Short QT interval in clinical practice

Congenital short QT syndrome: A review focused on electrocardiographic features

Congenital short QT syndrome is a very low prevalence inherited primary arrhythmia syndrome first reported in 2000 by Gussak et al., who described two families with a short QT interval, syncope, and sudden cardiac death. In 2004, Ramon Brugada et al. identified the first genetic type of this entity. To date, a total of nine genotypes have been described. The diagnosis is easy from the electrocardiogram (ECG), not only due to the short QT duration, but also based on other aspects covered in this review. During 24-h Holter monitoring, paroxysmal atrial fibrillation spontaneously converting to sinus rhythm may be found. Even though the T wave may appear symmetric on the ECG, the T loop of the vectorcardiogram confirms that the T wave is constantly asymmetric due to the presence of dashes closer to each other in the efferent branch. In this review, we also describe the minus-plus T wave sign that we have described in a previously published article. In addition to congenital causes, we briefly highlight the existence of numerous acquired causes of short QT interval.

Pilot Study on QTc Interval in Dogs Treated with Domperidone

Domperidone is used as an immunomodulatory drug for Leishmania infantum infection and disease in dogs. However, a pro-arrhythmic side effect, caused by prolonged QT intervals, is reported in humans. This pilot study evaluated the corrected QT (QTc) interval in dogs treated with domperidone for preventive or therapeutic management of leishmaniosis. The electrocardiogram and blood concentration of creatinine, urea nitrogen, sodium, potassium, and chloride were evaluated seven days before the start and on the last day of therapy in 17 dogs receiving domperidone for four weeks. In two dogs, the QTc interval was measured before and 2 h, 3 h, and 12 h after administration of the drug on the first day of treatment. After treatment, QTc measures and chloride concentrations increased significantly, although the QTc value slightly exceeded the upper reference limit only in one dog, and chloride concentrations were always normal. Creatinine concentrations significantly decreased after therapy. In the two dogs monitored at different times on the first day of treatment, QTc values were always normal. Domperidone caused a slight prolongation of QTc interval, and further studies should be made for a risk assessment in dogs with cardiac diseases, electrolytic imbalance, and in those receiving drugs increasing QT interval or competing with domperidone metabolism.

Artificial intelligence-enabled electrocardiography identifies severe dyscalcemias and has prognostic value

CONTEXT

Abnormal serum calcium concentrations affect the heart and may alter the electrocardiogram (ECG), but the detection of hypocalcemia and hypercalcemia (collectively dyscalcemia) relies on blood laboratory tests requiring turnaround time.

OBJECTIVE

The study aimed to develop a bloodless artificial intelligence (AI)-enabled (ECG) method to rapidly detect dyscalcemia and analyze its possible utility for outcome prediction.

METHODS

This study collected 86,731 development, 15,611 tuning, 11,105 internal validation, and 8401 external validation ECGs from electronic medical records with at least 1 ECG associated with an albumin-adjusted calcium (aCa) value within 4 h. The main outcomes were to assess the accuracy of AI-ECG to predict aCa and follow up these patients for all-cause mortality, new-onset acute myocardial infraction (AMI), and new-onset heart failure (HF) to validate the ability of AI-ECG-aCa for previvor identification.

RESULTS

ECG-aCa had mean absolute errors (MAE) of 0.78/0.98 mg/dL and achieved an area under receiver operating characteristic curves (AUCs) 0.9219/0.8447 and 0.8948/0.7723 to detect severe hypercalcemia and hypocalcemia in the internal/external validation sets, respectively. Although < 20 % variance of ECG-aCa could be explained by traditional ECG features, the ECG-aCa was found to be associated with more complications. Patients with ECG-hypercalcemia but initially normal aCa were found to have a higher risk of subsequent all-cause mortality [hazard ratio (HR): 2.05, 95 % conference interval (CI): 1.55-2.70], new-onset AMI (HR: 2.88, 95 % CI: 1.72-4.83), and new-onset HF (HR: 2.02, 95 % CI: 1.38-2.97) in the internal validation set, which were also seen in external validation.

