Heart Arrhythmia; Causes, Symptoms, Diagnosis, Treatment

Heart Arrhythmia/Arrhythmia caused by disruption of the coordinated electrical activity of the heart is among the leading causes of sudden cardiac death. Blood circulation is the result of the beating of the heart, which provides the mechanical force to pump oxygenated blood to, and deoxygenated blood away from, the peripheral tissues. This depends critically on the preceding electrical activation. Disruptions in the orderly pattern of this propagating cardiac excitation wave can lead to arrhythmias. A growing list of inherited gene defects can cause potentially lethal cardiac arrhythmia syndromes, including catecholaminergic polymorphic ventricular tachycardia, congenital long QT syndrome, and hypertrophic cardiomyopathy

Cardiac Arrhythmia (also known as arrhythmia, dysrhythmia or irregular heartbeat) is a group of conditions in which the heartbeat is irregular, too fast or too slow.^[rx] A heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a heart rate that is too slow – below 60 beats per minute – is called bradycardia.^[rx] Many types of arrhythmia have no symptoms.^[rx] When symptoms are present, these may include palpitations or feeling a pause between heartbeats.^[rx] In more serious cases, there may be lightheadedness, passing out, shortness of breath or chest pain. While most types of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure.^[rx][rx] Others may result in sudden death.^[rx]

Types of Arrhythmia

Arrhythmia may be classified by the rate (tachycardia, bradycardia), mechanism (automaticity, re-entry, triggered) or duration (isolated premature beats; couplets; runs, that is 3 or more beats; non-sustained= less than 30 seconds or sustained= over 30 seconds).

• Tachycardia – A fast heart rhythm with a rate of more than 100 beats per minute.
• Bradycardia – A slow heart rhythm with a rate below 60 beats per minute.
• Supraventricular arrhythmias –  Arrhythmias that begin in the atria (the heart’s upper chambers). “Supra” means above; “ventricular” refers to the lower chambers of the heart or ventricles.
• Ventricular arrhythmias – Arrhythmias that begin in the ventricles (the heart’s lower chambers).
• Bradyarrhythmias – Slow heart rhythms that may be caused by disease in the heart’s conduction system, such as the sinoatrial (SA) node, atrioventricular (AV) node or HIS-Purkinje network.

Atrial Arrhythmia

• Sinus bradycardia
• Premature atrial contractions (PACs)
• Wandering atrial pacemaker
• Atrial tachycardia
• Multifocal atrial tachycardia
• Supraventricular tachycardia (SVT)
• Atrial flutter
• Atrial fibrillation (Afib)
• AV nodal reentrant tachycardia

Junctional Arrhythmias

• AV nodal reentrant tachycardia
• Junctional rhythm
• Junctional tachycardia
• Premature junctional contraction

Ventricular Arrhythmia

• Premature ventricular contractions (PVCs), sometimes called ventricular extra beats (VEBs)
  • Premature ventricular beats occurring after every normal beat are termed ventricular bigeminy
  • PVCs that occur at intervals of 2 normal beats to 1 PVC are termed “PVCs in trigeminy”
  • Three premature ventricular grouped together is termed a “run of PVCs” in general, runs lasting longer than three beats with an increased heart rate are referred to as ventricular tachycardia
• Accelerated idioventricular rhythm
• Monomorphic ventricular tachycardia
• Polymorphic ventricular tachycardia
• Ventricular fibrillation
• Torsades de pointes
• Arrhythmogenic right ventricular dysplasia
• Re-entry ventricular arrhythmia

Heart blocks

These are also known as AV blocks because the vast majority of them arise from pathology at the atrioventricular node. They are the most common causes of bradycardia:

• First-degree heart block –  which manifests as PR prolongation
• Second-degree heart block – Type 1 Second degree heart block, also known as Mobitz I or Wenckebach. Type 2 Second degree heart block, also known as Mobitz II
• Third-degree heart block – also known as complete heart block.

First, the second and third-degree block also can occur at the level of the sinoatrial junction. This is referred to as sinoatrial block typically manifesting with various degrees and patterns of sinus bradycardia.

