This document discusses heart diseases that can affect youth, including both congenital heart defects present from birth as well as diseases that develop later in life. It notes that over the past 5-6 years, the author's hospital has performed over 2000 cardiac surgeries, with around 700 (or 1/3) being on patients under age 40, including over 40 coronary bypass surgeries on people under 40 years old. The document outlines different types of congenital and acquired heart conditions and their potential symptoms.