CONCLUSION

The AI-ECG-aCa may help detecting severe dyscalcemia for early diagnosis and ECG-hypercalcemia also has prognostic value for clinical outcomes (all-cause mortality and new-onset AMI and HF).

Primary Hyperparathyroidism Is Associated With Shorter QTc Intervals, but Not Arrhythmia

CONTEXT

Primary hyperparathyroidism (PHPT) is associated with subclinical cardiovascular disease, but data regarding cardiac conduction abnormalities are limited.

OBJECTIVE AND DESIGN

Retrospective cross-sectional comparison of cardiac conduction in patients with PHPT or thyroid disease (TD).

PARTICIPANTS AND SETTING

Patients ≥40 years old who underwent parathyroidectomy or thyroidectomy at a single tertiary institution from 2013 to 2018.

METHODS AND OUTCOMES

Demographics and preoperative electrocardiogram (EKG) parameters were compared using the Mann-Whitney U, chi-square test, and linear regression.

RESULTS

A total of 1242 patients were included: 49.8% PHPT (n = 619) and 50.2% TD (n = 623). Median age was 60.5 years [interquartile range (IQR) 53.6-67.9]. Compared to controls, PHPT patients had higher median serum calcium [10.7 mg/dL (IQR 10.4-11.1) vs 9.5 mg/dL (IQR 9.3-9.8), P < 0.001] as expected, as well as, a higher prevalence of hyperlipidemia (49% vs 36%, P < 0.001) and hypertension (50.1% vs 42.2%, P < 0.01). Based on EKG, there was no difference in PR interval or the prevalence of arrhythmia, atrioventricular block, ST segment/T wave changes, premature ventricular complexes, right bundle branch block, or left bundle branch block after adjusting for covariates. The PHPT group had a lower mean corrected QT interval (414 ± 24) ms vs 422 ± 24 ms, P < 0.01), adjusted for covariates. Serum calcium predicted QTc independently of age, sex, and other covariates.

CONCLUSIONS

In the largest study to date, PHPT patients had shorter QTc intervals compared to TD controls but no increased prevalence of arrhythmia based on preoperative EKG.

Assessment of Cardiovascular Safety of Anti-Osteoporosis Drugs

The incidence of osteoporosis and cardiovascular disease increases with age, and there are potentially shared mechanistic associations between the two conditions. It is therefore highly relevant to understand the cardiovascular implications of osteoporosis medications. These are presented in this narrative review. Calcium supplementation could theoretically cause atheroma formation via calcium deposition, and in one study was found to be associated with myocardial infarction, but this has not been replicated. Vitamin D supplementation has been extensively investigated for cardiac benefit, but no consistent effect has been found. Despite findings in the early 21st century that menopausal hormone therapy was associated with coronary artery disease and venous thromboembolism (VTE), this therapy is now thought to be potentially safe (from a cardiac perspective) if started within the first 10 years of the menopause. Selective estrogen receptor modulators (SERMs) are associated with increased risk of VTE and may be related to fatal strokes (a subset of total strokes). Bisphosphonates could theoretically provide protection against atheroma. However, data from randomised trials and observational studies have neither robustly supported this nor consistently demonstrated the potential association with atrial fibrillation. Denosumab does not appear to be associated with cardiovascular disease and, although parathyroid hormone analogues are associated with palpitations and dizziness, no association with a defined cardiovascular pathology has been demonstrated. Finally, romosozumab has been shown to have a possible cardiovascular signal, and therefore post-market surveillance of this therapy will be vital.

ECG changes in patients with opioid use disorder; P-QT wave dispersion: a retrospective study

OBJECTIVE

We aimed to examine the electrocardiographic arrhythmia risk predictors in patients with opioid use disorder by P wave dispersion, QT dispersion, and by comparing Tp-e/QTc ratio with healthy controls.

METHODS

One hundred seventeen patients who were diagnosed with opioid use disorder according to DSM-5 criteria and who were hospitalized in 25 Aralık Gaziantep State Hospital AMATEM (Alcohol and substance addiction treatment center) service and a healthy control group consisting of 168 subjects were included in the study. Electrocardiography (ECG) scans of all participants were performed in the supine position and at rest. P wave dispersion, QT dispersion, and Tp-e/QTc ratio were calculated.

