Answer to Question 1
The ventricles provide the pumping action that keeps blood moving. When the ventricles contract rapidly and uncontrollably (fibrillation), the force of the contractions is much less, sometimes drastically less. Without adequate pumping action, the heart effectively stops and hypoxemia ensues.
Answer to Question 2
paroxysm: sudden onset of a recurrent symptom
supraventricular: occurring at a point above the ventricles
tachycardia: a fast heart beat
Paroxysmal supraventricular tachycardia is a heart condition that causes the heart to beat too fast. The onset is sudden and the episodes tend to recur. The increased rhythm is caused by a lesion located in the upper portion of the heart (above the ventricles) that affects the electrical impulse of the heart.