## **Core Concept**
Thrombolytic therapy is a treatment used to dissolve blood clots that have formed in a patient's vascular system. It involves the administration of drugs that activate plasminogen to form plasmin, which then breaks down the clot. However, this therapy carries a risk of bleeding, and certain conditions increase this risk to an unacceptable level.

## **Why the Correct Answer is Right**
The correct answer, **D. Active bleeding or high risk of bleeding**, represents a scenario where the administration of thrombolytic therapy could lead to catastrophic consequences, including uncontrollable bleeding. This is because thrombolytic agents work by dissolving clots, and if there's already active bleeding or a high risk of it, these agents can exacerbate the bleeding, leading to severe morbidity or mortality.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Pregnancy is not an absolute contraindication to thrombolytic therapy. In certain life-threatening situations, the benefits of thrombolysis may outweigh the risks.
- **Option B:** Recent surgery is a relative contraindication. The risk of bleeding is increased, but it's not an absolute contraindication, as the decision to use thrombolytic therapy depends on the balance between the risk of bleeding and the need to dissolve the clot.
- **Option C:** History of stroke can be a contraindication, but it depends on the timing and type of stroke. Generally, an ischemic stroke within the past 3-6 months is considered a relative contraindication, not absolute.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that absolute contraindications to thrombolytic therapy include **active internal bleeding**, **suspected aortic dissection**, **pericarditis or myocarditis**, and **recent intracranial hemorrhage**. Always assess the risk-benefit ratio in patients with potential contraindications.

## **Correct Answer:** D. Active bleeding or high risk of bleeding.