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

Based on the given feature description, the feature "ritm_ecg_p_07" represents the ECG rhythm at the time of admission to the hospital. It is a categorical variable with two possible categories: "no" and "yes".

To analyze its relationship with the target variable ("chronic heart failure"), we need additional information about the data and its labeling. Unfortunately, no such information is provided in the given task description. Consequently, we cannot determine the specific relationship between the feature "ritm_ecg_p_07" and the presence of chronic heart failure. All we know is that the feature represents the ECG rhythm at admission with two possible values.

Therefore, the dictionary includes the two possible values of the feature for each target class, as requested in the given format.