1. Division of Cardiology, Royal Jubilee Hospital, Victoria, BC, Canada (M.v.Z.).
2. Division of Cardiovascular Diseases, Department of Medicine (S.J.A.), Mayo Clinic, Rochester, MN.
3. Department of Pediatrics and Adolescent Medicine (S.J.A.), Mayo Clinic, Rochester, MN.
4. Department of Biomedical Engineering (S.J.A.), Mayo Clinic, Rochester, MN.
5. Department of Clinical Anatomy (S.J.A.), Mayo Clinic, Rochester, MN.