Acute Setting Management
1. Hemodynamically unstable:
- Electric cardioversion (defibrillation)
- Start with 150-200 joules biphasic waveform in synchrony with
the R wave
- IV Heparin
- 60 units/kg loading dose followed by 12 units/kg per hour to
maintain an aPTT of approximately 1.5-2 times the control
value
- Low molecular weight heparin (LMWH) may also be
used
- Atropine (1 mg IV) should be readily available
to treat prolonged pauses
Note: Anticoagulation may or may not be used in
this setting. Patients with known AF/AFL <48hr may undergo
cardioversion without prior or subsequent anticoagulation. However,
prior anticoagulation is advised for AF/AFL of unknown duration (or
≥48hr) or if patient is at high risk of stroke (mechanical or
valvular heart disease, previous TIA or stroke). Such patients
require ≥4 weeks of oral anticoagulation post cardioversion.
Ref: Ian G. Stiell et al. Canadian Journal of
Cardiology 2011; 27: 38-46
2. Hemodynamically stable (atrial fibrillation
or
flutter duration <48 hours)
In selected patients, initial therapy with rate slowing agent is
acceptable while waiting for spontaneous cardioversion, such as
- Beta blockers
- Calcium channel blockers (CCBs)
- Digoxin (second line therapy)
Ref: Ian G. Stiell et al. Canadian Journal of
Cardiology 2011; 27: 38-46.
Caveat: In special circumstances like
Wolff-Parkinson-White syndrome (presence of an extra, abnormal
electrical pathway in the heart leading to tachycardia), avoid beta
blockers, CCBs, digoxin, and adenosine; consider intravenous
anti-arrhythmic e.g.
- Procainamide: 15-17 mg/kg IV over 60 min slow
infusion
- Ibutilide: 1-2 mg IV over 10-20 min; pretreat
with MgSO4 1-2 mg IV
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If patient is still in atrial fibrillation, cardioversion
without prior anticoagulation may be considered in low risk
patients <48h
a) Pharmacological cardioversion:
Class Ia:
- Procainamide: 15-17 mg/kg IV over 60 min
Class Ic:
- Propafenone (oral): 450 mg (wt. <70 kg);
600 mg (wt. ≥70 kg)
- Flecainide (oral): 200 mg (wt. <70 kg); 300
mg (wt. ≥70 kg)
Class III:
- Ibutilide: 1-2 mg IV over 10-20 min; pretreat
with MgSO4 1-2 mg IV
Note: Class Ic drugs (propafenone, flecainide )
should be used in combination with AV nodal blocking agents
(beta-blockers or calcium-channel blockers) to avoid paradoxical
increase in ventricular rate due to drug induced conversion of
atrial fibrillation (AF) to atrial flutter (AFL). Class Ic should
also be avoided in patients with structural heart disease.
b) Electrical cardioversion:
Recommended in case of pharmacological cardioversion failure.
- Prophylactic anti-arrhythmic drugs before electrical
cardioversion in emergency department is recommended in order to
decrease early recurrence of AF or AFL and to enhance cardioversion
efficacy
Ref: Ian G. Stiell et al. Canadian Journal of
Cardiology 2011; 27: 38-46
c) Oral anticoagulant (OAC):
- For high risk patients (e.g. valvular heart disease, recent
stroke/TIA) OAC use for 3 weeks prior to cardioversion is
recommended. In addition OAC is recommended for ≥ 4 weeks of post
cardioversion. Antithrombotic therapy with OAC or ASA is then based
on risk of recurrent AF and CHADS2 score
3. Hemodynamically stable (AF or AFL duration
≥48
hours)
- Start with rate slowing agents (beta blockers, CCBs, and
digoxin)
- If there is no optimal response with rate slowing therapy, then
consider cardioversion
- Perform ECHO (TEE or TTE) to exclude thrombus before
cardioversion
- If no thrombus, then start cardioversion
(preferably electric cardioversion) with IV heparin
- Followed by oral anticoagulant (OAC) therapy thereafter for at
least 4 weeks
- If thrombus is present or ECHO is not
available then give OAC (warfarin [INR 2-3] or dabigatran or
rivaroxaban or apixaban) for 3 weeks before and at least 4 weeks
post cardioversion
- Prophylactic treatment with antiarrhythmic drugs is advisable
after cardioversion in high risk patients, in view of high
relapse
Ref: Ian G. Stiell et al. Canadian Journal of
Cardiology 2011; 27: 38-46.
