Tachyarrhythmias

A tachyarrhythmia is a rapid heart rhythm, regular or irregular, with a rate > 100 beats/min. Tachyarrhythmia may or may not be accompanied by symptoms of hemodynamic change. Pathologic tachyarrhythmias resulting in hemodynamic instability can be caused by intrinsic cardiac abnormalities, systemic diseases, or medication toxicity. Supraventricular arrhythmias are called narrow-complex tachycardias and originate in the sinoatrial (SA) node, atrial myocardium, or atrioventricular (AV) node. Ventricular arrhythmias originate below the AV node and are characterized by a wide QRS complex. Diagnosis is made by physical exam and ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG). Management is directed toward the type of tachyarrhythmia present and its underlying cause.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

A tachyarrhythmia is a rapid heart rhythm, regular or irregular, with a rate > 100 beats/min.

Classification

Narrow QRS complex (< 120 msec) tachycardia: 

  • Usually seen with supraventricular tachycardias
  • May originate in the sinus node, the atria, the atrioventricular (AV) node, the His bundle, or some combination of these
  • Regular rhythm: 
    • Sinus tachycardia
    • Sinoatrial (SA) or AV nodal reentrant tachycardia (AVNRT)
    • Paroxysmal supraventricular tachycardia Supraventricular tachycardia Supraventricular tachycardias are related disorders in which the elevation in heart rate is driven by pathophysiology in the atria. This group falls under the larger umbrella of tachyarrhythmias and includes paroxysmal supraventricular tachycardias (PSVTs), ventricular pre-excitation syndromes (i.e. Wolff-Parkinson-White syndrome), atrial flutter, multifocal atrial tachycardia, and atrial fibrillation. Supraventricular Tachycardias (SVT)
    • Atrial flutter
  • Irregular rhythm: 
    • Atrial fibrillation
    • Multifocal atrial tachycardia

Wide QRS complex (≥ 120 msec) tachycardia: 

  • Most commonly originates below the His bundle or in the ventricles:
    • Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia: may be stable or unstable
    • Pulseless ventricular tachycardia: treated the same as ventricular fibrillation Ventricular fibrillation Ventricular fibrillation (VF or V-fib) is a type of ventricular tachyarrhythmia (> 300/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular Fibrillation
  • Can still originate in supraventricular structures if there is a His-Purkinje abnormality (aberrancy) or if conduction occurs over an accessory pathway

