Cardiac Arrhythmia

Cardiac Arrhythmia

Cardiac arrhythmia is an irregular heartbeat in which the heart beats are too fast (tachycardia), too slow (bradycardia), or in an abnormal rhythm.

There are a wide variety of cardiac arrhythmia’s and while some are harmless, others can be life-threatening. Arrhythmia’s are concerning because they can potentially reduce the amount of blood being pumped through the body and lead to more serious conditions such as heart attack. Since blood carries oxygen to all the tissues in the body, including the heart, a reduction in blood flow could lead to tissue death of the heart and organ damage.

Pathology of healthy heartbeat

The heart consists of 4 chambers: two upper chambers called the atria and two lower chambers called the ventricles. A heartbeat is initiated by an electrical signal generated in a group of cells at the top of the right atrium called the sinus node or sinoatrial (SA) node.

This signal travels down through the atria, causing them to contract and pump blood into the ventricles. The signal then moves down to a second node between the atria and ventricles called the atrioventricular (AV) node. Once the ventricles are full of blood, the signal travels down the ventricles on a pathway called the bundle of His. This causes the ventricles to contract and pump blood to the lungs or other areas of the body.

The ventricles then relax and the process starts over again. In a healthy heart 60 to 100 signals are sent per minute. Any issues that arise in this process could lead to cardiac arrhythmia.

What causes cardiac arrhythmia?

Heart arrhythmia is caused by anything that blocks, delays, or alters the electrical signals that regulate the heartbeat. Changes to these electrical signals can be due to a number of reasons including:

· Damage to the AV or SA nodes

· Damage to the bundle of His

· Production of electrical signals in other parts of the heart

Lifestyle Factors

Arrhythmia’s can be triggered by lifestyle factors such as smoking, drinking, high amounts of caffeine and other substances.

Smoking and Nicotine

Clinical trials have found that smokers have an increased risk of developing cardiac arrhythmia’s compared to non-smokers. Smoking also promotes coronary heart disease and chronic obstructive pulmonary disease (COPD), which themselves can promote arrhythmia’s.

Nicotine

Nicotine has been linked to several forms of cardiac arrhythmia including:

· Transient sinus arrest

· Bradycardia

· Sinus tachycardia

· Atrial fibrillation

· Sinoatrial block

· AV block

· Ventricular tachyarrhythmia

There are many ways in which nicotine can cause irregular heartbeats. For example, nicotine is linked to increased levels of catecholamine, which is a type of neuromodulator and hormone that is released in the blood when the body is under stress. While high catecholamine levels can lead to increase heart rate and blood pressure, extremely high levels can result in arrhythmia.

Nictoine can also bind to and block the potassium channel called (I K1), which can result in irregular heartbeats. This block specifically occurs when nicotinic acetylcholine receptors (nAChR) are not stimulated and catecholamines are released, thus generating arrhythmias.

Nicotine has also been found to increase atrial fibrosis, which is the thickening of the atria walls that can make pumping blood more difficult. This thickening, particularly after heart failure, increases the likely hood of atrial fibrillation and other arrhythmias. Nicotine causes atrial fibrosis by blocking the activity of two micro-RNA (mi-R-133 and miR-590), which inhibits transforming growth factor (TGF)-β1 and TGF-β receptor type II, and thus blocks the modulators of connective tissue growth factor.

Not only is nicotine from smoking potentially harmful, but chewing and inhaling second hand nicotine can increase the chances of developing short-term atrial fibrillation and other arrhythmias as well.

Carbon Monoxide

Nicotine is not the only component of tobacco smoke that promotes heart arrhythmia, carbon monoxide is also harmful. Inhaled carbon monoxide binds to hemoglobin, the protein in red blood cells that transports oxygen. This results in fewer cells being able to carry oxygen and thus, few cells releasing oxygen in the body, which leads to stress on the body. Carbon monoxide also increases susceptibility to ventricular fibrillation and ventricular arrhythmia.

Oxidative Stress

There is conflicting clinical trial evidence suggesting that oxidative stress due to smoking may also contribute to atrial fibrillation. However, animal studies have shown that oxidative stress can alter heart tissue resulting in more arrhythmogenic events. There is evidence that smoking-related oxidative stress promote various cardiovascular diseases.

Environmental Tobacco Smoke

Second hand smoke is now thought to be just as dangerous, if not more, than primary contact smoke. This is due to the fact that when you are inhaling smoke in the air it is going straight to your lungs unfiltered, rather than being partly filtered by the filter at the end of the cigarette. Studies have found associations between heart rate variability and environmental tobacco smoke exposure.

