Heart valve defects (HKF) can be classified into the following severity levels according to the New York Heart Association (NYHA):
| NYHA | Complaint level |
| I | No complaints |
| II | Complaints during heavy exertion |
| III | Complaints during light exertion |
| IV | Complaints at rest |
Aortic valve stenosis can be classified as follows:
| Grade | KÖF* (cm²) | KÖF/body surface (cm²/m²) | Mean pressure difference (mmHg) | Maximum transvalvular flow velocity (m/s) |
| Light | > 1,5 | > 1,0 | < 25 | < 3,0 |
| Medium | 1,0- 1,5 | 0,6-1,0 | 25-50 | 3,0-4,0 |
| Heavy | < 1,0 | < 0,6 | > 50 | > 4,0 |
* KÖF = valve orifice areaAortic valve regurgitation can be classified as follows:
| Grade | Regurgitation fraction |
| I | < 20 % |
| II | 20-39 % |
| III | 40-60 % |
| IV | > 60 % |
Mitral stenosis can be classified as follows:
| Grade | Mitral orifice area (cm²) | Mean pressure gradient (mmHg) | Mean pulmonary capillary pressure under stress (mmHg) |
| Slightly | < 8 | > 1,5-2,5 | < 21 |
| Medium | 8-15 | 1,0-1,5 | 21-25 |
| Heavy | > 15 | < 1,0 | > 25 |
Mitral regurgitation can be classified as follows:
| Grade | Regurgitation fraction |
| I | < 20 % |
| II | 20-39 % |
| III | 40-60 % |
| IV | > 60 % |
