Overdrive Pacing Protocol
Overdrive pacing involves pacing the heart at a rate faster than the underlying rhythm to either terminate existing arrhythmias (rapid atrial pacing) or prevent their onset (atrial overdrive pacing), with specific techniques varying by clinical indication. 1
Key Distinction: Rapid Atrial Pacing vs. Atrial Overdrive Pacing
Rapid Atrial Pacing (Termination)
- Purpose: Terminate existing atrial arrhythmias, particularly atrial flutter 2, 1
- Success rate: Approximately 82% cumulative success for atrial flutter termination (range 55-100%) 2
- Mechanism: Uses high-frequency burst pacing to interrupt arrhythmia circuits 1
Atrial Overdrive Pacing (Prevention)
- Purpose: Suppress atrial premature beats and prevent arrhythmia onset 1
- Mechanism: Paces at a rate 15 bpm higher than the underlying sinus rhythm or mean nocturnal heart rate 2, 1
- Application: Modern pacemakers include automatic algorithms that adjust pacing rate in response to underlying rhythm 1
Clinical Protocol for Rapid Atrial Pacing (Atrial Flutter Termination)
Patient Selection
- Ideal candidates: Post-cardiac surgery patients with epicardial atrial pacing wires already in place 2, 1
- Alternative access: Transesophageal pacing when temporary wires unavailable 2, 3
- Hemodynamic status: Patient must be hemodynamically stable; unstable patients require immediate DC cardioversion 2, 4
Pre-Procedure Considerations
- Anticoagulation: Address anticoagulation requirements if atrial flutter duration >48 hours, following same protocols as atrial fibrillation 2, 4
- Antiarrhythmic drugs: Consider pre-treatment with procainamide, ibutilide, or propafenone to facilitate conversion by enhancing impulse penetration of flutter circuit 2
- Rate control: Achieve adequate ventricular rate control before attempting conversion, as antiarrhythmic drugs may slow flutter rate and paradoxically increase ventricular response 2
Pacing Technique
- Standard overdrive pacing: Pace atrium at rate faster than flutter rate (typically 250-350 bpm for typical atrial flutter) 2
- Enhanced techniques: High-frequency atrial pacing or overdrive pacing with atrial extrastimuli when standard overdrive alone ineffective 2
- Duration: Continue pacing for 10-30 seconds, then abruptly terminate 2
- Repeat attempts: If initial attempt unsuccessful, repeat with slightly different pacing rates or cycle lengths 2
Equipment Requirements (if placing temporary transvenous wire)
- Haemostatic introducer sheath (5F or 6F) 2
- Bipolar temporary pacing catheter with preformed fish-hook shape for atrial positioning 2
- Sterile connector cable and pulse generator 2
- Fluoroscopy equipment for wire positioning 2
- Full sterile technique with iodine preparation and surgical drapes 2
Venous Access (if temporary wire needed)
- Preferred route: Right subclavian vein for ease of entry and flat surface positioning 2
- Alternative: Femoral vein for emergency situations or post-thrombolysis patients 2
- Avoid: Internal jugular if subclavian accessible, due to patient comfort and wire stability 2
Atrial Lead Positioning
- Insert wire until it lies vertically in right atrium 2
- Rotate to point leftward toward right atrial appendage 2
- Advance preformed fish-hook catheter tip into appendage 2
- Confirm position with lateral fluoroscopy showing anterior projection 2
- Secure with 2/0 silk sutures and clear dressing 2
Protocol for Ventricular Overdrive Pacing
Indications
- Primary indication: Torsades de pointes, where increasing heart rate temporarily protects against recurrence 5
- Secondary indication: Drug-resistant electrical storm in acute myocardial infarction as adjunct to antiarrhythmic therapy 6
- Recurrent monomorphic ventricular tachycardia: When amenable to pace termination 7, 8
Technique for Ventricular Tachycardia Termination
- Burst overdrive pacing: Deliver 8-10 pacing stimuli at rate 10-20% faster than VT cycle length 8
- Autodecremental pacing: Start 10-20% faster than VT, with 10 ms decrements between successive stimuli 8
- Effectiveness: 78% overall success rate for VT termination 8
- Avoid: 5 ms coupling decrements, which are less effective than 10 ms decrements 8
Technique for Torsades de Pointes Prevention
- Pace ventricle at rate 90-110 bpm to prevent pause-dependent arrhythmia 5
- Continue until QT interval normalizes with correction of underlying cause 5
- May use temporary atrioventricular sequential pacing for optimal hemodynamics 6
Duration for Electrical Storm
- Continue overdrive pacing for 24-25 hours after last arrhythmia episode 6
- Gradually wean pacing rate while monitoring for recurrence 6
- Maintain concurrent antiarrhythmic therapy and beta-blockade 6
Critical Pitfalls and Complications
Risk of Arrhythmia Induction
- Atrial fibrillation: Overdrive pacing may induce sustained AF instead of terminating flutter 2, 1
- Ventricular tachycardia acceleration: Occurs in 6.4% of VT episodes during overdrive pacing, with no specific pacing method showing higher propensity 8
- Management: Have DC cardioversion immediately available 2
Technical Failures
- Loss of capture: Verify adequate pacing thresholds before attempting overdrive 1
- Atrial undersensing: Ensure proper sensing function to avoid competitive pacing 1
- Coronary sinus cannulation: Electrode directed upward/leftward toward left shoulder; obtain lateral radiograph to confirm true right ventricular position 2
Contraindications
- Hemodynamic instability: Proceed directly to DC cardioversion 2, 4
- Pre-excitation syndromes: Risk of precipitating ventricular fibrillation with atrial pacing 4
- Recent thrombolysis: Consider femoral approach or transcutaneous pacing to avoid central venous cannulation complications 2
- Inexperienced operator: Defer to more experienced personnel or use alternative therapy 2