Postoperative atrial fibrillation associated with smoking

Up to 30% of patients experience postoperative atrial fibrillation (POAF) following heart surgery. There is evidence that smoking may actually reduce the risk of developing POAF. This is believed to be because smoking results in a higher adrenergic state, which allows smokers to tolerate increases in catecholamine induced from surgical stress. This protective effect disappears in people that have quit smoking.

Heavy alcohol use

Drinking alcohol can slow the intra-atrial conduction, the His-ventricular interval, and shortened sinus node recovery time during electrical impulse stimulation of the heartbeat. Atrial and ventricular tachyarrhythmia could be induced in 71% of cases in moderate to heavy drinkers. Patients with atrial fibrillation that drink experience shorter atrial refractory times and slowed conduction compared to nondrinkers.

There are several potential mechanisms by which alcohol could promote cardiac arrhythmia. One of which is that alcohol has been shown to cause damage to gap junction intracellular channels, resulting in abnormal signal conduction. Alcohol can also cause myocyte (heart cell) damage, inflammation, and short term oxidative stress.

Not surprisingly, alcohol has several electrophysiological effects such as reducing atrial and pulmonary vein action potentials, shortening the atrial refractory period, reducing the speed of intra- and inter-atrial conduction, and enhancing AV-node conduction. All of this is to say that alcohol changes the way in which the electoral system in the heart operates and can lead to abnormal heartbeats.

Lastly, alcohol can have autonomic effects on the heart such as shortening the activity of the vagal nerve. The vagal nerve is what stimulates the heart to beat, thus increasing the activity of this nerve will increase the chances of heart rate variability.

Long term consumption of alcohol leads to several conditions that can cause changes to atrial activity leading to arrhythmia. These conditions include left ventricle remodeling, obstructive sleep apnea, high blood pressure, atrial inflammation and oxidative stress. All of these promote left atrial remodeling, dilation, fibrosis and increase left atrial pressure. Any of these, supported by vagal nerve activation and/or short term binge drinking, promote atrial fibrillation.

Substance Abuse (specifically cocaine and amphetamines)

· Some prescription and over-the-counter drugs

High levels of caffeine

Animal studies revealed that exposure to high levels of caffeine increased susceptibility to ventricular fibrillation in non-ischemic and ischemic animal models. However, this increase can be blocked by treatment with beta blockade, which lowers heart rate. Animals taking high doses, but not moderate doses of caffeine, also were more susceptible to ventricular tachycardia induced by ventricular pacing. Another study observed an increase in the incidence of supraventricular and ventricular arrhythmias with moderate doses, while other forms of arrhythmia (ventricular tachycardia, atrial flutter and atrial fibrillation) were seen at higher doses. Caffeine is also capable of increasing the rate of spontaneous discharge from active fibers.

Human studies have found that caffeine can affect the refractory period of atrial, ventricular and nodal tissue. However, it is unclear how this relates to susceptibility for arrhythmia. Patients with ventricular ectopy have an increased risk of experiencing heart beat irregularities when ingesting caffeine. However, there is insufficient evidence to show an increase in risk for other patients already susceptible to cardiac arrhythmia such as patients that have recently experienced a heart attack, non-sustained ventricular tachycardia, or malignant ventricular arrhythmia.

Emotional distress such as intense emotional stress and anger

Emotional distress causes the heart to pump harder, resulting in raised blood pressure and release of stress hormones that can cause arrhythmias

Heart Failure

Heart failure occurs when the body is unable to pump body in a way that sufficient supplies the body with blood. Atrial fibrillation occurs in 19-37% of individuals living with heart failure. However, it occurs in up to 50% of individuals hospitalized during heart failure.

Heart conditions that damage the heart’s electrical system include:

o High blood pressure

o Coronary heart disease

o Heart failure

o Overactive thyroid gland (high thyroid hormone production)

o Underactive thyroid gland (low thyroid hormone production)

o Rheumatic heart disease

o Congenital heart defects (i.e. heart effects present at birth) like Wolff-Parkinson-White syndrome.

Symptoms of Arrhythmia

Symptoms of cardiac arrhythmia depend on disease type, frequency and severity. Common symptoms of cardiac arrhythmias include:

· Sensation of fluttering the chest

· Rapid heartbeat

· Slow heartbeat

· Chest pain

· Shortness of breath

· Lightheadedness

· Dizziness

· Sweating

· Fainting

How is cardiac arrhythmia diagnosed?

