The present invention relates to an If blocker or a pharmaceutically acceptable salt thereof for the treatment and/or prevention of a canine patient suffering from heart diseases, preferably heart diseases such as dilated cardiomyopathy (DCM), mitral valve insufficiency (MI), arrthymias, preferably tachyarrthymias, preferably artrial arrythmias, atrioventricular nodal arrythmias and/or tachycardia. Each of these diseases may or may not result in heart failure (HF) in canine patients. The invention also relates to improving the quality of life, improving the general health condition as well as a prolonging the life expectancy in canine patients suffering from heart diseases and/or heart failure due to one or more of the following aetiologies dilated cardiomyopathy (DCM), mitral valve insufficiency (MI), arrthymias, preferably tachyarrthymias, preferably artrial arrythmias, atrioventricular nodal arrythmias and/or tachycardia.本發明係關於用於治療患有心臟疾病之犬科動物患者及/或預防其患心臟疾病之If阻斷劑或其醫藥上可接受之鹽,較佳地諸如以下心臟疾病:擴張型心肌病(dilated cardiomyopathy;DCM)、二尖瓣閉鎖不全(mitral valve insufficiency;MI)、心律不整,較佳地快速性心律不整,較佳地心房性心律不整、房室性結性心律不整及/或心博過速。該等疾病中之每一者會或不會導致犬科動物患者心臟衰竭(heart failure;HF)。本發明亦係關於改善患有心臟疾病及/或心臟衰竭之犬科動物患者之生活品質、改善其一般健康狀況以及延長其預期壽命,該心臟衰竭因以下病因中之一或多者導致:擴張型心肌病(DCM)、二尖瓣閉鎖不全(MI)、心律不整,較佳地快速性心律不整,較佳地心房性心律不整、房室性結性心律不整及/或心博過速。
