Methodology of QT-interval measurement in the modular ECG analysis system (MEANS)

Impact of QRS misclassifications on heart-rate-variability parameters (results from the CARLA cohort study)

BACKGROUND

Heart rate variability (HRV), an important marker of autonomic nervous system activity, is usually determined from electrocardiogram (ECG) recordings corrected for extrasystoles and artifacts. Especially in large population-based studies, computer-based algorithms are used to determine RR intervals. The Modular ECG Analysis System MEANS is a widely used tool, especially in large studies. The aim of this study was therefore to evaluate MEANS for its ability to detect non-sinus ECG beats and artifacts and to compare HRV parameters in relation to ECG processing. Additionally, we analyzed how ECG processing affects the statistical association of HRV with cardiovascular disease (CVD) risk factors.

METHODS

20-min ECGs from 1,674 subjects of the population-based CARLA study were available for HRV analysis. All ECGs were processed with the ECG computer program MEANS. A reference standard was established by experienced clinicians who visually inspected the MEANS-processed ECGs and reclassified beats if necessary. HRV parameters were calculated for 5-minute segments selected from the original 20-minute ECG. The effects of misclassified typified normal beats on i) HRV calculation and ii) the associations of CVD risk factors (sex, age, diabetes, myocardial infarction) with HRV were modeled using linear regression.

RESULTS

Compared to the reference standard, MEANS correctly classified 99% of all beats. The averaged sensitivity of MEANS across all ECGs to detect non-sinus beats was 76% [95% CI: 74.1;78.5], but for supraventricular extrasystoles detection sensitivity dropped to 38% [95% CI: 36.8;38.5]. Time-domain parameters were less affected by false sinus beats than frequency parameters. Compared to the reference standard, MEANS resulted in a higher SDNN on average (mean absolute difference 1.4ms [95% CI: 1.0;1.7], relative 4.9%). Other HRV parameters were also overestimated as well (between 6.5 and 29%). The effect estimates for the association of CVD risk factors with HRV did not differ between the editing methods.

CONCLUSION

We have shown that the use of the automated MEANS algorithm may lead to an overestimation of HRV due to the misclassification of non-sinus beats, especially in frequency domain parameters. However, in population-based studies, this has no effect on the observed associations of HRV with risk factors, and therefore an automated ECG analyzing algorithm as MEANS can be recommended here for the determination of HRV parameters.

Surface Electrocardiographic Parameters of Children and Adolescents Diagnosed with Attention-Deficit/Hyperactivity Disorder in an Ambulatory Community Pediatric Center: A Focus on Cardiac Repolarization Electrocardiogram Intervals

Objectives: Our research aims were to determine if repolarization measures (QTcF, QTcB, JTcF, and JTcB) in attention-deficit/hyperactivity disorder (ADHD) children and adolescents differ from normal subjects and determine if the JTc interval duration, as a purer repolarization measure than QTc, strengthens the differentiation between ADHD and normal children and adolescents. Methods: This study included 418 subjects aged 5-18 years who were diagnosed with ADHD, and 1948 subjects in a historical normal control group. One-way analysis of variance (ANOVA) was performed to compare the independent groups on normal continuous outcomes. Means and standard deviations (SDs) were reported and interpreted for the ANOVA. Logistic regression analysis was performed to test the ability of four variables (QTcB, QTcF, JTcB, and JTcF) to predict an ADHD diagnosis, with age and gender as independent covariates. The log odds with standard errors for each variable were reported and interpreted for the logistic models. Results: In the nominal logistic regressions with JTcF ≥322 or JTcB ≥335 (values 1 SD above the mean of the control group), age and sex were significant contributors to the models that showed that subjects with a JTcF ≥322 ms had a statistically and significantly higher probability to be diagnosed with ADHD in comparison with normal control subjects (odds ratio [OR]: 2.6, 95% confidence interval [95% CI] 2.02-3.33, p < 0.0001). Similarly, those subjects with a JTcB ≥335 ms were 2.7 times more likely to be diagnosed with ADHD than normal control subjects (OR: 2.7, 95% CI 2.1-3.45, p < 0.0001). Conclusions: JTc provided a clearer separation of the groups than QTc. JTcB and JTcF 1 SD above the control group means are strong predictors of ADHD diagnosis and remain so even when strong demographic predictors of longer QTc (age and sex) are included in the regression models. Consideration should be given to recording a pretreatment electrocardiogram in all children and adolescents with ADHD, and to measuring and monitoring JTc in patients with ADHD, especially when considering the addition of QT prolonging drugs.

