Based on prior knowledge, we can 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 presence of chronic heart failure in patients.

It is important to note that First-degree AV block on ECG is a condition where the electrical conduction in the heart is delayed as it passes through the atrioventricular (AV) node. This condition can vary in severity and might or might not be associated with chronic heart failure. Therefore, we cannot definitively determine the presence of chronic heart failure based solely on the presence of First-degree AV block on ECG.

To create the dictionary, we need to analyze the possible values of "n_p_ecg_p_03" for each target class (yes or no) in the myocardial infarction complications data.

Here is the dictionary with the possible values of "n_p_ecg_p_03" for each target class:

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

Note: In this case, since "n_p_ecg_p_03" is a categorical variable, we include all possible categories ("no" and "yes") for each target class, even if they might be hard to predict or occur very rarely.