EL ESTADO DE NECESIDAD

1. Common - Ischaemic heart disease, mitral valve disease (commoner in stenosis), thyrotoxicosis, hypertension.

2. Less common - cardiomyopathy, pericarditis, sick sinus syndrome, atrial myxoma, endocarditis, chronic lung disease, atrial septal defect, acute alcohol intoxication, WPW syndrome, digoxin toxicity and lone AF.

B. Clinical Features

• May be either chronic or paroxysmal.

• Irregularly irregular pulse, S1 of variable intensity, pulse deficit (rate at apex is greater than at radial artery).

• ECG: chaotic baseline with no P waves, irregularly irregular but normally shaped QRS complex (unless concomitant BBB or preexcitation syndrome) at a rate of 160-200/min. AF with regular ventricular response may suggest digoxin toxicity.

• Complications of atrial fibrillation are hypotension, cardiac failure, systemic embolism and troublesome palpitations.

C. Investigations

• BUSE, ECG, CXR, cardiac enzymes, thyroid function, calcium and Echo.

D. Treatment _ Aims of therapy:

• Control of the ventricular rate using AV node blocking drugs (digitalis, beta blockers, calcium channel blockers and occasionally amiodarone).

• Reversion to sinus rhythm using membrance stabilizing agents [(class 1a -quinidine, procainamide, disopyramide), class 1c (propafenone, flecanide) and class III (sotalol, amiodarone)] or cardioversion.

• Prophylatic therapy to prevent recurrence.

• Anticoagulation to prevent embolization.

1. Emergency synchronised cardioversion is required in patients with rapid ventricular response (VR >200/min) and acute haemodynamic

deterioration (eg. patients with angina, hypotension, dyspnoea, or heart failure).

• If initial cardioversion is unsuccessful, procainamide or amiodarone can be given to facilitate further cardioversion attempts.

• Do not attempt to cardiovert patients with known chronic AF & a known progressive cause (eg. MS), in which case, rapid rate control with drugs should be achieved.

• Patients undergoing emergency cardioversion should receive anticoagulant therapy for 2-3 weeks after conversion unless there is a contraindication (anticoagulation may not be necessary if AF is <24-48 hr duration).

2. Haemodynamically stable acute AF and Chronic AF:

• The aim is to control ventricular rate using AV node blocking agents such as digitalis, beta blockers, calcium antagonists or amiodarone.

• In patients with normal heart clinically and on echocardiography, either digoxin, beta-blockers, verapamil /diltiazem or amiodarone can be used. If sick sinus syndrome is suspected as a cause, digoxin and drugs which exaggerate AV conduction delay should be avoided.

• In patients with LV dysfunction, if

a. EF <40%, digoxin or amiodarone are the drugs of choice.

b. EF >40%, digoxin +/- beta blockers or amiodarone can be used.

a. Digoxin:

• Loading dose: Either IV 0.25-1.5mg over 24 hour (0.5mg in 50ml of NS or D5% over 1-2hrs followed by 0.25mg iv every 2-4 hours until adequate response occurs or total dose of 0.02mg/kg or 1.5mg )

or

orally, 0.75-1.5mg over 24 hr (eg. 0.25-0.5mg tds for 1 day, bd for 1 day) if patient has not taken digoxin for the past 1-2 weeks.

• For patients who have been taking digoxin within 1 week, a dose of 0.125mg IV or oral can be given followed by 0.125mg, if needed, after 2 hrs followed by maintenance.

• Maintainance dose is 0.0625-0.5 daily, usually 0.25mg daily (Lower doses eg. 0.0625mg should be used in elderly and in patients with renal impairment).

• In some patients, digoxin fails to prevent acitivity induced tachycardia, then a small dose of beta-blockers may be needed.

b. Propanolol:

• Propanolol is useful in AF not responding to digoxin and it has a synergistic action with digoxin.

• IV 0.5-1mg/min, repeat every 2min up to total dose of 0.15 mg/kg or 10mg.

or

Oral propanolol 120-240mg daily in 3 divided doses.

c. Verapamil:

• Can be used as alternative or in addition to digoxin.

• IV 5-10mg over 1-2 min followed by oral dose 40-120mg tds.

d. Diltiazem:

• Useful alternative to verapamil as verapamil has high incidence of heart failure.

• 20mg or 0.25mg/kg IV over 2 min followed, if necessary, by 25mg or 0.35mg/kg IV 15 min later. Maintenance infusion of 5-15mg/h thereafter.

