Atrial flutter

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Atrial flutter
Atrial flutter34.svg
Atrial flutter with varying A-V conduction (5:1 and 4:1)
Specialty Cardiology
Diagnostic method Electrocardiography

Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart. [1] When it first occurs, it is usually associated with a fast heart rate and is classified as a type of supraventricular tachycardia. [2] Atrial flutter is characterized by a sudden-onset (usually) regular abnormal heart rhythm on an electrocardiogram (ECG) in which the heart rate is fast. Symptoms may include a feeling of the heart beating too fast, too hard, or skipping beats, chest discomfort, difficulty breathing, a feeling as if one's stomach has dropped, a feeling of being light-headed, or loss of consciousness.

Contents

Although this abnormal heart rhythm typically occurs in individuals with cardiovascular disease (e.g., high blood pressure, coronary artery disease, and cardiomyopathy) and diabetes mellitus, it may occur spontaneously in people with otherwise normal hearts. It is typically not a stable rhythm and often degenerates into atrial fibrillation (AF). [3] But rarely does it persist for months or years. Similar to the abnormal heart rhythm atrial fibrillation, atrial flutter also leads to poor contraction of the atrial chambers of the heart. This leads to the pooling of the blood in the heart and can lead to the formation of blood clots in the heart, which poses a significant risk of breaking off and traveling through the bloodstream, resulting in strokes.

A supraventricular tachycardia with a ventricular heart rate of 150 beats per minute is suggestive (though not necessarily diagnostic) of atrial flutter. Administration of adenosine in the vein (intravenously) can help medical personnel differentiate between atrial flutter and other forms of supraventricular tachycardia. [2] Immediate treatment of atrial flutter centers on slowing the heart rate with medications such as beta blockers (e.g., metoprolol) or calcium channel blockers (e.g., diltiazem) if the affected person is not having chest pain, has not lost consciousness, and if their blood pressure is normal (known as stable atrial flutter). If the affected person is having chest pain, has lost consciousness, or has low blood pressure (unstable atrial flutter), then an urgent electrical shock to the heart to restore a normal heart rhythm is necessary. Long-term use of blood thinners (e.g., warfarin or apixaban) is an important component of treatment to reduce the risk of blood clot formation in the heart and resultant strokes. [3] [4] Medications used to restore a normal heart rhythm (antiarrhythmics) such as ibutilide effectively control atrial flutter about 80% of the time when they are started but atrial flutter recurs at a high rate (70–90% of the time) despite continued use. [1] Atrial flutter can be treated more definitively with a technique known as catheter ablation. This involves the insertion of a catheter through a vein in the groin which is followed up to the heart and is used to identify and interrupt the electrical circuit causing the atrial flutter (by creating a small burn and scar).

Atrial flutter was first identified as an independent medical condition in 1920 by the British physician Sir Thomas Lewis (1881–1945) and colleagues. [5] AFL is the second most common pathologic supraventricular tachycardia but occurs at a rate less than one-tenth of the most common supraventricular tachycardia (atrial fibrillation). [2] [3] The overall incidence of AFL has been estimated at 88 cases per 100,000 person-years. The incidence of AFL is significantly lower (~5 cases/100,000 person-years) in those younger than age 50 and is far more common (587 cases/100,000 person-years) in those over 80 years of age. [3]

Signs and symptoms

While atrial flutter can sometimes go unnoticed, its onset is often marked by characteristic sensations of the heart feeling like it is beating too fast or hard. Such sensations usually last until the episode resolves, or until the heart rate is controlled. [6]

Atrial flutter is usually well-tolerated initially (a high heart rate is, for most people just a normal response to exercise); however, people with other underlying heart diseases (such as coronary artery disease) or poor exercise tolerance may rapidly develop symptoms, such as shortness of breath, chest pain, lightheadedness or dizziness, nausea and, in some patients, nervousness and feelings of impending doom. [6]

