"The cardiac effects of cocaine include acute myocardial infarction, ventricular dysrhythmias, and sudden cardiac death (2).
The pharmacological effects of cocaine on the cardiovascular system are varied and dose dependent. At low doses, the sympathomimetic effects of cocaine predominate resulting in tachycardia, vasoconstriction, and hypertension (2). At higher doses, cocaine-related myocardial sodium channel blockade predominates. Cocaine is a potent blocker of fast sodium channels in cardiac myocytes and conduction tissues, which has been postulated to be the mechanism of cocaine-related dysrhythmias, myocardial depression, and sudden death (3-5).
Journal of Toxicology: Clinical Toxicology, Oct 2003 v41 i6 p777(12) "
If an average person without any heart problems snorts several lines of cocaine and then proceeds to have a heart attack, then I think it is safe to say that he died from acute cocaine toxicity, manifested in a fatal heart attack. My point is, the LD50 for cocaine in rats/mice probably included a few rats/mice who died from cocaine-related dysrhythmias, myocardial depression, and sudden death. The scientists probably also didn't say "Hmm...these died of heart attacks and would not have had heart attacks just now if we didn't inject them with cocaine, but we aren't going to use their data to compute the LD50, since what we want is the lethal dose and all..."
And if I have convinced you that cocaine toxicity can be manifested in different ways (i.e. a heart attack), and that there might be a causative relationship between the two, then you might consider some of the reports of life-threatening symptoms in patients undergoing nasal surgery with cocaine used as a local anasthetic. Some of the doses reported were as low as 125mg applied on gauze to the inside of the nose. This is pure cocaine (you will never get coke this pure on the street in the US) but it is not like the patient is snorting a line-the doctor makes a point to minimize the amount of systemic absorption of the drug. Anyways, one patient had a heart attack, one had torsade des pointes (sp?), one had atrial fibrillation, etc, all life-threatening side effects from modest amounts of cocaine. I think that one of the patients died from cardiac arrest, but all of the patients could have died from the above side effects if not for the fact that the surgery was usually aborted and the symptoms promptly treated. And the toxicity mechanism here is cocaine's local anaesthetic effect when absorbed systemically (leading to conduction abnormalities in the heart).
I am not trying to propagandize for the ONDCP, but I think it's folly to say that cocaine didn't cause the death of someone who develops an irregular heartbeat and dies minutes after the coke was applied to their nose.