QT interval variations and mortality risk: is there any relationship?

Do Different TSH Suppression Levels Effect Heart Rate Variability and QT Dispersions in Patients with Differentiated Thyroid Cancer?

OBJECTIVE

The aim of this study was to investigate changes in heart rate variability (HRV) and QT dispersion (QTd) in patients with differentiated thyroid cancer at different TSH suppression levels.

METHODS

The study included 125 DTC patients, who had been on TSH suppression treatment (TSHST) for at least 1 year. The patients were categorized into three groups: patients with TSH < 0.1 mIU/L (n:30), those with TSH 0.1 to 0.5 mIU/L (n:56), and those with TSH 0.5 to 2 mIU/L (n:39). The first two groups were classified as suppression groups, and the last as replacement (control) group. All patients underwent 12-lead electrocardiogram (ECG) recording and 24-hour rhythm holter echocardiography analysis.

RESULTS

The HRV results derived from a 24-hour rhythm holter did not exhibit any significant difference (p < 0.05). In dispersion evaluations, the QTd was significantly longer in the suppression groups (groups 1 and 2), than in the replacement group (group 3) (p < 0.001 and p:0.002, respectively). The same was found for corrected QT dispersion (QTcd) (p < 0.001 and p: 0.008, respectively). In multivariate linear regression analysis, TSH was found to affect QTd (β = -0.299; p = 0.002) and QTcd (β = -0.300; p = 0.002) values independently.

CONCLUSION

In this study, it was shown that in patients with DTC receiving TSHST, QT dispersion prolonged as the TSH suppression level increased. Especially in high-risk DTC patients, evaluation of QTd may be useful in terms of evaluating cardiovascular risk and regulating TSHST level.

Sex Differences in Mouse Cardiac Electrophysiology Revealed by Simultaneous Imaging of Excitation-Contraction Coupling

Males and females differ in the basic anatomy and physiology of the heart. Sex differences are evident in cardiac repolarization in humans; women have longer corrected QT and JT intervals. However, the molecular mechanisms that lead to these differences are incompletely understood. Here, we present that, like in humans, sex differences in QT and JT intervals exist in mouse models; female mice had longer corrected QT and JT intervals compared with age-matched males. To further understand the molecular underpinning of these sex differences, we developed a novel technology using fluorescent confocal microscopy that allows the simultaneous visualization of action potential, Ca2+ transients, and contractions in isolated cardiomyocytes at a high temporal resolution. From this approach, we uncovered that females at baseline have increased action potential duration, decreased Ca2+ release and reuptake rates, and decreased contraction and relaxation velocities compared with males. Additionally, males had a shorter overall time from action potential onset to peak contraction. In aggregate, our studies uncovered male and female differences in excitation-contraction coupling that account for differences observed in the EKG. Overall, a better understanding of sex differences in electrophysiology is essential for equitably treating cardiac disease.

Electrocardiogram Changes Following Intravenous Bisphosphonate Infusion: A Systematic Review and Meta-Analysis

Bisphosphonates are first-line treatments for several bone and mineral disorders. Studies have reported an increased incidence of serious atrial fibrillation in patients receiving bisphosphonates; however, uncertainty remains as to whether electrical disturbances are precipitated by bisphosphonates. We aimed to review the literature for studies reporting electrocardiogram (ECG) findings in patients receiving intravenous bisphosphonates for any indication. We searched MEDLINE and EMBASE from inception until January 14, 2023, for studies reporting ECG parameters after intravenous bisphosphonate infusion. We excluded studies that only reported atrial fibrillation. Study quality was assessed using the Newcastle-Ottawa scale. Continuous data were meta-analyzed if reported in at least two studies. Random-effects models were fitted and reported as standardized mean difference (SMD) with 95% confidence intervals (95% CIs). We found 1083 unique records, of which 11 met our inclusion and exclusion criteria. Studies had a low to low/moderate risk of bias. Six prospective cohort studies were included in the meta-analysis. Five studies used zoledronic acid, whereas one study used pamidronate. Most studies (n = 4) were conducted in postmenopausal women with osteoporosis, one study was conducted in patients with bone metastases, and one study in children with osteoporosis secondary to cerebral palsy. Study populations ranged from n = 15 to n = 116. Heart rate-corrected QT (QTc) was significantly longer post-infusion (SMD = 0.46 ms [95% CI 0.80 to 0.11]; n = 67 patients, k = 2 studies, τ2  = 0). There were no differences in heart rate, P wave (maximum), P wave (minimum), P wave dispersion, PR interval, QRS duration, QTc, QTc (maximum), QTc (minimum), and QTc dispersion. The correlation between pre- and post-infusion QTc was not significant (p = 0.93). Overall, there is a weak association between intravenous bisphosphonate infusion and a QTc interval prolongation. However, there is insufficient evidence to support an association between intravenous bisphosphonate and any ECG variable changes, which may precipitate atrial fibrillation. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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

BACKGROUND

Conflicting findings have described the association between prolonged heart rate-corrected QT interval (QTc) and cardiovascular disease.