A computational investigation into rate-dependant vectorcardiogram changes due to specific fibrosis patterns in non-ischæmic dilated cardiomyopathy

Patients with scar-associated fibrotic tissue remodelling are at greater risk of ventricular arrhythmic events, but current methods to detect the presence of such remodelling require invasive procedures. We present here a potential method to detect the presence, location and dimensions of scar using pacing-dependent changes in the vectorcardiogram (VCG). Using a clinically-derived whole-torso computational model, simulations were conducted at both slow and rapid pacing for a variety of scar patterns within the myocardium, with various VCG-derived metrics being calculated, with changes in these metrics being assessed for their ability to discern the presence and size of scar. Our results indicate that differences in the dipole angle at the end of the QRS complex and differences in the QRS area and duration may be used to predict scar properties. Using machine learning techniques, we were also able to predict the location of the scar to high accuracy, using only these VCG-derived rate-dependent changes as input. Such a non-invasive predictive tool for the presence of scar represents a potentially useful clinical tool for identifying patients at arrhythmic risk.

Electrical remodeling after percutaneous atrial septal defect closure in pediatric and adult patients

BACKGROUND

Several studies have reported changes in electrocardiographic variables after atrial septal defect (ASD) closure. However no temporal electro-and vectorcardiographic changes have been described from acute to long-term follow-up at different ages. We aimed to study electrical remodeling after percutaneous ASD closure in pediatric and adult patients.

METHODS

ECGs of 69 children and 75 adults (median age 6 [IQR 4-11] years and 45 [IQR 33-54] years, respectively) were retrospectively selected before percutaneous ASD closure and at acute (1-7 days), intermediate (4-14 weeks) and late (6-18 months) follow-up. Apart from electrocardiographic variables, spatial QRS-T angle and ventricular gradient (VG) were derived from mathematically-synthesized vectorcardiograms.

RESULTS

In both pediatric and adult patients, the heart rate decreased immediately post-closure, which persisted to late follow-up. The P-wave amplitude also decreased acutely post-closure, but remained unchanged at later follow-up. The PQ duration shortened immediately in children and at intermediate follow-up in adults. The QRS duration and QTc interval decreased at intermediate-term follow-up in both children and adults. In both groups the spatial QRS-T angle decreased at late follow-up. The VG magnitude increased at intermediate follow-up in children and at late follow-up in adults, after an initial decrease in children.

CONCLUSION

In both pediatric and adult ASD patients, electrocardiographic changes mainly occurred directly after ASD closure except for shortening of QRS duration and QTc interval, which occurred at later follow-up. Adults also showed late changes in PQ duration. At 6-to-18 month post-closure, the spatial QRS-T angle decreased, reflecting increased electrocardiographic concordance. The initial acute decrease in VG in children, which was followed by a significant increase, may be the effect of action potential duration dynamics directly after percutaneous ASD closure.

Antidepressants and heart-rate variability in older adults: a population-based study

BACKGROUND

Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) may be associated with lower heart rate variability (HRV), a condition associated with increased mortality risk. We aimed to investigate the association between TCAs, SSRIs and HRV in a population-based study.

METHOD

In the prospective Rotterdam Study cohort, up to five electrocardiograms (ECGs) per participant were recorded (1991-2012). Two HRV variables were studied based on 10-s ECG recordings: standard deviation of normal-to-normal RR intervals (SDNN) and root mean square of successive RR interval differences (RMSSD). We compared the HRV on ECGs recorded during use of antidepressants with the HRV on ECGs recorded during non-use of any antidepressant. Additionally, we analysed the change in HRV on consecutive ECGs. Those who started or stopped using antidepressants before the second ECG were compared with non-users on two ECGs.

RESULTS

We included 23 647 ECGs from 11 729 participants (59% women, mean age 64.6 years at baseline). Compared to ECGs recorded during non-use of antidepressants (n = 22 971), SDNN and RMSSD were lower in ECGs recorded during use of TCAs (n = 296) and SSRIs (n = 380). Participants who started using TCAs before the second ECG had a decrease in HRV and those who stopped had an increase in HRV compared to consistent non-users (p < 0.001). Starting or stopping SSRIs was not associated with HRV changes.

CONCLUSION

TCAs were associated with a lower HRV in all analyses, indicating a real drug effect. For SSRIs the results are mixed, indicating a weaker association, possibly due to other factors.

Drugs and ventricular repolarization in a general population: the Rotterdam Study

PURPOSE

Prolonged ventricular repolarization (measured as heart-rate corrected QT (QTc) prolongation or JT-interval prolongation) is a risk factor for ventricular arrhythmias and can be drug-induced. Drugs can be classified as having known or possible QTc-prolonging properties. Regulatory agencies recommend avoiding concomitant use of multiple QTc-prolonging drugs, but evidence is lacking to what degree ventricular repolarization is influenced by concomitant use of these drugs.

