Statistical and deterministic approaches to designing transformations of electrocardiographic leads

Journal of Electrocardiology

Gregg

et al. 2013

Background Substantial new information has emerged recently about the prognostic value for a variety of new ECG variables. The objective of the present study was to establish reference standards for these novel risk predictors in a large, ethnically diverse cohort of healthy women from the Women's Health Initiative (WHI) study. Methods and results The study population consisted of 36,299 healthy racially diverse women. Racial differences in rate-adjusted QT end (QTea) and QT peak (QTpa) intervals as linear functions of RR were small, leading to the conclusion that 450 ms and 390 ms are applicable as thresholds for prolonged and shortened QTea and similarly, 365 ms and 295 for prolonged and shortened QTpa, respectively. As a threshold for increased dispersion of global repolarization (TpeakTend interval), 110 ms was established for white and Hispanic women and 120 ms for African-American and Asian women. Normal standards were derived using lead transformation matrix computed from 116 lead body surface potential maps to derive normal standards for ST monitoring with limb electrodes in Mason-Likar positions and chest leads V3-V6 at the level of V1-V2 and for bipolar vessel-specific left anterior descending (LAD), left circumflex (LCX) and right coronary artery (RCA) leads. The results support the choice 150 μV as a tentative threshold for abnormal ST onset elevation for all monitoring leads. Body mass index (BMI) had a profound effect on Cornell voltage and Sokolow-Lyon voltage in all racial groups and their utility for left ventricular hypertrophy classification remains open. Conclusions Common thresholds for all racial groups are applicable for QTea, and QTpa intervals and ST elevation. Race-specific normal standards are required for many other ECG parameters.

Section: Methodsmentioning

confidence: 99%

Normal standards for computer-ECG programs for prognostically and diagnostically important ECG variables derived from a large ethnically diverse female cohort: The Women's Health Initiative (WHI)

Journal of Electrocardiology

Gregg

et al. 2013

“…18 Spatial QRS|T angle (Ѳ(QRS|STT)) was derived as the angle between the mean QRS and STT vectors. Nondipolar QRS voltage (RNDPV) was computed from singular-value decomposition of QRS as the RMS value of the pooled variance of components 4 to 8.…”

Section: Methodsmentioning

confidence: 99%

Different Patterns of Bundle-Branch Blocks and the Risk of Incident Heart Failure in the Women’s Health Initiative (WHI) Study

Soliman

et al. 2013

Circ: Heart Failure

H eart failure (HF) as a consequence of ischemic, hypertensive, or valvular heart disease is known to be more common in bundle-branch blocks (BBBs) than in normal ventricular conduction. Left BBB (LBBB) has been associated with excess risk of incident HF in some studies, 1-4 but right BBB (RBBB) has not been found to predict incident HF. [5][6][7] Overall, available data are limited about specific BBB categories as predictors of incident HF, particularly in women. Therefore, the aim of the present study was to evaluate independent prognostic significance of BBBs in predicting incident HF, and further to evaluate whether repolarization abnormalities associated with BBBs contain additional prognostic information. Clinical Perspective on p 661 Methods Study Population and DesignThe Women's Health Initiative (WHI) study is a multicenter investigation of risk factors for the prevention of common causes of mortality, morbidity, and impaired quality of life in United States-postmenopausal women. Detailed eligibility criteria and recruitment methods, randomization, follow-up, data and safety monitoring, and quality assurance have been published previously. [8][9][10] The study was approved by the Institutional Review Board of each study site. All participants provided written informed consent. Of the 68 133 WHI clinical trial participants who were enrolled from 1993 to 1998, we excluded 2158 participants from analyses: 960 participants with no ECG data, 614 with inadequate quality ECG, 109 with an external pacemaker or Wolff-ParkinsonWhite pattern, and 475 participants with prevalent HF (self-report) at baseline. In the remaining group of 65 975 participants, 1676 had BBBs, and 64 299 had no BBBs (Figure). Background-We evaluated the risk of incident heart failure (HF) associated with bundle-branch blocks (BBBs) in postmenopausal women. Methods and Results-Cox's regression was used to evaluate hazard ratios with 95% confidence intervals for HF among 65 975 participants of the Women's Health Initiative (WHI) study during an average follow-up of 14 years. BBBs observed in 1676 women at baseline were categorized into left, right, and indetermined-type BBBs (LBBB, RBBB, and intraventricular conduction defect, respectively). Compared with women with no BBB, LBBB, and intraventricular conduction defect were strong predictors of incident HF in multivariable-adjusted risk models (hazard ratio, 3.79; confidence interval, 2.95-4.87 for LBBB and hazard ratio, 3.53; confidence interval, 2.14-5.81 for intraventricular conduction defect). RBBB was not a significant predictor of incident HF in multivariable-adjusted risk model, but the combination of RBBB and left anterior fascicular block was a strong predictor (hazard ratio, 2.96; confidence interval, 1.77-4.93). QRS duration was an independent predictor of incident HF only in LBBB, with more pronounced risk at QRS ≥140 ms than at <140 ms. QRS nondipolar voltage (RNDPV) was an independent predictor in both RBBB and LBBB and, in addition, in LBBB, QRS/STT angle and ST J-point depress...