Etiology

  • Primary cardiac disease:
    • Coronary artery disease (most common):
      • Ischemia
      • MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
    • Structural disease:
      • Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure
      • Cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Overview of Cardiomyopathies
      • Myocarditis Myocarditis Myocarditis is an inflammatory disease of the myocardium, which may occur alone or in association with a systemic process. There are numerous etiologies of myocarditis, but all lead to inflammation and myocyte injury, most often leading to signs and symptoms of heart failure. Myocarditis
  • Congenital disorders:
    • Long-QT syndrome
    • Wolff-Parkinson-White syndrome (WPW)
    • Inherited channelopathies
  • Metabolic causes:
    • Electrolyte disturbances:
      • Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia (paroxysmal atrial tachycardia (PAT), AV block AV block Atrioventricular (AV) block is a bradyarrhythmia caused by delay, or interruption, in the electrical conduction between the atria and the ventricles. Atrioventricular block occurs due to either anatomic or functional impairment, and is classified into 3 types. Atrioventricular Block, ventricular tachycardia or ventricular fibrillation Ventricular fibrillation Ventricular fibrillation (VF or V-fib) is a type of ventricular tachyarrhythmia (> 300/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular Fibrillation)
      • Hyperkalemia Hyperkalemia Hyperkalemia is defined as a serum potassium (K+) concentration >5.2 mEq/L. Homeostatic mechanisms maintain the serum K+ concentration between 3.5 and 5.2 mEq/L, despite marked variation in dietary intake. Hyperkalemia can be due to a variety of causes, which include transcellular shifts, tissue breakdown, inadequate renal excretion, and drugs. Hyperkalemia (ventricular tachycardia, ventricular fibrillation Ventricular fibrillation Ventricular fibrillation (VF or V-fib) is a type of ventricular tachyarrhythmia (> 300/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular Fibrillation)
      • Hypercalcemia Hypercalcemia Hypercalcemia (serum calcium > 10.5 mg/dL) can result from various conditions, the majority of which are due to hyperparathyroidism and malignancy. Other causes include disorders leading to vitamin D elevation, granulomatous diseases, and the use of certain pharmacological agents. Symptoms vary depending on calcium levels and the onset of hypercalcemia. Hypercalcemia (SVT, ventricular tachycardia)
      • Hypomagnesemia (ventricular arrhythmias)
    • Autoimmune disease
    • Toxic ingestions:
      • Excess caffeine, nicotine
      • Cocaine, amphetamines, or other stimulants Stimulants Stimulants are used by the general public to increase alertness and energy, decrease fatigue, and promote mental focus. Stimulants have medical uses for individuals with ADHD and sleep disorders, and are also used in combination with analgesics in pain management. Stimulants
      • Alcohol withdrawal
    • Hyperthyroidism Hyperthyroidism Thyrotoxicosis refers to the classic physiologic manifestations of excess thyroid hormones and is not synonymous with hyperthyroidism, which is caused by sustained overproduction and release of T3 and/or T4. Graves' disease is the most common cause of primary hyperthyroidism, followed by toxic multinodular goiter and toxic adenoma. Thyrotoxicosis and Hyperthyroidism
    • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview
  • Exercise
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever: interleukins Interleukins Interleukins are a type of cytokines (signaling proteins) that communicate messages between different parts of the immune system. The majority of interleukins are synthesized by helper CD4 T lymphocytes along with other cells such as monocytes, macrophages, and endothelial cells. Interleukins and inflammatory markers cause tachycardia (not directly due to the fever)
  • Anxiety/panic/fear
  • QT-prolonging drugs:
    • Antibiotics
    • Macrolides Macrolides Macrolides and ketolides are antibiotics that inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit and blocking transpeptidation. These antibiotics have a broad spectrum of antimicrobial activity but are best known for their coverage of atypical microorganisms. Macrolides and Ketolides
    • Fluoroquinolones Fluoroquinolones Fluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms. Fluoroquinolones
    • Antiarrhythmics
    • Amiodarone
    • Tricyclic antidepressants Tricyclic antidepressants Tricyclic antidepressants (TCAs) are a class of medications used in the management of mood disorders, primarily depression. These agents, named after their 3-ring chemical structure, act via reuptake inhibition of neurotransmitters (particularly norepinephrine and serotonin) in the brain. Tricyclic Antidepressants
    • Idiopathic: right ventricular outflow tract (RVOT) tachycardia

Anatomy and Physiology

Anatomy

  • Conduction system:
    • SA node:
      • Cluster of cells near the junction of the right atrium and the superior vena cava Superior vena cava The venous trunk which returns blood from the head, neck, upper extremities and chest. Mediastinum and Great Vessels
      • Natural pacemaker: initiates electrical impulses to stimulate contraction
    • AV node:
      • Sits near the coronary sinus on the interatrial septum
      • Receives impulses from the SA node
      • Slows electrical impulses from the SA node (AV nodal delay) to allow atrial ejection of blood before ventricular contraction
    • Bundle of His: conducts impulses from the AV node to the ventricles via the right and left bundles
    • Purkinje fibers: depolarize the ventricles
  • Innervation: 
    • Parasympathetic: reduces sinus node automaticity (↓ heart rate)
    • Sympathetic: increases sinus node automaticity (↑ heart rate)
The conduction system of the heart

Conduction system of the heart

Image by Lecturio.

Physiology

Sequential events of a cardiac cycle Cardiac cycle The cardiac cycle describes a complete contraction and relaxation of all 4 chambers of the heart during a standard heartbeat. The cardiac cycle includes 7 phases, which together describe the cycle of ventricular filling, isovolumetric contraction, ventricular ejection, and isovolumetric relaxation. Cardiac Cycle (numbers correlate to the 6 images below):

1. SA node initiates impulse; P wave: 

  • Atrial depolarization 
  • Atrial contraction

2. PR segment: impulse reaches the AV node and passes to the His bundle. 

3. QRS complex: 

  • Atrial repolarization (masked by QRS complex) 
  • Depolarization of the ventricles
  • Ventricular contraction

4. ST segment: completion of ventricular depolarization

5. T wave: repolarization of ventricles

6. Completion of repolarization

Electrocardiogram and electrical activity of the myocardium

ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) and electrical activity of the myocardium

Image by Lecturio.

