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Background: Tight mitral stenosis is a valvular pathology frequently associated with thrombus formation in the left atrium due to blood stasis. When a patent foramen ovale (PFO) is also present, this can allow thrombus to pass from the venous circulation into the systemic circulation, leading to paradoxical embolism. Although rare, this association carries a high risk of serious complications. We report here a case of paradoxical embolism in a patient with a giant thrombus in the left atrium and a PFO, on a background of tight mitral stenosis.

Case Summary: A 62-year-old male patient, with no cardiovascular risk factors besides age and sex, was admitted for worsening chronic dyspnea (NYHA class IV) and lower limb edema. Examination revealed signs of right and left heart failure. Echocardiography showed severe rheumatic valve disease, multiple thrombi in the left atrium, and a patent foramen ovale with thrombi. Chest CT revealed a pulmonary embolism in the right lower lobe. Urgent surgery including mitral valve replacement, tricuspid plasty, PFO closure, thrombectomy and embolectomy was indicated. Unfortunately, preoperative obstructive shock due to thrombus migration to the mitral valve led to the patient's immediate death.

Discussion: This case illustrates the complexity of managing patients with mitral stenosis associated with PFO. The increased risk of thrombus formation in the left atrium and the possibility of systemic migration via the PFO underscore the need for careful ultrasound screening in these patients. Optimal treatment includes anticoagulation, PFO closure and mitral valve repair to prevent thromboembolic recurrence and improve long-term prognosis.

Keywords: Mitral stenosis; Patent foramen ovale; Paradoxical embolism; Giant thrombus; Obstructive shock