Cavalier King Charles Spaniel vs Italian Greyhound

Heart disease isn't a risk for Cavaliers so much as a near-certainty — about half develop a heart murmur from mitral valve disease by age 5, and veterinary sources note that essentially every Cavalier that lives long enough will eventually develop it, making it the breed's leading cause of death.

Beneath the elegant looks this is a genuinely fragile dog — thin skin, minimal body fat, and slight bone structure mean Italian Greyhounds can fracture a leg jumping off furniture that wouldn't scratch most breeds, and like other sighthounds they need anesthesia protocols adjusted for low body fat; many breeders won't place a puppy in a home with children under 10 for exactly this reason.