QT interval: how to measure it and what is "normal"

The best QT correction formula in a non-hospitalized population: the Fasa PERSIAN cohort study

Background

QT interval as an indicator of ventricular repolarization is a clinically important parameter on an electrocardiogram (ECG). QT prolongation predisposes individuals to different ventricular arrhythmias and sudden cardiac death. The current study aimed to identify the best heart rate corrected QT interval for a non-hospitalized Iranian population based on cardiovascular mortality.

Methods

Using Fasa PERSIAN cohort study data, this study enrolled 7071 subjects aged 35–70 years. Corrected QT intervals (QTc) were calculated by the QT interval measured by Cardiax® software from ECGs and 6 different correction formulas (Bazett, Fridericia, Dmitrienko, Framingham, Hodges, and Rautaharju). Mortality status was checked using an annual telephone-based follow-up and a minimum 3-year follow-up for each participant. Bland–Altman, QTc/RR regression, sensitivity analysis, and Cox regression were performed in IBM SPSS Statistics v23 to find the best QT. Also, for calculating the upper and lower limits of normal of different QT correction formulas, 3952 healthy subjects were selected.

Results

In this study, 56.4% of participants were female, and the mean age was 48.60 ± 9.35 years. Age, heart rate in females, and QT interval in males were significantly higher. The smallest slopes of QTc/RR analysis were related to Fridericia in males and Rautaharju followed by Fridericia in females. Thus, Fridericia’s formula was identified as the best mathematical formula and Bazett’s as the worst in males. In the sensitivity analysis, however, Bazett’s formula had the highest sensitivity (23.07%) among all others in cardiac mortality. Also, in the Cox regression analysis, Bazett’s formula was better than Fridericia’s and was identified as the best significant cardiac mortality predictor (Hazard ratio: 4.31, 95% CI 1.73–10.74, p value = 0.002).

Conclusion

Fridericia was the best correction formula based on mathematical methods. Bazett’s formula despite its poorest performance in mathematical methods, was the best one for cardiac mortality prediction. Practically, it is suggested that physicians use QTcB for a better evaluation of cardiac mortality risk. However, in population-based studies, QTcFri might be the one to be used by researchers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02502-2.

A pharmacogenomic investigation of the cardiac safety profile of ondansetron in children and pregnant women

BACKGROUND

Ondansetron is a highly effective antiemetic for the treatment of nausea and vomiting. However, this medication has also been associated with QT prolongation. Pharmacogenomic information on therapeutic response to ondansetron exists, but no investigation has been performed on genetic factors that influence the cardiac safety of this medication.

METHODS

Three patient groups receiving ondansetron were recruited and followed prospectively (pediatric post-surgical patients n = 101; pediatric oncology patients n = 98; pregnant women n = 62). Electrocardiograms were conducted at baseline, and 5- and 30-min post-ondansetron administration, to determine the effect of ondansetron treatment on QT interval. Pharmacogenomic associations were assessed via analyses of comprehensive CYP2D6 genotyping and genome-wide association study data.

RESULTS

In the entire cohort, 62 patients (24.1%) met the criteria for prolonged QT, with 1.2% of the cohort exhibiting unsafe QT prolongation. The most significant shift from baseline occurred at five minutes post-ondansetron administration (P = 9.8 × 10^-4). CYP2D6 activity score was not associated with prolonged QT. Genome-wide analyses identified novel associations with a missense variant in TLR3 (rs3775291; P = 2.00 × 10^-7) and a variant linked to the expression of SLC36A1 (rs34124313; P = 1.97 × 10^-7).

CONCLUSIONS

This study has provided insight into the genomic basis of ondansetron-induced cardiac changes and has emphasized the importance of genes that have been implicated in serotonin-related traits. These biologically-relevant findings represent the first step towards understanding this adverse event with the overall goal to improve the safety of this commonly used antiemetic medication.

Monitoring prolongation of QT interval in patients with multidrug-resistant tuberculosis and non-tuberculous mycobacterium using mobile health device AliveCor

Multidrug resistant tuberculosis and non-tuberculous mycobacterium infections present challenges due to complex treatment regimens. Extended treatment regimes expose patients to higher risks of toxic side-effects. A high drug toxicity profile necessitates closer monitoring. One of the more challenging issues is QTc prolongation with non-injectable regimens. This study investigates the portable AliveCor device to record and measure the QTc on a 6-lead ECG. An automated QTc readout from 12-Lead ECG for each patient (n = 13) and mean QTc value calculated from each patients' respective AliveCor tracing were compared. The general trend suggests AliveCor underestimates QTc - 92% cases calculated the AliveCor QTc as lower than their corresponding 12-Lead QTc readout. The use of AliveCor could potentially be translated into current clinical practice with caution of percentage variation either side. This could facilitate the use of AliveCor as a promising and convenient screening tool before further evaluation by a 12-Lead ECG is required.

Comparison of the effect of citalopram, bupropion, sertraline, and tricyclic antidepressants on QTc: A cross-sectional study

BACKGROUND

Some data suggests that citalopram has more risk of corrected QT interval (QTc) prolongation than other selective serotonin reuptake inhibitors. Consequently the U.S. Food and Drug Administration distributed a safety warning limiting the maximum dose for citalopram. There is also a suggestion that bupropion may decrease QTc in patients on drugs that increase QTc. The goals of this cross-sectional study were to examine (1) effects on QTc of citalopram compared to sertraline, bupropion, and tricyclic antidepressants; (2) dose dependent effects of citalopram; and (3) effects of bupropion on citalopram-mediated changes in QTc.

METHODS

Records of subjects who received an EKG while taking one of the specified antidepressants were reviewed to collect demographic information, antidepressant history, and information about other confounders. Linear regression was used to examine the relationship between QTc and antidepressants.

RESULTS

487 subjects provided 798 EKG records. The sample was 95% male with an average age of 61 years. No differences were found in QTc between citalopram and other antidepressants. No dose relationship was detected between citalopram and QTc. Bupropion did not affect the relationship between citalopram and QTc (coefficient = -3.4; 95%CI = -14.2, 7.5; p = 0.54).

LIMITATIONS

Observational study designs are prone to biases from retrospective data collection. Some data subsets had small numbers of subjects.

CONCLUSIONS

No effect of citalopram on QTc was found at therapeutic doses. Neither was there evidence of a "QTc-sparing" effect of bupropion. The risk of adverse cardiovascular effects from citalopram at doses of 60 mg per day or less appears minimal.

Safety of ibogaine administration in detoxification of opioid-dependent individuals: a descriptive open-label observational study

BACKGROUND AND AIMS

Ibogaine is an indole alkaloid used in rituals of the African Bwiti tribe. It is also used in non-medical settings to treat addiction. However, ibogaine has been linked to several deaths, mainly due to cardiac events called torsades des pointes preceded by QTc prolongation as well as other safety concerns. This study aimed to evaluate the cardiac, cerebellar and psychomimetic safety of ibogaine in patients with opioid use disorder.

DESIGN

A descriptive open-label observational study.

SETTING

Department of psychiatry in a university medical center, the Netherlands.

PARTICIPANTS

Patients with opioid use disorder (n = 14) on opioid maintenance treatment with a lasting wish for abstinence, who failed to reach abstinence with standard care.

INTERVENTION AND MEASUREMENTS

After conversion to morphine-sulphate, a single dose of ibogaine-HCl 10 mg/kg was administered and patients were monitored at regular intervals for at least 24 hours assessing QTc, blood pressure and heart rate, scale for the assessment and rating of ataxia (SARA) to assess cerebellar side effects and the delirium observation scale (DOS) to assess psychomimetic effects.

FINDINGS

The maximum QTc (Fridericia) prolongation was on average 95ms (range 29-146ms). Fifty percent of subjects reached a QTc of over 500ms during the observation period. In six out 14 subjects prolongation above 450ms lasted beyond 24 hours after ingestion of ibogaine. No torsades des pointes were observed. Severe transient ataxia with inability to walk without support was seen in all patients. Withdrawal and psychomimetic effects were mostly well-tolerated and manageable (11/14 did not return to morphine within 24 hours, DOS scores remained below threshold).

CONCLUSIONS

This open-label observational study found that ibogaine treatment of patients with opioid use disorder can induce a clinically relevant but reversible QTc prolongation, bradycardia, and severe ataxia.

Electrocardiographic Changes in Children With Acute Opioid Poisoning: A Cross-Sectional Study

OBJECTIVES

Opioid poisoning in children is a common pediatric emergency in Iran. The emergence and spread of new synthetic opioids have come up with new consequences in case of toxicity. In this study, we aimed to evaluate electrocardiographic changes in children with acute opiate poisoning.

METHODS

This cross-sectional study was performed on all children with opioid poisoning admitted to the emergency ward of Vali-e-Asr Hospital, Birjand, Iran, from December 2015 to February 2017. Data (demographics, manifestations, clinical course, and outcome) were collected using a predesigned checklist. An electrocardiogram (ECG) was obtained and evaluated for arrhythmias, corrected QT interval (QTc), and other ECG indices. Data were analyzed using SPSS version 21. A value of P less than 0.05 was considered statistically significant.