To diagnose cardiac arrhythmia several factors, including personal and family medical histories, physical examination, and various tests will be used. Arrhythmias may be diagnosed by a primary care provider or by a specialist such as cardiologist or electrophysiologist, which is a cardiologists who specialized in arrhythmias. Diagnostic tests include the following:

Electrocardiogram (EKG, ECG)

An EKG is a non-invasive test to record the heart’s electrical activity. It shows the speed and rhythm at which the heart is beating as well as the strength and timing of the electrical signals in the heart.

A standard EKG records only for a few seconds, which means you only have a few seconds to detect the irregular heartbeat. This means less consistent arrhythmias are easy to miss. Thus, to detect infrequent episodes of arrhythmia, portable EKGs are often used. These include Holter and Event Monitors.

A Holter monitor records electrical activity for 1 to 2 days continuously. It involves wearing electrodes on the chest that are connected to a portable recorder that is fixed around the neck or on a belt.

Event monitors only record electrical activity when they are turned on by the user, which is usually when the symptoms are occurring. However, some event monitors can recognize the symptoms and turn on automatically. Event monitors can be worn for a day up to weeks.

Stress test

For detection of cardiac arrhythmias that cause symptoms prominently when the heart is working harder, a stress test may be given. The test involves increasing the work of the heart through exercises such as walking on a treadmill or using a pedal bike. Heart tests are then conducted during the exercise to see if an arrhythmia will be detected. For individuals that cannot exercise, they may be given a medication to make their heart beat harder.

Echocardiography (echo)

To identify low blood flow, abnormal heart contraction, and heart damage caused by low blood flow, an echocardiography, which is a live image of the heart may be ordered.

To preform an echo, a transducer is moved across the chest emitting sound waves through the chest wall to the heart. The sound waves bounce off structures of the heart which the computer converts into an image of a moving image of the heart. This image reveals the size and shape of the heart and how the chambers of the heart are working.

Transesophageal Echocardiography

Similar to echo, transesophageal echo or TEE, uses sound waves to take pictures of the heart. However, it takes these images through the esophagus, the tube connecting the mouth to the stomach. Because the atria can be difficult to see with echo, TEE may be used instead to get a better image.

During this test, a transducer is placed on the end of a tube that is passed down the throat into the esophagus. TEE is primarily used to detect blood clots in the atria.

Electrophysiology Study

This test evaluates the electrical activity of the heart on order to locate the origin of the arrhythmia. The test is done by threading catheters, followed by wires, through blood vessels to different locations in the heart to determine exactly where the abnormality is located.

Chest X Ray

In order to detect fluid build-up in specific organs in the chest such as the heart and lungs, a chest x ray may be given. Fluid buildup in the lungs is a common sign of A Fib.

Blood Tests

Many arrhythmias are due to underlying conditions outside the hear. Testing for abnormal levels of hormones, electrolytes, and blood cells can help to identify both cardiac and non cardiac root causes. Thyroid hormone imbalance, for example, is a common cause of arrhythmia.

Coronary catheterization

Coronary catheterization is performed to determine if the coronary arteries are blocked by plaque or a clot. To preform a catheterization, a catheter is threaded through a blood vessel and guided to the heart. A dye is then injected into a catheter, making the arteries visible on X-ray, so any blockages or narrowing of the arteries can be seen.

Treatment of Cardiac Arryhythmia

There are several different types of treatments for cardiac arrhythmias.

Blood Clot Prevention

Some cardiac arrhythmic conditions, such as A Fib, run the risk of inducing stroke. Thus, blood-thinning mediations such as warfarin, dabigatran, heparin and aspirin may be recommended. While these medications will reduce the risk for stroke by lowering blood clot factors, they will also increase the risk for prolonged bleeding. Thus careful monitoring is needed while on these medications.

Rate Control Medication

Rate control medicines may be prescribed to reduce the heart beat rate of the ventricles. These medications are recommended for most individuals with A Fib. While they may not bring the heart beat to a normal level, they significantly reduce the work the heart has to do. Heart rate is typically controlled with beta blockers (such as metoprolol and atenolol), calcium channel blockers (diltiazem and verapamil) and digitalis (digoxin).

Cardio sinus massage

This form of massage is provided by a trained professional. It involves putting pressure on the neck where the carotid artery divides into two sections, causing it to release chemicals that slow down the heart.

