atrial tachyarrhythmia on the effectiveness of landiolol was uncertain. In addition, the majority of those patients treated with landiolol were admitted to the intensive care unit or cardiac care unit, where continuous invasive arterial blood pressure monitoring and mechanical ventilation were available. The purpose of the present study was to evaluate the efficacy and safety of landiolol treatment for tachycardiac AF and tachycardiac AFl/AT patients with LV dysfunction in a general cardiovascular ward. Methods Subjects Seventy-seven consecutive patients with acute decompensated HF (ADHF) who were treated with landiolol for atrial tachyarrhythmia on the general ward of the Department of Cardiology at Nippon Medical School Hospital were retrospectively analyzed between November 2013 and March 2016. In this study, the patients were divided into 2 groups according to the mechanisms of the atrial tachyarrhythmia at the time of admission (Figure 1). The main inclusion criteria were ADHF (New York