Enlarged heart or 'cardiomegaly' is more usually associated with an enlarged or dilated left ventricle. In rare cases the right venticle can be enlarged but this is linked to lung disease.
Enlargement can be as a result of the heart putting on extra muscle to cope with an increased load or volume of blood to be pumped.This tends to suggest that one or more of heart valves is not working as it should. The other explanation can be a connecting hole between the heart chambers that allows blood to flow backwards and cause a volume overload.
Without further knowledge from your loved one, my best guess would be that he is either getting a hole patched over, or having a faulty valve repaired or replaced. Both Mitral valve malfunction and aortic stenosis can cause cardiac enlargement.
Both heart holes and dodgey valves can be heard as 'heart murmours' through a stethoscope.
My best thoughts are with you both