Based on my prior knowledge, the feature "nr_03", which represents Paroxysms of atrial fibrillation in the anamnesis, can be related to chronic heart failure. 

Analyzing the relationship between this feature and the presence of chronic heart failure, we can create a dictionary as follows:

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

In this case, the possible values for the feature "nr_03" when the patient does not show chronic heart failure are ['no'], and when the patient does show chronic heart failure, the possible values are ['yes']. Since 'no' represents the absence of complications and 'yes' represents the presence of complications, these are the only possible values for this feature in relation to the task.