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

Based on the provided feature description, the feature "n_p_ecg_p_12" is a categorical variable that represents the presence of Complete Right Bundle Branch Block (RBBB) on an electrocardiogram (ECG) at the time of admission to the hospital. 

To determine if the patient has chronic heart failure (CHF), we would need additional information or features to analyze. The feature "n_p_ecg_p_12" alone does not provide enough information to directly infer the presence or absence of CHF.

The possible values for the feature "n_p_ecg_p_12" are 'no' and 'yes'. However, without more detailed information about the relationship between this feature and the presence of CHF, it is not possible to determine the specific values of "n_p_ecg_p_12" that indicate CHF. Therefore, the dictionary only includes the available values 'no' and 'yes' for each target class, even if it is feasible that other values could exist.