RESULTS

Of all the participants, 12 were women (4.21%), 273 (95.78%) were men. The mean age of all participants was 30.42 ± 9.36 years. No difference was found between the gender, mean age, marital status, educational level, and smoking status of the participants (p > 0.05). The entire patient group was using heroin. Heart rate of the patient group was calculated as 68.14 ± 13.26 beats per minute, being lower than healthy controls (p < 0.05). Although QT dispersion value was lower than healthy controls (p < 0.05); P wave dispersion did not differ between groups (p > 0.05).

CONCLUSION

It is thought that the patients with opioid use disorder are at risk for cardiac arrhythmia based on our findings. Therefore, physicians should be careful about cardiac rhythm and conduction problems while organizing any treatment of these patients.

The Short QTc Is a Marker for the Development of Atrial Flutter and Atrial Fibrillation

A short QT interval has been difficult to define, and there is debate whether it exists outside of an extremely small group of individuals with inherited channelopathies and whether it predicts cardiac arrhythmias. The objective was to identify cases with short QT and their consequences. Our hospital ECG database was screened for cases with a QTc based on the Bazett formula (QTcBZT) of less than 340 ms. The QTc was recalculated using the spline (QTcRBK) formula, which more accurately adjusts for the heart rate and identifies cases based on percentile distribution of the QT interval. The exclusion criteria were presence of bundle branch block, arrhythmias, or electronic pacemakers. An age- and sex-matched cohort was obtained from individuals with normal QT intervals with the same exclusion criteria. There were 28 cases with a short QTc (QTcRBK < 380 ms). The age was 69.6 ± 14.6 years (mean ± SD) (50% males). The QT interval was 305.7 ± 61.1 ms with QTcRBK 308.4 ± 31.4 ms. Subsequent ECGs showed atrial flutter in 21%, atrial fibrillation in 18%, and atrial tachycardia in 4% of cases. Thus, atrial arrhythmias occurred in 43% of cases. This incidence was significantly (p < 0.0001) greater than the incidence of atrial arrhythmias in age- and sex-matched controls. In conclusion, a short QT interval can be readily identified based on the first percentile of the new QTc formula. A short QTc is an important marker for the development of atrial arrhythmias, including atrial flutter and atrial fibrillation, with the former predominating. It should be part of patient assessment and warrants consideration to develop strategies for detection and prevention of atrial arrhythmias.

Effect of Aqueous Extract of Adansonia digitata Stem Bark on the Development of Hypertension in L-NAME-Induced Hypertensive Rat Model

BACKGROUND

Adansonia digitata is a plant used against cardiovascular disorders in African folk medicine. We assessed the effects of the aqueous extract of its stem bark on the development of hypertension in L-NAME-induced hypertensive rats.

METHODS

The animals were administered L-NAME once daily for 3 weeks (25 mg/kg, i.p.), concomitantly with aqueous extract of A. digitata stem bark (100 and 200 mg/kg, p.o.) or captopril (20 mg/kg, p.o.). Then, hemodynamic and electrocardiographic parameters, oxidative stress markers, and the lipid profile were assessed in the blood and heart, aorta, and kidney homogenates, and histopathological analyses were performed.

RESULTS

L-NAME-induced hypertensive control animals, but not the animals concomitantly treated with A. digitata extract, displayed increases in the mean arterial blood pressure (21.64% difference, p < 0.001, vs. dose 200 mg/kg), systolic arterial blood pressure (21.33%, p < 0.001), and the diastolic arterial blood pressure (21.84%, p < 0.001). In addition, hypertensive control animals displayed (i) increases in serum triglycerides, total cholesterol, LDL, and creatinine levels, malondialdehyde and transaminase activities, and atherogenic index; (ii) decreases in serum HDL, catalase, reduced glutathione, and nitric oxide; and (iii) aorta wall thickening, inflammatory cell infiltration, and cell loss in the cardiac muscle and renal tissues. As captopril, the extract prevented hypertension-like changes in lipid profile, cardiac, hepatic, and renal affection indicators, and oxidative stress markers.

