Interatrial septal defect (ASD) diagnosed.  Patient presents with [Symptom 1, e.g., shortness of breath] and [Symptom 2, e.g., fatigue]  consistent with atrial septal defect symptoms.  Physical examination reveals [Physical Exam Finding 1, e.g., fixed split S2 heart sound] and [Physical Exam Finding 2, e.g., systolic murmur].  Echocardiogram confirms the presence of an interatrial communication consistent with an ASD, measuring [Size] [Units] with [Shunt direction, e.g., left-to-right shunt].  Severity assessed as [Mild, Moderate, or Severe] based on echocardiographic findings and clinical presentation.  Differential diagnosis included patent foramen ovale (PFO), ventricular septal defect (VSD), and pulmonary hypertension, ruled out based on echocardiographic findings.  Diagnosis codes considered include I21.1 (Atrial septal defect),  and additional codes may be added based on specific defect type (e.g., ostium secundum, ostium primum, sinus venosus) and associated complications.  Treatment plan includes [Medication if any, e.g., diuretics for symptom management] and [Intervention if any, e.g., surgical or percutaneous closure] depending on defect size, symptoms, and patient factors.  Patient education provided regarding ASD, potential complications (e.g., arrhythmias, heart failure, paradoxical embolism), and follow-up care including regular cardiology appointments and echocardiographic monitoring. Prognosis discussed with the patient, with emphasis on potential for full recovery following successful closure.  Referral to pediatric cardiology (if applicable) or adult congenital heart disease specialist made for further management and treatment considerations.