Electrophysiologic Mapping in PSVT Patients on Amiodarone
Yes, a patient with paroxysmal supraventricular tachycardia on amiodarone can absolutely undergo electrophysiologic mapping for re-entry mechanisms. Amiodarone does not contraindicate or preclude invasive electrophysiologic studies and catheter ablation procedures 1.
Rationale for Proceeding with Mapping
Electrophysiologic studies with mapping are specifically indicated for PSVT patients on amiodarone who have:
- Frequent or poorly tolerated episodes despite drug therapy 1
- Desire to be free of lifelong drug therapy 1
- Uncertainty about the exact tachycardia mechanism where EP study would guide appropriate therapy 1
The 2015 ACC/AHA/HRS guidelines explicitly position amiodarone as a second-line or last-resort agent for ongoing PSVT management, reserved only for patients who are not candidates for catheter ablation or in whom beta blockers, calcium channel blockers, and class Ic agents have failed or are contraindicated 1. This inherently supports proceeding to definitive mapping and ablation rather than continuing amiodarone long-term.
Clinical Context for Amiodarone in PSVT
Amiodarone's role in PSVT is limited due to:
- Significant extracardiac toxicity with long-term use 1
- Only Class IIb recommendation (Level C-LD evidence) for ongoing PSVT management 1
- Limited evidence base consisting primarily of small retrospective studies 1
While amiodarone can be effective for acute termination of PSVT (64% conversion rate in one large series) 2 and chronic suppression of refractory cases 3, 4, its toxicity profile makes it unsuitable as first-line chronic therapy 1, 4.
Electrophysiologic Effects During Mapping
Amiodarone will alter electrophysiologic properties during the mapping procedure:
- Prolongs AV nodal conduction (increases antegrade functional and effective refractory periods) 5
- Increases atrial cycle length for AV nodal Wenckebach block 5
- Prolongs retrograde conduction system refractory periods 5
- May prevent sustained PSVT induction during the study by blocking either antegrade or retrograde limbs of re-entry circuits 5
Important caveat: These electrophysiologic changes do not prevent accurate mapping of the re-entry circuit anatomy. The substrate (dual AV nodal pathways in AVNRT or accessory pathways in AVRT) remains identifiable and ablatable 1.
Procedural Approach
The mapping procedure should proceed as follows:
- Multielectrode catheter placement in standard positions (atria, ventricles, coronary sinus) for precise diagnosis 1
- Pacing and programmed electrical stimulation with or without pharmacologic provocation 1
- Three-dimensional electroanatomical mapping if needed 1
- Catheter ablation performed during the same session if re-entry mechanism is confirmed 1
If amiodarone prevents tachycardia induction during the study, this does not negate the value of the procedure—substrate mapping in sinus rhythm can still identify and allow ablation of the slow pathway in AVNRT or accessory pathways in AVRT 1.
Definitive Treatment Recommendation
Catheter ablation should be strongly considered as definitive therapy rather than continuing amiodarone, given:
- High success rates for radiofrequency ablation of re-entrant PSVT 1
- Avoidance of long-term amiodarone toxicity (pulmonary, thyroid, hepatic, ocular, neurologic) 1, 4
- Superior quality of life outcomes with ablation versus chronic drug therapy 1
The fact that this patient is already on amiodarone suggests either drug-refractory PSVT or intolerance to first-line agents—both scenarios strongly favor proceeding with EP study and ablation 1.