Heart rhythm disorders (arrhythmias) occur either independently or as a result of other cardiac conditions, such as coronary artery disease and myocardial infarction (heart attack). In any case, rhythm disorders signal abnormalities in the conduction system of the heart.
Heart rhythm disorders are categorized as either bradycardia (slow heartbeat) or tachycardia (rapid heartbeat). Tachycardia may further sub-divided into ventricular tachycardias (involving only the ventricles) and supraventricular tachycardias (involving both the atria and the ventricles).
- Symptoms of bradycardia(slow heartbeat)
Fatigue
Dizziness
Lightheadedness
Fainting spells
Heart palpitations
- Symptoms of tachycardia(fast heartbeat)
Rapid heart action
Dizziness
Lightheadedness
Fainting spells
Examples of specific arrhythmias include:
Atrial fibrillation:
Rapid and irregular heartbeat due to signals in the atria that cause the ventricles to contract abnormally. This condition prevents blood from flowing through the heart's chambers, often causing it to accumulate in the atria. A blood clot may form as a result of atrial fibrillation, leading to stroke or myocardial infarction (heart attack).
Ventricular fibrillation:
Rapid contractions of the heart caused by irregular electrical signals in the ventricles. The condition is common after myocardial infarction (heart attack) or from electrocution or drowning. The condition is life-threatening and should be treated immediately with electric shock (defibrillation) to the heart followed by anti-arrhythmic drugs.
Premature ventricular contraction:
An abnormal signal from the ventricles causes the heart to beat prematurely (early). Premature ventricular contraction is common in children and teenagers and may not require treatment. However, in some cases when the condition is caused by disease or injury, it could lead to ventricular tachycardia and also fibrillation.
Heart block:
Interruption of electrical communication between the atria and ventricles. This results in the ventricles contracting less often than the atria. The condition leads to episodes of dizziness, fainting spells or stroke. Heart block is categorized by its severity. More severe cases are commonly treated with an artificial pacemaker, or less commonly, with drugs (such as isoproterenol).
Early detection and treatment are key in preventing death or disability from certain heart rhythm disorders. Rhythm disorders may be diagnosed by careful examination of the symptoms (palpitations, fainting spells, lightheadedness, dizziness, rapid heart action, etc.) and several diagnostic tests, including:
Electrocardiogram (ECG or EKG):
An electrocardiogram is a graphical record of the electrical activity of the heart. A normal ECG, in most cases, rules out the presence of other cardiac diseases. An abnormal ECG indicates the presence of a cardiac disease and further investigations are performed. An ECG can be beneficial in detecting the disease and sometimes even the extent of the disease.
Stress test:
A stress test involves taking an ECG before, during and after a treadmill workout to detect cardiac disease and/or damage, including the extent of coronary artery disease. However, false positive results are possible with stress tests.
Echocardiogram (heart ultrasound):
This diagnostic technique is an excellent tool to provide details of the cardiac structures – vessels, valves, and muscle. Echocardiography is a non-invasive exam in which images are acquired and viewed in real time without the use of radiation. Echocardiography is often useful in studying the beating heart and provides some information on functional abnormalities of the heart wall, valves and blood vessels. Echocardiography with Doppler is used to measure blood flow across valves, across septal defects (shunts), extent of regurgitations, etc. Color flow mapping capability is extremely useful in the detection of shunts. Abnormal operation of the valves can be detected by studying the opening and closing function versus normal valve function. Echocardiography may also be used to study congenital heart defects such as a septal defect (a hole in the wall that separates the two chambers of the heart).
Tilt table study:
This study is typically performed to determine the cause of fainting spells. The patient is secured on a special table, an intravenous line is drawn, and the patient is quickly titled upright. Blood pressure, heart rate, and other factors are monitored for abnormal readings.
Electrophysiology (EP) study:
This study involves inserting a catheter in a vein or artery in the groin and guiding it to the heart using angiography for guidance. The heart’s electrical activity is then monitored in multiple places using sophisticated in-vivo EKG leads to help diagnose tachycardias or bradycardias. Electrophysiology studies are also useful before surgery to help plan implantation of pacemaker or cardioverter defibrillator.
Treating Heart Rhythm Disorders
The treatment of heart rhythm disorders depends on the type of disorder and its severity. Many abnormal heart rhythms may be treated by dietary and lifestyle changes such as not smoking, reducing caffeine intake, limiting alcohol intake, avoiding decongestants, and minimizing stress. Drug therapy may also be necessary.
The following chart summarizes types of drugs that may be used to help treat heart rhythm disorders. Brand names are :
Type of Drug: Anti-arrhythmics
Function: temporarily correct slow or fast heartbeat
Function: temporarily correct slow or fast heartbeat
Examples: amiodarone (Cordarone), disopyramide (Norpace), lidocaine (Xylocaine), procainamide (Procan), propafenone (Rythmol), propranolol (Inderal), sotalol (Betapace)
Type of Drug: Beta blockers
Function: reduce the heart’s workload
Examples: nadolol (Corgard), metoprolol (Lopressor, Toprol XL), pindolol (Visken), bisoprolol (Zebeta), and acebutolol (Sectral)
Function: reduce the heart’s workload
Examples: nadolol (Corgard), metoprolol (Lopressor, Toprol XL), pindolol (Visken), bisoprolol (Zebeta), and acebutolol (Sectral)
Type of Drug: Calcium channel blockers
Function: increase blood flow through the heart and help prevent blood vessel constriction by blocking calcium ions
Examples: verapamil (Calan, Isoptin, Verelan), diltiazem (Cardizem, Tiamate, etc.) and nifedipine (Adalat)
Type of Drug: Anticoagulants or antiplatelets
Function: work as blood thinners
Examples: aspirin, warfarin (Coumadin)
In some cases, surgery may be necessary to help treat heart rhythm disorders. Depending on the type of disorder and its severity, one of the following procedures may be performed:
Pacemaker implantation:
An artificial pacemaker can be surgically implanted to help correct bradycardia (slow heartbeat), a condition that can worsen congestive heart failure. The surgery involves implanting an artificial pacemaker into the patient’s chest, which uses batteries to deliver an electrical impulse when an irregularity of the heart rhythm is detected. Many pacemakers have sophisticated sensory systems which allow them to function only when necessary.
Cardioverter defibrillator implantation: Involves implanting leads on the heart’s surface, which are connected to a pulse generator implanted under the skin near the chest or abdomen. The device delivers electrical shocks to the heart to help restore a normal rhythm. Like pacemakers, implantable cardioverter defibrillators have sophisticated sensory systems that allow them to record activity and adjust electrical pulses based on the heart’s activity.
Radiofrequency ablation: Involves using angiography to guide insertion of a catheter with an electrode on its tip to a portion of the myocardium (heart muscle) with access to an electrical pathway. Mild radiofrequency pulses are then emitted to the pathway, causing a small area of myocardium cells to stop conducting extra impulses (the source of rapid heartbeats). Radiofrequency ablation may be used to treat supraventricular tachycardias (fast heartbeats) or other arrhythmias such as Wolff-Parkinson-White syndrome.
