Before surviving a heart attack, I knew virtually nothing about pacemakers (they were just something that old people have to get, right?) and absolutely nothing about the cardiac device called implantable cardioverter defibrillators, or ICDs.
In fact, the first time I laid eyes on a person with an ICD was at my 7-week Heart To Heart cardiac support group after I was discharged from hospital.
One of the people in my group was a lovely, athletic 24-year old woman who had been diagnosed with a rare and serious heart arrhythmia called Long QT Syndrome.* Her sister had recently died suddenly due to the same condition.
This young woman was accompanied every week to our meetings by her mother. I could only imagine the impact of this catastrophic diagnosis on the mother, who had already buried one daughter because of it, and was now living with the knowledge that her surviving daughter carried the same deadly (and largely invisible) diagnosis. Her daughter’s ICD device was about the size of a small cellphone, its corners easily visible beneath the taut skin of her upper chest.
Both ICDs and pacemakers are medical devices that are implanted inside the bodies of heart patients. But what’s the difference between the two? Here’s some useful info, courtesy of the American College of Cardiology:
“A pacemaker is a small device that’s placed under the skin of your chest or abdomen to help control abnormal heart rhythms. This device uses electrical pulses to prompt the heart to beat at a normal rate. Pacemakers are used to treat heart rhythms that are too slow, fast, or irregular. These abnormal heart rhythms are called arrhythmias. Pacemakers can relieve some symptoms related to arrhythmias, such as fatigue or fainting. A pacemaker can help a person who has an abnormal heart rhythm resume a more active lifestyle.
“An ICD is a small device placed in your chest or abdomen if you have an irregular heartbeat or are at risk for sudden cardiac arrest. It sends electrical pulses or shocks to the heart when it senses any abnormalities in heartbeat. For example, if a patient with an ICD has an irregular heartbeat or goes into sudden cardiac arrest, the device will send a shock to the heart to restore normal heart rhythm. ICDs can be life-saving, as cardiac arrest can cause death within minutes if not treated.
“The biggest difference between an ICD and pacemaker is that an ICD continually monitors heart rhythm and can send low- or high-energy electrical pulses to correct an abnormal heart rhythm. ICDs will initially send low-energy pulses to restore heart rhythm, but switch to high-energy pulses when the low-energy shocks are ineffective.
“Pacemakers, however, only give low-energy electrical pulses to restore regular heartbeat.
“Therefore, ICDs are more effective in patients at high-risk for or with a history of sudden cardiac arrest, who may need these more powerful, high-energy electrical pulses to restore their regular heartbeat.”
Most newer ICDs can act as both a pacemaker and a defibrillator. Many can also record the heart’s electrical patterns when there is an abnormal heartbeat, a useful tool when planning future treatment.
An ICD can be programmed for these therapies:
- Low-energy pacing therapy. You may feel either nothing or a painless fluttering in your chest when your ICD responds to mild disruptions in your heartbeat.
- Cardioversion therapy. A higher energy shock is delivered to deal with a more serious heart rhythm problem. You might feel as if you’re being thumped in the chest.
- Defibrillation therapy. This is the strongest form of electrical therapy used to restore a normal heartbeat. During this therapy you may feel as if you’re being kicked in the chest. It may knock you off your feet. The pain from this therapy typically lasts only a second. There should be no discomfort after the shock is over.
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UPDATE: Watch this helpful video (about 7:20) by Doug Rachac, who has become my go-to resource for questions about implantable devices. Doug worked for Medtronic (a company that manufactures these devices) for 14 years, and then became an ICD patient himself.
* Long QT Syndrome: An inherited defect in heart rhythm that predisposes to sudden fainting spells, dizziness, palpitations, seizures and sudden death. The heart takes longer to recharge itself between beats. Certain conditions can trigger an abnormal cardiac rhythm. Among the known triggers for Long QT are intense physical exercise, swimming, being suddenly startled or badly frightened.
It’s estimated that 4,000 children and young adults die yearly of Long QT. It is a common cause of sudden death among school athletes, as well as the cause of many unexplained drownings. The first sign may, unfortunately, be sudden cardiac death. The heart muscle abruptly goes into fibrillation, beating too fast and so ineffectively that the blood stops circulating. The heart has to be defibrillated (shocked back into a normal rhythm) within a few minutes if the person is to survive. Early diagnosis is essential. Drugs called beta blockers can help to maintain a normal heart rhythm in many cases. In the remaining cases, a pacemaker can be implanted to set the heart’s rhythm, or an implantable cardioverter defibrillator can be put in that can help to detect and correct an abnormal heart rhythm.
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