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: Eighteen of 31 ( 58 % ) patients showed cardiac toxicity , defined as having one or more of the following abnormalities : late potentials , complex ventricular arrhythmias , left ventricular dilation , decreased shortening fraction , or decreased ejection fraction .
### Output Text:
Eighteen of 31 ( 58 % ) patients showed cardiac toxicity , defined as having one or more of the following abnormalities : late potentials , complex ventricular arrhythmias , left ventricular dilation , decreased shortening fraction , or decreased ejection fraction . 