Correlation of QT interval correction methods during atrial fibrillation and sinus rhythm

doi:10.3760/cma.j.issn.1673-4777.2014.05.002

Abstract：Objective To compare the QT interval (QTc) during atrial tbrillation (AF).Methods A total of 30 patients with persistent AF receiving catheter ablation (CA) were enrolled.We selected 20 sex-and agematched patients with paroxysmal supraventricular tachycardia(PSVT) who underwent CA.None of the patients had factors that might have impact on QT interval including drugs,severe ischemia,electrode disorders and recent cardioversion.QT interval was measured 1 day before CA under AF rhythm and immediate after CA under SR.At each measurement,at least 3 consecutive QRS complexes were taken.QTc was corrected with the cardiac cycle length and calculated using three formulas:Bazett,Fridericia and Framingham.Sinus rhythm (SR) was restored spontaneously by CA without applying any medication or cardioversion.Results Average heart rate was similar during AF and SR[(89 ± 15) times/min vs (82 ± 11) times/min,P =0.06].Regardless of the formula used to correct QT interval,a self-controlled comparison indicated that there was no signifcant difference of QTc before and after CA in patients with PSVT[(436 ± 17)ms vs (437 ± 14)ms,P =0.837; (411 ± 16)ms vs (421 ± 13)ms,P =0.151 ; (412 ± 14) ms vs (422 ± 12) ms,P =0.110] and there was no signifcant difference of QTc during AF and SR[(441 ±42)ms vs (436 ±28)ms,P =0.398;(412 ±27)ms vs (413 ±36)ms,P=0.887;(408 ±25)ms vs (409 ± 31)ms,P =0.762].However,during AF,QTc showed much less strong correlation coefficients with cardiac cycle length when assessed by Framingham formula (correlation coeffcients:-0.399,-0.088,-0.031).Conclusions QTc during persistent AF is not different from that during SR when QT interval is corrected by using Bazett,Fridericia or Framingham formula.During AF,QTc is seldom influenced by cardiac cycle length when Framingham formula is applied.