Prolonged atrial flutter with fast heart rates may lead to decompensation with loss of normal heart function (heart failure). This may manifest as exercise intolerance (exertional breathlessness), difficulty breathing at night, or swelling of the legs and/or abdomen. [6]

Complications

Although often regarded as a relatively benign heart rhythm problem, atrial flutter shares the same complications as the related condition atrial fibrillation. There is a paucity of published data directly comparing the two, but overall mortality in these conditions appears to be very similar. [7]

Rapid heart rates may produce significant symptoms in patients with pre-existing heart disease and can lead to inadequate blood flow to the heart muscle and even a heart attack. [1]

In rare situations, atrial flutter associated with a fast heart rate persists for an extended period of time without being corrected to a normal heart rhythm and leads to a tachycardia-induced cardiomyopathy. [1] Even in individuals with a normal heart, if the heart beats too quickly for a prolonged period of time, this can lead to ventricular decompensation and heart failure.[ citation needed ]

Clot formation

Because there is little, if any, effective contraction of the atria, there is stasis (pooling) of blood in the atria. Stasis of blood in susceptible individuals can lead to the formation of a thrombus (blood clot) within the heart. A thrombus is most likely to form in the atrial appendages. A blood clot in the left atrial appendage is particularly important as the left side of the heart supplies blood to the entire body through the arteries. Thus, any thrombus material that dislodges from this side of the heart can embolize (break off and travel) to the brain's arteries, with the potentially devastating consequence of a stroke. Thrombus material can embolize to any other portion of the body, though usually with a less severe outcome. [8]

Sudden cardiac death

Sudden death is not directly associated with atrial flutter. However, in individuals with a pre-existing accessory conduction pathway, such as the bundle of Kent in Wolff-Parkinson-White syndrome, the accessory pathway may conduct activity from the atria to the ventricles at a rate that the AV node would usually block. Bypassing the AV node, the atrial rate of 300 beats/minute leads to a ventricular rate of 300 beats/minute (1:1 conduction). Even if the ventricles are able to sustain a cardiac output at such a high rate, 1:1 flutter with time may degenerate into ventricular fibrillation, causing hemodynamic collapse and death. [9]

Pathophysiology

Atrial flutter is caused by a re-entrant rhythm. This usually occurs along the cavo-tricuspid isthmus of the right atrium though atrial flutter can originate in the left atrium as well. Typically initiated by a premature electrical impulse arising in the atria, atrial flutter is propagated due to differences in refractory periods of atrial tissue. This creates electrical activity that moves in a localized self-perpetuating loop, which usually lasts about 200 milliseconds for the complete circuit. For each cycle around the loop, an electric impulse results and propagates through the atria.[ citation needed ]

The impact and symptoms of atrial flutter depend on the heart rate of the affected person. Heart rate is a measure of ventricular rather than atrial activity. Impulses from the atria are conducted to the ventricles through the atrio-ventricular node (AV node). In a person with atrial flutter, a 12-lead electrocardiogram (ECG) will demonstrate the atrial chambers of the heart contracting at a rate of 280–300 beats per minute whereas the ventricular chambers of the heart typically beat at a rate of 140–150 beats per minute. [2] Due primarily to its longer refractory period, the AV node exerts a protective effect on heart rate by blocking atrial impulses in excess of about 180 beats/minute, for the example of a resting heart rate. (This block is dependent on the age of the patient and can be calculated roughly by subtracting patient age from 220). If the flutter rate is 300 beats per minute, only half of these impulses will be conducted, giving a ventricular rate of 150 beats per minute, or a 2:1 heart block. The addition of rate-controlling drugs or conduction system disease can increase this block substantially [10]

