Pulseless electrical activity, or PEA, can cause cardiac arrest and occurs when any medical disorder causes severe hypotension during which the blood pressure drops critically low to the point where peripheral pulses are not palpable.
Cardiac tamponade occurs when a pericardial effusion exerts a significant amount of pressure externally on the heart, resulting in impaired right ventricular filling eventually causing decreased cardiac output and hypotension.
Hypotension is an abnormally low blood pressure. This can occur for many reasons; however, the most common causes include shock and medication side effects.