Supraventricular Tachyarrhythmias

The most common cause of narrow QRS complex tachycardia is reentry. This reentry is often referred to as “SVT”; however, SVT with aberrant conduction may result in wide-complex QRS if a supraventricular impulse is delayed or blocked.

  • Locations of dysfunction with supraventricular tachycardia Supraventricular tachycardia Supraventricular tachycardias are related disorders in which the elevation in heart rate is driven by pathophysiology in the atria. This group falls under the larger umbrella of tachyarrhythmias and includes paroxysmal supraventricular tachycardias (PSVTs), ventricular pre-excitation syndromes (i.e. Wolff-Parkinson-White syndrome), atrial flutter, multifocal atrial tachycardia, and atrial fibrillation. Supraventricular Tachycardias:
    • SA node:
      • Sinus tachycardia
      • SA nodal reentrant tachycardia
    • Atrial myocardium:
      • Intraatrial reentrant tachycardia
      • Multifocal atrial tachycardia
      • Atrial fibrillation
      • Atrial flutter
    • AV junction:
      • AV nodal reentrant tachycardia
      • Junctional tachycardia
  • Etiology:
    • Reentry (most common):
      • Occurs via an accessory pathway when a propagating impulse fails to terminate normally 
      • Orthodromic is the most common (impulses are conducted in the normal direction); may also be antidromic (impulse travels down the accessory pathway 1st, then back up)
    • Increased automaticity (the ability to generate spontaneous action potentials)
    • Increased triggered activity (spontaneous action potentials during early or delayed afterdepolarizations)
  • Usually results in a narrow-complex QRS tachycardia:
    • Sinus tachycardia:
      • Normal rhythm and morphology of P waves on ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG)
      • May be physiologic or a response to an illness
    • Atrial fibrillation:
      • Irregularly irregular rhythm without P waves
      • Increased risk of embolism and stroke
    • Atrial flutter:
      • Regular rhythm with around 300/min P waves
      • Classic sawtooth pattern on ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG)
    • Atrioventricular reentrant tachycardia (AVRT):
      • Regular rhythm
      • Inverted P waves after QRS complexes
    • Multifocal atrial tachycardia:
      • Multiple ectopic foci in the atrium with ≥ 3 discernible P-wave morphologies
      • Irregularly irregular rhythm
      • Classically caused by pulmonary disease ( chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) ( COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)))
    • Paroxysmal atrial tachycardia:
      • Sudden onset with unusual axis P wave
      • Adenosine to unmask underlying rhythm
    • AVNRT:
      • Reentrant pathway in AV node
      • Depolarizes atria and ventricle nearly simultaneously
  • May occasionally result in wide-complex tachycardia (not originating in the ventricles):
    • SVT with aberrant conduction → wide-complex QRS if a supraventricular impulse is delayed or blocked; seen in individuals with:
      • Left bundle branch block (LBBB)
      • Right bundle branch block (RBBB)
      • Intraventricular conduction delay (IVCD)
    • WPW:
      • Most individuals are asymptomatic; some develop tachyarrhythmias.
      • Results from an accessory pathway (bundle of Kent) that directly connects the atria and ventricles and bypasses the AV node
      • ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG): classic delta wave with short PR interval and widened QRS (with antidromic AVRT, can be narrow-complex if orthodromic)
      • Atrial fibrillation: seen in 10%–30% of individuals with WPW

Ventricular Tachyarrhythmias

Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia is the most common cause of wide-complex QRS tachycardia, especially in individuals with a history of cardiac disease. The diagnosis may be challenging when urgent treatment is needed.

  • Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia: originates below the AV node
    • Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia is the cause of wide complex QRS tachycardias 80%–90% of the time
    • Type and intensity of symptoms vary depending on the rate; occasionally asymptomatic
    • Often due to previous MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction and myocardial scar formation 
      • Ischemic damage → slows the conduction of cardiac electrical impulses
      • Unexcitable scar tissue is surrounded by hyperirritable myocardial cells
    • May also be due to electrolyte abnormalities or channelopathies
    • Can result in hemodynamic collapse and death 
    • Some individuals may have a narrow QRS complex at baseline that widens with faster heart rates. Seen with:
      • Hyperkalemia Hyperkalemia Hyperkalemia is defined as a serum potassium (K+) concentration >5.2 mEq/L. Homeostatic mechanisms maintain the serum K+ concentration between 3.5 and 5.2 mEq/L, despite marked variation in dietary intake. Hyperkalemia can be due to a variety of causes, which include transcellular shifts, tissue breakdown, inadequate renal excretion, and drugs. Hyperkalemia
      • Class IC antiarrhythmic drugs (e.g., flecainide, propafenone)
  • Etiology:
    • Underlying cardiovascular disease:
      • Ischemia/coronary artery disease 
      • MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction
      • Congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure
      • Cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Overview of Cardiomyopathies
      • Myocarditis Myocarditis Myocarditis is an inflammatory disease of the myocardium, which may occur alone or in association with a systemic process. There are numerous etiologies of myocarditis, but all lead to inflammation and myocyte injury, most often leading to signs and symptoms of heart failure. Myocarditis
      • Valvular stenosis or insufficiency
    • Electrolyte imbalances
    • Medications
  • Results in a wide-complex tachycardia:
    • Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia
      • Monomorphic, wide QRS complexes > 120 msec
      • ≥ 3 consecutive ventricular complexes with a rate > 100/min
    • Torsades de pointes:
      • Most common polymorphic ventricular tachycardia
      • Caused by early afterdepolarizations
      • Irregular QRS complexes twist around the isoelectric line (torsades de pointes = twisting of points)
      • A feared complication of long-QT syndrome
      • Rate of 160–250 beats/min
      • Often terminates spontaneously; can lead to sudden cardiac death
      • Many drugs prolong the QT interval, increasing risk of torsades de pointes
  • Ventricular flutter: very rapid monomorphic ventricular tachycardia; usually heart rate 300 beats/min
  • Ventricular fibrillation:
    • Indiscernible QRS
    • Fibrillary waves
    • Loss of P waves
    • Incompatible with life

Clinical Presentation and Diagnosis

The initial approach to evaluating an individual with tachyarrhythmia is assessing hemodynamic stability. Wide-complex tachycardias can be either stable or unstable. 

  • Physical examination is sufficient to identify tachyarrhythmias.
  • ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) differentiates between the types of tachyarrhythmias.
  • SVT presents with:
    • Palpitations (most commonly)
    • Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain
    • Dizziness/light-headedness
    • Shortness of breath
  • Ventricular tachycardia Ventricular tachycardia Ventricular tachycardia is any heart rhythm faster than 100 beats/min, with 3 or more irregular beats in a row, arising distal to the bundle of His. Ventricular tachycardia is the most common form of wide-complex tachycardia, and it is associated with a high mortality rate. Ventricular Tachycardia with low cardiac output presents with:
    • Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain
    • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension 
    • Syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
    • Confusion
    • Loss of consciousness
  • Further testing for suspected tachyarrhythmias with normal ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) on presentation:
    • 48-hour Holter monitor
    • Event monitor

Management

The management of tachyarrhythmias depends on whether the individual is stable or unstable and on an accurate diagnosis of the underlying rhythm, which may be difficult.

