**Core Concept**
Acute cardiac tamponade is a life-threatening condition characterized by the accumulation of fluid in the pericardial sac, leading to compression of the heart and impaired cardiac function. This results in a decrease in cardiac output and potentially fatal hemodynamic compromise.

**Why the Correct Answer is Right**
The primary treatment for acute cardiac tamponade is pericardiocentesis, which involves the insertion of a needle or catheter into the pericardial sac to drain the accumulated fluid. This procedure is typically performed under echocardiographic guidance to ensure accurate placement and minimize complications. The relief of pressure on the heart allows for restoration of cardiac output and improves hemodynamics.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because pericardiectomy, a surgical procedure to remove the pericardium, is not the first-line treatment for acute cardiac tamponade. While it may be necessary in cases of chronic pericardial disease or recurrent tamponade, it is not the preferred initial approach.
* **Option B:** This option is incorrect because thrombolytic therapy is not indicated in the treatment of acute cardiac tamponade. In fact, thrombolytics may worsen the situation by causing bleeding within the pericardial space.
* **Option C:** This option is incorrect because beta-blockers and other vasodilators may actually worsen the hemodynamic compromise in acute cardiac tamponade by reducing cardiac output and increasing venous return.

**Clinical Pearl / High-Yield Fact**
In cases of suspected cardiac tamponade, it is essential to quickly perform a bedside ultrasound to assess the pericardial space and guide pericardiocentesis. This can be a lifesaving intervention in the emergency setting.

**Correct Answer: D. Pericardiocentesis**