Introduction

Heart rhythm problems (arrhythmias) occur when the electrical impulses traveling in your heart don’t function properly, causing your heart to beat too fast, too slow or irregularly.

Most people have occasional, irregular heartbeats that may feel like a skipped, fluttering or racing heart. Arrhythmias are common and usually harmless However, some heart arrhythmias may sometimes be even life-threatening.

Signs and symptoms

Arrhythmias may not cause any signs or symptoms. But often, abnormal heart rhythms cause noticeable signs and symptoms such as:

• Shortness of breath
  
  
• Dizziness or near fainting
  
  
• Palpitations - a racing heartbeat
  
  
• Slow heartbeat or fluttering in your chest
  
  
• Chest pain
  
  
• Light-headedness

Noticeable signs and symptoms don't always indicate a serious problem. Some people who feel arrhythmias don't have a serious problem, while others who have life-threatening arrhythmias have no symptoms at all.

Normal heartbeat

When your heart beats, the electrical impulses that cause it to contract usually follow a precise pathway through your heart. Any interruption in these impulses can cause an arrhythmia.

The heart is divided into four chambers. Two upper and two lower chambers called atria and ventricle respectively.

During a heartbeat the upper chambers (atria) contract and fill the relaxed lower chambers (ventricles) with blood. This contraction is initiated when the sinus node — a small group of cells in your right atrium — sends an electrical impulse causing your right and left atria to contract. The impulse then travels through your ventricles, causing them to contract.

Causes

Common causes of arrhythmias, include heart disease, high blood pressure, diabetes, smoking, excessive use of alcohol or caffeine, drug abuse, stress, Over-the-counter medications and prescription medications. Dietary supplements also can cause arrhythmias in some people.

Scarring from a previous heart attack may disrupt the initiation or conduction of electrical impulses. It can cause arrhythmia especially ventricular in origin.

• Inadequate blood supply
  If blood supply to the heart is reduced, this can alter the ability of heart tissue that conducts electrical impulses to function improperly.
  
  
• Damage of heart tissue
  When heart tissue becomes damaged or dies, this can affect the way electrical impulses spread in the heart.
  
  
• Coronary artery disease
  Coronary artery disease is most closely associated with ventricular arrhythmias and sudden cardiac death. Narrowing of the arteries that occurs with CAD can lead to a heart attack which results in scarring. Electrical short circuits around the scar can prevent normal heart function by causing the heart to beat dangerously fast (ventricular tachycardia) or to quiver (ventricular fibrillation).
  
  
• Cardiomyopathy
  This occurs primarily when the heart's ventricular walls stretch and enlarge (dilated cardiomyopathy) or when the left ventricle wall thickens and constricts (hypertrophic cardiomyopathy). In either case, cardiomyopathy can produce arrhythmias.
  
  
• Valvular diseases
  Leaking or narrowing of your heart valves can lead to stretching and thickening of your heart muscle. When the chambers become enlarged or weakened, there’s an increased risk of developing arrhythmia.

Types of arrhythmias

Arrhythmias are classified not only by where they originate (atria or ventricles) but also by the speed of heart rate they cause:

• Tachycardia
  This refers to a fast heartbeat — a heart rate greater than 100 beats a minute.
  
  
• Bradycardia
  This refers to a slow heartbeat — a resting heart rate less than 60 beats a minute.

Atrial Tachycardias

Tachycardias originating in the atria include:

• Atrial fibrillation
  This fast and chaotic beating of the atrial chambers is a common arrhythmia. It mainly affects older people and the risk of developing atrial fibrillation increases past age 60.Seen in patients with high blood pressure or other heart problems. Atrial fibrillation is seldom a life-threatening arrhythmia, but over time it can be the cause of more serious conditions, such as stroke.
  
  
• Atrial flutter
  Atrial flutter is similar to atrial fibrillation. The key distinction is that more-organized and more-rhythmic electrical impulses are called atrial flutter. These occur because atrial flutter, unlike atrial fibrillation, arises from a short circuit.
  
