Pacemakers have become an established modality for long-term management of life-threatening arrhythmias and improve the quality of life of affected patients significantly. Pacemakers have also become a cornerstone in the management of cardiomyopathies.
Conventionally, these devices pace the ventricle in isolation, often leading to improper or mistimed atrial and ventricular contraction causing a reduction in cardiac output. This may be due to mistimed atrial contraction occurring against closed atrioventricular (AV) valve or atrial contraction occurring too close to ventricular contraction, producing back pressure in venous circulation systems and loss of atrial contribution to the ventricular output.
Since the invention of this therapy in 1958, physicians have reported reductions in cardiac output as a response to ventricular pacing. Although baroreceptor reflexes do compensate for this by increasing peripheral vascular resistance, this is not always the case. In patients who fail to compensate for the loss of cardiac output with these mechanisms, a wide variety of symptoms are noted and mostly attributable to a loss in cardiac output and decreased peripheral resistance. This phenomenon and the resulting constellation of signs and symptoms is referred to as pacemaker syndrome.
Pacemaker syndrome is most commonly seen in the setting of a single chamber device with ventricular sensing and pacing lead. Since there is no atrial sensing lead to guide the ventricle, the ventricle contracts at the programmed rate regardless of the timing of atrial contraction. This leads to loss of AV synchrony which leads to a loss in stroke volume and cardiac output. VA conduction, which is usually a ventricular beat finding its way upwards to the atria also leads to a mistimed atrial contraction and produces similar effects.
With single-chamber and ventricular-paced devices in VVI mode, the incidence approaches 20% as has been reported in the MOST trial.
In large trials as MOST, PASE and CTTOP, it was observed the pacing mode change or device revision to dual chamber pacing (DDD) helped the most and was often what was required to alleviate the symptoms in the majority of patients.
The physiologic electrical coupling and synchronization of atria and ventricles are altered whenever a pacing device is implanted. This is less of a concern with temporary pacemakers which are implanted for a shorter duration, but with permanent pacemakers, this physiologic coupling gets impaired and leads to electrical dyssynchrony which effects both AV coordination and VV coordination commonly referred to as AV dyssynchrony and VV dyssynchrony.
AV dyssynchrony results in mistimed atrial contractions which cause back pressure in venous circulation systems that causes congestion (peripheral and pulmonary) as well as loss of atrial contribution leading to decreased cardiac output. Frequently a ventricular beat that is conducted upward to the atrium also gives rise to a similar phenomenon.
VV dyssynchrony leads to mistiming of contraction of opposing ventricular walls, as RV pacing causing left bundle branch block (LBBB) pattern which is associated with asynchronous contraction of the inter-ventricular septum and opposing LV walls. This event often leads to a loss in output of the left ventricle and increases back pressure in the pulmonary circulation.
Hence, AV dyssynchrony and VV dyssynchrony and retrograde conduction of ventricular beats form the pathophysiological basis of this entity.
Diagnosis is often straightforward due to the correlation of timing of device implantation/onset of pacing and the timing of symptoms, as well as more frequent and persistent symptoms in patients who are pacing dependant in the setting of single chamber devices.
In the aging population, however, there might be some confusion in reporting and remembering symptoms, and most of these could be non-specific which can often be attributed to aging.
Symptoms often include the following;
Examination often yields the following signs:
Chest x-ray usually reveals a single pacemaker lead stationed in RV.
ECG reveals pacing spikes with adequate capture but no relation/synchrony between P waves and QRS complexes.
Laboratory studies are usually not required; however, cardiac troponins and an echocardiogram may reveal new wall motion abnormalities or a decline in EF suggesting cardiomyopathy. Clinicians best reach diagnosis when they correlate patients' symptoms with the cardiac rhythm. Historically, a drop in systolic blood pressures during episodes of ventricular pacing has been used as a perimeter to diagnose this entity, but this is not always the case and may not be practical.
Diagnosis is clinical and often one of exclusion. This may include the use of a Holter monitor or event recorder to look for arrhythmias. Often, device interrogation reveals pacemaker dependancy which also gives a clue to the presence of this entity.
Treatment includes switching to DDD or VDD modes in a dual chamber device. Up-gradation to a dual chamber device is necessary for single-chamber pacemakers. Concomitantly if the patient has LV dysfunction and low EF, then a CRT will be the preferred device for implantation/up-gradation.
Standard heart failure therapy is warranted for patients with LV dysfunction.
Tachyarrhythmias, most commonly atrial fibrillation or flutter, are the usual differential and can be easily excluded by an ECG and device interrogation. LV dysfunction and cardiomyopathies which usually present with similar symptoms can be excluded by echocardiography with tissue characterization by cardiac MRI (if the device is MRI compatible).
Prognosis is favorable because this entity is widely recognized and easily treated. However, if not recognized, and left untreated, it can result in the development of LV dysfunction, RV dysfunction, tachyarrhythmias and poor quality of life due to severe and debilitating symptoms as described above.
