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

Based on the given feature description and task, it seems that the feature "n_p_ecg_p_12", which represents the presence of Complete RBBB (Right Bundle Branch Block) on ECG at the time of admission to the hospital, is expected to have a direct relationship with the presence of chronic heart failure.

Since the feature is categorical with two possible values: "no" and "yes", we can create a dictionary with the possible values of the feature for each target class.

In this case, the only possible value for the target class "no" is "no". Similarly, the only possible value for the target class "yes" is "yes". Therefore, the dictionary would be as follows:

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

Note: The dictionary only includes the values that are known or assumed to exist based on the provided information. If there are other possible values for the feature that are not specified, they are not included in the dictionary.