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: After detailing the course of events , we discuss the role of paradoxical coronary spasm and hypotension - mediated myocardial ischemia occurring downstream to significant coronary arterial stenosis in the pathophysiology of acute coronary insufficiency .
### Output Text:
After detailing the course of events , we discuss the role of paradoxical coronary spasm and hypotension - mediated myocardial ischemia occurring downstream to significant coronary arterial stenosis in the pathophysiology of acute coronary insufficiency . 