Based on my prior knowledge, the presence of an anterior myocardial infarction can be a risk factor for chronic heart failure. Infarction of the left ventricular leads V1 - V4 can lead to the development or worsening of heart failure.

Here is the dictionary with the relationship between the feature "ant_im" and the task of determining chronic heart failure:

```json
{
	"no": ["QRS has no changes", "there is no infarct in this location"],
	"yes": ["QRS is like QS-complex", "QRS is like QR-complex", "QRS is like Qr-complex"]
}
```

In this case, the values of "ant_im" that indicate the absence of an anterior myocardial infarction ("QRS has no changes", "there is no infarct in this location") are associated with a lower likelihood of chronic heart failure. On the other hand, the values that indicate the presence of an anterior infarction ("QRS is like QS-complex", "QRS is like QR-complex", "QRS is like Qr-complex") are associated with a higher likelihood of chronic heart failure.