How Pacemakers & Implantable Cardioverter Defibrillators (ICDs) Work

Life-saving cardiac devices such as pacemakers and implantable cardioverter defibrillators (ICDs) play an important role in treating patients with cardiac arrhythmia. Also known as heart rhythm problems, cardiac arrhythmias occur when the electrical signals that regulate the heart’s beats don’t work like they should. These problems cause the heart to beat either too fast (tachycardia), too slow (bradycardia) or irregularly. While some arrhythmias are harmless, many are life-threatening or can lead to stroke, heart failure, and an increased risk for blood clots.

Here, we’ll explain the history and function of the pacemaker and implantable cardioverter defibrillator (ICD) and how they’re helping improve quality of life and peace of mind for many patients.

Pacemakers – Pacing a Slow Heart Rate

Since their invention in 1958, pacemakers have helped patients suffering from bradycardia, or an unusually slow heart rate. Today, approximately three million people worldwide are living with a pacemaker, and each year about 600,000 pacemakers are implanted.

Bradycardia is defined as a heartbeat that’s slower than 60 beats per minute, and it can occur for a wide variety of reasons. Most commonly, it’s caused by heart tissue damaged due to aging. It can also be caused by infection of the heart tissue (myocarditis) or damage to heart tissues caused by heart disease or heart attack. In rare cases, it can be genetic, or caused by inflammatory diseases, an underactive thyroid gland, obstructive sleep apnea or certain medications.

While not everyone who suffers from bradycardia needs a pacemaker, many do. For WakeMed Heart & Vascular patients, the decision is based on a personalized approach based on each individual’s risk factors, medication and medical history, as well as symptoms. Bradycardia can be a serious problem if the heart can’t pump enough oxygen-rich blood throughout the body. In these cases, patients may feel dizzy, lightheaded, short of breath, fatigue or experience confusion.

“Some patients have a slow heart rate and feel fine, while others may experience symptoms that are either dangerous or have a negative impact on their quality of life,” explains Ashish Patel, MD, MPH, FACC, WakeMed Heart & Vascular – Complex Arrhythmia.

“While common, arrhythmias are complex health problems. That’s why we look at each patient individually and perform a careful evaluation before making any treatment recommendations.”

Types of Pacemakers

Depending on the rhythm problem(s) being addressed, there are several types of pacemakers with a varying number of leads or wires.

Single-chamber pacemakers use just one lead (wire) that typically carries electrical impulses to the right ventricle of your heart. They’re often used in patients with atrial fibrillation or in patients who need very infrequent pacing.
Dual chamber pacemakers are the most common type in the United States and use two leads to carry electrical impulses to the right ventricle and the right atrium of your heart to help control the timing of contractions between the two chambers.
Biventricular pacemakers use three wires to deliver what’s called cardiac resynchronization therapy. This treatment is for patients who have an abnormal contraction pattern of the left ventricle. This kind of pacemaker helps restore a more normal contraction pattern of the left ventricle, which is the main pumping chamber of the heart.

Living With a Pacemaker

Pacemakers are generally implanted in a surgical procedure via a small incision in the shoulder. While less common, leadless pacemakers are placed using a nonsurgical procedure via a small puncture site in the right leg. In either scenario, most patients go home the same day or require an overnight hospital stay.

Once implanted, the pacemaker records and stores data on the patient’s heart rate, 24/7. The cardiologist will use remote monitoring technology to identify any time-sensitive problems, which results in a follow-up phone call to the patient. Approximately once a quarter, a thorough evaluation of heart rate readings will be reviewed by the cardiologist to identify any potential problems or opportunities to modify the plan of care.

In most cases, adjusting to life with a pacemaker is uneventful and the device will remain in place, untouched, for 8-10 years. When the battery nears the end of its life, the cardiologist will be notified well in advance and together, the patient and cardiologist can make a plan to schedule the minor procedure required to replace the device.

Keep An Eye Out For Signs of a Device-Related Infection

While device-related infections are relatively rare, both having a surgical procedure and introducing a foreign device into the body can put you at risk. Most infections occur shortly after surgery at the incision site, but internal infections can also occur where the leads connect to your heart. Contact your cardiologist right away if you experience any of the following signs of an infection:

Fever
Chills
Localized redness/inflammation
Pain at the implant site
Drainage from a sore near the surgical site
Erosion of pacemaker through the skin

Device Interference

Certain equipment and machines can interfere with both pacemakers and ICDs, which can keep devices from working properly. While your cardiologist can provide a full list, the following devices can cause interference.

Anti-theft systems such as those found in large retail establishments
Metal detectors for security
Earbuds and clip-on headphones
Battery powered cordless tools
Lawnmowers, leaf blowers, chainsaws
Medical alert systems and falls detection pendants
Cell phones and cordless phones (generally OK to use, but should be kept 6 inches away from your device)

Talk to your doctor for specific details on how or if you should limit your exposure to these and other devices and machinery.

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