Introduction

Heart arrhythmias, also called cardiac arrhythmias, are irregular heart rhythms that result when the heart beats too fast, too slow, or unevenly. A heart arrhythmia occurs if there is a disturbance anywhere along the nerve signal pathway in the heart chambers. There are many different types of heart arrhythmias and some are more serious than others, causing heart attack or sudden death. Heart arrhythmias are treated with medications, electrophysiologic ablations, and surgically placed pacemakers or implantable cardioverter-defibrillators.

Anatomy

The heart is the core of the cardiovascular system. Your cardiovascular system consists of your heart and the blood vessels that carry blood throughout your body. Your heart is located to the left of the middle of your chest. It is a large muscle about the size of your fist. It works as a pump. The blood carries nutrients and oxygen that your cells need for energy. It also carries waste products away.

Your heart is divided into four sections called chambers. The chambers are separated by the septum, a thick wall. The two top chambers are called atria, and they receive blood coming into the heart. The two bottom chambers are called ventricles and they send blood out from the heart.

Your heart contains two pumping systems — one on its left side and one on its right side. The left-sided pumping system consists of the left atrium and the left ventricle. Your left atrium receives blood that contains oxygen, which comes from your lungs. Whenever you inhale, your lungs move oxygen into your blood. The oxygenated blood moves from the left atrium to the left ventricle. The left ventricle sends the oxygenated blood out from your heart to circulate throughout your body.

The heart’s right-sided pumping system consists of the right atrium and the right ventricle. Your right atrium receives deoxygenated blood, blood that has circulated throughout your body and no longer has high levels of oxygen in it. The deoxygenated blood moves from the right atrium to the right ventricle. The right ventricle sends the blood to the lungs where it receives oxygen when you breathe.

As the blood travels through the heart chambers, four valves keep the blood from back flowing. The mitral valve and the tricuspid valve regulate blood flow from the atria to the ventricles. The aortic valve and the pulmonary valve control blood as it leaves the ventricles.

The four chambers of the heart contract in a very exact and coordinated manner. The contractions are controlled by electrical impulses from the sinus (SA) node, your heart’s natural pacemaker. The signals travel on a specific path, first from the SA node through the atrium and then through the atrio-ventricular (AV) node and through the ventricles.

Your doctor will listen to your heart with a stethoscope. A healthy heart has a regular rhythm and makes a lub-dub sound each time it beats. The first sound in your heartbeat occurs when the mitral valve and the tricuspid valve close. The second sound in your heartbeat occurs when the aortic valve and the pulmonary valve close after the blood leaves your heart.

Causes

A heart arrhythmia occurs if there is a disturbance anywhere along the nerve signal pathway throughout the heart. There are different types of heart arrhythmias depending on where the interruption in the conduction system occurs. Heart arrhythmias may result from heart conditions, heart attack, blood chemistry imbalances, and endocrine abnormalities. Medications, caffeine, and illegal drugs, such as cocaine or amphetamines, can cause irregular heart rhythms. Untreated heart arrhythmias can be life threatening.

Some of the specific types of heart arrhythmias are described below:

• Bradycardia is a slow heart rate that generally results because of problems with the heart’s internal pacemaker, the SA node.
• Tachycardia is a fast heart rate that may involve the atria or the ventricles.
• Supraventricular tachycardia (SVT) is a fast heart rate that originates in the atria.
• Ventricular tachycardia is a fast heart rate that originates in the ventricles.
• Atrial fibrillation is an uneven and very fast heart rate. The atria may pump five to seven times faster than normal, causing the heart to pump blood improperly.
• Atrial flutter is a very fast and steady heartbeat caused by abnormal nerve firing.
• Premature atrial contraction (PAC) is an irregular heartbeat with extra beats or premature beats from problems in the atria.
• Sick sinus syndrome is an irregular heartbeat caused when the SA node does not work properly and the heart rate slows down.
• Premature ventricular contraction (PVC) is an irregular heartbeat with extra beats or premature beats from problems in the ventricles.
• Ventricular fibrillation is a rapid irregular heartbeat. Little or no blood may be pumped from the heart. It requires immediate medical attention and can result in sudden death.

Symptoms

Heart arrhythmias may or may not produce symptoms. Heart arrhythmias can cause heart palpitations—you may feel your heart beating in your chest. Your heart may feel like it is beating fast, slow, or irregularly. It may feel like your heart skips a beat. You may feel faint, lightheaded, or dizzy. You may experience chest pain or shortness of breath. Your skin may become pale and sweaty. In severe cases, a heart attack may occur.

An ambulance should be called immediately if a heart attack is suspected. Symptoms of a heart attack include pain or pressure in the center of the chest, shortness of breath, nausea, vomiting, and pain that radiates from the chest into the teeth, jaws, shoulders, or arms. A heart attack can be fatal. Immediate emergency medical care is necessary.

Diagnosis

Your doctor can begin to diagnose heart arrhythmia by reviewing your medical history and conducting a physical examination and some tests. Your doctor will use a stethoscope to listen to your heart. There are several tests that can be used to diagnose heart arrhythmia.

The tests may include a chest X-ray, electrocardiogram (ECG), and echocardiogram. An ECG records the heart’s electrical activity. An echocardiogram uses sound waves to produce images of the heart on a monitor. An exercise stress test involves monitoring your ECG and blood pressure while you exercise on a treadmill. The exercise stress test provides information about how your heart works with an increased blood flow. You may wear a Holter monitor for periods of 24 hours or more. A loop recorder can also be used to detect rhythm abnormalities over a long period of time. If your arrhythmia is infrequent, you may wear an event recorder that you activate when you feel symptoms. An event recorder may also be surgically placed under the skin for long periods of time. An electrophysiologic (EP) study is an advanced procedure which can diagnose and even treat some arrhythmias.

Tilt table testing is used to check for sudden drops in blood pressure or heart rate that can cause fainting. For this procedure, you are secured to a table, which will be positioned at different inclines for various periods of time. Your blood pressure and ECG will be recorded.

Treatment

The treatment that you receive depends on the type, location, severity, and cause of your arrhythmia. Emergency treatment for arrhythmia includes electrical shock therapy (defibrillation or cardioversion) or intravenous (IV) medications. A pacemaker may be surgically implanted to maintain a regular heartbeat. Ablation is an advanced procedure, which can treat some arrhythmias. Some people may require lifelong medication. An implantable defibrillator may be surgically placed to treat ventricular tachycardia.

Prevention

You may prevent heart disease and decrease your risk of developing arrhythmias by taking steps to keep your heart healthy. It is important not to smoke, use illegal drugs, or abuse alcohol. You should eat a heart healthy diet and exercise regularly. Make and attend all of your doctor appointments and receive regular physicals.

Am I at Risk

People with heart conditions, a history of heart attack, blood chemistry imbalances, or endocrine abnormalities are at risk for heart arrhythmias. Using certain medications, caffeine, or illegal drugs can increase your risk for heart arrhythmias.

Complications

Some arrhythmias can be dangerous and potentially fatal. Some arrhythmias can lead to stroke, heart attack, heart failure, and sudden death. You should contact your doctor if you experience symptoms of arrhythmia. Early treatment is associated with better outcomes. You should call for an ambulance if you suspect that you or someone else is experiencing a heart attack or stroke.