Back Heart Defects Causing Too Little Blood Flow Through the Lungs Heart defects that cause too little blood flow through the lungs require clinical care by a physician or other healthcare professional. Listed in the directory below are some of these defects, for which we have provided a brief overview. Tricuspid Atresia (TA) Pulmonary Atresia (PA) Transposition of the Great Arteries (TGA) Tetralogy of Fallot