What are the symptoms and signs of a pacemaker (artificial cardiac pacemaker) malfunction?

Recognizing Pacemaker Malfunction

If you suspect a pacemaker has stopped working, look for the return of the original symptoms that led to pacemaker placement—particularly lightheadedness, syncope, extreme fatigue, or confusion—combined with a heart rate below the programmed pacemaker rate on ECG. 1

Key Clinical Presentations of Pacemaker Failure

Symptom Recurrence

• Bradycardia symptoms reappear: Patients develop lightheadedness, presyncope, syncope, or confusional states that were previously controlled by pacing 2
• Fatigue and exercise intolerance: Marked decrease in functional capacity, particularly if the patient had chronotropic incompetence requiring rate-responsive pacing 2
• Congestive heart failure symptoms: Worsening dyspnea, edema, or reduced cardiac output in patients who were pacemaker-dependent 2

Pacemaker Syndrome Features

• Cannon A waves: Visible neck pulsations from atrial contraction against closed AV valves due to loss of AV synchrony 2, 3
• Hypotension: Sudden drops in blood pressure >20 mmHg, particularly with ventricular-only pacing 2
• Malaise and weakness: Inadequate cardiac output from improper timing of atrial and ventricular contractions 2, 3

ECG Findings Indicating Malfunction

Failure to Capture

• Pacing spikes without QRS complexes: The pacemaker fires but fails to depolarize the myocardium 1
• Heart rate below programmed rate: Native rhythm slower than the pacemaker's lower rate limit 1

Failure to Sense (Oversensing/Undersensing)

• Inappropriate pacing: Pacemaker fires during the patient's intrinsic rhythm when it should be inhibited 1, 4
• Intermittent non-conducted P waves: Pacemaker inappropriately inhibited by noise or oversensing 4
• Competitive rhythms: Pacemaker and native rhythm compete, potentially triggering ventricular arrhythmias 5

Lead-Related Problems

• Positional symptoms: Dizziness or palpitations with specific arm movements suggesting lead fracture or insulation break 4
• Intermittent capture: Inconsistent pacing suggesting lead displacement or elevated stimulation threshold 5

Critical Warning Signs Requiring Immediate Evaluation

Life-Threatening Presentations

• Documented asystole or pauses ≥3 seconds: Particularly in pacemaker-dependent patients 2
• Ventricular rate <40 bpm in symptomatic patients: Indicates complete failure in patients with underlying complete heart block 2
• Syncope in pacemaker patients: Must be presumed pacemaker-related until proven otherwise 2

High-Risk Scenarios

• Sudden death risk: 10-30% of pacemaker patients die suddenly, often from ventricular fibrillation in the context of myocardial failure rather than pacemaker malfunction itself 5
• Pacemaker-dependent patients: Those with complete heart block, post-AV junction ablation, or no escape rhythm are at highest risk from device failure 2

Diagnostic Approach

Immediate Assessment

• 12-lead ECG: Compare current heart rate to programmed lower rate limit; look for pacing spikes and their relationship to QRS complexes 1
• Magnet application: Placing a magnet over the pacemaker converts it to asynchronous mode (VOO/DOO), which can help differentiate sensing from capture problems 1
• Vital signs: Document blood pressure, particularly orthostatic changes suggesting hemodynamic compromise 2

Pacemaker Interrogation

• Device check required: Formal interrogation reveals battery status, lead impedances, sensing thresholds, and stored diagnostic data 1, 4
• Lead impedance changes: Sudden decreases suggest insulation break; sudden increases suggest lead fracture 4
• Threshold elevation: Gradual increases in pacing threshold may indicate lead maturation or myocardial changes at the electrode interface 1, 5

Common Pitfalls to Avoid

• Assuming symptoms are non-cardiac: In pacemaker patients with confusional states, bradycardia, or syncope, always suspect device malfunction first 2
• Ignoring positional symptoms: Dizziness with arm movement is highly suggestive of lead fracture and requires urgent evaluation 4
• Overlooking battery depletion: Gradual symptom recurrence may indicate end-of-life battery rather than acute failure 1
• Missing pacemaker syndrome: New fatigue, dyspnea, or hypotension in VVI-paced patients may represent loss of AV synchrony rather than device failure 2, 3