AIMS

To 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.

METHODS

A 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.

RESULTS

Of 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.

CONCLUSION

QTc prolongation was associated with risk of cardiovascular disease in the general population, but not in the type 2 diabetes population.

Impact of age and sex on hyperoxia-induced cardiovascular pathophysiology

Hyperoxia is characterized by pronounced inflammatory responses, pulmonary cell apoptosis, and adverse cardiac remodeling due to an excess supply of oxygen. Hyperoxic episodes are frequent in mechanically ventilated patients and are associated with in-hospital mortality. This study extends the analysis of prior published research by our group as it investigates the influence of age in male and female rodents exposed to hyperoxic conditions. Age is an independent cardiovascular risk factor, often compounded by variables like obesity, diabetes, and a decline in sex hormones and their receptors. This study simulates clinical hyperoxia by subjecting rodents to > 90 % of oxygen for 72 h and compares the changes in cardiac structural and functional parameters with those exposed to normal air. While in both sexes conduction abnormalities with ageing were discernible, aged females owing to their inherent higher baseline QTc, were at a higher risk of developing arrhythmias as compared to age-matched males. Quantitative real-time RT-PCR and western blot analysis reflected altered expression of cardiac potassium channels, resulting in conduction abnormalities in aged female rodents. Unaffected by age and sex, hyperoxia-treated mice had altered body composition, as evidenced by a considerable reduction in body weight. Interestingly, compensatory hypertrophy observed as a protective mechanism in young males was absent in aged males, whereas protection of hearts from hyperoxia-induced cardiac hypertrophy was absent in aged female mice, both of which may be at least in part due to a reduction in sex steroid receptors and the systemic steroid levels. Finally, statistical analysis revealed that hyperoxia had the greatest impact on most of the cardiac parameters, followed by age and then sex. This data established an imperative finding that can change the provision of care for aged individuals admitted to ICU by elucidating the impact of intrinsic aging on hyperoxia-induced cardiac remodeling.

Grade III Severe QT Prolongation in an Indian Male on All-Oral Longer Regimen for Multidrug-Resistant Pulmonary Tuberculosis: World's First Case

Antitubercular drugs are associated with several adverse drug reactions (ADRs). Some of these ADRs are life-threatening and require immediate attention and hospital admission. With the development of new regimens and inclusions of newer drugs such as bedaquiline, pretomanid, and delamanid, it is imperative to have an eye for the side effects. A number of antitubercular drugs such as bedaquiline, moxifloxacin, clofazimine, pretomanid, and delamanid are known to cause ADRs on the heart. Herein, a case of grade III severe QT prolongation with corrected QT (QTc) of 688 ms in an Indian male on a WHO-recommended all-oral longer regimen (AOLR) for multidrug-resistant (MDR) pulmonary tuberculosis (TB) is presented. This episode happened on the sixth day post his treatment initiation, thereby making it the earliest of such findings. The patient was managed conservatively, and his baseline electrocardiogram (ECG) returned to normal with QTc of 432 ms with the offending drug as moxifloxacin, which was omitted from the regimen and replaced with delamanid. There are some cases similar to this case available in the literature; however, grade III severe QT prolongation with QTc of 688 ms in a male on a WHO-recommended all-oral longer regimen for multidrug-resistant pulmonary tuberculosis is never reported.

Genç yetişkinlerde elektrofizyolojik ve hemodinamik parametreler üzerine kafeinli içeceklerin akut etkileri

Purpose: The consumption of caffeinated beverages has significantly increased among young people in recent years. The objective of the study is to investigate the acute effects of caffeinated beverages on electrocardiographic and hemodynamic parameters of young adults. Materials and Methods: Study was designed as a non-randomized, non-placebo controlled, three-arm parallel assignment. It was conducted on 56 individuals selected from a pool of students enrolled at Aydın Adnan Menderes University. Energy drink, coffee, cola and control groups were determined according to the results of the applicant acceptance questionnaire. Blood pressure and electrocardiogram were measured before and after consuming the drinks at 30 minutes and 60 minutes. Heart rate variability was detected from electrocardiogram signal and investigated by linear analysis. Results: All caffeinated drinks increased the blood pressure. Only, heart rate was increased by energy drink and cola. There was a small increment in root-mean square differences of successive R-R intervals and the number of times successive heartbeat intervals exceed 50ms (NN50) values in coffee group. High frequency (HF) values were increased some for coffee and cola groups. But, low frequency (LF) and LF/HF values were decreased. These alterations were statistically significant for coffee group. PR interval and QRS complex did not alter, however, QTc interval was lower in energy drink and cola groups. Conclusion: Caffeinated beverage consumption has the potential to induce adverse effects on cardiovascular system of young adults. Coffee appears to be more prominent than energy drink and cola.

