Pacemaker syndrome

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2] Tayebah Chaudhry[3]

Pacemaker syndrome is a condition that represents the clinical consequences of suboptimal atrioventricular (AV) synchrony or AV dyssynchrony, regardless of the pacing mode, after pacemaker plantation. It is an iatrogenic disease that is often underdiagnosed.

In general, the symptoms of the syndrome are a combination of decreased cardiac output, loss of atrial contribution to ventricular filling, loss of total peripheral resistance response, and nonphysiologic pressure waves.

Individuals with a low heart rate prior to pacemaker implantation are more at risk of developing pacemaker syndrome. Normally the first chamber of the heart (atrium) contracts as the second chamber (ventricle) is relaxed, allowing the ventricle to fill before it contracts and pumps blood out of the heart. When the timing between the two chambers goes out of synchronization, less blood is delivered on each beat. Patients who develop pacemaker syndrome may require adjustment of the pacemaker timing, or another lead fitted to regulate the timing of the chambers separately.

• Since the implantation of artificial pacemaker in 1958, cases of decreased cardiac output due to ventricular pacing have been reported.

• Majority of the patients had increased total peripheral resistance due to aortic and carotid reflexes activity resulting from reduced cardiac output.

• The loss of physiologic timing of atrial and ventricular contractions, or sometimes called AV dyssynchrony, leads to different mechanisms of symptoms production.
• Due to loss of AV synchrony, there is no atrial kick, and thus cardiac output decreases.
• Decrease cardiac effect causes signs and symptoms of Pacemaker syndrome which includes:
  • Shortness of breath
  • Fatigue
  • Chest pain
  • Choking sensation
  • Anxiety
  • Dizziness
  • Confusion
  • Palpitations.
• This altered ventricular contraction will decrease cardiac output, and in turn will lead to systemic hypotensive reflex response with varying symptoms.^[1]

• The incidence of pacemaker syndrome varies from 2%^[2] to 83%.^[3]

• The wide range of reported incidence is likely attributable to two factors which are the criteria used to define pacemaker syndrome and the therapy used to resolve that diagnosis.^[4]

• No laboratory tests are usually indicated in pacemaker syndrome. But levels of atrial natriuretic peptide and brain natriuretic peptide can be measured to define the level of cardiac functioning.

• Electrocardiographic findings in pacemaker syndrome may include prolonged PR interval, VA conduction due to dyssynchrony between atria and ventricles and/or AV dissociation.

• Sometimes surgical intervention is needed.
• After consulting an electrophysiologist, an additional pacemaker lead placement might be needed, which eventually relieves some of the symptoms.

• At the time of pacemaker implantation, AV synchrony should be optimized to prevent the occurrence of pacemaker syndrome.
• Patients with optimized AV synchrony have shown great results and very low incidence of pacemaker syndrome than those with suboptimal AV synchronization.
• References

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2] Raviteja Guddeti, M.B.B.S. [3] Mohammed Salih, MD. [4] Tayebah Chaudhry[5]

Since the implantation of artificial pacemaker in 1958, cases of decreased cardiac output due to ventricular pacing have been reported. The majority of the patients had increased total peripheral resistance due to aortic and carotid reflexes activity resulting from the reduced cardiac output.

• Pacemaker syndrome was first described in 1969 by Mitsui et al. as a collection of symptoms associated with right ventricular pacing.^[1][2]

• The name pacemaker syndrome was first coined by Erbel in 1979.^[1][3]

• Since its first discovery, there have been many definitions of pacemaker syndrome but the understanding of the cause of pacemaker syndrome still under investigation.

• In a general sense, pacemaker syndrome can be defined as the symptoms associated with right ventricular pacing relieved with the return of A-V and V-V synchrony.

• In 1994 Furman redefined pacemaker syndrome to include loss of AV synchrony, retrograde ventriculoatrial conduction, and absence of rate response to the general physiologic requirement.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2] Raviteja Guddeti, M.B.B.S. [3] Tayebah Chaudhry[4]

The loss of physiologic timing of atrial and ventricular contractions, or sometimes called AV dyssynchrony, leads to different mechanisms of symptoms production. This altered ventricular contraction will decrease cardiac output, and in turn, will lead to systemic hypotensive reflex response with varying symptoms.

Pacemaker Syndrome Mechanisms:

AV dyssynchrony leads to various symptoms with different mechanisms of symptom production.

• Loss of AV synchrony
• Valvular incompetence
• Asynchronous ventricular contractions
• Ventriculoatrial conduction
• Echo beats
• Arrhythmias

Inappropriate pacing in patients with decreased ventricular compliance, which may be caused by diseases such as:

• Hypertensive cardiomyopathy
• Hypertrophic cardiomyopathy
• Restrictive cardiomyopathy
• Aging

All of the above causes result in loss of atrial contraction and significantly reduces cardiac output because in such cases the atria are required to provide 50% of cardiac output, which is normally only 15% – 25%.^[1][2]

• Atrial contraction against a closed tricuspid valve can cause pulsation in the neck and abdomen, headache, cough, and jaw pain.^[1][3]

• Ventricular pacing is associated with dyssynchrony between the atria and ventricles causing an elevated right and left atrial pressures, as well as elevated pulmonary venous and pulmonary arterial pressures, which can in turn lead to symptomatic pulmonary and hepatic congestion.