The American Heart Association and American College of Cardiology further classified AF as follows:[rx]

• Paroxysmal AF – intermittent in nature, terminating spontaneously or within 7 days of treatment
• Persistent AF – Failure to terminate in 7 days
• Long-lasting AF – AF lasting for more than 12 months
• Permanent AF – Persistent AF where rhythm strategy is no longer pursued

Other Types of AF

• Lone AF – Lone AF is used to describe patients younger than 60 years with no other concomitant heart disease and structurally normal heart on an echocardiogram.
• Non-Valvular AF – Defines whether AF is related to valvular disease, replacement or repair. It is much more difficult to convert valvular AF into sinus rhythm.

Causes of Arrhythmia

The etiology of reentry is diverse and includes:

• Electrolyte abnormalities and channelopathies form a substrate for reentry arrhythmias.
• A mechanical force such as the chest thump maneuver induces but also terminates reentry.[4]
• Chronic cardiac stretch leads to remodeling and fibrosis that changes the electrical properties of the myocardiocytes.
• Scar tissue following infarction is the basis of anatomical reentry.
• Congenital heart disease and surgery performed to treat it can cause reentry.
• Genetic culprits are related to reentry tachycardias. Roberts et al. identified genetic culprits SCN5A and LMNA as a cause of idiopathic bundle branch reentry ventricular tachycardia.[5]

Cardiac Causes

• Hypertensive heart disease
• Coronary artery disease
• Valvular heart disease
• Heart failure
• Congenital heart disease
• Cardiomyopathy
• Infiltrative cardiac disease
• Sick sinus syndrome
• pre-excitation syndrome

Non-Cardiac Causes

• Chronic lung disease
• Pulmonary embolism
• Electrolyte abnormalities
• Acute infections
• Thyroid disorders
• Pheochromocytoma
• Hypothermia
• Post-surgical (seen in 35% to 50% of patients post coronary artery bypass graft)[3]

A number of factors can cause the heart to work incorrectly, they include

• alcohol abuse
• diabetes
• drug abuse
• excessive coffee consumption
• heart disease like congestive heart failure
• hypertension (high blood pressure)
• hyperthyroidism (an overactive thyroid gland)
• mental stress
• scarring of the heart, often the result of a heart attack
• smoking
• some dietary supplements
• some herbal treatments
• some medications
• structural changes in the heart

Others

• Age-related fibrosis
• Diabetes
• Obesity
• Metabolic syndrome
• Obstructive sleep apnea
• Chronic kidney disease
• High-intensity exercise
• Genetic factors
• Sinus tachycardia
• Atrial flutter
• Atrial flutter with variable block
• Atrial tachycardia (AT)
• Multifocal atrial tachycardia (MAT)
• Wolff-Parkinson-White syndrome (WPW)
• Atrioventricular nodal reentry tachycardia (AVNRT)
• Atrioventricular reentry tachycardia (AVRT)
• Junctional ectopic tachycardia

Symptoms of Arrhythmia

• The most common symptom of arrhythmia – is an awareness of an abnormal heartbeat, called palpitations. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though distracting for patients) but some of them predispose to adverse outcomes.
• Higher risk of blood clotting – within the heart and a higher risk of insufficient blood being transported to the heart because of a weak heartbeat. Other increased risks are of embolization and stroke, heart failure and sudden cardiac death.
• If an arrhythmia results in a heartbeat that is too fast – too slow or too weak to supply the body’s needs, this manifests as lower blood pressure and may cause lightheadedness or dizziness, or syncope (fainting).
• Cardiac arrest or sudden death.
• Abnormality using an electrocardiogram is one way to diagnose and assess the risk of any given arrhythmia.

