Pacemaker Syndrome and Pacemaker Complications

Synonym: AV dyssynchrony syndrome

This article deals with the complications of pacemakers, including pacemaker syndrome. Pacemakers are discussed further in the separate articles Pacemakers and Pacing, Inserting Temporary Pacemakers, and Implantable Cardioverter Defibrillators.

Pacemakers sense intrinsic cardiac activity and pacing is inhibited when this occurs:

• Atrial pacing is used in sick sinus syndrome and in patients without any conduction disturbance.
• Ventricular pacing (pacing catheter in the right ventricle) is necessary for complete heart block.

Causes of pacing system malfunction include undersensing, oversensing, loss of capture, loss of output, inappropriate rate, inappropriate lead position, inappropriate mode, extracardiac stimulation, true pulse generator failure, pacemaker-mediated tachycardia (in dual-chamber pacemakers with DDD, VDD, and DDDR modes), pacemaker syndrome and inappropriate fiddling of the pulse generator by the patient. Most pacing system malfunctions are benign, but some can be life threatening.

• Complications related to venous access include pneumothorax, haemothorax, and air embolism.
• Lead-related complications include perforation, dislodgment, diaphragmatic stimulation, and malposition (including passage into left side of heart via a septal defect). Cardiac tamponade, usually due to chamber perforation should be suspected whenever hypotension occurs.
• Local pocket-related complications include haematoma, wound pain, pocket erosion, and infection.
• Pacemaker infection ranges from mild local pain and erythema to life-threatening septicaemia. The most common pathogens are coagulase-negative staphylococci, Staphylococcus aureus Gram-negative enteric bacilli and mixed infections.
• Delayed complications of permanent pacing leads include venous thrombosis, exit block, insulation failure, and conductor fracture. Late lead damage may be reduced by use of axillary or cephalic venous access.
• Most modern pulse generators have an expected longevity of 5–9 years and unexpected pulse generator (electrical) failure is rare.
• Lead-related problems (increased thresholds, decreased impedance) resulting in increased current drain are the most common causes of premature battery depletion.
• Lithium-iodine batteries used in current pulse generators are not rechargeable and surgical replacement of the entire generator is required.

• Immediate complications include:
  • Ventricular tachycardia or fibrillation
  • Arterial puncture
  • Pneumothorax
  • Brachial plexus injury
• Late complications include:
  • Ventricular arrhythmias
  • Septicaemia (especially Staphylococcus infection)
  • Wrong position requiring repositioning

• The rate of acute complications of pacemaker insertion is 4–5% and mostly related to operator experience.¹
• The incidence of late complications of permanent pacemakers has been reported as 2.7%.¹

• Investigation for possible underlying myocardial infarction, including troponins and creatine kinase (which is elevated in myocardial injury and cardiac trauma).
• Coagulation screen: prevent bleeding complications during invasive procedures.
• Electrolytes: exclude electrolyte abnormalities that may affect pacing thresholds.
• Drug levels: e.g. digoxin and other antiarrhythmics that may alter pacing thresholds.
• Chest x-ray: evaluate lead position and fracture. A chest x-ray can be used to identify the pacemaker model, as most pacemakers have an x-ray code which is visible on a standard chest xray.
• Echocardiogram: to assess for inappropriate lead position, pericardia effusion or tamponade, or lead fracture.
• Pacemaker assessment:
  • Evaluation of thresholds, lead impedance, and battery voltage, as well as review of histograms, mode switch episodes, and stored electrocardiograms.
• Magnet application:
  • After magnet application, pacemaker goes to asynchronous pacing mode at a programmed rate, which is unique to that model. This is helpful in diagnosis of loss of capture and battery depletion.
• ECG:
  • To diagnose arrhythmias and also undersensing, oversensing, and capture loss.
  • The best method of diagnosis is to correlate symptoms with cardiac rhythms, e.g. using Holter monitoring and event recorders.
• Telemetry monitoring:
  • Early recognition of loss of sensing and capture from lead dislodgement in immediate post-implant period.
• Transtelephonic monitoring:
  • Early recognition of battery depletion based on the magnet rate, which is unique to each pacemaker model.
• Fluoroscopy:
  • To evaluate lead fracture, especially during provocative manoeuvres.