Rhythm Control Procedures

Medications

The most commonly used rhythm controlling medications include the following; amiodarone, sotalol, flecainide, propafenone, dofetilide, ibutilide and older therapies; quinidine, procainamide, disopyramide.

Cardioversion

The procedure entails shocking the heart using electrodes placed on the chest and possibly the back. The electrodes are attached to the cardioversion machine which records the heart’s electrical activity and in response sends electrical impulses to the heart.

The doctor will give an additional low-energy shocks to return the heart to a normal rhythm. This procedure is done under anesthesia so the patient does not feel any pain. Heart rhythm and blood pressure are monitored following the procedure for a few hours. Risks related to cardioversion include worsening arrhythmias and the release of a blood clot. However, anticlotting medication can be taken prior to and after the treatment to reduce the risk.

Catheter ablation

Catheter ablation is a procedure in which a section of the heart that may be causing the abnormal heart beat is scarred. This treatment is used when arrhythmias cannot be controlled by medicine or there is a high risk for ventricular fibrillation or atrial fibrillation.

The scar can be made in several ways:

· Radiofrequency ablation: Uses high-energy radiofrequency signals

· Cryoablation: Uses extremely cold temperatures

· Laser ablation: Uses laser light

Catheter ablation is performed while the patient is awake, but sedated. An opening will be made in the arm, groin, or upper thigh into a blood vessel Catheters (flexible tubes) are then threaded through the blood vessel to the targeted area in the heart using x ray imaging. Alternatively, the doctors may locate the area using electrodes at the ends of the catheters to determine the origin of the abnormal heartbeat.

Once the tip of the catheter is on the correct area, a machine will send either radiofrequency waves, cold temperatures, or laser light through the catheter to create a scar to block electrical signals from passing through the area. The catheter is then removed and the patient is monitored for the next few hours. There are some risks with this method such as bleeding, infection, blood vessel damage, arrhythmias, blood clots and cancer (from radiation).

Pacemaker

In some cases of catheter ablation, the physician may destroy the AV node, the location where the electrical signals pass from the atria to the ventricles. Following this treatment, a pacemaker will be implanted under the collarbone with electrodes to the heart to maintain normal heart rhythm.

Implantable cardioverter-defibrillator

Implantable cardioverter-defibrillators or ICDs may be used if the patient is at high risk of experiencing irregular or fast heart beat in the ventricles, particularly in cases of ventricular tachycardia, ventricular fibrillation, or after sudden cardiac arrest. ICDs are battery-powered implantable devices that are placed under the skin by the collarbone. Electrodes run from the device to the heart and monitor heart rhythm. If an abnormal heart rhythm is detected, the device shocks the heart to return it to a normal rhythm.

Maze Surgery

Maze surgery is typically only done when the patient is getting open heart surgery for another condition. This treatment involves placing cuts and burns in the atria to prevent the spreading of disorganized electrical signals.

Other Treatments

Vagal maneuvers

These maneuvers are performed to stop episodes of SVT currently in progress. Maneuvers are done by the patient and include

· Holding one’s breath and straining

· Dunking one’s face in cold water

· Coughing

Types of Cardiac Arrhythmia

Atrial Fibrillation (A Fib)

Atrial Fibrillation, also known as A Fib, is the most common form of arrhythmia. A Fib is defined as a rapid and irregular heartbeat.

Causes of A Fib

It is caused by quick, disorganized electrical signals sent to the atria causing them to beat quickly and abnormally. In a normal heartbeat, the electrical signals originate from the SA node. However, in the case of A Fib, the electrical signals originate in another region of the atria or in the pulmonary veins and spread throughout the atria causing them to fibrillate.

The signals then move to the AV node causing the ventricles to also beat abnormally fast. Overall, this disorganized signal results in the atria and ventricles to beat out of sync causing an abnormal heart beat. Not only does this cause the atria to flood with blood, preventing all the blood from pumping into the ventricles, A Fib causes the ventricles to pump out random amounts of blood to the body.

There are three types of A Fib:

· Paroxysmal A Fib: In the case of paroxysmal A Fib, the abnormal symptoms begin and end suddenly. Symptoms of this form can be mild to severe and usually last less than 24 hours.

· Persistent A Fib: Persistent a Fib symptoms lasts longer than a week. This form may stop on its own or may need to be stopped with medication.

· Permanent A Fib: In this form of A Fib, regular heart beat cannot be restored even with treatment. This form results gradually from frequent episodes of persistent and paroxysmal A Fib.