Symptoms of Tachycardia

Tachycardia is when the heart beats quicker than normal; symptoms include

• Breathlessness (dyspnea)
• Dizziness
• Syncope (fainting, or nearly fainting)
• Fluttering in the chest
• Chest pain
• Lightheadedness
• Sudden weakness

Symptoms of Bradycardia

Bradycardia is when the heart beats slower than normal; symptoms include

• Angina (chest pain)
• Trouble concentrating
• Confusion
• Difficulties when exercising
• Dizziness
• Fatigue (tiredness)
• Lightheadedness
• Palpitations
• Shortness of breath
• Syncope (fainting or nearly fainting)
• Diaphoresis, or sweating

Symptoms of atrial fibrillation

• Angina (chest pain)
• Breathlessness (dyspnea)
• Dizziness
• Palpitations
• Syncope (fainting, or nearly fainting)
• Weakness

Diagnosis of Arrhythmia

The following tests might be ordered

• Blood and urine tests
• EKG (electrocardiogram)
• Holter monitor – a wearable device that records the heart for 1-2 days
• Echocardiogram
• Electrophysiologic testing (or EP studies)
• Heart catheterization
• The absence of distinct “P” waves
• Irregularly irregular R-R interval.
• Narrow QRS complex tachycardia –  typically with the heart rate between 110 and 160; QRS duration fewer than 0.12 seconds unless accompanied by pre-existing bundle block, aberrant conduction, or accessory pathway
• Fibrillatory waves – may be present which can mimic “P” waves.
• Ashman phenomenon – QRS morphology is usually unaffected in AF, however, in cases with aberrant ventricular conduction bundle branch block can occur as a result of an abrupt change in length of the cardiac cycle. These aberrantly conducted beats are usually of right bundle branch block morphology.[rx]
• Patients should be tested for electrolyte abnormalities – endocrine disorders (specifically hyperthyroid) drug-induced causes, infections, drug or chemical withdrawal, and echocardiography to check for structural heart disease. In patients presenting with ischemic stroke and with no prior history of AF, 72-hour Holter monitoring improves the detection rate of silent paroxysmal.[rx]
• Magnetic resonance imaging (MRI) – A cardiac MRI can provide still or moving pictures of how the blood is flowing through the heart and detect irregularities.
• Computerized tomography (CT) – CT scans combine several X-ray images to provide a more detailed cross-sectional view of the heart.
• Coronary angiogram – To study the flow of blood through your heart and blood vessels, your doctor may use a coronary angiogram to reveal potential blockages or abnormalities. It uses a dye and special X-rays to show the inside of your coronary arteries.
• Chest X-ray – This test is used to take still pictures of your heart and lungs and can detect if your heart is enlarged.
• Stress Test – Your doctor may recommend a stress test to see how your heart functions while it is working hard during exercise or when medication is given to make it beat fast. In an exercise stress test, electrodes are placed on your chest to monitor heart function while you exercise, usually by walking on a treadmill. Other heart tests may also be performed in conjunction with a stress test.
• Additional Tests -Your doctor may order additional tests as needed to diagnose an underlying condition that is contributing to tachycardia and judge the condition of your heart.
• Electrophysiological Testing (EP Studies) – This is an invasive, relatively painless, non-surgical test and can help determine the type of arrhythmia, its origin, and potential response to treatment. The test is carried out in an EP lab by an electrophysiologist and makes it possible to reproduce troubling arrhythmias in a controlled setting.
• Tilt-Table Test – If an individual experiences fainting spells, dizziness, or lightheadedness, and neither the ECG nor the Holter revealed any arrhythmias, a tilt-table test might be performed. This monitors blood pressure, heart rhythm, and heart rate while they are moved from a lying to an upright position. When reflexes work correctly, they cause the heart rate and blood pressure to change when moved to an upright position. This is to make sure the brain gets an adequate supply of blood.
• LINQ insertable cardiac monitor – This wireless, powerful, small insertable cardiac monitor is ideal for patients experiencing infrequent symptoms that require long-term monitoring or ongoing management.
• Exercise test – Your doctor might monitor your heart rate while you walk on a treadmill or ride a stationary bike to see whether your heart rate increases appropriately in response to physical activity.
• A stress test – can be helpful in bringing out either sinus node disease or heart block that becomes apparent only during exertion.

Event Recorder – This device is similar to a Holter monitor, but it does not record all the heartbeats. There are two types:

• One type – uses a phone to transmit signals from the recorder while the person is experiencing symptoms.
• The other type – is worn all the time for a long time. These can sometimes be worn for as long as a month.
  This event recorder is good for diagnosing rhythm disturbances that happen at random moments.