  • Hemodynamically unstable individuals → urgent cardioversion
  • Evaluate underlying abnormalities:
    • Cardiac enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes
    • Electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes 
    • Thyroid-stimulating hormone (for thyrotoxicosis)
    • Chest x-ray
    • Urine drug screen (for stimulants Stimulants Stimulants are used by the general public to increase alertness and energy, decrease fatigue, and promote mental focus. Stimulants have medical uses for individuals with ADHD and sleep disorders, and are also used in combination with analgesics in pain management. Stimulants that may cause tachycardia)
    • Coronary angiography
    • Echocardiography 
  • Narrow complex tachycardia in symptomatic individuals:
    • AVNRT: 
      • Vagal maneuvers
      • IV adenosine
      • IV calcium-channel blockers
      • IV beta-blockers
    • Atrial fibrillation:
      • IV calcium channel blockers Calcium Channel Blockers Calcium channel blockers (CCBs) are a class of medications that inhibit voltage-dependent L-type calcium channels of cardiac and vascular smooth muscle cells. The inhibition of these channels produces vasodilation and myocardial depression. There are 2 major classes of CCBs: dihydropyridines and non-dihydropyridines. Class 4 Antiarrhythmic Drugs (Calcium Channel Blockers)
      • IV beta-blockers
    • Multifocal atrial tachycardia: 
      • Treat underlying cause (usually COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)), if possible
      • IV magnesium and potassium if indicated
      • IV calcium channel blocker
      • Avoid beta-blockers in individuals with COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)
  • Wide-complex tachycardia:
    • Assume ventricular tachycardia until proven otherwise
    • If pulseless → defibrillate, administer IV epinephrine
    • If unstable but conscious → urgent synchronized electrocardioversion with sedation
    • If hemodynamically stable: 
      • Evaluate and treat reversible causes (electrolytes, MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction)
      • Attempt to restore normal rhythm with IV medications: procainamide, amiodarone, sotalol, or lidocaine
    • Torsades de pointes:
      • IV magnesium
      • Overdrive pacing if heart rate > 100/min

Clinical Relevance

  • Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia: plasma potassium concentration < 3.5 mEq/L. Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular Transcellular The movement of one cell into, through, and out of another cell. The Tubular System shifts, or poor dietary intake. The condition is usually asymptomatic if minor but can lead to cardiac arrhythmias, muscle weakness, rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis, paralysis, and respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure. Diagnosis is by history and lab testing. Management is by replacing the potassium deficit and treating the underlying cause.
  • Hyperkalemia Hyperkalemia Hyperkalemia is defined as a serum potassium (K+) concentration >5.2 mEq/L. Homeostatic mechanisms maintain the serum K+ concentration between 3.5 and 5.2 mEq/L, despite marked variation in dietary intake. Hyperkalemia can be due to a variety of causes, which include transcellular shifts, tissue breakdown, inadequate renal excretion, and drugs. Hyperkalemia: serum K+ concentration > 5.2 mEq/L. Hyperkalemia Hyperkalemia Hyperkalemia is defined as a serum potassium (K+) concentration >5.2 mEq/L. Homeostatic mechanisms maintain the serum K+ concentration between 3.5 and 5.2 mEq/L, despite marked variation in dietary intake. Hyperkalemia can be due to a variety of causes, which include transcellular shifts, tissue breakdown, inadequate renal excretion, and drugs. Hyperkalemia can be due to various causes, including transcellular Transcellular The movement of one cell into, through, and out of another cell. The Tubular System shifts, tissue breakdown, inadequate renal excretion, and drugs. The condition is usually asymptomatic if minor in severity; however, acute elevations or severe hyperkalemia can lead to potentially fatal cardiac arrhythmias. Management is potassium replacement and treating the underlying conditions.
  • Hypercalcemia Hypercalcemia Hypercalcemia (serum calcium > 10.5 mg/dL) can result from various conditions, the majority of which are due to hyperparathyroidism and malignancy. Other causes include disorders leading to vitamin D elevation, granulomatous diseases, and the use of certain pharmacological agents. Symptoms vary depending on calcium levels and the onset of hypercalcemia. Hypercalcemia: serum calcium level > 10.3 mg/dL, resulting from various conditions, most often hyperparathyroidism Hyperparathyroidism Hyperparathyroidism is a condition associated with elevated blood levels of parathyroid hormone (PTH). Depending on the pathogenesis of this condition, hyperparathyroidism can be defined as primary, secondary or tertiary. Hyperparathyroidism and malignancy. Severe hypercalcemia can lead to supraventricular or ventricular tachycardia. Treatment depends on the underlying cause.
  • Coronary artery disease: inadequate supply of blood to the myocardium, typically because of atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis. The myocardium becomes ischemic when the oxygen supply does not meet oxygen demand, and this may cause cardiac arrhythmias. Diagnosis is based on history and electrocardiographic findings, cardiac stress tests, or heart catheterization. Management is primarily based on reducing the oxygen demand of the heart and increasing the delivery of oxygen.
  • Myocardial infarction Myocardial infarction MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction: ischemia of an area of myocardial tissue due to insufficient blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure and oxygenation. Clinical presentation is with chest pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain. Diagnosis is by history, ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) changes, increases in cardiac enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes, and evidence of wall-motion abnormalities. MI MI MI is ischemia and death of an area of myocardial tissue due to insufficient blood flow and oxygenation, usually from thrombus formation on a ruptured atherosclerotic plaque in the epicardial arteries. Clinical presentation is most commonly with chest pain, but women and patients with diabetes may have atypical symptoms. Myocardial Infarction may lead to cardiac arrhythmias. Management is with thrombolytic therapy versus percutaneous intervention. All individuals receive nitrates Nitrates Nitrates are a class of medications that cause systemic vasodilation (veins > arteries) by smooth muscle relaxation. Nitrates are primarily indicated for the treatment of angina, where preferential venodilation causes pooling of blood, decreased preload, and ultimately decreased myocardial O2 demand. Nitrates, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control, aspirin, anticoagulation, and beta-blockers.
  • Long-QT syndrome: disorder of the heart’s electrical activity that affects the repolarization of the heart after a heartbeat. Long-QT syndrome may be congenital or acquired and is typically characterized by a prolongation of the QT interval on the ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG) and by the occurrence of syncope or cardiac arrest Cardiac arrest Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest. Medications that prolong the QT interval may lead to ventricular tachycardia.
  • Ventricular fibrillation: type of ventricular tachyarrhythmia (> 300 beats/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular fibrillation is most commonly caused by underlying ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
  • Cardiac arrest: sudden complete cessation of cardiac output with hemodynamic collapse. Individuals present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest Cardiac arrest Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest are ventricular fibrillation Ventricular fibrillation Ventricular fibrillation (VF or V-fib) is a type of ventricular tachyarrhythmia (> 300/min) often preceded by ventricular tachycardia. In this arrhythmia, the ventricle beats rapidly and sporadically. The ventricular contraction is uncoordinated, leading to a decrease in cardiac output and immediate hemodynamic collapse. Ventricular Fibrillation/tachycardia, asystole, or pulseless electrical activity. Management of cardiac arrest Cardiac arrest Cardiac arrest is the sudden, complete cessation of cardiac output with hemodynamic collapse. Patients present as pulseless, unresponsive, and apneic. Rhythms associated with cardiac arrest are ventricular fibrillation/tachycardia, asystole, or pulseless electrical activity. Cardiac Arrest starts with basic life support (BLS) outside the hospital and advanced cardiac life support (ACLS) in the hospital.

