Understanding EPS/RFA: The Two-Phase Procedure

An EPS/RFA (Electrophysiology Study and Radiofrequency Ablation) is the standard endovascular diagnostic and therapeutic continuum for evaluating and managing complex cardiac arrhythmias.

Here is a breakdown of the two distinct but seamlessly integrated phases of the procedure:

The Diagnostic Phase: Electrophysiology Study (EPS)

The EPS is designed to assess the integrity of the heart’s electrical conduction system, induce clinical arrhythmias, and map their precise mechanisms and pathways.

• Catheter Placement: Multipolar electrode catheters are typically advanced via the femoral veins to standard right-sided cardiac stations: the high right atrium (HRA), the His bundle (HIS), the coronary sinus (CS), and the right ventricular apex/outflow tract (RVA/RVOT).
• Programmed Electrical Stimulation (PES): Extrastimulus testing and burst pacing are utilized to measure conduction intervals (such as AH and HV intervals), assess refractory periods, and intentionally induce reentrant or focal tachycardias.
• Mapping: Using either conventional fluoroscopy or 3D electroanatomical mapping systems (like CARTO or EnSite), the exact origin or critical isthmus of the arrhythmia is localized in real-time.

The Therapeutic Phase: Radiofrequency Ablation (RFA)

Once the arrhythmogenic substrate is definitively mapped, RFA is employed to eliminate the abnormal tissue.

• Mechanism: An ablation catheter delivers medium-frequency alternating current (typically 350–500 kHz). This energy generates resistive heating in the adjacent myocardium, causing localized coagulative necrosis. This effectively creates a targeted, non-conductive scar that permanently disrupts the abnormal circuit.
• Endpoints: The procedure concludes with rigorous post-ablation testing—often involving repeated PES or the administration of isoproterenol—to confirm the complete non-inducibility of the arrhythmia or to verify bidirectional block (such as across the cavotricuspid isthmus).

Common Clinical Indications

• AVNRT & AVRT (e.g., Wolff-Parkinson-White Syndrome): Targeting the slow pathway or accessory pathways.
• Atrial Fibrillation (AFib): Achieving pulmonary vein isolation (PVI) to block triggers.
• Typical Atrial Flutter: CTI (cavotricuspid isthmus) linear ablation.
• Ventricular Tachycardia (VT): Mapping and ablating surviving channels within structural scars or targeting idiopathic outflow tract foci.