Which one of the following statements regarding prosthetic heart valves is correct?
Antibiotic prophylaxis is still recommended for patients with mechanical valves who have dental procedures
The majority of mechanical valves are of the ball-and-cage type
Bioprosthetic valves are now usually obtained from human cadavers
The target INR for patients with mechanical aortic valves is 3.0-4.0
Mechanical valves have a lower failure rate than bioprosthetic valves