**11. Hypertrophic cardiomyopathy**

Hypertrophic cardiomyopathy is characterised by a global thickening of the heart muscle. It should be kept in mind especially in children with exercise-related chest pain [36]. The incidence in the general population is 1 per 500 births and genetic transfer is autosomal dominant. Hypertrophy seen in the ventricular septum together with movement of the mitral valve anteriorally causes a narrowing of the left ventricle outlet [36]. Especially during exercise, this narrowness may cause a decrease in cardiac output and sudden death [38]. Shortness of breath and chest pain are frequent complaints. Situations such as exercise which reduces the pre-load and increases the after-load, tachycardia or dehydration, exacerbate the narrowing of the left ventricle outlet [38].

Coronary artery involvement can occasionally be seen in Takayasu arteritis, which tends to involve larger vessels than PAN [48–50]. It has also been reported that Paediatric MI can be

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http://dx.doi.org/10.5772/intechopen.74793

Slow coronary flow phenomenon is a microvascular disease characterised by slow progress of the contrast dye within the vessel, which is not obstructive coronary artery flow [51]. Despite evaluation as a benign clinical setting, it is concerning for families and physicians because of the relationship with MI and anginal symptoms. In addition, the mechanism and clinical

Occasionally, clinical findings can be seen in children with ST-segment elevation myocardial infarction (STEMI) [51]. On coronary angiography, there is no vessel obstruction or it is close to normal, but the peripheral blood flow is noticeably slow. Studies of these patients have shown cellular oedema, thickening in the capillary endothelium, fibromuscular hyperplasia, myofibril disorganisation and microvascular thickening, causing endothelial dysfunction [52, 53].

As atherosclerotic coronary artery disease seen in adults originates in childhood, it is necessary to start taking preventative measures against atherosclerosis in that period. However, as there are few cases related to atherosclerosis within the PMI cases reported in literature it is thought that MI cases developing on an atherosclerotic basis are rare in children [3, 7, 54].

In an autopsy study of 760 murder or accident cases aged 15–34 years, atheroma was determined in males at 2% and was not determined in females [54]. Other risk factors increasing

seen in Behçet's disease [45].

**Table 7.** Diagnostic criteria for PAN.

**1.** Arteriographic abnormality

**4.** Livedo reticularis

**6.** Myalgias

**9.** Weight loss

**2.** Diastolic blood pressure > 90 mmHg

**5.** Mononeuropathy or polyneuropathy

**8.** Testicular pain or tenderness

**7.** Presence of hepatitis B reactants in serum

**3.** Elevated blood nitrogen or serum creatinine

**15. Atherosclerosis**

**14. Slow coronary flow phenomenon**

**10.** Biopsy-confirmed granulocytic or mixed leukocytic infiltrate in an arterial wall

outcomes of the disease are not yet fully understood.
