An abnormal heart rhythm is called an arrhythmia, which means that the heart beats too slowly, too rapidly, or in an irregular pattern. There are many types of arrhythmias, which are identified according to where they occur in the heart (atria or ventricles) and by what happen to the heart”s rhythm when they occur. Arrhythmias arising in the atria are described as atrial or supraventricular (above the ventricles). Arrhythmias originating in the ventricles are generally the most serious type of abnormal heart rhythm.
Arrhythmias are classified based on the presence or absence of heart disease. In the absence of structural heart disease, all arrhythmias are generally benign (not life threatening) and do not have an impact on longevity. Arrhythmias can indicate the presence of heart disease also symptoms from arrhythmia can be disabling and affect the quality of one”s life.
Individuals experience the symptoms of arrhythmia differently. Some who have this condition may not feel any symptoms, and their arrhythmia will go unnoticed until it is detected by a physician during a routine examination. Others may experience only minor symptoms, while some are sensitive to the slightest sensation. Symptoms commonly reported include:
The heart’s electrical system generates impulses that are felt as heartbeats. Every cell in the heart muscle is capable of initiating an electrical impulse; therefore, it is normal to have occasional premature beats that can occur under normal conditions. If you have rapid or irregular heartbeats, this can cause a sensation called palpitation. Patients describe palpitations as fullness in the throat or neck or as feeling a more forceful beat. They are usually felt at times when the mind and body are relaxed, so patients often experience palpitations in the evening when reading, watching television, or getting into bed. Feeling palpitations sometimes causes anxiety that can produce increased adrenaline levels, which, in turn, can increase the frequency of the premature beats and make the palpitations worse. Although palpitations can be a benign condition, they should always be evaluated by a cardiologist/electrophysiologist to rule out any underlying problems.
Some arrhythmias may cause syncope (fainting), lightheadedness, or dizziness. This is caused by the heart either beating too slow or too fast, leading to an insufficient flow of blood to the brain. Syncope can be episodic and difficult to diagnose. A tilt table test may be recommended to determine if the cause of fainting spells is due to neurocardiogenic syncope. Arizona Heart Rhythm consultants also offer a 24-hour monitor (Holter), a 10-30 day event monitor and also implantable diagnostic device that provides a method for the diagnosis of syncope or lightheadedness. These monitoring devices may provide answers that can lead to effective treatment.
Arrhythmias Originating in the Upper Chambers
ARRHYTHMIAS ORIGINATING IN THE LOWER CHAMBERS
When the heart rate is too slow, (usually less than 60 beats per minute), not enough oxygen is pumped to the body. The lack of oxygen causes symptoms such as dizziness, extreme tiredness, shortness of breath, or fainting. Bradycardia is when a heart rate is too slow and symptoms occur.
The heart can beat too slowly for several reasons.
SICK SINUS SYNDROME
Sick Sinus Syndrome is a failure of the heart’s natural pacemaker, the sinus node, which controls the rhythmic contractions of the heart. As a result, the heart beats slow and irregular. Sometimes the rate changes back and forth between a slow rate (bradycardia) and a fast rate (tachycardia), also called as “Tachy-Brady Syndrome”. Symptoms are palpitations, lightheadedness and shortness of breath. Treatment: In most cases when the heart rate is too slow or too high, a pacemaker is recommended to control the heart rate.
Heart block occurs when there is a partial or complete block of the heart’s electrical pathways between the atrium and the ventricles, resulting in a slow, unreliable heart rhythm. Symptoms are lightheadedness, syncope, shortness of breath. Treatment: Implantation of a pacemaker is often recommended to prevent a slow heart rate that would cause symptoms.
Atrial fibrillation is a rapid chaotic rhythm that originates from multiple sites within both atrial chambers. Small circuits simultaneously exist throughout the atrial chambers in a dynamic changing pattern. These circuits give rise to rapid impulses that bombard the connection between the top and bottom chambers of the heart, the AV node. Only some of these impulses can get through this structure which serves as a natural bottleneck against too rapid stimulation of the bottom chambers, the ventricles. Nonetheless, the ventricles will be stimulated in a more rapid fashion than normal and the pattern will be irregular, also differing from the normal. This rapid, irregular pattern gives rise to the symptoms of atrial fibrillation, such as palpitations, rapid heart-beat , chest discomfort, shortness of breath and dizziness. Contributing to the symptoms is the failure of the atria and the ventricles to have coordinated pumping action as they do in the normal situation, which can also lead to a less efficient cardiac pump. In some individuals, failure of the atrial chambers to contract properly can make them more prone to the formation of clot which can travel to distant organs where they may cause damage. Treatment: Antiarrhythmic drugs are sometimes sufficient treatment for atrial fibrillation. Ablation of atrial fibrillation is curative in 70-80% of cases. In certain cases, an implanted pacemaker (in conjunction with ablation of AV node) is used to control the heart rate.
