A patient in their mid-50s presents to the hospital with right leg swelling that started 4 days ago. He reports sudden leg swelling associated with constant 4/10 leg pain. He says his leg feels hard and is making him limp. He denies trauma or excessive exercise, chest pain, SOB, or other complaints.
Vital signs are normal except for a pulse in the 120s. The physical exam is notable for tachycardia and a swollen firm leg.
An ECG is performed:
What is the most likely cause of the ECG findings?