Introduction and Indications
Diagnostic cardiac catheterization utilization declined due to high-quality noninvasive imaging (Echocardiography, MRI, CT). Remains crucial for hemodynamic assessment, interventional therapy, and complex anatomic evaluation.
Diagnostic Indications
- Inconsistent or equivocal noninvasive imaging.
- Complex congenital heart disease (CHD) evaluation (e.g., Tetralogy of Fallot with major aortopulmonary collateral arteries [MAPCAs], Pulmonary atresia with intact ventricular septum and coronary sinusoids).
- Hemodynamic assessment (shunt quantification, pulmonary vascular resistance [PVR] calculation).
- Between staged single-ventricle palliations (e.g., pre-Glenn or pre-Fontan evaluation).
- Long-term surveillance post-complex repair.
- Endomyocardial biopsy (cardiomyopathy diagnosis, transplant rejection screening).
- Electrophysiology study (EPS) for arrhythmia evaluation.
Interventional Indications
- Preferred alternative to surgery (patent ductus arteriosus [PDA] closure, atrial septal defect [ASD] closure, balloon valvuloplasty).
- High-risk surgical candidates (e.g., transcatheter superior sinus venosus ASD closure with pulmonary hypertension).
Pre-Procedure Preparation
Clinical Assessment
- Detailed history: Initial and current anatomy, previous surgeries/catheterizations, bleeding disorders, contrast reactions, renal insufficiency.
- Physical examination: Cyanosis, weak pulses, delayed capillary refill.
- Inspection of planned vascular access sites.
- Identification of superficial venous collaterals. Suggests superior vena cava (SVC) obstruction. Alters access plan.
Sedation and Anesthesia
- Goals: Reduce anxiety, promote cooperation, induce amnesia, maintain hemodynamic stability.
- General anesthesia: Preferred in children. Facilitates procedural safety, airway control, immobility for interventions. May alter hemodynamics.
- Local anesthesia (Lidocaine): Frequent burning sensation. Minimize discomfort with small needles (25-gauge), buffering with sodium bicarbonate, prior sedation.
- Ketamine: Increases systemic vascular resistance (SVR). Ideal for Tetralogy of Fallot. Prevents vasodilation and hypercyanotic spells.
- Propofol: Profound negative inotrope. Avoid in systolic dysfunction.
Vascular Access Techniques
Ultrasound (US) guidance routinely utilized. Improves success rate, decreases complications. Essential in small infants and patients with low/absent pulsatility.
| Access Route | Indications & Characteristics |
|---|---|
| Femoral Vein/Artery | Standard approach. “Syringe technique” useful in spontaneous breathing (gentle continuous negative pressure during advancement). Start with smallest sheath (4-5 Fr for diagnostic). Upsize only for intervention. |
| Internal Jugular Vein (IJV) | Right IJV preferred. Provides straight trajectory to heart. Default access if femoral veins occluded. Ideal for right ventricle (RV) endomyocardial biopsy and superior cavopulmonary anastomosis evaluation. |
| Common Carotid/Axillary Artery | Ideal trajectory for PDA stents, aortic balloon valvuloplasty, and modified Blalock-Taussig shunt interventions in small infants. |
| Umbilical Vein | Used in neonates. Straight course. Facilitates balloon atrial septostomy (Rashkind procedure) crossing foramen ovale. |
| Transhepatic | Utilized when bilateral femoral occlusion exists or in interrupted inferior vena cava (IVC). |
Equipment: Catheters and Wires
| Catheter Type | Characteristics & Uses | Examples |
|---|---|---|
| End-Hole | Single distal hole. Measures specific location pressures. Used for selective hand-injection angiograms. Obtains wedge pressures. High risk of wall injury or myocardial staining during power injection. | Berman wedge, Goodale Lubin (GL), Angled glide, Multipurpose, Judkins Right/Left (JR/JL). |
| Multiple-Hole | Multiple distal holes. Accurate pressure measurement even against cardiac walls. Ideal for high-volume, rapid flow rate angiograms. Cannot measure wedge pressures. | Berman angiographic, NIH, Pigtail. |
Hemodynamic Measurements
Crucial for physiological interpretation. Requires measurement of oxygen saturation and pressure recordings.
Pressure Evaluation
- Fluid-filled catheters connected to pressure-sensitive transducers.
- De-air system. Level transducer at mid-left atrium (mid-axillary line) and zero to atmospheric pressure.
- Record pressures at end-expiration (passive inhalation) to mitigate respiratory artifacts.
- Pulmonary Capillary Wedge Pressure (PCWP): Surrogates left atrial (LA) mean pressure. Correlates with left ventricular end-diastolic pressure (LVEDP) in absence of mitral stenosis or pulmonary vein stenosis.
- Peaked ‘a’ wave: Seen in restrictive cardiomyopathy or mitral stenosis.
- Large ‘v’ wave: Seen in mitral regurgitation.
Fick Principle and Flow Calculations
- Calculates cardiac output (Flow) based on oxygen consumption (VO2) and oxygen content difference.
- Pulmonary Blood Flow (Qp) = VO2 / (Pulmonary Vein O2 content - Pulmonary Artery O2 content).
- Systemic Blood Flow (Qs) = VO2 / (Aortic O2 content - Mixed Venous O2 content).
- Superior vena cava (SVC) oxygen saturation commonly used as surrogate for mixed venous oxygen content in left-to-right shunt lesions.
