Rhythms of the Heart: Demystifying Common Types of Heart Arrhythmia

Heart arrhythmias, or irregular heart rhythms, occur when the heart's electrical system malfunctions, causing it to beat too fast, slow, or irregularly. Understanding the different types of arrhythmias is crucial because they can vary widely in severity and impact on a person's health. These conditions are more prevalent than one might think, with millions of people worldwide affected. The importance of early detection and treatment cannot be overstated, as untreated arrhythmias can lead to serious complications, including heart failure, stroke, and even sudden cardiac arrest. Therefore, regular check-ups and monitoring are essential to identify and manage arrhythmias promptly, ultimately improving patients' quality of life and reducing the risk of life-threatening events. (24) 

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What Is a Heart Arrhythmia?

A healthy adult's heart normally beats 60-100 times per minute in a regular, coordinated pattern. Each beat originates from electrical signals that travel through the heart's specialized conduction system. These signals control the timing and sequence of cardiac muscle contractions that pump blood through the body. A heart arrhythmia, also known simply as an arrhythmia, is a medical condition characterized by an abnormal rhythm or irregular heartbeat. (32) 

The electrical impulses that initiate each heartbeat originate in a small cluster of cells called the sinoatrial (SA) node, located in the heart's right atrium. The SA node is often called the "natural pacemaker" of the heart because it generates electrical signals spontaneously. The electrical impulse travels through specialized pathways in the atria (the heart's upper chambers), causing the atria to contract and push blood into the ventricles. It then reaches the atrioventricular (AV) node in the wall between the atria. The AV node acts as a gateway, slowing down the electrical signal to allow the ventricles enough time to fill with blood from the atria. After passing through the AV node, the electrical signal travels down a bundle of specialized fibers called the bundle of His. This bundle divides into the right and left branches, extending down the septum toward the bottom of the heart. The bundle branches further split into smaller fibers known as Purkinje fibers, by which the electrical signal rapidly spreads, causing the ventricles to contract and pump oxygenated blood into the pulmonary artery and aorta. In an arrhythmia, there is a disturbance in this regular electrical activity, leading to irregular heartbeats. (4) 

Source: Johns Hopkins Medicine

Arrhythmias can result from a variety of causes, including heart disease, high blood pressure, electrolyte imbalances, heart attacks, congenital heart defects or other changes to the heart's structure, diabetes, thyroid disease, COVID-19 infection, sleep apnea, certain medications, stimulants like caffeine or drugs, genetics, and stress.

Some arrhythmias may not cause noticeable symptoms and are only detected during medical exams or monitoring. Other arrhythmias can cause palpitations and decrease the blood flow to the brain and other vital body tissues, leading to dizziness, shortness of breath, chest pain, or fainting. More severe arrhythmias can increase the risk of blood clots, stroke, heart failure, and sudden death. (6, 32) 

Common Types of Heart Arrhythmia

There are many types of arrhythmias, classified by what part of the heart (i.e., atria, ventricles) is affected and whether they cause a slow (bradycardia), fast (tachycardia), or irregular heart rate.

Atrial Fibrillation (AFib) 

AFib is one of the most common types of arrhythmia, affecting more than two million American adults. The main hallmark of AFib is the disorganized electrical activity in the atria, causing the atria to fibrillate or quiver, leading to an irregular and rapid heartbeat. A fluttering heartbeat is the most common symptom of AFib. Other symptoms include fatigue, dizziness, shortness of breath, weakness, and chest pain. (10, 47) 

Age is a significant risk factor for AFib. The risk for AFib increases as you get older; it rarely occurs in children. Other risk factors include family history and genetics, alcohol and illegal drugs, smoking, emotional stress, preexisting heart or lung disease, and sleeping disorders. (8) 

Treatment options for AFib aim to control the heart's rhythm and rate. This may involve lifestyle changes, medications, and surgical procedures. Stroke prevention is critical to AFib management because individuals with AFib have a significantly higher risk of stroke. Blood thinners or direct oral anticoagulants (DOACs) are often prescribed to reduce this risk by preventing the formation of blood clots in the atria. (9) 

Ventricular Tachycardia (VT)

VT is a serious cardiac arrhythmia characterized by a rapid and regular heartbeat originating in the heart's ventricles. In VT, the heart beats significantly faster than normal, exceeding 100 beats per minute. This rapid and sustained rhythm can disrupt the heart's normal pumping function, potentially leading to severe complications, including inadequate blood circulation, fainting, and, in some cases, cardiac arrest. Sudden cardiac deaths caused by VT account for approximately half of cardiovascular-related deaths. (30)