Atrial flutter also involves rapid firing of the electrical impulse as in atrial fibrillation, but the rhythm or heart-beat is more regular or organized. The rhythm is due to a circuit (reentry) within the atria. The electrical impulse travels in circles arriving back at the same point, usually around 300 times per minute. Signs and symptoms often experienced with atrial flutter are similar to those of atrial fibrillation, such as a pounding heart rate or pulse, shortness of breath, or dizziness. Treatment: Antiarrhythmic drugs are only sometimes successful in treating atrial flutter. However, cardiac ablation can cure atrial flutter in greater than 90 percent of cases.
ATRIAL PREMATURE CONTRACTIONS (APC)
A heart rhythm disorder that involves a premature firing of the atrium that, in some cases, can cause the sensation of an irregular heartbeat. Symptoms are Palpitations, fluttering. Treatment: APC is generally a benign condition; however, some patients may experience symptoms that require medical therapy. When frequent and symptomatic they may require catheter ablation
Atrial tachycardia is an electrical circuit originating in the upper or atrial chambers. This electrical circuit or focus takes over and generates rapid impulses across the atrial chambers. These impulses are transmitted to the ventricular chambers resulting in a rapid rate. These arrhythmias may originate from a variety of places across the atria. They may exist as an isolated problem or be related to an ongoing structural problem within the heart. Treatment: Antiarrhythmic drugs are sometimes sufficient treatment for atrial tachycardia. In some cases, cardiac ablation is needed to cure this condition.
ATRIOVENTRICULAR RECIPROCATING TACHYCARDIA (AVRT)
Many patients with this condition are otherwise healthy and often quite young when this arrhythmia is diagnosed. This type of arrhythmia involves an extra electrical pathway from the atria to the ventricles known as the “accessory pathway,” electrical impulses may be transmitted rapidly via this allowing a circuit to form leading to a rapid arrhythmia. Atrioventricular reciprocating tachycardia is similar to Wolff-Parkinson-White (WPW) Syndrome in that the abnormal electrical pathway bypasses the AV node. The difference, however, between WPW and this condition is that the abnormalities do not show up on a patient”s resting EKG. The most common symptoms people experience are palpitations, dizziness, and chest discomfort. Treatment: Certain forms of drug therapy can be effective; however, in most cases, cardiac ablation is recommended to cure this condition.
AV NODAL REENTRANT TACHYCARDIA (AVNRT)
AV nodal reentrant tachycardia is the most common form of paroxysmal supraventricular tachycardia or PSVT. Patients afflicted with this arrhythmia do not usually have other structural problems with their heart. The arrhythmia originates in the tissues near the AV node, the electrical structure that transmits impulses between the upper and lower chambers of the heart. Susceptible individuals will have two pathways that can channel impulses to and from the AV node. Under the right conditions, usually following a premature beat, these pathways can form an electrical circuit. An impulse will revolve around this circuit and each revolution will lead to impulse propagation to the atria and the ventricles, and thus a rapid heart-beat results. Treatment: Certain forms of drug therapy can be effective; however, in most cases, cardiac ablation is recommended to cure this condition.
INAPPROPRIATE SINUS TACHYCARDIA
This condition originates in the sinus node and is characterized by an abnormally fast heart rate greater than 100 beats per minute for prolonged periods of time. Symptoms are palpitations, fatigue, and lightheadedness. Treatment: Antiarrhythmic drugs usually offer successful treatment for sinus tachycardia. In rare cases, cardiac ablation is needed to control this condition.