Special considerations:
Cardioversion in patients with implanted pacemakers and
defibrillators
- The electrode paddle should be at least 8 cm away from the
pacemaker battery
- Anteroposterior paddle positioning is recommended
- Biphasic shocks are preferred
- After cardioversion, the device should be evaluated to ensure
normal function
AV junction ablation and implantation of a permanent
pacemaker
- Indicated in symptomatic patients with uncontrolled ventricular
rates during atrial fibrillation despite maximally tolerated
combination pharmacologic therapy
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Maintenance Therapy
- Rate control
- Rhythm control
- Thromboembolic prophylaxis
1) Rate Control
Beta blockers, calcium channel blockers
(CCBs):
- Usually first line rate control agents in most patients without
past history of MI or LV dysfunction
Digoxin:
- IV: 0.5-1 mg; usual dose 0.1-0.4 mg IV once
daily
- Oral: 0.75-1.5 mg PO; usual dose 0.125-0.5 mg
once daily
- Not to be used for initial therapy in
active patients; usually used as initial therapy in patients who
are sedentary or who have left ventricular systolic
dysfunction.
- May be used as adjunct with beta
blockers or CCBs in whom rate control is not achieved.
Amiodarone:
- 400 mg PO TID over 5-7 days, then 400 mg/day over 1 month, then
200 mg/day
- Usually reserved when other means are
not feasible or are insufficient for rate control (because of
adverse effects).
Dronedarone:
- 400 mg PO BID with meals
- Indicated for treatment of patients with non-permanent AF
- Reduces hospitalizations due to AF
- May be used as adjunct with beta-blockers, calcium channel
blockers and used with caution with digoxin, if ventricular rate is
uncontrolled despite therapy
- Requires regular monitoring of liver function
HOWEVER, this agent is now contraindicated in:
- Permanent AF, duration at least 6 month
- Severe heart failure (NYHA stage IV) or unstable hemodynamic
conditions
- Left ventricular ejection fraction (LVEF) <40%
- 2nd or 3rd degree AV block or sick sinus
syndrome (SSS); unless functioning pacemaker present
Catheter ablation:
- AV junction ablation and permanent pacemaker implantation may
be employed in those refractory to maximum combined medical
therapy
- OAC therapy be continued following AF ablation in patients with
- i) CHADS2 score ≥1
- ii) Mechanical heart valve
2) Rhythm Control
Anti-arrhythmic agents in maintenance therapy:
Generally reserved for patients with AF or AFL who remain
symptomatic with rate control therapy or in whom rate control
therapy is unlikely to control symptoms, agents used include:
Propafenone or Flecainide - Class I:
- Used with structurally normal heart
- Fast onset of action
Sotalol - Class III:
- Avoid in decompensated congestive heart failure (CHF)
- Not very effective in converting recent onset AF to sinus
rhythm
Dofetilide - Class III:
Amiodarone - Class I, II, III, and IV:
- Effective but has extensive toxicity
- Used in those with severely depressed LV function
- Usually indicated in patients with recent-onset AF and
structural heart disease
Dronedarone - Class III:
- Initially considered less toxic, but also less effective than
amiodarone and is used to lower side effects with acceptance of
higher recurrence of AF
- Contraindications: Permanent AF/severe heart
failure/LVEF <40% / 2nd or 3rd degree AV
block (as discussed in rate control above)
"Pill in the Pocket" for selected patients with atrial
fibrillation
- Self-treatment with intermittent antiarrhythmic drug therapy
(propafenone or flecainide) is usually recommended; as an
alternative to daily antiarrhythmic therapy, in symptomatic
patients with infrequent long lasting episodes of AF
Caveat: Avoid oral antiarrthymic therapy in
patients with AF/AFL or advanced sinus or AV nodal disease unless
pacemaker or defibrillator has been installed.
