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: A 54 - year - old man with severe left ventricular dysfunction due to dilated cardiomyopathy was referred to our hospital for symptomatic incessant sustained ventricular tachycardia ( VT ) .
### Output Text:
A 54 - year - old man with severe left ventricular dysfunction due to dilated cardiomyopathy was referred to our hospital for symptomatic incessant sustained ventricular tachycardia ( VT ) . 