Based on prior knowledge, a first-degree AV block on an electrocardiogram (ECG) at the time of admission to the hospital can be related to chronic heart failure. 

To analyze the relationship between the feature `n_p_ecg_p_03` (First-degree AV block on ECG at the time of admission to hospital) and the task of determining if the patient has chronic heart failure, we can examine the distribution of `n_p_ecg_p_03` values for each target class.

The dictionary for this feature would then be as follows:

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

Note that since the feature is categorical and only has two categories ('no' and 'yes'), we include all possible values for each target class.