Based on prior knowledge, the use of calcium channel blockers in the ICU (ANT_CA_S_n) may have an impact on the occurrence of chronic heart failure. To analyze the relationship between this feature and the occurrence of chronic heart failure, we can examine the distribution of ANT_CA_S_n values for each target class.

Here is the dictionary with the relevant details:

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

In this case, the possible values of ANT_CA_S_n for both the "no" and "yes" target classes are ["yes", "no"].