Hello, today we will discuss Atrial fibrillation.
Atrial fibrillation is often asymptomatic, meaning that you don’t know that you have
it.
However, some may experience symptoms such as palpitations,
weakness, Dyspnea i.e. difficulty in breathing,
presyncope which is a state of lightheadedness, muscular weakness, blurred vision, and feeling
faint Atrial thrombi can form, which may dislodge
and result in an embolic stroke An irregularly, irregular jugular venous pulse
with loss of the a wave can be felt when palpated in the neck region.
And finally, a pulse deficit, which is a difference between heart beats and the peripheral pulsations.
This may be present because left ventricular stroke volume is not always sufficient to
produce a peripheral pressure wave at fast ventricular rates.
Diagnosis of atrial fibrillation is mainly made by ECG.
The ECG findings in atrial fibrillation include: Absence of P waves
Presence of fibrillatory waves, so called f waves between QRS complexes; These f waves
are irregular in timing as well as in morphology; Irregularly irregular R-R intervals is another
ECG finding.
The R-R interval is the interval from the peak of one QRS complex to the peak of the
next Other investigations that aid in the diagnosis
of Atrial fibrillation include Echocardiography and thyroid function tests which are especially
important in the initial evaluation.
Echocardiography is done to assess Structural heart defects
Such as left atrial enlargement, left ventricular wall motion abnormalities
suggesting past or present ischemia, valvular disorders,
And cardiomyopathy) It is also important to identify risk factors
for stroke Such as atrial thrombus,
Or a complex aortic plaque).
Atrial thrombi are more likely to be found in the atrial appendages,
where they are best detected by transesophageal rather than transthoracic echocardiography.
Thyroid Function tests can be done to find out if you have hyperthyroidism.
Because Hyperthyroidism patients have a higher risk of getting atrial fibrillation.
Atrial fibrillation can be classified into 4 types
Paroxysmal atrial fibrillation, which is an episode of Atrial fibrillation that terminates
spontaneously or with intervention in less than seven days.
This means that there is a possibility for these episodes to recur.
Persistent atrial fibrillation is when an episode of atrial fibrillation lasts for more
than one week.
Long-standing persistent atrial fibrillation refers to continuous atrial fibrillation that
lasts longer than 1 yr, but there is still the possibility of restoring sinus rhythm.
Lastly, Permanent atrial fibrillation refers to patients in which efforts to restore normal
sinus rhythm have failed.
The longer the atrial fibrillation is present, the less likely is spontaneous conversion
and the more difficult is cardioversion because of atrial remodeling.
The most common causes of atrial fibrillation are
Hypertension, Coronary artery disease
Cardiomyopathy, Mitral or tricuspid valvular disorders
Hyperthyroidism, Binge alcohol drinking which may give rise
to holiday heart syndrome.
This is an irregular heartbeat pattern presented in individuals who are otherwise healthy and
sometimes follow excessive alcohol consumption.
Less common causes of atrial fibrillation include, Pulmonary embolism
Atrial septal defects and other congenital heart defects,
Chronic obstructive Pulmonary Disease (COPD) Myocarditis which refers to the inflammation
of the heart muscle.
And Pericarditis, the inflammation of the pericardium
Now, let’s move onto the treatment of atrial fibrillation.
If a significant underlying disorder is suspected, patients with new-onset atrial fibrillation
may benefit from hospitalization, but those with recurrent episodes do not require hospitalization
unless other symptoms suggest the need for it.
Once the causes have been managed, treatment of Atrial fibrillation focuses on ventricular
rate control.
Rate control can be achieved with drugs or AV node ablation.
Patients with Atrial fibrillation of any duration require rate control (typically to < 100 beats/min
at rest) to control their symptoms.
For acute paroxysms of rapid rates like 140 to 160 beats/min, intravenous AV node blockers
are used.
Rate control is also important to prevent tachycardia-induced cardiomyopathy.
A word of Caution: AV node blockers should not be used in patients with Wolff-Parkinson-White
syndrome when an accessory AV pathway is involved.
This is indicated by wide QRS duration.
These drugs increase frequency of conduction via the bypass tract, possibly causing ventricular
fibrillation.
Ventricular fibrillation is the most serious cardiac rhythm disturbance.
The lower chambers quiver and the heart can't pump any blood, causing cardiac arrest.
