Heart Rate-corrected QT Research Articles

Thoracic epidural analgesia prolongs postoperative QT interval on electrocardiogram in major non-cardiac surgery: a randomized comparison and a prospective cohort analysis.

Introduction: Prolongation of QT interval on electrocardiogram can be associated with perioperative lethal arrhythmia. Epidural analgesia is a commonly used modality to relieve surgical pain by blocking sensory nerves, which also blocks the autonomic nervous system and can affect QT interval. Since patient monitoring becomes much less frequent after surgery than intraoperative period, we investigated the effects of epidural analgesia on postoperative QT interval with a randomized clinical trial and a prospective cohort study. Methods: In a randomized study, we assigned 60 patients undergoing thoracic epidural analgesia to an epidural analgesia or no-epidural analgesia group, in which 3ml/h of 0.25% epidural levobupivacaine (7.5mg/h) was administered only in the epidural analgesia group during surgery. The primary outcome was the postoperative heart rate-corrected QT interval. In a prospective cohort study, patients were assigned to receive 5ml/h epidural levobupivacaine (12.5mg/h). The plasma concentration of levobupivacaine was measured using liquid chromatography-mass spectrometry. Results: The median postoperative corrected QT interval interval with 3ml/h epidural levobupivacaine was significantly longer than that without epidural analgesia. Using multiple regression analysis for the factors known to affect postoperative corrected QT interval interval, epidural analgesia was found to be an independent variable for prolongation, and the mean difference of the corrected QT interval interval with or without epidural analgesia was 23ms after adjustment. The median plasma concentration of levobupivacaine at the end of surgery was 164ng/ml with 3ml/h epidural levobupivacaine, and the correlation coefficient to the postoperative corrected QT interval interval was 0.14, showing a not significant correlation. A prospective cohort study showed that 5ml/h epidural levobupivacaine significantly prolonged postoperative corrected QT interval interval compared to preoperative baseline. The median plasma concentration of levobupivacaine was 166ng/ml with 5ml/h, the correlation coefficient of which showed no significant correlation. Conclusion: Thoracic epidural analgesia could enhance postoperative corrected QT interval prolongation after general anesthesia. The mechanism is possibly caused by blocking neighboring or part of the cardiac sympathetic nerves, rather than by systemic effects of epidurally administered levobupivacaine. Clinical trial number: UMIN000013347 for the randomized study and UMIN000041518 for the prospective cohort study, which were registered at University hospital Medical Information Network Center.

Abstract #1403093: Absence of QT Prolongation Associated with Relacorilant, a Selective Glucocorticoid Receptor Modulator in Development for the Treatment of Cushing Syndrome

QT prolongation is a significant concern for patients with Cushing syndrome (CS). Approximately 26% of men with CS present with QT prolongation, and the risk of cardiac arrhythmic events correlates with the extent of QT prolongation. All currently approved CS medications are associated with QT prolongation, posing a significant risk for the management of CS. Here, we evaluate the impact relacorilant, an investigational selective glucocorticoid receptor modulator, on QT prolongation in healthy volunteers and patients with CS. In a 3-part, single-center, first-in-human study (NCT03508635, “phase 1 study”), 103 healthy volunteers received single or multiple ascending doses of relacorilant (up to 500 mg QD) for up to 14 days; 24 received placebo. In a randomized, partial double-blind, crossover thorough QT study (NCT04795479, “TQT study”), the effect of multiple therapeutic (400 mg QD, n=25) and supra-therapeutic (800 mg QD, n=28) doses of relacorilant on cardiac repolarization was studied in healthy volunteers. A single dose of moxifloxacin (400 mg, n=28) was used as a positive control; 29 participants received placebo. In a single-arm, open-label phase 2 study (NCT02804750, “CS study”), 17 patients with CS received low-dose relacorilant (100–200 mg QD) for 12 weeks and 18 patients received high-dose relacorilant (250–400 mg QD) for 16 weeks. In all studies, ECG data were collected, and the heart rate-corrected QT interval using Fridericia’s formula (QTcF) was assessed. In the phase 1 study, relacorilant up to 500 mg daily did not adversely affect ECG parameters. An effect on placebo-corrected change from baseline QTcF (ΔΔQTcF) above 10 msec was excluded. In the TQT study, moxifloxacin control showed the expected QT prolongation, confirming assay sensitivity. Relacorilant had no adverse effects on ECG parameters and showed effects similar to placebo. Based on concentration-QTc analysis, an effect on ΔΔQTcF exceeding 10 msec was excluded within the full observed range of relacorilant plasma concentrations. These results constitute a negative TQT study. The CS study confirmed that these favorable findings also apply to patients with CS: Throughout the CS study, no significant changes in median QTcF were observed in either dose group. There is an unmet need for medications to treat CS that do not cause QT prolongation and possibly fatal arrhythmias. Based on the TQT study and supported by additional data in healthy volunteers and patients with CS, relacorilant did not show an association with QT prolongation.

