Patients Resources

How Are Arrhythmias Treated?

There are dozens of arrhythmias that differ vastly in their symptoms severity, clinical prognosis, and available treatments.  For each arrhythmia, frequently, there can be more than one therapeutic options.  These factors can result in a bewildering array of treatment choices and professional opinions, creating a great deal of confusion for patients.  This is especial true for patients who have sought multiple "second opinion" consultations.  It is not unusual for these patients to become even more confused and more indecisive after each additional second opinion consultations he or she went to.

It is often said that medicine is an "art."  In other words, diagnosis and therapy for many medical conditions, including arrhythmias, are not always "black and white."  There are "judgment calls" and variation in professional opinions.  Therefore, it is probably not possible that any two physicians would give identical opinions for any medical condition, except for a very select few conditions where it is clearly a "life and death" situation.  For many conditions where treatments are elective or semi-elective, there can be many equally viable treatment options.  The choice is often made by the patient in conjunction with their physicians.

This section on the treatments of arrhythmia is, therefore, not meant to provide an answer to every arrhythmia, but rather to discuss the general principles of treating arrhythmias.  Certain myths in treating arrhythmias are also discussed.  This is then followed by detailed discussion on specific treatment procedures in Cardiac Electrophysiology.


General Principles of Treating Arrhythmias:

Frequently, there can be as many different opinions regarding treatment options for any given arrhythmia as there are physicians willing to provide them.  However, there are some general principles and guidelines that most physicians do agree on.

1) Primum non nocere.  

This Latin phrase translates to "First, do no harm," which is the first and foremost principle that all physicians agree on and adhere to.  With whatever treatment recommendation a physician prescribes, either medical or surgical, the patient should not be harmed as a result.  Medical treatments are meant to help, not worsen, the medical condition.  However, one should keep in mind that there are practically no treatments that are completely harmless.  There are risks in every medication and every surgery.  (If someone tells you that a particular medication has "absolutely no side effect," he or she is not being truthful about it.)  The important principle is that if the treatment should not be worse than the disease itself.  This is where "risk/benefit analysis" comes in.

2) Risk/Benefit Analysis. 

This is a basic principle that applies not only to Cardiac Electrophysiology, but practically in every aspect of Medicine.  The rule is very simple.  Whenever one considers a treatment option, the benefits of the treatment must outweigh the potential risks (side effects, complications, etc) of the treatment.  A very common example is chemotherapy for cancers.  This therapy is well known to be "toxic."  Without the toxicity, it simply can not kill the cancer cells.  However, there are very few chemotherapies that are so specific as to kill only the cancer cells, not healthy normal cells.  This "collateral damage" is why patients frequently lose their hair and have dangerously low white blood cells during chemotherapy.  But most patients and physicians will happily embrace chemotherapy because without it patient may die.  In other word, one is willing to accept a "toxic" therapy because the disease is worse than the treatment.  In the case where the treatment is worse than the disease, the treatment would not be a good one.

As the above example shows, the more serious a medical condition is, the more one would be willing to accept a treatment option with potentially higher risks.  Unfortunately, as it turns out, the risk of treatments for more serious conditions usually are higher compared to those for less serious conditions.   An example would be Tylenol for headache and chemotherapy for leukemia.  Again, one would accept a treatment with potentially higher risk if the potential benefit is higher.

This general principle applies to Cardiac Electrophysiology as well.  An arrhythmia such as PAC carries a completely benign prognosis.  Patients usually have no symptoms or have minimal symptoms.  Therefore, the threshold for treating these patients with any medications that have serious side effects would be very high.  Most patients would be treated with milder medications, which may be less effective, but less risky.  Patients would have to be severely symptomatic in order to take on the risk of taking the more effective, but potentially more toxic, medications.   On the other hand, an arrhythmia like ventricular tachycardia is life-threatening and carries an ominous prognosis.  Therefore, one would be willing to accept more aggressive treatment options, even those with potentially higher risks, because the ultimate benefits outweigh the risks. 

Similar to the example of Tylenol versus chemotherapy, the more effective a treatment is in Cardiac Electrophysiology, the more potential risk.  This is easy to understand.  An extreme example would be a patient with an arrhythmia who chooses to treat himself with nothing.  This "nothing" will have less side effect than a medication like amiodarone, but would be far less effective in controlling the arrhythmia.

