Patients with diastolic heart failure often complain of breathlessness on exertion which relates to the stiffness or lack of compliance of their heart i.e. the heart fails to relax rapidly enough to allow it to fill with blood between each heart beat. This may result in high pressure in the heart chamber which backs up in to the lungs and may be experienced as breathlessness. There is little evidence that any specific therapy benefits patients with this type of heart failure besides treating coexisting problems such as high blood pressure or angina. By slowing the heart rate down with ivabradine, the heart would have a longer time to fill during exercise which would make it more effective. This slowing of the heart rate may therefore relieve the breathlessness experienced on activity such as walking to the shops or up a flight of stairs etc.