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: An increase in TDR by dl - sotalol facilitated transmural propagation of EADs that initiated multiple episodes of spontaneous TdP in 3 of 6 rabbit left ventricles .
### Output Text:
An increase in TDR by dl - <span class="chemical">sotalol</span> facilitated transmural propagation of EADs that initiated multiple episodes of spontaneous TdP in 3 of 6 rabbit left ventricles . 