Pacemaker Syndrome
Pacemakers have become an established modality for long-term management of life-threatening arrhythmias and can significantly improve patient's 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.
Causes of 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.
Symptoms of Pacemaker Syndrome
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
Diagnosis of Pacemaker Syndrome
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.
Treatment of Pacemaker Syndrome
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.