Based on the given feature description and task, it is not clear how the feature "ANT_CA_S_n" relates to the presence of chronic heart failure in the patient. The feature represents the use of calcium channel blockers in the ICU, but there is no direct information about how this variable is related to chronic heart failure.

Nevertheless, we can still analyze the relationship between the feature and the target variable and create a dictionary with possible values based on the available information. Here is an example of a dictionary that can be created:

```json
{
	"no": ["yes", "no"],  
	"yes": ["yes", "no"]
}
```
Please note that this dictionary includes all the possible values of the "ANT_CA_S_n" feature for both the "no" and "yes" classes of chronic heart failure. However, since we don't have specific information about the relationship between the feature and the target, we cannot provide a more accurate analysis.