References

  1. Brugada, J., et al., (2020). 2019 ESC guidelines for the management of patients with supraventricular tachycardia: the task force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). European Heart Journal 41:655–720. doi:10.1093/eurheartj/ehz467
  2. Al-Khatib, S.M., et al. (2018). 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Journal of the American College of Cardiology 72:e91–e220. https://doi.org/10.1016/j.jacc.2017.10.054 
  3. Kashou, A.H., et al. (2020). Wide complex tachycardia differentiation: a reappraisal of the state-of-the-art. Journal of the American Heart Association 9(11):e016598. https://doi.org/10.1161/jaha.120.016598
  4. Prutkin, J.P. (2021). Overview of the acute management of tachyarrhythmias. UpToDate. Retrieved November 4, 2021, from https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias
  5. Homoud, M.K. (2021). Sinus tachycardia: evaluation and management. UpToDate. Retrieved November 4, 2021, from https://www.uptodate.com/contents/sinus-tachycardia-evaluation-and-management
  6. Ganz, L.I. (2019). Wide QRS complex tachycardias: approach to the diagnosis. UpToDate. Retrieved November 4, 2021, from https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis
  7. Ganz, L.I. (2020). Narrow QRS complex tachycardias: clinical manifestations, diagnosis, and evaluation. UpToDate. Retrieved November 8, 2021, from https://www.uptodate.com/contents/narrow-qrs-complex-tachycardias-clinical-manifestations-diagnosis-and-evaluation

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