CONCLUSION

Our findings suggest that the extract of A. digitata has antihypertensive and antioxidant effects in L-NAME-induced hypertension rat models. These effects partly justify the traditional medicine use against cardiovascular disorders.

Calcium Handling Defects and Cardiac Arrhythmia Syndromes

Calcium ions (Ca²⁺) play a major role in the cardiac excitation-contraction coupling. Intracellular Ca²⁺ concentration increases during systole and falls in diastole thereby determining cardiac contraction and relaxation. Normal cardiac function also requires perfect organization of the ion currents at the cellular level to drive action potentials and to maintain action potential propagation and electrical homogeneity at the tissue level. Any imbalance in Ca²⁺ homeostasis of a cardiac myocyte can lead to electrical disturbances. This review aims to discuss cardiac physiology and pathophysiology from the elementary membrane processes that can cause the electrical instability of the ventricular myocytes through intracellular Ca²⁺ handling maladies to inherited and acquired arrhythmias. Finally, the paper will discuss the current therapeutic approaches targeting cardiac arrhythmias.

Pathophysiology of Calcium Mediated Ventricular Arrhythmias and Novel Therapeutic Options with Focus on Gene Therapy

Cardiac arrhythmias constitute a major health problem with a huge impact on mortality rates and health care costs. Despite ongoing research efforts, the understanding of the molecular mechanisms and processes responsible for arrhythmogenesis remains incomplete. Given the crucial role of Ca²⁺-handling in action potential generation and cardiac contraction, Ca²⁺ channels and Ca²⁺ handling proteins represent promising targets for suppression of ventricular arrhythmias. Accordingly, we report the different roles of Ca²⁺-handling in the development of congenital as well as acquired ventricular arrhythmia syndromes. We highlight the therapeutic potential of gene therapy as a novel and innovative approach for future arrhythmia therapy. Furthermore, we discuss various promising cellular and mitochondrial targets for therapeutic gene transfer currently under investigation.

Severe hypercalcemia from multiple myeloma as an acquired cause of short QT

An otherwise healthy 64-year-old man with recently diagnosed multiple myeloma was admitted to hospital with hypercalcemia and renal failure. Despite his electrocardiogram showing short QT/QTc intervals, he was admitted without cardiac monitoring. He died suddenly a few hours later, likely from a fatal arrhythmia. This case illustrates that pronounced QT shortening from hypercalcemia is an underappreciated malignant finding that can portend a significant risk for arrhythmia and sudden cardiac death. In addition, we also discuss the causes of hypercalcemia associated short QT/QTc intervals and its ECG features.

Recent Advances in Short QT Syndrome

Short QT syndrome is a highly malignant inherited cardiac disease characterized by ventricular tachyarrhythmias leading to syncope and sudden cardiac death. It is responsible of lethal episodes in young people, mainly infants. International guidelines establish diagnostic criteria with the presence of a QTc ≤ 340 ms in the electrocardiogram despite clinical diagnostic values remain controversial. In last years, clinical diagnosis, risk stratification as well as preventive therapies have been improved due to identification of pathophysiological mechanisms. The only effective option is implantation of a defibrillator despite Quinidine may be at times an effective option. Currently, a limited number of rare variants have been identified in seven genes, which account for nearly 20–30% of families. However, some of these variants are associated with phenotypes showing a shorter QT interval but no conclusive diagnosis of Short QT syndrome. Therefore, an exhaustive interpretation of each variant and a close genotype-phenotype correlation is necessary before clinical translation. Here, we review the main clinical and genetic hallmarks of this rare entity.

Molecular Insights into the Short QT Syndrome

Short QT syndrome (SQTS) is a myocardial conduction disorder characterized by a short QT interval on electrocardiogram and predisposition to familial atrial fibrillation and/or sudden cardiac death. Genetic SQTS is primarily caused by one or more cardiac ion channelopathies, in which either impaired depolarization currents, or enhanced repolarization currents, shorten cardiac action potential duration. Given that QT interval duration is not always predictive of arrhythmia burden and risk of death in SQTS, there is a need to understand the molecular mechanisms of the condition to improve risk prognostication and potential pharmacologic treatment. In the last decade, several computational advances and in vitro preclinical studies have provided insight into the molecular mechanisms underlying congenital SQTS. In this review, we discuss recent findings in SQTS molecular mechanisms and correlate these advances with clinical guidelines for SQTS diagnosis and treatment.

