What is Pacemaker Syndrome?
Pacemaker syndrome is an iatrogenic disorder characterized by symptoms such as fatigue, lightheadedness, syncope, dyspnea, chest discomfort, and presyncope that result from adverse hemodynamics due to loss of atrioventricular (AV) synchrony in patients with implanted pacemakers. 1
Core Pathophysiology
The syndrome arises from three primary mechanisms that disrupt normal cardiac hemodynamics:
- Loss of AV synchrony causing inadequate cardiac output, particularly when atrial contraction occurs against closed AV valves 1, 2
- Retrograde ventriculoatrial (VA) conduction leading to atrial contraction against closed AV valves, producing cannon A waves and elevated atrial pressures 1
- Beat-to-beat variations in cardiac contractile sequence with fixed asynchrony or episodic alternating synchrony and asynchrony 1
Clinical Manifestations
The American College of Cardiology defines a broad spectrum of symptoms that occur during ventricular pacing:
- Cardiovascular symptoms: Lightheadedness, presyncope, syncope, chest discomfort, dyspnea, and cough 1
- Systemic symptoms: Fatigue, confusion, and reduced exercise capacity 1, 3
- Hemodynamic findings: Systolic blood pressure drops ≥20 mm Hg during ventricular pacing, cannon A waves, and V waves transmitted to atria or pulmonary veins 1, 4
Incidence and Risk Factors
Pacemaker syndrome occurs in approximately 18-20% of patients with ventricular-based (VVI/VVIR) pacing, with most cases developing early (13.8% at 6 months). 5 In blinded randomized trials, up to 83% of patients in sinus rhythm experienced significantly worse symptoms with VVI mode compared to dual-chamber pacing (12 of 16 symptoms were significantly worse). 1
Key predictors include:
- Presence of intact retrograde VA conduction (most important risk factor) 1
- Higher percentage of ventricular pacing and slower underlying sinus rate 5
- Patients in sinus rhythm receiving ventricular-only pacing 1, 2
Prevention and Management
The American College of Cardiology and American Heart Association recommend avoiding VVI pacing in patients with sinus rhythm and using atrial-based (AAI/AAIR) or dual-chamber (DDD/DDDR) pacing to maintain AV synchrony. 1, 6
Treatment Algorithm:
- For established pacemaker syndrome: Convert from VVI to dual-chamber pacing, which abolishes symptoms and improves quality of life 4, 5
- For patients with congestive heart failure or need for maximum atrial contribution: VVI mode is contraindicated; dual-chamber pacing is mandatory 1, 6
- For patients with absent retrograde VA conduction: VVI pacing may be acceptable, though dual-chamber remains preferred 1
Important Caveats:
Pacemaker syndrome is not restricted to VVI pacing alone—it can occur, though rarely, with atrial and dual-chamber pacing modes when AV synchrony is suboptimal. 2, 7 The syndrome represents the clinical consequences of AV dyssynchrony regardless of pacing mode. 7
Because prediction of pacemaker syndrome is difficult based on baseline characteristics alone, the only reliable prevention strategy is to implant atrial-based pacemakers in all patients with sinus node dysfunction. 5 Quality of life improves significantly when patients are reprogrammed from ventricular to atrial-based pacing. 5, 6