Symptoms of A Fib

Common symptoms of A Fib include:

· A fluttering sensation in the chest

· A rapid heart beat (heart palpitations)

· A sensation that the heart has skipped a beat

· Shortness of breath

· Difficulty exercising

· Chest pain

· Dizziness

· Fainting

· Fatigue

· Confusion

While an individual with A Fib may not exhibit any symptoms, it still can lead to severe complications such as stroke and heart failure.

Risk Factors of A Fib

A Fib is triggered by injury to the heart usually resulting from a heart related condition such as high blood pressure or coronary heart disease. Risk factors include

· Age

· High blood pressure

· Coronary heart disease

· Heart failure

· Heart attack

· Surgery

· Rheumatic heart disease

· Mitral valve prolapse and other structural heart defects

· Pericarditis

· Congenital heart defects

· Sick sinus syndrome: when electrical signals of the heart do not always fire

· Hyperthyroidism (a high level of thyroid hormone)

· Obesity

· Diabetes

· Lung disease

· Modest to excessive consumption of alcohol

· Caffeine

· Stress

· Sleep Apnea

· Metabolic syndrome

· High doses of steroid therapy

· Inflammatory conditions

A Fib Prevention

Living a healthy lifestyle can reduce the risk of developing A Fib and associated heart diseases. Healthy lifestyle changes include:

· Heart healthy diet

· Quit smoking

· Exercise

· Maintaining a healthy weight

For individuals with risk factors for A Fib, it is recommended they:

· Lower their blood pressure

· Maintain healthy levels of cholesterol with diet or medications, if needed

· Limit alcohol consumption

· Individuals with diabetes should control blood sugar levels

· Maintain a heart healthy diet (variety of grains, fruits, vegetables with low levels of fat and cholesterol)

A Fib Treatment

The best treatment for A Fib depends largely on the symptoms and severity of the disease and heart disease comorbidity. Individuals with A Fib that do not show any symptoms or have any co-existing heart conditions may not need treatment.

Treatments used for A Fib include:

· Blood clot prevention with blood thinning medications. The risk of stroke is higher for individuals with A Fib because the blood is pumped out of the atria less efficiently, which increases the thickness of the blood in the atria and thus increases the chances of a clot forming. Once formed, the clot can then leave the heart and travel to the brain, where it may get trapped in the blood vessels and block blood flow to the brain, resulting in a stroke. Blood clot prevention is one of the primary goals of A Fib treatment. Commonly used blood-thinning medication include warfarin, dabigatran, heparin and aspirin.

· Rate Control with Beta and Calcium Channel Blockers is another common treatment option. Oral medications such as beta and calcium channel blockers will be prescribed to reduce the rate of the ventricles. These medications are recommended for most individuals with A Fib. While they may not bring the heart beat to a normal level, they significantly reduce the work the heart has to do. Heart rate is typically controlled with beta blockers (such as metoprolol and atenolol), calcium channel blockers (diltiazem and verapamil) and digitalis (digoxin).

· Rhythm Control. For individuals in which rate control medications are not helping the condition, rhythm control medicines and procedures may be used. These treatments are often used in those that have just developed A Fib, since it is less likely to help the longer the patient has A Fib (especially for cases lasting longer than 6 months). Rhythm control treatments are also less effective in those that have a coexisting heart condition that has gotten worse or enlarged atria.

Commonly used medications include the new generationsaiodarone, sotalol, flecainide, propafenone, dofetilide, and ibutilide) and older therapies (quinidine, procainamide, and disopyramide)

When medication are not enough, procedures may need to be ordered. Rhythm controlling procedures include; cardioversion, catheter ablation, pacemakers, and maze surgery.

Reducing risk factors is another treatment option. The following actions can be taken to reduce the risk of A fib

o Taking medication to control overactive thyroid

o Lowering high blood pressure

o Managing high cholesterol

o Eating a healthy diet

o Reducing salt intake

o Quitting smoking

o Reducing stress

o Limiting alcohol, caffeine and other stimulants

Premature ventricular contractions

Premature ventricular contractions, also known PVCs are extra beats of one of the ventricles. These extra heart beats are relatively common and often feel like a fluttering of the heart or like the heart has skipped a beat. This occurrence is of relatively little concern for individuals that experience it periodically and do not have a heart condition.

