```json
{
    "no": ["no"],
    "yes": ["yes"]
}
```

Based on the feature description and task, the relationship between the feature "NITR_S" and the target variable is straightforward. The possible values for the feature "NITR_S" are categorical with two options: "no" and "yes". 

In this case, since the task is to determine if the patient shows chronic heart failure, the presence of liquid nitrates in the ICU ("NITR_S" feature) could potentially indicate chronic heart failure. So, if the value of "NITR_S" is "yes", it indicates that the patient does show chronic heart failure.

Therefore, the dictionary representation shows that for the target class "no", the "NITR_S" feature has the possible value of "no", and for the target class "yes", the "NITR_S" feature has the possible value of "yes".