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3) Thromboembolic Prophylaxis
(Prevention of thromboembolic complications and bleeding risk)
a) Patients with AF often require prophylaxis
with
anticoagulant therapy, unless contraindicated
Therapeutic choices include:
- IV heparin/LMWH (may be considered for short
term prophylaxis)
- Dabigatran
- Rivaroxaban
- Apixiban
- Warfarin
- Acetylsalicylic acid (ASA)
The therapy in turn is based on clinically relevant thromboembolic
risk factors which are summarized as follows:
Major risk factors are considered:
- Previous stroke, transient ischemic attack (TIA)
- Previous systemic embolism
- Age >65 years
Clinically relevant non-major risks:
- Heart failure or severe to moderate LV systolic dysfunction
(e.g. LVEF <40%)
- Hypertension
- Diabetes mellitus
- Female sex
- Age 65-74 years
- Vascular disease
b) The risk/benefit ratio for patient selection
has
been outlined in number of scales/tools, which
have been summarized in one table for
convenience
c) Based upon the therapeutic bleeding risk
stratification scores (HAS-BLED score) in AF:
- Patients with HAS-BLED Score ≥3 indicates
increased one year bleeding risk on anticoagulation, sufficient
enough to justify caution or more regular review.
d) Special considerations in patient who are
on
prevention of thromboembolic complication:
Subclinical Atrial Fibrillation (SCAF):
- Appears to have a lower risk of stroke as compared to those
with clinical AF
- Uncertainty remains regarding the duration AF above which
stroke risk is increased
- OAC therapy may be considered for patients >65 years or
CHADS2 score >1 with episodes of SCAF lasting > 24
hours, or for shorter episodes in high-risk patients (such as those
with a recent cryptogenic stroke)
Patients on antiplatelet therapy or OAC scheduled for
surgery:
For CHADS2 ≥3 or high risk of stroke (e.g.
prosthetic valve, recent stroke, TIA, rheumatic valve
disease)
- Decision to discontinue antithrombotic agent depends on
advantages and disadvantages of the patient's condition at that
time with other risk factors
- For those on OAC, discontinuation followed by bridging therapy
with LMWH or IV heparin pre-procedure might be an option
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Procedures
1) Electric cardioversion:
- Safe and effective method for quick restoration of sinus
rhythm:
- If AF <48 hrs proceed with cardioversion
- If AF ≥48 hrs or of unknown duration anticoagulant therapy is
suggested (see "Hemodynamically Stable AF or AFL duration 48 hr"
section above)
- Biphasic external defibrillators are preferred
- Start with lower possible dose in small size patient
- Electrode placement positions:
- Anteroposterior electrode placement (more effective)
- Anterolateral placement
- If initial shocks are unsuccessful:
- Reposition electrodes and repeat cardioversion
- Outpatient/ambulatory cardioversion can be undertaken:
- In hemodynamically stable patients with no underlying severe
heart disease
- Post procedure monitoring:
- Blood pressure, heart rate and telemetry for ≥3 hrs
2) Catheter ablation:
- Is chosen as a first line therapy in highly selected patients
with symptomatic paroxysmal AF
- AF ablation should not be considered as an alternative to oral
anticoagulation, and initiation of anticoagulation should not be
delayed in patients with high thromboembolic risks
Potential sites for ablation:
a) Accessory pathway
- Indicated in patients with evidence of ventricular
pre-excitation during AF, such as rapid ventricular rates,
syncope
- Definitive therapy for patients with Wolff-Parkinson-White
syndrome
b) AV node ablation and implantation of a
permanent pacemaker
- For those with uncontrolled ventricular rates refractory to
maximal pharmacologic therapy, a pacemaker and indefinite
anticoagulant therapy is often required
c) Left atrial catheter ablation
- Effective for either paroxysmal or chronic AF
d) Pulmonary vein isolation ablation (PVI
ablation
or PVA)
- Effective in patients who have "paroxysmal" AF
3) Surgical ablation:
Usually reserved for those patients who have failed a catheter
ablation strategy or who have planned concomitant cardiac
surgery.
Procedures usually used are:
- Maze procedure
- Cox Maze III procedure
- Minimally invasive surgical ablation (e.g.)