METHODS

Within a population-based cohort of persons aged 45 years and older, with up to five electrocardiograms recorded per participant between 1991 and 2010, we used generalised estimating equations to study the association between concomitant use of multiple QTc-prolonging drugs and repolarization duration.

RESULTS

The study population consisted of 13 009 participants with 26 908 electrocardiograms. With the addition of a second or third QTc-prolonging drug there was no substantial increase in QTc and JT interval and no increased risk of a prolonged QTc interval, compared to use of one QTc-prolonging drug. There was a large difference between the effect of one known or one possible QTc-prolonging drugs on QTc interval: 15 ms for known, and 3 ms for possible QTc-prolonging drugs.

CONCLUSIONS

In this study, the added prolongation in users of two or three QTc-prolonging drugs on QTc was small. There was a large difference in QTc prolongation between known and possible QTc-prolonging drugs. Further research in larger or high-risk populations is needed to establish whether it is safe to use multiple QTc-prolonging drugs concomitantly to prevent that the current advice might unnecessarily withhold beneficial drugs from patients.

Use of selective serotonin re-uptake inhibitors and the heart rate corrected QT interval in a real-life setting: the population-based Rotterdam Study

AIMS

Selective serotonin re-uptake inhibitors (SSRIs), specifically citalopram and escitalopram, are thought to cause QTc prolongation, although studies have shown contradictory results. Nevertheless, a maximum citalopram dosage of 20 mg in high risk patients (e.g. >60 years of age) is recommended. We aimed to investigate the association between use of (individual) SSRIs and QTc in a population-based study in older adults.

METHODS

This study, which was part of the prospective Rotterdam Study (period 1991-2012), included participants with up to five electrocardiograms (ECGs). We used linear mixed models to compare QTc F (QT corrected according to Fridericia) measured during use of individual SSRIs with QTc F measured during non-use of any antidepressant. For citalopram, analyses were additionally restricted to a maximum dosage of 20 mg in participants aged 60 years and older.

RESULTS

We included 12 589 participants with a total of 26 620 ECGs of which 436 ECGs were made during SSRI use. The mean QTc F was similar during use of any drugs from the SSRI class and during non-use. After stratifying to individual SSRIs, ECGs recorded during use of citalopram had the longest QTc compared with ECGs recorded during non-use (+12.8 ms, 90% CI 7.5, 18.2). This result remained similar in the analysis comprising participants aged 60 years and older with a maximum prescribed daily dosage of 20 mg citalopram.

CONCLUSIONS

Although no SSRI class effect was observed, use of citalopram was associated with a longer QTc F, even after considering the recommended restrictions. Other SSRIs may not give a clinically relevant QTc F prolongation.

Consistency of heart rate-QTc prolongation consistency and sudden cardiac death: The Rotterdam Study

BACKGROUND

A prolonged heart rate-corrected QT (QTc) interval is a well-known risk indicator for sudden cardiac death (SCD) and a contraindication for drugs with potentially arrhythmogenic adverse effects.

OBJECTIVE

We aimed to study the consistency of QTc interval prolongation and whether a consistent QTc interval prolongation correlates differently with SCD than does an inconsistently prolonged QTc interval.

METHODS

We used a population-based cohort study of persons 55 years and older. We excluded participants using QTc-prolonging drugs or with bundle branch block. The QT interval was corrected for heart rate using Bazett and Fridericia formulas. Using a Cox regression model, we assessed the association between QTc interval prolongation consistency and the occurrence of SCD.

RESULTS

A total of 3484 participants had electrocardiograms (ECGs) recorded on 2 consecutive visits. In 96%-98% of participants with a normal QTc interval on the first ECG, the QTc interval remained normal, but only in 27%-35% of those with a prolonged QTc interval, the QTc interval was prolonged on the second ECG after a median of 1.8 years. A consistently prolonged QTc interval was associated with an increased risk of SCD as compared with a consistently normal QTc interval (Bazett: hazard ratio 2.23; 95% confidence interval 1.17-4.24, Fridericia: hazard ratio 6.67; 95% confidence interval 2.96-15.06). A prolonged QTc interval preceded or followed by a normal QTc interval was not significantly associated with an increased risk of SCD.

CONCLUSION

Persons with an inconsistently prolonged QTc interval did not have a higher risk of SCD than those with a consistently normal QTc interval. Persons with a consistently prolonged QTc interval did have a higher risk of SCD. Our results suggest that repeated measurements of the QTc interval could enhance risk stratification.

Inflammation and prolonged QT time: results from the Cardiovascular Disease, Living and Ageing in Halle (CARLA) study

Background

Previous research found an association of CRP with QT time in population based samples. Even more, there is evidence of a substantial involvement of the tumor necrosis factor-alpha system in the pathophysiology of cardiac arrhythmia, while the role of Interleukin 6 remains inconclusive.

