A 63-year-old man with a history of systemic hypertension presented to the emergency department for evaluation of acute chest pain and shortness of breath that occurred while he was shoveling heavy snow. His heart rate was 114 bpm and blood pressure was 142/78 mm Hg. Peripheral oxyhemoglobin saturation was 91%, and his respiratory rate was 20 breaths per minute. During the physical examination, he developed severe left arm pain associated with complete loss of the left radial and brachial pulses. Urgent upper-extremity angiography demonstrated acute thromboembolism of the proximal left axillary artery (Figure 1A). Percutaneous transluminal embolectomy, followed by catheter-directed thrombolysis, was performed to successfully treat the arterial thrombus. However, thoracic computed tomographic (CT) angiography identified bilateral pulmonary emboli (Figure 1B). Coincidental venous and arterial thromboemboli raised suspicion for a paradoxical embolism. To evaluate this further, transthoracic echocardiography with agitated saline contrast was performed and demonstrated a patent foramen ovale (PFO) with evidence of right-to-left intracardiac shunt (Figure 1C). Three recent studies provide, for the first time, data from prospective, randomized trials to guide treatment in patients with PFO and paradoxical embolism.1–3 Figure 1. Clinical studies demonstrating paradoxical embolism. A 63-year-old man presented with chest pain and subsequently developed left arm ischemia from an axillary artery thromboembolism. Clinical investigation revealed the presence of a pulmonary embolism and patent foramen ovale, supporting a diagnosis of paradoxical embolism. A , Selective angiography demonstrates occlusive thrombus in the left axillary artery (arrowhead). B , Computed tomographic angiography of the pulmonary arteries identifies a filling defect within the right lower lobe pulmonary artery (arrowhead) extending into the segmental branches of the right lower lobes. Filling defects were also observed in the left lower lobe pulmonary artery and within the segmental branches of the left lower lobe. C , Transthoracic echocardiography performed ≈5 seconds …