Classification
Classification system
First detected-only one diagnosed episode
Paroxysmal-recurrent episodes that stop on their own in
less than seven days
Persistent-recurrent episodes that last more than seven
days
Longstanding Persistent -recurrent
episodes that last more than twelve months
Permanent-AF that has been accepted, and for which a solely
rate control strategy has been decided upon.
The American College of Cardiology (ACC), American Heart
Association (AHA), and the European Society of Cardiology (ESC) recommend in
their guidelines the following classification system based on simplicity and
clinical relevance.
All people with AF are initially in the category called
first detected AF. These people may or may not have had previous undetected
episodes. If a first detected episode stops on its own in less than seven days
and then another episode begins, later on, the category changes to paroxysmal
AF. Although people in this category have episodes lasting up to seven days, in
most cases of paroxysmal AF, the episodes will stop in less than 24 hours. If
the episode lasts for more than seven days, it is unlikely to stop on its own
and is then known as persistent AF. In this case, cardioversion can be
attempted to restore a normal rhythm. If an episode continues for a year or
more, the rhythm is then known as longstanding persistent AF. If a decision is
made by the person and their medical team to accept persistent AF and not
attempt restoration of a normal sinus rhythm but instead manage the AF by
simply controlling the person's ventricular rate then the rhythm is referred to
as permanent AF. As a further subtype, AF that is detected only by an implanted
or wearable cardiac monitor is known as subclinical AF.
Episodes that last less than 30 seconds are not considered
in this classification system. Also, this system does not apply to cases where
the AF is a secondary condition that occurs in the setting of a primary
condition that may be the cause of the AF.
About half of people with AF have permanent AF, while a
quarter have paroxysmal AF, and a quarter have persistent AF.
In addition to the above AF categories, which are mainly
defined by episode timing and termination, the ACC/AHA/ESC guidelines describe
additional AF categories in terms of other characteristics of the person.
Valvular AF refers to AF attributable to moderate to severe mitral valve
stenosis or atrial fibrillation in the presence of a mechanical artificial heart
valve. This distinction may be useful as it has implications on appropriate
treatment, including differing recommendations for anticoagulation, but the
most recent guidelines discourage use of this term as it may be confusing.
Other historically used definitions include lone AF – AF occurring in those
aged under 60 in the absence of other cardiovascular or respiratory diseases.
This description is also discouraged as it is recognised that AF always has an
underlying cause. Secondary AF refers to AF that occurs in the setting of
another condition that have caused the AF, such as acute myocardial infarction,
cardiac surgery, pericarditis, myocarditis, hyperthyroidism, pulmonary
embolism, pneumonia, or another acute pulmonary disease.
Prevention
Prevention of atrial fibrillation focuses primarily on
preventing or controlling its risk factors. Many of its risk factors, such as
obesity, smoking, lack of physical activity, and excessive alcohol consumption,
are modifiable and preventable with lifestyle modification or can be managed by
a healthcare professional.
Lifestyle
modification
Several healthy lifestyle behaviors are associated with a
lower likelihood of developing atrial fibrillation. Accordingly, consensus
guidelines recommend abstaining from alcohol and recreational drugs, stopping
tobacco use, maintaining a healthy weight, and regularly participating in
moderate-intensity physical activities. Consistent moderate-intensity aerobic
exercise, defined as achieving 3.0–5.9 METs of intensity, for at least 150
minutes per week may reduce the risk of developing new-onset atrial
fibrillation. Few studies have examined the role of specific dietary changes
and how it relates to the prevention of atrial fibrillation.
Management
The main goals of treatment are to prevent circulatory
instability and stroke. Rate or rhythm control is used to achieve the former,
whereas anticoagulation is used to decrease the risk of the latter. If
cardiovascularly unstable due to uncontrolled tachycardia, immediate
cardioversion is indicated. Many antiarrhythmics, when used long term, increase
the risk of death without any meaningful benefit. An integrated management
approach, which includes stroke prevention, symptoms control and management of
associated comorbidities, has been associated with better outcomes in patients
with atrial fibrillation.
This holistic or integrated care approach is summed up as
the ABC (Atrial fibrillation Better Care) pathway, as follows:
A: Avoid stroke with Anticoagulation, where the
default is stroke prevention unless the patient is at low risk. Stroke
prevention means use of oral anticoagulation (OAC), whether with well managed
vitamin K antagonists (VKA), with time in therapeutic range >70%, or more
commonly, label-adherent dosed direct oral anticoagulant (DOAC).
