Cardiac Catheterization

1. Introduction

Cardiac catheterization is an invasive procedure involving the introduction of radiopaque catheters into the heart chambers and great vessels under fluoroscopic guidance to obtain hemodynamic and anatomic data.

2. Indications

Hemodynamic Assessment: Calculation of shunt (Qp:Qs ratio), pulmonary vascular resistance (PVR), and systemic vascular resistance (SVR).
Anatomical Evaluation: Delineating complex anatomy not fully captured by Echo/CT/MRI (e.g., peripheral pulmonary artery stenosis, aortopulmonary collaterals).
Pre-operative Evaluation: Assessing operability in Left-to-Right shunts (reversibility of PVR with O2 or Nitric Oxide).
Post-operative Evaluation: Assessing conduit function, residual shunts, or baffle obstructions.
Specific Conditions: Evaluation of cardiomyopathies, heart transplant surveillance (endomyocardial biopsy), and pulmonary hypertension.

3. Procedure Components

Vascular Access: Percutaneous (Seldinger technique), usually via the femoral vein (Right heart) and femoral artery (Left heart).
Oximetry Run: Blood samples collected from various chambers to detect "step-up" (L-to-R shunt) or "step-down" (R-to-L shunt).
Pressure Recording: Measurements of systolic, diastolic, and mean pressures in all chambers/vessels.
Angiography: Injection of non-ionic contrast to visualize morphology.

4. Hemodynamic Data Interpretation

Shunt Calculation (Fick’s Principle):
- $Q p / Q s = (S a t_{A o} - S a t_{M V}) / (S a t_{P V} - S a t_{P A})$
- (Where Qp = Pulmonary flow, Qs = Systemic flow).
Vascular Resistance:
- $P V R = (M e a n P A P r e s s u r e - M e a n L A P r e s s u r e) / Q p$
- Normal PVR: < 2 Wood Units (WU). Values > 6 WU often indicate inoperability.

5. Complications

Vascular: Hematoma, arterial thrombosis (common in infants), or pseudoaneurysm.
Cardiac: Arrhythmias (typically transient), cardiac perforation/tamponade.
Systemic: Contrast-induced nephropathy, allergic reactions, or air embolism.
General: Hypothermia and hypoglycemia (especially in neonates).

6. Post-Procedure Care

Continuous monitoring of vitals and distal pulses.
Flat bed rest for 4-6 hours with pressure dressing on the puncture site.
Encouraging fluid intake to facilitate contrast excretion.