The above paragraphs discussed how we choose treatment options based on risk/benefit analysis.  The following section discusses why we treat any medical condition.  There are only two reasons to treat a patient, for any ailment, for any condition, in any specialty.  First is to alleviate symptoms (section 3).  The second is to prevent morbidity and mortality (section 4), even in patients without symptoms.  There are NO OTHER REASONS TO TREAT A PATIENT.  A treatment is recommended to help a patient, either by reducing the symptoms or by improving the outcome (e.g. longevity of patient) .  If the patient has no symptoms and the condition is not helped by the treatment, then there is no role for the treatment.

3) Treating Symptoms

With few exceptions, patients come to a physician because of symptoms.  In Cardiac Electrophysiology, the most common symptom is palpitation, racing heartbeats, or fainting spells.  The primary goal for any treatment, therefore, is the alleviation of symptoms, taking into consideration the "risk/benefit" ratio.  Take PAC again for example.  This benign condition should be treated if patients have significant symptoms of palpitation, which may be extremely disabling and troublesome for some patients.  In these cases, one may accept a treatment that may have potential side effects as long as the benefit outweighs the risks.  Management of another condition,SVT, which can cause disabling symptoms, is also governed by the same principle.  A patient with this condition who has frequent attacks and multiple ER visits would best be served with a treatment like radiofrequency ablation which can eliminate the source of SVT and cure this condition.  Both PACs and SVTs are considered "benign" conditions, as they usually do not lead to fatality.  Therefore, reason for treating these conditions is alleviation of symptoms.

4) Preventing Morbidity and Mortality

This second principle of treatment is just as important, if not more important, than treating symptoms.  One of the central goals in medicine is prevention of premature deaths, an example of which is high cholesterol treatment.  Most patients with high cholesterol do not have any symptoms specific to the condition of high cholesterol because there is none.  However, high cholesterol level can cause hardening of the arteries and heart attack; most physicians would consider treatment of high cholesterol mandatory even though these patients have no symptoms whatsoever.  Cancer screening (breast, colon, prostate, etc) in asymptomatic high risk patient is another example. 

In Cardiac Electrophysiology, the same principle holds for the management of arrhythmias.  Treatment with coumadin for prevention of stroke in atrial fibrillation is a classic example.  Atrial fibrillation is one of the most common preventable causes of stroke and the treatment with coumadin, a blood thinner, can prevent stroke.  In this case, Coumadin does not improve symptoms of patients with atrial fibrillation whatsoever, but it is one of the most important treatments because it prevents a devastating morbidity and potential mortality of atrial fibrillation. 

Similarly, recommendation for a prophylactic (preventative) defibrillator implantation in high risk patients who may have not any symptom is another important example of this principle of treatment.  Cardiac patients with severe dysfunction of their heart are at high risk for sudden cardiac death.  They can be completely asymptomatic until they actually suffer an event, by which time it is too late.  Ironically, when patients do suffer sudden death, they frequently have no symptoms because death is instant.  Thus, it is obvious why one does not wait for symptoms of sudden death to occur before recommending a defibrillator.

5) Physician Experiences

Even though every physician strives to provide the best treatment recommendation for his or her patients, there are many factors that influences the physician's opinion, one of which is his or her own anecdotal experiences.  A physician who recently referred a patient for a surgery and the patient suffered a complication may be "gun-shy" the next time he or she considers referring a similar patient, even though it may have been a 1 in a 1000 occurrence of that complication.  On the other hand, a physician who never referred any patients for certain procedures probably does not have sufficient experience to make any reasonable recommendation for or against the procedure. 

The experience of the physician or surgeon performing a certain procedure is also critically important.  A physician or surgeon who has performed a large number of certain procedure would be more comfortable with that procedure, and consequently more inclined to recommend it than another physician who has little or no experience with it.  The latter physician may recommend an alternative procedure which he or she is more experienced with but which may or may not be a superior procedure than the first one.  Asking your physician and surgeon about his or her clinical experience is a completely legitimate (though sometimes embarrassing) question to ask at the time of your consultation.


Myths in Treating Arrhythmias:

1) My neighbor had it done.  Why Can't I? 

Even though all men are created equal (not really), all arrhythmias are not.  Just because your neighbor had a certain procedure done for his arrhythmia and he is feeling great, it does not mean that you have the same condition or that you will benefit from the same procedure.  There are many different arrhythmias, and treatment options vary dramatically from one arrhythmia to another.  Your physicians, not your neighbor, would be a better person to provide medical recommendation.

2) My friend had a friend who died after a defibrillator.  I will never have one myself.

This myth, unfortunately, is another one that influences patient decision on medical therapy, sometimes more so than any other factors.  Patients sometimes trust the medical opinion of a friend or a neighbor more than that of their physician.

