I can't say exactly with certainty what this means without more information, but it sounds to me like your father most likely had either an electrocardiogram (electrical tracing of the heart) or echocardiogram (ultrasound of the heart) which showed left ventricular hypertrophy.
Left ventricular hypertrophy is a common condition in which the muscle that forms the wall of the left ventricle (the biggest chamber in the heart) becomes thickened. This is usually due to chronic high blood pressure. Just like any other muscle, when made to work hard, the heart will get bigger, and having blood pressure elevated over the years will lead to a larger heart muscle than if the blood pressure was not elevated.
Your father will have to work with either his doctors
">primary care doctor or his cardiologist
to help figure out what additional treatments or workup are needed at this point. In the setting of chest pains, for example, it is pretty common to get a stress test to rule out more serious heart disease, and his doctors may want to do this if they have not done so already. Similarly, they will definitely want to work on controlling his blood pressure if that is an unresolved issue. Good luck.