RESULTS

A total of 85 children were enrolled in this study. Most of them were male (51.8%). The mean age of the patients was 3.46 ± 3.36 years. Among these children, 38.8% were poisoned with synthetic opioids (methadone). Mean QTc length was 399 ± 24 milliseconds in nonsynthetic opioid poisoning and 407 ± 66 milliseconds in methadone poisoning, and it was prolonged (>450 milliseconds) in 3.5% of cases. Other ECG changes were limited to 1 U wave formation (1.2%) that was detected in a patient with methadone poisoning.

CONCLUSIONS

Electrocardiogram changes due to acute opioid toxicity in children are not common, although in the case of methadone poisoning, long QT interval and associated arrhythmias should be anticipated. Moreover, because of life-threatening effects of opioids such as respiratory insufficiency and decreased consciousness, it is necessary to be prepared for these conditions.

American College of Rheumatology White Paper on Antimalarial Cardiac Toxicity

Hydroxychloroquine (HCQ) and chloroquine (CQ) are well-established medications used in treating systemic lupus erythematosus and rheumatoid arthritis, as well as skin conditions such as cutaneous lupus erythematosus. In rare cases, arrhythmias and conduction system abnormalities, as well as cardiomyopathy, have been reported in association with HCQ/CQ use. Recently, however, the corrected QT interval (QTc)-prolonging potential of these medications, and risk of torsade de pointes (TdP) in particular, have been highlighted in the setting of their experimental use for COVID-19 infection. This report was undertaken to summarize the current understanding of HCQ/CQ cardiac toxicity, describe QTc prolongation and TdP risks, and discuss areas of priority for future research. A working group of experts across rheumatology, cardiology, and dermatology performed a nonsystematic literature review and offered a consensus-based expert opinion. Current data clearly indicate that HCQ and CQ are invaluable medications in the management of rheumatic and dermatologic diseases, but they are associated with QTc prolongation by directly affecting cardiac repolarization. Prescribing clinicians should be cognizant of this small effect, especially in patients taking additional medications that prolong the QTc interval. Long-term use of HCQ/CQ may lead to a cardiomyopathy associated with arrhythmias and heart failure. Risk and benefit assessment should be considered prior to initiation of any medication, and both initial and ongoing risk-benefit assessments are important with regard to prescription of HCQ/CQ. While cardiac toxicity related to HCQ/CQ treatment of rheumatic diseases is rarely reported, it can be fatal. Awareness of the potential adverse cardiac effects of HCQ and CQ can increase the safe use of these medications. There is a clear need for additional research to allow better understanding of the cardiovascular risk and safety profile of these therapies used in the management of rheumatic and cutaneous diseases.

The effect of oral ondansetron on QT interval in children with acute gastroenteritis; a retrospective observational study

BACKGROUND

In mildly to moderately dehydrated patients with acute gastroenteritis (AGE), oral rehydration therapy (ORT) is the treatment of choice. Though ondansetron is a very effective antiemetics and leads to succeed ORT, there have been reports QT prolongation in patients using it. We investigated the effect of oral ondansetron on QT interval in mildly to moderately dehydrated children with AGE.

METHODS

This retrospective observational study was conducted in a single pediatric emergency department (ED) of a tertiary university hospital. We collected the medical records of patients with a primary diagnosis of AGE who received oral ondansetron and underwent an electrocardiogram between January 2017 and June 2018. A pediatric emergency physician calculated the corrected QT interval (QTc) by Bazett's method, and the calculations were reviewed by a pediatric cardiologist. QTc values before (preQTc) and after (postQTc) ondansetron administration were analyzed. ΔQTc was calculated as the change from preQTc to postQTc. We also investigated any cardiac complications from oral ondansetron.

RESULTS

Total 80 patients were included. The mean age of the patients was 53.31 ± 32.42 months, and 45% were male. The mean dose of oral ondansetron was 0.18 ± 0.04 mg/kg. The mean interval from administration of ondansetron to performance of the electrocardiogram was 65 ± 26 min. The mean preQTc was 403.3 ± 24.0 ms, and the mean postQTc was 407.2 ± 26.7 ms. Two patients had a preQTc ≥460 ms, and one patient had a postQTc ≥460 ms. ΔQTc was ≥30 ms in seven patients (8.8%). No ΔQTc was ≥60 ms. No pre- or postQTc was ≥500 ms. No patient had a fatal cardiac arrhythmia after taking ondansetron.

CONCLUSION

Oral administration of a single dose of ondansetron in children with AGE did not cause high-risk QTc prolongation or fatal arrhythmia.

Manual QT interval measurement with a smartphone-operated single-lead ECG versus 12-lead ECG: a within-patient diagnostic validation study in primary care

OBJECTIVE

To determine the accuracy of QT measurement in a smartphone-operated, single-lead ECG (1L-ECG) device (AliveCor KardiaMobile 1L).

DESIGN

Cross-sectional, within-patient diagnostic validation study.

SETTING/PARTICIPANTS

Patients underwent a 12-lead ECG (12L-ECG) for any non-acute indication in primary care, April 2017-July 2018.

INTERVENTION

Simultaneous recording of 1L-ECGs and 12L-ECGs with blinded manual QT assessment. OUTCOMES OF INTEREST: (1) Difference in QT interval in milliseconds (ms) between the devices; (2) measurement agreement between the devices (excellent agreement <20 ms and clinically acceptable agreement <40 ms absolute difference); (3) sensitivity and specificity for detection of extreme QTc (short (≤340 ms) or long (≥480 ms)), on 1L-ECGs versus 12L-ECGs as reference standard. In case of significant discrepancy between lead I/II of 12L-ECGs and 1L-ECGs, we developed a correction tool by adding the difference between QT measurements of 12L-ECG and 1L-ECGs.

RESULTS

250 ECGs of 125 patients were included. The mean QTc interval, using Bazett's formula (QTcB), was 393±25 ms (mean±SD) in 1L-ECGs and 392±27 ms in lead I of 12L-ECGs, a mean difference of 1±21 ms, which was not statistically different (paired t-test (p=0.51) and Bland Altman method (p=0.23)). In terms of agreement between 1L-ECGs and lead I, QTcB had excellent agreement in 66.9% and clinically acceptable agreement in 93.4% of observations. The sensitivity and specificity of detecting extreme QTc were 0% and 99.2%, respectively. The comparison of 1L-ECG QTcB with lead II of 12L-ECGs showed a significant difference (p=<0.01), but when using a correction factor (+9 ms) this difference was cancelled (paired t-test (p=0.43) or Bland Altman test (p=0.57)). Moreover, it led to improved rates of excellent (71.3%) and clinically acceptable (94.3%) agreement.

CONCLUSION

Smartphone-operated 1L-ECGs can be used to accurately measure the QTc interval compared with simultaneously obtained 12L-ECGs in a primary care population. This may provide an opportunity for monitoring the effects of potential QTc-prolonging medications.

Hydroxychloroquine use is not associated with QTc length in a large cohort of SLE and RA patients

Background

Hydroxychloroquine (HCQ) is a cornerstone therapy for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). However, reports of its use and subsequent fatal arrhythmias in patients with coronavirus disease 19 (COVID-19) have raised concern regarding its cardiovascular (CV) safety. Therefore, we examined the relationship between HCQ use and corrected QT (QTc) length in SLE and RA patients without clinical CV disease (CVD).

Methods

SLE patients from the Columbia University Lupus Cohort registry (n = 352) and two RA cohorts (n = 178; ESCAPE-RA and RHYTHM-RA) with electrocardiograms (ECGs) collected as part of study data were analyzed. RA cohort participants were recruited from tertiary referral centers with additional referrals from community rheumatologists, while SLE subjects originated from the Columbia University Lupus Cohort. All patients met American College of Rheumatology (ACR) classification criteria for SLE or RA and lacked known CVD. The exposure of interest was HCQ use and main outcome measure was QTc length [continuous or categorical (≥ 440 ms and ≥ 500 ms)].

Results

Of the combined SLE and RA cohorts (n = 530), 70% were HCQ users and 44% had a QTc ≥ 440 ms. The adjusted mean QTc length was comparable between HCQ users vs non-users (438 ms vs 437 ms). In multivariable logistic models, HCQ use was not a significant predictor of a QTc ≥ 440 ms for the entire cohort (OR 0.77; 95% CI 0.48–1.23; p = 0.27). Importantly, a QTc ≥ 500 ms was inversely associated with HCQ use and not associated with arrhythmias or deaths. A significant interaction was found between HCQ use and use of anti-psychotics. Ultimately, the use of HCQ combined with any QTc prolonging medication as a group was associated with a QTc length (434 ms; 95% CI 430, 439) which was comparable to that of use of HCQ alone (433 ms; 95% CI 429-437).