Every treatment, every medication, and every surgery has its inherent risks, but the mere presence of risks does not mean that one does not accept the treatment (see risk/benefit analysis section).  To decline a procedure simply because it has some risks is like giving up driving a car because there is the risk of car accident (unless, of course, the risk is so high because of the driver or the car.  Here the problem is the driver or the car, not "driving" per se).

Furthermore, cardiac patients who undergo procedures are generally very sick and elderly patients.  It is not unexpected that some patients can still die after a defibrillator is implanted (This does not mean that the defibrillator caused the death; risks of death from a defibrillator surgery is in the order of 1 in 1000 or less).  On the other hand, there are countless number of patients whose lives have been saved by the defibrillators and these stories do not always make the "headlines."  Like every field in medicine, one must consider boththe benefits and the risks, not just the risks, in deciding on any medical intervention.

3) I get bruises easily.  I can't take coumadin

Again, risk/benefit analysis should be considered in any medical decision, including that for medications like coumadin.  Coumadin in high risk patients can prevent a devastating stroke.  The risk of not taking coumadin (stroke) is significantly greater than the risk of taking it (bruises).  For most patients, having a stroke is worse than having skin bruises or other bleeding complications, unless you have a modeling career.

4) I won't take that rat poison! 

Coumadin is a blood thinner and it is derived from rat poisoning.  It is currently the standard of care in patients at high risk for stroke, such as atrial fibrillation or mechanical valve.  It's level must be carefully monitored and dosage adjusted according to the level (seecoumadin clinic).  Although rats do die from rat poisoning, there are important differences between rat poison and coumadin.  Rat poison are given to rats in toxic and lethal dosages to cause massive bleeding, whereas coumadin is administered in tightly titrated dosages.  In carefully monitored patients, coumadin is extremely safe.

5) I don't want any machine in me!

Many therapies in Cardiac Electrophysiology consist of implanting high-tech medical devices, such as pacemaker or defibrillator.  Patients sometimes jokingly refer to themselves the "bionic man."  Having a "machine" implanted in the body, however, is neither a new concept nor particularly unusual.  Patient with broken bones or severe arthritis have had metal prosthesis implanted for decades.  We live with and around machines everyday, including watches, cell phones, computers, automobiles, and hearing aids.  Pacemakers and defibrillators are just sophisticated "machines" that are implanted inside the body to improve our health, not much different than those outside the body that improve our lives.

6) It's not "natural." 

Many patients who subscribe to the "natural" theory of healing their medical conditions are strong opponents of many therapies in Cardiac Electrophysiology.  Clearly, all medications are "synthetic" and no treatment is "natural."  The only thing natural is to let the condition run its natural course (physicians call this "natural history of disease").  Every human intervention to alter the natural history of a disease is, by definition, "unnatural."  For argument sake, here are a few examples of "natural" things in life: bacteria, virus, pneumonia, and "natural disasters" like earthquake and tsunami.  And here are some examples of "unnatural" or synthetic things: antibiotics, nurses, doctors, hospitals, cars, phones, computers, and houses.  Your reading this paragraph on an LCD screen over the internet is not "natural."


Hospital Based Procedures for Treating Arrhythmias

The previous paragraphs discussed general treatment principles in dealing with arrhythmias.  The following section goes into detail about some of the more commonly performed Electrophysiology procedures.  Not every procedure is meant for every patient with arrhythmias, and not every patient will need a procedure.  This section deals only with procedures themselves, most of which are invasive and hospital-based.  For specific treatment options for each arrhythmia type, please refer to the section on "Different Types of Arrhythmias."


Electrophysiology study (EPS).

This invasive study is generally needed for patients whose causes for fainting or severe palpitation remain unknown despite extensive noninvasive evaluations.  It is also useful to differentiate the various causes for a documented episode of arrhythmia.  It can be used to risk-stratify certain patients with known or suspected arrhythmias.  Lastly, it is performed in conjunction with radiofrequency ablation, as a mean to confirm the mechanism of the arrhythmia before performing curative ablation.

The procedure is performed in a hospital setting in the cardiac catheterization laboratory, the same facility where coronary angiogram and angioplasty are performed.  Under sedation, lidocaine (or equivalent local anesthetics) is injected into the skin.  Several catheters are then inserted into veins in the groins and into the heart (see picture), after which electrical stimulation of the heart is performed through these catheters by the Electrophysiologist.  These electrical stimulation can reveal an underlying electrical conduction problem such as slow heartbeat or heart block, as well as reproducing and confirming the cause of a rapid heartbeat.  For patients with rapid heartbeat problem, they do not necessarily have to be in their arrhythmia at the time of the procedure since this test can "provoke" the dormant arrhythmia.

