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What is an arrhythmia?
Normally, the heart beats in a consistent, coordinated rhythm, speeding up or slowing down in response to physical activity or to an emotional event. Various conditions can disrupt this pattern, causing the heart to beat either inappropriately slow or fast or in an uncoordinated manner. Any such irregular heartbeat is called an arrhythmia. Arrhythmias are very common, especially in older people. While some arrhythmias are harmless, others can be serious, leading to heart disease, stroke, or sudden cardiac death. Fortunately, most of these arrhythmias can be controlled with medicines, implantable devices such as pacemakers, or surgical procedures.
Anatomy of a heartbeat
The heart is a muscle that pumps blood around the body. It consists of four chambers — two atria at the top and two ventricles at the bottom — that contract (or beat) in a regular, organized rhythm. The timing of the heart’s rhythm is regulated by its own electrical system. Each heartbeat begins with an electrical impulse that originates at the sino-atrial (SA) node, a cluster of specialized cells located in the right atrium. This initial electrical impulse spreads through the walls of the right and left atria, which causes them to contract, pumping blood into the ventricles. The impulse then travels to the atrioventricular (AV) node, which acts as an electrical relay from the atria to the ventricles. The AV node delays transmission of the impulse, allowing the atria to contract fully and the ventricles to fill with as much blood as possible. When the electrical impulse then reaches the bundle of HIS, a network of electrical conduction fibers that transmit the signal to the ventricles, it causes them to contract in unison, pumping blood out of the heart and into the lungs and body. Finally, the SA node fires again, beginning a new heart cycle. The normal heart rate is between 60 and 100 beats per minute in resting adults. However, it is common for younger adults and athletes to have lower resting heart rates. One’s heart rate rises in response to such stimuli as exercise, pain, or anger. A heart rhythm is considered abnormal only when the heart rate is inappropriately fast (a condition known as tachycardia) or slow (bradycardia), or irregular, or when the electrical impulses veer from their usual pathways, causing the heart’s chambers to pump in an uncoordinated and inefficient manner.How Your Heart Works — An animated tutorial on the heart’s electrical system (from the National Heart, Lung, and Blood Institute).
The Division of Cardiac Surgery at NYU brings a multidisciplinary approach to the diagnosis and treatment of arrhythmias. Working closely with our colleagues in cardiology and interventional cardiology, we offer the full range of therapies, ranging from medications to implantable devices to surgery, including the latest technologies and minimally invasive surgical approaches. Our team has extensive experience with arrhythmias, treating hundreds of patients each year. We specialize in the care of arrhythmias in newborns, young children, and teenagers. Our team is also equipped to take care of complex and high risk cases, including the elderly, patients with multiple heart problems or diabetes, as well as those with pacemaker/defibrillator-related infections and non-working device leads. We also use minimally invasive techniques to place pacemakers and defibrillators.
Arrhythmias are classified by where they originate: the atria, the ventricles, or the heart’s electrical system:
- Atrial arrhythmias
- Ventricular arrhythmias
- Other arrhythmias
Abnormal heartbeats that originate in the atria, the heart’s two upper chambers, are known as atrial, or supraventricular, arrhythmias. These include:
A common arrhythmia, atrial fibrillation affects more than two million Americans. In this form of arrhythmia, the atria send uncoordinated electrical impulses through the heart’s upper chambers, causing them to beat in a disorganized, rapid, and irregular rhythm. The heart may beat as fast as several hundred times a minute. When properly controlled, atrial fibrillation is not life-threatening; however atrial fibrillation can lead to other conditions, such as chronic fatigue, heart failure, or stroke. The risk of stroke increases because in atrial fibrillation blood doesn't empty completely from the left atrium. This stagnant blood has a tendency to form clots, which can break loose as emboli, traveling to the brain and causing a stroke, or travelling out into the body clogging an artery.
Arial flutter is characterized by rapid electrical signals that cause the atria to contract quickly, producing an abnormally fast, steady heartbeat. This condition is typically more organized and regular than atrial fibrillation.
