Errors in manual measurement of QT intervals.

Murray, Alan; McLaughlin, Neil; Bourke, John; Doig, J C; Furniss, Stephen S.; Campbell, R. W. F.

doi:10.1136/hrt.71.4.386

Cited by 154 publications

(65 citation statements)

References 14 publications

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“…The CSE set was annotated on multiple leads by multiple annotators very carefully and the method was well documented [16]. All primary leads were used and the annotation was performed on high resolution ECG which has been shown to affect the QT measurement [17]. The annotators of the PTB database were instructed to concentrate on only lead II.…”

Section: Discussionmentioning

confidence: 99%

Comparison of two automated methods for QT interval measurement

Gregg

Babaeizadeh

Feild

et al. 2007

2007 Computers in Cardiology

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In this paper we compared two methods of automated QT interval measurement on standard ECG databases: the Root-Mean-Square (RMS) lead combining method aimed at QT monitoring and the method of median of lead-by-lead QT interval measurements.We IntroductionGlobal QT interval is one of the fundamental ECG measurements reported on virtually every 12 lead ECG. A longer than normal QT interval may indicate a congenital or acquired long QT condition [1][2][3]. The AHA/ACC practice guideline for ECG monitoring now includes a recommendation to monitor QT interval for the purpose of drug titration of drugs known to have a pro-arrhythmic effect [4]. If the QT interval lengthens by more than 60ms after starting the drug or the QT interval extends beyond 500 ms the administration of the drug should be stopped or the dosage can be reduced.We have previously presented Philips automated QT interval measurement algorithms for 12-lead ECG, Holter and ECG monitoring applications [5][6][7][8][9][10]. In the ambulatory Holter and patient monitoring ECG applications, the QT interval algorithm uses an RMS waveform from combined available high quality leads and measures QT interval on the RMS ECG. In the resting 12-lead ECG application, the global QT interval measurement is based on a lead-by-lead method. The open question is, of the two, which method is better ignoring the constraints of the application. In this paper, we compared the two automated methods and reported the results using the same ECG datasets. Study PopulationA comparison between automated methods aimed at either monitoring or ambulatory ECG versus 12-lead ECG is hampered by the gross difference in available ECG in each case. Ambulatory ECGs cannot be used to test the 12-lead QT algorithm because of low sample rate, narrow bandwidth and limited leads. For 12-lead ECG analysis, a sample rate of 500 sps and a bandwidth of 0.05 to 150Hz are required. Ambulatory ECG recordings often have sample rates around 200 sps and a cut-off frequency of 40Hz. Only selected parts of the 12-lead analysis are possible with the small number of leads used in an ambulatory or monitoring recording. On the other hand, the sample rate, bandwidth and number of leads may be adequate for a 12-lead ECG to be used for an ambulatory analysis, but the 10 second recording is not long enough for even the learning period of the ambulatory and monitoring algorithmsThe addition of the PTB set to the data publicly available at PhysioNet made this study possible because it has the features that allow direct comparison between ambulatory and 12 lead algorithms [11]. The PTB dataset consists of 549 records from 294 subjects with a sample

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Section: Discussionmentioning

confidence: 99%

Comparison of two automated methods for QT interval measurement

Gregg

Babaeizadeh

Feild

et al. 2007

2007 Computers in Cardiology

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“…Mean values were compared between groups by use of independent samples t test, except for ECG measures, which were compared by use of 2-way ANOVA adjusting for differences in ECG paper speed, because it has an effect on estimates of QT interval measures. 18,25,26 Proportions were compared by 2 tests. Outcome rates were calculated by the product-limit method and were plotted by the Kaplan-Meier method, with comparisons of outcome rates between dichotomized groups performed with the log-rank test.…”

Section: Discussionmentioning

confidence: 99%

QRS Duration and QT Interval Predict Mortality in Hypertensive Patients With Left Ventricular Hypertrophy