Objective

To determine the association between inflammation with an abnormally prolonged QT-time (APQT) in men and women of the elderly general population.

Methods

Data descend from the baseline examination of the prospective, population-based Cardiovascular Disease, Living and Ageing in Halle (CARLA) Study. After exclusion of subjects with atrial fibrillation and missing ECG recording the final study cohort consisted of 919 men and 797 women. Blood parameters of inflammation were the soluble TNF-Receptor 1 (sTNF-R1), the high-sensitive C-reactive protein (hsCRP), and Interleukin 6 (IL-6). In accordance with major cardiologic societies we defined an APQT above a QT time of 460 ms in women and 450 ms in men. Effect sizes and the corresponding 95% confidence intervals (CI) were estimated by performing multiple linear and logistic regression analyses including the analysis of sex differences by interaction terms.

Results

After covariate adjustment we found an odds ratio (OR) of 1.89 (95% CI: 1.13, 3.17) per 1000 pg/mL increase of sTNF-R1 in women, and 0.74 (95% CI: 0.48, 1.15) in men. In the covariate adjusted linear regression sTNF-R1 was again positively associated with QT time in women (5.75 ms per 1000 pg/mL, 95% CI: 1.32, 10.18), but not in men. Taking possible confounders into account IL-6 and hsCRP were not significantly related to APQT in both sexes.

Conclusion

Our findings from cross-sectional analyses give evidence for an involvement of TNF-alpha in the pathology of APQT in women.

Highly automated QT measurement techniques in 7 thorough QT studies implemented under ICH E14 guidelines

Thorough QT (TQT) studies are designed to evaluate potential effect of a novel drug on the ventricular repolarization process of the heart using QTc prolongation as a surrogate marker for torsades de pointes. The current process to measure the QT intervals from the thousands of electrocardiograms is lengthy and expensive. In this study, we propose a validation of a highly automatic-QT interval measurement (HA-QT) method. We applied a HA-QT method to the data from 7 TQT studies. We investigated both the placebo and baseline-adjusted QTc interval prolongation induced by moxifloxacin (positive control drug) at the time of expected peak concentration. The comparative analysis evaluated the time course of moxifloxacin-induced QTc prolongation in one study as well. The absolute HA-QT data were longer than the FDA-approved QTc data. This trend was not different between ECGs from the moxifloxacin and placebo arms: 9.6 ± 24 ms on drug and 9.8 ± 25 ms on placebo. The difference between methods vanished when comparing the placebo-baseline-adjusted QTc prolongation (1.4 ± 2.8 ms, P = 0.4). The differences in precision between the HA-QT and the FDA-approved measurements were not statistically different from zero: 0.1 ± 0.1 ms (P = 0.7). Also, the time course of the moxifloxacin-induced QTc prolongation adjusted for placebo was not statistically different between measurements methods.

Genetic variation in NOS1AP is associated with sudden cardiac death: evidence from the Rotterdam Study

Common variation within the nitric oxide-1 synthase activator protein (NOS1AP) locus is strongly related to QT interval, a sudden cardiac death (SCD) risk factor. A recent report describes common variation in NOS1AP associated with SCD in a US population of European ancestry. The objective of the current study was to obtain additional evidence by investigating the association between NOS1AP variants and SCD in the prospective population-based Rotterdam Study. The study population consisted of 5974 European ancestry subjects, aged 55 years and older, genotyped on Illumina arrays. SCD was defined according to European Society of Cardiology guidelines. Smoking, body mass index, diabetes mellitus, hypertension, heart failure and myocardial infarction were used as covariates in Cox proportional hazard models. Results were combined with reported evidence using inverse-variance weighted meta-analysis. Two hundred and eight (109 witnessed) cases of SCD occurred during a mean follow-up of 10.4 years. Within the Rotterdam Study alone, no significant associations were observed. Upon pooling of results with existing data, we observed strengthening of existing evidence for rs16847549 (US data HR = 1.31, P = 0.0024; Rotterdam Study HR = 1.18, P = 0.16; joint HR = 1.26, P = 0.0011). When the case definition in the Rotterdam Study was restricted to witnessed SCD, association of rs16847549 with SCD became stronger (joint P = 0.00019) and additionally the association between rs12567209 and SCD gained significance (US data HR = 0.57, P = 0.0035; Rotterdam Study HR = 0.69, P = 0.23; joint HR = 0.60, P = 0.0018). In conclusion, this study provided additional evidence for association between genetic variation within NOS1AP and SCD. The mechanism by which this effect is exerted remains to be elucidated.