CVT Electrophysiology Studies & Catheter Ablation 1 — Questions and Answers
Question 1: What is the primary purpose of an electrophysiology (EP) study?
- To measure cardiac output during exercise
- To map electrical pathways and identify arrhythmia mechanisms (Correct answer)
- To assess coronary artery anatomy
- To evaluate valvular function
Correct answer: To map electrical pathways and identify arrhythmia mechanisms
EP studies use intracardiac catheters to map electrical conduction and identify the origin and mechanism of arrhythmias.
Question 2: Which catheter position is used to record His bundle electrograms during an EP study?
- Right atrial appendage
- Coronary sinus
- Tricuspid valve region (Correct answer)
- Right ventricular apex
Correct answer: Tricuspid valve region
The His bundle catheter is positioned at the tricuspid valve region to record activation of the AV node and His bundle.
Question 3: What does the HV interval measure in an electrophysiology study?
- Time from sinus node discharge to atrial activation
- Time from His bundle activation to ventricular depolarization (Correct answer)
- Time from atrial pacing to ventricular response
- Time from P-wave onset to QRS complex onset
Correct answer: Time from His bundle activation to ventricular depolarization
The HV interval (normally 35–55 ms) measures conduction time from the His bundle through the His-Purkinje system to ventricular activation.
Question 4: Radiofrequency (RF) catheter ablation destroys arrhythmogenic tissue primarily by:
- Freezing cardiac tissue to create conduction block
- Delivering high-voltage shocks to reset the arrhythmia circuit
- Applying thermal energy to cause localized tissue necrosis (Correct answer)
- Injecting alcohol to destroy accessory pathways
Correct answer: Applying thermal energy to cause localized tissue necrosis
RF ablation delivers resistive heating (typically 50–60°C) through the catheter tip to create a focal lesion of coagulative necrosis.
Question 5: In Wolff-Parkinson-White (WPW) syndrome, which EP study finding confirms the presence of an accessory pathway?
- Prolonged HV interval greater than 70 ms
- Short or negative HV interval with ventricular pre-excitation (Correct answer)
- Absence of a recordable His bundle potential
- Complete AV block induced during atrial pacing
Correct answer: Short or negative HV interval with ventricular pre-excitation
WPW produces a short or negative HV interval because the ventricles are pre-excited via the accessory pathway before normal His-Purkinje conduction.
Question 6: Why is cryoablation often preferred over RF ablation for AVNRT located close to the AV node?
- It creates larger lesions with less contact force
- It allows reversible testing (cryomapping) before creating a permanent lesion (Correct answer)
- It generates more precise temperature control above 70°C
- It eliminates the need for fluoroscopic guidance
Correct answer: It allows reversible testing (cryomapping) before creating a permanent lesion
Cryoablation permits cryomapping at –30°C; if AV block occurs, the effect is reversible, reducing the risk of permanent AV nodal damage.
Question 7: During a standard EP study, where is the atrial pacing catheter most commonly placed?
- Left ventricle via retrograde aortic approach
- Pulmonary artery
- Right atrium or coronary sinus (Correct answer)
- Descending aorta
Correct answer: Right atrium or coronary sinus
Atrial pacing to evaluate AV nodal function and induce supraventricular arrhythmias is performed from the right atrium or coronary sinus.
CVT Electrophysiology Studies & Catheter Ablation 1
What is the primary purpose of an electrophysiology (EP) study?