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

Based on the feature description, the possible values for the feature ritm_ecg_p_08 are "no" and "yes". It is a categorical variable with two categories. Since the task is to determine if the patient shows chronic heart failure, the only relevant value in this feature is "yes". If the patient has chronic heart failure, the feature value would be "yes", indicating that the ECG rhythm at the time of admission to the hospital is sinus with a heart rate below 60. Therefore, the only possible value for target class "no" is "no", and the possible value for target class "yes" is "yes".