A variety of drugs are available to treat arrhythmias. These include

• Antiarrhythmic drugs – These drugs control heart rate and include beta-blockers.
• Anticoagulant or antiplatelet therapy – These drugs reduce the risk of blood clots and stroke. These include warfarin (a “blood thinner”) or aspirin. Another blood thinner called Pradaxa (dabigatran) was approved in 2010 to prevent stroke in people with atrial fibrillation.
• Oral β-blocker – diltiazem or verapamil treatment is useful for ongoing management in patients with symptomatic SVT who do not have ventricular pre-excitation during sinus rhythm (class I recommendation, level B-R evidence)
• Electrophysiologic study – with the option of radiofrequency catheter ablation is useful for the diagnosis and potential treatment of SVT (class I recommendation, level B-NR evidence)
• Patients with SVT – should be educated on how to perform vagal maneuvers for ongoing management of SVT (class I recommendation, level C-LD evidence)
• Intravenous administration of diltiazem – or verapamil can be effective for acute treatment in patients with hemodynamically stable SVT (class IIa recommendation, level B-R evidence)
• Cardioversion – the doctor may use an electric shock or medication to reset the heart to its regular rhythm.
• Ablation therapy – one or more catheters go through blood vessels into the inner heart. They are placed in areas of the heart that are thought to be the source of the arrhythmia and destroy small sections of those tissues.
• Implantable cardioverter-defibrillator – the device is implanted near the left collarbone and monitors heart rhythm; if it detects an abnormally fast rhythm, it stimulates the heart to return to a normal rhythm.
• Maze procedure – a series of surgical incisions are made in the heart. They then heal into scars and form blocks. These blocks guide the electrical impulses, helping the heart to beat efficiently.

Surgery

• Ventricular aneurysm surgery – sometimes, an aneurysm (bulge) in a blood vessel that leads to the heart causes an arrhythmia. If other treatments do not work, a surgeon may remove the aneurysm.
• Coronary bypass surgery – arteries or veins from elsewhere in the patient’s body are grafted to the coronary arteries to bypass any regions that have become narrow, and improve the blood supply to the heart muscle (myocardium).

Additional Rx

• Control of Ventricular Response – The conventional use of digitalis for acute control of ventricular rate in a patient presenting with atrial fibrillation and the rapid ventricular response has become obsolete with the introduction of intravenous beta-blockers, verapamil, and diltiazem.
• Anticoagulation is the 1st requirement – regardless of whether acute, late, or no conversion to sinus rhythm is contemplated. In the acute situation, the administration of intravenous heparin—or of subcutaneous enoxaparin or dalteparin in combination with Coumadin or aspirin (or both)—are recommended strategies, while a decision is being made about the timing of conversion to sinus rhythm. Restoration of sinus rhythm by any method, whether electrical or pharmacologic, should be delayed until the patient has been given the best possible protection from systemic embolism.
• Electrical cardioversion – should always be performed under brief general anesthesia, administered by competent personnel in a well-oxygenated patient who is hemodynamically and medically stable, to the degree possible.
• Medical cardioversion – with intravenous or oral antiarrhythmic drugs has a lower acute success rate than electrical cardioversion. Whether medical cardioversion will be shown to be safer than electrical cardioversion is an interesting question. Theoretically, the proarrhythmic effects of antiarrhythmic drugs might be offset by less of a mechanical stunning effect on the atria. It is now well-established that the class III drug ibutilide can effectively restore sinus rhythm, especially in atrial fibrillation or flutter of short duration (hours), with an acceptably low risk of torsades de pointes in properly selected patients. ^[rx] Other oral regimens, such as high-dose propafenone, quinidine, and flecainide, have been reported. ^[rx,rx]
• Dual-site atrial pacing has been reported to have the following short-term effects – shortening of P wave duration and interatrial conduction time; diminished dispersion of atrial refractoriness; less functional delay during atrial extra stimulation; and lower inducibility of atrial fibrillation. ^[rx]
• Pacemaker Therapy – Of the many exciting developments in the management of atrial fibrillation, one of the most promising is the present investigation of various pacing techniques for the prevention of atrial fibrillation.
• Ablation or Modification of Atrioventricular Conduction – For nearly 20 years, interruption of A-V conduction by high-energy shock and more recently by radiofrequency energy has been a procedure of last resort in selected patients with persistent or permanent atrial fibrillation in whom ventricular rate has not been controllable by double or triple therapy with A-V nodal blocking agents or amiodarone. ^[rx]
• Surgical Ablation of Atrial Fibrillation – The pioneering work of Cox and colleagues in mapping human atrial flutter and in developing a series of “maze” operations to eliminate atrial fibrillation has led to very impressive long-term cure of the arrhythmia with substantial restoration of right and (usually) left atrial transport function and the possibility of discontinuation of anticoagulation in selected patients with idiopathic, medically refractory atrial fibrillation. ^[rx]
• Ablation of Atypical (Non-Classical) Atrial Flutter – Flutters that do not conform to the foregoing electrocardiographic patterns are designated atypical flutters. Although these can occur in the absence of structural heart disease, they seem to be much more prevalent in patients with congenital or acquired heart diseases or in patients in whom previous ablation procedures have been performed in the atria. Circuits have been described crossing the crista terminalis, circulating around atrial septal defects, around a septal defect patch, around atriotomy scars, and around the pulmonary veins.