- Wolf Mini Maze
- Saltman Microwave Mini Maze
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MEDICATIONS
RATE CONTROL:
Beta-adrenergic blocking agents
- ➢ Cardioselective
- Atenolol
- Esmolol
- Metoprolol
- ➢
Non-cardioselective
Mechanism:
- Block Beta receptors
- Decrease heart rate and cardiac output
- Decrease renin release
Dose: Cardioselective
Atenolol:
Atrial fibrillation
- 2.5-5 mg slow IV infusion over 2-5 minute; Max. 10 mg over
10-15 minute
Esmolol:
SVT/Postoperative tachycardia/Hypertension (gradual
control)
- 500 mcg/kg IV over 1 minute; then 50 mcg/kg/minute infusion
over 4 min; Max of 300 mcg/kg/min
- Titration: Increased by 50 mcg/kg/minute (once
in 4 mins) as needed
- Note: If no response within 5 minute, may give
2nd loading dose of 500 mcg/kg over 1 minute, then 100
mcg/kg/minute infusion over 4 minute
Intraoperative tachycardia/Hypertension (immediate
control)
- 1.5 mg/kg IV bolus over 30 sec.; Then 0.15 mg/kg/minute
infusion, if necessary; Max. 0.3 mg/kg/minute
Metoprolol:
Atrial fibrillation/Supraventricular
tachycardia
- Acute treatment: 2.5-5 mg IV every 2-5
minutes; Max. 15 mg over 10-15 minute
- Maintenance (immediate release): 25-100 mg PO
BID
Dose: Non-cardioselective
Propranolol:
Tachyarrhythmias
- Intravenous: 1-3 mg slow IV push every 2-5 mg up to total of 5
mg
- Regular Tablet: 10-30 mg PO QID or TID
Sotalol: (antiarrhythmic agent class III &
II)
- 40-160 mg PO twice daily; usual initial dose can be 80 mg PO
twice daily, if required may go up to 240-320 mg PO per day
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Calcium channel blocking agents
(CCBs)
Mechanisms:
- Blocks calcium influx by binding to the L-type calcium channels
in the heart and in smooth muscle of the peripheral
vasculature
- Decreases intracellular calcium leading to a reduction in
muscle contraction
- Significant reduction in afterload, with no effect on
preload
Dose: Non-Dihydropyridines
Diltiazem:
Supraventricular tachyarrhythmias
- 0.25 mg/kg IV over 2 minute; if desired response not achieved
in 15 minutes, may repeat 0.35 mg/kg IV bolus over 2 minute; then
follow with continuous infusion at 10 mg/hr (range 5-15 mg/hr) for
up to 24 hr, if required
- Note: Infusions >24 hrs or >15 mg/hr are
not recommended
Verapamil:
Chronic atrial fibrillation/PSVT (prophylaxis)
- Immediate-release: 240-480 mg/day PO divided
in 3-4 doses; usual 120-360 mg/day in 3-4 divided doses
Supraventricular tachyarrhythmias
- Dosage: 2.5-5 mg IV over 2 minute; may repeat
5-10 mg IV 15-30 minute after the initial dose if required; Max.
