Continuing Education Activity

Pacemakers have become an established modality for long-term management of life-threatening arrhythmias and can significantly improve patients' quality of life. They have also become a cornerstone in the management of cardiomyopathies. Conventionally, these devices pace the ventricle in isolation, which can result in poor coordination between atrial and ventricular contraction and a subsequent reduction in cardiac output. This is known as pacemaker syndrome, and may be due to 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 ventricular output. This activity reviews the pathophysiology of pacemaker syndrome and the importance of the interprofessional team in its management.

Objectives:

• Describe the pathophysiology of pacemaker syndrome.
• Describe the symptoms of pacemaker syndrome.
• Summarize the treatment options for pacemaker syndrome.
• Explore modalities to improve care coordination among interprofessional team members in order to improve outcomes for patients affected by pacemaker syndrome.

Introduction

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.

Etiology

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.

Epidemiology

The incidence of pacemaker syndrome varies widely, but has been reported as high as 80%[1] and as low as 5%[2], and is seen fairly constantly in both genders.[3]

With single-chamber and ventricular-paced devices in VVI mode, the incidence approaches 20% as has been reported in the MOST trial.[4]

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.[5][6][7]

Pathophysiology

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.[8]

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.[9][10]

Hence, AV dyssynchrony and VV dyssynchrony and retrograde conduction of ventricular beats form the pathophysiological basis of this entity.[11]

History and Physical

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;

• Neurologic: Fatigability, memory loss, confusion, and often transient blackouts
• Cardiovascular: Low blood pressures, exertional dyspnea, orthopnea, palpitations, a decrease in exercise capacity, syncope
• Hemodynamic: Prominent neck pulsations, abdominal pulsations, right upper quadrant (RUQ) pain

Examination often yields the following signs:

• Hypotension, tachypnea, low oxygen saturation, lung rales
• Narrow pulse pressure and low pulse volume
• Neck vein distension and cannon wave in JVP tracing
• Precordial examination may reveal regurgitant murmurs and variability in the intensity of first heart sound
• Pulsatile liver and ascites may be present in severe cases
• Lower extremity edema
• Neurologic examination may reveal confusion, dizziness, or altered mental status

Evaluation

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 / Management

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.

Differential Diagnosis

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

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.

Complications

• Poor quality of life
• LV dysfunction
• RV dysfunction
• Heart failure
• Tachyarrhythmias

Consultations

Such patients should be managed in consortium with a cardiologist and a cardiac electrophysiologist.

Deterrence and Patient Education

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.

Pearls and Other Issues

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.

Enhancing Healthcare Team Outcomes

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.