![]() In all other cases, DCM is generally caused by viral/bacterial myocarditis, exposure to cardiotoxic substances or is a manifestation of a systemic disease. Gene mutations can be detected in 20–30% of patients with the DCM phenotype and involve proteins of the membrane-scaffolding apparatus, sarcomeric proteins, nuclear envelope proteins, calcium-handling proteins and transcription cofactors of the cell energy-generating machinery. The LV tends to become spherical and hypertrophy is eccentric. Progressive LV cavity enlargement, wall thinning and hypertrophy caused by an in-series disposition of sarcomeres with slippage of the fibers characterize DCM. In a minority of patients, the disease evolves towards severe remodeling of the LV with cavity enlargement, wall thinning and progressive impairment of systolic function, a condition known as endstage HCM. HCM is characterized by variable degrees of diastolic dysfunction that may be severe enough to cause symptoms of HF despite a normal EF. LV volumes are normal or reduced, systolic function is preserved and there is often evidence of hypercontractility with EF higher than normal and near obliteration of the cavity in systole. Hypertrophy is generally asymmetrical (with wall thickness >15 mm) and affects predominantly the interventricular septum, although it may also be symmetrical or localized to the apex or posterior wall. Impaired myofibrillar contractile function, mainly caused by abnormal cardiomyocyte calcium cycling and sensitivity, is thought to be the key mechanism triggering compensatory hypertrophy, although other factors may play a role, including disturbed biomechanical stress sensing and altered energy homeostasis. The mechanisms responsible for LVH development in HCM remain incompletely understood. Given its Mendelian inheritance, HCM was the first cardiomyopathy to be associated with a genetic origin, 7Īnd specific mutations in genes encoding sarcomeric proteins can be identified in over 50% of patients. Variable degrees of LVH are present in most forms of primary myocardial diseases, including hypertrophic (HCM) and dilated (DCM) cardiomyopathy. (Reproduced with permission from Lang RM, et al. 5Īthletes with LVH generally have a normal ejection fraction (EF) and no evidence of either systolic or diastolic dysfunction.Ĭlassification of left ventricular (LV) geometry based on relative wall thickness and LV mass index. Similarly, wall thickness in athletes has been shown to decrease significantly after deconditioning, together with cavity dimensions, although in some elite athletes, the LV cavity may remain enlarged even after cessation of training. LVM in highly trained athletes may exceed that in matched nonathletic controls by up to 60% and usually reverts to normal values after a period of deconditioning, which can take up to several years in athletes with evidence of marked LV cavity enlargement. Accordingly, athletes may develop eccentric (eg, runners) or concentric (weight lifters) LVH. The changes in cardiac structure differ depending on the type of training: dynamic exercise, such as running and swimming, produces an increase in volume load whereas static exercise, such as weight lifting, causes mainly pressure overload. Intense training results in a physiological adaptation of the heart, characterized by increased LV mass (LVM), cavity dimensions and wall thickness, known as the ‘athlete’s heart’. Noninvasive imaging allows detection of myocardial fibrosis and CMD, thus providing unique information for the stratification of patients with LVH. Coronary microvascular dysfunction (CMD) and myocardial ischemia, which have been demonstrated in most forms of pathological LVH, have an important pathogenetic role in the formation of replacement fibrosis and both contribute to the evolution towards LV dysfunction and HF. Both interstitial and replacement fibrosis play a major role in the progressive decompensation of the hypertrophied LV. Pathological LVH is a compensatory phenomenon, which eventually may become maladaptive and evolve towards progressive LV dysfunction and heart failure (HF). Physiological LVH is usually benign and regresses upon reduction/cessation of physical activity. LVH can be a physiological adaptation to strenuous physical exercise, as in athletes, or it can be a pathological condition, which is either genetic or secondary to LV overload. Left ventricular hypertrophy (LVH) is growth in left ventricular mass caused by increased cardiomyocyte size. ![]()
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