ECG Features of Pulmonary Embolism in a Patient With Normal D-Dimer and Hypoxia

Pulmonary embolism is a life-threatening condition that requires urgent treatment. We present the case of a 76-year-old male referred to our medical team with dyspnoea, shortness of breath on exertion, and chest pain. Upon further questioning, the patient reported a two-week history of right-sided parasternal pleuritic chest pain without radiation. He denied any history of haemoptysis, calf swelling or pain, recent surgery, and reduced mobility. The patient had a medical history of bilateral cataracts, glaucoma, and hypertension. Clinical examination was unremarkable except for requiring 2L/minute supplemental oxygen to maintain an oxygen saturation of 94%, and blood tests were unremarkable, including a normal D-dimer. Chest radiography revealed no obvious pathological findings. However, the electrocardiogram showed a right bundle branch, sinus tachycardia, and an S1Q3T3 pattern. A computed tomography pulmonary angiogram confirmed pulmonary emboli within the right lower lobe segmental artery, extending into the bilateral basal segmental branch and posterior basal segmental branch. The patient was commenced on low molecular weight heparin initially followed by rivaroxaban 20 mg once daily. This case highlights the importance of having a high degree of suspicion for pulmonary embolism, and D-dimer is an important screening test that can be normal.