PO-04-209 A NOVEL MACHINE LEARNING (ML) ALGORITHM TO MEASURE THE CORRECTED QT INTERVAL FROM MOBILE ECGS WITH HIGH ACCURACY AND PRECISION

The heart rate-corrected QT interval (QTc) is an important feature of the electrocardiogram (ECG), as it is an important prognosticator for ventricular arrhythmia and sudden cardiac death. The 12-lead (12L) ECG is used most often for assessment of QTc, and algorithms that have extended QTc detection to mobile ECGs with fewer than 12 leads are prone to wide sample size deviation. For clinical applications requiring serial QTc monitoring, such as titration of QTc-prolonging drugs, both accuracy and precision are critical. The aim was to develop a novel machine-learning (ML) algorithm that measures QTc from mobile ECG data formats with high accuracy as well as precision. The acceptance criteria was defined as error and standard deviation within 20 milliseconds (ms), the human interobserver variability observed for manual ECG measurements (gold standard). The ML algorithm was trained using a database of 13,000 cardiologist-annotated 12L ECG heartbeats, including the following steps: 1) pre-processing including resampling to 300 Hz, 2) normalization of amplitudes using min-max scaling 3) noisy beats with excessive baseline wander were discarded, and 4) applying TabNet and XGBoost models for detection of the end of T-Wave. This ML model for detection of the T-wave endpoint was merged with a signal processing method for detection of the Q-point. The algorithm was then validated on a subset of 1,239 cardiologist-annotated heartbeats, sufficient to assess strong agreement between software and manual methods (95% CI ± 0.2 std, Bland-Altman approach). Results showed high AUC, sensitivity, and specificity for detecting QTc above clinically meaningful thresholds. Mean QTc error was 5.24±7.22 ms, meeting predefined acceptance criteria. The ML algorithm was then applied to a dataset of 150 6L mECGs (AliveCor; Mountain View, CA), which comprise an all-comer population of a combination of healthy (∼40%), outpatient clinic (30%), and hospitalized patients (30%), with error 13.7±7.78 ms, again meeting acceptance criteria. Algorithm validation surpassed the defined acceptance criteria and demonstrated that the algorithm can provide and potentially surpass human QTc measurement capabilities. By enabling automated, dynamic QTc analysis, the algorithm offered the precision required for outpatient use.

Genetic analysis identifies the SLC4A3 anion exchanger as a major gene for short QT syndrome

A variant in the SLC4A3 anion exchanger has been identified as a novel cause of short QT syndrome (SQTS), but the clinical importance of SLC4A3 as a cause of SQTS or sudden cardiac death remains unknown. The purpose of this study was to investigate the prevalence of potential disease-causing variants in SQTS patients using gene panels including SLC4A3. In this multicenter study, genetic testing was performed in 34 index patients with SQTS. The pathogenicity of novel SLC4A3variants was validated in a zebrafish embryo heart model. Potentially disease-causing variants were identified in 9 (26%) patients and were mainly (15%) located in SLC4A3: 4 patients heterozygous for novel nonsynonymous SLC4A3 variants-p.Arg600Cys, p.Arg621Trp, p.Glu852Asp, and p.Arg952His-and 1 patient with the known p.Arg370His variant. In other SQTS genes, potentially disease-causing variants were less frequent (2× in KCNQ1, 1× in KCNJ2, and CACNA1C each). SLC4A3 variant carriers (n = 5) had a similar heart rate but shorter QT and J point to T wave peak intervals than did noncarriers (n = 29). Knockdown of slc4a3 in zebrafish resulted in shortened heart rate-corrected QT intervals (calculated using the Bazett formula) that could be rescued by overexpression of the native human SLC4A3-encoded protein (AE3), but neither by the mutated AE3 variants p.Arg600Cys, p.Arg621Trp, p.Glu852Asp nor by p.Arg952His, suggesting pathogenicity of these variants. Dysfunction in slc4a3/AE3 was associated with alkaline cytosol and shortened action potential of cardiomyocytes. In about a quarter of patients with SQTS, a potentially disease-causing variant can be identified. Nonsynonymous variants in SLC4A3 represent the most common cause of SQTS, underscoring the importance of including SLC4A3 in the genetic screening of patients with SQTS or sudden cardiac death.

Prolongation of the heart rate-corrected QT interval is associated with cardiovascular diseases: Systematic review and meta-analysis

BackgroundConflicting findings have described the association between prolonged heart rate-corrected QT interval (QTc) and cardiovascular disease. AimsTo identify articles investigating the association between QTc and cardiovascular disease morbidity and mortality, and to summarize the available evidence for the general and type 2 diabetes populations. MethodsA systematic search was performed in PubMed and Embase in May 2022 to identify studies that investigated the association between QTc prolongation and cardiovascular disease in both the general and type 2 diabetes populations. Screening, full-text assessment, data extraction and risk of bias assessment were performed independently by two reviewers. Effect estimates were pooled across studies using random-effect models. ResultsOf the 59 studies included, 36 qualified for meta-analysis. Meta-analysis of the general population studies showed a significant association for: overall cardiovascular disease (fatal and non-fatal) (hazard ratio [HR] 1.68, 95% confidence interval [CI] 1.33–2.12; I2=69%); coronary heart disease (fatal and non-fatal) in women (HR 1.27, 95% CI 1.08–1.50; I2=38%; coronary heart disease (fatal and non-fatal) in men (HR 2.07, 95% CI 1.26–3.39; I2=78%); stroke (HR 1.59, 95% CI 1.29–1.96; I2=45%); sudden cardiac death (HR 1.60, 95% CI 1.14–2.25; I2=68%); and atrial fibrillation (HR 1.55, 95% CI 1.31–1.83; I2=0.0%). No significant association was found for cardiovascular disease in the type 2 diabetes population. ConclusionQTc prolongation was associated with risk of cardiovascular disease in the general population, but not in the type 2 diabetes population.

