Introduction

An understanding of the anatomy, physiology, and alternative treatment strategies for congenital heart defects is essential to provide the appropriate patient care. This includes an understanding of the guideline recommendations and the natural history of congenital heart defects. This knowledge is required to determine if there is an indication for treatment of these conditions. Pediatric and adult congenital heart patients offer distinct challenges, such as unusual cardiovascular anatomy and deranged or surgically corrected physiology, and for older patients there are demands such as pregnancy and exercise tolerability not found in traditional patients.

Diagnostic cardiac catheterization for children with heart disease and adults with congenital heart disease is the practice of percutaneous catheter-based techniques to assess cardiovascular hemodynamics and anatomy. Real-time fluoroscopy with contrast injection coupled with rapid digital angiography provides high-resolution images of the heart that are necessary for successful management decisions. In addition, the direct measurement of pressures within the cardiovascular system enhances the treatment of heart disease for this patient population by streamlining medical treatment options and defining surgical and interventional indications.

This chapter reviews current indications and best practice guidelines by proceeding through the diagnostic cardiac catheterization procedure from beginning to end in the order of anatomic structures evaluated.

Historical Background

In 1628 the court physician to James I and Charles I of England, Dr. William Harvey, presented the “movement of the heart and blood” in an experiment on a deer. He used his experiments and deductive logic to conclude that blood was pumped by the heart through systemic and pulmonary circulations. These experiments confirmed unidirectional blood flow in the blood vessels. In 1929 Werner Forssmann of Germany demonstrated on himself the ability to move a urethral catheter into his basilic vein in his left arm to his heart. He then walked to radiology and made an x-ray to prove the catheter course. After this report he was fired by his chief of surgery who said “for a real surgeon, there is only one thing, to operate, to operate, to operate.” Ultimately, he was awarded the Nobel Prize in 1956.

Over the next 6 decades, the field of structural and congenital cardiac catheterization evolved into primarily an interventional discipline. Accordingly, diagnostic cardiac catheterization evolved to mostly the preintervention evaluation and assessment. Meanwhile, the pure diagnostic cardiac catheterization regressed to a limited and select patient group. Currently the diagnostic cardiac catheterization and percutaneous interventional procedures are not mutually exclusive. It is currently recommended that percutaneous interventions are preceded by a diagnostic evaluation that most often determines the indications for that intervention (class I; level of evidence: A). Consequently, assessment of patient hemodynamics and, when necessary, assessment of anatomy by angiography should be accomplished before the interventional cardiac catheterization to confirm congenital or acquired heart disease in infants and children, as well as adults with congenital heart defects.

On the other hand, most pure diagnostic cardiac catheterizations will often include preprocedure discussions regarding potential interventions if indications for an interventional procedure are met during the diagnostic evaluation. Consequently, both the procedural preapproval process and the informed consent process for most diagnostic cardiac catheterizations include consent for any possible intervention. This is essential in the management of children but even more so for older children and adults where assent and consent from the patient is mandatory prior to sedatives. This preparation will allow congenital heart patients, who have often already undergone multiple procedures, to avoid more than one anesthetic to accomplish the clinical management deemed necessary during the diagnostic cardiac catheterization evaluation.

The Society of Cardiac Angiography and Interventions recognizes the importance of advanced training in pediatric and congenital interventional cardiac catheterization and recommends the development of guidelines and assessment tools for such programs. The society states that it is important for pediatric cardiologists who wish to perform cardiac catheterizations to become proficient in all aspects of cardiac catheterization through at least one additional year of advanced training. Individuals in these programs should perform procedures of gradually increasing complexity under the supervision of an attending interventional cardiologist until they become competent as the sole or primary operator. Mastery of the diagnostic component of this training will lead to successful interventions following appropriate guidelines and recommendations and lower the adverse event risk.

Preprocedure Considerations

Diagnostic cardiac catheterization should not be considered routine for the diagnosis of congenital heart defects because the performance of complete right- and left-sided heart studies may subject patients to unnecessary risk and exposure to radiation. Complete cardiac echocardiographic imaging or alternative noninvasive imaging modalities such as cardiac magnetic resonance imaging (CMRI) or chest and cardiovascular computed tomography (CT) are indicated before invasive cardiac catheterization to facilitate planning of diagnostic data collection and performance of an intervention (class I; level of evidence: A).

