Heparin Before DC Cardioversion for PSVT
No, heparin is NOT routinely given before DC cardioversion for PSVT—anticoagulation is specifically indicated for atrial fibrillation and atrial flutter, not for typical paroxysmal supraventricular tachycardia (PSVT). 1, 2
Key Distinction: PSVT vs. Atrial Fibrillation
The critical issue here is understanding that PSVT and atrial fibrillation are fundamentally different arrhythmias with different thromboembolic risks:
- PSVT (including AVNRT and AVRT) does not cause atrial stasis or thrombus formation because atrial mechanical function remains coordinated 1, 2, 3
- Atrial fibrillation/flutter causes loss of coordinated atrial contraction, leading to blood stasis and thrombus formation, particularly in the left atrial appendage 4
When Heparin IS Required: Atrial Fibrillation/Flutter
For atrial fibrillation or atrial flutter requiring immediate cardioversion due to hemodynamic instability:
- Administer heparin concurrently with an initial IV bolus followed by continuous infusion 4, 5
- Target aPTT of 1.5-2.0 times control value 4, 6
- Continue oral anticoagulation (INR 2.0-3.0) for at least 4 weeks post-cardioversion 4
For AF/flutter of ≥48 hours duration or unknown duration:
- Either anticoagulate for 3 weeks before and 4 weeks after cardioversion 4
- OR perform TEE to exclude thrombus, then give heparin before cardioversion and oral anticoagulation for 4 weeks after 4, 5
For AF/flutter <48 hours duration:
- Anticoagulation may be based on thromboembolic risk assessment (CHA₂DS₂-VASc score) 4, 5
- If cardioversion is performed, still provide post-cardioversion anticoagulation for at least 4 weeks 7
Management of PSVT Requiring Cardioversion
For hemodynamically unstable PSVT:
- Perform immediate synchronized cardioversion without anticoagulation 1, 2, 3
- No heparin is needed before or after cardioversion 1, 3
For hemodynamically stable PSVT:
- First-line: vagal maneuvers (modified Valsalva maneuver, 43% effective) 1, 3
- Second-line: IV adenosine (91% effective) 1, 3
- Alternative medications: calcium channel blockers or beta-blockers 2, 3
- Cardioversion is reserved for refractory cases or hemodynamic instability 2, 3
Critical Pitfall to Avoid
Do not confuse PSVT with atrial fibrillation. The electrocardiographic features are distinct:
- PSVT: Regular narrow-complex tachycardia (150-250 bpm), P waves hidden or inverted, abrupt onset/termination 2, 8
- Atrial fibrillation: Irregularly irregular rhythm, absent P waves, fibrillatory waves 4
If there is any diagnostic uncertainty on a single-lead rhythm strip, obtain a 12-lead ECG immediately to confirm the diagnosis before treatment 8. Misdiagnosing atrial fibrillation as PSVT could lead to cardioversion without appropriate anticoagulation and subsequent stroke risk 4.