Association of QT interval-prolonging drugs with clinical trial eligibility in patients with advanced cancer.

Drug-induced prolongation of the heart rate-corrected QT interval (QTc) is associated with increased risk for the potentially fatal arrhythmia torsades de pointes. Due to arrhythmia risk, clinical trials with cancer therapeutics often exclude patients based on thresholds for QTc prolongation. Our objective was to assess associations between prescriptions for QT-prolonging drugs and the odds of meeting cancer trial exclusionary QTc thresholds in a cohort of adults with advanced cancer. Electronic health records were retrospectively reviewed for 271 patients seen at our institutional molecular solid tumor clinic. Collected data included demographics, QTc measurements, ventricular arrhythmia-related diagnoses, and all inpatient and outpatient prescriptions. Potential associations were assessed between demographic and clinical variables, including prescriptions for QT-prolonging drugs, and QTc measurements. Women had longer median QTc measurements than men (p = 0.030) and were prescribed more QT-prolonging drugs during the study (p = 0.010). In all patients, prescriptions for QT-prolonging drugs were associated with longer median and maximum QTc measurements at multiple assessed time points (i.e., for QT-prolonging drugs prescribed within 10, 30, 60, and 90 days of QTc measurements). Similarly, the number of QT-prolonging drugs prescribed was correlated with longer median and maximum QTc measurements at multiple time points. Common QTc-related exclusionary criteria were collected from a review of ClinicalTrials.gov for recent cancer clinical trials. Based on common exclusion criteria, prescriptions for QT-prolonging drugs increased the odds of trial exclusion. This study demonstrates that prescriptions for QT-prolonging drugs were associated with longer QTc measurements and increased odds of being excluded from cancer clinical trials.

Heart rate-corrected QT interval prolongation is associated with decreased heart rate variability in patients with type 2 diabetes.

We investigated the association between the heart rate-corrected QT interval (QTc interval) measured by standard electrocardiography and heart rate variability (HRV) in patients with type 2 diabetes mellitus (T2DM). From March 1, 2009, to December 12, 2009, 411 patients with T2DM who underwent resting 12-lead electrocardiography and cardiovascular autonomic function testing concurrently without the exclusion criteria were consecutively recruited in this cross-sectional study. Time- and frequency-domain HRV variables were assessed for 5 minutes by beat-to-beat HRV recording. The QT interval was corrected for the heart rate using Bazett's formula. QTc interval measurements of >440 ms were considered abnormally prolonged. The mean age and diabetes duration were 56.3 ± 10.6 years and 9.6 ± 7.3 years, respectively. A total of 90 patients had QTc interval prolongation (21.9%). The participants with a prolonged QTc interval were older (59.4 ± 10.1 years vs 55.5 ± 10.6 years, P = .002), were more likely to be a woman (72.2% vs 51.7%, P = .001), had a higher prevalence of hypertension (46.7% vs 33.4%, P = .022), had a higher hemoglobin A1c level (8.8% ± 2.2% vs 8.2% ± 1.8%, P = .045), and had decreased values for the variables measuring HRV, except for the low frequency (LF)/high frequency (HF) ratio (total power [TP], 147.7 [74.1-335.9] ms vs 328.7 [185.7-721.7] ms, P = .002). After adjusting for multiple confounders, QTc interval prolongation was associated with the lowest quartile of the HRV parameters of TP (odds ratio [OR] = 3.99; 95% confidence interval [CI]: 2.29-6.96), HF (OR = 3.20; 95% CI: 1.84-5.58), LF (OR = 3.68; 95% CI: 2.10-6.43), standard deviation of the normal-to-normal interval (OR = 3.31; 95% CI: 1.89-5.77), and root-mean-square of the successive differences (OR = 1.98; 95% CI: 1.13-3.47) in patients with T2DM. Decreased values for the variables measuring HRV, except for the LF/HF ratio, might be associated with QTc interval prolongation in patients with T2DM.

Abstract 11465: Impact of a QTc Risk Score Advisory on Mortality in Intensive Care Units