Diagnostic cardiac catheterization has been impacted by advances in noninvasive imaging because it is no longer indicated in the routine preoperative evaluation of most congenital defects, such as atrial septal defect, complete or partial atrioventricular canal defect, ventricular septal defect (VSD), double-outlet right ventricle (RV), tetralogy of Fallot (TOF), TOF with pulmonary atresia, coarctation of the aorta, hypoplastic left heart syndrome, or any of the cyanotic neonatal heart defects. Details of anatomy, including situs, systemic and pulmonary connections, septal structure, severity of atrioventricular and semilunar valve function, coronary artery attachments and course, and aortic arch anatomy, are certainly established with noninvasive imaging to the degree of certainty required for surgical intervention.

In most instances, the 2011 indications for diagnostic cardiac catheterization were developed empirically, with no prospective trials, controlled or otherwise, that would validate superiority of cardiac catheterization over noninvasive diagnostic modalities. Therefore most indications are supported by patient series, retrospective case reviews, or the opinion of authorities (level of evidence: C). Most important, diagnostic cardiac catheterization should be considered only when the patient’s congenital heart anatomy and physiology are inadequately defined by modern noninvasive methods such as two-dimensional (2D) or 3D echocardiography, cardiovascular CT, or CMRI.

Diagnostic Catheterization Recommendations

Potential Adverse Events

The diagnostic cardiac catheterization provides accurate physiologic and anatomic information to the care of congenital heart patients but is not without risk. The following are potential adverse events associated with a diagnostic cardiac catheterization:

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  Risk of general anesthesia or sedation-related changes to the cardiovascular physiology.

  
  
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  Allergic reactions to medications, anesthetics, or contrast agent.

  
  
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  Latex allergy occurs uncommonly in the modern “latex-free” catheterization laboratories. If an allergic reaction occurs, there is a wide range of symptomatology, including urticarial to anaphylaxis; thus protocols are used for high-risk patients or patients with previous allergic history. There are no reports of this occurring with the use of catheters.

  
  
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  Hypothermia, especially in the neonates and infants.

  
  
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  Aggravation of hypoxia or hypoxemia secondary to medications and sedation.

  
  
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  Arrhythmias—atrial flutter, atrial fibrillation, ventricular arrhythmias, and heart block.

  
  
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  Peripheral vascular injury, cardiac perforation, and cardiac valve injury.

  
  
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  Blood loss that requires transfusion.

  
  
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  Renal insufficiency and injury secondary to contrast agent administration.

  
  
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  Diffuse central nervous system injury, embolic events, stroke, and mortality.

  
  
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  Exposure to ionized radiation, especially for patients requiring multiple procedures.

Safety and Quality Control

Most congenital catheterization labs in the United States have voluntary reporting of their procedural and safety data into the IMPACT (Improving Pediatric and Adult Congenital Treatment) database. This collects data about the patient, procedure type, outcome, and complications. The data are submitted quarterly to the National Cardiovascular Data Registry/American College of Cardiology and are compared with the other centers nationally. This is published in a way such that the center information is deidentified and that only each individual center can see how they rank among the other programs nationally.

The IMPACT database is the largest voluntary reporting database, but there are other systems such as the CCISC, C3PO, and MAGIC databases.

Aside from national reporting, each individual center offering pediatric and congenital catheterization should report any complications to the hospital monitoring board and division M&M (Mortality and Morbidity) conference. These should be vetted and assessed and severe/catastrophic complications fully evaluated, discussed, and necessary changes in policy/procedure made where appropriate.

Premedication, Sedation, and Anesthesia

For the elective diagnostic cardiac catheterization procedure, general recommendations include no solid food for 8 hours, milk or formula for up to 6 hours, breast milk up to 4 hours, or clear liquids up to 2 hours before initiation of sedation. Premedication is usually administered orally, although for older patients or those requiring preprocedural hydration, intravenous (IV) placement is performed prior to coming into the lab. For younger patients or those with higher level of anxiety, mask induction is often performed in the lab and the IV placed after sedation. Local anesthesia is used often at the percutaneous access site(s), including lidocaine infiltration (maximum 4.5 mg/kg; avoid intravascular injection, and lidocaine buffered with sodium bicarbonate diminishes the discomfort of lidocaine infiltration) and topical anesthetics such as lidocaine 2.5% or prilocaine 2.5%.

