Arrhythmias are disorders that produce abnormal heart rhythms when there is a change from the normal sequence of electrical impulses. This can cause the heart to pump less effectively. Some arrhythmias are so brief that the overall heart rate or rhythm is not greatly affected. Other arrhythmias, more extensive or volatile in nature, can be signals of more serious underlying problems.
An arrhythmia is likely to occur:
- When the heart's natural pacemaker develops an abnormal rate or rhythm.
- When the normal conduction pathway is interrupted.
- When another part of the heart takes over as a pacemaker.
In many cases, the exact cause of an arrhythmia remains a mystery. However, there are a number of factors that can contribute to this type of disorder. They can include:
- coronary artery disease
- high blood pressure
- excessive use of alcohol or caffeine
- drug abuse
Certain over-the-counter substances such as dietary supplements, herbal remedies, and prescription medication can lead to arrhythmias.
If conditions of an arrhythmia linger over a long period of time, they can cause the heart rate to either beat too slowly (bradycardia) or too quickly (tachycardia).
Bradycardia and tachycardia can produce the following symptoms:
- Fainting or near fainting
Slow heartbeats (bradycardia) may be treated when symptoms occur. A pacemaker is sometimes implanted to prevent the heart from beating too slowly. Some fast heartbeats may be treated with medications or with a procedure called an ablation. During an ablation, abnormal heart tissue is located and destroyed using special catheters inserted into the heart through the veins. No surgery is required and ablations are often done as a same-day procedure.
Atrial fibrillation is the most common heart rhythm disturbance, affecting more than 2 million people in the United States. About 160,000 new cases are diagnosed each year. Atrial Fibrillation, also called AFib, is a heart rhythm disorder caused by a problem in the conduction of electrical impulses in the upper chambers, or atria of the heart. AFib causes the heart to beat irregularly and sometimes rapidly. It happens when the heart's electrical system is unable to maintain control of the heart's rhythm. Normally, the heart's rhythm is controlled by a group of cells called the sinoatrial node (SA node). These cells are found in the top chambers of the heart (the atria) and they function as our own natural pacemaker. With atrial fibrillation, the SA node no longer is in control and the top chambers of the heart beat erratically and rapidly. Fortunately our hearts have another group of cells, called the atrioventricular node (or the AV node) which keeps all of these erratic impulses from making it to the main lower chambers of the heart (the ventricles).
Atrial fibrillation is seen in all age groups. The likelihood of developing the condition, however, increases with age. After age 65, 3 to 5 percent of people have atrial fibrillation. Approximately 9 percent of people who are age 80 or older have the condition. Atrial fibrillation is more common in people who already have heart disease (such as a previous heart attack, hypertension or leaky valves) but it can also be seen in people without any signs of heart disease.
Signs and Symptoms
Atrial fibrillation may cause a variety of symptoms. But some people have no idea they have it. The most common symptoms of atrial fibrillation are:
- Shortness of breath
- Difficulty with exertion
- Chest pain
- Dizziness or fainting
Damage, abnormalities, and diseases to the heart's valves or pumping system are the most common causes of atrial fibrillation. These might include:
- Heart attacks
- High blood pressure
- Overactive thyroid
- Congenital heart defects
- Abnormal heart valves
- Exposure to stimulants, caffeine, alcohol, medications
- Sick sinus syndrome - the heart's natural pacemaker stops functioning properly
- Lung diseases
- Viral infections
- Sleep apnea
Even if the symptoms are minimal, atrial fibrillation can cause serious problems, including a stroke. During atrial fibrillation, the top chambers no longer beat effectively. This reduces the flow of blood through these chambers. This, in turn, can allow the blood to form clots inside the heart. These clots may travel out of the heart and lodge in a small artery in the brain, causing a stroke. The risk of stroke in atrial fibrillation increases with age. People with AFib have a 3- to 5-times higher risk of stroke, especially those who are older than 65, have already had a stroke, or have high blood pressure, diabetes or congestive heart failure, according to the Framingham Heart Study. In addition to stroke, atrial fibrillation may cause the heart to weaken over time, especially when it is associated with a rapid heart rate for a prolonged period of time. This, in turn, may cause congestive heart failure or shortness of breath.
What to do?
It is important to know that these complications of atrial fibrillation can be prevented. The Hoffman Heart and Vascular Institute of Connecticut offers a range of successful treatment options for arrhythmias and atrial fibrillation. Learn more...
A rapid heart rate in the ventricles, called ventricular tachycardia, can be life-threatening. However, the most serious cardiac rhythm disturbance is ventricular fibrillation, where the heart can't pump any blood. Collapse and sudden death can follow unless medical help is provided immediately. If treated in time, ventricular tachycardia and ventricular fibrillation can be converted into a normal rhythm with a high voltage electrical shock.
For patients felt to be at high risk for sudden cardiac arrest, surgeons can implant a special device called an implantable cardioverter-defibrillator (ICD). This device monitors a patient's heart beat and delivers an electric shock when it detects a life-threatening heart rhythm such as ventricular fibrillation. The ICD has been proven to help prevent sudden cardiac death in patients with weak hearts, congestive heart failure and in patients who have survived a previous cardiac arrest.
Congestive Heart Failure
Patients with congestive heart failure may be at risk for sudden cardiac arrest. An ICD may be required to prevent this fatal arrhythmia. In patients with congestive heart failure and bundle brach block (a form of electrical conduction disorder that causes the ventricles to beat out of sync with each other), an ICD is combined with a special pacemaker to help a failing heart to pump more efficiently. This is called a biventricular ICD because it paces both the right and the left ventricles to resynchronize them.