Diagnosis

Typical atrial flutter is recognized on an electrocardiogram by the presence of characteristic "flutter waves" at a regular rate of 250 to 350 beats per minute. Flutter waves may not be evident on an ECG in atypical forms of atrial flutter. Individual flutter waves may be symmetrical, resembling p-waves, or maybe asymmetrical with a "sawtooth" shape, rising gradually and falling abruptly or vice versa. If atrial flutter is suspected clinically but is not clearly evident on ECG, acquiring a Lewis lead ECG may be helpful in revealing flutter waves.[ citation needed ]

Classification

There are two types of atrial flutter, the common type I and rarer type II. [11] Most individuals with atrial flutter will manifest only one of these. Rarely someone may manifest both types; however, they can manifest only one type at a time.[ citation needed ]

Type I

Type I atrial flutter, counterclockwise rotation with 3:1 and 4:1 AV nodal block. AtrialFlutter12.JPG
Type I atrial flutter, counterclockwise rotation with 3:1 and 4:1 AV nodal block.
Atrial flutter with a two to one block. Note the P waves hiding in the T waves in leads V1 and V2 Aflut.jpg
Atrial flutter with a two to one block. Note the P waves hiding in the T waves in leads V1 and V2

Type I atrial flutter, also known as common atrial flutter or typical atrial flutter, has an atrial rate of 240 to 340 beats/minute. However, this rate may be slowed by antiarrhythmic agents.[ citation needed ]

The reentrant loop circles the right atrium, passing through the cavo-tricuspid isthmus – a body of fibrous tissue in the lower atrium between the inferior vena cava, and the tricuspid valve. [1] Type I flutter is further divided into two subtypes, known as counterclockwise atrial flutter and clockwise atrial flutter depending on the direction of current passing through the loop. [1]

  • Counterclockwise atrial flutter (known as cephalad-directed atrial flutter) is more commonly seen. The flutter waves in this rhythm are inverted in ECG leads II, III, and aVF. [1]
  • The re-entry loop cycles in the opposite direction in clockwise atrial flutter, thus the flutter waves are upright in II, III, and aVF. [1]

Type II

Type II (atypical) atrial flutter follows a significantly different re-entry pathway to type I flutter, and is typically faster, usually 340–350 beats/minute. [12] Atypical atrial flutter rarely occurs in people who have not undergone previous heart surgery or previous catheter ablation procedures. Left atrial flutter is considered atypical and is common after incomplete left atrial ablation procedures. [13] Atypical atrial flutter originating from the right atrium and heart's septum have also been described.[ citation needed ]

Management

In general, atrial flutter should be managed in the same way as atrial fibrillation. Because both rhythms can lead to the formation of a blood clot in the atrium, individuals with atrial flutter usually require some form of anticoagulation or antiplatelet agent. Both rhythms can be associated with dangerously fast heart rates and thus require medication to control the heart rate (such as beta blockers or calcium channel blockers) and/or rhythm control with class III antiarrhythmics (such as ibutilide or dofetilide). However, atrial flutter is more resistant to correction with such medications than atrial fibrillation. [1] For example, although the class III antiarrhythmic agent ibutilide is an effective treatment for atrial flutter, rates of recurrence after treatment are quite high (70–90%). [1] Additionally, there are some specific considerations particular to treatment of atrial flutter.[ citation needed ]

Cardioversion

Atrial flutter is considerably more sensitive to electrical direct current cardioversion than atrial fibrillation, with a shock of only 20 to 50 Joules commonly being enough to cause a return to a normal heart rhythm (sinus rhythm). Exact placement of the pads does not appear important. [14]

Ablation

Due to the reentrant nature of atrial flutter, it is often possible to ablate the circuit that causes atrial flutter with radiofrequency catheter ablation or pulsed field ablation. Catheter ablation wasconsidered to be a first-line treatment method for many people with typical atrial flutter due to its high rate of success (>90%) and low incidence of complications, [1] although pulsed field ablation now offers a non-thermal option. This is done in the cardiac electrophysiology lab by causing a ridge of scar tissue in the cavotricuspid isthmus that crosses the path of the circuit that causes atrial flutter. Eliminating conduction through the isthmus prevents reentry, and if successful, prevents the recurrence of the atrial flutter. Atrial fibrillation often occurs (30% within 5 years) after catheter ablation for atrial flutter. [1]