Conclusion

In a combined cohort of SLE and RA patients without clinical CVD, adjusted QTc length was comparable between HCQ and non-HCQ users, supporting its CV safety in patients with rheumatic diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02646-0.

Assessment of proarrhythmic ventricular electrophysiological remodeling in patients with rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is related to cardiovascular disease and results in increased mortality rates. Ischemia, autonomic nervous system dysfunction, impaired cardiac ionic currents, and genetic predisposition may be the underlying mechanisms. Proarrhythmic ventricular electrophysiological remodeling detected on the basis of Tp‑e interval, Tp-e/QT, and Tp-e/QTc ratios plays a key role in the prognosis. Our aim was to assess proarrhythmic ventricular electrophysiological remodeling in patients with RA, a well-known chronic inflammatory disorder.

MATERIALS AND METHODS

A total of 163 patients with RA and 47 patients as a control group were included in this retrospective study. Proarrhythmic ventricular electrophysiological remodeling markers were evaluated in both groups along with baseline demographic and clinical variables. Patients using medication or with chronic disorders that can affect ventricular repolarization markers were excluded.

RESULTS

The patients with RA had prolonged Tp‑e interval (66 ms [44-80]; 80 ms [78-96], p < 0.001) and increased Tp-e/QT ratio (0.18 [0.12-0.22]; 0.22 [0.20-0.24], p < 0.001) and Tp-e/QTc ratio (0.16 [0.11-0.19]; 0.20 [0.17-0.22], p < 0.001) compared to the control group.

CONCLUSION

The Tp‑e interval and Tp-e/QT ratio, which may help to clarify the pathophysiological mechanisms of ventricular arrhythmias, were increased in patients with RA.

Novel markers of ventricular repolarization are associated with mortality in patients undergoing surgical aortic valve replacement for severe aortic stenosis

INTRODUCTION

Aortic stenosis (AS) is the most common degenerative valvular heart disease that can affect left ventricular functions. Tp-e interval and Tp-e/QT ratio is a novel repolarization marker which is associated with adverse cardiovascular events in several cardiovascular diseases. In our study, our aim is to investigate the prognostic effect of Tp-e interval, Tp-e/QT and Tp-e/QTc ratios on mortality in patients who underwent successful surgical aortic valve replacement (AVR).

METHODS

A total of three hundred seventy-five patients undergoing successful surgical AVR were included in this study. Then, patients were divided into two groups according to mortality as group 1 without mortality (342 patients) and group 2 with mortality (33 patients). Tp-e interval, Tp-e/QT, and Tp-e/QTc ratios were calculated for both groups.

RESULTS

Tp-e interval (71 (63.7-77); 86 (84-88), p < .001), Tp-e/QT ratio (0.19 (0.17-0.20); 0.23 (0.22-0.23), p < .001) and Tp-e/QTc ratio (0.17 ± 0.02; 0.21 ± 0.01, p < .001) were higher in group 2 compared to group 1. In multivariate logistic regression analyses Tp-e interval (odds ratio [OR]: 1.315, 95% confidence interval [CI]: 1.203-1.437, p < .001), Tp-e/QT ratio (OR: 7.334, 95% CI: 3.274-1.643, p < .001) and Tp-e/QTc ratio (OR: 2.567, 95% CI: 4.106-1.605, p < .001) were found to be independent predictors of mortality. Additionally, a Kaplan-Meier survival analysis also revealed that long term survival was found to be significantly decreased in patients with higher Tp-e/QT ratio (Log-Rank p < .001) and Tp-e/QTc ratio (Log-Rank p < .001).

CONCLUSION

Tp-e interval, Tp-e dispersion, Tp-e/QT, and Tp-e/QTc ratios are associated with worse prognosis after surgical AVR in patients with severe AS. All of them are also independent predictors of mortality.

Mesenchymal stem cells seeded onto nanofiber scaffold for myocardial regeneration

Cardiac disease is the leading cause of mortality and disability worldwide. We investigated the role of undifferentiated adipose tissue-derived mesenchymal stem cells (ADMSC) alone and ADMSC seeded onto the electro-spun nanofibers (NF) for reconstructing damaged cardiac tissue in isoprenaline-induced myocardial infarction (MI) in rats. ADMSC were sorted by morphological appearance and by detection of cluster of differentiation (CD) surface antigens. The therapeutic potential of ADMSC for treating MI was evaluated by electrocardiogram (ECG), biochemical analysis, molecular genetic analysis and histological examination. Treatment of MI-challenged rats with ADMSC improved ECG findings, which were corroborated by significant decreases in serum lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) enzyme activities together with reduced serum troponin T (cTnT) and connexin 43 (Cx43) levels. MI model rats treated with ADMSC exhibited a significant increase in serum alpha sarcomeric actin (Actn) and GATA binding protein 4 (GATA4), and NK2 homeobox 5 (NKX2.5) gene expression was decreased following treatment with ADMSC. ADMSC also ameliorated damage to cardiac tissue. The effects of ADMSC seeded onto NF were superior to those of ADMSC alone. ADMSC may be useful for mitigation of MI.

Chemotherapy-Induced Arrhythmia - Underrecognized and Undertreated

Cancer is one of the leading causes of death worldwide. Chemotherapy-induced arrhythmia is a potential complication of treatment that confers increased morbidity and mortality. The relationship between chemotherapeutic agents and arrhythmias is poorly established. Atrial fibrillation, ventricular ectopic beats, and prolonged QTc are the most common arrhythmias suffered by cancer patients undergoing chemotherapy. The treatment of atrial fibrillation in cancer is complicated by complex drug-drug interactions and a lack of evidence guiding practice. Furthermore, the normal risk assessment scores utilized in the decision-making for anticoagulation in the normal population are not validated in the cancer population. Multiple agents are implicated in prolonging the QTc, and this can often have adverse consequences for both the patient and the treatment of their cancer. This can manifest as torsades de pointes and sudden cardiac death. It is advised that, during treatment, oncologists should have close liaison with cardio-oncologists to ensure optimum patient management.

Cardiac involvement in Wilson disease: Review of the literature and description of three cases of sudden death

Wilson disease (WD) is a rare genetic condition that results from a build-up of copper in the body. It requires life-long treatment and is mainly characterized by hepatic and neurological features. Copper accumulation has been reported to be related to the occurrence of heart disease, although little is known regarding this association. We have conducted a systematic review of the literature to document the association between WD and cardiac involvement. Thirty-two articles were retained. We also described three cases of sudden death. Cardiac manifestations in WD include cardiomyopathy (mainly left ventricular (LV) remodeling, hypertrophy, and LV diastolic dysfunction, and less frequently LV systolic dysfunction), increased levels of troponin, and/or brain natriuretic peptide, electrocardiogram (ECG) abnormalities, and rhythm or conduction abnormalities, which can be life-threatening. Dysautonomia has also been reported. The mechanism of cardiac damage in WD has not been elucidated. It may be the result of copper accumulation in the heart, and/or it could be due to a toxic effect of copper, resulting in the release of free oxygen radicals. Patients with signs and/or symptoms of cardiac involvement or who have cardiovascular risk factors should be examined by a cardiologist in addition to being assessed by their interdisciplinary treating team. Furthermore, ECG, cardiac biomarkers, echocardiography, and 24-hours or more of Holter monitoring at the diagnosis and/or during the follow-up of patients with WD need to be evaluated. Cardiac magnetic resonance imaging, although not always available, could also be a useful diagnostic tool, allowing assessment of the risk of ventricular arrhythmias and further guidance of the cardiac workup.

Dorsal vagal nucleus involvement relates to QTc-prolongation after acute medullary infarction

BACKGROUND

Infarction of the medulla has been associated with prolongation of the QTc, severe arrhythmia, and sudden cardiac death, yet the precise anatomical substrate remains uncertain.

AIMS

We sought to determine the possible anatomical structures relating to QTc-prolongation in patients with acute medullary infarction.

METHODS

We included 12 subjects with acute ischemic medullary infarction on brain MRI, who presented within 4.5 h from the last known well time, with a 90-day follow-up. For an unbiased lesion analysis, medullary infarcts were manually outlined on diffusion weighted MRI and co-registered with an anatomical atlas.

RESULTS

Nine out of 12 had QTc-prolongation. Qualitative and semi-quantitative comparisons were made between infarct location and QTc-prolongation. Among patients with QTc-prolongation, the greatest degree of congruence of the infarct location was over the dorsal vagal nucleus (DVN, 8 out of 9). There was a significant correlation between the number of sections showing infarction of the DVN and presence of QTc-prolongation (r = .582, p = .047). Among patients without QTc-prolongation, the maximum lesion overlap included the medial aspect of the gigantocelluar reticular nucleus of the reticular formation.

CONCLUSION

We found that the DVN is a key anatomical substrate related to QTc-prolongation. Further studies with more patients and high-resolution, volumetric MRI are needed to confirm our findings.