Introduction: Prolongation of the heart rate-corrected QT interval (QTc) is associated with increased mortality. We hypothesized that incorporation of a QTc prolongation risk score (QTc-RS) into a clinical decision support (CDS) advisory may reduce mortality in patients in intensive care units (ICUs). Objective: To evaluate the effectiveness of a QTc-RS risk score CDS on inpatient mortality in ICUs within hospitals in a wide geographical area. Methods: A QTc-RS CDS advisory incorporating a validated risk score using patient information available in the electronic health record was implemented throughout urban and rural facilities in the Banner Health system. Risk factors were assigned points as follows: female (1 point), age > 67 years (1), administration of a loop diuretic (1), diagnosis of acute myocardial infarction (2), serum K + ≤ 3.5 mEq/L (2), sepsis (3), diagnosis of heart failure (3), one medication with a known risk of torsades de pointes (TdP) (3), two or more medications with known risk of TdP (3), and a Fridericia-corrected QTc > 500 ms (4). The QTc-RS was automatically calculated in the background each time an order for medication with a known risk of TdP was initiated. The pre-implementation period consisted of hospitalized patients from January 1, 2020 to March 31, 2020, with QTc-RS ≥12. However, clinicians did not receive a QTc-RS CDS advisory when placing an order for a medication with a known risk of TdP for these patients. The post-implementation period was from April 1, 2020 to December 13, 2020 and included patients where clinicians received an advisory when placing an order for a medication with a known risk of TdP and the QTc-RS ≥12. Logistic regression was conducted to assess the impact of implementing the QTc-RS advisory on inpatient mortality. Results: We evaluated 620 unique hospitalized patients during the pre-implementation period and 3,112 hospitalized patients post-implementation of the CDS. Mortality was lower in the post-implementation cohort compared to that in the pre-implementation cohort (odds ratio =0.61, 95% confidence interval 0.49-0.76). Increasing QTc-RS was associated with increasing mortality [(OR=1.08 (1.02-1.14)]. Conclusion: Implementation of a QTc-RS CDS advisory was associated with lower mortality.

Abstract 13289: Risk of QT Interval Prolongation Associated With Dofetilide and Sotalol in Patients With Heart Failure With Preserved Ejection Fraction

Introduction: Heart failure (HF) with reduced ejection fraction (HFrEF) is a risk factor for drug-induced QT interval prolongation. It is unknown if HF with preserved ejection fraction (HFpEF) also increases the risk. Dofetilide (D) and sotalol (S) are potent QT interval-prolonging agents that are commonly used in patients with HFpEF, in whom atrial fibrillation is a common comorbidity. Hypothesis: The risk of QTc prolongation associated with D or S (D/S) is increased in patients with HFpEF. Methods: The data source was electronic health records from the Indiana Network for Patient Care (February 2010 to May 2021). After removing patients with overlapping diagnoses of HFpEF and HFrEF, no diagnosis code, absence of QT interval records, and no validated record of using D/S, we identified patients taking D/S among three groups: HFrEF (n=138), HFpEF (n=109), and no HF (n=729). Cochran-Mantel-Haenszel statistics were used to compare baseline characteristics. QT interval prolongation was defined as heart rate-corrected QT (QTc) > 500 ms during D/S therapy. Unadjusted odds ratios (OR) of QT interval prolongation were determined by univariate analysis, and adjusted ORs were determined by generalized estimating equations (GEE) with logit link to account for an individual cluster with different times of hospitalization and covariates. Results: QTc prolongation associated with D/S occurred in 51.2% of patients with HFpEF, 70.1% of patients with HFrEF, and 29.4% of patients with no HF. After adjusting for age, sex, race, serum potassium and magnesium concentrations, kidney function, concomitant drug therapy, and comorbid conditions, the adjusted odds of QTc prolongation were significantly higher in patients with HFpEF, as well as in those with HFrEF, compared to those with no evidence of HF (Table). Conclusions: The odds of QT interval prolongation among inpatients receiving D/S were increased in patients with HFpEF and HFrEF compared to those who did not have HF.

QTc interval in anorexia nervosa: a systematic review and meta-analysis

Abstract Background Patients with anorexia nervosa (AN) are at higher risk of sudden cardiac death. Although the underlying aetiology for this association remains unclear. It may be related to prolongation of the QT interval, which can degenerate into fatal ventricular arrhythmias. However, the presence of prolonged heart rate-corrected QT interval (QTc) in AN remains controversial, and two previous meta-analyses on AN and QTc showed contradictory findings [1,2]. Purpose In this systematic review and meta-analysis, we aimed to evaluate if AN was associated with changes in the QTc interval and dispersion. Methods MEDLINE, EMBASE and COCHRANE databases were systematically searched from inception to January 2021. Random-effects meta-analysis and meta-regression were used. The inclusion criteria were (i) confirmed diagnosis of AN, (ii) measurement of QTc on electrocardiogram and (iii) peer-reviewed articles. The primary endpoint of the study was the duration of the QTc interval calculated using the Bazett (QTcB), Hodges (QTcH), Fridericia (QTcF) and Framingham (QTcFr) formulae. The secondary endpoints were QT dispersion (QTd) and QTc dispersion (QTcd). Results The 25 eligible studies included 5687 patients (1862 AN, 3825 control) (Figure 1: PRISMA diagram). The majority of patients were female (96.3%) with a mean age between 14.3 to 31.0 years and mean duration of disease ranging from 9.1 to 129.6 months. The mean BMI ranged from 13.7 to 18.5 kg/m2. Pooled analysis did not show significant prolongation between AN versus control in QTcB (mean difference (MD) MD 4.9ms, 95% CI −3.2, 13.1ms, p=0.23; I2=95%; n=24/25 studies; Figure 2A), QTcH (MD 1.3ms, 95% CI −8.5, 11.2ms, p=0.79; I2=71%; n=3/25 studies), and QTcF (MD 3.1ms, 95% CI −21.6, 27.7ms, p=0.81; I2=97%; n=3/25 studies). Only two studies reporting QTcFr showed a significant prolongation between AN and control (MD 15.9ms, 95% CI 0.0, 31.8ms, p=0.05, I2=65%; n=2/25 studies; Figure 2B). However, QTd and QTcd were significantly greater in AN than control (MD 21.3ms, 95% CI 10.4, 32.3ms, p=0.0001, I2=94%; Figure 2C and MD 16.9ms, 95% CI 4.5, 29.3ms, p=0.007 I2=93%; Figure 2D, respectively). Conclusion To the best of our knowledge, this is the largest meta-analysis of QTc in AN and the first meta-analysis exploring the significance of QTd and QTcd in AN. AN was not found to be associated with prolongation of QTc calculated using the Bazett, Fridericia and Hodges formulae. However, an association of AN with prolonged QTc was observed in the studies using the Framingham formula. More pronounced dispersion (QTd and QTcd) was also observed in patients with AN. Funding Acknowledgement Type of funding sources: None.

