Based on my prior knowledge, frequent premature atrial contractions on an electrocardiogram (ECG) can be an indicator of chronic heart failure. Therefore, it is likely that the presence of frequent premature atrial contractions ('yes' category) in the n_r_ecg_p_02 feature suggests chronic heart failure in the patient.

Here is the dictionary with the possible values of the n_r_ecg_p_02 feature for each target class:

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

Since the feature is a categorical variable with categories 'no' and 'yes', the 'no' target class will only have the value 'no' and the 'yes' target class will only have the value 'yes'.