Ventricular Repolarization Parameters and Coronary Involvement in Kawasaki Disease

OBJECTIVES

To evaluate electrocardiogram markers to predict coronary involvement in patients with Kawasaki disease by assessing measures of ventricular repolarization parameters on the 12-lead electrocardiogram.

STUDY DESIGN

This cross-sectional study included 180 Spanish and Japanese patients ≤14 years of age with Kawasaki disease, with or without coronary involvement, from 2011 to 2016. We manually measured the Tp-Te/QT ratio and QTc interval (with Bazett's formula) in 12-lead electrocardiogram in the acute and recovery period and explored their potential association with coronary involvement.

RESULTS

No association was found between Tp-Te/QT ratio obtained manually in V5 and V6 leads and coronary involvement in the acute (V5:0.25 [IQR, 0.21-0.27] vs 0.25 [IQR, 0.20-0.27], P = .80; V6:0.24 [IQR, 0.21-0.27] vs 0.25 [IQR, 0.20-0.27], P = .86) or the recovery (V5: 0.23 [IQR, 0.20-0.25] vs 0.23 [IQR, 0.19-0.25], P = .68; V6: 0.23 [IQR, 0.20-0.25] vs 0.23 [IQR, 0.17-0.25], P = .50) period. By contrast, QTc in V5 and V6 was significantly lower in patients with Kawasaki disease and coronary involvement in the acute period (V5: 378 ms [IQR, 364-395 ms] vs 390 ms [IQR, 371-411 ms], P = .04; V6: 377 ms [IQR, 364-392 ms] vs 390 ms [IQR, 371-410 ms], P = .01). A QTc interval of <385 ms in lead V6 was associated with a 2.5-fold increased risk of coronary involvement (OR, 2.5; 95% CI, 1.2-5.3; P = .02).

CONCLUSIONS

Manually measured QTc interval may be a marker of coronary disease in the acute period of Kawasaki disease.

When Manual Analysis of 12-Lead ECG Holter Plays a Critical Role in Discovering Unknown Patterns of Increased Arrhythmogenic Risk: A Case Report of a Patient Treated with Tamoxifen and Subsequent Pneumonia in COVID-19

Several medicines, including cancer therapies, are known to alter the electrophysiological function of ventricular myocytes resulting in abnormal prolongation and dispersion of ventricular repolarization (quantified by multi-lead QTc measurement). This effect could be amplified by other concomitant factors (e.g., combination with other drugs affecting the QT, and/or electrolyte abnormalities, such as especially hypokalemia, hypomagnesaemia, and hypocalcemia). Usually, this condition results in higher risk of torsade de point and other life-threatening arrhythmias, related to unrecognized unpaired cardiac ventricular repolarization reserve (VRR). Being VRR a dynamic phenomenon, QT prolongation might often not be identified during the 10-s standard 12-lead ECG recording at rest, leaving the patient at increased risk for life-threatening event. We report the case of a 49-year woman, undergoing tamoxifen therapy for breast cancer, which alteration of ventricular repolarization reserve, persisting also after correction of concomitant recurrent hypokalemia, was evidenced only after manual measurements of the corrected QT (QTc) interval from selected intervals of the 12-lead ECG Holter monitoring. This otherwise missed finding was fundamental to drive the discontinuation of tamoxifen, shifting to another "safer" therapeutic option, and to avoid the use of potentially arrhythmogenic antibiotics when treating a bilateral pneumonia in recent COVID-19.

Recurrent Pregnancy Loss and Concealed Long-QT Syndrome

Background

Recurrent pregnancy loss affects 1% to 2% of couples attempting childbirth. A large fraction of all cases remains idiopathic, which warrants research into monogenic causes of this distressing disorder.

Methods and Results

We investigated a nonconsanguineous Estonian family who had experienced 5 live births, intersected by 3 early pregnancy losses, and 6 fetal deaths, 3 of which occurred during the second trimester. No fetal malformations were described at the autopsies performed in 3 of 6 cases of fetal death. Parental and fetal chromosomal abnormalities (including submicroscopic) and maternal risk factors were excluded. Material for genetic testing was available from 4 miscarried cases (gestational weeks 11, 14, 17, and 18). Exome sequencing in 3 pregnancy losses and the mother identified no rare variants explicitly shared by the miscarried conceptuses. However, the mother and 2 pregnancy losses carried a heterozygous nonsynonymous variant, resulting in p.Val173Asp (rs199472695) in the ion channel gene KCNQ1. It is expressed not only in heart, where mutations cause type 1 long‐QT syndrome, but also in other tissues, including uterus. The p.Val173Asp variant has been previously identified in a patient with type 1 long‐QT syndrome, but not reported in the Genome Aggregation Database. With heterologous expression in CHO cells, our in vitro electrophysiologic studies indicated that the mutant slowly activating voltage‐gated K+ channel (I_Ks) is dysfunctional. It showed reduced total activating and deactivating currents (P<0.01), with dramatically positive shift of voltage dependence of activation by ≈10 mV (P<0.05).

Conclusions

The current study uncovered concealed maternal type 1 long‐QT syndrome as a potential novel cause behind recurrent fetal loss.

Matrix Metalloproteinase-3 (MMP-3) Polymorphisms Are Associated with Prolonged ECG-Derived QTc Interval: A Cross-Sectional Study of the Australian Rural Population

Matrix metalloproteinases (MMPs) are enzymes that are integral in extracellular matrix (ECM) remodeling. In age or disease, ECM may become dysregulated and contribute to fibrosis, which impairs cardiac electrical conduction. Two alleles regulate matrix metalloproteinase-3 (MMP-3) activity: one with five adenosine bases (5A; associated with higher MMP-3 activity and decreased fibrosis) and another with six adenosine bases (6A; associated with lower MMP-3 activity and increased fibrosis). Here, we determined whether ECG-derived QTc and related parameters are associated with the MMP-3 5A/6A genotype in a cross-section of the Australian rural population. A retrospective cross-sectional population was obtained from the Charles Sturt University Diabetes Screening Research Initiative. Genotype and resting 12-lead ECG parameters of 295 participants were analyzed. Amongst these participants, 85 individuals carried the 5A/5A genotype, 141 individuals carried the 5A/6A genotype, and 65 individuals carried the 6A/6A genotype. Compared to 5A/5A genotype carriers, 5A/6A genotype carriers had a significantly longer QTc duration by 9.50 ms (95% CI: 3.48-15.52, p = 0.002), whilst 6A/6A genotype carriers had an even longer QTc duration by 12.19 ms (95% CI: 5.04-19.34, p = 0.001). We found an association between MMP-3 5A/6A polymorphisms and QTc, independent of adjustments for age, gender, alcohol consumption, smoking status, body mass index and blood pressure.

Electrocardiographic differences in patients with true and pseudo-resistant hypertension

Cardiovascular disease is the leading cause of mortality in hypertensives, and patients with true resistant hypertension have an increased risk for premature cardiovascular events. Electrocardiography (ECG) has an essential role in the monitoring of hypertensive heart disease; however, little is known about the importance of ECG parameters in patients with resistant hypertension. We aimed to investigate whether fragmented QRS (fQRS) and frontal plane QRS-T angle, which are novel ECG parameters indicating myocardial damage, predict true resistant hypertension in patients with uncontrolled blood pressure. Four hundred six hypertensive patients with resistant hypertension were prospectively enrolled for the study. Patients were divided into two groups as 'true resistant' or 'pseudo-resistant' hypertensives and compared regarding the ECG parameters. While 73 (18%) patients had true resistant hypertension, 333 (82%) patients had pseudo-resistant hypertension. The frequency of fQRS (47.9% vs. 20.1%, p < 0.001) and average frontal plane QRS-T angle (93.0° ± 19.7° vs. 53.8° ± 10.2°, p < 0.001) were significantly higher in patients with true resistant hypertension compared to those with pseudo-resistant hypertension. Also, fQRS in anterior leads was significantly more frequent in patients with true resistant hypertension (57.1% vs. 23.8%, p < 0.001). Moreover, ROC curve analysis demonstrated that an increased frontal plane QRS-T angle > 90.75° predicted true resistant hypertension with a sensitivity 96% and specificity 61% (AUC:0.874, p < 0.001). Furthermore, multivariate analysis demonstrated that fQRS in anterior leads (OR: 1.251, 95% CI: 1.174-1.778, p = 0.002) and frontal plane QRS-T angle (OR: 1.388, 95% CI: 1.073-1.912, p < 0.001) were independent predictors of true resistant hypertension. In conclusion, fQRS and frontal plane QRS-T angle may be useful to predict true resistant hypertension in patients with uncontrolled blood pressure.

Impact of cardiac rehabilitation on ventricular repolarization indices following coronary artery bypass grafting

Background

The aim of this study was to evaluate the effect of cardiac rehabilitation on electrocardiographic changes in patients undergoing isolated coronary artery bypass grafting.