Fibroblast growth factor 21 is associated with widening QRS complex and prolonged corrected QT interval in patients with stable angina

BackgroundFibroblast growth factor 21 (FGF21) is produced by cardiac cells, may acts in an autocrine manner, and was suggested to has a cardioprotective role in atherosclerosis. Wide QRS complex and heart rate-corrected QT interval (QTc interval) prolongation are associated to dangerous ventricular arrhythmias and cardiovascular disease mortality. Yet, the role of FGF21 in cardiac arrhythmia has never been studied. The aim of the study was to investigate the relationship between plasma FGF21 and the QRS duration and QTc interval in patients with stable angina.MethodsThree hundred twenty-one consecutive stable angina patients were investigated. Plasma FGF21 was measured through ELISA, and each subject underwent 12-lead electrocardiography.ResultsFGF21 plasma levels were positively associated with the QRS duration (β = 0.190, P = 0.001) and QTc interval (β = 0.277, P < 0.0001). With increasing FGF21 tertiles, the patients had higher frequencies of wide QRS complex and prolonged QTc interval. After adjusting for patients’ anthropometric parameters, the corresponding odd ratios (ORs) for wide QRS complex of the medium and high of FGF21 versus the low of FGF21 were 1.39 (95% CI 0.51–3.90) and 4.41 (95% CI 1.84–11.59), respectively, and p for trend was 0.001. Furthermore, multiple logistic regression analysis also showed the corresponding odd ratios (ORs) for prolonged QTc interval of the medium and high of FGF21 versus the low of FGF21 were 1.02 (95% CI 0.53–1.78) and 1.93 (95% CI 1.04–3.60) respectively with the p for trend of 0.037. In addition, age- and sex-adjusted FGF21 levels were positively associated with fasting glucose, HbA1c, creatinine, and adiponectin, but negatively associated with albumin, and the estimated glomerular filtration rate.ConclusionsThis study indicates that plasma FGF21 is associated with wide QRS complex and prolonged corrected QT interval in stable angina patients, further study is required to investigate the role of plasma FGF21 for the underlying pathogenesis.

Importance of Formula-Specific Centile Thresholds for Evaluation of Heart Rate-Corrected QT Prolongation in Williams Syndrome

Patients with Williams syndrome (WS) have a 25- to 100-fold higher risk of sudden death and prolonged heart rate-corrected QT (QTc). A recent study using the Fridericia formula for QT correction suggested that prolongation is principally an issue of heart rate. We used multiple published heart rate correction formulas to reevaluate the prevalence of QTc prolongation in our original dataset from our 2010 study at the Children's Hospital of Philadelphia. The ninety-eighth centile for QTc and corrected JT Interval (JTc) of the control population for each formula were used to set the threshold for prolongation. Prevalence comparison was done with Fisher's exact test. Predictors of longer QTc/JTc were assessed using linear regression models adjusting for age, gender, and heart rate. Adjusted odds of QTc/JTc prolongation were evaluated with conditional logistic regression models matched based on age and heart rate. There were 482 electrocardiograms from 188 patients with WS and 1,522 from normal controls. Patients with WS were younger, with higher heart rates and shorter RR and QRS intervals. WS was associated with longer QTc/JTc compared with controls. There were higher odds of prolonged QTc/JTc in patients with WS than controls using both Bazett and Fridericia formulas. In conclusion, this study confirms the higher prevalence of QTc prolongation in WS compared with controls and highlights the importance of setting appropriate formula-specific upper thresholds for QTc prolongation for accurate diagnosis.

Accuracy of mobile 6-lead electrocardiogram device for assessment of QT interval: aprospective validation study.

Ambulatory assessment of the heart rate-corrected QT interval (QTc) can be of diagnostic value, for example in patients on QTc-prolonging medication. Repeating sequential 12-lead electrocardiograms (ECGs) to monitor the QTc is cumbersome, but mobile ECG (mECG) devices can potentially solve this problem. As the accuracy of single-lead mECG devices is reportedly variable, amultilead mECG device may be more accurate. This prospective dual-centre study included outpatients visiting our cardiology clinics for any indication. Participants underwent an mECG recording using asmartphone-enabled 6‑lead mECG device immediately before or immediately after aconventional 12-lead ECG recording. Multiple QTc values in both recordings were manually measured in leadsI andII using the tangent method and subsequently compared. In total, 234 subjects were included (mean ± standard deviation (SD) age: 57 ± 17years; 58% males), of whom 133 (57%) had cardiac disease. QTc measurement in any lead was impossible due to artefacts in 16mECGs (7%) and no 12-lead ECGs. Mean (±SD) QTc in leadII on the mECG and 12-lead ECG was 401 ± 30 and 406 ± 31 ms, respectively. Mean (±SD) absolute difference in QTc values between both modalities was 12 ± 9 ms (r = 0.856; p < 0.001). In 55% of the subjects, the absolute difference between QTc values was < 10 ms. A6-lead mECG allows for QTc assessment with good accuracy and can be used safely in ambulatory QTc monitoring. This may improve patient satisfaction and reduce healthcare costs.