  
• Supraventricular Tachycardia (SVT)
  SVT is a broad term that includes many forms of arrhythmia originating above the ventricles (supraventricular). SVTs usually cause a burst of rapid heartbeats. SVT may cause your heart to beat 160 to 200 times a minute. Although generally not life-threatening in an otherwise normal heart, symptoms from the racing heart may feel quite uncomfortable. These arrhythmias are common in young people.
  
  
• Wolff-Parkinson-White syndrome
  Wolff-Parkinson-White syndrome. Causes SVT. This arrhythmia is caused by an extra electrical pathway between the atria and the ventricles. This pathway may allow electrical current to pass between the atria and the ventricles through an extra pathway leading to short circuits and rapid heartbeats.

Ventricular Tachycardia

Tachycardia occurring in the ventricles include:

• Ventricular Tachycardia (VT)
  This fast, regular beating of the heart is caused by abnormal electrical impulses originating in the ventricles. Often, can cause the ventricles to contract more than 200 beats a minute. Most VT occurs in people with some form of heart-related problems. Sometimes, ventricular tachycardia last for 30 seconds or less (non-sustained) and are usually harmless, although they cause inefficient heartbeats. Still, a non-sustained VT may be a predictor for more-serious ventricular arrhythmias.. An episode of sustained VT is a medical emergency. It may be associated with palpitations, dizziness, fainting or possibly death. Without prompt medical treatment, sustained ventricular tachycardia often degenerates into ventricular fibrillation.
  
  
• Ventricular Fibrillation (VF)
  Thousands die every year of sudden cardiac death believed to be caused by ventricular fibrillation. With ventricular fibrillation, rapid, chaotic electrical impulses cause your ventricles to quiver uselessly instead of pumping blood. Without an effective heartbeat, your blood pressure drops, instantly cutting off blood supply to your vital organs — including your brain. Most people lose consciousness within seconds and immediate medical assistance including cardiopulmonary resuscitation (CPR). Your chances of survival may be prolonged if CPR is delivered until your heart can be shocked back into a normal rhythm with a device called a defibrillator. Without CPR or defibrillation, death results in minutes. Ventricular fibrillation is frequently triggered by a heart attack.

Bradycardias

Heart rate below 60 beats a minute while at rest is considered bradycardia, a low resting heart rate doesn't always signal a problem. However, if you have a slow heart rate and your heart isn't pumping enough blood, you may have one of following conditions:

• Sick Sinus Syndrome
  If your natural pacemaker, called sinus node isn't functioning properly, your heart rate may be too slow, or it may speed up and slow down intermittently. This condition is called sick sinus syndrome. Impulse from the sinus node may be slow, intermittent or even stop.
  
  
• Conduction Block
  A block in the heart’s electrical pathways can occur in or near the AV node or along pathways that conduct impulses to each ventricle. Depending on the location various types of block are present. A conduction block is usually detectable on an ECG and they may not produce any sign or symptoms.

Risk factors for arrhythmias

• Age
  With age, the heart muscle weakens and may become stiffed. This may affect normal electrical impulse conduction leading to heart blocks or arrhythmias.
  
  
• Cardiac conditions
  Coronary artery disease, abnormal valves, prior heart surgery, cardiomyopathy and other heart muscle conditions are risk factors for almost any kind of arrhythmia.
  
  
• Thyroid problems
  Excess secretion of the thyroid hormones speeds up the heart causing fast or irregular heartbeats and is most commonly associated with atrial fibrillation. Inadequate hormone levels slows metabolism and may cause a slow heart rate.
  
  
• Medications and Supplements
  Over-the-counter cough and cold medicines and certain prescription drugs may contribute to arrhythmia development.
  
  
• High Blood Pressure
  Raised blood pressure increases your risk of developing coronary artery disease. It may also cause the walls of your left ventricle to thicken and produce arrhythmias and abnormal electrical impulses conduction.
  
