Based on prior knowledge, frequent premature ventricular contractions on ECG at the time of admission to the hospital (n_r_ecg_p_04) can be an indicator of chronic heart failure. Thus, it is reasonable to assume that if the value of n_r_ecg_p_04 is "yes", it might suggest the presence of chronic heart failure.

Here is the dictionary generated based on this analysis:

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

In this case, the only possible value for n_r_ecg_p_04 is "yes". If there were other possible values, they would be included in the respective lists for each target class.