Methods
A retrospective analysis was performed in consecutive patients treated at our institution with an LVEF ≤ 50 % presenting with new-onset non-ischemic HF. The definition of TCM included: 1) heart rate on admission > 100 beats/min and evidence of prolonged elevated heart rate; 2) recovery of LVEF after the restoration of sinus rhythm or rate control (> 5 % absolute increase in LVEF [9]); and 3) exclusion of other causes of HF. The decision to perform EMB was based on clinical criteria and indications, as described previously [10,11,12,13]. Cardiomyopathies were defined according to classification criteria from the American Heart Association and the European Society of Cardiology [12,13,14]. Coronary artery disease as the cause of the reduced LVEF had to be excluded using coronary angiography before a patient was eligible for inclusion in the study. All patients were medically treated according to current guidelines, depending on the degree of HF symptoms and LVEF development [15].
LVEF was estimated by echocardiography using the modified Simpson’s rule with images obtained from apical 4- and 2-chamber views. The study conformed to the principles outlined in the Declaration of Helsinki, and the local ethics committee approved the research protocol.