Is the association of QTc with atrial fibrillation and stroke in cohort studies a matter of time?

ObjectivesTo investigate the association of the heart rate-corrected QT interval (QTc) with the risk of atrial fibrillation (AF) and ischaemic stroke.MethodsWe estimated the risk of AF and ischaemic stroke associated...

Genotype-Specific ECG-Based Risk Stratification Approaches in Patients With Long-QT Syndrome.

BackgroundCongenital long-QT syndrome (LQTS) is a major cause of sudden cardiac death (SCD) in young individuals, calling for sophisticated risk assessment. Risk stratification, however, is challenging as the individual arrhythmic risk varies pronouncedly, even in individuals carrying the same variant.Materials and MethodsIn this study, we aimed to assess the association of different electrical parameters with the genotype and the symptoms in patients with LQTS. In addition to the heart-rate corrected QT interval (QTc), markers for regional electrical heterogeneity, such as QT dispersion (QTmax-QTmin in all ECG leads) and delta Tpeak/end (Tpeak/end V5 – Tpeak/end V2), were assessed in the 12-lead ECG at rest and during exercise testing.ResultsQTc at rest was significantly longer in symptomatic than asymptomatic patients with LQT2 (493.4 ms ± 46.5 ms vs. 419.5 ms ± 28.6 ms, p = 0.004), but surprisingly not associated with symptoms in LQT1. In contrast, post-exercise QTc (minute 4 of recovery) was significantly longer in symptomatic than asymptomatic patients with LQT1 (486.5 ms ± 7.0 ms vs. 463.3 ms ± 16.3 ms, p = 0.04), while no such difference was observed in patients with LQT2. Enhanced delta Tpeak/end and QT dispersion were only associated with symptoms in LQT1 (delta Tpeak/end 19.0 ms ± 18.1 ms vs. −4.0 ms ± 4.4 ms, p = 0.02; QT-dispersion: 54.3 ms ± 10.2 ms vs. 31.4 ms ± 10.4 ms, p = 0.01), but not in LQT2. Delta Tpeak/end was particularly discriminative after exercise, where all symptomatic patients with LQT1 had positive and all asymptomatic LQT1 patients had negative values (11.8 ± 7.9 ms vs. −7.5 ± 1.7 ms, p = 0.003).ConclusionDifferent electrical parameters can distinguish between symptomatic and asymptomatic patients in different genetic forms of LQTS. While the classical “QTc at rest” was only associated with symptoms in LQT2, post-exercise QTc helped distinguish between symptomatic and asymptomatic patients with LQT1. Enhanced regional electrical heterogeneity was only associated with symptoms in LQT1, but not in LQT2. Our findings indicate that genotype-specific risk stratification approaches based on electrical parameters could help to optimize risk assessment in LQTS.

A Combination of Heart Rate-Corrected QT Interval and GRACE Risk Score Better Predict Early Mortality in Patients with Non-ST Segment Elevation Acute Coronary Syndrome.

This study aimed to evaluate whether the addition of heart rate-corrected QT inter- val prolongation to the Global Registry of Acute Coronary Events risk score improves the pre- dictive value for early mortality in patients with non-ST segment elevation acute coronary syndrome. We retrospectively screened our database for consecutive non-ST-segment eleva- tion acute coronary syndrome patients between January 2017 and July 2019. The demographic and clinical parameters were acquired via chart review. All electrocardiograms were reviewed by 2 physicians. QT interval was measured using the tangent method. Early mortality was defined as all-cause death observed during the hospital stay or within 30 days after discharge. The final study population consisted of 283 patients, there were 17 early deaths. Ten of 59 patients with prolonged corrected QT intervals died (16.9%, P < .001). Both the Global Registry of Acute Coronary Events risk score (odds ratio: 1.032; 95% CI: 1.012-1.053; P = .002) and corrected QT interval (odds ratio: 1.026; 95% CI: 1.007-1.045; P = 0.007) independently predicted early mortality. The area under value was 0.769 (95% CI: 0.674-0.863, P < .001) for the corrected QT interval and 0.780 (95% CI:0.681-0.878; P < .001) for the Global Registry of Acute Coronary Events risk score alone. However, when the corrected QT interval and the Global Registry of Acute Coronary Events risk score were combined, it was found to be 0.808 (95% CI: 0.713-0.904, P < .001). This study is the first to report that prolonged corrected QT and the Global Registry of Acute Coronary Events risk score independently predict early mortality and a combina- tion of these 2 factors may improve the predictive value for early mortality in patients with ST-segment elevation acute coronary syndrome.