Beta-blockers (for example, metoprolol and esmolol) are also preferred in acute paroxysms,
if excess catecholamines are suspected like in thyroid disorders and exercise-triggered
cases, Nondihydropyridine calcium channel blockers for example verapamil and diltiazem
are also effective.
Digoxin is the least effective but may be preferred if heart failure is present.
These drugs may be used orally for long-term rate control.
When beta-blockers, nondihydropyridine calcium channel blockers, and digoxin—separately
or in combination—are ineffective, amiodarone may be required.
Prevention of thromboembolism during rate control.
If Atrial fibrillation has been present for more than 48 hours, patients should typically
be given an oral anticoagulant.
This is because regardless of the method used for cardioversion, it increases the risk of
thromboembolism..
Anticoagulation should be maintained for more than 3 weeks before conversion
or can be given for a shorter time before conversion if transesophageal echocardiography
(TEE) does not show left atrial thrombus.
Rhythm control can be achieved with synchronized cardioversion, drugs, or ablation.
For acute conversion, synchronized cardioversion or drugs can be used.
Drugs for conversion of atrial fibrillation to sinus rhythm include class Ia, Ic, and
III antiarrhythmic drugs.
These drugs should not be used until rate has been controlled by a beta-blocker or nondihydropyridine
calcium channel blocker.
These converting drugs are also used for long-term maintenance of sinus rhythm.
The class Ia antiarrhythmic drugs include procainamide, quinidine and disopyramide.
Class Ic antiarrhythmic drugs include flecainide, and propafenone.
Class III antiarrhythmic drugs include amiodarone, dofetilide, dronedarone, ibutilide, and sotalol.
It is important to continue anticoagulation for at least 4 weeks after cardioversion.
Many patients may need chronic anticoagulation.
cardioversion may be done without prior anticoagulation if the patient has nonvalvular Atrial fibrillation
and is not at high risk of a thromboembolic event.
Ablation is a surgical procedure which works by scarring or destroying heart tissue that
is responsible for the bad rhythm.
Ablation is done for patients that can’t take rate-controlling drugs.
Ablation procedures that isolate the pulmonary veins from the left atrium can prevent Atrial
fibrillation without causing AV block.
This procedure is often reserved for younger patients with drug-resistant Atrial fibrillation
who have no significant structural heart disease.
Long-term measures to prevent stroke are taken for certain patients with atrial fibrillation.
Patients with rheumatic mitral stenosis and those with mechanical artificial heart valves
are at a high risk of stroke.
Therefore these patients are treated with warfarin.
We can use 2 tools to evaluate risk factors for stroke and bleeding.
The CHADS VAS score is used to evaluate the risk of stroke, and the HAS-BLED is used to
evaluate the risk of bleeding.
A high CHADS-VASc score means an increased risk of stroke.
The acronym CHADS VAS means, C for Congestive heart failure, H for Hypertension, A for Age
more than 75, D for Diabetes, S for Stroke, V for Vascular disease, A for age 65 to 74,
and S for female sex.
The number 2 next to A and S just means that we give 2 points for those risk factors.
One point is given for every risk factor, except for stroke and when the patient is
more than 75 years old.
These are given 2 points.
Note that when the patient is 65-74, only 1 point is given, and when the patient is
less than 65, then no point is given.
Here is a picture showing the CHADS VAS score.
These are the risk factors for stroke.
Starting from the upper left picture, we have Congestive heart failure, Hypertension, Age
more than 75 which is given 2 points, and age 65-74 which is given only 1 point.
Then in the lower left picture we have diabetes, then stroke which is also given 2 points.
Then we have vascular disease and finally female sex.
In situations when antithrombotic therapy is absolutely contraindicated, the left atrial
appendage may be surgically ligated or closed with a transcatheter device.
The CHADS VAS score dealt with the risk of stroke.
But the HAS-BLED score deals with the risk of bleeding.
The acronym HAS-BLED means, H for Hypertension, A for abnormal renal and liver function, S
for stroke, B for bleeding, L for labile INR, E for elderly and D for drugs or alcohol.
One point is given for each risk factor.
These are the risk factors for bleeding.
Starting from the upper left picture, we have Hypertension, Kidney disease, Liver disease,
stroke, . Then in the lower left picture we have bleeding disease, patients over older
65 years of age, alcohol and anticoagulation medications like warfarin.
All these risk factors are given 1 point each.
Thanks for listening