Premature atrial contractions
Premature atrial contractions are premature, extra beats that originate in the atria. This arrhythmia may feel as if your heart has “skipped a beat.” The heart doesn't actually skip a beat. Rather, the extra beat occurs sooner than normal. Premature atrial contractions are common in healthy children and teens. In most cases, there is no detectable cause and no treatment is needed. This arrhythmia may disappear as the child ages. It is not uncommon for this arrhythmia to occur due to excitement or the intake of caffeinated beverages. On occasion, premature beats are caused by disease or injury to the heart.
Paroxysmal supraventricular tachycardia
Paroxysmal supraventricular tachycardia (PSVT) is a very rapid heart rate that begins and ends suddenly. PSVT stems from problems with the electrical connection between the atria and the ventricles. More specifically, electrical impulses that begin in the atria and travel to the ventricles reenter the atria, causing extra heartbeats. PSVT is usually harmless. It tends to affect young people, and can occur during vigorous exercise. Treatment is considered only if episodes are frequent or prolonged. One form of PSVT is Wolff-Parkinson-White syndrome. In this syndrome, the heart’s electrical signals flow along an extra pathway between the atria and ventricles. These extra impulses affect the timing of the heart’s electrical signals, causing the ventricles to beat very rapidly. Wolff-Parkinson-White syndrome can be life threatening.
In atrial tachycardia, electrical signals arise from somewhere in the atria other than the sino-atrial (SA) node, causing an abnormally fast heart rhythm.
AV nodal re-entrant tachycardia
AV nodal re-entrant tachycardia is an abnormally fast heart rate due to an extra pathway that develops through the atrioventricular (AV) node.
Sick sinus syndrome (tachy-bradycardia)
When the sino-atrial (SA) node malfunctions, the heart rate slows down, resulting in a condition known as sick sinus syndrome. In some cases, the heart rhythm alternates between a slow rate (bradycardia) and a fast rate (tachycardia).
Abnormal heart rhythms that originate in the ventricle, the heart’s two lower chambers, are known as ventricular arrhythmias. These include:
Premature ventricular contractions
Premature ventricular contractions are premature, extra beats that originate in ventricles. This arrhythmia may feel as if your heart has “skipped a beat.” The heart doesn't actually skip a beat. Rather, the extra beat occurs sooner than normal. Stress, exercise, or excess caffeine or nicotine can trigger this form of arrhythmia. Other causes include heart disease or an electrolyte imbalance.
Ventricular tachycardia is a rapid rhythm that begins in the lower chambers of the heart. This condition prevents the heart from filling adequately with blood, reducing the amount of blood that is pumped through the body. This is a potentially serious arrhythmia, especially in people with heart disease, and requires prompt treatment.
In ventricular fibrillation, disorganized electrical impulses occur in the ventricles, causing the lower chambers of the heart to quiver. The ventricles are unable to contract effectively, preventing the delivery of blood to the body. A medical emergency, ventricular fibrillation must be must be treated immediately with cardiopulmonary resuscitation (CPR) and defibrillation, in which an electrical shock is delivered to the heart, restoring a normal rhythm; otherwise this is a fatal arrhythmia.
Long QT syndrome
Long QT syndrome is an arrhythmia that originates in the heart’s electrical system. “QT” refers to the section on the electrocardiogram (ECG) representing the time it takes for the heart muscle to contract and then recover. People with this syndrome are vulnerable to fast, chaotic heartbeats, often leading to fainting, cardiac arrest, or sudden death. In most cases, long QT syndrome is the result of a congenital disorder. However, many medications, as well as other medical conditions, may cause this arrhythmia.
Sinus node dysfunction
If the sinus node, the heart’s natural pacemaker is damaged (from surgery, drugs, congenital heart defects, or other causes), the heart rhythm may become abnormally slow, accompanied by a decrease in blood pressure.