The most common cause of ventricular tachycardia is underlying ischemic heart disease; around 15% of patients with coronary artery disease also have VT. Other causes include structural heart disease, electrolyte imbalances, and illicit drug use. (30) 

VT can manifest with a range of symptoms, from palpitations and chest discomfort to dizziness, lightheadedness, and loss of consciousness. The severity of these symptoms often depends on factors like the duration and rate of the arrhythmia and the patient's overall health. VT can occur as an isolated event or as part of a broader cardiac condition, such as heart disease, heart attack, or cardiomyopathy. When VT persists, it can degenerate into ventricular fibrillation (VFib), a life-threatening arrhythmia characterized by chaotic electrical activity in the ventricles, leading to a loss of effective cardiac pumping and sudden cardiac arrest. Prompt medical evaluation and treatment are crucial for individuals with VT to prevent these potentially fatal outcomes. Treatment strategies may include anti-arrhythmic medications, implantable cardioverter-defibrillators (ICDs) to deliver electrical shocks to restore normal rhythm, and addressing underlying heart conditions if present. (30)

Bradycardia 

Bradycardia is a medical condition characterized by an unusually slow heart rate of fewer than 60 beats per minute. It can occur due to various causes, including age-related changes in the heart's electrical system, certain medications like beta-blockers, heart diseases like coronary artery disease or heart attack, and certain medical conditions like hypothyroidism. In some cases, bradycardia may be congenital (present from birth). (13, 14)

Symptoms of bradycardia can vary depending on the severity of the condition. Mild cases may not produce noticeable symptoms, while more severe bradycardia can lead to fatigue, dizziness, lightheadedness, shortness of breath, chest pain, and fainting due to insufficient blood flow to the brain. If you or someone you know experiences these symptoms, especially if they are recurrent or severe, it's essential to seek medical attention promptly. Bradycardia can sometimes lead to serious complications, including reduced blood flow to vital organs, an increased risk of falls or accidents, heart failure, and sudden death. (13, 14)

Treatment options for bradycardia depend on the underlying cause and the severity of symptoms. In cases where bradycardia is due to a reversible cause, addressing that cause, such as adjusting medications or treating an underlying medical condition, may be sufficient. However, for persistent or severe bradycardia, a pacemaker may be recommended as an effective means of management and improving the quality of life for individuals with this condition. (13, 14)

Supraventricular Tachycardia (SVT)

SVT is characterized by episodes of rapid heartbeat originating above the heart's ventricles. SVT encompasses many arrhythmias, including premature atrial contractions, atrial tachycardia, AFib, and atrial flutter. It has an incidence rate of 2.29 per 1,000 people and can occur in people of all ages. (42, 45)

SVT episodes can range from brief and infrequent to prolonged and frequent occurrences. Symptoms of SVT often include a sudden and rapid heartbeat, palpitations, chest discomfort or pain, dizziness, lightheadedness, and sometimes fainting. Triggers for SVT episodes can vary among individuals but commonly include stress, caffeine consumption, alcohol, tobacco use, and certain medications. (42, 45)

SVT can be diagnosed with an electrocardiogram or heart monitor, which both record the heart's electrical activity. Treatment options aim to restore a normal heart rhythm, including vagal maneuvers (simple exercises that stimulate the vagus nerve), medications, or more invasive procedures like catheter ablation. Lifestyle modifications are also important in managing SVT and often involve avoiding or minimizing triggers, adopting stress-reduction techniques, and making healthy lifestyle choices such as regular exercise and a heart-healthy diet. (42, 45)

Atrial Flutter 

Atrial flutter is a cardiac arrhythmia characterized by a rapid and regular heartbeat originating in the atria. During atrial flutter, the atrium can beat up to 300 times a minute, resulting in a pulse rate of around 150 beats per minute (12). While similar in some ways to AFib, atrial flutter is less common and differs because the abnormal electrical signals in the atria follow a more organized and regular pattern. Despite this distinction, atrial flutter and AFib can result in similar complications, including an increased risk of stroke and other heart-related issues. (3) 

Common symptoms of atrial flutter may include palpitations, a sensation of rapid, pounding heartbeat, shortness of breath, fatigue, and chest discomfort. Risk factors for developing atrial flutter include advanced age and preexisting cardiopulmonary disease. Treatment for atrial flutter aims to treat tachycardia, convert to and maintain a normal sinus rhythm, and reduce the risk of stroke. This is achieved by using antiarrhythmic and blood-thinning medications. Electrical cardioversion and catheter ablation may also be recommended to convert atrial flutter to normal sinus rhythm. (12)

