What is Pacemaker Syndrome?
Pacemakers are medical devices used to manage serious heart rhythm problems and have greatly improved the lives of those affected. They are crucial tools in treating conditions where the heart becomes weak and abnormally enlarged, known as cardiomyopathies.
Usually, pacemakers control the rhythm of the lower chambers of the heart, known as the ventricles. However, this can sometimes cause the upper and lower chambers of the heart to contract out of sync. This can reduce the volume of blood the heart pumps out, due to the upper part of the heart contracting against a closed heart valve, or because it contracts too close to when the lower part of the heart beats, leading to a backflow of blood and reducing the overall effectiveness of the heart’s pumping action.
Since the introduction of pacemakers in 1958, doctors have observed reductions in the amount of blood the heart pumps out due to the pacemaker controlling the lower parts of the heart. Although the body usually counters this by narrowing blood vessels to maintain blood pressure, not all patients can compensate in this way. In these cases, various symptoms occur, mostly due to the reduced blood volume pumped out by the heart and decreased resistance of the blood vessels, a condition known as pacemaker syndrome.
What Causes Pacemaker Syndrome?
Pacemaker syndrome is usually encountered when there is a single-chamber device equipped with sensors and pacemaker leads in the ventricle (one of the heart’s lower chambers). Since there is no sensor in the atrium or upper chamber of the heart, the lower chamber contracts based on a programmed schedule, irrespective of when the upper chamber contracts. This makes the upper and lower chambers function out of sync, leading to a decrease in the amount of blood pushed out by the heart with each beat, and subsequently, a decreased overall heart performance. This condition is called VA conduction. VA conduction is typically a lower heart chamber beat getting up to the upper chamber of the heart and causing incorrectly-timed contractions in the upper chamber. This also produces effects similar to pacemaker syndrome.
Risk Factors and Frequency for Pacemaker Syndrome
The occurrence of pacemaker syndrome can range widely, being as high as 80% and as low as 5%. It’s seen about equally in both males and females.
When it comes to single-chamber and ventricular-paced devices in VVI mode, the occurrence rate is close to 20%, as shown in the MOST trial.
In large studies like MOST, PASE, and CTTOP, it was found that changing the pacing mode or revising the device to dual chamber pacing (DDD) was the most effective solution. This was often what was necessary to relieve the symptoms in most patients.
Signs and Symptoms of Pacemaker Syndrome
Diagnosing this condition is often simple due to the timing of symptoms. These usually start once a device has been implanted or when the pacemaker begins working, particularly for patients whose heart rhythm heavily relies on the pacemaker. This is especially true if they have a type of pacemaker that only works in one chamber of the heart.
However, for older adults, the situation can be more complicated. They might have difficulty recalling their symptoms correctly, and their symptoms might be unspecific and could easily be attributed to aging instead of their heart condition.
Common symptoms include:
- Neurological: tiredness, memory loss, confusion, and sometimes temporary bouts of unconsciousness
- Cardiovascular: low blood pressure, shortness of breath during exercise, waking up from sleep due to shortness of breath, irregular heartbeats, decrease in ability to workout, fainting
- Hemodynamic: noticeable pulsations in the neck and abdomen, upper right side of the abdominal pain
The physical examination often reveals the following signs:
- Low blood pressure, rapid breathing, low oxygen levels, crackling sounds in the lungs
- A small difference between the systolic and diastolic blood pressure and a weak pulse
- Distended neck veins and a specific pattern known as a cannon wave in the recorded vein pulse
- An examination of the chest area might show signs of valve leakage and variations in the intensity of the first heart sound
- Swellings or fluid accumulation in the abdomen and a liver that pulsates may be seen in serious cases
- Swelling of the lower legs
- A neurological examination might show confusion, dizziness, or changes in mental status
Testing for Pacemaker Syndrome
If you’ve had a pacemaker installed, your doctor will likely perform some routine tests to make sure it is functioning as it should. These tests include a chest x-ray, which shows the placement of your pacemaker lead in the right ventricle (RV) of your heart, and an ECG (Electrocardiogram), which monitors the electrical activity in your heart.