  
• Obesity
  Along with being a risk factor for coronary artery disease, obesity may increase your risk of developing an arrhythmia.
  
  
• Diabetes Mellitus
  The risk of developing coronary artery disease and hypertension greatly increases with uncontrolled diabetes. These can trigger an arrhythmia in the long run.
  
  
• Obstructive sleep apnoea
  This disorder can cause bradycardia and atrial fibrillation. It is also a risk factor for heart disease.
  
  
• Electrolyte imbalance
  Electrolyte levels that are too high or too low can affect your heart's electrical impulses and contribute to arrhythmia development. Electrolytes, such as potassium, calcium and magnesium, help trigger and conduct the electrical impulses in your heart.
  
  
• Alcohol
  Too much alcohol can affect the conduction of electrical impulses in your heart or increase the chance of developing atrial fibrillation. The development of atrial fibrillation after an episode of heavy drinking is sometimes called "holiday heart syndrome." Chronic alcohol abuse may lead to cardiomyopathy. Both are factors in arrhythmia development.
  
  
• Usage of Stimulants
  Stimulants, such as caffeine and nicotine, can cause premature heartbeats and may contribute to the development of more serious arrhythmias. Illicit drugs, such as amphetamines and cocaine, may affect the heart and lead to many types of arrhythmias and even sudden death due to ventricular fibrillation.

When to seek medical advice

Arrhythmias may make your heart go very fast (palpitations) or slow. The signs and symptoms may include shortness of breath or wheezing, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort. Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms.

Screening and diagnosis

To diagnose a heart arrhythmia, your doctor may perform heart monitoring tests specific to arrhythmias. Also certain additional tests may be carried out.

• Electrocardiogram (ECG)
  ECG is an essential test in screening of patients for arrhythmias. An ECG measures the timing and duration of each electrical phase in your heartbeat.
  
  
• Holter monitor
  This portable ECG device continuously monitors the heart beats over a 24 hour period. Any arrhythmia which occurs during this time is captured and the tracing can be analysed and printed in a computer.
  
  
• Trans Telephonic Monitor
  For sporadic arrhythmias, you keep this portable ECG device at home, attaching it to your body and activating it only when you experience symptoms of an arrhythmia. This could be relayed to the hospital through a telephone. This permits your doctor to determine your heart rhythm at the time of your symptoms.
  
  
• Echocardiogram
  Ultrasound waves are used to produce images of your heart and the structures within.
  
  
• Stress test
  Some arrhythmias are triggered or worsened by exercise. During a stress test, you'll be asked to exercise on a treadmill while your heart activity is monitored by an ECG. Your doctor may use a drug to stimulate your heart in a way that's similar to exercise. This may be particularly helpful if you have difficulty doing exercises, and it can also be used to detect coronary artery disease.
  
  
• Tilt table test
  Your doctor may recommend this test if you've had recurrent fainting spells. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted as if you were standing up. Your doctor observes how your heart and the nervous system that controls your heart respond to the change in angle.
  
  
• Electrophysiologic testing (EPS)
  In this test, thin, flexible tubes (catheters) tipped with electrodes are passed through your blood vessels to a variety of spots within your heart. The electrodes can precisely map the spread of electrical impulses through your heart. It is also used to stimulate your heart to reproduce the arrhythmia and once the area is spotted it can then be treated by radio frequency to halt the arrhythmia.

Complications of arrhythmias

• Stroke
  The heart is unable to pump blood effectively in atrial fibrillation. Stagnant blood in the atria may form blood clots which can break loose. This small clot can travel to and obstruct a brain artery, causing a stroke.
  
  
• Heart failure
  If your heart is pumping ineffectively for a prolonged period due to an arrhythmia such as atrial fibrillation, it may lead to heart failure. Sometimes, controlling the rate of an arrhythmia that's causing congestive heart failure can lead to improved heart function.

