• Heart Rhythm Disturbances (Arrhythmias)

    Overview

    Cardiac arrhythmias represent electrical disturbances of heart rhythm, which affect the normal activation sequence of the heart muscle. Such arrhythmias may or may not be associated with symptoms, and may range from single extra heartbeats, to abnormally slow heart rates (bradycardias), to sustained, possibly life-threatening rapid heart rhythms (tachycardias). Patients with heart rhythm disturbances that require treatment are typically referred by their physician to a cardiac electrophysiologist, a specially trained and certified cardiologist.

    Types of ArrhythmiasDr. David Martin and Dr. G. Muqtada Chaudhry

    Atrial Fibrillation

    Atrial fibrillation is the most common cardiac arrhythmia, affecting approximately 10 percent of people over the age of 80. It is becoming increasingly common in the younger population, however, and Lahey Hospital & Medical Center cardiologists commonly treat atrial fibrillation in patients in their 40s and 50s.

    Risk Factors

    The most common risk factor for the development of atrial fibrillation is a history of hypertension. Other forms of heart disease, such as valvular heart disease and heart failure, are also associated with this type of arrhythmia. The most common non-cardiovascular cause of atrial fibrillation in this country is alcoholism. Although alcohol abuse is widely recognized as a cause of liver disease, both binge drinking and chronically high levels of alcohol consumption can also lead to atrial fibrillation.

    Some patients experience atrial fibrillation without any underlying heart disease or other predisposition. More aggressive forms of therapy are being developed for these patients because they are often relatively young and experience severe symptoms.

    There are two main concerns regarding atrial fibrillation. The first is the risk for blood clot formation in the heart, which may lead to stroke or other complications. Blood clot risk is related to the age of the patient as well as the presence and severity of underlying heart disease. The second concern is that long-standing fast heart rates may lead to weakening of the heart muscle. Such weakening is irreversible in some situations, particularly in patients who experience little or no symptoms from atrial fibrillation, despite having very rapid heart rates.

    Assessment and Treatment

    Patients should be assessed on an individual basis for risk factors related to atrial fibrillation and the formation of blood clots in the heart. These risk factors include:

    • Being age 65 or older
    • Experiencing a previous stroke or transient stroke symptoms
    • Having a history of hypertension or diabetes

    If such factors are present, the main therapy is warfarin (Coumadin). We know from clinical trials that aspirin and other less powerful blood thinners are not effective stroke preventers in patients with significant risk.

    Another important aspect of atrial fibrillation treatment includes controlling heart rate, which is often quite rapid. Heart rate control may be achieved with medications such as beta-blockers or calcium channel blockers. Catheter ablation and pacemaker therapy are reserved for patients who do not respond to or tolerate these medications.


    An electroanatomic map of the left atrium produced during an ablation procedure to treat atrial fibrillationIn addition, anti-arrhythmic drugs have been used to maintain a normal heart rhythm, although their effectiveness is modest. For this reason, in patients who have severe symptoms and need to be at a normal rhythm, newer therapies, including catheter ablation, have been developed as an adjunct to medical therapy.

    Patients undergoing cardiac surgery for treatment of coronary artery disease or valvular disease can also be treated for atrial fibrillation at the time of surgery. This MAZE operation is usually quite effective in patients with both chronic and intermittent atrial fibrillation. Performed by Lahey Hospital & Medical Center's cardiothoracic surgeons, the MAZE procedure requires making incisions in the atrium that disrupt the re-entrant circuits. Once the incisions are made, they are sewn together again. The atrium can then hold blood on its way to the ventricle and can squeeze or contract to push the blood in to the ventricle, but the electrical impulse does not cross the incisions. The result resembles a children's maze in which there is only one path that the electrical impulse can take from the SA node to the AV node. The atrium can not longer fibrillate and the heart's normal rhythm is restored. The MAZE procedure, while unnecessary for most atrial fibrillation patients, is highly effective in restoring a normal heart rhythm.