Related Research Articles

<span class="mw-page-title-main">Electrocardiography</span> Examination of the hearts electrical activity

Electrocardiography is the process of producing an electrocardiogram, a recording of the heart's electrical activity through repeated cardiac cycles. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including:

<span class="mw-page-title-main">Cardioversion</span> Conversion of a cardiac arrhythmia to a normal rhythm using an electrical shock or medications

Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or other cardiac arrhythmia is converted to a normal rhythm using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle, restoring the activity of the electrical conduction system of the heart. Pharmacologic cardioversion, also called chemical cardioversion, uses antiarrhythmia medication instead of an electrical shock.

<span class="mw-page-title-main">Tachycardia</span> Heart rate exceeding normal resting rate

Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal or abnormal.

<span class="mw-page-title-main">Wolff–Parkinson–White syndrome</span> Abnormal heart rhythm due to faulty electrical connections in the heart

Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart involving an accessory pathway able to conduct electrical current between the atria and the ventricles, thus bypassing the atrioventricular node. About 60% of people with the electrical problem developed symptoms, which may include an abnormally fast heartbeat, palpitations, shortness of breath, lightheadedness, or syncope. Rarely, cardiac arrest may occur. The most common type of irregular heartbeat that occurs is known as paroxysmal supraventricular tachycardia.

<span class="mw-page-title-main">Sinus node dysfunction</span> Medical condition

Sinus node dysfunction (SND), also known as sick sinus syndrome (SSS), is a group of abnormal heart rhythms (arrhythmias) usually caused by a malfunction of the sinus node, the heart's primary pacemaker. Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome in which the arrhythmia alternates between fast and slow heart rates.

<span class="mw-page-title-main">Palpitations</span> Perceived cardiac abnormality in which ones heartbeat can be felt

Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart.

<span class="mw-page-title-main">Ventricular tachycardia</span> Abnormally fast rhythm of the hearts ventricles

Ventricular tachycardia is a cardiovascular disorder in which fast heart rate occurs in the ventricles of the heart. Although a few seconds of VT may not result in permanent problems, longer periods are dangerous; and multiple episodes over a short period of time are referred to as an electrical storm. Short periods may occur without symptoms, or present with lightheadedness, palpitations, shortness of breath, chest pain, and decreased level of consciousness. Ventricular tachycardia may lead to coma and persistent vegetative state due to lack of blood and oxygen to the brain. Ventricular tachycardia may result in ventricular fibrillation (VF) and turn into cardiac arrest. This conversion of the VT into VF is called the degeneration of the VT. It is found initially in about 7% of people in cardiac arrest.

<span class="mw-page-title-main">Supraventricular tachycardia</span> Abnormally fast heart rhythm

Supraventricular tachycardia (SVT) is an umbrella term for fast heart rhythms arising from the upper part of the heart. This is in contrast to the other group of fast heart rhythms – ventricular tachycardia, which start within the lower chambers of the heart. There are four main types of SVT: atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and Wolff–Parkinson–White syndrome. The symptoms of SVT include palpitations, feeling of faintness, sweating, shortness of breath, and/or chest pain.

<span class="mw-page-title-main">AV nodal reentrant tachycardia</span> Medical condition

AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia. It is more common in women than men. The main symptom is palpitations. Treatment may be with specific physical maneuvers, medications, or, rarely, synchronized cardioversion. Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed.

<span class="mw-page-title-main">Catheter ablation</span> Removal or termination of an electrical pathway from parts of the heart

Catheter ablation is a procedure that uses radio-frequency energy or other sources to terminate or modify a faulty electrical pathway from sections of the heart of those who are prone to developing cardiac arrhythmias such as atrial fibrillation, atrial flutter and Wolff-Parkinson-White syndrome. If not controlled, such arrhythmias increase the risk of ventricular fibrillation and sudden cardiac arrest. The ablation procedure can be classified by energy source: radiofrequency ablation and cryoablation.