Methods

Between January 2016 and July 2019, a total of 625 patients (485 males, 140 females; mean age: 59.6 years; range, 50.6 to 68.6 years) who underwent isolated coronary artery bypass grafting and survived were retrospectively analyzed. The patients were divided into two groups according to the participation in the cardiac rehabilitation program as follows: the Rehab(+) group (n=363) and the Rehab(-) group (n=262). Electrocardiographic parameters of both groups were compared.

Results

There was a significant decrease in the electrocardiographic findings of heart rate (p<0.001), QTc (p<0.001), Tpe duration (p<0.001), Tpe/QT ratio (p<0.001), and Tpe/QTc ratio (p<0.001) in the Rehab(+) group before and after surgery. There was a significant decrease in the Rehab(+) group, compared to the Rehab(-) group, in terms of parameters of QT interval (p=0.001), QTc (p=0.017), Tpe duration (p<0.001), Tpe/QT ratio (p<0.001), and Tpe/QTc ratio (p<0.001).

Conclusion

Cardiac rehabilitation program after coronary artery bypass grafting decreases ventricular repolarization indices of electrocardiography. Based on these changes, postoperative cardiac rehabilitation program may reduce the risk of ventricular arrhythmia and sudden cardiac death during follow-up.

Dose response to nadolol in congenital long QT syndrome

BACKGROUND

Beta-blocker therapy is the cornerstone of treatment for patients with long QT syndrome (LQTS). Few details on the dose to be used are available. As the response is variable between patients, we systematically evaluated the effect of treatment by performing an exercise test.

OBJECTIVE

The purpose of this study was to explore dose response to nadolol on exercise test in LQTS patients in order to propose a more personalized therapeutic approach.

METHODS

LQTS patients followed at the Reference Centre for Hereditary Arrhythmic Diseases of Nantes with at least 1 exercise test under nadolol were included retrospectively between 1993 and 2017. All patients underwent gradual cycle exercise tests. Doses adjusted to weight and response to treatment were recorded and evaluated by the percentage of age-predicted maximum heart rate reached on exercise test.

RESULTS

Ninety-five patients were included in the study, and 337 stress tests under nadolol were analyzed. No correlation existed between dose and percentage of age-predicted maximum heart rate on exercise tests. Twenty-one patients were overresponders, mostly LQTS1, and 20 were underresponders, mainly LQTS2 (P = .0229). Forty-two patients had at least 3 stress tests under nadolol. We found a negative correlation between dose change and percentage of age-predicted maximum heart rate change (P <.0001). We then proposed a table to adapt dose according to exercise test response.

CONCLUSION

Our study demonstrated a major variability of dose response to nadolol in patients with LQTS, thus underlining the need for a tailored dosage for each patient. Intraindividual analysis showed a relatively constant dose-response relationship, allowing guided dose adaptation after the first exercise test.

Perceived Stress in a Gender Perspective: A Survey in a Population of Unemployed Subjects of Southern Italy

Stressful life events, are differently handled by women and men. This study evaluates gender differences in perceived stress and health status among a sample of subjects going through a transition period from unemployment to work. This cross-sectional study enrolled 395 participants, 245 men (62%) and 150 (38%) women, between 19 and 67 years, that were going to be hired for a 6-month contract. Before being employed, all participants underwent a mandatory protocol consisting in a general medical check. Stress assessment was performed by using the Perceived Stress Scale (PSS). Most of the participants (68%) showed normal to low perceived stress level. But dividing the sample by gender, out of the remaining 32% with medium to high stress level, 11% male subjects and 22.7% females reported high perceived stress values. We found mean PSS values that are overlapping with those in the general population of developed countries. This study does not suggest an association between perceived stress and health or social parameters. However, our results highlight that the female gender is associated with higher stress level, pointing out the relevance of specific and designed interventions in the context of health promotion programs, especially in order to mitigate stress in more susceptible subjects.

Coronavirus disease 2019 (COVID-19) and QTc prolongation

INTRODUCTION

The cause-and-effect relationship of QTc prolongation in Coronavirus disease 2019 (COVID-19) patients has not been studied well.

OBJECTIVE

We attempt to better understand the relationship of QTc prolongation in COVID-19 patients in this study.

METHODS

This is a retrospective, hospital-based, observational study. All patients with normal baseline QTc interval who were hospitalized with the diagnosis of COVID-19 infection at two hospitals in Ohio, USA were included in this study.

RESULTS

Sixty-nine patients had QTc prolongation, and 210 patients continued to have normal QTc during hospitalization. The baseline QTc intervals were comparable in the two groups. Patients with QTc prolongation were older (mean age 67 vs. 60, P 0.003), more likely to have underlying cardiovascular disease (48% versus 26%, P 0.001), ischemic heart disease (29% versus 17%, P 0.026), congestive heart failure with preserved ejection fraction (16% versus 8%, P 0.042), chronic kidney disease (23% versus 10%, P 0.005), and end-stage renal disease (12% versus 1%, P < 0.001). Patients with QTc prolongation were more likely to have received hydroxychloroquine (75% versus 59%, P 0.018), azithromycin (18% vs. 14%, P 0.034), a combination of hydroxychloroquine and azithromycin (29% vs 7%, P < 0.001), more than 1 QT prolonging agents (59% vs. 32%, P < 0.001). Patients who were on angiotensin-converting enzyme inhibitors (ACEi) were less likely to develop QTc prolongation (11% versus 26%, P 0.014). QTc prolongation was not associated with increased ventricular arrhythmias or mortality.

CONCLUSION

Older age, ESRD, underlying cardiovascular disease, potential virus mediated cardiac injury, and drugs like hydroxychloroquine/azithromycin, contribute to QTc prolongation in COVID-19 patients. The role of ACEi in preventing QTc prolongation in COVID-19 patients needs to be studied further.

Electrocardiographic Evaluation of the Ventricular Arrhythmia Risk in Patients Diagnosed With Schizophrenia

OBJECTIVE

The purpose of this study was to examine electrocardiographic ventricular arrhythmia predictors in patients with schizophrenia by comparing with healthy controls.

METHODS

The study included 100 patients with schizophrenia and 100 healthy controls. Electrocardiography (ECG) was performed on all participants in resting position. T-wave peak to end (Tp-e), QT ranges, P-wave dispersion (Pd), and R-R range were measured. Then, the Schizophrenia Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS) were applied to the schizophrenia group.

RESULTS

The PANSS positive symptom subscale was calculated as 10.41 (SD = 2.27), the negative symptom subscale was calculated as 14.44 (SD = 5.42), and the overall functionality level was calculated as 27.04 (SD = 5.43). The mean CDSS score was determined to be 3.74 (SD = 2.15). No differences were detected in the heart rate measurements of the patient and control groups in ECG results (P = .427). The minimum QT interval and minimum Tp-e wave times were found to be low in the patient group (P < .001 for both intervals). Corrected QTc dispersion, Pd, Tp-e dispersion, and QT dispersion were found to be higher in the patient group than in healthy controls (P < .001 for all intervals).

DISCUSSION

Based on our results, it is possible to speculate that patients with schizophrenia are at a risk of developing cardiac arrhythmia and cardiac dysfunction if they do not receive treatment. For this reason, clinicians should pay attention to cardiac transmission problems when organizing the treatment of patients. Further studies should be conducted to determine cardiac problems in patients with schizophrenia.

T-wave morphology descriptors in patients with bulimia nervosa

PURPOSE

Bulimia nervosa (BN) is associated with increased risk of cardiovascular disease and arrhythmias. Some reports found abnormal electrocardiographic markers of arrhythmias in BN, while others did not. This study investigated novel parameters of T-wave morphology that were reported to be associated with adverse cardiovascular outcomes in other patient groups, among patients with BN under medical care.

METHOD

Thirty-five BN patients and 76 healthy controls were included. Total cosine R to T (TCRT) and T-wave Morphology Dispersion (TMD) parameters were computed according to accepted standards for an average beat and a random beat. Patients were followed for 11.1 ± 0.1 years for the emergence of arrhythmias or events of sudden death.

RESULTS

Twenty-five (71.4%) BN patients were hospitalized when enrolled, for a mean duration of 1.1 ± 0.2 months. The rest were ambulatory patients. The BN group had lower blood pressure, more smokers, and used antidepressants, neuroleptic drugs and benzodiazepines more than controls did. Other demographic parameters were comparable between groups. TCRT and TMD parameters were statistically similar and within the normal ranges reported by other research groups. None of the BN patients had prolonged QTc interval or electrolyte abnormalities on inclusion. During the follow-up period, no clinical symptoms suggestive of arrhythmias were reported, and no cardiovascular-related hospitalizations or deaths occurred in either group.

CONCLUSION

Medically treated BN patients have normal T-wave morphology parameters and hence, low risk for repolarization-associated malignant ventricular arrhythmias. The prognostic importance of these novel repolarization parameters remains to be explored among untreated patients, those who ingest emetic substances and patients with electrolyte imbalance.

LEVEL OF EVIDENCE

Level III.

