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: Spontaneous coronary thrombosis or thromboembolism with subsequent clot lysis has been suggested as one of the most common causes of myocardial infarction ( MI ) during pregnancy , with a subsequently normal coronary angiogram .
### Output Text:
Spontaneous coronary thrombosis or thromboembolism with subsequent clot lysis has been suggested as one of the most common causes of myocardial infarction ( MI ) during pregnancy , with a subsequently normal coronary angiogram . 