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 evaluation consisted of a history , physical examination , electrocardiogram ( ECG ) , signal averaged ECG , 24 - hour ambulatory ECG , echocardiography and radionuclide angiography .
### Output Text:
The evaluation consisted of a history , physical examination , electrocardiogram ( ECG ) , signal averaged ECG , 24 - hour ambulatory ECG , echocardiography and radionuclide angiography . 