QT shortening: a proarrhythmic safety surrogate measure or an inappropriate indicator of it?

OBJECTIVE

To examine whether QT interval shortening is an overlooked adverse event as compared to QT prolongation through a review of preclinical, clinical and post-marketing adverse event data available to the regulator for centrally and nationally authorized medicinal products.

METHODS

Potential safety signals of QT shortening related to authorized medicinal products were detected from Eudravigilance using proportional reporting ratios. Active substances identified as having unexpected signals of QT shortening were assessed in depth using the Bradford-Hill criteria for causation. Preclinical, clinical and adverse event data related to each active substance was used in the assessments. Post marketing adverse event cases were reviewed for imputability using the French method.

RESULTS

80 adverse event cases of electrocardiogram QT shortening were detected from 13 different active substances which included antipsychotics and antiepileptics (Clozapine, Ziprasidone, Quetiapine, Olanzapine, Carbamazepine), cardiovascular drugs (Atenolol, Digoxin, Ramipril, Simvastatin), anti-inflammatories and analgesics (Ibuprofen, Paracetamol) and other substances Calcium Carbonate (Mineral Supplement/Antacid) and Fingolimod (Immunosuppressant). By comparison 404 active substances were found have a potential safety signal of Electrocardiogram QT prolongation. Following in depth review none of the 13 active substances identified were found to be clearly associated with QT shortening using the minimum level of evidence for regulatory action. In the preclinical data reviewed we observed cases of morphological changes to the action potential (AP) where the Action Potential Duration at 90% (APD₉₀) was not affected.

CONCLUSIONS

From a regulatory perspective one cannot refute the possibility of a clinically relevant risk from QT shortening through the current testing requirements. Lack of further investigations into any potential morphological changes to the AP, or APD₉₀ shortening beyond a specified threshold in our opinion does not fully exclude the possibility of proarrhythmic effects of active substances.

Prevalence of potential drug - drug interactions in the cardiothoracic intensive care unit patients in a Chinese tertiary care teaching hospital

Background

With an increasing number of reviews describing clinically significant drug–drug interactions (DDIs), the scope and severity of interactions involving commonly used drugs in cardiothoracic intensive care units (CCUs) remain unclear. This study aims to identify risk factors and determine the incidence of potential DDIs in intensive care units.

Methods

DDIs were identified based on the profile of the prescribed drug and classified according to the Micromedex drug interaction database. Potential risk factors associated with DDIs have been identified.

Results

A total of 3193 medication episodes were evaluated, and 680 DDIs (21.3%) were found. A total of 203 patients were recruited into the study, with an average of 3.4 DDIs per patient [95% confidence interval (3.2 − 3.6)]. A total of 84.2% of the patients experienced at least one DDI. Anticoagulant and antiplatelet agents were involved in 33.5% (228/680) of the potential drug − drug interactions in the CCU. Univariate analysis and multiple logistic regression analysis showed that the age of the patient and the number of medications prescribed were significantly correlated with the occurrence of DDIs. In multiple linear regression analysis, the number of DDIs had a significant correlation only with the number of prescription drugs.

Conclusions

A high prevalence of DDIs was observed, especially in intensive care units without pharmacist intervention and computerized drug monitoring systems, highlighting the need for active surveillance to prevent potential adverse events.

The Assessment of Ventricular Arrhythmia Indicators Based on Electrocardiography in Patients With Differentiated Thyroid Cancer Followed Up With Levothyroxine Suppression

Levothyroxine suppression therapy (LST) can cause some unfavorable effects on the cardiovascular system in patients with differentiated thyroid cancer (DTC). The aim of this study was to evaluate ventricular arrhythmia predictors based on electrocardiography (ECG) in patients with DTC with LST. The ECG parameters including QT, corrected QT (QTc), Tp-e intervals, Tp-e/QT, and Tp-e/QTC ratios of 265 patients with DTC who met the inclusion criteria were compared with 100 controls. No difference was observed in the number of patients with DTC and controls with prolonged and borderline QTc interval (P = .273). Tp-e interval, Tp-e/QT, and Tp-e/QTc ratios were significantly higher in patients (P = .002, P = .02, P = .003; respectively). Linear regression analysis suggested that male gender was a predictor of higher Tp-e interval, Tp-e/QT, and Tp-e/QTc ratios (β = 4.322, R ² = 0.024, P = .042; β = 0.016, R ² = 0.048, P = .005; β = 0.015, R ² = 0.044, P = .006, respectively). A higher serum fT4 level was found to be associated with a higher Tp-e/QT ratio (β = 0.018, R ² = 0.089, P = .007). Ventricular arrhythmia indicators were found to be higher in patients with DTC with LST. Defining ventricular arrhythmia predictors through ECG, an easily accessible cardiac diagnostic tool, can be potentially useful in raising awareness of the possible cardiac harm of LST.

