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

Based on the feature description, the feature np_08 represents the presence of Complete LBBB (Left Bundle Branch Block) in the patient's medical history. It is a categorical variable with two possible categories: "no" and "yes".

To analyze the relationship between this feature and the task of determining whether the patient has chronic heart failure or not, we need to look for any patterns or associations between the feature values and the target variable. 

Since the feature represents the presence of Complete LBBB in the patient's medical history, it is possible that patients with Complete LBBB are more likely to have chronic heart failure. This suggests that the presence of Complete LBBB (value "yes") may be associated with a higher likelihood of chronic heart failure. On the other hand, patients without Complete LBBB (value "no") may be less likely to have chronic heart failure.

Therefore, we can create a dictionary with the possible values of the feature np_08 for each target class:

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

Please note that this analysis is based on prior knowledge and assumptions. Further analysis and statistical testing would be required to confirm the relationship between the feature and the target variable.