Teasing out Artificial Intelligence in Medicine: An Ethical Critique of Artificial Intelligence and Machine Learning in Medicine

The rapid adoption and implementation of artificial intelligence in medicine creates an ontologically distinct situation from prior care models. There are both potential advantages and disadvantages with such technology in advancing the interests of patients, with resultant ontological and epistemic concerns for physicians and patients relating to the instatiation of AI as a dependent, semi- or fully-autonomous agent in the encounter. The concept of libertarian paternalism potentially exercised by AI (and those who control it) has created challenges to conventional assessments of patient and physician autonomy. The unclear legal relationship between AI and its users cannot be settled presently, an progress in AI and its implementation in patient care will necessitate an iterative discourse to preserve humanitarian concerns in future models of care. This paper proposes that physicians should neither uncritically accept nor unreasonably resist developments in AI but must actively engage and contribute to the discourse, since AI will affect their roles and the nature of their work. One's moral imaginative capacity must be engaged in the questions of beneficence, autonomy, and justice of AI and whether its integration in healthcare has the potential to augment or interfere with the ends of medical practice.

An explainable algorithm for detecting drug-induced QT-prolongation at risk of torsades de pointes (TdP) regardless of heart rate and T-wave morphology

Torsade de points (TdP), a life-threatening arrhythmia that can increase the risk of sudden cardiac death, is associated with drug-induced QT-interval prolongation on the electrocardiogram (ECG). While many modern ECG machines provide automated measurements of the QT-interval, these automated QT values are usually correct only for a noise-free normal sinus rhythm, in which the T-wave morphology is well defined. As QT-prolonging drugs often affect the morphology of the T-wave, automated QT measurements taken under these circumstances are easily invalidated. An additional challenge is that the QT-value at risk of TdP varies with heart rate, with the slower the heart rate, the greater the risk of TdP. This paper presents an explainable algorithm that uses an understanding of human visual perception and expert ECG interpretation to automate the detection of QT-prolongation at risk of TdP regardless of heart rate and T-wave morphology. It was tested on a large number of ECGs (n=5050) with variable QT-intervals at varying heart rates, acquired from a clinical trial that assessed the effect of four known QT-prolonging drugs versus placebo on healthy subjects. The algorithm yielded a balanced accuracy of 0.97, sensitivity of 0.94, specificity of 0.99, F1-score of 0.88, ROC (AUC) of 0.98, precision-recall (AUC) of 0.88, and Matthews correlation coefficient (MCC) of 0.88. The results indicate that a prolonged ventricular repolarisation area can be a significant risk predictor of TdP, and detection of this is potentially easier and more reliable to automate than measuring the QT-interval distance directly. The proposed algorithm can be visualised using pseudo-colour on the ECG trace, thus intuitively 'explaining' how its decision was made, which results of a focus group show may help people to self-monitor QT-prolongation, as well as ensuring clinicians can validate its results.

Association Between ECG Abnormalities and Fatal Cardiovascular Disease Among Patients With and Without Severe Mental Illness

Background

ECG abnormalities are associated with adverse outcomes in the general population, but their prognostic significance in severe mental illness (SMI) remains unexplored. We investigated associations between no, minor, and major ECG abnormalities and fatal cardiovascular disease (CVD) among patients with SMI compared with controls without mental illness.

Methods and Results

We cross‐linked data from Danish nationwide registries and included primary care patients with digital ECGs from 2001 to 2015. Patients had SMI if they were diagnosed with schizophrenia, bipolar disorder, or severe depression before ECG recording. Controls were required to be without any prior mental illness or psychotropic medication use. Fatal CVD was assessed using hazard ratios (HRs) with 95% CIs and standardized 10‐year absolute risks. Of 346 552 patients, 10 028 had SMI (3%; median age, 54 years; male, 45%), and 336 524 were controls (97%; median age, 56 years; male, 48%). We observed an interaction between SMI and ECG abnormalities on fatal CVD (P<0.001). Severe mental illness was associated with fatal CVD across no (HR, 2.17; 95% CI, 1.95–2.43), minor (HR, 1.90; 95% CI, 1.49–2.42), and major (HR, 1.40; 95% CI, 1.26–1.55) ECG abnormalities compared with controls. Across age‐ and sex‐specific subgroups, SMI patients with ECG abnormalities but no CVD at baseline had highest standardized 10‐year absolute risks of fatal CVD.

Conclusions

ECG abnormalities conferred a poorer prognosis among patients with SMI compared with controls without mental illness. SMI patients with ECG abnormalities but no CVD represent a high‐risk population that may benefit from greater surveillance and risk management.

The Changes of T-Wave Amplitude and QT Interval Between the Supine and Orthostatic Electrocardiogram in Children With Dilated Cardiomyopathy

Objectives: Electrocardiogram (ECG) can be affected by autonomic nerves with body position changes. The study aims to explore the ECG changes of children with dilated cardiomyopathy (DCM) when their posture changes. Materials and methods: Sixty-four children diagnosed with DCM were recruited as research group and 55 healthy children as control group. T-wave amplitude and QT interval in ECG were recorded, and their differences between supine and orthostatic ECG were compared in both groups. Subsequently, the children with DCM were followed up and the differences before and after treatment compared. Results: ① Comparisons in differences: Differences of T-wave amplitude in lead II and III, aVF, and V₅ and differences of QT interval in lead II, aVL, aVF, and V₅ were lower in the research group than in the control group. ② Logistic regression analysis and diagnostic test evaluation: The differences of T-wave amplitude in lead III and QT interval in lead aVL may have predictive value for DCM diagnosis. When their values were 0.00 mV and 30 ms, respectively, the sensitivity and specificity of the combined index were 37.5 and 83.6%. ③ Follow-up: In the response group, the T-wave amplitude difference in lead aVR increased and the difference of QT interval in lead V₆ decreased after treatment. In the non-response group, there was no difference before and after treatment. When the combined index of the differences of T-wave amplitude difference in lead aVR and QT interval difference in lead V₆, respectively, were -0.05 mV and 5 ms, the sensitivity and specificity of estimating the prognosis of DCM were 44.4 and 83.3%. Conclusions: The differences of T-wave amplitude and QT interval may have a certain value to estimate DCM diagnosis and prognosis.

Serum Bilirubin Level Predicts Frontal QRS-T Angle Change in Patients with Acute Coronary Syndrome

Introduction: The predictive role of serum bilirubin levels on the alteration of total ischemic burden expressed via frontal QRS-T angle change has never been studied in patients with acute coronary syndrome (ACS). In this study, we aimed to investigate the relationship between serum bilirubin levels and frontal QRS-T angle change after percutaneous coronary intervention (PCI) in ACS patients.

Methods: Frontal QRS-T angle change was accepted as positive or negative according to whether the value of the baseline frontal QRS-T angle minus the post PCI frontal QRS-T angle is positive or negative. A total of 314 consecutive patients with ACS who underwent PCI were divided into two groups based on their negative frontal QRS-T angle change (n = 152 patients) and positive frontal QRS-T angle change (n = 162 patients).

Results: Multivariate logistic regression analysis showed that the C-reactive protein (CRP) to albumin ratio (CAR) (Odds ratio [OR]: 0.519, 95% CI: 0.373–0.724, p <0.001), total bilirubin (OR: 3.687, 95% CI: 1.151–8.095, p = 0.03), and low-density lipoprotein (LDL) (OR: 0.985, 95% CI: 0.970–1.000, p = 0.04) were independent predictors of positive QRS-T angle change. In receiver operating characteristics curve analysis, a cut-off value of 0.59 total bilirubin had a 69% sensitivity and a 65% specificity (area under curve: 0.739, p <0.001) for the prediction of positive QRS-T angle change.

Conclusion: In ACS patients, serum total bilirubin has been found to be a useful decision-making tool to predict positive frontal QRS-T angle change as a sign of reduced total ischemic burden, to assess early invasive strategy independently from other study parameters.

Cardiac Complications of Propionic and Other Inherited Organic Acidemias

Clinical observations and experimental studies have determined that systemic acid-base disturbances can profoundly affect the heart. A wealth of information is available on the effects of altered pH on cardiac function but, by comparison, much less is known about the actions of the organic anions that accumulate alongside H⁺ ions in acidosis. In the blood and other body fluids, these organic chemical species can collectively reach concentrations of several millimolar in severe metabolic acidoses, as in the case of inherited organic acidemias, and exert powerful biological actions on the heart that are not intuitive to predict. Indeed, cardiac pathologies, such as cardiomyopathy and arrhythmia, are frequently reported in organic acidemia patients, but the underlying pathophysiological mechanisms are not well established. Research efforts in the area of organic anion physiology have increased dramatically in recent years, particularly for propionate, which accumulates in propionic acidemia, one of the commonest organic acidemias characterized by a high incidence of cardiac disease. This Review provides a comprehensive historical overview of all known organic acidemias that feature cardiac complications and a state-of-the-art overview of the cardiac sequelae observed in propionic acidemia. The article identifies the most promising candidates for molecular mechanisms that become aberrantly engaged by propionate anions (and its metabolites), and discusses how these may result in cardiac derangements in propionic acidemia. Key clinical and experimental findings are considered in the context of potential therapies in the near future.

