Mobile right heart thrombus as a manifestation of homozygous mutation of MTHFR 1298 A C

Objective: Mobile right heart thrombi (MRHT) are uncommon but the true prevalence is still unknown. Previous studies reported thay MRHT occur in 7% to 18% of patients with pulmonary embolism. Chartier et al. have reported in-hospital mortality of MRHT as 44.7%. The main manifestations of venous thromboembolism (VTE) are deep venous thrombosis (DVT) and pulmonary embolism (PE). In addition, genetic factors play an important role in pathogenesis of VTE. The relationship between common genetic mutations such as factor V Leiden, prothrombin factor II G 20210A, methylenetetrahydrofolate reductase (MTHFR), deficiencies of protein C, protein S, and antithrombin III, and VTE have been reported. Nevertheless, hyperhomocysteinemia was documented in the pathogenesis of VTE. Methods: A 34-year-old man was presented to the emergency department because of sudden onset of dyspnea. He describes loss of consciousness occurred two days before. He had no previous history of both venous thromboembolism and acute coronary syndrome. He denied any trauma, history of malignancy, recent surgery, and any drug usage. Admission physical examination was unremarkable. Examination of lower extremities was also normal. Baseline 12-lead electrocardiogram (ECG) revealed sinus rhythm and S1Q3T3 sign. Because of suspicion of PE, bedside transthoracic echocardioghraphy (TTE) was performed and revealed mobile right atrial mass. Left ventricular systolic functions were normal. Right ventricle was not enlarged and estimated systolic pulmonary arterial pressure was 28mmHg. Because of poor imaging quality with TTE, transesophageal echocardiography (TEE) was performed and two hypermobile and snake-like thrombi in the right atrium were demonstrated (Figure 1A). Duplex scan of the lower extremities was normal. Laboratory parameters were within normal limits. Homocysteine was slightly elevated: 19.6mmol/L (5.5–14mmol/L). Upon genetic testing, there were no mutations in the factor V Leiden (G1691A), factor II (G20210A), and MHFR (C677T). Only homozygous mutation of MTHFR (A1298C) was detected. Pulmonary computed tomography revealed bilateral lower lobe PE. Because of hemodynamic stability and no evidence of RV strain, anticoagulation with heparin was administered. After 10 days of hospitalization, control TEE was performed and right atrial thrombi were markedly decreased (Figure 1B). The patient was discharged with warfarin treatment for indefinite time. Results: In the present case, we postulated that the possible cause of right atrial thrombi is MTHFR A1298C homozygous mutation because no other predisposing factors were present in our patient. For the best of our knowledge, right heart thrombus as a manifestation of homozygous MTHFR mutation have not been reported previously. Figure 1. (A) Pretreatment transesophageal echocardiography showing two mobile thrombi in the right atrium. (B) Aftertreatment transesophageal echocardiography showing markedly reduced thrombi in the right atrium. RA, right atrium; RV, right ventricle; PA; pulmonary artery; Th; thrombus.