Atrial fibrillation
Def: AF is irregular atrial rhythm or irregular supera ventricular arrhythmia
The normal range for a heart rate is 60 to 100 beats a minute
.
* Instead of a coordinated contraction, the atrial contractions are irregular, disorganized, chaotic, and very rapid. The atria may contract at a rate of 400-600 per minute.
* These irregular impulses reach the AV node, but not all of them pass the AV node. Therefore, the ventricles beat slower, often at rates of 110-180 beats per minute in an irregular rhythm.
, the heart's
two small upper chambers (the atria) instead of beating effectively. Blood isn't pumped completely out of them, so it may clot. If a piece of a blood clot in the atria leaves the heart and becomes lodged in an artery in the brain, a stroke results
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The American College of Cardiology/
American Heart Association/European Society
of Cardiology (ACC/AHA/ESC)
define the following categories for
atrial fibrillation :
:
*Recurrent: Two or more episodes of Afib
*Paroxysmal: Recurrent Afib that terminates
spontaneously (usually within 7days)
* Persistent: Afib that is sustained (does not
spontaneously resolve) for longer than 7
days
need medication or DC shock
*Permanent: Afib that lasts longer than
1 year
need surgery not respond to drugs
*Lone Afib: Occurs in a patient:
○ Younger than 60 years of age
○ Without evidence of cardiac or pulmonary
disease
causes:
heart failure, ischemia, hyperthyroidism ,hypertension , , valvular heart dses. pul. Embolism D.M, lvf , sinus sick
syndrom, pneumonia, after cardiac surgery , previous stroke
Af….. results in the loss of atrial systole (causing
decreased ventricular filling)
lower cardiac output.
Mechanism:
Af is due to enhance
automaticity of atrial foci or the presence of
Foci of enhanced automaticity:
○ Are usually located in the superior pulmonary
veins.
○ May also be located in the right atrium,
superior vena cava, or coronary sinus.
symptoms:
asympomatic
chest pain
palpitation
dysnea
fainting
lightheadeness
decrease blood pressure
signs :
irregularly irregular pulse
1st heart sound variable intensity
tests:
1-ECG
abscent p- wave
irregular QRS wave
there is irregular "f" waves or fibrillatory waves
2-x- ray …………….to see if ther is enlargement of the heart
3- echo…….to detect LVH ,mitral valve dse , lt. atrial enlargement
4-Holter monitor. A Holter monitor is a portable ECG device that you wear for a day or more to record your heart's electrical activity during your daily routine.
5- blood tests….as
a-cardiac enzymes….
b- prothromin time
c- INR
d-sodium and potassium level
e- stress test
6-Transesophageal Echocardiography (TEE)
The major role of TEE is to assess for left atrial
or left atrial appendage thrombus. This may be
useful to determine whether there is an atrial
thrombus in patients with ischemic stroke, or
prior to cardioversion
complication :
- Stroke. In atrial fibrillation, the chaotic rhythm may cause blood to pool in your heart's upper chambers (atria) and form clots. If a blood clot forms, it could dislodge from your heart and travel to your brain. There it might block blood flow, causing a stroke.
Heart failure. Atrial fibrillation, especially if not controlled, may weaken the heart, leading to heart failure — a condition in which your heart can't circulate enough blood to meet your body's needs.
treatment:
Treatment of AF is designed to:
- Prevent blood clots from forming, and reduce the risk for stroke.
- . Rate control is important because it allows the ventricles enough time to completely fill with blood. With this approach, the irregular heart rhythm continues, but the person feels better and has fewer symptoms.
- .. Rhythm control…. Restore the heart to a normal rhythm ….. allows the atria and ventricles to work together again to efficiently pump blood to the body.
- Treat any underlying disorder that's causing or raising the risk of AF-for example, hyperthyroidism.
Acute AF :< 48 h*
1-oxygen
2- cardioversion,
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cardioversion
there is 2 types:
electrical or pharmacological cardioversion:
Electrical Cardioversion:
The patient is asked to fast
overnight and is given conscious sedation prior
to the procedure. ..electrode pads
or paddles are placed either in the anterior–
posterior (sternum anteriorly and left subscapular
position posteriorly) or anterior–lateral (right
subclavicular anteriorly and ventricular apex
laterally) positions.
For monophasic waveform, an initial energy
setting of 200 J, synchronized with the QRS
complex should be used. The energy may be
increased by 100 J for additional shocks, to a
maximum of 400 J. A minimum of 1 minute
should elapse between successive shocks to
minimize myocardial damage
phamacological cardioversion
Amiodaron:
5 mg/kg over 1hr then 900mg over 24h via central line
max. dose 1.2 gm per 24 hr
or
200 mg/8 hr for 1 week then
200mg/12hr for 1 week then
200 mg/24 hr maintainance
3- anti coagulant
start full anticoagulation with "LMNH" eg: clexan to keep options open for cardioversion
cardioversion …perfomed with out anti coagulant if we performed transoesophageal echo and it show no cardiac thrombus
4- B.B and CCB
a- metoprolol" 50 mg/ 12 h" po
or
"2.5-5 mg" i.v over 2 min
may repeat after 5 min
max. dose 15 mg
b-verapamil "40- 120 mg"po
or
5 – 10 mg i.v over 2 min
can repeated after 5 min
Once rate control is achieved, may give
continuous infusion of 0.125 mg/min to
maintain rate control
c- deltiazem " 60-120 mg "po
or
○ For initial dose, give 0.25 mg/kg body
weight IV over 2 min.