20-30 mg
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RHYTHM CONTROL
Antiarrhythmics
- ➢ Class Ia
- ➢ Class Ic
- ➢ Class III
- Ibutilide
- Amiodarone
- Ibutilide
Mechanisms:
- Complete mechanism of antiarrhythmic action is not known
- Depress Na conductance and block K+ channel →
resultin in increased action potential duration (APD) and effective
refractory period (ERP)
- Ic agents block Na+ channels more potently
than the Ia drugs and has some beta-blockade activity
Dose: Class Ia:
Procainamide:
Atrial Fibrillation
- Initial Loading dose: 15-17 mg/kg slow
infusion over 60 minutes or 100 mg/dose repeated every 5 minutes
(rate not to exceed 50 mg/minute) to a total dose of 1 g
- Maintenance: 1-4
mg/minute IV continuous infusion
- Oral: Initially 1.25 g PO; followed by 0.75 g
PO after 1 hour interval. If there are no change on ECG, give
additional doses of 0.5-1 g every 2 hours until arrhythmia is
interrupted or until toxic effects appear
- Maintenance
(extended-release): Up to 50 mg/kg/day PO in equally
divided doses every 6 hrs starting 2 to 3 hours after the last dose
of conventional tablets
Hemodynamically stable monomorphic VT/Pre-excited atrial
fibrillation (ACLS)
- Loading dose as IV Infusion 20-50 mg/minute Or
100 mg every 5 minutes (rate not to exceed 50 mg/minute), until the
arrhythmia is suppressed, a fall in BP of >15 mmHg occurs,
excessive widening of the QRS complex (≥50%) from baseline or
prolongation of the PR interval occurs, severe adverse effects
appear, or a total dose of 17 mg/kg is given
- Maintenance: Followed by continuous infusion
of 1-4 mg/minute
Dose: Class Ic
Propafenone:
Paroxysmal atrial fibrillation
("Pill-in-the-pocket")
- Weight <70 kg: 450 mg PO
- Weight ≥70 kg: 600 mg PO
- Avoid repeating in ≤24 hrs
Recent onset atrial fibrillation
- 150 mg PO given every 8 hours (total of 450 mg/day). May
increase in 3-4 days interval to 300 mg PO every 12 hours (total of
600 mg/day) and if required may increase dose to 300 mg PO every 8
hours (900 mg/day)
Flecainide:
Prevention of PSVT/Paroxysmal atrial
fibrillation
- 50 mg PO BID, may increase by 50 mg PO BID at 4 day intervals;
Max. 300 mg/day
Paroxysmal atrial fibrillation - "pill-in-the-pocket"
dose
- Weight <70 kg: 200 mg PO daily;
weight ≥70 kg: 300 mg PO daily
Note: Patient must
be on an AV nodal-blocking agent prior to initiation of
antiarrhythmic. No more than one dose during a 24-hour period.
Dose in renal impairment:
- If CrCl <35 ml/minute, initiate 100 mg PO daily
OR 50 mg PO BID: may increase dose at 4 day
intervals cautiously, if needed
Dose: Class III
Ibutilide:
Atrial fibrillation/flutter
- <60 kg: 0.01 mg/kg IV infusion over 10 minutes
- ≥60 kg: 1 mg IV infusion over 10 minutes
Note: May repeat 2nd dose after 10
minutes
Atrial fibrillation/flutter after cardiac
surgery
- <60 kg: 0.005 mg/kg over 10 minute; ≥60 kg: 0.5 mg IV
infusion over 10 minutes
- Note: May repeat one additional time. If
arrthymia terminates discontinue the infusion
Amiodarone:
Atrial fibrillation pharmacologic
cardioversion
- 5-7 mg/kg IV over 30-60 minutes; followed 1.2-1.8 g/day IV
continuous infusion or PO in divided doses until total of 10 g
- Maintenance: 200-400
mg/day in divided or single dose
- Inpatient: 1.2-1.8 g PO daily in divided doses
up to a total of 10 g
- Maintenance: 200-400
mg/day PO in divided or single dose
- Outpatient: 600-800 mg PO in single or divided
dose; up to a total of 10 g
- Maintenance: 200-400
mg/day in divided or single dose
Recurrent atrial fibrillation
- 10 mg/kg/day PO in single or 2 divided doses for 14 days; then
300 mg PO daily for 4 weeks, followed by of 200 mg PO daily for
maintenance OR
- 400 mg PO TID for 5-7 days; then 400 mg /day for 1 month;
followed by 200 mg/day
Dronedarone:
Atrial fibrillation/Flutter
Cardiac Glycoside
Mechanisms:
Exact mechanism of action not known; however, the acceptable
hypothesis is as follows:
- Inhibition of the sodium/ potassium ATPase pump in myocardial
cells results in a transient increase of intracellular sodium,
which in turn promotes calcium influx via the sodium-calcium
exchange pump leading to increased contractility
- There is a direct effect on the
conductivity of A-V node which is delayed; slowing the rate of
origin of impulses from the S-A node. In short heart rate becomes
slow. These effects are largely due to parasympathetic
stimulation
Dose:
Digoxin:
AF + Heart failure
- Acute management: Loading dose 250 mcg IV
(0.25 mg) every 2 hours up to total of 1500 mcg (1.5 mg) in a
day
- Non-acute management: 500 mcg (0.5 mg) PO
daily for 2 day
- Maintenance: 125-375 mcg (0.125-0.375 mg)
IV/PO daily
Supraventricular tachyarrhythmia
Total digitalizing dose (TDD)
- 500-1000 mcg (0.5-1 mg) IV/IM; start with 50% of the TDD, then
one quarter of the TDD in each of 2 subsequent doses at 6-8 hr
intervals
- 750-1500 mcg (0.75-1.5 mg) PO; start with 50% of the total
digitalis dose (TDD), then one quarter of the TDD in each of 2
subsequent doses at 6-8 hr intervals
- Note: Obtain ECG 6
hours after each dose to assess potential toxicity.