B: Better symptom and atrial fibrillation management
with patient-centered, symptom directed decisions on rate control or rhythm
control. In some selected patients, use early rhythm control may be beneficial.
C: Cardiovascular risk factor and comorbidity management,
including attention to lifestyle factors and psychological morbidity.
Lifestyle
modification
Regular aerobic exercise improves atrial fibrillation
symptoms and AF-related quality of life. The effect of high-intensity interval
training on reducing atrial fibrillation burden is unclear. Weight loss of at
least 10% is associated with reduced atrial fibrillation burden in people who
are overweight or obese.
Comorbidity treatment
For people who have both atrial fibrillation and obstructive
sleep apnea, observational studies suggest that continuous positive airway
pressure (CPAP) treatment appears to lower the risk of atrial fibrillation
recurrence after undergoing ablation. Randomized controlled trials examining
the role of obstructive sleep apnea treatment on atrial fibrillation incidence
and burden are lacking. Guideline-recommended lifestyle and medical
interventions are recommended for people with atrial fibrillation and
coexisting conditions such as hyperlipidemia, diabetes mellitus, or
hypertension without specific blood sugar or blood pressure targets for people
with atrial fibrillation.
Bariatric surgery may reduce the risk of new-onset atrial
fibrillation in people with obesity without AF and may reduce the risk of a recurrence
of AF after an ablation procedure in people with coexisting obesity and atrial
fibrillation. It is important for all people with atrial fibrillation to
optimize the control of all coexisting medical conditions that can worsen their
atrial fibrillation, such as hyperthyroidism, diabetes, congestive heart failure,
high blood pressure, chronic obstructive pulmonary disease, stimulant use
(e.g., methamphetamine dependence), and excessive alcohol consumption.
Anticoagulants
Anticoagulation can be used to reduce the risk of stroke
from AF. Anticoagulation is recommended in most people other than those at low
risk of stroke or those at high risk of bleeding. The risk of falls and
consequent bleeding in frail elderly people should not be considered a barrier
to initiating or continuing anticoagulation since the risk of fall-related
brain bleeding is low and the benefit of stroke prevention often outweighs the
risk of bleeding. Similarly, the presence or absence of AF symptoms does not
determine whether a person warrants anticoagulation and is not an indicator of
stroke risk. Oral anticoagulation is underused in atrial fibrillation, while
aspirin is overused in many who should be treated with a direct oral anticoagulant
(DOAC) or warfarin. In 2019, DOACs were often recommended over warfarin by the American
Heart Association.
The risk of stroke from non-valvular AF can be estimated
using the CHA2DS2-VASc score. In the 2019 AHA/ACC/HRS guidelines
anticoagulation is recommended in non-valvular AF if there is a score of two or
more in men and three or more in women and may be considered if there is a
score of one in men or two in women; not using anticoagulation is reasonable if
there is a score of zero in men or one in women. Guidelines from the American
College of Chest Physicians, Asia-Pacific Heart Rhythm Society, Canadian
Cardiovascular Society, European Society of Cardiology, Japanese Circulation
Society, Korean Heart Rhythm Society, and the National Institute for Health and
Care Excellence recommend the use of novel oral anticoagulants or warfarin with
a CHA2DS2-VASc score of one over aspirin and some directly recommend against aspirin.
Experts generally advocate for most people with atrial fibrillation with
CHA2DS2-VASc scores of one or more receiving anticoagulation though aspirin is
sometimes used for people with a score of one (moderate risk for stroke). There
is little evidence to support the idea that the use of aspirin significantly
reduces the risk of stroke in people with atrial fibrillation. Furthermore,
aspirin's major bleeding risk (including bleeding in the brain) is similar to
that of warfarin and DOACs despite its inferior efficacy.
Anticoagulation can be achieved through several means including
warfarin, heparin, dabigatran, rivaroxaban, edoxaban, and apixaban. Many issues
should be considered related to their comparative effectiveness, including the
cost of DOACs, risk of stroke, risk of falls, comorbidities (such as chronic
liver or kidney disease), the presence of significant mitral stenosis or
mechanical heart valves, compliance, and speed of the desired onset of
anticoagulation. The optimal approach to anticoagulation in people with AF and
who simultaneously have other diseases (e.g., cirrhosis and end-stage kidney
disease on dialysis) that predispose a person to both bleeding and clotting complications
is unclear.