○ After 15 min, repeat with 0.35 mg/kg body
weight given over 2 min, if necessary.
○ In patients who respond to either 1 or 2 IV
bolus doses, start maintenance infusion of
_5 to 15 mg IV per hour.
Digoxin-
- 0.5–1 mg i.v , 0.125 mg–0.5 mg o.d.
Chronic AF:*
achieved with oral doses of beta-blockers,
calcium channel blockers, digoxin, or a combination
of the previously mentioned drugs:
_ Metoprolol: 25–100 mg orally twice a day
_ Atenolol: 25–100 mg orally daily
_ Verapamil: 40–120 mg orally three times a
day
_ Diltiazem: 30–90 mg orally four times a day
_ Digoxin: 0.25mg orally every 2 hr up to 1.5mg
total loading dose, then 0.125–0.375 mg orally
daily. Digoxin levels should be monitored at
about 1 week when steady levels are achieved,
or when digoxin toxicity is suspected.
In patients with rapid ventricular rate despite
treatment with these medications, amiodarone
may be used for rate control:
- don't give BB with diltiazem or verapamil without expert advice" for the risk of brady cardia"
_ Amiodarone: 800 mg orally daily for 1 week,
followed by 600 mg daily for 1 week, then
400 mg daily for 4–6 weeks.
_ Amiodarone: 200 mg orally daily as maintenance
may then be continued after the
loading regimen is completed.
Prevention of Thromboembolism
Use of aspirin or warfarin with a target International
Normalized Ratio (INR) of at least 2.0 to
3.0 lowers the risk of thromboembolic events in
patients with Afib. Risk factors for thromboembolism
_ Aspirin 325 mg orally daily
_ Warfarin therapy should be offered, in the
absence of contraindications, for patients
who do not fall into these categories.
Specifically,
○ Target INR 2.0–3.0
CHADS2 scoring system …..detemine the need of coagulation
_ Congestive heart failure—1 point
_ Hypertension—1 point
_ Age >75—1 point
Diabetes mellitus—1 point
history of
thromboembolism—2 points
Therapy should be administered as follows:
* score 0…….no need for anticoagulation
- for score 1 ….warfarin or asprin may be used according to ptn risk factors
- for score 2… warfarin is needed
for ptn < 65 asprin 57- 300 mg daily
Anticoagulation and Cardioversion
*Patients with Af of less than 48 hours’ duration
and no risk factors for thromboembolism :
do not need 3 to 4 weeks of anticoagulation
prior to cardioversion. . these
patients should receive heparin (unfractionated or
low molecular weight) before and during cardioversion,
and anticoagulation (usually with warfarin)
for at least 4 weeks after cardioversion..
*Af of less than 48 hours’ duration in a
patient with significant risk factors :for thromboembolism,
including prior thromboembolic
event, valvular heart disease, or heart failure,
should receive 3 to 4 weeks of warfarin therapy
prior to cardioversion. These patients should be
maintained on warfarin for at least 4 weeks after cardioversion
*Afib of unknown or greater than 48 hours’
duration may be managed with either:
_ Prolonged anticoagulation
:
Patient is given 3–4 weeks of warfarin
therapy, with a target INR of 2.5 (goal
2.0–3.0) prior to cardioversion.
○ Anticoagulation should be maintained for
at least 4 weeks after cardioversion.
_ TEE-based strategy:
○ Heparin should be started and/or
warfarin initiated for anticoagulation.
○ Transesophageal echocardiogram should
then be performed.
* If a clot is visualized,
or if a clot cannot be excluded, 3 to 4
weeks of anticoagulation should be given
prior to cardioversion
*If a clot is excluded, cardioversion
may be performed.
○ Anticoagulation should be maintained for a
minimum of 4 weeks after cardioversion.
*catheter ablation:
used in ptn which not respond to treatment
Radiofrequency catheter ablation
الفيديو دة بيشرح يعنى اية بالظبطhttp://www.youtube.com/watch?v=MY0MI_BWc90&feature=related
catheter inserted into a vein in the leg and until it reach the heart and the specific place and by the electrica; tip of the catheter it send radio energy to destroy the area causing AF
Atrioventricular (AV) node ablation
. apply radiofrequency energy to the pathway connecting the upper and lower chambers of your heart (AV node) through a long, thin tube (catheter) to destroy this small area of tissue.
This prevents the atria from sending electrical impulses to the ventricles. The atria continue to fibrillate, , and anticoagulant medication is still required.
A pacemaker is then implanted to establish a normal rhythm. After AV node ablation, you'll need to continue to take anticoagulation medications to reduce the risk of stroke, because your heart rhythm is still atrial fibrillation.
Surgical maze procedure.
The maze procedure is done during an open-heart surgery. Using a scalpel, doctors create several precise incisions in the atrium to create scar tissue. Because scar tissue doesn't carry electricity, it interferes with electrical impulses that cause atrial fibrillation.
prefrences
://www.mayoclinic.com
oxford clinical medicin
http://www.americanheart.org
aryl. Goldburger electrocardiography
http://emedicine.medscape.com
kumar and clark clinical medicine
http://www.patient.co.uk
http://www.emedicinehealth.com
http://emedicine.medscape.com/
http://www.webmd.com/heart-disease/
http://www.news-medical.net
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