IV Septal Thickness 0.7-1.2 cm.
LV Posterior Wall Thickness 0.7-1.1 cm.
LV Internal Diameter, systole 2.5-4.0 cm.
LV Internal Diameter, diastole 3.5-5.5 cm.
LVEF 55-75
Does you echo report provide wall thickness? Based on the parameters you have provided, it appears you left ventricle is dilated. And your heart is only pumping about 20 to 22% of the blood received from the heart...normal is 50 to 70% and is referred to as ejection fraction (EF).
When the left ventricle is dilated that will reduce the ejection fraction so the focus of your treatment should be to reduced heart size to normal if possible. I had the same medical circumstances 7 years ago, and today my heart is normal size and functioning normally with EF of 59%.
The underlying cause for your present heart condition should be treated. Almost always the heart enlarges due to a heavy burden the heart pumps agains. If the burden can be reduced the heart can return to normal. Vessel resistance with narrow and/or occluded vessels if properly treated can be effective. A had a stent implant and medication that improved blood flow to areas deficit of good blood flow.
There can be other causes for an enlarged heart and that good be any abnorality that reduces the cardiac output. That could be due to valve insufficiency or other anamolies of heart structure.
What you can do is follow your doctor's advice and take any necessary medication and see if there is any improvement over a period of time. It is difficult provide further information within some knowledge of your health history, other tests, more complete echo report, etc. I hope I have given a perspective, and given you a basis for further consulation with your doctor as (s)he would have more information and a better source. However, if you have any further information you are welcome or comments you are welcome to respond.
Thanks for sharing, take care.