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

Based on the given feature, "B_BLOK_S_n" which represents the use of beta-blockers in the ICU, we can analyze the relationship between this feature and the presence of chronic heart failure, as indicated by the myocardial infarction complications data of the patient.

Since the feature is a categorical variable with two categories: "no" and "yes", we can assume that this indicates whether or not beta-blockers were used in the ICU for the patient.

To determine if there is a relationship between the use of beta-blockers and chronic heart failure, we would need additional information or data. It's important to note that this analysis is based solely on the given feature, without considering other variables or data.

In the provided dictionary, we present the possible values of the feature "B_BLOK_S_n" for each target class.

For the "no" class, which represents patients without chronic heart failure, the only possible value of the feature is "no".

For the "yes" class, which represents patients with chronic heart failure, the only possible value of the feature is "yes".

Remember that this analysis is purely based on the feature-description given and does not take into account other factors that may affect the relationship between the use of beta-blockers and chronic heart failure.