Premature atrial contraction (PAC), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common cardiac dysrhythmia characterized by premature heartbeats originating in the atria. While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat, in contrast to escape beats, in which the normal sinoatrial node fails, leaving a non-nodal pacemaker to initiate a late beat.

Tachycardia-induced cardiomyopathy (TIC) is a disease where prolonged tachycardia or arrhythmia causes an impairment of the myocardium, which can result in heart failure. People with TIC may have symptoms associated with heart failure and/or symptoms related to the tachycardia or arrhythmia. Though atrial fibrillation is the most common cause of TIC, several tachycardias and arrhythmias have been associated with the disease.

<span class="mw-page-title-main">Multifocal atrial tachycardia</span> Fast heart rhythm associated with exacerbations of COPD

Multifocal atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmonary disease (COPD). Normally, the heart rate is controlled by a cluster of cells called the sinoatrial node. When a number of different clusters of cells outside the SA node take over control of the heart rate, and the rate exceeds 100 beats per minute, this is called multifocal atrial tachycardia.

<span class="mw-page-title-main">Wandering atrial pacemaker</span> Medical condition

Wandering atrial pacemaker (WAP) is an atrial rhythm where the pacemaking activity of the heart originates from different locations within the atria. This is different from normal pacemaking activity, where the sinoatrial node is responsible for each heartbeat and keeps a steady rate and rhythm. Causes of wandering atrial pacemaker are unclear, but there may be factors leading to its development. It is often seen in the young, the old, and in athletes, and rarely causes symptoms or requires treatment. Diagnosis of wandering atrial pacemaker is made by an ECG.

The following outline is provided as an overview of and topical guide to cardiology, the branch of medicine dealing with disorders of the human heart. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in cardiology are called cardiologists.

<span class="mw-page-title-main">Junctional ectopic tachycardia</span> Irregular heartbeat due to abnormal conduction from the atrioventricular nerve

Junctional ectopic tachycardia (JET) is a rare syndrome of the heart that manifests in patients recovering from heart surgery. It is characterized by cardiac arrhythmia, or irregular beating of the heart, caused by abnormal conduction from or through the atrioventricular node. In newborns and infants up to 6 weeks old, the disease may also be referred to as His bundle tachycardia or congenital JET.

Atrial tachycardia is a type of heart rhythm problem in which the heart's electrical impulse comes from an ectopic pacemaker in the upper chambers (atria) of the heart, rather than from the sinoatrial node, the normal origin of the heart's electrical activity. As with any other form of tachycardia, the underlying mechanism can be either the rapid discharge of an abnormal focus, the presence of a ring of cardiac tissue that gives rise to a circle movement (reentry), or a triggered rapid rhythm due to other pathological circumstances.

<span class="mw-page-title-main">Atrial fibrillation</span> Irregular beating of the atria of the heart

Atrial fibrillation is an abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or continuous over time. It may also start as other forms of arrhythmia such as atrial flutter that then transform into AF.

<span class="mw-page-title-main">Arrhythmia</span> Group of medical conditions characterized by irregular heartbeat

Arrhythmias, also known as cardiac arrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. Some types of arrhythmias have no symptoms. Symptoms, when present, may include palpitations or feeling a pause between heartbeats. In more serious cases, there may be lightheadedness, passing out, shortness of breath, chest pain, or decreased level of consciousness. While most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in sudden death.

