Arrhythmias (Heart Rhythm Disorders)

(Also known as: heart rhythm disorders, irregular heartbeat)

An arrhythmia is a disorder that affects the heart rate. The heart tends to beat too slow (bradycardia), too fast (tachycardia), or irregularly. Arrhythmias can affect the amount of blood pumped by the heart.

The beating of the heart is controlled by electrical impulses that normally travel on a smooth path through the heart, causing the ventricles and atria of the heart to contract in a specific order, pushing blood through the lungs and body. These electrical impulses are controlled by the heart's sinoatrial (SA) node, or sinus node, the heart's natural pacemaker.

Although many arrhythmias will never cause health problems, they can cause troublesome symptoms, such as dizziness or chest discomfort. Other, more dangerous arrhythmias can impact blood supply and require medical management. Left untreated, they can eventually lead to stroke, heart attack, heart failure, or sudden death.

Ventricular fibrillation is the most dangerous type of arrhythmia. With this condition, the heart's ventricles lose the ability to contract, stopping blood flow to the body and brain. Ventricular fibrillation rapidly leads to loss of consciousness and death, and requires electrical shock (defibrillation) to restart the heartbeat.

Causes

Damage from many heart diseases and disorders can cause arrhythmias. These include:

• Coronary artery disease
• Past heart attack
• High blood pressure
• Valve disease
• Some forms of congenital heart disease or cardiomyopathy

Often, in patients with an arrhythmia, the heart is normal. Other diseases or substances that can cause arrhythmias include:

• Inherited (genetic) disorders such as Long QT Syndrome
• Diabetes
• Endocrine disorders, such as problems with the thyroid gland
• Excess alcohol and some street drugs
• Excess caffeine
• Smoking
• Some prescription medications or dietary supplements
• Stress

Symptoms

Symptoms of arrhythmias can include:

• Heart palpitations (a racing or irregular heartbeat)
• Lightheadedness or dizziness
• Fainting or almost fainting
• Shortness of breath
• Chest pain or discomfort

Many of these symptoms can be confused with the effects of aging or physical inactivity, or with other diseases affecting the heart.

Diagnosis

Tests commonly used to diagnose arrhythmias include:

• Electrocardiogram: to identify problems with heart rhythm
• Holter monitor: a portable electrocardiogram machine used to continuously monitor the heartbeat over one or two days
• Event monitor: similar to a Holter monitor, but used for weeks or months. An event recorder is turned on by the patient when symptoms occur
• Electrophysiology studies: to track and stimulate electrical impulses in the heart
• Stress (exercise) testing: to test whether an arrhythmia occurs when the heart is challenged to work harder than normal

Treatment/Management

A variety of approaches can be taken in treating and managing arrhythmias. Some arrhythmias need only to be monitored, while others require urgent treatment.

Drug Therapies: Many drugs are available for reducing the occurrence of arrhythmias or managing symptoms. These include drugs to:

• Slow the heartbeat (beta blockers and calcium channel blockers)
• Keep the heart rhythm normal (antiarrhythmic drugs)
• Help prevent blood clots (blood thinners, such as warfarin)

Implantable Devices: Some people with arrhythmias may need an implantable device to help the heart work properly.

• A pacemaker is a small device implanted near the heart. It is usually used to treat bradycardia. The pacemaker monitors the electrical activity of the heart and delivers a small electrical pulse when the heart beats too slowly.
• An implantable cardioverter-defibrillator (ICD) is similar to a pacemaker but can deliver an electrical shock to restore normal heart rhythms when needed. An ICD may be necessary for patients with more dangerous arrhythmias that can stop the heartbeat, such as ventricular fibrillation.

Ablation: Some arrhythmias may need to be treated with a minimally invasive technique called radio-frequency ablation. This procedure is performed using a catheter threaded through a blood vessel to the heart. An electrode is inserted through the catheter and used to heat and destroy a small area of tissue. This can block abnormal electrical signalling pathways in the heart.

Lifestyle Changes: Lifestyle changes can help reduce the symptoms of heart disease underlying arrhythmias as well as target arrhythmias directly. Some changes recommended for people with arrhythmias include:

• Quitting smoking
• Limiting alcohol, caffeine, and over-the-counter medications that contain stimulants
• Increasing physical activity (with a doctor's supervision)
• Reducing stress
• Losing weight if overweight and maintaining a healthy weight

Although important to make, such lifestyle changes may have little effect on arrhythmias.