Frontal plane QRS-T angle in the monitoring of intravenous amiodarone infusion for pharmacological cardioversion of acute atrial fibrillation

WHAT IS KNOWN AND OBJECTIVE

Intravenous amiodarone infusion is effective and widely used treatment for pharmacological cardioversion of recent-onset atrial fibrillation (Af). Although amiodarone may trigger various alterations in cardiac electrophysiology and electrocardiography (ECG), the impact of amiodarone treatment on frontal plane QRS-T angle remains unclear. Frontal plane QRS-T angle is the angle between the depolarization and repolarization axes and indicates instability in the cardiac cellular electrophysiology. Therefore, the present study aimed to investigate whether intravenous amiodarone infusion has effect on frontal plane QRS-T angle in patients with acute Af.

METHODS

A total of 179 patients with acute-onset Af who underwent pharmacological cardioversion with intravenous amiodarone infusion were included into the study. Patients with successful and failed pharmacological cardioversion were compared regarding pre- and post-treatment frontal plane QRS-T angle.

RESULTS AND DISCUSSION

At the end of the amiodarone infusion, sinus rhythm was restored in 112 (62.6%) patients, whereas Af was persisted in 67 (37.4%) patients. Despite the similar frontal plane QRS-T angle at baseline (59.6°±21.73°vs.60.4°±25.67°, p = 0.822), patients with failed pharmacological cardioversion had significantly higher post-treatment frontal plane QRS-T angle compared to patients with successful pharmacological cardioversion (68.8°±21.71°vs.58.6°±25.15° p < 0.001). Furthermore, multivariate analysis demonstrated that post-treatment increased frontal plane QRS-T angle was found to be an independent predictor of failure of pharmacological cardioversion with amiodarone infusion (OR:1.233, 95% CI:1.147-1.919, p = 0.024).

WHAT IS NEW AND CONCLUSION

Amiodarone may significantly affect the frontal plane QRS-T angle. As a parameter that can be easily calculated from automated ECG recordings, frontal plane QRS-T angle may be useful in the monitoring of intravenous amiodarone treatment.

Importance of electrocardiographic markers in predicting cardiac events in children

ECG is a common diagnostic tool in medical practice. Sudden cardiac death (SCD) is a rare but devastating event. The most common cause of SCD in the young is a primary arrhythmic event, which is often produced by malignant ventricular arrhythmia. Several electrocardiographic markers for ventricular repolarization and depolarization have been proposed to predict this arrhythmic risk and SCD in children. Although many of these parameters can easily be used in clinical practice, some of them need specific techniques for interpretation. In this review, we summarized the current knowledge regarding the clinical importance and the ability of these ECG parameters to predict adverse cardiac events in the pediatric population.

Absence of relevant QT interval prolongation in not critically ill COVID-19 patients

SARS-CoV-2 is a rapidly evolving pandemic causing great morbimortality. Medical therapy with hydroxicloroquine, azitromycin and protease inhibitors is being empirically used, with reported data of QTc interval prolongation. Our aim is to assess QT interval behaviour in a not critically ill and not monitored cohort of patients. We evaluated admitted and ambulatory patients with COVID-19 patients with 12 lead electrocardiogram at 48 h after treatment initiation. Other clinical and analytical variables were collected. Statistical analysis was performed to assess the magnitude of the QT interval prolongation under treatment and to identify clinical, analytical and electrocardiographic risk markers of QT prolongation independent predictors. We included 219 patients (mean age of 63.6 ± 17.4 years, 48.9% were women and 16.4% were outpatients. The median baseline QTc was 416 ms (IQR 404-433), and after treatment QTc was prolonged to 423 ms (405-438) (P < 0.001), with an average increase of 1.8%. Most of the patients presented a normal QTc under treatment, with only 31 cases (14.1%) showing a QTc interval > 460 ms, and just one case with QTc > 500 ms. Advanced age, longer QTc basal at the basal ECG and lower potassium levels were independent predictors of QTc interval prolongation. Ambulatory and not critically ill patients with COVID-19 treated with hydroxychloroquine, azithromycin and/or antiretrovirals develop a significant, but not relevant, QT interval prolongation.

Long-term azithromycin use is not associated with QT prolongation in children with cystic fibrosis

Chronic Azithromycin (AZM) is a common treatment for lung infection. Among adults at risk of cardiac events, AZM use has been associated with cardiovascular harm. We assessed cardiovascular safety of AZM among children with CF, as a secondary analysis of a placebo-controlled, clinical trial, in which study drug was taken thrice-weekly for a planned 18 months. Safety assessments using electrocardiogram (ECG) occurred at study enrollment, and then after 3 weeks and 18 months of participation. Among 221 study participants with a median of 18 months follow-up, increased corrected QT interval (QTc) of ≥30 msec was rare, at 3.4 occurrences per 100 person-years; and incidence of QTc prolongation was no higher in the AZM arm than the placebo arm (1.8 versus 5.4 per 100 person-years). No persons experienced QTc intervals above 500 msec. Long-term chronic AZM use was not associated with increased QT prolongation.

Effect of hydroxychloroquine, azithromycin and lopinavir/ritonavir on the QT corrected interval in patients with COVID-19

Background

Administration of Hydroxychloroquine and Azithromycin in patients with coronavirus disease 2019 (COVID-19) prolongs QTc corrected interval (QTc). The effect and safety of Lopinavir/Ritonavir in combination with these therapies have seldom been studied.

Objectives

Our aim was to evaluate changes in QTc in patients receiving double (Hydroxychloroquine + Azithromycin) and triple therapy (Hydroxychloroquine + Azithromycin + Lopinavir/Ritonavir) to treat COVID-19. Secondary outcome was the incidence of in-hospital all-cause mortality.

Methods

Patients under treatment with double (DT) and triple therapy (TT) for COVID-19 were consecutively included in this prospective observational study. Serial in-hospital electrocardiograms were performed to measure QTc at baseline and during therapy.

Results

168 patients (±66.2 years old) were included: 32.1% received DT and 67.9% received TT. The mean baseline QTc was 410.33 ms. Patients under DT and TT prolonged QTc interval respect baseline values (p < 0.001), without significant differences between both therapy groups (p = 0.748). Overall, 33 patients (19.6%) had a peak QTc and/or an increase QTc 60 ms from baseline, with a higher prevalence among those with hypokalemia (p = 0.003). All-cause mortality was similar between both strategy groups (p = 0.093) and high risk QTc prolongation was no related to clinical events in this series.

Conclusions

DT and TT prolong the QTc in patients with COVID-19. Addition of Lopinavir/Ritonavir on top of Hydroxychloroquine and Azithromycin did not increase QTc compared to DT.

J-curve relationship between corrected QT interval and mortality in acute heart failure patients

BACKGROUND/AIMS

This study investigated the prognostic power of corrected QT (QTc) interval in patients with acute heart failure (AHF) according to sex.

METHODS

We analyzed multicenter Korean Acute Heart Failure registry with patients with AHF admitted from 2011 to 2014. Among them, we analyzed 4,990 patients who were followed up to 5 years. Regarding QTc interval based on 12 lead electrocardiogram, patients were classified into quartiles according to sex.

RESULTS

During follow-up with median 43.7 months, 2,243 (44.9%) patients died. The relationship between corrected QT interval and all-cause mortality followed a J-curve relationship. In Kaplan-Meier analysis, both sex had lowest mortality in the second QTc quartile. There were significant prognostic differences between the second and the fourth quartiles in male (log-rank p = 0.002), but not in female (log-rank p = 0.338). After adjusting covariates, the third (hazard ratio [HR], 1.185; 95% confidence interval [CI], 1.001 to 1.404; p = 0.049) and the fourth (HR, 1.404; 95% CI, 1.091 to 1.535; p = 0.003) quartiles demonstrated increased risk of mortality compared to the second quartile in male. In female, however, there was no significant difference across quartiles. QTc interval was associated with 5-year all-cause mortality in J-shape with nadir of 440 to 450 ms in male and 470 to 480 ms in female.

CONCLUSION

QTc interval was an independent predictor of overall death in male, but its significance decreased in female. The relationship between QTc interval and all-cause mortality was J-shaped in both sex.

Evaluation of early electrocardiographic changes after successful percutaneous stent implantation to isolated coarctation of aorta

BACKGROUND

Coarctation of aorta (CoA) is a congenital obstructive lesion characterized by narrowing of the aorta in which concludes as increase in afterload. Percutaneous stent implantation to CoA is a treatment of choice in older children and adults. Pathology related to CoA mainly caused by increased afterload and left ventricular hypertrophy. Electrocardiographic (ECG) findings are also related to left ventricular hypertrophy (LVH). Evidence shows that, in variety of diseases, the correction of the pathology might normalize ECG findings and ventricular dysfunction related to increase in afterload. Therefore the aim of this study was to compare the pre- and postprocedural ECG findings of the patients who underwent percutaneous intervention for isolated CoA.