235-OR: Sustained QTc Prolongation during Recovery from Hypoglycemia in Patients with Type 1 Diabetes

Hypoglycemia and increased glycemic variability have been associated with cardiac arrhythmias and sudden cardiac death. We investigated cardiac repolarization during acute hypoglycemia followed by recovery to hyperglycemia or euglycemia in patients with type 1 diabetes. In a randomized crossover study, patients with type 1 diabetes (N=24, (mean±SD) age 53±years, HbA1c 7.5±0.8% [57.6±8.9 mmol/mol], diabetes duration 23±14 years, BMI 25.7± 3.1 kg/m2) underwent two clamps with three steady-state phases: 1) a hyperinsulinemic-euglycemic phase for 45 minutes, 2) a hyperinsulinemic-hypoglycemic phase for 60 minutes, and 3) a recovery phase in hyperglycemia (clamp A) or euglycemia (clamp B) for 60 minutes. Continuous ECG (Holter) monitoring and blood samples for counterregulatory hormones and plasma potassium were obtained. Linear mixed models were used to assess the impact of hypoglycemia and recovery to hyperglycemia vs. euglycemia on cardiac repolarization. Heart rate-corrected QT (QTc) (Fridericia’s formula) progressively increased from baseline (mean (95% CI) , clamp A: 415 msec (409;421) ; clamp B: 418 msec (412;424)) during hypoglycemia on both clamp days (∆mean (95% CI) , clamp A: 21 msec (11;31) ; clamp B: 22 msec (12;31)) . In the recovery phase, QTc remained increased during hyperglycemia and euglycemia (17 msec (11;21) vs. 14 msec (10;20)) with no difference in change between recovery to hyperglycemia compared to euglycemia (3 msec (-6;11) , P=0.5442) . No significant changes from baseline were observed in QTc dispersion (heterogeneity of myocardial repolarization) during hypoglycemia or in the recovery phases. We conclude that clinically significant QTc prolongations during insulin-induced hypoglycemia remain during a 60-minute recovery period independently of recovery to hyperglycemia or euglycemia in patients with type 1 diabetes. Thus, vulnerability for serious cardiac arrhythmias and sudden cardiac death may extend beyond a hypoglycemic event itself. Disclosure C.R.Andreasen: None. A.Andersen: n/a. P.G.Hagelqvist: None. J.V.Lauritsen: None. S.Engberg: Employee; Novo Nordisk A/S. J.J.Holst: Advisory Panel; Novo Nordisk, Board Member; Antag Therapeutics, Bainan Biotech. U.Pedersen-bjergaard: Advisory Panel; Novo Nordisk A/S, Sanofi. F.K.Knop: Advisory Panel; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Novo Nordisk, Sanofi, ShouTi, Zucara Therapeutics, Consultant; AstraZeneca, Eli Lilly and Company, Novo Nordisk, Pharmacosmos A/S, Sanofi, ShouTi, Zealand Pharma A/S, Zucara Therapeutics, Research Support; AstraZeneca, Novo Nordisk, Sanofi, Zealand Pharma A/S, Speaker's Bureau; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Stock/Shareholder; Antag Therapeutics. T.Vilsbøll: Consultant; AstraZeneca, Bristol-Myers Squibb Company, Eli Lilly and Company, Gilead Sciences, Inc., GlaxoSmithKline plc., Merck Sharp &amp; Dohme Corp., Mundipharma, Novo Nordisk, Sun Pharmaceutical Industries Ltd. Funding Danish Diabetes Academy (NNF17SA0031406)

Pharmacological characterisation of electrocardiogram J-Tpeak interval in conscious Guinea pigs

Drug-induced human ether-à-go-go-related gene (hERG) channel block and QT interval prolongation increase torsade de pointes (TdP) risk. However, some drugs block hERG channels and prolong QT interval with low TdP risk, likely because they block additional inward currents. We investigated the utility of J-Tpeak interval, a novel biomarker of inward current block and TdP risk, in conscious telemetered guinea pigs. Electrocardiogram parameters were analysed in Hartley guinea pigs orally administered one of eight test compounds (dofetilide, flecainide, nifedipine, quinidine, quinine, ranolazine, sotalol, verapamil) or vehicle alone as controls. Heart rate-corrected QT (QTcX) and J-Tpeak (J-TpeakcX) were calculated to evaluate the relations of QT–RR and J-Tpeak–RR. Dofetilide and sotalol significantly increased ΔQTcX and ΔJ-TpeakcX intervals to similar degrees. Quinidine, quinine and flecainide also increased ΔQTcX and ΔJ-TpeakcX intervals, but the degrees of ΔJ-TpeakcX interval prolongation were shorter than those of ΔQTcX interval prolongation. Ranolazine showed slight increasing trends in ΔQTcX and ΔJ-TpeakcX intervals, but the differences were not significant. Verapamil and nifedipine did not increase the ΔQTcX or ΔJ-TpeakcX intervals. Based on the relations of ΔΔJ-TpeakcX and ΔΔQTcX intervals, dofetilide, sotalol and quinidine were classified as high risk for TdP, quinine, flecainide and ranolazine were classified as intermediate risk and verapamil and nifedipine were classified as low risk. These results supported the usefulness of J-Tpeak interval assessment in conscious guinea pigs for predicting drug-induced balanced block of inward currents and TdP risk in early-stage preclinical studies.

