Based on my prior knowledge, the presence of a First-degree AV block on ECG at the time of admission to the hospital (n_p_ecg_p_03) can provide some insights into the likelihood of chronic heart failure.

To analyze the relationship between this feature and the presence of chronic heart failure, we can compare the distribution of n_p_ecg_p_03 for both the "yes" and "no" classes of chronic heart failure.

Here is the dictionary with the specific details:

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

In this case, the feature n_p_ecg_p_03 has two categories: "no" and "yes". For the class "no" (meaning no chronic heart failure complications), the only possible value for n_p_ecg_p_03 is "no". For the class "yes" (meaning chronic heart failure complications present), the only possible value for n_p_ecg_p_03 is "yes".

Therefore, the dictionary reflects the possible values of n_p_ecg_p_03 for each class.