Related Clues:

• Tough spot
• Shoelace woe
• Difficulty
• The way to a person's heart?
• Vital carrier
• Unit of speed
• Place for a valve
• Main stream
• Main line from the heart
• Angiogram image
• Its walls withstand a lot of pressure
• Line from the heart
• Cardiological concern
• Hitch, e.g.
• Blood carrier