In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The primary outcome was new or worsening valvulopathy , defined as progression of either aortic or mitral regurgitation by at least one degree of severity and disease that met U . S .
### Output Text:
The primary outcome was new or worsening valvulopathy , defined as progression of either aortic or mitral regurgitation by at least one degree of severity and disease that met U . S . 