• Patients with pacemaker syndrome exhibit increased plasma levels of ANP. That’s due to increase in left atrial pressure and left ventricular filling pressure, which is due to decreased cardiac output caused by dyssynchrony in atrial and ventricular contraction in ventricle paced rhythms.

• ANP and BNP are potent arterial and venous vasodilators that can override carotid and aortic baroreceptor reflexes attempting to compensate for decreased blood pressure.

• Usually patients with cannon a waves have higher plasma levels of ANP than those without cannon a waves.^[4][5][6][7]

• A major cause of AV dyssynchrony is VA conduction.
• VA conduction, sometimes referred to as retrograde conduction, leads to delayed, nonphysiologic timing of atrial contraction in relation to ventricular contraction.
• Nevertheless, many conditions other than VA conduction promote AV dyssynchrony.^[4][1][3]
• Ventricular paced rhythms cause a reduction in cardiac output by causing a nonphysiologic depolarization of the ventricles.
• Depolarization patterns and contraction are altered when pacemaker leads are placed in the apex of the right ventricle.
• This will further decrease blood pressure and cause a secondary increase in ANP and BNP.^[5][6]
• In patients with heart failure it has been shown that institution of biventricular pacing mode has been associated with a better cardiac output.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahshid Mir, M.D. [2] Raviteja Guddeti, M.B.B.S. [3]

Patients with pacemaker syndrome present with varied symptoms resulting from dyssynchrony between atria and ventricles. Pacemaker syndrome should be differentiated from the following diseases:Acute coronary syndrome, failed pacemaker, hypothyroidism, cardiogenic pulmonary edema, arrhythmias (especially supraventricular tachycardias), hyperthyroidism, pulmonary embolism, and carotid sinus hypersensitivity.

Patients with pacemaker syndrome present with varied symptoms resulting from dyssynchrony between atria and ventricles.

Presenting symptoms include:

• Dyspnea
• Edema
• Orthopnea
• Symptoms of low cardiac output like weakness, fatigue, lightheadedness and dyspnea on exertion
• Hypotension
• Shock
• Orthostatic changes
• Syncope
• Dizziness
• Right upper quadrant pain
• Headaches
• Palpitations
• Easy fatigability

Pacemaker syndrome should be differentiated from the following diseases:

• Consider Pacemaker Syndrome as a differential diagnosis in a patient with implanted ventricular pacemaker who develops new neurological or cardiovascular symptoms
• Acute coronary syndrome
• Failed pacemaker
• Hypothyroidism
• Cardiogenic pulmonary edema
• Arrhythmias (especially supraventricular tachycardias)
• Hyperthyroidism
• Pulmonary embolism
• Carotid sinus hypersensitivity

On the basis [symptom 1], [symptom 2], and [symptom 3], [disease name] must be differentiated from [disease 1], [disease 2], [disease 3], [disease 4], [disease 5], and [disease 6].

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2] Mohammed Salih, MD. [3] Tayebah Chaudhry[4]

• The incidence of pacemaker syndrome varies from 2%^[1] to 83%.^{[2] [3]}
• The wide range of reported incidence is likely attributable to two factors, which are, the criteria used to define pacemaker syndrome and the therapy used to resolve that diagnosis.^[3]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2] Mohammed Salih, MD. [3]

• People with the following conditions are at higher risk of developing Pacemaker Syndrome:
  • Left ventricular disease
  • Recipients of single-chamber ventricular pacemakers
  • Retrograde conduction
  • Decreased stroke volume
  • Decreased cardiac output
  • Decreased left atrial total emptying fraction
  • Elderly people

• According to most trials the only two variables that predict the development of pacemaker syndrome in the pre-implantation period are low sinus rate, and a higher programmed lower rate limit. Similarly in the post-implantation period, an increased percentage of ventricular paced beats is the only variable that significantly predicts the development of pacemaker syndrome.
• One major risk factor for the development of pacemaker syndrome is the presence of an intact VA conduction (retrograde ventriculo-atrial conduction).
• Intact VA conduction is present in as many as 90% of patients with preserved AV conduction, and in about 30-40% of patients with complete AV block. VA conduction may develop at any time after implantation of the pacemaker and may not be apparent at the time of implantation of the device.
• Patients with cardiomyopathy (hypertensive, hypertrophic, restrictive) and elderly individuals are particularly sensitive to the development of pacemaker syndrome because of the presence of noncompliant ventricles and diastolic dysfunction which lead to loss of atrial contribution to ventricular filling and in turn to pacemaker syndrome.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2] Mohammed Salih, MD. [3]

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Studies have shown that patients with pacemaker syndrome and/or with sick sinus syndrome are at higher risk of developing fatal complications that calls for the patients to be carefully monitored in the ICU. Complications include:

• Atrial fibrillation
• Thrombo-embolic events
• Heart failure
• Hypotension
• Cardiogenic shock
• Complications of treatment – when a new pacemaker is implanted or a new lead is placed the following complications may be seen:
  • Infection
  • Pneumothorax
  • Cardiac tamponade
  • Shock
  • Bleeding

Prognosis of pacemaker syndrome is usually excellent after correction of the pacing mode.

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