For those with non-valvular atrial fibrillation, DOACs are
at least as effective as warfarin for preventing strokes and blood clots
embolizing to the systemic circulation (if not more so) and are generally
preferred over warfarin. DOACs carry a lower risk of bleeding in the brain
compared to warfarin, although dabigatran is associated with a higher risk of
intestinal bleeding. Dual antiplatelet therapy with aspirin and clopidogrel is
inferior to warfarin for preventing strokes or systemic embolism and has
comparable bleeding risk in people with atrial fibrillation. In those who are
also on aspirin, however, DOACs appear to be better than warfarin.
Time in therapeutic range (TTR) and INR variability are commonly
used to assess the quality of VKA treatment. Patients who are unable to
maintain a therapeutic INR on VKA, as indicated by low TTR and/or high INR
variability, are at an increased risk of thromboembolic and bleeding events. In
these patients, treatment with a DOAC is recommended. While there are no
significant changes in adherence, persistence or clinical outcomes in patients
switched from a VKA to a DOAC, an increase in therapy satisfaction has been
reported.
DOAC therapy is not recommended for all patients with atrial
fibrillation. For instance, warfarin is the recommended anticoagulant for
patients with atrial fibrillation who have mechanical heart valves.
Rate versus rhythm
control
There are two ways to approach atrial fibrillation using
medications: rate control and rhythm control. Both methods have similar
outcomes. Rate control lowers the heart rate closer to normal, usually 60 to
100 bpm, without trying to convert to a regular rhythm. Rhythm control tries to
restore a normal heart rhythm in a process called cardioversion and maintains
the normal rhythm with medications. Studies suggest that rhythm control is more
important in the acute setting AF, whereas rate control is more important in
the chronic phase.
The risk of stroke appears to be lower with rate control
versus attempted rhythm control, at least in those with heart failure. AF is
associated with a reduced quality of life, and, while some studies indicate
that rhythm control leads to a higher quality of life, some did not find a
difference.
Neither rate nor rhythm control is superior in people with
heart failure when they are compared in various clinical trials. However, rate
control is recommended as the first-line treatment regimen for people with
heart failure. On the other hand, rhythm control is only recommended when
people experience persistent symptoms despite adequate rate control therapy.
In those with a fast ventricular response, intravenous
magnesium significantly increases the chances of achieving successful rate and
rhythm control in the urgent setting without major side-effects. A person with
poor vital signs, mental status changes, pre-excitation, or chest pain often
will go to immediate treatment with synchronized DC cardioversion. Otherwise,
the decision of rate control versus rhythm control using medications is made.
This is based on several criteria that include whether or not symptoms persist
with rate control.
Rate control
Rate control to a target heart rate of fewer than 110 beats
per minute is recommended in most people. Lower heart rates may be recommended
in those with left ventricular hypertrophy or reduced left ventricular
function. Rate control is achieved with medications that work by increasing the
degree of the block at the level of the AV node, decreasing the number of
impulses that conduct into the ventricles. This can be done with:
Beta blockers
(preferably the "cardioselective" beta blockers such as metoprolol,
bisoprolol, or nebivolol)
Non-dihydropyridine
calcium channel blockers (e.g., diltiazem or verapamil)
Cardiac glycosides (e.g., digoxin) – have less use, apart
from in older people who are sedentary. They are not as effective as either
beta-blockers or calcium channel blockers.
Patients with chronic AF are recommended to take either beta
blockers or calcium channel blockers.
In addition to these agents, amiodarone has some AV node
blocking effects (in particular when administered intravenously) and can be
used in individuals when other agents are contraindicated or ineffective
(particularly due to hypotension).
Cardioversion
Cardioversion is the attempt to switch an irregular
heartbeat to a normal heartbeat using electrical or chemical means.
Electrical cardioversion involves the restoration of normal
heart rhythm through the application of a DC electrical shock. The exact
placement of the pads does not appear to be important.
Chemical cardioversion is performed with medications, such
as amiodarone, dronedarone, procainamide (especially in pre-excited atrial
fibrillation), dofetilide, ibutilide, propafenone, or flecainide.
After successful cardioversion, the heart may be stunned,
which means that there is a normal rhythm, but the restoration of normal atrial
contraction has not yet occurred.