Symptoms of premature ventricular contractions include:

· Heart fluttering

· Heart pounding

· Sensation that the heart has missed a beat

· Increased awareness of the heart

These extra beats may occur because the ventricles are beating slightly out of order of when they should. This can occur when changes in the body cause the cells in the ventricles to become electrically unstable. Some situations include:

· Taking specific medications (such as antihistamines and decongestants)

· Consumption of alcohol or illegal substances

· High levels of adrenaline due to caffeine, tobacco, exercise or anxiety

· Heart damage from heart diseases such as coronary artery disease, congenital heart disease, high blood pressure or heart failure

Risk factors for extra heart beats include:

· Substances that increase adrenaline (caffeine, tobacco, alcohol, illegal substances)

· Exercise (for certain forms of the disease)

· High blood pressure

· Anxiety

· Heart diseases (such a congenital heart disease, coronary artery disease, heart attack, heart failure, and cardiomyopathy (weakened heart muscle)

Premature ventricular contractions can be diagnosed through many ways. The most common method is using an electrocardiogram (ECG). If premature heartbeats are experienced infrequently, a portable monitoring device can be worn for a day to record electrical activity.

While in most healthy individuals premature ventricular contractions do not need to be treated, in individuals with heart problems, the condition may need to be managed. Common management strategies include lifestyle changes that reduce risk factors to reduce the frequency and severity.

Medications, such as beta blockers, a medication commonly used to treat high blood pressure and heart disease, can also be used to reduce premature heartbeats. Medications for other arrhythmic conditions such as ventricular tachycardia medications amiodarone and flecainide could also help reduce this condition. In severe, refractory cases of premature heartbeat, radiofrequency catheter ablation may also be used. This is a procedure done to destroy regions of the heart responsible for the extra heartbeats.

Supraventricular Arrhythmia

Supraventricular arrhythmia or paroxysmal supraventricular tachycardia (SVT) is the sudden rapid beating of the heart for reasons other than exercise, fever and stress.

There are three common types of SVT:

· atrioventricular nodal reentrant tachycardia (AVNRT): The most common SVT. While seen in both males and females, it is more common in young women.

· atrioventricular reciprocating tachycardia (AVRT): The second most common SVT. AVRT is mainly seen in younger individuals.

· Atrial tachycardia: Atrial tachycardia is not caused by issues involving the AV node (like the other subtypes). It is commonly seen in individuals with coexisting heart disease

Other types of SVT include:

· Sinus tachycardia

· Inappropriate sinus tachycardia (IST)

· Multifocal atrial tachycardia (MAT)

· Junctional ectopic tachycardia (JET)

· Nonparoxysmal junctional tachycardia (NPJT)

During SVT the heart beats between 100 and 300 times per minute (compared to 60 to 100 times per minute in a healthy individual).

SVT symptoms include:

· Fluttering sensation in the chest

· Rapid heartbeat

· Shortness of breath

· Lightheadedness

· Dizziness

· Sweating

· A pounding sensation in the neck

· Fainting (syncope)

In some individuals SVT comes and goes quickly; the induvial may not experience any symptoms at all. SVT symptoms can last a few minutes or a few days. SVT is primarily a concern in individuals that experience symptoms for long stretches of time and with a history of heart disorder.

There are a number of causes for SVT including:

· Heart failure

· Thyroid disease

· Heart disease

· Chronic lung disease

· Smoking

· Excessive alcohol consumption

· Excessive caffeine consumption

· Use of illicit drugs (i.e. cocaine and methamphetamines)

· Asthma medications and over-the-counter cold and allergy drugs

· Surgery

· Pregnancy

· Other health conditions, particularly Wolff-Parkinson-White syndrome

Risk factors of SVT include:

· Age: SVT is the most common type of arrhythmia seen in children and infants. However, there are some forms that are more common in middle-aged and elderly individuals.

· Sex: Women, especially pregnant women, are more likely to experience SVT

· Heart disease such as coronary artery disease, narrowed heart arteries, heart attack, abnormal heart valves, heart failure, cardiomyopathy, other heart damage, congenital heart disease and heart surgery

· Thyroid problems

· Consumption of over-the-counter drugs (such as cough drops and cold medicine) as well as prescription drugs

· Use of nicotine and illicit drugs (particularly amphetamines and cocaine)

Management and prevention

Prevention largely involves identifying and avoiding triggers of SVT episodes. Other helpful actions include:

· Healthy diet

· Increased physical activity

· Avoiding smoking

· Maintaining a healthy weight

· Limiting alcohol

· Reducing stress

· Obtaining adequate sleep

· Limiting use of over-the-counter drugs

· Avoiding illicit drug use

· Maintain healthy blood pressure

· Maintain healthy cholesterol levels

· Practice yoga, meditation and other relaxation strategies

Similar to premature ventricular contractions, SVT may be diagnosed by use of a standard or portable ECG. An echocardiogram, which uses transducers placed on the chest, instead of electrodes, that emit soundwaves to generate images of the heart that include size, structure and motion. In other cases implantable loop recorders may be placed under the skin in the chest to detect abnormal heart beats. In addition to some of these tests, physicians may also test for other conditions that have been shown to associate with SVT like other heart diseases.

