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Using electricity to regulate heart rhythms in not a new idea, pacemakers have been around for 40 years. But treatments such as cardiac resynchronization therapy (CRT) and implantable cardioverter defibrillator (ICD) therapy offer cutting edge hope for an old problem. Heart health expert Dr. William T. Abraham, explained how it all comes together during our Body Electric Cyberconference.
Moderator : Welcome, Dr. Abraham. For many people, the paddles used on ER, or perhaps a relative's pacemaker are the extent of their knowledge of electrical devices used for the heart. Can you enlighten us?
Abraham: First, let me mention that the heart is not only a mechanical organ; the heart is also an electrical organ, as well. That is, the heart has an electrical system, and that electrical system helps to keep the heart in rhythm and helps to keep the walls pumping in a coordinated and simultaneous fashion. Thus, the heart's electrical system is critically important to the normal functioning of the heart.
In this regard, newer devices have been designed to either strengthen weak hearts or to terminate episodes of life threatening heart arrhythmias. These devices are called cardiac resynchronization devices and implantable cardioverter defibrillators, respectively. For the sake of today's discussion, we'll use the abbreviations CRT and ICD.
Moderator: So one therapy gets the heart started and the other keeps it going?
Abraham: Correct. They are different therapies, but sometimes both are used in a complementary fashion in the same patient. For example, patients with congestive heart failure may have weakness of the heart muscle and abnormalities of the heart's electrical system, which requires treatment with both CRT and an ICD. The CRT is intended to strengthen the heart, and the ICD is used only when necessary to pace or to shock the heart out of a dangerous irregularity of heart rhythm.
Moderator: How is the ICD different than a pacemaker?
Abraham: The ICD does pace the heart, or can pace the heart, but it also can shock the heart, similar to those paddles that we see used on television shows in the emergency department. The ICD is an internal (shock box) that can resuscitate patients from episodes of cardiac arrest. So the ICD offers heart disease patients great protection from sudden cardiac death or cardiac arrest.
Member question: How does the doctor decide when to use CRT alone or when to use CRT with ICD?
Abraham: CRT is used to treat weak hearts, and ICDs are used to treat patients at risk for cardiac arrest. These two situations overlap in many patients, and those patients should receive a device that combines both features.
On the other hand, some patients have an indication for an ICD, but do not have the electrical problem that is treated by CRT. Those patients will receive an ICD alone. Other patients have the electrical abnormality and weakness of the heart that is improved by CRT, but are not at high risk for cardiac arrest and they may receive CRT alone.
In reality, the indications for these two therapies are becoming more and more overlapping so that most patients will get a combined device, including CRT and ICD capabilities.
Member question: Are pacemakers used anymore? How are the new devices different?
Abraham: Standard pacemakers, which have been around for approximately 40 years, are still used to treat certain types of heart disease. Standard pacemakers are used primarily to treat heartbeats that are too slow and also treat instances in which there is a short circuit in the electrical system. In this way, pacemakers help maintain the normal rhythm and rate of the heart.
In the case of CRT, the heart rate and rhythm may be normal. CRT is used to strengthen weak hearts. In the case of an ICD, heart rate and rhythm may be normal most of the time, but occasional unexpected or sudden abnormalities in the heart rate or rhythm require temporary pacing or an electrical shock to correct.
Member question: Are implantable devices a last resort, or are they an option for anyone with heart failure who is resistant to the idea of taking drugs for the rest of their life?
Abraham: These new devices are used in addition to medications. The effect of CRT to improve heart failure is complementary to drug therapies. So CRT does not replace drug therapies, it is used in addition to drug therapies to further improve heart function and patient well-being. It is not used as a last resort and should be considered in patients on medical therapy who continue to be limited by symptoms such as shortness of breath and excessive fatigue.
Member question: What is the procedure for implanting these devices? How invasive is it?
Abraham: The procedure involves a minor surgery and is done in a heart catheterization laboratory. The devices are generally implanted just under the skin and just below the collarbone, and some wires are threaded through the veins of the body into the heart. The procedures generally take an hour or two. They are done with local anesthesia and patients are generally discharged from the hospital the following day.
Member question: With CRT -- how does it work? And how long does it take to have an effect?
Abraham: CRT works by re-synchronizing the contraction pattern of the heart. In normal hearts, the electricity passes through the pumping chambers very quickly, signaling all of the walls of the heart to squeeze simultaneously. In diseased hearts, the electricity passes through these pumping chambers much more slowly, thus some of the walls of the heart are squeezing, while other walls are relaxing, and this uncoordinated pattern of contraction decreases the ability of the heart to pump blood.