    Generally, atrial fibrillation should be viewed as a long-term, chronic condition not unlike diabetes or hypertension. In only a few cases is atrial fibrillation amenable to curative treatment. Nevertheless, there is a broad range of therapies available including drug therapy, device therapy, and ablation therapy, all of which are designed to enable patients with this arrhythmia to experience an improved quality of life.

    Atrial Flutter

    Atrial flutter is a regular, rapid rhythm in the upper chamber of the heart. Atrial flutter and atrial fibrillation often coexist, but it is important to differentiate between the two arrhythmias because atrial flutter can be easily cured through catheter ablation. Considering that long periods of sustained atrial flutter may lead to progressive cardiac deterioration, we often recommend the use of catheter ablation – even in patients whose symptoms are relatively minimal. The elimination of atrial flutter will reliably prevent related cardiac deterioration from developing. Catheter ablation is the most effective therapy for the treatment of atrial flutter. It is performed on an outpatient basis, typically takes less than two hours, and the patient is usually discharged home following a four-hour recovery period. Less effective alternatives to catheter ablation include cardioversion and drug therapy.

    Supraventricular Tachycardia

    Supraventricular tachycardia is one of the common causes of sudden, rapid, regular palpitations. This disorder most often appears in otherwise healthy young people, but may also occur in middle aged and elderly patients. Supraventricular tachycardia is not life-threatening. Nevertheless, it may cause frequent and disabling symptoms such as palpitations and dizziness. It is important to document the arrhythmia using an electrocardiogram because the resulting information is helpful in guiding therapy. Supraventricular tachycardia is often caused by abnormal electrical conduction pathways present at birth, but which may not become active until later in life. These pathways, including those associated with Wolff-Parkinson-White syndrome, are curable through catheter ablation.

     Two most common forms of supraventricular tachycardia mechanisms 

    Most patients with supraventricular tachycardia experience minimal symptoms and require no specific therapy. They should, however, read provided information about how they may try to terminate episodes of arrhythmia once they begin. Patients that require treatment for more disabling supraventricular tachycardia symptoms may opt for drug treatment, which often consists of beta-blockers and calcium channel blockers. However, the definitive treatment for these arrhythmias is catheter ablation, which can offer a cure with a 98 percent or greater success rate.

    Ventricula Tachycardia

    A rapid heart rhythm originating in one of the lower chambers of the heart may be life-threatening, particularly if it is associated with other cardiac diseases or conditions such as a previous heart attack. Symptoms may be absent if episodes are brief, but when the tachycardia is prolonged, dizziness or fainting spells may occur.

    Ventricular tachycardia most commonly occurs in patients with some form of significant heart disease and requires immediate treatment as there is an associated risk of sudden death. For these patients, the only effective therapy is the implantation of an automatic defibrillator.

    In patients without any other heart diseases or conditions, ventricular tachycardia is typically benign and requires little therapy unless symptoms are present. Medications may be helpful in treating any symptoms that do appear. In addition, catheter ablation may offer a cure for some unusual forms of ventricular tachycardia.

    Treating Arrhythmias

    The heart with the left ventricle opened to show a catheter placed via the aorta during ablation Catheter ablation involves the targeted destruction of cardiac tissue to eliminate cardiac arrhythmias. Small wires are placed inside the heart using the veins, and sometimes the artery, in the groin area. The recordings from these wires allow physicians to precisely locate the abnormality responsible for the cardiac arrhythmia. A special wire is then placed against this cardiac tissue, and radiofrequency energy (cautery) is delivered at the site. This radiofrequency energy causes a tiny burn inside the heart no larger than a pinhead in order to eliminate the cells responsible for the arrhythmia.

    Catheter ablation is commonly used in the treatment of a wide range of cardiac arrhythmias, including supraventricular and ventricular arrhythmias, atrial flutter, and atrial fibrillation. In addition, this technique is sometimes used in combination with pacemaker implantation for the treatment of rapid atrial arrhythmias.

