Heart failure occurs when the heart is unable to pump sufficiently to maintain blood flow due to conditions that damage or overload the heart muscle such as myocardial infarction, hypertension, amyloidosis, and cardiomyopathy. It can be caused by systolic dysfunction where the heart has a reduced force of contraction or diastolic dysfunction where the heart has difficulty filling. Symptoms range from no limitation of activity to being unable to carry out any physical activity without discomfort.