**18. Substance abuse**

The use of marijuana and cocaine should be investigated in adolescents seen with MI. Tramadol, amphetamines, benzodiazepines and opiates are also substances that can cause PMI [61]. The use of a vasoconstrictor substance, especially by those who smoke, increases the risk of ischaemic cardiac complications, even in a healthy heart. [62]. Marijuana stimulates the sympathetic nervous system by expressing epinephrine and the effect is seen with an increase in vasoconstriction, tachycardia, hypertension and cardiac output [63]. Furthermore, by increasing the carboxyhaemoglobin level, the oxygen carrying capacity is reduced [62]. The coronary ischaemia and MI which occur as a result of increased heart rate, vasoconstriction and the increased need for oxygen can be life-threatening for the patient [63–65]. As most substances causing Paediatric MI are illegal, the users may deny having used them. In cases suspected of substance abuse, a toxicology examination must be made. Cardiac ischaemia can also be seen related to the use of bonzai, which is a synthetic cannabinoid [63].

Cocaine with sympathomimetic effect on coronary arteries can cause MI by vasoconstriction. As a result of increasing blood pressure and heart rate, the myocardium has an increased need for oxygen and with the tendency for thrombosis resulting from endothelial dysfunction, MI can develop in patients [4].

In an autopsy examination of 477 cases of sudden cardiac death aged 1–49 years, Bjune et al. determined positive results in the toxicology scan of 57% of the cases [61]. The toxicological substances determined in the blood in that study were benzodiazepines, opioids, antidepressants, anticonvulsants, antipsychotics, ethanol, cannabis, cocaine, amphetamines and gamma hydroxybutyrate. In 39% of the cases with substances determined in the blood, multiple substances were present. Despite the subpharmacological basis of the substances determined and the pharmacological dose, that death occurred was concluded to be due to the interaction of multiple drugs and/or substances.