    Most procedures are performed on an ambulatory (outpatient) basis, and patients are usually discharged on the evening of the procedure. Follow-up after catheter ablation usually involves a return visit to the clinic within six to eight weeks, during which an electrocardiogram is performed.

    Complications from catheter ablation are uncommon. The most serious complication is the development of a heart blockage (due to damage to the normal conduction system in the heart), which may require the implantation of a permanent pacemaker in patients who otherwise would not need such a procedure. Patients should discuss the potential for individual complications with their electrophysiologist, who will be able to provide more detailed risk information.

    Implantable Defibrillators

    These devices were first introduced in the US in 1985, and ever since, have been widely accepted by patients and physicians. Implantable defibrillators automatically detect and correct unstable and unpredictable rapid heart rhythms. In doing so, they provide a safety net for patients at high risk for sudden cardiac death.

    Defibrillators are implanted in the upper chest, and the wires are placed in the heart through a vein that runs under the collarbone. The deSize comparison of original (top) and current (bottom) implantable defibrillatorsvice is no larger than a small bar of soap, and after a few weeks it is often unnoticeable to the patient. By automatically detecting the development of an unstable cardiac rhythm, implantable defibrillators can correct the problem using either pacing or shock therapies.

    Implantable defibrillators rely on a battery that typically lasts five to six years. Battery replacement is performed on an outpatient basis. Follow-up clinic visits are typically needed approximately twice a year. In addition, patients who do not receive shock therapy from their defibrillator within the first year following implantation are advised to undergo formal testing to ensure the device is functioning normally.

    Individuals eligible for defibrillator implantation include those who have been resuscitated from sudden cardiac death, have experienced previous heart attacks or have a left ventricular ejection fraction less than or equal to 30 percent. Such patients should talk to their cardiologist about whether an implantable defibrillator is appropriate for them.

    Pacemakers

    Size comparison of original (top) and current (bottom) pacemakersCardiac pacemakers have been used in various forms since the 1960s and provide reliable protection from abnormally slow heart rhythms. Pacemakers are often recommended for patients who experience dizziness or fainting spells related to slow heart rhythms or for those at significant risk for developing slow heart rhythms.

    Typically no larger than a silver dollar, pacemakers are connected to one or two wires that run through a vein under the collarbone into the heart. These devices typically last eight to ten years and generally require follow up visits twice yearly.

    Cardiac pacemakers have been used in various forms since the 1960s and provide reliable protection from abnormally slow heart rhythms. Pacemakers are often recommended for patients who experience dizziness or fainting spells related to slow heart rhythms or for those at significant risk for developing slow heart rhythms. Typically no larger than a silver dollar, pacemakers are connected to one or two wires that run through a vein under the collarbone into the heart. These devices typically last eight to ten years and generally require follow up visits twice yearly.

    Biventricular Pacing

    Pacemakers are increasingly being used for the treatment of congestive heart failure. Such pacemaker therapy is also referred to as cardiac resynchronization because it involves placing an additional pacing wire on the left side of the heart to improve the efficiency of the main pumping chambers. Conventional pacemaker wires stimulate the right atrium and right ventricle.

    Cardiac resynchronization pacemakers have been shown to significantly improve quality of life and functional capacity in certain patients with disabling symptoms related to congestive heart failure. Combination devices are available for patients requiring both an implantable defibrillator and cardiac resynchronization therapy. Patients who believe they may be suitable candidates for such a therapy should discuss this option with their cardiologist.

    Pacemaker and Defibrillator Clinic

    Florence Parella, MD, with patient in the Pacemaker ClinicThe Pacemaker and Defibrillator Clinic was established at Lahey Hospital & Medical Center to centralize the care of patients with implanted cardiac rhythm devices. The Clinic has two main functions: (1) to ensure the proper operation of implanted devices; and (2) to maximize the utilization of these devices to meet individual patient needs.

    The Pacemaker and Defibrillator Clinic is housed in the Department of Cardiology, located at both Lahey Hospital & Medical Center, Burlington and Lahey Medical Center, Peabody.

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