There is no way that a medical examiner can explicitly state the cause of death is a heart condition due to the effects of a drug that was in the person's system.

Cocaine can cause the coronary arteries to constrict, which can lead to acute ischemia and even infarction (a heart attack), but acute ischemia is damn near impossible to detect by autopsy. Chronic ischemia is easily detected, but there is no way you could definitively say that a combination of cocaine and chronic ischemia was the cause of death.

Even if acute ischemia and infarction were detected via the autopsy, there is no way that a medical examiner could say that that was the result of a drug effect. Many things can cause heart attacks, including the stress of having someone bear their full body weight on one knee pressing into your cervical spine.

Basically, all a medical examiner could say when asked if drugs caused this man's heart to stop is, "Maybe."