Pacemaker syndrome refers to the occurrence of symptoms relating to the loss of atrial-ventricular synchrony in patients with a pacemaker.

• Ventricular pacing has been shown to sacrifice the atrial contribution to ventricular output.
• In some cases, atrial contraction occurs against closed atrioventricular valves, producing reverse blood flow.
• In response to decreased cardiac output, total peripheral resistance is usually increased in order to maintain blood pressure but does not increase in some patients, resulting in decreased blood pressure.
• This combination of decreased cardiac output with a loss of the usual compensatory increase in total peripheral resistance contributes to the development of pacemaker syndrome.
• The incidence of pacemaker syndrome has been estimated to range from 7% (symptoms severe enough to warrant pacemaker revision) to 20% (mild to moderately severe symptoms).⁴ Asymptomatic pacemaker syndrome is probably common and the true incidence of pacemaker syndrome much higher.¹
• In 1994 Furman redefined pacemaker syndrome as:⁵
  • Loss of AV synchrony
  • Retrograde ventriculoatrial (VA) conduction
  • Absence of rate response to physiological need

Most authorities now understand pacemaker syndrome as being related to non-physiological timing of atrial and ventricular contractions, which may occur in a variety of pacing modes. It has been proposed that pacemaker syndrome should be renamed as AV dyssynchrony syndrome, which better reflects the mechanism responsible for causing symptoms.⁶

Risk factors⁶

• Patients with sick sinus syndrome frequently have preserved AV conduction.
• As many as 90% of patients with preserved AV conduction may have VA conduction, which predisposes them to pacemaker syndrome.
• Patients may have intact VA conduction not apparent at the time of implantation or may develop VA conduction at any time after pacemaker implantation.
• Patients with non-compliant ventricles and diastolic dysfunction (e.g. the elderly and patients with cardiomyopathy) are particularly sensitive to loss of the atrial contribution to ventricular filling.

Prevention

• Most cases of pacemaker syndrome occur with ventricular pacing and so atrial pacing should be used whenever possible.
• Alternatively, a dual-chamber system can be programmed to a long AV interval to promote intrinsic conduction, as long as dyssynchrony related to marked first-degree AV block is not present.
• Pacing parameters must be optimised, e.g. AV delay, to achieve physiological timing of atrial and ventricular contractions.

Presentation of pacemaker syndrome⁶

• Most common symptoms include pulsation and fullness in neck, dizziness, palpitations, fatigue, light-headedness and syncope.
• Symptoms of heart failure may occur.¹
• Symptoms can vary considerably and also vary in severity.
• Signs are also variable and include hypotension, tachycardia, tachypnoea, raised JVP and cannon waves.
• There may be variations in pulses and fluctuating blood pressure.
• A drop of 20 mm Hg or more during ventricular pacing compared to that during atrial or AV synchronous pacing is suggestive of pacemaker syndrome.
• Basal lung crepitations, tender and pulsatile liver and peripheral oedema may occur.
• Examination of the heart may demonstrate regurgitant murmurs and variability of heart sounds.

Differential diagnosis

• AV dyssynchrony may also occur without a pacemaker (called ” pseudopacemaker syndrome“), e.g. extremely prolonged first-degree AV block, nodal rhythm more rapid than the atrial rate (such as in children with sinus node dysfunction after congenital defect repair) and hypertrophic cardiomyopathy with complete AV block.⁶
• Possible other causes for the patient's presentation are pacemaker malfunction, inappropriate mode switching, worsening heart failure, recent change in medications (especially anti-hypertensives), paroxysmal atrial fibrillation, sinus tachycardia, autonomic dysfunction and respiratory tract infection.

Management

• In patients with other pacing modes, symptoms usually resolve after upgrading the pacemaker to a dual-chamber pacing system,⁷ or reprogramming the pacemaker parameters, e.g. AV delay, post-ventricular atrial refractory period, sensing level, and pacing threshold voltage.
• Medical therapy has a limited role but electrolyte abnormalities may need to be corrected and the medication regime should be reviewed and adjusted as needed.

Prognosis

• Prognosis is excellent with correction of pacing mode.