```json
{
    "no": ["no"],
    "yes": ["yes"]
}
```
Since the feature "ANT_CA_S_n" represents the use of calcium channel blockers in the ICU, and the task is to determine if the patient has chronic heart failure or not, it is difficult to predict the relationship between this feature and the target variable without additional information. 

Therefore, based on the available data, we can assume that if the patient has used calcium channel blockers in the ICU (ANT_CA_S_n = 'yes'), it may indicate a higher likelihood of chronic heart failure. Conversely, if the patient has not used calcium channel blockers in the ICU (ANT_CA_S_n = 'no'), it may indicate a lower likelihood of chronic heart failure. However, this is purely speculative without further information or analysis.

Note: If there are additional possible values for feature "ANT_CA_S_n" besides 'yes' and 'no' that are not specified in the dataset, they would not be included in the dictionary to ensure that each target class has a non-empty list.