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: BACKGROUND AND AIM OF THE STUDY : Undersized mitral annuloplasty ( MAP ) is effective in patients with dilated cardiomyopathy and functional mitral regurgitation ( MR ) since , as well as addressing the MR , the MAP may also reshape the dilated left ventricular ( LV ) base .
### Output Text:
BACKGROUND AND AIM OF THE STUDY : Undersized mitral annuloplasty ( MAP ) is effective in patients with dilated cardiomyopathy and functional mitral regurgitation ( MR ) since , as well as addressing the MR , the MAP may also reshape the dilated left ventricular ( LV ) base . 