?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=The+fallacies+of+QT+correction&rft.creator=Lokhandwala%2C+Yash&rft.creator=SC%2C+Toal&rft.subject=Indian+Pacing+and+Electrophysiology+Journal&rft.description=Not+to+correct+QT%2C+but+how+to%2C+that+is+the+question%E2%80%9D.+The+QT+interval+is+a+reflection+of+the+action+potential+in+the+cardiac+cells.+Homogenous+or+heterogenous+changes+in+the+action+potential+duration+lead+to+alteration+of+QT+interval+(in+addition+to+morphological+changes+of+T+%26+U+waves)+1.++Such+changes+can+be+due+to+change+in+heart+rate+%26+autonomic+tone.+They+can+also+be+markers+of+abnormal+repolarization%2C+depolarization+or+both+as+a+result+of+electrolyte+disturbances%2C+cardiac+diseases%2C+drugs+and+congenital+long+QT+syndromes+2.+%0A++++++++Repolarization+disorders+are+responsible+for+life+threatening+arrhythmias+like+torsades+de+pointes2.+The+purpose+of+heart+rate+correction+is+to+obtain+a+standardized+value+that+would+have+been+measured+in+the+same+subject+if+the+heart+rate+was+60+beats+per+minute+(QTc).+Thus+this+QTc+value+will+now+become+independent+of+the+heart+rate+and+measure+replarization+changes.+It+will+thus+be+a+surrogate+marker+of+the+risk+of+torsade+de+pointes.%0A++++++++The+concept+of+QTc+appeared+in+1920%2C+when+Bazett+introduced+his+square+root+formula+3.+This+formula+obtained+from+data+on+39+young+men+has+been+questioned+because+it+overcorrects+QT+at+fast+heart+rate+and+undercorrects+at+low+heart+rate+(4).+Thus+at+slow+heart+rate%2C+which+is+one+of+the+predisposing+factors+of+torsade+initiation%2C+Bazett+correction+can+easily+mask+substantial+QT+prolongation+by+under+correcting.+This+can+hide+the+proarrhythmic+toxicity+of+drugs+slowing+heart+rate.+An+alternative%2C+cube+root+correction+of+Fridericia%2C+corrects+better+than+Bazett+but+again+is+not+reliable+at+fast+heart+rates.+Compared+to+these+non+linear+correction+formulae%2C+linear+regression+correction+obtained+from+large+population+data%2C+like+the+Framingham+heart+study+linear+correction+are+still+better+4.+%0A&rft.publisher=Indian+Pacing+and+Electrophysiology+Group&rft.contributor=Singh%2C+Balbir&rft.contributor=Lokhandwala%2C+Yash&rft.contributor=Francis%2C+Johnson&rft.contributor=Gupta%2C+Anup&rft.date=2003-10&rft.type=Journal+(Paginated)&rft.type=PeerReviewed&rft.format=text%2Fhtml&rft.identifier=http%3A%2F%2Fcogprints.org%2F4241%2F1%2Fyash2.htm&rft.identifier=++Lokhandwala%2C+Yash+and+SC%2C+Toal++(2003)+The+fallacies+of+QT+correction.++%5BJournal+(Paginated)%5D+++++&rft.relation=http%3A%2F%2Fcogprints.org%2F4241%2F