If a slow heartbeat is documented, one can prescribe the appropriate treatment, usually a pacemaker.  If a fast heartbeat is confirmed, there are several treatment options, depending on the type of rapid heartbeat discovered.  For some rapid heartbeat that are potentially life-threatening, such as ventricular tachycardia, an implantable defibrillator is required.  On the other hand, for many other forms of rapid heartbeats, such as SVT, the arrhythmias can be "mapped" to determine the exact source of the problem, which is usually an "extra nerve" in the heart.  In the majority of these cases, ablation can successfully eliminate the culprit of the arrhythmias, resulting in a long-term permanent cure for the patient.

Thus, an Electrophysiology study is a diagnostic study that helps the Electrophysiologists confirm the root of the suspected electrical problem of the heart.  It serves as a gateway to other therapeutic modalities available to treat the arrhythmias.

Many patients who have serious symptoms from their rapid heartbeat, such as fainting or near-fainting, may be very reluctant to have a test which can provoke their arrhythmias, for fear of reproducing the frightening sensation.  Reproducing the arrhythmia, however, may be the only way to confirm the causes of their conditions in most patients.  Furthermore, there is no safer place to have an arrhythmia than in the cardiac catheterization laboratory, under the direct care of a Cardiac Electrophysiologist, and in the presence of an entire team of personnel specializing in the chronic as well as emergency treatment of arrhythmias.  It is better to find it here than to have it occur "naturally" at home or while driving on the road.

In contrast to an coronary angiogram, which is a procedure designed to look for clotted arteries of the heart (coronary arteries), an Electrophysiology study is not meant to evaluate the patency of patient's arteries.  But rather, it focuses on the evaluation of the electrical health of the heart.  One, therefore, can not tell "if the arteries are blocked" by this test.  This is the job for your general or interventional cardiologists.


Radiofrequency ablation (RFA). This is a cardiac procedure specifically designed to treat and cure certain types of arrhythmias (see sections on supraventricular tachycardiaWolff-Parkinson-White Syndrome, and atrial flutter). 

Ablation is a procedure of selectively destroying certain tissues of the body to cure or control a disease process.  An ablation can be performed for seizure focus in the brain or for certain masses in the liver, or for abnormal electrical activities in the heart.  Cardiac ablation refers to ablation specific to the heart rhythm problem.  The most common source of energy for cardiac ablation is radiofrequency and thus the most common term for this procedure is "radiofrequency ablation," although other sources of energy have been used.

For cardiac ablation, very thin catheters are placed into the heart via large veins in the groin and sometimes in the neck (see picture above).  This is why the procedure is also called "trans-catheter ablation," to distinguish it from open-heart surgical ablation.  The procedure is done much like that of an Electrophysiology study, which is first performed to identify the source of the arrhythmia.  "Mapping" is done to localize the source of the problem, after which ablation is performed targeting and selectively destroying the areas that are responsible for the arrhythmias.

For the purpose of discussion on this website, the term "radiofrequency ablation" means cardiac ablation procedures performed "percutaneously," or "endocardially" through a catheter (trans-catheter).  In other words, they are performed by a minimally invasive technique via a vein or artery through the skin (percutaneous), not by an open-chest or open-heart surgery.  The approach is from inside the heart (endocardial), because the catheters enter the heart on the inside, as opposed to outside the heart (epicardial) as in open-heart surgery.  In the latter case, the approach is through a surgical opening in the chest and these epicardial ablation procedures are done by cardiothoracic surgeons, not by Cardiac Electrophysiologists.

Cure rates for most forms of arrhythmias by radiofrequency ablation range form 80% to 98% (please see sections on specific arrhythmias for individual discussion).  Complications rates are low, with mortality less than 1 in several thousand and very small risks of bleeding and perforation.

For many types of arrhythmias, radiofrequency ablation is increasingly accepted as an preferred therapeutic alternative to chronic therapy with medications.  It is considered first-line therapy for most curable arrhythmias such as supraventricular tachycardiaWolff-Parkinson-White Syndrome, and atrial flutter. 


3-Dimensinal Mapping..  This is a specialized mapping technique which utilizes a computer to delineate the source of complex arrhythmias.  It works by projecting a virtual 3-demensional image of the heart in the computer to help the Cardiac Electrophysiologist navigate his catheters, in ways very similar to what GPS does for driving a car or flying an airplane.

