Sinus venosus defect

• AII the features are same as ostium secundum except that P waves are inverted in inferior leads, and right hilum in chest X-ray shows dilatation of lower portion of superior vena cava where it joins the right atrium.
• In the adult, it is incorporated into the wall of the right atrium to form a smooth part called the sinus venarum, also known as the venarum sinus,
• The sinus venosus also forms the SA node and the coronary sinus.
• 2D echo with colour flow and spectral Doppler local­izes the ASD.
• In humans, it exists distinctly only in the embryonic heart, where it is found between the two venae cavae.

Sinus venosus defect or sinus venarum

SD with reversal of shunt (Eisenmengern)

• Occurs in < 10% of cases
• Cyanosis develops after 3rd decade only Dyspnoea and fatigue occur
• There may be syncope
• JVP shows big ‘a’ waves
• There is parasternal heave and P2 is loud and pal­pable.
• There are signs of pulmonary hypertension, fourth
• heart sound, pulmonary ejection sound, soft short pulmonary ejection systolic murmur narrow split of or single second heart sound with loud P2 and Gra­ham steell murmur (early diastolic murmur in left parasternal area of pulmonary regurgitation due to pulmonary hypertension).

ECG:

• shows RSR pattern in V1 or rR pattern or domi­nant R wave with deeply inverted T waves.

X-ray:

• shows clear peripheral lung fields, large pul­monary trunk and its branches and small aorta.