What is Sic Sinus Syndrome of the heart?

Answer 1

Read the wiki page

Sick Sinus Syndrome (of the heart) is an uncommon condition where the Sino-Atrial Node (hence sinus) which normally tells the heart when to beat is "sick". There is some sort of disease affecting it - often from Ischaemic Heart Disease (a heart attack can affect it), but various other disease can also affect this important part of the heart.

The end result is that the bit that generates the start of the heart beat can trigger off too fast (tachycardia) or too slow (bradycardia) and can cause people to have chest pains or collapses.