<span class="mw-page-title-main">Rhythm interpretation</span>

Rhythm interpretation is an important part of healthcare in Emergency Medical Services (EMS). Trained medical personnel can determine different treatment options based on the cardiac rhythm of a patient. There are many common heart rhythms that are part of a few different categories, sinus arrhythmia, atrial arrhythmia, ventricular arrhythmia. Rhythms can be evaluated by measuring a few key components of a rhythm strip, the PQRST sequence, which represents one cardiac cycle, the ventricular rate, which is the rate at which the ventricles contract, and the atrial rate, which is the rate at which the atria contract.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Sawhney, NS; Anousheh, R; Chen, WC; Feld, GK (February 2009). "Diagnosis and management of typical atrial flutter". Cardiology Clinics (Review). 27 (1): 55–67, viii. doi:10.1016/j.ccl.2008.09.010. PMID   19111764.
  2. 1 2 3 4 Link, MS (October 2012). "Clinical practice. Evaluation and initial treatment of supraventricular tachycardia". New England Journal of Medicine. 367 (15): 1438–48. doi:10.1056/NEJMcp1111259. PMID   23050527.
  3. 1 2 3 4 Bun, SS; Latcu, DG; Marchlinski, F; Saoudi, N (September 2015). "Atrial flutter: more than just one of a kind". European Heart Journal. 36 (35): 2356–63. doi: 10.1093/eurheartj/ehv118 . PMID   25838435.
  4. ↑ Vadmann, H; Nielsen, PB; Hjortshøj, SP; Riahi, S; Rasmussen, LH; Lip, GY; Larsen, TB (September 2015). "Atrial flutter and thromboembolic risk: a systematic review". Heart. 101 (18): 1446–55. doi:10.1136/heartjnl-2015-307550. PMID   26149627. S2CID   26126493.
  5. ↑ Lewis T, Feil HS, Stroud WD (1920). "Observations upon flutter, fibrillation, II: the nature of auricular flutter". Heart. 7: 191.
  6. 1 2 3 "Atrial Flutter". Johns Hopkins Medicine. 22 February 2021. Retrieved 3 July 2021.
  7. ↑ Vidaillet H, Granada JF, Chyou PH, Maassen K, Ortiz M, Pulido JN, et al. (2002). "A Population-Based Study of Mortality among Patients with Atrial Fibrillation or Flutter". The American Journal of Medicine. 113 (5): 365–70. doi:10.1016/S0002-9343(02)01253-6. PMID   12401530.
  8. ↑ Stoddard, M. F. (2000). "Risk of thromboembolism in acute atrial fibrillation or atrial flutter". Echocardiography. 17 (4): 393–405. doi:10.1111/j.1540-8175.2000.tb01155.x. PMID   10979012. S2CID   20652213 . Retrieved 3 July 2021.
  9. ↑ Yow, A. G.; Rajasurya, V.; Sharma, S. (2023). "Sudden Cardiac Death". National Center for Biotechnology Information, U.S. National Library of Medicine. PMID   29939631 . Retrieved 3 July 2021.
  10. ↑ "Atrial Flutter". The Lecturio Medical Concept Library. Retrieved 3 July 2021.
  11. ↑ Surawicz, Borys; Knilans, Timothy K.; Chou, Te-Chuan (2001). Chou's electrocardiography in clinical practice: adult and pediatric. Philadelphia: Saunders. ISBN   978-0-7216-8697-4.[ page needed ]
  12. ↑ "Atrial Flutter: Overview". eMedicine Cardiology. Archived from the original on 26 February 2009. Retrieved 2009-03-06.
  13. ↑ Garan, H (April 2008). "Atypical atrial flutter". Heart Rhythm. 5 (4): 618–21. doi:10.1016/j.hrthm.2007.10.031. PMID   18325846.
  14. ↑ Kirkland, S; Stiell, I; AlShawabkeh, T; Campbell, S; Dickinson, G; Rowe, BH (July 2014). "The efficacy of pad placement for electrical cardioversion of atrial fibrillation/flutter: a systematic review". Academic Emergency Medicine. 21 (7): 717–26. doi: 10.1111/acem.12407 . PMID   25117151.
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