Cardiac Catheterization
Overview and Historical Context
- Diagnostic cardiac catheterization remains a valuable tool in pediatric cardiology.
- It provides precise blood flow data, pressure measurements, and anatomical delineation.
- Non-invasive modalities like echocardiography and magnetic resonance imaging (MRI) have largely replaced it for purely anatomic diagnosis.
- It was first introduced by Dr. Werner Forssmann in 1929 via self-experimentation.
- It remains unparalleled for determining precise hemodynamics and facilitating transcatheter interventions.
Clinical Indications
Diagnostic Indications
- Diagnostic catheterizations assess suitability for surgery and aid in comprehensive management planning.
| Indication Category | Specific Clinical Scenarios |
|---|---|
| Hemodynamic Assessment | Quantifying left-to-right shunts (Qp:Qs ratio) in borderline cases. Measuring pulmonary vascular resistance (PVR) in older patients with shunts. |
| Pulmonary Hypertension | Evaluating resting pressures and conducting pulmonary vasoreactivity testing. Utilizing inhaled nitric oxide or epoprostenol to check reversibility. |
| Single Ventricle Palliation | Pre-operative assessment prior to bidirectional Glenn and Fontan completion. Post-Fontan surveillance for pulmonary arteriovenous malformations or elevated circuit pressures. |
| Myocardial Biopsy | Diagnosing cardiomyopathy or screening for cardiac transplant rejection. Serving as the gold standard for diagnosing myocarditis. |
| Electrophysiological Study | Evaluating arrhythmias or mapping accessory pathways prior to radiofrequency ablation. |
| Complex Anatomy | Delineating complex pulmonary atresia with major aortopulmonary collateral arteries (MAPCAs). |
Interventional Indications
- Interventional cardiology offers a less traumatic alternative to open heart surgery.
- Recovery is typically rapid.
| Intervention Type | Examples and Applications |
|---|---|
| Device Closure | Occlusion of selected secundum atrial septal defects (ASD), ventricular septal defects (VSD), and patent ductus arteriosus (PDA). |
| Balloon Valvuloplasty | First-line treatment for congenital pulmonary and aortic valve stenosis. |
| Vascular Stenting | Relief of aortic coarctation or branch pulmonary artery stenosis. |
| Septostomy | Balloon atrial septostomy (Rashkind procedure) for immediate mixing in transposition of the great arteries. |
Pre-Procedural Preparation
Clinical Evaluation
- Obtaining an accurate history and performing a thorough examination are essential.
- Review previous surgical reports, cardiac anatomy, and prior catheterization data.
- Document contrast reactions, drug allergies, and bleeding disorders.
- Identify concurrent medical problems like renal insufficiency that affect contrast tolerance.
- Obtain a pregnancy test for females of child-bearing age.
Informed Consent
- Informed consent is mandatory due to the invasive nature of the procedure.
- Explain intended plans and general risks like bleeding, vascular injury, and clot formation.
- Discuss procedure-specific risks.
- Embolization, heart block, and cardiac erosion are risks in ASD device closure.
- Valvular regurgitation is a specific risk in balloon valvuloplasty.
Laboratory and Blood Bank Preparation
- Ensure blood type and screen are completed.
- Have blood products available at the procedure location for high-risk interventions.
Equipment and Vascular Access
Vascular Access Routes
- Percutaneous entry is usually obtained in the femoral vein or internal jugular vein.
- Ultrasound guidance reduces vascular complications during access.
- Access to the left heart is achieved by crossing a patent foramen ovale.
- If the foramen is closed, retrograde arterial access or transseptal puncture is required.
- Right internal jugular vein access forms a natural counterclockwise curve directing the catheter into the right pulmonary artery.
Catheter Selection and Dynamics
- Fluid-filled catheters connect to pressure-sensitive transducers.
- The transducer diaphragm converts pressure changes into electrical waveforms.
- Systems must be de-aired, tightened, and zeroed at the mid-axillary line.
Common Catheter Types
- Balloon-Tipped Catheters: Berman wedge catheters feature an end hole and proximal balloon. They are soft and flow-directed.
- End-Hole Catheters: Provide accurate pressure measurements for discrete gradients. Cannot measure wedge pressures effectively.
- Multi-Hole Catheters: Pigtail or NIH catheters deliver large contrast volumes rapidly. They reduce the risk of injection-induced arrhythmias or catheter recoil.
Hemodynamic Data Acquisition
Saturation and Pressure Measurement
- Measure oxygen saturation in each chamber to calculate pulmonary and systemic blood flow.
- Calculate the Qp:Qs ratio to determine the magnitude of shunting.
- Record pressures across valves to determine gradients and calculate valve areas.
- The systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) are critical indicators.
- Evaluate pressure waveforms for high-frequency artifacts or excessive dampening.
Angiocardiography
- Selective injection of radiopaque contrast delineates specific chambers and vessels.
- A power injector delivers the contrast medium.
- Digital biplane cineangiocardiography captures detailed anatomy in two simultaneous planes.
- Operators must aspirate the catheter before injection to ensure it is not wedged against a wall.
- Injecting contrast into a wedged catheter causes myocardial staining or vascular dissection.
Complications and Management
- The overall complication rate is approximately 7.8%.
- Minor complications occur in 6% of cases.
- Major complications occur in 1.8% of cases, predominantly during interventional procedures.
Arrhythmias
- Arrhythmias frequently result from catheter or wire contact with the endocardium.
- Most are transient and resolve by adjusting the catheter position.
- Sustained ventricular tachycardia or fibrillation can occur during ventriculography.
- Complete heart block may develop.
- Patients with ventricular inversion (L-TGA) are particularly susceptible to heart block when catheters enter the pulmonary artery.
Structural and Vascular Injury
- Cardiac perforation can occur, leading to hemopericardium and tamponade.
- Vascular access complications include retroperitoneal bleeding, pseudoaneurysms, and arteriovenous fistulas.
- Arteriovenous fistulas present with a continuous machinery murmur over the access site.
- Retroperitoneal bleeding should be suspected if unexplained abdominal pain or a hematocrit drop occurs.
Hemodynamic and Systemic Complications
- High volumes of contrast material increase the risk of contrast-induced nephropathy.
- Cardiovascular effects of contrast are related to osmolarity, sodium content, and injection rate.
- Critically ill infants are susceptible to hypothermia, hypoglycemia, and acidosis during the procedure.