Pacemaker Syndrome

Pacemaker syndrome is a group of symptoms and signs caused by loss of normal atrioventricular synchrony or by inappropriate atrioventricular timing in a paced patient.

It is classically seen with single chamber ventricular pacing (VVI), in which the atria contract against closed atrioventricular valves whenever the ventricle is paced and retrograde ventriculoatrial conduction is present.

It can also occur with dual chamber pacing when the atrioventricular delay is too long or too short, or atrial pacing is delayed by interatrial conduction. Reported frequency varies widely with the definition, with clinically significant disease in roughly 20% of patients with VVI pacing and much less with dual chamber pacing.

Retrograde conduction is present in a substantial minority of patients with sick sinus syndrome and in more patients with intact atrioventricular conduction.

Pathophysiology. Loss of the atrial contribution to ventricular filling (about 20 to 30% of cardiac output, more with a stiff ventricle) lowers stroke volume.

Atrial contraction against closed valves raises atrial and pulmonary venous pressures, and atrial stretch produces reflex vasodilatation and a fall in blood pressure through neurohumoral mechanisms. Ventricular pacing from the right ventricular apex also adds dyssynchrony and functional mitral regurgitation.

High ventricular pacing burdens can lead to pacing induced cardiomyopathy. The combined effect is reduced cardiac output, reduced cerebral perfusion, venous congestion and atrial arrhythmia.

• Fatigue, lightheadedness, presyncope or syncope, dyspnoea, orthopnoea, palpitations, throbbing in the neck or head, cough, chest discomfort, confusion, and symptoms that are worse on exertion.
• Hypotension during pacing, with a fall in systolic pressure of 20 mm Hg or more compared with intrinsic rhythm.
• Cannon a waves in the jugular venous pulse, a variable first heart sound, pulsations in the neck and abdomen, and signs of congestion with crackles and oedema.
• Symptoms can start days or years after implantation.

Red flags.

• Syncope or presyncope in a paced patient
• Systolic blood pressure fall of 20 mm Hg or more on pacing
• New or worsening heart failure
• New atrial fibrillation
• Falling ejection fraction with a high percentage of ventricular pacing
• Symptoms that resolve when the patient is in intrinsic rhythm

• ECG. Ventricular pacing with retrograde P waves or atrioventricular dissociation, with intermittent sinus rhythm.
• Device interrogation. Pacing mode (VVI, VVIR, or dual chamber), percentage of ventricular pacing, presence of atrial activity and retrograde conduction time, programmed atrioventricular delay, and rate response. Test retrograde conduction by ventricular pacing at a rate over the sinus rate and examining the atrial electrogram.
• Comparison of blood pressure in paced and intrinsic rhythm by reducing the lower rate or enabling hysteresis. A fall of 20 mm Hg or more on pacing supports the diagnosis.
• Echocardiography. Atrial size, pulmonary venous flow reversal during atrial systole, mitral and tricuspid regurgitation, ejection fraction and dyssynchrony.
• Natriuretic peptide and exercise testing for chronotropic competence and symptoms.
• Exclusion of other causes. Haemoglobin, thyroid function, electrolytes, lead position on chest X-ray, and echocardiography for pericardial effusion.

Differential diagnosis.

• Pacemaker mediated tachycardia
• Lead perforation or pericardial effusion
• Pacing induced cardiomyopathy
• Exit block or battery depletion
• Atrial fibrillation with rapid ventricular response
• Chronotropic incompetence
• Progressive heart failure or valve disease
• Orthostatic hypotension from antihypertensive drugs
• Anaemia, thyrotoxicosis and anxiety
• Pulmonary embolism
• Tricuspid regurgitation from the lead
• Neurally mediated syncope

• Restore atrioventricular synchrony. Upgrade a single chamber ventricular pacemaker to dual chamber (DDD or DDDR) or atrial based pacing (AAIR) when atrioventricular conduction is intact. In permanent atrial fibrillation, synchrony cannot be restored. Use rate responsive ventricular pacing with the lowest lower rate that avoids bradycardia.
• Reprogramme first when possible.
  • Enable rate hysteresis or search hysteresis, or lower the lower rate, to allow intrinsic conduction.
  • Optimise the atrioventricular delay: shorten when a long delay causes diastolic mitral regurgitation, lengthen when atrial contraction occurs too late relative to ventricular filling, and use algorithms that promote intrinsic conduction.
  • Review the rate response settings.
• High ventricular pacing burden with ejection fraction of 50% or less: upgrade to biventricular or conduction system pacing.
• Medical measures have limited effect. Avoid vasodilating drugs that worsen hypotension, and treat heart failure and atrial fibrillation with their usual therapy.
• Upgrade risks: pocket infection, lead dislodgement, venous occlusion, and tricuspid valve injury. Check the venous anatomy before upgrading, and give antibiotic prophylaxis for the procedure.

Special groups. Older adults with a normal ejection fraction and mild symptoms may be managed by reprogramming alone. Active people and those with heart failure usually need an upgrade.

Monitoring. Check symptoms and blood pressure in paced and intrinsic rhythm at 2 to 4 weeks after reprogramming or upgrade. Device checks every 3 to 12 months with remote monitoring. Echocardiography at 3 to 6 months when ejection fraction was reduced or ventricular pacing exceeds 40%.

Referral and escalation. Refer to the device clinic or electrophysiology. Urgent for syncope, heart failure, new atrial fibrillation or falling ejection fraction.