Atrial Fibrillation

Definition Cardiac output can drop by 10-20% Chaotic, irregular atrial rhythm at 300-600 bpm Maintained by continuous, rapid activation of the atria by multiple meandering re-entry wavelets Atria respond electrically, but there is no coordinated mechanical action and only a proportion of the impulses are conducted to the ventricles. AV node responds intermittently, hence irregular ventricular rate Cardiac output can drop by 10-20%

Common in elderly (<9%) Main risk is embolic stroke Warfarin reduces this to 1%/yr

Causes Heart failure/ischaemia; HT; MI (22%); mitral valve disease; coronary artery disease PE; Pneumonia; Hyperthyroidism; post-op hypokalaemia; Mg2+ decrease; Phaeochromocytoma Caffeine; alcohol

Symptoms May be asymptomatic or cause- Chest pain Palpitation Dyspnoea Faintness

Signs Irregularly irregular pulse Apical pulse rate greater than the radial rate 1st heart sound of variable intensity Should examine whole pt as AF often assoc with non-cardiac disease

Investigations ECG: Blood tests: U & E, cardiac enzymes, TFTs (Echo) Shows fine oscillations of the baseline (fibrillation/f-waves) and absent P waves QRS rhythm is rapid & irregular ‘Irregularly irregular’ DO an ECG on anyone with irregular pulse (+ 24 hr ECG if dizzy, faints, palpitations etc) Blood tests: U & E, cardiac enzymes, TFTs (Echo) Look for left atrial enlargement, mitral valve disease, poor LV function & other abnormalities

Management Acute: Treat assoc illness, control ventricular rate 1st choice: diltiazem or verapamil or metoprolol 2nd rate: digoxin, amiodarone Start full coag with LMWH 2nd choice: rate control & anticoagulation Beta-blocker or rate-limiting Ca-blocker If fails, consider digoxin (as monotherapy) or amiodarone