**Core Concept**
The management of massive pulmonary embolism (PE) involves restoring blood flow to the lungs, improving cardiac output, and addressing shock. This requires a comprehensive approach, including anticoagulation, thrombolytic therapy, and supportive care.

**Why the Correct Answer is Right**
Thrombolytic therapy is the most effective treatment for massive PE in shock. It involves administering medications that dissolve the clot, restoring blood flow to the lungs and improving oxygenation. This is particularly crucial in patients who are hemodynamically unstable, as it can rapidly improve cardiac output and reduce mortality. The primary mechanism of thrombolytic therapy is through the activation of plasminogen to plasmin, which breaks down fibrin clots. Commonly used thrombolytics include tissue plasminogen activator (tPA), streptokinase, and urokinase.

**Why Each Wrong Option is Incorrect**
**Option A:** Anticoagulation with heparin or low molecular weight heparin is essential in the management of PE, but it is not sufficient for massive PE in shock. While anticoagulation prevents further clot formation, it does not dissolve existing clots.
**Option B:** Vasopressors, such as norepinephrine or epinephrine, may be used to support blood pressure in patients with PE, but they do not address the underlying cause of shock. In fact, vasopressors can worsen pulmonary hypertension and further compromise cardiac output.
**Option C:** Pulmonary artery catheterization may be used to monitor hemodynamics and guide therapy in patients with PE, but it is not a treatment for massive PE in shock. In fact, the procedure carries risks, including catheter-related complications and pulmonary artery rupture.

**Clinical Pearl / High-Yield Fact**
In patients with massive PE in shock, the key is to act quickly and decisively. Thrombolytic therapy should be initiated promptly, ideally within 2 hours of diagnosis, to maximize the chances of successful treatment.

**Correct Answer:** C. Thrombolytic therapy.