Introduction: Mitral stenosis represents a valvular dysfunction arising from its impossibility of opening completely which in turn creates a significant atrio-ventricular gradient in the left side of the heart. The primary cause of mitral valve stenosis is rheumatic fe-ver secondary to the pharyngo-tonsilar infection with group A beta-hemolytic streptococci, with a decrea-sing prevalence due to efficient primary and secondary prophylaxis. As the disease progresses, left atrial dilati-on appears, which can lead to embolic atrial arrhyth-mias, on top off the associated risk of atrial thrombosis associated with the presence of the mitral stenosis itself. Case review: A 32 year-old lady, non-smoker, with a low socio-economic status, 22 weeks pregnant, presents to the emergency department with rapid and irregular palpitations that started 12 hours prior and dyspnea at rest. She had similar self-limiting episodes (10 minutes at most) in the past 2 weeks. She had four pregnanci-es successfully carried to term, with no known cardio-vascular history. Physical examination: tachypnea (28 breaths per minute), BP 105/60 mmHg, PR 140 per minute, irregular, with no apparent murmurs, no signs of pulmonary congestion, and minor jugular vein dis-tention. ECG: atrial fibrillation with a ventricular rate of 150 per minute, narrow QRS complex and diffuse ST segment depression of approximately 1 mm. Biological profile: minor normochromic-normocytic anemia (Hb 10,5 g/dl), NTproBNP 600 pg/ml, negative troponin, negative D-dimers. Echocardiography: non-dilated left ventricle, with conserved LVEF and no regional wall motion abnormalities, severe mitral stenosis with a mean trans-valvular gradient of 12 mmHg and a peak value of 22mmHg, valvular area of 0,8 cm2 (measured by PHT method and confirmed by anatomic measure-ment from the parasternal short axis view), dilated LA 42 ml/m2, aortic valve with adequate opening, aortic valve flow velocity of 1 m/s, RA 45 mm, RV 42 mm, PAPs estimated at 50-55 mmHg, normal RV function, moderate tricuspid regurgitation. It is decided to con-trol the PR in the emergency room with metoprolol succinate 5 mg i.v. (3 doses administered at a 1 hour interval), with no results on the ventricular rate and a slight decrease in systolic BP to 100 mmHg. The ad-ministration of cardiac glycosides was avoided. After continuous monitoring in the emergency room, 1 hour after the last metoprolol succinate dose, the heart rate raised to 160/min, with worsening of the symptoms and a further drop in systemic BP to 80 mmHg. It is decided to admit the patient in the intensive coronary care unit and emergency electric cardioversion was in-dicated, but while awaiting analgesic medication the patient converts spontaneously to sinus rhythm, with significant alleviation of symptoms and hemodynamic stabilization. She was put on parenteral anticoagulant medication with unfractionated heparin for the dura-tion of hospitalization, which would be continued with oral anticoagulant drugs (acenocoumarol) after dis-charge with a target INR of between 2 and 3, taking into account the high risk of atrial and auricular thrombosis associated with mitral stenosis. For the prevention of reoccurrence metoprolol succinate 50 mg was chosen in a single daily dose and for decongestion furosemide 20 mg once a day was prescribed. Furthermore, for re-ducing the fetal and maternal risk in the last trimester, close hemodynamic evaluation was recommended and, in case of severe secondary pulmonary hypertension or acute pulmonary edema, emergency caesarean section with percutaneous mitral commissurotomy/surgical valve replacement would be considered. At discharge (day 3): The patient was hemodynamically stable with complete remission of symptoms.

Case specific features: the challenge in managing this complicated case is in no small part due to the limited therapeutic options for treating atrial fibrillation in a pregnant patient. Pharmacological cardioversion pre-sents itself with numerous problems in choosing the ri-ght drug taking into account that amiodarone, which is widely used for this, is contraindicated in pregnant wo-men while propafenone use is highly questionable in pregnancy and has a clear contraindication in advan-ced structural cardiac disease. Emergency electrical cardioversion becomes necessary in patients with he-modynamic instability caused by the atrial fibrillation. Another remarkable characteristic is that the patient was completely asymptomatic over the last 4 pregnan-cies, considering the presence of severe mitral stenosis. Conclusions: Pregnancy in a patient with severe struc-tural cardiac disease represents a challenge considering the limited therapeutic options and the vital risks for both the fetal and the maternal sides. Evaluation of the risk/benefit ratio of every medical decision is cruci-al. Multidisciplinary approach is mandatory in such a case.