For many types of ablation, such as those for atrial fibrillation, 3-D mapping is essential to ensure optimal success rates and safety for the patients.  For further discussion on this technology, please click this link to St. Jude Medical.


Cardioversion. This is a procedure used to electrically convert a sustained abnormal heart rhythm back to the regular normal rhythm (normal sinus rhythm).  The most common arrhythmias that require cardioversion is atrial fibrillation or atrial flutter, although sometimes ventricular tachycardia may need to be treated with cardioversion on an emergency basis.. 

Under anesthesia, an external electrical shock is applied to the heart through the chest. An external defibrillator is used to deliver the shock through its "paddles."  The electricity that is transmitted through the chest into the heart will instantly stop an arrhythmia and restore normal regular rhythm. The risk of the procedure is fairly low.  Other than the risk of minor skin burn and some risks associated with light anesthesia, the procedure is very safe, effective, and easy to perform.  One risk that deserves mention is that of blood clot and stroke in patients with atrial fibrillation or flutter who undergo cardioversion.  The risk is negligible if patients with these conditions have previously been treated with a blood thinner, or coumadin.  One should not proceed with cardioversion if one has not been therapeutically treated with coumadin for at least 3 weeks, unless an ultrasound of the heart done through the esophagus is first performed (trans-esophageal echocardiogram) to rule out the presence of a clot in the left atrium.


Pacemaker (PM). A pacemaker's is a medical device used to regulate the heart rate and to keep it from beating too slowly. Therefore, the most common indication for a pacemaker in a patient is slow heartbeat or heart block.  Patients with atrial fibrillation and fainting spellsdue to slow heart rate are also candidates for pacemaker implantation.  The latest indication for pacemaker is cardiac resynchronization therapy for pacing with congestive heart failure.

A pacemaker system consists of the "pulse generator" and the "lead."  The pulse generator is where the battery and the electronics reside.  It is the "brain" of the pacemaker.  It is connected to a "lead," or a wire, through which the "brain" of the pacemaker communicates with the heart.  The connection between the lead and the pulse generator is called the "header."

Most pacemakers in use today are "dual chamber" pacemaker because they utilize two electrodes, which are placed respectively in the atrial and ventricular chamber, thus "dual chamber." (See anatomy and physiology section).  The advantage of such a system is that is preserves the normal physiology of the heart, i.e., normal relationship between the upper chamber and lower chamber.  A "single chamber" pacemaker uses only one electrode, which can be placed in either the atrium or the ventricle.  A single chamber pacemaker is less frequently used in the U.S. because it does not preserve the normal relationship between the upper and lower chambers of the heart.  A single chamber pacemaker is most commonly used when when such a normal relationship is no longer present in patients with chronic atrial fibrillation.

During surgical implantation of the pacemaker system, the leads are inserted through the vein on the chest.  They are subsequently placed permanently inside the chambers of the heart whereas the "pulse generator" itself is implanted on the chest just under the skin (subcutaneous).  Because the procedure is done transvenously (through the vein), it does not require an open heart surgery. This surgery can be completed in as short as 20 minutes and is associated with reasonably low risks and rapid recovery (see also frequently asked questions section).

Major complications are rare but may include cardiac perforation, pneumothorax (air leak in the lung), vascular injury, and hematoma (blood clot).  Infection of the pacemaker may occur in 1 percent of the time which will require explantation of the entire pacemaker system.

While older generations of pacemaker has only one function and that is pacing the heart, newer generations of pacemakers have the added capability of cardiac resynchronization therapy (CRT). They can be used in patients without slow heartbeat but who suffer fromheart failure refractory to standard medical therapy.


Implantable Cardioverter Defibrillator (AICD or ICD). A defibrillator is a medical device whose primary function is to shock the heart when the heart has gone into a very rapid and life-threatening arrhythmia such as ventricular tachycardia.  Its secondary function is to pace the heart when the heart rate is too slow. 

A frequent question that comes up is whether a particular device is a "defibrillator" or a "pacemaker" or a "combination."  A pacemaker simply paces the heart when it is too slow.  It has no defibrillator function, i.e., it can not "shock" the heart in the case of an emergency.  A defibrillator, on the other hand, can pace the heart when it is too slow, and shock the heart when it is too fast.  All defibrillators today can also work as pacemakers, and therefore the concept of a "combination" pacemaker-defibrillator is no longer relevant.  There are no defibrillators today that work only as a "shock box" without full pacemaker capability.  The converse, however, is not true.

