During percutaneous interventional procedures such as mitral valvuloplasty (a surgical process done to repair a mitral valve), 11-12% of individuals will develop ASD allowing blood to flow from the left atrium to the right. Mitral Valve Stenosis
The second cause of Lutembachers syndrome is mitral stenosis (MS). MS can be caused by birth defects, rheumatic fever, or just stress to the heart due to ASD; because MS can be caused by several things, there is no exact mechanism but many mechanisms or causes. If mitral valve stenosis is a result of birth defects during development stemming from rheumatic fever, several things may occur in the heart. Rheumatic fever causes the immune system to attack its own protein tissues leading to lesions forming on the mitral valve flaps. As the flaps heals over time, the flaps lose their filmy and floppiness resulting in solid, stiff flaps. The loss of proper flappy mitral valves makes it harder for the valves to open and allow blood to flow through. As a result of blood flow being stopped or slowed by the faulty valve, pressure begins to build in the heart. It was once thought an ASD is not already present, could form because of MS, but it is now thought the ASD is either a birth defect or acquired from surgical procedures.Overall, Lutembachers syndrome has no certain mechanism but a combination as the result of ASD and MS.
Treatment
If suspected antenatally, a consultation with a paediatric surgeon/ paediatric urologist maybe indicated to evaluate the risk and consider treatment options.Treatment is by endoscopic valve ablation. Fetal surgery is a high risk procedure reserved for cases with severe oligohydramnios, to try to limit the associated lung underdevelopment, or pulmonary hypoplasia, that is seen at birth in these patients. The risks of fetal surgery are significant and include limb entrapment, abdominal injury, and fetal or maternal death. Specific procedures for in utero intervention include infusions of amniotic fluid, serial bladder aspiration, and creating a connection between the amniotic sac and the fetal bladder, or vesicoamniotic shunt.There are three specific endoscopic treatments of posterior urethral valves:
Vesicostomy followed by valve ablation - a stoma, or hole, is made in the urinary bladder, also known as low diversion, after which the valve is ablated and the stoma is closed. Pyelostomy followed by valve ablation -  stoma is made in the pelvis of the kidney as a slightly high diversion, after which the valve is ablated and the stoma is closed
Primary (transurethral) valve ablation - the valve is removed through the urethra without creation of a stomaThe standard treatment is primary (transurethral) ablation of the valves. Urinary diversion is used in selected cases, and its benefit is disputed.Following surgery, the follow-up in patients with posterior urethral valve syndrome is long term, and often requires a multidisciplinary effort between paediatric surgeons/ paediatric urologists, paediatric nephrologists, pulmonologists, neonatologists, radiologists and the family of the patient.