Predictive value of beat-to-beat QT variability index across the continuum of left ventricular dysfunction: competing risks of noncardiac or cardiovascular death and sudden or nonsudden cardiac death.
BACKGROUND
The goal of the present study was to determine the predictive value of beat-to-beat QT variability in heart failure patients across the continuum of left ventricular dysfunction.


RESULTS
Beat-to-beat QT variability index (QTVI), log-transformed heart rate variance, normalized QT variance, and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca heart failure study (mean age, 63.1±11.7; men, 70.6%; left ventricular ejection fraction >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death (subhazard ratio, 1.67 [95% CI, 1.14-2.47]; P=0.009) and, in particular, with non-SCD (subhazard ratio, 2.91 [1.69-5.01]; P<0.001). Elevated QTVI separated 97.5% of healthy individuals from subjects at risk for cardiovascular (subhazard ratio, 1.57 [1.04-2.35]; P=0.031) and non-SCD in multivariate competing risk model (subhazard ratio, 2.58 [1.13-3.78]; P=0.001). No interaction between QTVI and left ventricular ejection fraction was found. QTVI predicted neither noncardiac death (P=0.546) nor SCD (P=0.945). Decreased heart rate variability rather than increased QT variability was the reason for increased QTVI in the present study.


CONCLUSIONS
Increased QTVI because of depressed heart rate variability predicts cardiovascular mortality and non-SCD but neither SCD nor extracardiac mortality in heart failure across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from heart failure patients at risk.
Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA. lteresh1@jhmi.edu
Larisa G
LG
Tereshchenko
Iwona
I
Cygankiewicz
Scott
S
McNitt
Rafael
R
Vazquez
Antoni
A
Bayes-Genis
Lichy
L
Han
Sanjoli
S
Sur
Jean-Philippe
JP
Couderc
Ronald D
RD
Berger
Antoni Bayes
AB
de Luna
Wojciech
W
Zareba
D000368:Aged; D016022:Case-Control Studies; D002423:Cause of Death; D016009:Chi-Square Distribution; D016757:Death, Sudden, Cardiac / Q000209:etiology*; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006333:Heart Failure / Q000150:complications / Q000175:diagnosis* / Q000401:mortality* / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D013318:Stroke Volume; D016019:Survival Analysis; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality* / Q000503:physiopathology; D016277:Ventricular Function, Left