Doctors look for pacing spikes in the ECG, which indicate the pacemaker is sending out impulses to regulate your heart rhythm. However, when there is no synchrony – or matching rhythm – between the P waves and QRS complexes, two vital components of your heart rhythm, this could suggest a possible issue.
Usually, there’s no need for additional laboratory tests. Sometimes though, a blood test to check for cardiac troponins – proteins that are a marker for heart damage – might be needed. An echocardiogram, an ultrasound of your heart, may also be performed to observe the motion of the heart walls and measure the ejection fraction (EF) – the percentage of blood that leaves your heart each time it contracts. If there’s a decline in EF or new motion abnormalities in the heart show up, it may suggest cardiomyopathy, a disease of the heart muscle.
Figuring out the diagnosis often involves looking at your symptoms and comparing them to your heart rhythm. In the past, a drop in systolic blood pressure – the pressure in your arteries when your heart beats – during ventricular pacing periods was considered a sign of a condition, but this isn’t always the case and may not be practical.
Arriving at a diagnosis often involves ruling out other conditions. This might involve the use of a Holter monitor or an event recorder to track heart rhythms over a period of time. If the pacemaker evaluation reveals that your heart is highly dependent on the pacemaker, this could lead to the diagnosis of a particular heart condition.
Treatment Options for Pacemaker Syndrome
If your heart pacemaker only has a single chamber, you might need to switch to a dual chamber device. The dual chamber device can better regulate the heart as it controls both the atria and the ventricles (the upper and lower chambers of your heart). This type of pacemaker will more closely mimic the natural pacing of the heart, making it a better choice for some people.
If, at the same time, your left ventricle (the chamber of the heart that pumps blood to the body) isn’t working as well as it should be and your ejection fraction (EF – a measure of how well your heart is pumping) is low, it might be a good idea to consider a specific type of device called a Cardiac Resynchronization Therapy (CRT) device. CRT devices are used to help the heart’s chambers work together more efficiently.
If you have left ventricle dysfunction, it’s also recommended that you follow the usual treatment plan for heart failure. This could include a mix of lifestyle changes and medications to help your heart pump better, ease symptoms, and improve your overall quality of life.
What else can Pacemaker Syndrome be?
When a person has a fast heart rate, also known as tachyarrhythmias, it’s often due to conditions like atrial fibrillation or flutter. These can be easily ruled out by conducting an Electrocardiogram (ECG) and checking out the proper function of any implanted cardiac device.
Other conditions, like poor functioning of the left ventricle of the heart (LV dysfunction) or heart muscle diseases (cardiomyopathies), can also cause similar symptoms. However, these can be ruled out using an ultrasound of the heart (echocardiography). If the person has a cardiac device that is compatible with MRI, a Cardiac MRI, which offers more detailed images, can also be used to check the tissue of the heart.
What to expect with Pacemaker Syndrome
The outlook for people with this condition is generally positive as it’s commonly recognized and easily treated. However, if it goes unrecognized and untreated, it can lead to the development of issues in the left and right sides of the heart, irregular and rapid heartbeats, and a decrease in the quality of life due to severe and debilitating symptoms as mentioned earlier.
Possible Complications When Diagnosed with Pacemaker Syndrome
- Low quality of life
- Left heart ventricle dysfunction
- Right heart ventricle dysfunction
- Heart failure
- Fast, irregular heart rhythms
Preventing Pacemaker Syndrome
Doctors should inform patients about the necessity of the device they are about to receive and what specific device will be most beneficial for their condition. This conversation should happen before the device is implanted.
If a device designed to work with one chamber of the heart is to be implanted, it’s crucial that the patient receives detailed information about the potential risks and occurrence rate of this procedure. They should be aware of the signs and symptoms to look out for that might indicate a problem. Every effort will be made to keep the heart beating in time or in ‘electrical synchrony’ for patients getting a device to control their heart rhythm. This means the device will help to ensure the heartbeats are coordinated properly.