• Oral maintenance of 60-120mg 3 times daily should then be given.

e. Amiodarone:

• Amiodarone is also used in the treatment of atrial fibrillation with rapid conduction that causes haemodynamic embarrassment to convert AF to sinus rhythm because of its safety in patients with poor left ventricular function and the relatively low incidence of ventricular arrhythmias. Even in those patients who did not convert to sinus rhythm, a slower heart response can be achieved compared to digoxin.

• IV: Loading dose of 300-600mg (5-10mg/kg) in 250ml of D5% over 2 hrs (may be given in 100 ml if fluid restriction) and it may need to be followed by 300-600mg in 250ml D5% over 24 hrs (ie. 5-10mg/kg /day to a daily maximim dose of 1.2g). The infusion can be continued for several days (max 2-3 weeks) before changing to oral amiodarone.

• In emergency, the loading dose can be put in 100ml and run over 10 mins.

• Transition to oral therapy: 200mg 3 times daily for 1 week reduced to 200mg twice daily for a further week then maintenance dose.

• Maintenance: Usually 200-300mg daily.

# Digoxin and verapamil are strictly contraindicated with WPW in atrial fibrillation.

3. Elective conversion to sinus rhythm:

• An attempt should be made to convert all patients with AF present for < 6-12 months, and when the left atrium is not enlarged (<45mm).

Cardioversion is less likely to be successful if AF has been present for over a year, left atrial size is >45 mm, and untreated conditions are present (eg.

thyrotoxocosis, valvular heart disease and heart failure).

• Pharmacological conversion should be attempted first.

• Class 1a - (quinidine, procainamide, disopyramide), Class 1c (propafenone, flecanide) and Class III (sotalol, amiodarone) drugs can be used to restore sinus rhythm but ventricular response should be controlled first. Class IA and IC drugs should be avoided in patients with left ventricular

hypertrphy, with coronary artery disease and with a previous infarct.

• If atrial fibrillation persists, digitalis should be withheld for 24h, and then DC cardioversion (start with 100J) should be attempted (refer to section on cardioversion).

• In elective cardioversion (electrical or pharmacological), ideally, the patient should receive a 4 week course of oral anticoagulation before conversion and for 4 weeks after conversion. Cardioversion can also be attempted early if transesophageal echocardiography does not show evidence of left atrial thrombi.

4. Prophylatic therapy to prevent recurrece of AF:

• If sinus rhythm is restored, dual therapy with both an AV node blocking drug and a membrance stabilizing agent (Class IA, IC or III) is

recommended to prevent recurrence (except for sotalol and amiodarone, which have both properties when monotherapy is adequate).

• If recurrences cannot be prevented, therapy is directed toward controlling the ventricular rate.

• Sotalol and amiodarone may be preferred in paroxysmal AF.

• Permanent pacemaker: High rate atrial pacing may inhibit AF.

• Radiofrequency catheter ablation may offer cure for selected cases.

5. Prophylaxis for embolic phenomenon:

a. Acute AF:

• IV heparin should be given to all patients except those with AF of <24-48hrs.

b. Chronic AF:

• Guidelines are summarized as below:

Age Risk Factors* Recommendations

< 60 Present

Absent Warfarin with INR 2-3

Aspirin or nothing

60-75 Present

Absent Warfarin with INR 2-3

Warfarin or Aspirin

> 75# Warfarin with INR 2-3

or Aspirin

* Risk factors: Previous TIA or stroke, hypertension, DM, coronary artery disease, mitral valve disease, prosthetic heart valves and thyrotoxicosis

# Age >75, little data available, has increased risk of major haemorrhage from warfarin, continue if already on & tolerating. Otherwise, consider patient's long-term outlook, concomitant medical problem and etc.

6. Footnotes:

_ Vaughan Williams' Classification of antiarrhythmic drugs.

Class Mechanism of Action Drugs

I Membrane-depressant drugs that reduce the rate of entry of sodium into the cell.

Ia Lengthen the action potential Quinidine

Procainamide Disopyramide

Ib Shorten the action potential Lignocaine

Mexiletine Tocainide Phenytoin Ic Do not affect the duration of action potential Flecainide Propafenone

II Beta-adrenergic blocking drugs which prevent the

effects of catecholamines on the action potential Propanolol Metoprolol

III Prolong the action potential and do not affect

sodium transport through the membrane Amiodarone Sotalol Bretylium IV Non-dihydropyridine calcium antagonist that

reduce the plateau phase of the action potential Verapamil Diltiazem

Others Adenosine

Digoxin

_ ATRIAL FLUTTER