专业笔试(8:00--11:00)ISurgeonsliketosaythatwhensomeonesuffersaheartattack,timeismuscle.Theheartdependsonacontinuoussupplyofoxygenfromthecoronaryarteries;ifthesebecomeblockedandthatsupplystops,theheart’smusclecellsstarttodieoffwithinjustafewminutes.Inmanycases,unlesssurgeonscanrelievetheblockagewithinthehour,morethan1billionmusclecellsareirreversiblylost.Thosewhosurviveareoftenleftwithpermanentheartfailure–agroupwhichincludesapproximately450,000peopleintheUK.Withinthefiveyearsfollowinganattack,50%ofthemwillnolongerbealive.Eventuallytheirheartsbecomesoweakthattheycan’tsustainsufficientbloodflowandtheyjuststopaltogether.Atthemoment,theonlymedicaloptionforpatientswithheartfailureisahearttransplant.Butalackofdonororgansmeansthatjust200oftheseoperationscanbeperformedintheUKeachyear.There’sonlyaverysmallpoolofpeoplewho’vedied,intrafficaccidentsorthroughheadinjuries,wheretheheartisstillstrongandcanbeusedforatransplant.Stemcellmedicinemayprovideanalternative.Inclinicaltrials,scientistshaveattemptedtoremuscularisedamagedheartsbyinjectingindividualstemcells–whichcandevelopintomanydifferenttypes–fromthepatient’sbloodorbonemarrowdirectlyintotheheart.