Without any further information, your heart dilated to compensate to increase the cardiac output. This is normal to maintain a balance of blood flow between the left and right side of the heart's chambers and there are variations of 50 t0 70% EF and that indicates the percent of blood pumped with each heartbeat.
If the EF exceeds the normal range 50 to 70%, that may indicate the heart is overcompensating for a deficiency with other factors such as heart rate, blood pressure, blood volume, etc. When the heart overcompensates for a period of time the dilation of the left ventrical increases to a size that is pathological and the left ventricle loses its strength to pump adequately and the EF drops.
Your echo should provide the size of your left ventricle, right ventricle, atria, and if there is any hypokinesis (heart wall movement impairment).
I've provided the worst case scenario, and even if that is the underlying cause for the low EF there is effective treatment. Thanks for sharing, and if there is any other questions or comments, you are welcome to reapond. Take care,
Ken