Heart block is a delay in the transmission of the heart’s electrical impulses as they travels through the AV (atrioventricular) node, which relays the signals from the atria to the ventricles. There are three degrees of heart block. In first-degree heart block, impulses reach the ventricles but are slightly delayed more than normal as they travel through the AV node. This arrhythmia is common in young adults, athletes, and in those with a highly active vagus nerve (the tenth cranial nerve). First-degree heart block also occurs in people with rheumatic fever, sarcoidosis, and other structural heart problems, and in those taking certain medications, notably beta-blockers. This form of heart block does not cause symptoms. In second-degree heart block, some of the heart electrical impulses do not reach the ventricles. As a result, the heart beats slowly, irregularly, or both. Second-degree heart block sometimes progresses to third-degree heart block. In third-degree, or complete, heart block, electrical impulses do not pass from the atria to the ventricles. This causes the heartbeat to slow. Secondary pacemaker cells in the ventricles take over, signaling the lower chambers of the heart to contract, but at a slower rate than normal. Third-degree heart block is usually caused by heart disease or medications. It may also be present at birth (congenital heart block).
Bundle branch block
The heart’s electrical impulses travel from the atria to the ventricles through the AV (atrioventricular) node. After the impulses go through the AV node, they travel along a track of fibers called the bundle of His, which divides into two parts, a right and left bundle, which connect, respectively, to the right and left ventricles. Normally, impulses travel down both bundles at the same speed, triggering the ventricles to contract simultaneously. Sometimes, a block occurs in one of the branches, forcing the impulses to take a detour, slowing them down. As a result, one part of the ventricle contracts later than the other. Bundle branch block impairs the heart's ability to pump blood, making it work less efficiently. The condition itself often causes no symptoms and requires no direct treatment. However, it may be a sign of an underlying heart problem.
The common cause of arrhythmia is heart disease, especially coronary artery disease, heart valve disorders, and heart failure. Arrhythmias can also stem from injury due to a heart attack or from the healing process after heart surgery. Many medications, prescription as well as over-the-counter, can lead to arrhythmias. In addition, stress, caffeine, tobacco, alcohol, diet pills, and electrolyte imbalances can cause heart rhythm abnormalities. Other causes include congenital heart defects, age-related changes in the heart's electrical system, hyperthyroidism (an overactive thyroid gland), and hypothyroidism (an underactive thyroid gland). In some cases, the cause of an arrhythmia cannot be identified.
Symptoms can range from mild to severe, depending on the arrhythmia and your overall health. Some patients experience no symptoms at all.
Common symptoms of arrhythmia include:
- palpitations (a feeling of skipped or fluttering heartbeats)
- irregular or rapid pulse or heartbeat
- pounding in the chest
- pain or pressure in the chest
- dizziness, light-headedness, or fainting
- shortness of breath
- weakness or fatigue severity of symptoms is not necessarily indicative of the seriousness of an abnormal heart rhythm. An arrhythmia may be harmless and cause severe symptoms, while an arrhythmia may be life-threatening but not cause any symptoms. Often, the arrhythmia is less important than the nature and severity of the underlying heart disease.
In addition to a physical exam and blood tests, the following tests may be used to diagnose an arrhythmia:
- Chest x-ray
- Electrocardiogram (ECG or EKG) — a test used to evaluate the rhythm and electrical activity of the heart
- Holter monitor — a wearable heart monitor that records the heart rhythm for 24 hours
- Transesophageal echocardiograph (TEE): a special echocardiogram that uses high-frequency sound waves to visualize the heart.
- Cardiac catheterization — an X-ray exam of the heart and its arteries, which is used to assess the location and extent of arterial blockage or narrowing.
- 64-slice cardiac CT angiography — a noninvasive test that uses X-rays to build highly detailed three-dimension pictures of cardiac anatomy, including coronary arteries, great arteries and veins, cardiac chambers, muscle, and valves. This test can help rule out structural problems of the heart that may contribute to arrhythmias.
- Electrophysiological study — a test in which a series of electrodes is threaded into arteries in the groin or neck until they reach the heart, allowing doctors to identify the exact source of an abnormal rhythm.
- Tilt-table testing — a test that evaluates how your body regulates blood pressure in response to simple stresses. In this test, the patient lies flat on a table, which is then tilted at different angles.