WOLFF-PARKINSON-WHITE SYNDROME (WPW)
Many patients with WPW syndrome are otherwise healthy and often quite young when this arrhythmia is diagnosed. This type of arrhythmia involves an extra electrical pathway from the atria to the ventricles. Known as the “accessory pathway,” electrical impulses may be transmitted rapidly via this pathway and the rapid rhythm sometimes can be dangerous. Other times, the pathway allows a circuit to form leading to a rapid arrhythmia. The most common symptoms people experience with WPW syndrome are palpitations, dizziness, and chest discomfort. Some people with WPW do not have arrhythmias. Treatment: Certain forms of drug therapy can be effective; however, in most symptomatic cases, cardiac ablation is recommended to cure this condition.
Ventricular fibrillation is a fatal arrhythmia characterized by rapid, disorderly contraction of the ventricles. If immediate defibrillation is not administered when this occurs, blood pressure cannot be maintained and death will occur. Symptom is usually Syncope. Treatment: Cardiac defibrillation. Survivors will need implantation of cardiac defibrillator.
VENTRICULAR PREMATURE COMPLEXES (VPC)
An extra beat originating from the ventricles is called a VPC. In patients with normal hearts, this is a benign condition. However, in patients with an underlying heart disorder, this can indicate a life-threatening problem. Patients are often symptomatic with palpitations or skipped beats. Treatment: In patients with normal hearts, asymptomatic VPCs generally do not require treatment; however, some patients may experience symptoms that require medical therapy. Cardiac ablation is successful in curing this condition when these extra beats arise in the right side of the heart. If significant heart dysfunction is suspected, then an electrophysiology study is recommended to determine whether a life threatening abnormal heart rhythm is present, which may require placement of cardiac defibrillator.
Ventricular tachycardia is an arrhythmia that originates in the pumping chambers, or the ventricles. It is usually seen in patients who have damaged ventricular chambers, frequently in the aftermath of a heart attack or myocardial infarction. Scar tissue in the ventricles will alter many local electrical properties and set up conditions favorable to formation of a local electrical circuit. Under specific circumstances, the circuit can be activated leading to a rapid arrhythmia arising from within the pumping chambers. As this is always more rapid than the heart”s natural electrical activity, it takes over the heart-beat for the duration of the arrhythmia. Due to the fact that this rhythm is usually very fast and occurring in damaged chambers, the heart may not function properly or efficiently and low blood pressure of fainting may result. In its most extreme form, ventricular tachycardia can lead to fatal consequences. This is a potentially dangerous arrhythmia that almost always requires therapy. In some patients, ventricular tachycardia may occur when there is no structural heart disease. This “idiopathic” form often arises from the right ventricle and less often from the left ventricle. These arrhythmias are less dangerous, but also often require therapy. Treatment: In symptomatic patients with normal hearts, VT can be cured with cardiac ablation. In those with a history of heart disease, an ICD, possibly combined with medical therapy, is required to control the condition. Patients with recurrent episodes who are not controlled with medications need cardiac ablation.
MEDICAL TREATMENT WITH ANTIARRHYTHMIC DRUGS:
The initial treatment for atrial rhythm disorders may be antiarrhythmic drug therapy. These drugs can slow the conduction of rapid heart rhythms and/or convert them to a normal sinus rhythm. Other drugs help the heart maintain regular rhythm. Drugs, however, do not cure heart rhythm disorders (only suppress them), and they are not effective in all patients. They also require that a patient maintain a very strict schedule of follow-up care with his or her physician. Blood tests are needed for those on long-term therapy to monitor the functioning of other organ system which may be affected by the drugs.
Some heart rhythms predispose patient to formation of blood clots in the heart. Blood thinning medications (anticoagulation) are sometimes used in conjunction with other treatments to decrease the stroke risk in some patients.
Catheter ablation is a non-surgical technique that sometimes offers a cure for patients with heart rhythm abnormalities. This procedure is an option for those patients who are not controlled by medical therapy. (For more information about this procedure, see Catheter Ablation)
Pacemakers are implanted to treat slow heart rhythms and heart block. These devices may also be used to allow medical therapy which may otherwise slow the heart rhythm. Defibrillators are implanted for treatment of fast life threatening rhythms originating in the lower chambers. They are also used for prevention of sudden cardiac death in patients at high risk of developing these fast life threatening rhythm (those with weak heart muscle).
Biventricular pacing is used in patients with weak heart muscle along with abnormal electrical signaling in the lower pumping chamber. They work by resynchronizing the contraction of different walls of the heart muscle thereby making the lower pumping chamber more efficient.