Cardiac Arrhythmias

Basic Facts

  • An arrhythmia is an abnormality or disturbance in the rate or rhythm of the heartbeat.
  • Arrhythmias are caused by problems with the heart’s electrical system that alter the formation of the electrical impulse that initiates a heartbeat or disrupt the pattern of conduction that distributes the impulse through the heart.
  • Arrhythmias may range from minor events to those that may cause loss of consciousness or, occasionally, death.
  • An atrial arrhythmia is an abnormality that occurs in one of the two upper chambers of the heart, the left or right atrium.
Atrial Fibrillation

Atrial Fibrillation - In atrial fibrillation, the atrium (the upper chambers of the heart) are in a state of electrical chaos, causing them to quiver — sometimes more than 600 times per minute — without contracting. The ventricles (the lower chambers of the heart) do not receive regular impulses and contract out of rhythm, and the heartbeat becomes uncontrolled and irregular. It is the most common atrial arrhythmia, and 85 percent of people who experience it are older than 65 years.

Atrial fibrillation can cause a blood clot to form, which can enter the bloodstream and result in a stroke. Underlying heart disease or hypertension increases the risk of stroke from atrial fibrillation, as does age. 

Premature Atrial Contraction (PAC or premature atrial impulses) - A common and benign arrhythmia, a PAC is a heartbeat that originates away from the sinus node, which sends electrical signals through the upper chamber. It typically occurs after the sinus node has initiated one heartbeat and before the next regular sinus discharge. A PAC can cause a feeling of a skipped heartbeat. Use of caffeine, tobacco, and/or alcohol, or stress can bring on PACs or increase their frequency.

Supraventricular Tachycardia (SVT) - Characterized by a rapid heart rate that ranges between 100 and 240 beats per minute, SVT usually begins and ends suddenly. SVT occurs when an electrical impulse “re-enters” the atrial muscles. A disorder that a person may have at birth, SVT is commonly caused by a variation in the electrical system of the heart. SVT often begins in childhood or adolescence and can be triggered by exercise, alcohol, or caffeine. SVT is rarely dangerous, but can cause a drop in blood pressure, causing lightheadedness or near-fainting episodes, and, rarely, fainting episodes.

Atrial flutter - Differentiated from atrial fibrillation by its coordinated, regular pattern, atrial flutter is a coordinated rapid beating of the atria. Most who experience atrial flutter are 60 years and older and have some heart disorder, such as heart valve problems or a thickening of the heart muscle. As with atrial fibrillation, atrial flutter increases the risk of stroke.

Sick Sinus Syndrome (SSS) - Common among older people, SSS is an improper firing of electrical impulses caused by disease or scarring in the sinus node, which sends electrical signals through the upper chamber. SSS normally causes the heart rate to slow, but sometimes it alternates between abnormally slow and fast. SSS is a progressive condition, with episodes increasing in frequency and duration

Sinus Tachycardia – With Sinus Tachycardia, the sinus node emits abnormally fast electrical signals, which increases the heart rate to between 100 beats per minute to 140 beats per minute at rest, and 200 beats per minute during exercise. 

Sinus Bradycardia - Associated with impaired impulse generation in the sinus node, sinus bradycardia causes the heart rate to decrease to fewer than 60 beats per minute. 

Wolff-Parkinson-White syndrome (WPW) - In WPW syndrome, an extra electrical pathway between the heart’s upper and lower chambers causes a rapid heartbeat

The onset and duration of arrhythmia symptoms vary according to its type, frequency, duration, and whether structural heart disease is present. 

An arrhythmia may require medical treatment when it occurs repeatedly over an extended period or cause symptoms such as:

  • Palpitations,
  • Lightheadedness,
  • Shortness of breath, 
  • Fatigue, 
  • Chest pain and/or
  • Cardiac arrest.

Certain arrhythmias may cause fainting (Syncope), and, occasionally stroke, while others (‘silent’ arrhythmias) cause no symptoms.

 

 

People with a preexisting heart condition or other conditions such as diabetes or high blood pressure are at risk for developing an arrhythmia. Age, gender and lifestyle factors can also play a role. 

 

Arrhythmias can be difficult to diagnose because they can be unpredictable and brief. A physician will typically take a person’s medical history, and perform a physical examination, during which the physician may detect an arrhythmia using a stethoscope. Arrhythmias that occur infrequently, last for short periods of time, or do not cause noticeable symptoms may require more detailed tests, such as:

  • Electrocardiogram (ECG) – This noninvasive test records the electrical activity of the heart.
  • Holter Monitor (an ambulatory ECG) – This device records the heart’s activity for 24 hours or longer.
  • Event Recorder – This portable ECG can be activated when a patient experiences symptoms of a fast heart rate. It is intended to monitor heart activity over a few weeks or months.
  • Implantable Loop Recorder – This implanted recorder can be used to diagnose patients with recurring and unexplained arrhythmia episodes.

In some cases, arrhythmias may not require treatment. Other arrhythmias can be controlled by treating the underlying cause. Arrhythmias that cause symptoms may require one or more of the following treatments to reduce the number or duration of arrhythmic events.

Common antiarrhythmic medications for suppressing arrhythmias include:

  • Beta-blockers, 
  • Calcium channel blockers,
  • Digitalis, and
  • Antiarrhythmic agents, which affect the heart’s electrical activity.

People with atrial fibrillation are typically prescribed an anticoagulant to minimize their risk of clotting and stroke. 

Cardioversion - This procedure restores a normal heartbeat by transmitting a brief electric shock through the chest to the heart. This resets the rhythm to normal, but does not fix any underlying problem that predisposes a patient to an arrhythmia. 

Usually an outpatient procedure that is performed in a hospital while the patient is under heavy sedation or anesthesia, cardioversion is commonly used to treat:

  • Atrial fibrillation,
  • Atrial flutter, and
  • Ventricular arrhythmias.

Radiofrequency Catheter Ablation – For this minimally invasive treatment, a catheter with an electrode tip is positioned on the affected area. The catheter delivers energy to strategically destroy tissue that is interfering with the normal transmission of electrical impulses through the heart. It is most commonly used for:

  • SVT,
  • Atrial flutter, and
  • Certain types of ventricular arrhythmias.

Pacemaker – This small electronic device is surgically implanted under the skin near the collarbone. The pacemaker regulates a slow or erratic heartbeat by sending rhythmic electrical charges to the right atrium and right ventricle. 

Maze Procedure – For this treatment, a physician makes multiple incisions through the atrium. The resulting scar tissue conducts impulses through the heart’s electrical system in a way that allows normal conduction but does not sustain atrial fibrillation. Since it is a form of cardiac surgery, it is reserved for those patients who are highly symptomatic.