tailieunhanh - ABC OF RESUSCITATION - PART 4

Trong rung nhĩ, tất cả phối hợp của tâm thu tâm nhĩ là bị mất và làm đầy tâm thất trong thời gian tâm trương trở thành một quá trình thụ động. Việc kiểm soát trật tự của tỷ lệ thất và nhịp điệu tồn tại trong nhịp xoang bình thường là bị mất và tỷ lệ thất được xác định bởi thời gian chịu lửa của nút AV | ABC of Resuscitation Atrial fibrillation In atrial fibrillation all coordination of atrial systole is lost and ventricular filling during diastole becomes a passive process. The orderly control of ventricular rate and rhythm that exists during normal sinus rhythm is lost and the ventricular rate is determined by the refractor y period of the AV node. When this is short a rapid ventricular rate may result which further reduces cardiac output. The treatment of atrial fibrillation centres on three key objectives to control ventricular rate to restore sinus rhythm and to prevent systemic embolism. Thrombus forms in the left atrium particularly in the atrial appendage as a result of the disturbed blood flow. Such thrombus may form within hours of the onset of atrial fibrillation and the risk of embolisation is particularly great at the point that sinus rhythm is restored. The need for anticoagulation to reduce this risk fundamentally influences the approach to treatment of this arrhythmia. Patients may be placed into one of three risk groups depending on the ventricular rate and the presence of clinical symptoms and signs. The treatment of each is summarised in the algorithm. Patients with a ventricular rate greater than 150 beats min those with ongoing ischaemic cardiac pain and those who have critically reduced peripheral perfusion are considered at particularly high risk. Immediate anticoagulation with heparin and an attempt at cardioversion is recommended. This should be followed by an infusion of amiodarone to maintain sinus rhythm if it has been restored or control ventricular rate in situations in which atrial fibrillation persists or recurs. Patients with a ventricular rate of less than 100 beats min with no symptoms and good peripheral perfusion constitute a low risk group. When the onset of atrial fibrillation is known to have been within the previous 24 hours anticoagulation with heparin should be undertaken before an attempt is made to restore sinus rhythm .