A 21-year old male patient with history of recreational nitrous oxide abuse presented in the emergency department due to gait disorder in the past 6 months and additional shortness of breath in the last 3 days. The patient reported daily nitrous oxide consumption for more than a year. Walking distance comprised 20 meters due to dyspnea with gait instability as a results of proprioceptive ataxia, feet flexor weakness, and limb paresthesia. Laboratory measurements revealed markedly elevated levels of D-dimers (18,59 mg/l) and NT-proBNP (3,094 ng/l). Computed tomography pulmonary angiography showed acute central pulmonary embolism, with large thrombi extending in both main pulmonary arteries. The patient received unfractionated heparin and afterwards low-molecular heparin daily. Echocardiography showed signs of moderate right heart dysfunction, and the patient had no signs of cardiopulmonary instability. Thus, a conservative treatment with anticoagulation was chosen. Three days later the patient developed acute chest pain after mobilization and the electrocardiogram showed ST-elevation in leads I, aVL, V5-V6. Emergent coronary angiogram revealed proximal left anterior descending (LAD) artery occlusion with large thrombus burden. Thrombus aspiration was performed with residual thrombotic material extending to a proximal diagonal branch. Balloon dilatation was undertaken with good reflow, and stent implantation was therefore deferred. Bedside echocardiography showed apical akinesia, large multiple biventricular thrombi, and a large thrombus passing through the patent foramen ovale (PFO). Consequently, the patient underwent emergent surgical embolectomy in both main pulmonary arteries, the ascending aorta, and in all four cardiac chambers including removal of a large (20 cm) worm-like thrombus from the PFO. Finally, PFO closure was performed. Creatine kinase (CK) max was 1,029 U/l. The patient presented an uneventful course after antibiotic treatment of infarction pneumonia and was discharged thereafter. At three-month outpatient follow-up, the patient presented asymptomatic. Echocardiography revealed a modest right ventricular dilatation of 45 mm with a reduced tricuspid annular plane systolic excursion (TAPSE) (most probably after cardiac surgery) but normal fractional area change (FAC) of 41%. There was no systolic pulmonary artery pressure gradient in echocardiography. NT-proBNP levels were normal with 67 ng/l. Nitrous oxide is known to be associated with vitamin B12 deficiency which leads to polyneuropathy, funicular myelosis, and elevation of homocystein and plasma methylmalonic acid (MMA). Therefore, the patient was advised continue anticoagulation for a least six months, remain abstinent from recreational nitrous oxide abuse, and take vitamin B12 supplementation for treating funicular myelosis and polyneuropathy.