In the case of CRT, wires are threaded to both the right side and the left side of the heart. By stimulating both sides of the heart simultaneously, the walls of the heart begin to contract together again. This improves the function of the heart immediately; however, the benefits of CRT continue to grow over a period of about six months. During that period, in most patients, the heart continues to get stronger and stronger.
Member question: How permanent are such implanted devices?
Abraham: These implanted devices are permanent. Any limitation in their permanence is related to battery life. With modern battery technologies, most CRT and ICD devices will last about five to seven years. When the battery gets low, the heart doctor will simply replace the pacemaker device, which is implanted just under the skin
Member question: Here's my worry about these devices ... they bring a person back to life who will then have a poor quality of life until the next heart attack claims them. Or do they work better than that?
Abraham: This is an excellent question. How do we balance quality of life with duration of life? In the treatment of patients with heart disease or heart failure, we try to achieve both goals; that is to make patients both feel better and live longer. In this regard, CRT and ICDs are complementary. CRTs clearly make patients feel better, and ICDs help patients to live longer.
Member question: Is there an age limit for considering such devices?
Abraham: There is no age limit, per se. Physicians tend to base medical decisions regarding implantable devices based on the overall health of the patient, rather than on age alone. For example, patients in their 80s or even 90s who are otherwise healthy, except for their heart disease, may be considered good candidates. On the other hand, younger patients with many additional medical problems might be viewed as poorer candidates for such implantable devices.
Member question: What lifestyle changes or possible risks does one have to deal with after implantation?
Abraham: The good news is that very few lifestyle changes are required. Modern implantable devices are well shielded so there is less concern about the effects of interference from appliances, such as microwave ovens. Strong magnetic fields can affect the devices, so patients with these devices cannot undergo MRI scans. They also require to be hand patted down at airports rather than having the wand used by security personnel passed over the device. Otherwise, there are really very few cautions or limitations associated with these devices.
Member question: What is your experience with ICDs for long QT?
Abraham: Long QT syndrome may be an inherited abnormality of the heart's electrical system that predisposes people to episodes of cardiac arrest. In patients who have had cardiac arrest, a defibrillator is warranted. However, many patients with long QT syndrome will never experience an episode of cardiac arrest and so an ICD should not be placed in all of them.
If you have or know someone who has long QT syndrome, you should be evaluated by a cardiac electrophysiologist, a heart doctor that specializes in the electrical system of the heart.
Member question: Sudden cardiac arrest is very scary. My kids watch the commercials with me and want me to buy the emergency device. Is it wise for every family to have one?
Abraham: The question is in reference to the automatic external defibrillator, AED. These devices are now found in many public places, such as shopping malls and airports. They are a sophisticated version of the older defibrillators used in hospitals, the ones we see in television shows and movies, when the paddles are placed upon the chest. An AED can make a simple determination about a possible heart arrhythmia, and deliver a shock externally without the need for sophisticated medical decision-making. They have been shown to improve the chances of survival for cardiac arrest that occurs outside of the hospital.
I urge patients and families with heart disease to at least learn basic CPR. For those who are at risk for cardiac arrest and can afford these costly devices, an AED would add some additional benefit in the event that cardiac arrest occurs.
Member question: With all of these defibrillators in the airports for example, isn't there a risk of someone attempting to use the device who does not know how and then causing more problems?
Abraham: The good news is that the devices have sophisticated diagnostic capabilities. When the patches or paddles are placed upon the chest the device analyzes the heart rhythm and will only administer a shock if necessary. The devices require very little thinking or knowledge on the part of the operator.
Member question: Will CRT reduce or eliminate the need for heart transplants?
Abraham: CRT has recently been shown to reduce the need for heart transplants in some patients. Heart failure is a chronic and progressive disease. Many patients are made better with drugs and devices. In some instances, the need for transplantation may be avoided completely and in other cases, drugs and devices simply delay the need for transplantation.
Member question: Are there devices that can be used to monitor the heart's electrical activity over a period of time to diagnose better?
Abraham: All of these implantable devices -- pacemakers, CRT, ICDs -- have monitoring capabilities built into them. In addition, there are both implanted and external devices that are used for long-term monitoring of the heart rate and rhythm.
Moderator: Dr. Abraham, we are just about out of time. Do you have any final comments for us?
Abraham: I'd like to thank today's audience for the opportunity to interact with them. I am sure that there are still many questions and I would urge them to speak directly to their physician if they have further questions about these implantable devices.
Moderator: Thanks to Dr. William T. Abraham, for joining us, as part of the WebMD Body Electric Cyberconference. For more information, advice, and support, be sure to visit our message boards, where you can post questions and comments for fellow WebMD members and for our in-house experts.
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