Surgery
Ablation
Catheter ablation (CA) is a procedure performed by an
electrophysiologist, a cardiologist who specializes in heart rhythm problems,
to restore the heart's normal rhythm by destroying, or electrically isolating,
specific parts of the atria. A group of cardiologists led by Dr. Haïssaguerre
from Bordeaux University Hospital noted in 1998 that the pulmonary veins are an
important source of ectopic beats, initiating frequent paroxysms of atrial
fibrillation, with these foci responding to treatment with radio-frequency
ablation. Most commonly, CA electrically isolates the left atrium from the
pulmonary veins, where most of the abnormal electrical activity promoting
atrial fibrillation originates. CA is a form of rhythm control that restores
normal sinus rhythm and reduces AF-associated symptoms more reliably than antiarrhythmic
medications.
Electrophysiologists generally use two forms of catheter
ablation—radiofrequency ablation, or cryoablation. In young people with
little-to-no structural heart disease where rhythm control is desired and
cannot be maintained by medication or cardioversion, radiofrequency catheter
ablation or cryoablation may be attempted and may be preferred over several years
of medical therapy. Although radiofrequency ablation has become an accepted
intervention in selected younger people and may be more effective than
medication at improving symptoms and quality of life, there is no evidence that
ablation reduces all-cause mortality, stroke, or heart failure. Some evidence
indicates CA may be particularly helpful for people with AF who also have heart
failure. AF may recur in people who have undergone CA and nearly half of people
who undergo it will require a repeat procedure to achieve long-term control of
their AF.
In general, CA is more successful at preventing AF
recurrence if AF is paroxysmal as opposed to persistent. As CA does not reduce
the risk of stroke, many are advised to continue their anticoagulation.
Possible complications include common, minor complications such as the
formation of a collection of blood at the site where the catheter goes into the
vein (access site hematoma), but also more dangerous complications including
bleeding around the heart (cardiac tamponade), stroke, damage to the esophagus
(atrio-esophageal fistula), or even death. Use of pulsed field ablation as a
non-thermal method of inducing electroporation avoids damage to the phrenic
nerve, esophagus, and blood vessels, while being at least as effective as
thermal ablation methods.
A hybrid convergent procedure has been developed which
combines endocardial ablation with epicardial ablation, which can reduce AF
recurrence to less than 5% for over one year. The epicardial ablation is
performed first, with a minimally invasive surgical approach.
Maze procedure
An alternative to catheter ablation is surgical ablation.
The maze procedure, first performed in 1987, is an effective invasive surgical
treatment that is designed to create electrical blocks or barriers in the atria
of the heart. The idea is to force abnormal electrical signals to move along
one, uniform path to the lower chambers of the heart (ventricles), thus restoring
the normal heart rhythm. People with AF often undergo cardiac surgery for other
underlying reasons and are frequently offered concomitant AF surgery to reduce
the frequency of short- and long-term AF. Concomitant AF surgery is more likely
to lead to the person being free from atrial fibrillation and off medications
long-term after surgery and Cox-Maze IV procedure is the gold standard
treatment. There is a slightly increased risk of needing a pacemaker following
the procedure. Less invasive modifications of the maze procedure have been
developed, designated as minimaze procedures.
Left atrial appendage
occlusion
There is growing evidence that left atrial appendage
occlusion therapy may reduce the risk of stroke in people with non-valvular AF
as much as warfarin. The addition of left atrial appendage isolation to
catheter ablation has reduced AF recurrence by 80% in patients with persistent
AF.
After surgery
After catheter ablation, people are moved to a cardiac
recovery unit, intensive care unit, or cardiovascular intensive care unit where
they are not allowed to move for 4–6 hours. Minimizing movement helps prevent
bleeding from the site of the catheter insertion. The length of time people
stay in the hospital varies from hours to days. This depends on the problem,
the length of the operation, and whether or not general anesthetic was used. Additionally,
people should not engage in strenuous physical activity – to maintain a low
heart rate and low blood pressure – for around six weeks.
