Perioperative management of atrial fibrillation R 1 Anaesthesia

Perioperative management of atrial fibrillation R 1 劉志中 Anaesthesia , 1998, 53, pages 665 -676

Prevalence n n 0. 4% in adult less than 60 years old 12% in those over 75 years

Classification of AF Drugs 2003; 63(14)1489 -1509

etiology

Volatile anesthetic agent n n n Sensitizing the myocardium to catecholamine Have an apparent antifibrillary effect in the ventricle following periods of ischemia and reperfusion similar to CCB like verapamil. Depression of sinus node automaticity, increased supraventricular refractoriness and depressed AV nodal conduction

Clinical consequence n n Loss of “atrial kick” Excessively rapid and irregular ventricular rate Systemic thrombo-embolism and a significant risk of stroke Patient discomfort due to palpitation

Loss of “atrial kick” n n Absent (atrial fibrillation) , ineffective (atrial flutter) , or altered timing of atrial contraction (low atrial or junctional rhythm) can reduce ventricular filling by 20 -30% LV dysfunction more depend on atrial kick

Excessively rapid and irregular ventricular rate n Ventricular filling progressively becomes impaired at high heart rate (>120 beats/min in adult ).

Tachycardiomyopathy n n Tachycardia-induced LV dysfunction due to high ventricular rate (>120 bpm) which is reversible with rate or rhythm control LV dysfunction secondary to chronic tachycardia

Tachycardiomyopathy

What is the Optimal Ventricular Rate during Atrial Fibrillation?

Current recommandation for the targets of rate control n n ≦ 80 -90 bpm at rests ≦ 110 -115 bpm during moderate exercise

Management strategies n n Management of acute-onset AF Maitenance of sinus rhythm Control of ventricular rate Prevention of thromboembolism

Management of acute-onset AF ~ cardiversion ~ n DC cardioversion: 1. Indication : AF associated with hypotension, CHF, active ischemia or acute infarction. Patients with severe AS, MS, and hypertrophic cardiomyopathy 2. contraindication: digoxin toxicity, a history of bradycardia or sick sinus syndrome, and inadequated correct precipitating factors.

Duration of AF>48 hrs without >3 weeks anticoagulation or exclude the atrial thrombus by TEE Do Not DC cardioversion!!!

Management of acute-onset AF ~ cardiversion ~ n Pharmacological cardioversion:

Maintenance of sinus rhythm

Rate control vs. Rhythm control

Treatment option for rate control

Further investigation of AF n n n Full history and examination 12 lead ECG (including and ECG during periods of sinus rhythm if AF is paroxysmal in order to detect intra-atrial conduction defect) Echocardiography(Dx of impaired LV function) Serum chemistry screen including thyroid function test Exercise ECG if arrythmia is exercise-induced. Electrophysiological studies in p’t who are young or refractory to treatment.