Final answer:
Echocardiography is the test used to confirm pericardial tamponade, allowing visualization of excess fluid in the pericardial space that compromises heart function.
Step-by-step explanation:
The test used to confirm pericardial tamponade is echocardiography. An echocardiogram (ECG or ECHO) utilizes ultrasound technology to create images of the heart, which allows physicians to observe the heart's valves and chambers, determining if they are functioning correctly. In the context of pericardial tamponade, an echocardiogram can visualize the excess fluid within the pericardial space that restricts the heart's ability to relax and fill with blood, reducing the volume of blood ejected from the heart with each beat. This condition, if untreated, can be life-threatening, necessitating prompt diagnosis and often requiring the insertion of drainage tubes into the pericardial cavity to remove the excess fluid.