Premature Ventricular Contractions (PVCs) 

PVCs are extra heartbeats initiated by the Purkinje fibers in the ventricles, creating a sensation of a skipped heartbeat followed by a fluttering feeling. They are common and have been detected in 75% of healthy individuals through Holter heart monitoring. They can affect people of all ages and are often considered benign, especially when they occur infrequently. (43)  

Various factors, including stress, anxiety, caffeine, alcohol, tobacco use, certain medications, and underlying heart conditions, can cause PVCs. For most people, occasional PVCs are not concerning. However, if PVCs cooccur with preexisting disease, become more frequent and prolonged, or are associated with symptoms such as chest pain, dizziness, or fainting, they should prompt medical evaluation. Treatment options for PVCs may include lifestyle modifications like reducing stress, caffeine, and alcohol intake and medications to suppress PVCs or treat underlying heart conditions if present. Catheter ablation may be considered for individuals with frequent or complex PVCs that significantly impact their quality of life. (28, 43) 

Diagnosis and Monitoring 

Accurate diagnosis and vigilant monitoring of arrhythmias form the cornerstone of effective patient care and the prevention of potential complications.

Diagnostic Tests For Heart Arrhythmia

An electrocardiogram (EKG or ECG) is the most common test for diagnosing arrhythmias. It can be performed on a patient at rest or during a stress test. It records the heart's electrical activity to determine how long electrical impulses pass through the heart and if parts of the heart are damaged.

Holter monitors are small, portable EKGs that continuously monitor the heart's electrical activity over a 24-to-48-hour period. Because abnormal heart rhythms may come and go, and EKGs only record the heart's activity at a single point, Holter monitors provide the advantage of prolonged monitoring to evaluate the heart over a more extended period. Patients are often asked to keep a diary of their activities and symptoms while wearing the monitor so that their doctor can compare how symptoms correspond to the heart's rate and rhythm. 

A cardiac event recorder is similar to a Holter monitor and is generally recommended when patients experience infrequent symptoms. There are various types of event recorders, most of which require activation (by pushing a button) when the patient experiences a symptomatic episode.

Electrophysiology testing, also called an EP study, is a procedure performed under local anesthesia during which temporary electrode catheters are threaded into and positioned in the heart to record and map the path of electrical signals and impulses during each heartbeat. 

Identifying Underlying Causes of Arrhythmias

Your doctor may also recommend various blood tests to help determine the underlying cause of your arrhythmia. Standard blood tests ordered during an arrhythmia evaluation include:

Complete Blood Count (CBC)

Anemia, most frequently caused by iron deficiency, is common in patients with arrhythmia and other cardiac conditions. Patients with co-existing cardiac conditions and (iron deficiency) anemia also have poorer clinical outcomes. (31) A CBC, which measures the levels of red blood cells, hemoglobin, and hematocrit in circulation to diagnose anemia, is an important blood test to order in evaluating arrhythmia to identify the underlying cause and determine prognosis. 

Thyroid Panel

Tachycardia is noted in almost all patients with hyperthyroidism. The risk of AFib increases sixfold in the presence of overt hyperthyroidism. Conversely, bradycardia is common in patients with hypothyroidism. (37) A thyroid panel is the diagnostic test of choice for thyroid diseases.

Electrolyte Panel

Electrolytes, including potassium, sodium, calcium, and magnesium, help trigger and send electrical impulses in the heart. Imbalances in these nutrients, whether they be too high or too low, can interfere with heart signaling and contraction, leading to arrhythmia. Disturbances in the balance of potassium account for the majority of clinical arrhythmias. (29) 

Cardiovascular Risk Assessment

Because underlying heart disease increases the risk of developing an arrhythmia, and vice versa, a comprehensive cardiovascular assessment is advised to evaluate the general health status of a patient's cardiovascular system. Various cardiovascular tests are available to evaluate heart and blood vessel health and assess disease risk, including an advanced lipid panel, hs-CRP, homocysteine, vitamin D, and HbA1c. Your doctor may also recommend genetic testing, including the MTFHR and 4q25 genes, to identify genetic variants predisposing an individual to atherosclerotic cardiovascular disease and certain arrhythmias.