et al. 2004

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Abstract-Left ventricular hypertrophy is a risk factor for cardiovascular mortality, including sudden cardiac death.Experimentally, left ventricular hypertrophy delays ventricular conduction and prolongs action potential duration. Electrocardiographic QRS duration and QT interval measures reflect these changes, but whether these measures can further stratify risk in patients with electrocardiographic left ventricular hypertrophy is unknown. We measured the QRS duration and QT intervals from the baseline 12-lead electrocardiograms in the Losartan Intervention For Endpoint Reduction in Hypertension (LIFE) study, which included hypertensive patients with electrocardiographic evidence of left ventricular hypertrophy randomized to either losartan-based or atenolol-based treatment to lower blood pressure. In the present study, we related study baseline electrocardiographic measures to cardiovascular and all-cause mortality. There were 5429 patients (male 45.8%; mean age 66Ϯ7 years) included in the present analyses. After a mean follow-up of 4.9Ϯ0.8 years, there were 417 deaths from all causes, including 214 cardiovascular deaths. In separate univariate Cox regression analyses, QRS duration and several QT measures were significant predictors of cardiovascular mortality and all-cause mortality. However, in multivariate Cox analyses including all electrocardiographic measures and adjusting for other risk factors as well as treatment strategy, only QRS duration and maximum rate-adjusted QT apex interval remained as significant independent predictors of cardiovascular (Pϭ0.022 and Pϭ0.037, respectively) and all-cause mortality (Pϭ0.038 and Pϭ0.002, respectively). In conclusion, in a hypertensive risk population identified by electrocardiographic left ventricular hypertrophy, increased QRS duration and maximum QT apex interval can further stratify mortality risk even in the setting of effective blood pressure-lowering treatment. Key Words: electrocardiography Ⅲ hypertension Ⅲ mortality Ⅲ hypertrophy L eft ventricular hypertrophy (LVH) is an important indicator of target organ damage in chronic arterial hypertension. Electrocardiographically and echocardiographically detected LVH independently predict increased morbidity and mortality, 1,2 including sudden cardiac death, 3,4 and the relative risk of these events increases with increasing LV mass. The impact of LVH on outcome may in part be mediated by adverse changes in LV mechanical function. However, LVH also induces potentially arrhythmogenic changes in LV electrophysiology. Experimental evidence shows that LVH alters ventricular conduction and repolarization. [5][6][7][8][9][10][11][12][13][14] In the 12-lead ECG, these changes may prolong the QRS and QT interval duration, respectively, and affect T-wave morphology. [15][16][17] In hypertensive patients with ECG LVH, increase in LV mass was associated with prolonged QRS and QT interval duration and measures of QT dispersion. 18 However, it is unknown if these ECG measures can further stratify risk in patients with LVH. T...

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“…To reduce the bias introduced by errors in manual measurements, all the ECGs were recorded at the same paper speed and read by two observers as has been suggested [38,39]. The mean of the two readings has been used for analysis to reduce the bias of interobserver variability [12].…”

Section: Discussionmentioning

confidence: 99%

The relation between QTc interval prolongation and diabetic complications. The EURODIAB IDDM Complication Study Group

Veglio

Borra

Stevens³

et al. 1999

Diabetologia

163

124

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The QT interval reflects the total duration of ventricular myocardial depolarization and repolarization: a prolonged QT interval is associated with sudden death and poor survival in apparently healthy subjects [1]. The relation of QT interval prolongation with diabetes complications, poor survival prognosis and sudden death has recently received considerable interest. It has been postulated that QT prolongation accounts for higher mortality in people with diabetes and its complications as the prevalence of QT interval prolongation is higher among patients with Type I (insulin-dependent) diabetes mellitus [2], ischaemic heart disease (IHD) [3±7], end stage renal disease [8] and autonomic neuropathy [2, 9±12].Data on QT interval in diabetic patients are, however, mainly derived from small, selected samples [9±15]. In particular, the prevalence of QT interval prolongation and its relation with cardiac autonomic neuropathy has been evaluated in only one cross-sec- Diabetologia (1999) Summary The prevalence of QT interval prolongation is higher in people with diabetes and its complications. Sudden death has been reported as a common cause of death in insulin-dependent diabetic patients affected by autonomic neuropathy. It has been postulated that QT prolongation predisposes to cardiac arrhythmias and sudden death. In this analysis the prevalence of QT interval prolongation and its relation with diabetic complications were evaluated in the EURODIAB IDDM Complications Study (3250 insulin-dependent diabetic patients attending 31 centres in 16 European countries). Five consecutive RR and QT intervals were measured with a ruler on the V5 lead of the resting ECG tracing and the QT interval corrected for the previous cardiac cycle length was calculated according to the Bazett's formula. The prevalence of an abnormally prolonged corrected QT was 16 % in the whole population, 11 % in males and 21 % in females (p < 0.001). The mean corrected QT was 0.412 s in males and 0.422 s in females (p < 0.001). Corrected QT duration was independently associated with age, HbA 1 c and blood pressure. Corrected QT was also correlated with ischaemic heart disease and nephropathy but this relation appeared to be stronger in males than in females. Male patients with neuropathy or impaired heart rate variability or both showed a higher mean adjusted corrected QT compared with male patients without this complication. The relation between corrected QT prolongation and autonomic neuropathy was not observed among females. In conclusion we have shown that corrected QT in insulin-dependent diabetic female patients is longer than in male patients, even in the absence of diabetic complications known to increase the risk of corrected QT prolongation. [Diabetologia (1999) 42: 68±75]

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Errors in manual measurement of QT intervals.

Cited by 154 publications

References 14 publications

Comparison of two automated methods for QT interval measurement

Comparison of two automated methods for QT interval measurement

QRS Duration and QT Interval Predict Mortality in Hypertensive Patients With Left Ventricular Hypertrophy

The relation between QTc interval prolongation and diabetic complications. The EURODIAB IDDM Complication Study Group

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