Based on my prior knowledge, frequent premature ventricular contractions on an electrocardiogram (ECG) at the time of admission to the hospital can be an indicator of underlying heart conditions, including chronic heart failure. However, it is important to note that not all patients with these contractions will develop chronic heart failure, and further medical evaluation is required to confirm the presence of this complication.

Based on the given task, we need to analyze the relationship between the feature "n_r_ecg_p_04" and the presence of chronic heart failure. Let's create a dictionary to summarize the possible values of "n_r_ecg_p_04" for each target class:

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

In this case, since the feature "n_r_ecg_p_04" is a binary categorical variable with categories 'yes' and 'no', the possible values for the target class "no" would be "no" only, and for the target class "yes" it would be "yes" only.

Please note that this dictionary assumes that the only possible values for the feature "n_r_ecg_p_04" are 'yes' and 'no'. If there are additional possible values or if hard to predict values are encountered, they should be included accordingly.