Based on my prior knowledge, the RestingECG feature can provide valuable information in determining the presence of heart disease. Here is the analysis of the relationship between the RestingECG feature and the target variable:

- Normal RestingECG (category: 'Normal'): It is likely that a normal RestingECG indicates the absence of heart disease, so it might be associated with the target class 'no'.
- ST-T wave abnormality (category: 'ST'): The presence of ST-T wave abnormalities in the RestingECG could be indicative of heart disease, so it might be associated with the target class 'yes'.
- Left ventricular hypertrophy (category: 'LVH'): Left ventricular hypertrophy is a condition often associated with heart disease, so it might also be associated with the target class 'yes'.

Based on this analysis, the dictionary with the possible values for each target class is as follows:

```json
{
    "no": ["Normal"],
    "yes": ["ST", "LVH"]
}
```

Please note that this analysis assumes a general relationship between the RestingECG feature and heart disease. As data and domain-specific knowledge are crucial in such cases, it is always recommended to validate these assumptions with further information and medical expertise.