A variety of therapies are used to restore normal heart rhythms, including medications, pacemakers, defibrillators, biventricular pacing devices, radiofrequency ablation, and surgery. The choice of therapy depends on the type of arrhythmia, the seriousness of the arrhythmia, and the patient’s overall health. Many kinds of arrhythmias do not require treatment. In some cases, serious arrhythmias can be controlled by treating the underlying heart disease.
Types of treatment
Several kinds of drugs are useful in altering the heart’s electrical activity and correcting abnormal rhythms. These include sodium-channel blockers, beta-blockers, potassium-channel blockers, calcium-channel blockers, digoxin, quinidine, procainamide. and adenosine. Finding the right drugs and dosages is not simple and can take some time. In addition, these medications can have significant side-effects and can lead to new arrhythmias. In many cases, additional therapies, including devices or surgery, are needed.
A pacemaker is a small, battery-operated device that sends electrical signals to the heart to help it maintain a regular rhythm. Pacemakers are used to treat bradycardia (abnormally slow heart rate), sick sinus syndrome (tachy-bradycardia), and atrial fibrillation. The device is typically implanted under the skin, below the right or left collarbone, and connected to the heart with one or more wires, or leads. NYU offers patients the option of having the pacemaker inserted using a minimally invasive transaxillary approach (through the armpit). This allows the device to be hidden under the chest muscle, achieving a more desirable cosmetic effect.
External defibrillators (EDs) and Automatic External defibrillators (AEDs):
In emergency situations, such as when a patient experiences ventricular fibrillation and ventricular tachycardia, EDs are used to deliver an electrical shock to the outside of the chest wall, restoring the heart to its normal rhythm. After emergency defibrillation, additional therapy is given to prevent the arrhythmia from recurring. EDs are carried in ambulances, while AEDs are found on airplanes and in many public places. Automated implantable cardioverter defibrillators (AICDs/ICDs). An ICD is a small battery-powered device that is implanted in patients who are at risk of sudden cardiac death due to ventricular tachycardia or fibrillation. The device constantly monitors the heart’s rate and rhythm. When a life-threatening arrhythmia is detected, the ICD delivers an electrical shock, resetting the heart’s pacing. Newer devices can be used to correct both atrial and ventricular arrhythmias or perform biventricular pacing in patients with bradycardia or congestive heart failure. ICDS are implanted in the same way as artificial pacemakers (see above). NYU offers patients the option of having the ICD inserted using a minimally invasive transaxillary approach (through the armpit). This allows the device to be hidden under the chest muscle, achieving a more desirable cosmetic effect.
Radiofrequency ablation is a catheter-based procedure in which radiofrequency energy is used to destroy (ablate) abnormal electrical pathways. Ablation is used to treat atrial fibrillation, atrial flutter, ventricular tachycardia, and paroxysmal supraventricular tachycardia. More information.
The most common arrhythmia surgery is the Maze procedure. It is typically reserved for patients whose atrial fibrillation has not been corrected with medication, for patients at high risk for blood clots or stroke, for patients already undergoing surgery to resolve other heart conditions, and for those whose symptoms significant affect their quality of life. In this operation, a “maze” of incisions is made in the atria, confining electrical impulses to defined pathways. Maze surgery is complicated, yet in the right hands it is highly successful. Some patients require a pacemaker after a Maze procedure. Left atrial appendage ligation. This minimally invasive procedure is typically reserved for patients whose atrial fibrillation has not been corrected with medication and for patients at high risk for blood clots or stroke, such as those who cannot take blood thinners. In this operation, a small incision is made in the left chest and the left atrial appendage is closed off so blood cannot stagnate inside of it and become clotted.
NYU Langone Medical Center
530 First Avenue, Suite 9V
New York, NY 10016
Cardiac Electrophysiology/Heart Rhythm Center
Larry A. Chinitz, M.D.
Neil E. Bernstein, M.D.
Douglas S. Holmes, M.D.
Anthony Aizer, M.D.
Scott Bernstein, M.D.
Sabrina Wilbur, M.D.