Interleukin-6 Elevation Is a Key Pathogenic Factor Underlying COVID-19-Associated Heart Rate-Corrected QT Interval Prolongation.

BackgroundHeart rate-corrected QT interval (QTc) prolongation is prevalent in patients with severe coronavirus disease 2019 (COVID-19) and is associated with poor outcomes. Recent evidence suggests that the exaggerated host immune-inflammatory response characterizing the disease, specifically interleukin-6 (IL-6) increase, may have an important role, possibly via direct effects on cardiac electrophysiology. The aim of this study was to dissect the short-term discrete impact of IL-6 elevation on QTc in patients with severe COVID-19 infection and explore the underlying mechanisms.MethodsWe investigated the following mechanisms: (1) the QTc duration in patients with COVID-19 during the active phase and recovery, and its association with C-reactive protein (CRP) and IL-6 levels; (2) the acute impact of IL-6 administration on QTc in an in vivo guinea pig model; and (3) the electrophysiological effects of IL-6 on ventricular myocytes in vitro.ResultsIn patients with active severe COVID-19 and elevated IL-6 levels, regardless of acute myocardial injury/strain and concomitant QT-prolonging risk factors, QTc was significantly prolonged and rapidly normalized in correlation with IL-6 decrease. The direct administration of IL-6 in an in vivo guinea pig model acutely prolongs QTc duration. Moreover, ventricular myocytes incubated in vitro with IL-6 show evident prolongation in the action potential, along with significant inhibition in the rapid delayed rectifier potassium current (IKr).ConclusionFor the first time, we demonstrated that in severe COVID-19, systemic inflammatory activation can per se promote QTc prolongation via IL-6 elevation, leading to ventricular electric remodeling. Despite being transitory, such modifications may significantly contribute to arrhythmic events and associated poor outcomes in COVID-19. These findings provide a further rationale for current anti-inflammatory treatments for COVID-19, including IL-6-targeted therapies.

Declining Levels and Bioavailability of IGF-I in Cardiovascular Aging Associate With QT Prolongation-Results From the 1946 British Birth Cohort.

BackgroundAs people age, circulating levels of insulin-like growth factors (IGFs) and IGF binding protein 3 (IGFBP-3) decline. In rat cardiomyocytes, IGF-I has been shown to regulate sarcolemmal potassium channel activity and late sodium current thus impacting cardiac repolarization and the heart rate-corrected QT (QTc). However, the relationship between IGFs and IGFBP-3 with the QTc interval in humans, is unknown.ObjectivesTo examine the association of IGFs and IGFBP-3 with QTc interval in an older age population-based cohort.MethodsParticipants were from the 1946 Medical Research Council (MRC) National Survey of Health and Development (NSHD) British birth cohort. Biomarkers from blood samples at age 53 and 60–64 years (y, exposures) included IGF-I/II, IGFBP-3, IGF-I/IGFBP-3 ratio and the change (Δ) in marker levels between the 60–64 and 53y sampled timepoints. QTc (outcome) was recorded from electrocardiograms at the 60–64y timepoint. Generalized linear multivariable models with adjustments for relevant demographic and clinical factors, were used for complete-cases and repeated after multiple imputation.ResultsOne thousand four hundred forty-eight participants were included (48.3% men; QTc mean 414 ms interquartile range 26 ms). Univariate analysis revealed an association between low IGF-I and IGF-I/IGFBP-3 ratio at 60–64y with QTc prolongation [respectively: β −0.30 ms/nmol/L, (95% confidence intervals −0.44, −0.17), p < 0.001; β−28.9 ms/unit (-41.93, −15.50), p < 0.001], but not with IGF-II or IGFBP-3. No association with QTc was found for IGF biomarkers sampled at 53y, however both ΔIGF-I and ΔIGF-I/IGFBP-3 ratio were negatively associated with QTc [β −0.04 ms/nmol/L (−0.08, −0.008), p = 0.019; β −2.44 ms/unit (-4.17, −0.67), p = 0.007] while ΔIGF-II and ΔIGFBP-3 showed no association. In fully adjusted complete case and imputed models (reporting latter) low IGF-I and IGF-I/IGFBP-3 ratio at 60–64y [β −0.21 ms/nmol/L (−0.39, −0.04), p = 0.017; β −20.14 ms/unit (−36.28, −3.99), p = 0.015], steeper decline in ΔIGF-I [β −0.05 ms/nmol/L/10 years (−0.10, −0.002), p = 0.042] and shallower rise in ΔIGF-I/IGFBP-3 ratio over a decade [β −2.16 ms/unit/10 years (−4.23, −0.09), p = 0.041], were all independently associated with QTc prolongation. Independent associations with QTc were also confirmed for other previously known covariates: female sex [β 9.65 ms (6.65, 12.65), p < 0.001], increased left ventricular mass [β 0.04 ms/g (0.02, 0.06), p < 0.001] and blood potassium levels [β −5.70 ms/mmol/L (−10.23, −1.18) p = 0.014].ConclusionOver a decade, in an older age population-based cohort, declining levels and bioavailability of IGF-I associate with prolongation of the QTc interval. As QTc prolongation associates with increased risk for sudden death even in apparently healthy people, further research into the antiarrhythmic effects of IGF-I on cardiomyocytes is warranted.