Effective sedation and analgesia are maintained using agents with consideration for the individual patient’s cardiovascular condition. Often patients with ventricular dysfunction need to avoid cardiac depressant agents such as propofol, and at times agents that maintain or increase systemic vascular resistance, such as ketamine, are useful.

Vascular Access

Vascular access is most commonly obtained in the femoral system using the Seldinger technique and ultrasound guidance. The right heart catheterization can be performed through the inferior vena cava (IVC) and the left heart catheterization through either antegrade also from the IVC through an existing congenital opening or retrograde from the femoral artery. The internal jugular vein is the most common access site when bilateral femoral veins are obstructed, there is Glenn physiology, or the IVC is interrupted. The internal jugular approach is either a high or standard entry or a low approach superior-inferior to the clavicular grove lateral from the supraclavicular notch. The low approach is mainly reserved for mid-internal jugular occlusion such as with patients with a history of vascular extracorporeal membrane oxygenation support via the neck. The subclavian approach is often used when there is internal jugular occlusion or as a primary access site if the postprocedure plan is to place a subclavian Broviac for long-term management. Other access options include umbilical artery and vein in neonates, axillary or carotid artery when femoral approach is nonconductive, and the transhepatic approach described in the mid-1990s.

For the transhepatic approach, a long 21- or 22-gauge needle with an obturator is most commonly used with a puncture along the mid to anterior axillary line. The needle can be guided by fluoroscopy and/or ultrasound toward the IVC and right atrial junction in a posteriorly, superiorly, and medially. The obturator is removed, and diluted (10% to 15%) contrast is injected during withdrawal until the hepatic vein is identified. Subsequently, the wire is advanced and the sheath placed is determined. Post procedure the track can be closed with a coil, plug, or device of preference, or the track can be rewired for placement of a transhepatic Broviac.

Catheters, Wires, Equipment

The cardiologist needs to have an understanding of and familiarity with the different catheters and wires available in the cardiac catheterization laboratory. Catheters are hollow, thus allowing blood sampling, transmission of pressure, and injection of contrast. These catheters can be classified as end-hole, side-hole, or both. Angiographic injections are primarily performed using catheters with a side-hole(s) to prevent vascular injury during the injection. Catheters may be straight, angled, or shaped either out of the package or by the physician using a wire or tip deflector apparatus.

Hemodynamic Variables

To calculate pulmonary and systemic shunt volume and resistance, the initial measurement during a diagnostic cardiac catheterization is cardiac output ( Box 17.1 ). This cannot be measured directly; thus it is estimated by using an indicator dilution technique described by Fick. Oxygen, a common indicator used to calculate cardiac output, is carried in the blood stream attached to hemoglobin (Hgb) and dissolved in plasma. As the patient breathes room air, the vast majority of the oxygen in the blood is bound to Hgb. The amount of dissolved oxygen in the plasma (CdO ₂ ) is directly proportional to the partial pressure of oxygen (PaO ₂ ) know as Henry’s law. The CdO ₂ can be calculated using the solubility coefficient of oxygen at body temperature, and the PaO ₂ . At 37°C (the normal body temperature), the amount of oxygen dissolved in blood is 0.03 mL/mm Hg per liter or 0.003 mL/mm Hg per deciliter. Thus in blood with a PaO ₂ of 100 mm Hg, there is 3 mL of dissolved oxygen per liter of blood and 0.3 mL of dissolved oxygen per deciliter of blood. This amount of oxygen is trivial compared with the oxygen bound to Hgb; thus it is usually ignored in hemodynamic calculations. However, if the patient is on supplemental oxygen, and the PaO ₂ is greater than 100 mm Hg, then the dissolved oxygen is considered for an accurate calculation. To calculate the oxygen capacity that is the amount of oxygen bound to Hgb in the blood, we multiply (Hgb in g/dL) × (1.36 mL O ₂ /g of Hgb) × (10 dL/L) = the mL O ₂ /L of blood.