A normal heart rate but enlarged heart may be caused by hypertensive heart disease, dilated cardiomyopathy, pulmonary hypertension and other diseases. 1. Hypertensive heart disease: it is mainly caused by the significant increase of blood pressure, which leads to the increase of the load of the heart. Failure to lower the blood pressure in time leads to the enlargement of the heart and the hypertrophy of the left ventricle. 2. Dilated cardiomyopathy: this disease is usually associated with myocarditis and cardiomyopathy, which can easily cause heart enlargement, heart failure and arrhythmia. 3. Pulmonary arterial hypertension: pulmonary arterial hypertension will lead to increased load on the right ventricle, which will easily lead to hypertrophy and enlargement of the right ventricle if not treated in time. If the heart rate is normal but the heart is enlarged, it is necessary to carry out the next step of examination, including cardiac ultrasound, electrocardiogram, etc., according to the diagnostic results and then symptomatic treatment.