METHODS

After exclusion criterion was applied, 30 patients were included into study, retrospectively. ECG records before the procedure and 3 months after the procedure of the patients were evaluated. The parameters related to LVH, ventricular and atrial conduction were evaluated and compared between pre- and post-procedural ECG records.

RESULTS

The findings showed that parameters of atrial conduction including P wave maximum duration (p < 0.001) and p wave dispersion (p < 0.001) were significantly decreased after stent implantation. Additionally, ventricular repolarization parameters including QT duration (p = 0.039), Tpe interval (p < 0.001), Tpe / QT (p = 0.038) and Tpe / QTc (p = 0.003) were significantly decreased after stent implantation. Sokolow-Lyon criteria (p < 0.003) and voltage in selected leads were significantly decreased after intervention.

CONCLUSION

Percutaneous intervention to CoA might regress LVH parameters in ECG and improve atrial and ventricular repolarization in ECG, which might lead to decreased event of atrial and ventricular arrhythmias in patients with isolated CoA.

Managing drug-induced QT prolongation in clinical practice

Many drug therapies are associated with prolongation of the QT interval. This may increase the risk of Torsades de Pointes (TdP), a potentially life-threatening cardiac arrhythmia. As the QT interval varies with a change in heart rate, various formulae can adjust for this, producing a ‘corrected QT’ (QTc) value. Normal QTc intervals are typically <450 ms for men and <460 ms for women. For every 10 ms increase, there is a ~5% increase in the risk of arrhythmic events. When prescribing drugs associated with QT prolongation, three key factors should be considered: patient-related risk factors (eg, female sex, age >65 years, uncorrected electrolyte disturbances); the potential risk and degree of QT prolongation associated with the proposed drug; and co-prescribed medicines that could increase the risk of QT prolongation. To support clinicians, who are likely to prescribe such medicines in their daily practice, we developed a simple algorithm to help guide clinical management in patients who are at risk of QT prolongation/TdP, those exposed to QT-prolonging medication or have QT prolongation.

QT correction using Bazett's formula remains preferable in long QT syndrome type 1 and 2

Background

The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients.

We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes.

Methods

Automated measurements from routine 12‐lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup (n = 44). Concordance analysis was performed for QTc ≥ 480 ms (diagnosis) and ≥500 ms (prognosis).

Results

The median age was 32 years (range 0.1–78), 123 (62%) were female and 52 (26%) were children ≤16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629–0.469) for diagnosis and prognosis in individual patients.

Conclusion

Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.

No Association Between T-peak to T-end Interval on the Resting ECG and Long-Term Incidence of Ventricular Arrhythmias Triggering ICD Interventions

Background and Objectives

Potential of using the T-peak to T-end (TpTe) interval as an electrocardiographic parameter reflecting the transmural dispersion of ventricular repolarization (TDR) to identify patients (pts.) with higher risk of malignant ventricular arrhythmias (MVA) for better selection of candidates for implantable cardioverter-defibrillator (ICD) in primary prevention (PP) of sudden cardiac death (SCD) remains controversial. The primary objective of this study was to investigate the relationship between the TpTe interval in patient’s preimplantation resting 12-lead electrocardiogram (ECG) and the incidence of MVA resulting in appropriate ICD intervention (AI). The secondary objective was to assess its relationship to overall mortality.

Methods

A total of 243 consecutive pts. with severe left ventricular (LV) systolic dysfunction after myocardial infarction (MI) with a single-chamber ICD for PP of SCD from one implantation center were included. Excluded were all pts. with any other disease that could interfere with the indication of ICD implantation. Primarily investigated intervals were measured manually in accordance with accepted methodology. Data on ICD interventions were acquired from device interrogation during regular outpatient visits. Survival data were collected from the databases of health insurance and regulatory authorities.

Results

We did not find a significant relationship between the duration of the TpTe interval and the incidence of MVA (71.5 ms in pts. with MVA vs. 70 ms in pts. without MVA; p = 0.408). Similar results were obtained for the corrected TpTe interval (TpTec) and the ratio of TpTe to QT interval (76.3 ms vs. 76.5 ms; p = 0.539 and 0.178 vs. 0.181; p = 0.547, respectively). There was also no significant difference between the duration of TpTe, TpTec and TpTe/QT ratio in pts. groups by overall mortality (71.5 ms in the deceased group vs. 70 ms in the survivors group; HR 1.01; 95% CI, 0.99–1.02; p = 0.715, 76.3 ms vs. 76.5 ms; HR 1.01; 95% CI, 0.99–1.02; p = 0.208 and 0.178 vs. 0.186; p = 0.116, respectively).

Conclusion

This study suggests no significant association of overall or MVA-free survival with ECG parameters reflecting TDR (TpTe, TpTec) in patients with systolic dysfunction after MI and ICD implanted for primary prevention.

Andersen-Tawil Syndrome: A Comprehensive Review

Andersen-Tawil syndrome (ATS) is a very rare orphan genetic multisystem channelopathy without structural heart disease (with rare exceptions). ATS type 1 is inherited in an autosomal dominant fashion and is caused by mutations in the KCNJ2 gene, which encodes the α subunit of the K+ channel protein Kir2.1 (in ≈ 50-60% of cases). ATS type 2 is in turn linked to a rare mutation in the KCNJ5-GIRK4 gene that encodes the G protein-sensitive-activated inwardly rectifying K+ channel Kir3.4 (15%), which carries the acetylcholine-induced potassium current. About 30% of cases are de novo/sporadic, suggesting that additional as-yet unidentified genes also cause the disorder. A triad of periodic muscle paralysis, repolarization changes in the electrocardiogram, and structural body changes characterize ATS. The typical muscular change is episodic flaccid muscle weakness. Prolongation of the QU/QUc intervals and normal or minimally prolonged QT/QTc intervals with a tendency to ventricular arrhythmias are typical repolarization changes. Bidirectional ventricular tachycardia is the hallmark ventricular arrhythmia, but also premature ventricular contractions, and rarely, polymorphic ventricular tachycardia of torsade de pointes type may be present. Patients with ATS have characteristic physical developmental dysmorphisms that affect the face, skull, limbs, thorax, and stature. Mild learning difficulties and a distinct neurocognitive phenotype (deficits in executive function and abstract reasoning) have been described. About 60% of affected individuals have all features of the major triad. The purpose of this review is to present historical aspects, nomenclature (observations/criticisms), epidemiology, genetics, electrocardiography, arrhythmias, electrophysiological mechanisms, diagnostic criteria/clues of periodic paralysis, prognosis, and management of ATS.

Effect of lung resection on electrocardiography

BACKGROUND

Post-operative changes in electrocardiography (ECG) after lung surgery have been investigated in prior researches. We have limited data about benign physiologic changes in ECG after lung surgery, specifically after lung resection. The aim of our study was to investigate relationship in between lung resection with minimally invasive robotic or video-assisted thoracoscopic surgery (VATS) and its effect on ECG after lung resection.

METHODS

After exclusion criteria had been applied, a total of 133 patients were enrolled in the present study. Operational information such as amount of resected segment and side of resection was recorded. Lung resections were divided into two groups. One group included surgeries with lung resections <3 segments and other group included surgeries with segmentectomy ≥3 segments. Pre-operative and postoperative (in between 2nd and 3rd months) ECG data of the patients were compared. The location of resected segments as left-sided and right-sided resections were noted to compare the ECG changes for sub-analysis.

RESULTS

Among 133 patients, 101 patients were male (75.9%). There was no significant difference between parameters including ventricular rate, P wave, QRS wave and T wave axis in degrees, PR, QRS, QT and QTc durations, Tpe interval, ratio of Tpe interval to QT and QTc interval and fQRSTa. There was significant difference between before and after resection in terms of degree of QRS axis (before resection =37.3 ± 52.7 vs. after resection = 26.2 ± 55.7, P = .026). Sub-analysis regarding to amount of resected segments, there was no significant difference identified in terms of QRS axis in degrees between before and after resection for patients who underwent lung resection <3 segments (p = .885). However, there was significant difference in QRS axis in degrees for patients who underwent lung resection ≥3 segments (before resection = 47.3 ± 57.5 vs. after resection = 23.7 ± 66.2, P = .010). There was significant rightward axial change after left-sided lung resections (before resection =32.0 ± 52.4 vs. after resection = 49.4 ± 47.1, P = .005) and leftward axial change after right-sided lung resection (before resection = 41.7 ± 53.0 vs. after resection = 7.1 ± 55.2, P < .001).

CONCLUSION

Understanding and recognition of possible ECG changes are crucial during post-operative follow-up of the patients who underwent lung resection. These changes might be benign changes, which are related to anatomical and geometrical changes within thoracic cavity.