## 4 Discussion
Nevertheless, the literature reported that in HCM the amount of disarray is generally >20%, resulting in a sensitive and specific marker [31; 68; 72]; in one study, the mean percentage area of disarray in the ventricular septum was reported to be equal to 30 \(\pm\) 16% [22]. The increased fibrosis is another finding of HCM that was described as having variable degrees from patchy to extensive and, frequently, as being more severe in the ventricular septum [18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 73]. It is reported to be extensively severe in the left ventricle in the dilated phase of the cardiomyopathyopathy [28; 29; 30]. HCM can be also characterized by the involvement of intramyocardial coronary arteries and small vessels, which present the proliferation of intimal and medial smooth muscle cells and collagen and are then responsible for wall thickening and lumen narrowing [18; 22; 23; 29; 30]. The authors reported that intramural artery changes were observed in more than 80% of HCM cases, especially at the interventricular septum [74]. These features seem to be more common in both cases with severe fibrosis and a dilated phase of HCM [22; 75]. Regarding vascular abnormalities, myocardial bridging of the left anterior descending coronary may be observed [22]. The vascular changes can occur together with microscopic signs of subacute or acute myocardial ischemia [18; 22; 76]; in particular, the incidence of transmural myocardial infarction in the hearts of subjects who died from HCM was described as being up to 15% [77]. The abovementioned microscopic findings are considered to be the main substrate responsible for SCD, which is often the result of lethal arrhythmias. The arrhythmogenic role of myocyte disarray is well known due to the intercellular junction disorganization that negatively affects the electromechanical coupling [78]. The literature evidence highlights a greater incidence of premature SCD, which is probably related to malignant arrhythmia in the subject with extensive and severe disarray [79]. Also, fibrosis can contribute to the electrical instability which is responsible for SCD; in particular, it was reported that myocardial ischemia at any stage observed in HCM can determine a variable amount of fibrotic replacement [22]. The pathogenesis of myocardial ischemia was explained by several mechanisms mediated by intramural coronary arteries and small vessel disease or epicardial coronary myocardial bridging, in which the compromission of the blood flow can occur for both the obstruction determined by lumen narrowing and the transient compression, resulting in systolic contraction of the hypertrophic ventricle [69; 80; 81; 82]. It is known that the increase in the myocardiocyte activity causes an increase in oxygen demand, especially in the hypertrophic regions, leading to cellular hypoxia. Despite that, although myocardial blow flow events are not always associated with the onset of ischemic events, their cyclical repetition throughout the life of these subjects can be considered the basis of the remodeling phenomena characterized by the post-ischemic fibrotic replacement [83; 84]. Thus, the combination of myocardial disarray and ischemic damage is considered to be a malignant trigger for myocardial electrical instability and sudden death [22]. In some cases, death is due to heart failure, which is generally observed in the end stage of HCM (like dilated cardiomyopathy) for extensive myocardial fibrosis with marked dilatation of the ventricle [85]. Cardiac imaging using PMCT and PMMR, as also recognized by the Association for European Cardiovascular Pathology, can have an added value in contributing to the diagnosis of sudden cardiac death due to HCM [2; 86]. A study analyzing cases of SCD underlined the usefulness of PMCT angiography, which can provide data suggesting the presence of HCM such as the left ventricular hypertrophy and the asymmetrical septal hypertrophy associated with hypervascularity in the upper portion of the septum [27].