Daily maintenance dose
- 125-500 mcg (0.125-0.5 mg) PO daily
- 100-400 mcg (0.1-0.4 mg) PO daily
Note: Intramuscular injections are not preferred
due to severe pain at the sight of injection.
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CARDIOEMBOLIC PROPHYLAXIS
Anticoagulant
- ➢ Heparin
(unfractionated)
- ➢ Low-molecular-weight
heparin (LMWHs)
- ➢ Oral anticoagulants
(OAC)
- Warfarin
- Dabigatran
- Rivaroxaban
- Apixaban
Mechanism:
- Inhibits thrombus formation and prevent extension of existing
thrombi
- No direct lytic effect on established thrombi
- Prolongs aPTT, PT and INR
Dose:
Heparin:
Typical use for IV heparin
Symptomatic AF with consideration of cardioversion or
thrombus detection on ECHO
AF with concomitant TIA or minor/small ischemic
stroke
- Initial IV bolus of ~60-80 IU/kg or 5000 IU
- Followed by an infusion of 12 IU/kg/hr; Max. 1000 IU/hr
- Adjusted to maintain an APTT to 1.5-2 times normal (usually 50
to 70 seconds)
Caveat: For patients with moderate or large
strokes, the above may be modified to a low initial exposure for
avoidance of supra-therapeutic PTT and potential risk of
bleeding:
- Initial IV bolus of ~30-40 IU/kg or 2500 IU or no bolus
- Followed by an infusion of 12 IU/kg/hr; Max. 1000 IU/hr
- Adjusted to maintain an APTT to 1.4-1.8 times normal
(suggested, but adjusted at discretion of treating physician)
Low-molecular-weight heparin (LMWH):
May sometimes be used for patients with AF/AFL
- Enoxaparin: 1 mg/kg every 12 hrs
- Dalteparin: 200 IU/kg/day SC every 12 hrs or
once daily
Warfarin:
Prevention/treatment of thrombosis/embolism
Dabigatran:
Dose (Canada labelling):
- Age <80 year: 150 mg PO BID if creatinine
clearance >30 ml/minute
- Age >80 years: 110 PO BID if creatinine
clearance >30 ml/minute
- Contraindicated in creatinine clearance <30 ml/minute
Dose (USA labelling):
- 150 mg PO BID if creatinine clearance >30ml/minute
- 75mg PO BID if creatinine clearance 15-30 ml/minute
Conversion from dabigatran to parenteral
anticoagulant
- Wait 12 hrs. after the last dose of dabigatran before switching
to a parenteral anticoagulan
Conversion from vitamin K antagonists (e.g. warfarin) to
dabigatran
- Dabigatran should only be started after vitamin K antagonists
have been discontinued, and the patient's INR <2.0
Conversion from dabigatran to vitamin K antagonists (e.g.
warfarin)
- Stop dabigatran for 12 hrs then begin warfarin
protocol/nomogram (see above)
Rivaroxaban:
- GFR ≥50 ml/minute: 20 mg PO daily
- GFR 30-49 ml/minute: 15 mg PO daily
Apixaban:
- GFR >25 ml/minute: 5 mg PO BID;
alternatively 2.5 mg BID may considered in patients with at least 2
of the following features: Age ≥80 years, body weight ≤60 kg, or
serum creatinine ≥133 micromole/L (1.5 mg/dL)
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