1 = Upper sinus venosus defect 2 = Lower sinus venosus defect 3 = Ostium secundum atrial septal defect 4 = Coronary sinus atrial septal defect 5 = Ostium Primum atrial septal defect The murmur ...

When an ostium primum atrial defect is present, the ECG reveals left axis deviation. When an ostium secundum atrial septal defect is present, the ECG reveals right axis deviation.