Pacemaker syndrome overview

# Overview
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.

# Historical Perspective
- 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.

# Pathophysiology
- 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.
- 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.

# Epidemiology and Demographics
- The incidence of pacemaker syndrome varies from 2% to 83%.
- 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.

# Diagnosis

## Laboratory Findings
- 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.

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

# Treatment

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

## Prevention
- 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
-  Ellenbogen KA, Gilligan DM, Wood MA, Morillo C, Barold SS (1997). "The pacemaker syndromea matter of definition". Am. J. Cardiol. 79 (9): 12269. doi:10.1016/S0002-9149(97)00085-4. PMID 9164889. Unknown parameter |month= ignored (help)CS1 maint: Multiple names: authors list (link) .mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
-  Andersen HR, Thuesen L, Bagger JP, Vesterlund T, Thomsen PE (1994). "Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome". Lancet. 344 (8936): 15238. doi:10.1016/S0140-6736(94)90347-6. PMID 7983951. Retrieved 2009-06-19. Unknown parameter |month= ignored (help)CS1 maint: Multiple names: authors list (link)
-  Heldman D, Mulvihill D, Nguyen H;  et al. (1990). "True incidence of pacemaker syndrome". Pacing and Clinical Electrophysiology : PACE. 13 (12 Pt 2): 174250. doi:10.1111/j.1540-8159.1990.tb06883.x. PMID 1704534. Unknown parameter |month= ignored (help); |access-date= requires |url= (help)CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
-  Farmer DM, Estes NA, Link MS (2004). "New concepts in pacemaker syndrome". Indian Pacing and Electrophysiology Journal. 4 (4): 195200. PMC 1502063. PMID 16943933. Retrieved 2009-06-19.CS1 maint: Multiple names: authors list (link)