Excessive stress can have the following harmful effects on a cat's internal health:
1. Leads to changes in mood and behavior
2. Sustained contraction of blood vessels in the abdominal cavity can lead to ischemia of internal organs. 
3. Prolonged vasoconstriction in peripheral small blood vessels can increase blood pressure.
4. Increases blood viscosity and promotes thrombus formation.
5. Increased heart rate leads to increased myocardial oxygen consumption, resulting in myocardial ischemia.
So, when teasing a cat, know when to stop. Don't let it turn into a mad cat, or frighten it into developing a nervous breakdown or other illnesses; that would be a real problem.