Such patients should be managed in consortium with a cardiologist and a cardiac electrophysiologist.
Providers should educate patients about the need for the device and based on the indications and pacing needs, what type of device will benefit most. This must be done before device implantation.
However, if single chamber ventricular lead devices are to be implanted then the patient must be counseled in detail about the possibility, prevalence and signs/symptoms of this condition. Every attempt must be made to maintain electrical synchrony in patients undergoing cardiac rhythm device implantation.
Despite advances in cardiac device therapy, it is recognized that complete electrical synchrony between cardiac chambers is not attainable at present and there still might be some patients who will develop this constellation of signs and symptoms. However, it is the clinician and electrophysiologist's job to make sure that all attempts are made to maintain and restore AV and VV synchrony to avoid pacemaker syndrome.
The right device for the right patient should be the provider's rationale.
Discussion and effective communication between the primary or referring physician, the cardiologist, and the cardiac electrophysiologist should be ensured at all times. This will not only minimize the development of the syndrome by selecting the right device for the right patient but will also help in effective management that improves patient outcomes and ensures patient safety.
|||Heldman D,Mulvihill D,Nguyen H,Messenger JC,Rylaarsdam A,Evans K,Castellanet MJ, True incidence of pacemaker syndrome. Pacing and clinical electrophysiology : PACE. 1990 Dec [PubMed PMID: 1704534]|
|||Andersen HR,Thuesen L,Bagger JP,Vesterlund T,Thomsen PE, Prospective randomised trial of atrial versus ventricular pacing in sick-sinus syndrome. Lancet (London, England). 1994 Dec 3 [PubMed PMID: 7983951]|
|||Lamas GA,Lee K,Sweeney M,Leon A,Yee R,Ellenbogen K,Greer S,Wilber D,Silverman R,Marinchak R,Bernstein R,Mittleman RS,Lieberman EH,Sullivan C,Zorn L,Flaker G,Schron E,Orav EJ,Goldman L, The mode selection trial (MOST) in sinus node dysfunction: design, rationale, and baseline characteristics of the first 1000 patients. American heart journal. 2000 Oct [PubMed PMID: 11011325]|
|||Link MS,Hellkamp AS,Estes NA 3rd,Orav EJ,Ellenbogen KA,Ibrahim B,Greenspon A,Rizo-Patron C,Goldman L,Lee KL,Lamas GA, High incidence of pacemaker syndrome in patients with sinus node dysfunction treated with ventricular-based pacing in the Mode Selection Trial (MOST). Journal of the American College of Cardiology. 2004 Jun 2 [PubMed PMID: 15172414]|
|||Lamas GA,Orav EJ,Stambler BS,Ellenbogen KA,Sgarbossa EB,Huang SK,Marinchak RA,Estes NA 3rd,Mitchell GF,Lieberman EH,Mangione CM,Goldman L, Quality of life and clinical outcomes in elderly patients treated with ventricular pacing as compared with dual-chamber pacing. Pacemaker Selection in the Elderly Investigators. The New England journal of medicine. 1998 Apr 16 [PubMed PMID: 9545357]|
|||Connolly SJ,Kerr CR,Gent M,Roberts RS,Yusuf S,Gillis AM,Sami MH,Talajic M,Tang AS,Klein GJ,Lau C,Newman DM, Effects of physiologic pacing versus ventricular pacing on the risk of stroke and death due to cardiovascular causes. Canadian Trial of Physiologic Pacing Investigators. The New England journal of medicine. 2000 May 11 [PubMed PMID: 10805823]|
|||Lamas GA,Lee KL,Sweeney MO,Silverman R,Leon A,Yee R,Marinchak RA,Flaker G,Schron E,Orav EJ,Hellkamp AS,Greer S,McAnulty J,Ellenbogen K,Ehlert F,Freedman RA,Estes NA 3rd,Greenspon A,Goldman L, Ventricular pacing or dual-chamber pacing for sinus-node dysfunction. The New England journal of medicine. 2002 Jun 13 [PubMed PMID: 12063369]|
|||Ausubel K,Furman S, The pacemaker syndrome. Annals of internal medicine. 1985 Sep [PubMed PMID: 3896087]|
|||Rosenqvist M,Isaaz K,Botvinick EH,Dae MW,Cockrell J,Abbott JA,Schiller NB,Griffin JC, Relative importance of activation sequence compared to atrioventricular synchrony in left ventricular function. The American journal of cardiology. 1991 Jan 15 [PubMed PMID: 1987716]|
|||Grines CL,Bashore TM,Boudoulas H,Olson S,Shafer P,Wooley CF, Functional abnormalities in isolated left bundle branch block. The effect of interventricular asynchrony. Circulation. 1989 Apr [PubMed PMID: 2924415]|
|||Lamas GA,Ellenbogen KA, Evidence base for pacemaker mode selection: from physiology to randomized trials. Circulation. 2004 Feb 3 [PubMed PMID: 14757681]|