If something goes wrong when a patient is undergoing medical treatment, it is called a medical accident or an adverse event. If the treatment does not work or there have been complications, it does not always mean that there has been a mistake, or that someone is to blame.  

In certain cases, one has to accept that errors or complications are unavoidable risks of the treatment and the healthcare professional would not be considered to be to blame.  

For instance, when one undergoes a major heart surgery, the patient can expect that there will be risks because of the surgery. Moreover, there can be complications with minor procedures as well.