The heart will enlarge over time if it has to pump against high resistance due to constricted vessels (high syustole measurement) and resistance due to occluded or partially occluded vessesls. When necessary it takes medication to dilate vessels and cholesterol management, however a proper diet, regular exercise and healthy lifestyle can help prevent or prevent.
An enloarged heart can be due to a virus, heredity (congenital) or ideopathic (cause unknown). Prevention may not be an option , but requires medical intervention.