Section 870.3945 - Prosthetic heart valve sizer(a)Identification. A prosthetic heart valve sizer is a device used to measure the size of the natural valve opening to determine the size of the appropriate replacement heart valve.(b)Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 870.9 .45 FR 7907, Feb. 5, 1980, as amended at 61 FR 1121, Jan. 16, 1996; 66 FR 38797 , July 25, 2001