It depends upon 1. the causes of the enlargement (cardiomegaly) e.g. Valvular disease, hypertension , cardiomyopathy etc. etc. 2.the effects. A mild cardiomegaly may not have any effect upon the circulatory system . A severe one, where the heart has lost a significant amount of healthy elasticity, heart failure may be present to an intractable stage. As you can imagine there is a wide spectrum of the consequences of heart enlargement. On one side there is the mild one with no circulatory embarassment and amenable to treatment. On the other side there is the one which is uncontrollable with treatment and eventually becomes terminal. In between these two extremes various grades of severity exist and various degree of responses to treatment occurs. Hope this answers your question.