The Importance of Regular Check-Ups and Monitoring 

Regular check-ups and monitoring are crucial for individuals with arrhythmias for several reasons. Firstly, arrhythmias may not produce noticeable symptoms, especially in their early stages. Regular check-ups can detect arrhythmias even before symptoms arise, enabling prompt treatment. Secondly, these check-ups allow healthcare providers to assess the severity and risk associated with an arrhythmia. Studies have determined that having an arrhythmia, especially tachycardia or PVCs, increases a person's risk of cardiovascular disease, stroke, and heart failure. Early diagnosis of arrhythmia and quickly identifying changes in the arrhythmia's pattern or severity improves health outcomes by ensuring timely interventions and effective care are provided to prevent health complications.

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Treatment Options 

Treatment for arrhythmias depends on their severity and the underlying cause. Some arrhythmias may not require treatment if they are benign and do not cause symptoms. Others may be managed with medications, lifestyle changes, or procedures like cardioversion, catheter ablation, or the implantation of devices to regulate the heart's rhythm and prevent life-threatening arrhythmias. The specific treatment approach is determined by a healthcare provider based on the individual's medical history and the nature of the arrhythmia.

Medications 

Antiarrhythmic medications act on the heart's various electrical channels to reset the heart to a normal sinus rhythm and prevent future arrhythmic episodes. There are four main classes of antiarrhythmics:

• Class I (Sodium Channel Blockers) prevent sodium from getting through cell membranes to slow electrical impulses in the heart muscle
• Class II (Beta Blockers) slow heart rate by blocking the effects of catecholamines (epinephrine and norepinephrine) 
• Class III (Potassium Channel Blockers) prevent potassium from crossing cell membranes, slowing electrical impulses in cardiac cells
• Class IV (Calcium Channel Blockers) block calcium channels in the heart, decreasing heart rate and contractions

Anticoagulants (blood thinners) are prescribed for patients with a higher risk of forming blood clots, such as those with AFib. By making it harder for the blood to clot, anticoagulants are used in preventing stroke occurrence. 

Cardioversion 

Cardioversion is a medical procedure used to restore a normal heart rhythm in individuals with certain types of abnormal heart rhythms or arrhythmias. There are two main types of cardioversion.

In electrical cardioversion, an electric shock is delivered to the heart through special electrodes placed on the chest. This shock is synchronized with the heart's electrical activity and is intended to momentarily interrupt the abnormal rhythm. The brief interruption allows the heart's SA node to regain control and reestablish a normal heart rhythm. Electrical cardioversion is commonly used for arrhythmias such as AFib, atrial flutter, and certain ventricular arrhythmias. (25) 

Chemical or pharmacological cardioversion involves using medications, typically antiarrhythmic drugs, to restore a normal heart rhythm. Chemical cardioversion is often used for less severe arrhythmias or when electrical cardioversion is not advisable due to patient factors or other considerations. (18) 

Catheter Ablation 

Catheter ablation is a medical procedure performed under anesthesia to treat certain heart arrhythmias by modifying or destroying the abnormal heart tissue responsible for irregular electrical signals. It is often recommended when medications fail to effectively control or manage the arrhythmia or when the side effects of medications become problematic.

Implantable Devices

Pacemakers are small, implantable devices placed under the chest's skin, typically just below the collarbone. Pacemakers send electrical impulses to the heart to stimulate contractions and maintain a normal heart rate. They can ensure that the heart beats at a steady rate and help prevent symptoms like dizziness, fatigue, and fainting.

Implantable cardioverter-defibrillators (ICDs) are similar in size and placement to pacemakers but serve a different purpose. They are used to treat life-threatening ventricular arrhythmias, such as VT and VFib, which can lead to sudden cardiac arrest. ICDs continuously monitor the heart's rhythm, and if they detect a dangerous arrhythmia, they can deliver a high-energy shock ("defibrillation") to restore a normal heartbeat.

Lifestyle Modifications

Lifestyle changes can help prevent heart arrhythmias and reduce the overall risk of heart disease. A heart-healthy lifestyle includes eating a heart-healthy diet, staying physically active, maintaining a healthy weight, not smoking, limiting consumption of alcohol, getting adequate sleep, and reducing stress.

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Summary

Heart arrhythmias are irregular heart rhythms that can significantly impact cardiac health. Diagnosing these arrhythmias often involves tests such as EKGs, Holter monitoring, EP studies, and bloodwork. Treatment options vary based on the specific arrhythmia: AFib and atrial flutter may be managed with medications to control heart rate and rhythm, catheter ablation to correct abnormal electrical pathways, and blood thinners to reduce stroke risk; VT may require antiarrhythmic drugs or ICDs for life-threatening cases; and bradycardia often calls for pacemakers to maintain a healthy heart rate. Tailoring the approach to each patient's condition is crucial for effectively managing heart arrhythmias and improving overall cardiac health.