A defibrillator is used to treat patients with life-threatening arrhythmias.  When first invented in the 1980s, defibrillators were reserved for patients who have already suffered a cardiac arrest or have documented serious arrhythmias.  However, most defibrillators today are implanted on a prophylactic basis, i.e., preventatively.  In other words, they are implanted in patients at high risk for a serious arrhythmia and cardiac arrest but who have not yet suffered such an event.  While this idea may be difficult for some patients and even some physicians to accept, prophylactic defibrillator implantation is no different, conceptually, than treating hypertension or hypercholesterolemia for prevention of heart attack.  One does not wait for cardiac arrest to occur before implanting a defibrillator, just as one does not wait until a full blown heart attack to take place before treating patient's elevated blood pressure and cholesterol.  Current recommendation is for defibrillator implantation in patients with an ejection fraction less than 35%.

The anatomy of a defibrillator is very similar to that of a pacemaker, except that the size of the pulse generator and the electrodes are significantly bigger and the structures more complicated.  This is because the defibrillator needs to deliver higher energy to shock the heart than what is required to pace the heart.  The placement of the electrodes inside the heart is also more critical that that for the pacemaker because the effectiveness of the "shock" function depends greatly on the location of the electrodes.

Similar to pacemakers, defibrillators are inserted transvenously (through the vein) and therefore do not require an open heart surgery. Surgical risks are similar to those with pacemaker (see also frequently asked questions section).

 

Once implanted, a defibrillator monitors every single one the patient's heartbeat, day in and day out, 24/7, for any serious arrhythmia.  The very second the heart slips into a dangerous rhythm like ventricular fibrillation (left side of the above diagram), the defibrillator instantly recognizes the problem, charges up its capacitors, and delivers a high voltage shock to the heart to restores regular rhythm (right side of the diagram).


Cardiac Resynchronization Therapy (CRT). This is a percutaneous (through the skin) surgical procedure specifically for the treatment of patients with severe congestive heart failure.  In patients with heart failure, the left ventricle is enlarged and the time it takes to activate the entire heart may be significantly increased, leading to "dyssynchrony," or lack of synchronized or coordinated contraction of the heart.  This usually manifests itself as abnormal EKG with either right bundle branch block or left bundle branch block.  The larger the heart and the greater the degree of dyssynchrony (as assess by echocardiogram and EKG), the more one would benefit from CRT.  CRT works by pacing both the right and left side of the heart simultaneously, shortening the time to activate the heart and restoring "synchrony" to the heart, thus the term "Cardiac Resynchronization Therapy (CRT)."

A CRT device can be a CRT pacemaker or a CRT defibrillator.  Most CRT devices implanted in the U.S. are the defibrillator type because most patients with heart failure who need CRT will also need a defibrillator.  A CRT device works by having a "third wire" capability to pace the left side of the heart.

Ordinary pacemakers and defibrillators come with two wires, one in the right atrium and one in the right ventricle (RV).  CRT pacemakers and defibrillators have an extra wire which goes into the left ventricle (LV), via a vein in the back of the heart called "coronary sinus."  The branches of the coronary sinus are called "coronary veins," through which the "third-wire" is placed in order to pace the left side of the heart (see diagram below).  Simultaneous pacing of both right and left ventricle can be performed through these wires in order to "resynchronize" the heart.  This can result in dramatic improve symptoms of heart failure for those patients with heart failure and dyssynchrony.  Most patients with CRT implantation will experience improvement in their breathing, stamina, and exercise capacity.  The ejection fraction and other important parameters of the heart may also improve.

For a CRT defibrillator, the CRT portion of the device is an added feature of the unit.  In other words, the device can provide CRT while still functioning as a defibrillator.  A standard two-wire defibrillator works as a defibrillator without CRT function.

Although CRT has been available since the late 1990s, it has only recently gained wide-spread acceptance and popularity following the publication of several large landmark clinical trials which demonstrated significant improvement in heart failure patients who have received CRT.  Today, CRT is considered a standard of care for patients with heart failure and evidence of dyssynchrony, who continue to have refractory symptoms of heart failure despite optimal medical treatment.

Risks of the surgery is similar to those of the pacemakers and standard defibrillators.  The additional "third wire" placed in the left side of the heart used to be a critical step that was difficult to achieve and took many hours.  Today, with improved technique and equipment, the deployment of the "third wire" for CRT may take as few as an extra 10 minutes compared to the standard pacemaker or defibrillator.