- Dissolved oxygen must be included in calculation if patient receives supplemental oxygen with PaO2 > 100 mmHg.
- Systemic Vascular Resistance (SVR) = (Mean Aorta Pressure - Mean Right Atrium Pressure) / Qs.
Pulmonary Vasoreactivity Testing
- Delineates reversibility of pulmonary arterial hypertension (PAH).
- Testing agents: Nitric oxide (20 ppm for 5 mins), 100% oxygen, or epoprostenol.
- Positive response (Children): >20% decrease in mean pulmonary artery pressure (mPAP) and PVR/SVR ratio without reduction in cardiac output.
Angiocardiography
Provides structural delineation of cardiac chambers and great vessels via contrast injection.
Imaging Modalities
- Fluoroscopy mode: Low radiation dose. Utilized for catheter manipulation. Images not automatically saved.
- Cine acquisition mode: Higher radiation dose. Superior image quality. Automatically stored for review. Reserved for fine detail visualization.
- ALARA principle (As Low As Reasonably Achievable): Default to low-level image intensifier mode. Minimize radiation exposure.
- 3D Rotational Angiography: C-arm spins 180 degrees during continuous contrast injection. Generates 3D volume dataset comparable to CT/MRI. Post-processing allows detailed structural analysis.
Contrast Media Administration
- Hypertonic solutions containing organic iodides.
- Risks: Nausea, renal insufficiency, central nervous system symptoms, allergic reactions.
- Hemodynamic effects: Transient myocardial depression, hypotension, subsequent tachycardia, increased cardiac output.
- Standard dose: 1 cc/kg. Max volume per injection: 30-40 cc.
- Fast heart rates require faster contrast flow rates (delivered within one cardiac cycle).
- Layered contrast technique: Precise manual injection for selective angiograms (e.g., coronary artery) to minimize total contrast volume.
Common Interventional Procedures
Balloon Atrial Septostomy (Rashkind Procedure)
- Creates atrial communication in duct-dependent lesions (e.g., Transposition of Great Arteries, tricuspid atresia).
- Performed via femoral or umbilical vein.
- Catheter advanced across patent foramen ovale into LA. Balloon inflated. Pulled rapidly/forcefully back to RA-IVC junction.
- Complications: Arrhythmias, atrial free wall perforation, IVC avulsion.
Transseptal Puncture
- Accesses left heart when foramen ovale closed.
- Equipment: Brockenbrough needle or Radiofrequency (Baylis NRG) needle.
- Guidance: Intracardiac echocardiography (ICE) or Transesophageal echocardiography (TEE).
- Technique: Assembly descends from SVC to RA. Needle maintained at 5 o’clock position. “Jump” noted as assembly drops under limbus of fossa ovalis. Puncture confirmed via LA pressure tracing and oxygen saturation.
- Complications (1%): Aortic puncture, atrial free wall perforation, thrombus introduction.
Balloon Valvuloplasty
- Standard therapy for isolated pulmonary or aortic valve stenosis.
- Aortic Valvuloplasty: Exchange-length wire looped in LV (avoids mitral valve/LV apex damage). Balloon inflated across annulus until “waist” disappears. Rapid deflation required. Marked hypotension and bradycardia occur during inflation.
- Complications: Creation of valvular insufficiency (more poorly tolerated on aortic side).
Radiofrequency Perforation
- Treats pulmonary atresia with intact ventricular septum.
- Contraindicated in patients with RV-dependent coronary circulation. RV decompression results in fatal coronary steal and myocardial ischemia.
Transcatheter Pulmonary Valve Implantation
- Treats right ventricular outflow tract (RVOT) dysfunction (e.g., post-Tetralogy of Fallot repair).
- Melody or Harmony valve deployed.
- Crucial step: Rule out coronary artery compression. Expand sizing balloon in RVOT with simultaneous selective coronary angiography or aortic root injection. Ensures stent will not occlude adjacent coronary arteries.
Complications and Management
Overall complication rate ~7.8% (6% minor, 1.8% major). Major complications higher in interventional procedures.
| Complication | Etiology & Mechanism | Management & Prevention |
|---|---|---|
| Arrhythmias | Catheter/wire contact with endocardium. High risk in ventricular inversion (L-TGA) leading to complete heart block during PA catheterization. | Transient. Reposition catheter. Temporary transvenous pacing for heart block. Defibrillation for ventricular fibrillation. |
| Cardiac Perforation | Excessive force against wall. Common sites: Atrial appendage, RVOT, RV free wall (during biopsy). | Immediate recognition via echocardiography. Reverse anticoagulation. Pericardiocentesis. Autotransfusion via sheath side-arm. |
| Vascular Access Thrombosis | Common in infants <5 kg, long sheaths, large sheaths, small femoral arteries (<3 mm). | Systemic heparinization. Doppler US evaluation. Recombinant tissue plasminogen activator (rTPA) infusion. Recanalization. |
| Air Embolism | Balloon rupture, inadequate flushing, or negative intrathoracic pressure (snoring) drawing air through open catheter. | Use CO2 for balloon inflation (absorbs quickly). “Canadian technique” (water seal with saline-filled syringe) during wire removal. |
| Cyanosis / Hypoxia | Hypoventilation, pneumothorax, or increased right-to-left shunting (e.g., hypercyanotic spell in TOF). | Supplemental oxygen. Identify and correct underlying etiology (e.g., fluid bolus/phenylephrine for tet spell). |