Although many cases of SVT do not require treatment, in individuals with symptoms that last for a long period of time or occur more frequently, the following may be recommended:

· Cardio sinus massage

· Vagal maneuvers

· Cardioversion

· Anti-arrhythmic medication

· Catheter ablation

Atrial Flutter

As the name suggests, atrial flutter is the rapid beating (240-400 beats/min) of the atria. The rapid beating may also occur with a block on AV node conduction. This is different from A Fib in that the beating is more regular and organized with atrial flutter.

There are two types of atrial flutter:

· Typical (classic) atrial flutter (80% of cases): the electrical signal from the right atrium travels in a counterclockwise direction around the atrium

· Atypical atrial flutter: Originate in the right atrium due to surgical scars or from the left atrium, especially after ablation procedures for A Fib.

Comorbidity

Atrial flutter is typically associated with

· Coronary artery disease (30% of cases

· High blood pressure (30% of cases)

· Surgical procedure and congenital heart diseases (26% of cases).

· Unrelated to other heart diseases (30% of cases)

· In rare cases, atrial flutter can result from

o Rheumatic heart disease

o Pericarditis

o Cardiomyopathy

o Mitral valve prolapse

o Acute myocardial infarction

o Hypoxia

o Chronic obstructive pulmonary disease

o Pulmonary embolism

o Hyperthyroidism

o Pheochromocytoma

o Diabetes

o Electrolyte imbalance

o Alcohol consumption

o Obesity

o Digitalis toxicity

o Myotonic dystrophy in childhood

Symptoms of Atrial flutter

· Rapid heart beat

· Fatigue

· Difficulty breathing (dyspnea)

· Chest pain

Diagnosis

Atrial flutter is typically diagnosed with

· ECG

· TTE

Treatments

Treatments center on controlling the ventricular response and sinus rhythm. Thus, electrical cardioversion is commonly used for those with unstable blood flow. Catheter-based ablation is associated with the best outcome for atrial flutter therapy. However, prognosis depends largely on comorbidity and the nature of the disease.

Epidemiology

Atrial flutter is far less common than A Fib. However, it is much more common in men. Approximately, three of every four cases occurred in men. It is also much more common in individuals 65 years old and older.

Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome or WPW is a rare congenital condition in which an additional electrical pulse is sent between the atria and ventricles, resulting in a rapid heartbeat. While the condition itself is not severe, it can lead to the development of more serious heart conditions.

Causes

The additional electrical pathway is the result of a genetic mutation. It may also occur in conjunction with Ebstein’s anomaly, a congenital heart disease. The additional electrical pathway bypasses the AV node causing the ventricles to beat too soon.

The pathway can alter the heartbeat in two ways:

· Looped electrical impulses: the pulses travel down the normal pathway and then back up the extra pathway or vise versa. This specific response is known as AV reentrant tachycardia.

· Disorganized electrical impulses: occurs when the electrical impulses don’t begin in the right atrium resulting in dispersion across the atria in a disorganized way, leading to A Fib.

Common symptoms

· Sensation of a rapid heartbeat, fluttering, or pounding in the chest (a few seconds to hours)

· Dizziness

· Lightheadedness

· Shortness of breath

· Fainting

· Fatigue

· Anxiety

Infants may have additional symptoms such as

· Ashen color

· Restlessness

· Rapid breathing

· Poor eating

Severe symptoms (10 to 30% of cases)

Development of A Fib resulting in A Fib symptoms

o Chest pain

o Chest tightness

o Difficulty breathing

o Fainting

WPW can be diagnosed using

· ECG (standard or portable)

· Electricophysiological testing

Treatment

If an individual with WPW does not experience any symptoms, they may not need treatment. As is the case with most heart arrhythmia conditions, the type of treatment used depends on the severity and frequency of the condition. Potential treatments include:

· Vagal maneuvers

· Anti-arrhythmic medication

· Cardioversion

· Radiofrequency catheter ablation

Ventricular Arrhythmia (Originating in the Ventricles)

Ventricular Tachycardia

Ventricular tachycardia is a rapid heart rate (170 beats per minute) originating from the ventricles. This results in a decrease in blood pressure which prevents a sufficient amount of oxygen from reaching all the tissue in the body.

