**Core Concept**
Polycythemia vera is a myeloproliferative disorder characterized by the overproduction of red blood cells, leading to an increased risk of thrombotic complications. The condition is associated with an elevated risk of postoperative complications due to the coagulopathy.

**Why the Correct Answer is Right**
The most common postoperative complication in polycythemia vera is thrombosis, particularly venous thrombosis. This is due to the increased blood viscosity and platelet count, which can lead to a hypercoagulable state. The increased red blood cell mass also contributes to increased blood viscosity, further elevating the risk of thrombotic events. The risk of thrombosis is particularly high in the first few weeks after surgery, making perioperative management crucial.

**Why Each Wrong Option is Incorrect**
* **Option A:** Myocardial infarction is not the most common postoperative complication in polycythemia vera, although patients with this condition may have an increased risk of cardiovascular events.
* **Option B:** Pulmonary embolism is a potential complication in patients with polycythemia vera, but it is not the most common postoperative complication.
* **Option C:** Bleeding is not typically associated with polycythemia vera; in fact, patients with this condition may have an increased risk of thrombotic events.

**Clinical Pearl / High-Yield Fact**
It is essential to manage patients with polycythemia vera perioperatively with anticoagulation therapy, particularly in the first few weeks after surgery, to minimize the risk of thrombotic complications.

**Correct Answer: B. Pulmonary embolism.**