Other cases have been reported among the children of some ethnic groups in which mothers avoid exposure to the sun for religious or cultural reasons, leading to a maternal shortage of vitamin D, and people with darker skin need more sunlight to maintain vitamin D levels. Rickets had historically been a problem in London, especially during the Industrial Revolution. Persistent thick fog and heavy industrial smog permeating the city blocked out significant amounts of sunlight to such an extent that up to 80 percent of children at one time had varying degrees of rickets in one form or the other. It is sometimes known "the English Disease" in some foreign languages (e.g. German: Die englische Krankheit, Dutch: Engelse ziekte, Hungarian: angolkór). Skin color theory
Rickets is often a result of vitamin D3 deficiency. The correlation between human skin color and latitude is thought to be the result of positive selection to varying levels of solar ultraviolet radiation. Northern latitudes have selection for lighter skin that allows UV rays to produce vitamin D from 7-dehydrocholesterol.
In this procedure, the small area in which the cells initiating JET are found can be destroyed by heating or freezing the tissue. This is accomplished using wires passed to the heart via the femoral vein through a small puncture in the groin. The main risk of this procedure is accidental damage to the AV node. This occurs more frequently when treating JET than other forms of supraventricular tachycardia, requiring treatment with a pacemaker in 5-10% of ablations for JET. The risk is lower if the tissue is frozen rather than heated.For those at risk of developing JET such as children undergoing heart surgery, treatment can also be given prophylactically. A meta-analysis of 9 studies found that sedation with dexmedetomidine reduced the risk of JET occurring post-operatively. Epidemiology
JET is most commonly seen in children following cardiac surgery. The arrhythmia affects 2-22% of children depending on the type of surgery performed, with higher rates seen following repair of Tetralogy of Fallot, and lower rates following the repair of ventricular septal defects and arterial switch operations. Etymology
Junctional ectopic tachycardia derives its name from the problem it causes. "Junctional" is used as the abnormal tissue driving the ventricular rate is located close junction between the atria and ventricles, known as the AV node. Ectopic (from the Greek ektopos, meaning "out of place") refers to the fact that the ventricles are being triggered by tissue that is not the normal pacemaker tissue within the heart.