IV contrast administration. For patients at risk, use of low-osmolar or iso-osmolar contrast, and infusion of normal saline IV for 4 to 6 h before angiography and 6 to 12 h afterward reduces this risk. In such patients, assess serum creatinine 48 h 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 (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 the coronary arteries may cause myocardial infarction.

Coronary artery dissection is possible.

Access site complications

Access site complications include

  • Bleeding

  • Hematoma

  • Pseudoaneurysm

  • Arteriovenous (AV) fistula

  • Limb ischemia

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.

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* This is the Professional Version. *