▁Q T ▁synd rome ▁while ▁their ▁heart ▁is ▁be ating ▁in ▁its ▁normal ▁or ▁sin us ▁rh ythm . ▁ ▁C ause ▁Short ▁Q T ▁synd rome ▁is ▁a ▁gen etic ▁dis order ▁caused ▁by ▁mut ations ▁in ▁gen es ▁responsible ▁for ▁producing ▁certain ▁ion ▁channels ▁within ▁heart ▁cells . ▁ ▁It ▁appears ▁to ▁be ▁inherited ▁in ▁an ▁aut os om al ▁dominant ▁pattern . ▁Some ▁gen etic ▁variants ▁cause ▁an ▁increased ▁flow ▁of ▁pot ass ium ▁out ▁of ▁the ▁cell , ▁while ▁others ▁reduce ▁the ▁flow ▁of ▁calci um ▁into ▁the ▁cell . ▁The ▁common ▁effect ▁of ▁all ▁these ▁variants ▁is ▁to ▁short en ▁the ▁card iac ▁action ▁potential , ▁reflected ▁on ▁the ▁surface ▁E CG ▁as ▁a ▁short ening ▁of ▁the ▁Q T ▁interval . ▁ ▁A ▁list ▁of ▁gen es ▁in ▁which ▁variants ▁have ▁been ▁associated ▁with ▁short ▁Q T ▁synd rome ▁can ▁be ▁found ▁in ▁the ▁table ▁below . ▁ ▁Mechan ism ▁ ▁The ▁overall ▁effect ▁of ▁each ▁of ▁the ▁gen etic ▁variants ▁associated ▁with ▁short ▁Q T ▁synd rome ▁is ▁to ▁short en ▁the ▁card iac ▁action ▁potential , ▁which ▁in ▁turn ▁increases ▁the ▁risk ▁of ▁developing ▁ab normal ▁heart ▁rh yth ms ▁including ▁at rial ▁f ibr ill ation ▁and ▁vent ric ular ▁f ibr ill ation . ▁During ▁the ▁normal ▁rh ythm ▁of ▁the ▁heart , ▁or ▁sin us ▁rh ythm , ▁smooth ▁waves ▁of ▁elect rical ▁activity ▁pass ▁regularly ▁through ▁the ▁card iac ▁mus cle . ▁ ▁In ▁contrast , ▁during ▁at rial ▁or ▁vent