Previously thought as exclusively due to digitalis toxicity, it may actually occur even in patients with diseased hearts. The P waves, although usually positive in the inferior leads, have a morphology different from sinus rhythm. The atrial rate is inferior to 250 bpm. Second degree AV block or advanced block is usually present. Prognosis is mainly bound to the underlying cardiopathy.
Atrial fibrillation is the most frequent supraventricular arrhythmia.
Since this risk is particularly high following sinusalization, when atrial mechanical function resumes, chemical or electrical cardioversion can be attempted only if the arrhythmia has been lasting no more than 48 hours. Nevertheless, if a transoesophageal echocardiogram rules out the presence of atrial thrombi, it will be possible to cardiovert the patient under heparin administration, to be started immediately and maintained until oral anticoagulants do not provide full protection. Anticoagulant therapy should be continued for at least one month after cardioversion. In recent onset atrial fibrillation, the treatment depends on the clinical setting. If the arrhythmia cause low cardiac output or cardiac failure, DC cardioversion will be mandatory.