“…The orthogonal Frank XYZ leads were obtained from the 8 independent components (leads I, II, V1 to V6) using a transformation matrix from the 116‐lead body surface map library of Horáĉek containing recordings for 892 adults aged 16 to 85 years. 15 Repolarization measurements were made utilizing temporal reference points derived from the spatial T‐vector magnitude curve derived from the XYZ leads (the “global” T wave), including QT end (QT e ), QTpeak (QT p ), and QTonset (QT o ) intervals. QT e , QT p , and QT o intervals were rate adjusted (QT ea , QT pa and QT oa , respectively) as linear functions of the RR interval with the following formulas derived in the CVD‐free group: QT ea =QT e +184×(1−RR), QT pa =QT p +135×(1−RR) and QT oa =QT o +113×(1−RR).…”

Section: Methodsmentioning

confidence: 99%

Electrocardiographic Repolarization‐Related Variables as Predictors of Coronary Heart Disease Death in the Women's Health Initiative Study

Vitolins

et al. 2014

JAHA

BackgroundWe evaluated 25 repolarization‐related ECG variables for the risk of coronary heart disease (CHD) death in 52 994 postmenopausal women from the Women's Health Initiative study.Methods and ResultsHazard ratios from Cox regression were computed for subgroups of women with and without cardiovascular disease (CVD). During the average follow‐up of 16.9 years, 941 CHD deaths occurred. Based on electrophysiological considerations, 2 sets of ECG variables with low correlations were considered as candidates for independent predictors of CHD death: Set 1, Ѳ(Tp|Tref), the spatial angle between T peak (Tp) and normal T reference (Tref) vectors; Ѳ(Tinit|Tterm), the angle between the initial and terminal T vectors; STJ depression in V6 and rate‐adjusted QTp interval (QTpa); and Set 2, TaVR and TV1 amplitudes, heart rate, and QRS duration. Strong independent predictors with over 2‐fold increased risk for CHD death in women with and without CVD were Ѳ(Tp|Tref) >42° from Set 1 and TaVR amplitude >−100 μV from Set 2. The risk for these CHD death predictors remained significant after multivariable adjustment for demographic/clinical factors. Other significant predictors for CHD death in fully adjusted risk models were Ѳ(Tinit|Tterm) >30°, TV1 >175 μV, and QRS duration >100 ms.ConclusionsѲ(Tp|Tref) angle and TaVR amplitude are associated with CHD mortality in postmenopausal women. The use of these measures to identify high‐risk women for further diagnostic evaluation or more intense preventive intervention warrants further study.Clinical Trial RegistrationURL: http://www.clinicaltrials.gov. Unique identifier: NCT00000611.