Based on the given feature "ANT_CA_S_n" which represents the use of calcium channel blockers in the ICU, it is important to analyze its relationship with the task of identifying chronic heart failure.

Analysis:
Calcium channel blockers are commonly used to treat various cardiovascular conditions including hypertension and certain arrhythmias. However, their use in the ICU specifically for myocardial infarction complications may have slightly different implications.

Chronic heart failure is a long-term condition characterized by the heart's inability to pump enough blood to meet the body's needs. It is often caused by underlying cardiovascular diseases such as hypertension or previous myocardial infarctions. While calcium channel blockers can be effective in managing hypertension, they are not typically the first-line treatment for chronic heart failure.

With this analysis, we can infer that the use of calcium channel blockers in the ICU for myocardial infarction complications is less likely to indicate chronic heart failure. Therefore, patients who have used calcium channel blockers are less likely to have chronic heart failure.

Based on this analysis, the dictionary can be defined as follows:

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

The "no" category represents patients without chronic heart failure and their possible values for the feature "ANT_CA_S_n" are "yes". The "yes" category represents patients with chronic heart failure and their possible values for the feature "ANT_CA_S_n" are "no".