```json
{
  "no": ["no"],
  "yes": ["yes"]
}
```
Since the feature "B_BLOK_S_n" represents the use of beta-blockers in the ICU, it seems logical to assume that patients who did not use beta-blockers ("no" category) may have a higher likelihood of experiencing chronic heart failure. On the other hand, patients who did use beta-blockers ("yes" category) may have a lower likelihood of developing chronic heart failure.