Symptoms

· Dizziness

· Lightheadedness

· Sensation of a rapid heartbeat, pounding or heart flutter

· Shortness of breath

· Chest pain

In severe cases, ventricular tachycardia can lead to:

· Fainting

· Loss of consciousness

· Cardiac arrest

· Death

Ventricular tachycardia typically occurs with another heart condition such as:

· Coronary heart disease

· High blood pressure

· Cardiomyopathy

· Heart valve disease

· Following a heart attack

· Following heart surgery

Risk factors for ventricular tachycardia include:

· Specific medications

· Electrolyte imbalance

· Excessive consumption of caffeine

· Excessive alcohol intake

· Use of illicit drugs

· Exercise

· Genetic predisposition

Diagnosis

Ventricular tachycardia is typically diagnosed using a standard or portable ECG, or an electrophysiology test.

Common treatments include

· Radiofrequency catheter ablation

· Implantation of an implantable cardioverter defibrillator

· Medications that slow down heart rate

Ventricular Fibrillation (V-Fib)

Similar to A Fib, ventricular fibrillation occurs when the heart displays erratic heart beat due to disorganized, rapid electrical impulses. However, in the vase of ventricular fibrillation, the ventricles quiver, resulting in inadequate pumping of blood to the lungs and body.

Ventricular fibrillation needs to be treated immediately. The condition usually causes blood pressure to drop rapidly, causing the individual to collapse almost immediately. It is one of the primary causes of sudden cardiac death.

Causes

V-Fib usually results from alterations in electrical signals sent through the heart after a heart attack or scars that form on the heart following a heart attack. Ventricular tachycardia may also contribute to the development of V-Fib.

Treatment

· Cardiopulmonary resuscitation (CPR)

· Defibrillation

· Treatments for coronary artery disease (Coronary angioplasty and stent placemen or coronary bypass surgery)

Risk factors for V-Fib

· Previous v-fib episode

· Previous heart attack

· Congenital heart disease

· Cardiomyopathy

· Injury to the heart

· Use of illicit drugs

· Electrolyte imbalance

Prevention

To prevent sudden cardiac death, individuals with ventricular fibrillation are treated with medications and implanted devices such as pace makers to achieve and maintain normal heart rate.

Early signs of V-Fib include

· Chest pain

· Sensation of rapid heart beat

· Dizziness

· Nausea

· Shortness of breath

· Loss of consciousness

Diagnosis

V-Fib is only diagnosed during a medical emergency through monitoring heart beat or a pulse check in which no pulse can be detected. Causes of ventricular fibrillation can be determined using

· ECG

· Blood tests

· Chest X-rays

· Echocardiogram

· CT scan

· MRI

· Coronary catheterization

Premature Ventricular Complexes (PVC)

Premature ventricular complexes (also known as PVC, ventricular premature beats, or ventricular extrasystoles) are additional of one of the ventricles. These additional beats result in the sensation of the heart skipping a beat due to a disrupted heartbeat. This condition usually does not need to be treated in healthy individuals not experiencing symptoms.

Nicotine can also bind to and block the potassium channel called (I K1), which can result in irregular heartbeats. This block specifically occurs when nicotinic acetylcholine receptors (nAChR) are not stimulated and catecholamines are released, thus generating arrhythmias.

Symptoms:

· Sensation of the heart skipping a beat

· Fluttering, pounding, or jumping sensation in the chest

· Heightened awareness of heartbeat

Causes and Risk Factors

· Medications (including decongestants and antihistamines)

· Alcohol use

· Illicit drug use

· High levels of adrenaline (resulting from caffeine, tobacco use, exercise or anxiety)

· Injury to the heart

PVC is usually diagnoses through ECG. Treatments include leading a heart healthy lifestyle, use of beta blockers, or radiofrequency catheter ablation.

Sinus Irregularities

1. Sinus Arrhythmia

2. Sinus tachycardia

3. Sick sinus syndrome

4. Sinus node dysfunction

Others forms of Arrhythmia

1. Accessory pathway tachycardias

2. AV nodal reentrant tachycardia

3. Ventricular tachycardia (V-tach)

4. Ventricular fibrillation

5. Long QT syndrome

6. Bradyarrhythmias

7. Heart bloc

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