An atrial septal defect of 4.5 mm in the heart is not a serious condition and is classified as a microscopic defect in the atrial septal defect, which is a defect in the heart of 5 mm or less. There are minimally invasive interventional procedures and open-chest direct visualization repair for the treatment of microscopic defects, regardless of which procedure is used to achieve a radical cure. Therefore, once an atrial septal defect is present, the first step is to go to the hospital to get an ultrasound of the heart to see the location and type of defect before choosing the type of surgery. After the surgery, you also need to take long-term cardiotonic and diuretic medication, which is the only way to maximize the protection of the heart and achieve the fastest recovery.