Correlation of Prolonged Corrected QT Interval With Ventricular Arrhythmias and In-Hospital Mortality Among ST-Elevation Myocardial Infarction Patients: A Mystique or Lucidity?

Background Ventricular arrhythmias (VAs) are a frequent cause of cardiovascular mortality, especially in developing countries. Prolongation of corrected QT (QTc) interval predisposes patients to life-threatening VAs. Our study aims to assess the correlation of prolonged QTc interval with VAs and in-hospital mortality among ST-elevation myocardial infarction (STEMI) patients.  Methods This cross-sectional study analyzed the data from 40 patients with a confirmed diagnosis of STEMI and prolonged QTc interval. The patients were evaluated for several characteristics including their electrocardiography (ECG) findings. The frequency of in-hospital mortality and VAs developed after admission were recorded. Spearman correlation was used to assess the correlation of prolonged QTc interval with VAs and in-hospital mortality. Results Out of 40 cases, 30 patients were males and 10 were females with a mean age hovering at 52.95 ± 10.65 years. The mean QTc interval of our patients was 512.02 ± 49.74 milliseconds (ms). A total of 11 (27.5%) patients developed VAs while 14 (35%) of the patients succumbed to the disease complications. Spearman correlation showed a strong significant positive correlation of QTc interval with VAs (rho = 0.658, p < 0.001) and in-hospital mortality (rho = 0.314, p = 0.04). Conclusion Prolonged QTc interval is positively correlated with VAs and in-hospital mortality among STEMI patients. These patients should be regularly monitored and must be managed with caution as they have increased chances to develop VAs and in-hospital mortality. There is an utmost need for curation of guidelines that aid in risk stratification and appropriate management of such patients.

Electrocardiographic conduction and repolarization markers associated with sudden cardiac death: moving along the electrocardiography waveform

The QT interval along with its heart rate corrected form (QTc) are well-established ECG markers that have been found to be associated with malignant ventricular arrhythmogenesis. However, extensive preclinical and clinical investigations over the years have allowed for novel clinical ECG markers to be generated as predictors of arrhythmogenesis and sudden cardiac death. Repolarization markers include the older QTc, QT dispersion and newer Tpeak - Tend intervals, (Tpeak - Tend) / QT ratios, T-wave alternans (TWA), microvolt TWA and T-wave area dispersion. Meanwhile, conduction markers dissecting the QRS complex, such as QRS dispersion (QRSD) and fragmented QRS, were also found to correlate conduction velocity and unidirectional block with re-entrant substrates in various cardiac conditions. Both repolarization and conduction parameters can be combined into the excitation wavelength (λ). A surrogate marker for λ is the index of Cardiac Electrophysiological Balance (iCEB: QT / QRSd). Other markers based on conduction-repolarization are [QRSD x (Tpeak-Tend) / QRSd] and [QRSD x (Tpeak-Tend) / (QRSd x QT)]. Advancement in technology permitted sophisticated electrophysiological analyses such as principal component analysis and periodic repolarization dynamics to further improve risk stratification. This was closely followed by other novel indices including ventricular ectopic QRS interval, the f99 index and EntropyXQT, which integrates mathematical and physical calculations for determining the risk markers. Though proven to be effective in limited patient cohorts, more clinical studies across different cardiac pathologies are required to confirm their validity. As such, this review seeks to encapsulate the development of old and new ECG markers along with their associated utility and shortcomings in clinical practice.

QT Prolongation and Malignant Arrhythmia: How Serious a Problem?

QT prolongation constitutes one of the most frequently encountered electrical disorders of the myocardium. This is due not only to the presence of several associated congenital syndrome but also, and mainly, due to the QT-prolonging effects of several acquired conditions, such as ischaemia and heart failure, as well as multiple medications from widely different categories. Propensity of repolarization disturbances to arrhythmia appears to be inherent in the function of and electrophysiology of the myocardium. In the present review the issue of QT prolongation will be addressed in terms of pathophysiology, arrhythmogenesis, treatment and risk stratification approaches. Although already discussed in literature, it is hoped that the mechanistic approach of the present review will assist in improved understanding of the underlying changes in electrophysiology, as well as the rationale for current diagnostic and therapeutic approaches.