AF often occurs after cardiac surgery and is usually
self-limiting. It is strongly associated with age, preoperative hypertension,
and the number of vessels grafted. Measures should be taken to control
hypertension preoperatively to reduce the risk of AF. Also, people with a
higher risk of AF, e.g., people with pre-operative hypertension, more than
three vessels grafted, or greater than 70 years of age, should be considered
for prophylactic treatment. Postoperative pericardial effusion is also
suspected to be the cause of atrial fibrillation. Prophylaxis may include
prophylactic postoperative rate and rhythm management. Some authors perform
posterior pericardiotomy to reduce the incidence of postoperative AF. When AF
occurs, management should primarily be rate and rhythm control. However,
cardioversion may be used if the patient is hemodynamically unstable, highly
symptomatic, or AF persists for six weeks after discharge. In persistent cases,
anticoagulation should be used.
Prognosis
Atrial fibrillation can progress from infrequent occurrences
to more frequent occurrences, ultimately becoming permanent. Some cases do not
progress, especially among patients with a healthy lifestyle.
Many mechanisms contribute to cardiac remodeling leading to
a worsening of atrial fibrillation, including fibrosis, fatty infiltration,
amyloidosis, and ion channel modifications. Fatty infiltration helps explain
why obesity is a risk factor for atrial fibrillation in one fifth of patients.
Atrial fibrillation increases the risk of heart failure by
11 per 1000, kidney problems by 6 per 1000, death by 4 per 1000, stroke by 3
per 1000, and coronary heart disease by 1 per 1000. Women have a worse outcome
overall than men. Evidence increasingly suggests that atrial fibrillation is
independently associated with a higher risk of developing dementia.
Blood clots
Prediction of embolism
Among Danish men aged 50, with no risk factors, the 5-year
risk of stroke was 1.1% and with AF alone 2.5%. For women the risks were
slightly less, 0.7% and 2.1%. For men aged 70, the 5-year risk of stroke was
4.8% and with AF alone 6.8%. For women aged 70 the risk was again lower than
for men, 3.4% with no added risk factor and 8.2% with AF.
Determining the risk of an embolism causing a stroke is
important for guiding the use of anticoagulants. The most accurate clinical
prediction rules are:
CHADS2
CHA2DS2-VASc score
Both the CHADS2 and the CHA2DS2-VASc score predict future
stroke risk in people with A-fib with CHA2DS2-VASc score being more accurate.
The addition of blood based biomarkers such as NT-proBNP and neurofilament
light chain improves risk prediction significantly. Some that had a CHADS2
score of zero had a CHA2DS2-VASc score of three, with a 3.2% annual risk of
stroke. Thus, a CHA2DS2-VASc score of zero is considered very low risk.
Mechanism of thrombus
formation
In atrial fibrillation, the lack of an organized atrial
contraction can result in some stagnant blood in the left atrium (LA) or left
atrial appendage (LAA). This lack of movement of blood can lead to thrombus
formation (blood clotting). If the clot becomes mobile and is carried away by
the blood circulation, it is called an embolus. An embolus proceeds through
smaller and smaller arteries until it plugs one of them and prevents blood from
flowing through the artery. This process results in end organ damage due to the
loss of nutrients, oxygen, and the removal of cellular waste products. Emboli
in the brain may result in an ischemic stroke or a transient ischemic attack
(TIA).
More than 90% of cases of thrombi associated with
non-valvular atrial fibrillation evolve in the left atrial appendage. However,
the LAA lies in close relation to the free wall of the left ventricle, and thus
the LAA's emptying and filling, which determines its degree of blood
stagnation, may be helped by the motion of the wall of the left ventricle if
there is good ventricular function.
Dementia
Atrial fibrillation has been independently associated with a
higher risk of developing cognitive impairment, vascular dementia, and
Alzheimer disease and with elevated levels of neurofilament light chain in
blood, a biomarker indicating neuroaxonal injury. Several mechanisms for this
association have been proposed, including silent small blood clots (subclinical
microthrombi) traveling to the brain resulting in small ischemic strokes
without symptoms, altered blood flow to the brain, inflammation, clinically
silent small bleeds in the brain, and genetic factors. Tentative evidence
suggests that effective anticoagulation with direct oral anticoagulants or
warfarin may be somewhat protective against AF-associated dementia and evidence
of silent ischemic strokes on MRI but this remains an active area of
investigation.
Epidemiology
Atrial fibrillation is the most common arrhythmia and
affects more than 33 million people worldwide. In Europe and North America, as
of 2014, it affects about 2% to 3% of the population. This is an increase from
0.4 to 1% of the population around 2005. In the developing world, rates are
about 0.6% for males and 0.4% for females. The number of people diagnosed with
AF has increased due to better detection of silent AF and increasing age and
conditions that predispose to it.
