The heart functions as a pump, circulating oxygenated blood to the body and returning oxygen-poor blood to the lungs. Efficient circulation relies on adequate valve function managed by the heart’s electrical and mechanical systems. The strength of the heart is assessed by the amount of blood pumped out of the heart each minute (cardiac output) and the percentage of blood ejected with each heartbeat (ejection fraction (EF)). A normal EF ranges between 50% and 70% and can be measured by various modalities like echocardiography. An EF below 50% or above 70% can indicate impaired heart function and is a risk factor for developing heart failure and dangerous arrhythmias. Knowing your numbers, like EF, is important in guiding treatment options and patient management.