Implantable Cardioverter Defibrillator (ICD)

Doctors mainly use ICDs to treat ventricular tachycardia and ventricular fibrillation, two life-threatening heart rhythms.

The ICD constantly tracks the heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers an electric shock to the heart muscle to cause the heart to beat in a normal rhythm again. There are several ways the ICD can be used to restore normal heart rhythm. They include:

• Anti-tachycardia pacing (ATP). When the heart beats too fast, you get a series of small electrical impulses to the heart muscle to restore a normal heart rate and rhythm.
• Cardioversion. You may get a low-energy shock at the same time as the heart beats to restore normal heart rhythm.
• Defibrillation. When the heart is beating dangerously fast or irregularly, the heart muscle gets a higher-energy shock to restore a normal rhythm.
• Anti-bradycardia pacing. Many ICDs provide back-up pacing to maintain heart rhythm if it slows too much.

Complications

Complications associated with AF include [rx]

• Thromboembolism including stroke
• New-onset heart failure or worsening of existing heart failure
• Acute myocardial infarction
• Hemodynamic instability leading to cardiogenic shock
• Sudden death from Wolff-Parkinson-White syndrome
• Tachycardia-induced cardiomyopathy

Prevention

To prevent heart arrhythmia, it’s important to live a heart-healthy lifestyle to reduce your risk of heart disease. A heart-healthy lifestyle may include:

• Eating a heart-healthy diet
• Increasing your physical activity
• Avoiding smoking
• Keeping a healthy weight
• Limiting or avoiding caffeine and alcohol
• Reducing stress, as intense stress and anger can cause heart rhythm problems
• Using over-the-counter medications with caution, as some cold and cough medications contain stimulants that may trigger a rapid heartbeat

Living with Arrhythmias

Taking medications

• Take all medications exactly as prescribed.
• Never stop taking any prescription medication without first consulting your healthcare provider.
• If you have any side effects, tell your healthcare provider about them.
• Tell your healthcare provider about all your other drugs and supplements, including over-the-counter medications and vitamins.

Monitor your pulse

You should know how to take your pulse – especially if you have an artificial pacemaker.

• Put the second and third fingers of one hand on the inside of the wrist of the other hand, just below the thumb OR on the side of your neck, just below the corner of your jaw.
• Feel for the pulse.
• Count the number of beats in one full minute.
• Keep a record of your pulse along with the day and time took and notes about how you felt at the time.

Certain substances can contribute to an abnormal/irregular heartbeat, including

• Caffeine
• Tobacco
• Alcohol
• Cold and cough medications
• Appetite suppressants
• Psychotropic drugs (used to treat certain mental illnesses)
• Antiarrhythmics (paradoxically, the same drugs used to treat arrhythmia can also cause arrhythmia. Your healthcare team will monitor you carefully if you’re taking antiarrhythmic medication.)
• Beta-blockers for high blood pressure
• Street drugs such as cocaine, marijuana and “speed” or methamphetamines

If you’re being treated for arrhythmia and use any of these substances, be sure to discuss this with your doctor.

References

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