Background: Loop diuretics are commonly used in heart failure (HF) patients, but they are sometimes associated
with insufficient response as well as adverse events. In such diuretics-resistant cases, tolvaptan, a vasopressin type
2 receptor antagonist, shows the improvement of volume overload without electrolyte imbalance. Tolvaptan was
launched in Japan in 2010, and a post-marketing surveillance has been performed to evaluate the safety and efficacy
of tolvaptan in real-world clinical settings