Treatment

Is required only if the arrhythmia is causing significant symptoms; or there is a risk of a more serious arrhythmia or arrhythmia complication.

• Bradycardias
  
  Symptom-producing bradycardias that have a cause should be corrected — such as hypothyroidism or a drug side effect. Doctors often treat pathological bradycardia with a pacemaker. A pacemaker is a small, battery-powered device that's usually implanted in the front of the chest under the collar bone. One or more wires run from the pacemaker through your blood vessels to your inner heart. If your heart rate is too slow or if it stops, the pacemaker kicks in and helps in the functioning of the heart. The pacemakers can monitor and pace your atria or ventricles or both in proper sequence.
  
  
• Tachycardias
  
  Tachycardia originating in the atria or ventricles, treatments may include one or more of the following:
  
  
  • Vagal manoeuvres
    Using certain manoeuvres, which include holding your breath and straining, immersing your face in ice water, or coughing you may be able to stop a supraventricular tachycardia .Your doctor may be able to recommend other manoeuvres to halt a fast heartbeat. These manoeuvres affect the nervous system that controls your heartbeat (vagal nerves), often causing your heart rate to slow.
    
    
  • Medications
    Anti-arrhythmic medications don't cure the problem; they can reduce episodes of tachycardia or slow down the heart when an episode occurs. It's very important to take any anti-arrhythmic medication as directed by your doctor in order to avoid complications.
    
    Cardio version
    It is an electrical shock used to reset your heart to its regular rhythm. If you have an atrial tachycardia, atrial fibrillation or supraventricular tachycardia your doctor may use cardioversion. Normally this is done externally in a monitored setting, and you're given a sedative during the procedure, to avoid any pain.
    
    
  • Radio frequency ablation
    Catheters which are passed through the blood vessels are positioned on areas of your heart identified by your doctor as causing your arrhythmia. Electrodes at the catheter tips are heated with radiofrequency energy. Another method involves cooling the tips of the catheters, which freezes the problem tissue. Both methods destroy (ablates) the small spot of heart tissue which is causing your arrhythmia. This creates an electrical block along the pathway that's causing your arrhythmia. Usually, this stops your arrhythmia.
    
    
  • Implantable devices
    
    
    • Pacemaker
      It is small battery-driven device is placed under the skin near the collarbone in a minor surgical procedure. An insulated wire extends from the device to the right side of the heart, where it's permanently anchored. Pacemakers detect a heart rate that's too slow or no heartbeat at all, it sends an electrical impulse that stimulates your heart to speed up or beat again. Most pacemakers have a sensing device that turns itself off when your heartbeat is normal. It turns back on when your heartbeat is too slow.
      
      
    • Implantable cardioverter-defibrillator (ICD)
      An ICD is a battery-powered unit that's implanted near the left collarbone something similar to a pacemaker. The ICD continuously monitors your heart rhythm. If it detects a rhythm that's too slow, it paces the heart as a pacemaker would. If it detects VT or VF, it sends out low- or high-energy shocks to reset the heart to a normal rhythm. An ICD lessen your chance of having a fatal arrhythmia.
    
    
  • Surgical treatments
    
    
    • Maze procedure
      The procedure has a high success rate, but because it requires open-heart surgery, it's usually reserved for people who don't respond to other form of treatment. A series of surgical incisions in the atria are made and they heal into carefully placed scars .These scars form boundaries that force electrical activation to proceed in an orderly manner from top to bottom.
      
      
    • Ventricular aneurysm surgery
      It involves removing the bulge (aneurysm) that's causing your arrhythmia. This requires open-heart surgery and hence it is reserved for a few only. By removing the source of the abnormal impulses, the arrhythmia often can be eliminated.
      
      
    • Coronary bypass surgery (CABG)
      Frequent ventricular tachycardia may be due to poor blood supply to your muscles. CABG may reduce or even eliminate the dangerous ventricular arrhythmia occurring.