```json
{
	"no": ["no"],  
	"yes": ["yes"]
}
```
Given that the feature "n_p_ecg_p_04" represents the presence or absence of Type 1 Second-degree AV block (Mobitz I/Wenckebach) on ECG at the time of admission to the hospital, the possible values for this feature are "no" and "yes". 

Based on the task of determining whether the myocardial infarction complications data of the patient shows chronic heart failure, it is clear that the presence of Type 1 Second-degree AV block (Mobitz I/Wenckebach) on ECG at the time of admission to the hospital may be indicative of chronic heart failure.

Therefore, for the target class "no" (indicating no chronic heart failure), the possible values for the feature "n_p_ecg_p_04" are ["no"]. Similarly, for the target class "yes" (indicating chronic heart failure), the possible values for the feature "n_p_ecg_p_04" are ["yes"].