It also accounts for one-third of hospital admissions for cardiac
rhythm disturbances, and the rate of admissions for AF has risen in recent
years. AF is the cause for 20% to 30% of all ischemic strokes. After a
transient ischemic attack or stroke, about 11% are found to have a new diagnosis
of atrial fibrillation. 3% to 11% of patients with AF have structurally normal
hearts. Approximately 2.2 million individuals in the United States and 4.5
million in the European Union have AF.
The number of new cases each year of AF increases with age.
In people older than 80 years, it affects about 8%. In contrast, in younger
people the prevalence is estimated to be 0.05% and is associated with
congenital heart disease or structural heart disease in this demographic. As of
2001, it was anticipated that in developed countries, the number of people with
atrial fibrillation was likely to increase during the following 50 years, due
to the growing proportion of elderly people.
Gender
Atrial fibrillation is more common in men than in women when
reviewed in European and North American populations. In developed and
developing countries, there is also a higher rate in men than in women. The
risk factors associated with AF are also distributed differently according to
gender. In men, coronary disease is more frequent, while in women, high
systolic blood pressure and valvular heart disease are more prevalent.
Ethnicity
Rates of AF are lower in populations of African descent than
in populations of European descent. African descent is associated with a
protective effect for AF, due to the lower presence of SNPs with guanine
alleles. European ancestry has more frequent mutations. The variant rs4611994
for the gene PITX2 is associated with risk of AF in African and European
populations. Hispanic and Asian populations have a lower risk of AF than
European populations. The risk of AF in non-European populations is associated
with characteristic risk factors of these populations, such as hypertension.
Young people
Atrial fibrillation is an uncommon condition in children but
sometimes occurs in association with certain inherited and acquired conditions.
Congenital heart disease and rheumatic fever are the most common causes of
atrial fibrillation in children. Other inherited heart conditions associated
with the development of atrial fibrillation in children include Brugada
syndrome, short QT syndrome, Wolff Parkinson White syndrome, and other forms of
supraventricular tachycardia (e.g., AV nodal reentrant tachycardia). Adults who
survived congenital heart disease have an increased risk of developing AF. In
particular, people who had atrial septal defects, Tetralogy of Fallot, or
Ebstein's anomaly, and those who underwent the Fontan procedure, are at higher
risk with prevalence rates of up to 30% depending on the heart's anatomy and
the person's age.
History
Because the diagnosis of atrial fibrillation requires
measurement of the electrical activity of the heart, atrial fibrillation was not
truly described until 1874, when Edmé Félix Alfred Vulpian observed the
irregular atrial electrical behavior that he termed "fremissement fibrillaire" in dog hearts. In the mid-18th
century, Jean-Baptiste de Sénac made note of dilated, irritated atria in people
with mitral stenosis. The irregular pulse associated with AF was first recorded
in 1876 by Carl Wilhelm Hermann Nothnagel and termed "delirium cordis", stating that "[I]n this form of arrhythmia the heartbeats follow each other in
complete irregularity. At the same time, the height and tension of the
individual pulse waves are continuously changing". Correlation of
delirium cordis with the loss of atrial contraction, as reflected in the loss of
waves in the jugular venous pulse, was made by Sir James MacKenzie in 1904.
Willem Einthoven published the first ECG showing AF in 1906. The connection
between the anatomic and electrical manifestations of AF and the irregular
pulse of delirium cordis was made in 1909 by Carl Julius Rothberger, Heinrich
Winterberg, and Sir Thomas Lewis.
Other animals
Atrial fibrillation occurs in other animals, including cats,
dogs, and horses. Unlike humans, dogs rarely develop the complications that
stem from blood clots breaking off from inside the heart and traveling through
the arteries to distant sites (thromboembolic complications). Cats rarely
develop atrial fibrillation but appear to have a higher risk of thromboembolic
complications than dogs.
Cats and dogs with atrial fibrillation often have underlying
structural heart disease that predisposes them to the condition. The
medications used in animals for atrial fibrillation are largely similar to
those used in humans. Electrical cardioversion is occasionally performed in
these animals, but the need for general anesthesia limits its use. Standardbred
horses appear to be genetically susceptible to developing atrial fibrillation.
Horses that develop atrial fibrillation often have minimal or no underlying
heart disease and the presence of atrial fibrillation in horses can adversely affect
physical performance.
No comments:
Post a Comment