<unk>  (from Latin<unk> n of the heart - a functional effect of mechanical stimulation in the absence of structural damage, as opposed to myocardial contusion which involves tissue damage) is a sudden disturbance of heart rhythm observed nowadays mostly in young people during participation in sports. It occurs as the result of a blunt, non-penetrating impact to the precordial region, often caused by impact of a ball, a bat or other projectile. The impact is transmitted to the heart muscle, and depending on the precise timing in relation to the cardiac cycle, it may affect the heart's electrical activity, causing an arrhythmia, such as an ectopic beat, ventricular tachycardia or ventricular fibrillation.
Pre-existing conditions, such as undetected electrical or structural abnormalities in the heart of these individuals, have been speculated to render individuals more vulnerable, but this view is not currently corroborated by hard evidence. The phenomenon was confirmed experimentally in the 1930s, with research in anaesthetized rabbits, cats and dogs.
Commotio cordis
Epiphora 
Cutis rhomboidalis nuchae
White piedra
Balanitis circinata
Cutis marmorata
Tentorium cerebelli
Duplessis Orphans