Prevalence of Electrocardiographic Patterns Associated With Sudden Cardiac Death in the Spanish Population Aged 40 Years or Older. Results of the OFRECE Study

INTRODUCTION AND OBJECTIVES

Some electrocardiographic patterns are associated with an increased risk of sudden cardiac death due to ventricular arrhythmias. There is no information on the prevalence of these patterns in the general population in Spain. The objective of this study was to analyze the prevalence of these patterns and associated clinical and epidemiological factors.

METHODS

This subanalysis of the OFRECE study selected a representative sample of the Spanish population aged ≥ 40 years. We studied the presence or absence of electrocardiographic patterns of Brugada syndrome and QT interval abnormalities. Clinical data and electrocardiograms were available in all participants. Electrocardiograms were evaluated by 2 cardiologists and a third cardiologist was consulted if there was disagreement in the diagnosis. We calculated the weighted prevalence and clinical factors associated with the presence of Brugada-type patterns or QT segment abnormalities.

RESULTS

Overall, 8343 individuals were evaluated (59.2 years, 52.4% female). There were 12 Brugada cases (type 1, 2 cases; type 2, 10 cases; weighted prevalence, 0.13%). For corrected QT (QTc) analysis, we excluded participants with left bundle branch block or without sinus rhythm. Weighted prevalences were as follows: short QTc (< 340ms) 0.18%, borderline QTc (441-469ms) 8.33%, long QTc (≥ 470ms criterion) 1.01% and long QTc (≥ 480 criterion) 0.42%.

CONCLUSIONS

A total of 0.6% to 1.1% of the Spanish population aged ≥ 40 years has an electrocardiographic pattern associated with a higher risk of sudden death (Brugada syndrome, long QT, or short QT).

PQ segment depression in patients with short QT syndrome: a novel marker for diagnosing short QT syndrome?

BACKGROUND

Patients with short QT syndrome (SQTS) have an increased risk for atrial tachyarrhythmias, ventricular tachyarrhythmias, and/or sudden cardiac death. PQ segment depression (PQD) is related to atrial fibrillation and carries a poor prognosis in the setting of acute inferior myocardial infarction and is a well-defined electrocardiographic (ECG) marker of acute pericarditis.

OBJECTIVE

To evaluate the prevalence of PQD in SQTS and to analyze the association with atrial arrhythmias.

METHODS

Digitalized 12-lead ECGs of SQTS patients were evaluated for PQD in all leads and for QT intervals in leads II and V5. PQD was defined as ≥0.05 mV (0.5 mm) depression from the isoelectric line.

RESULTS

A total of 760 leads from 64 SQTS patients (mean age 36 ± 18 years; 48 [75%] men) were analyzed. PQD was seen in 265 (35%) leads from 52 (81%) patients and was more frequent in leads II, V3, aVF, V4, and I (n = 43 [67%], n = 30 [47%], n = 27 [42%], n = 25 [39%], and n = 25 [39%], respectively). Nine of 64 (14%) patients presented with atrial tachyarrhythmias, and all of them had PQD.

CONCLUSION

Fifty-two of 64 (81%) patients with SQTS reveal PQD. As PQD is rarely observed in healthy individuals, this ECG stigma may constitute a novel marker for SQTS in addition to a short QT interval.

Heart rate variability dynamics during controlled hypotension with nicardipine, remifentanil and dexmedetomidine

BACKGROUND

This study was done to investigate how nicardipine, remifentanil and dexmedetomidine affect the balance of the autonomic nervous system in patients receiving controlled hypotension under general anaesthesia by evaluating heart rate variability indices.

METHODS

Sixty-two patients were randomly allocated to either the nicardipine-sevoflurane (Group N, n = 21), remifentanil-sevoflurane (Group R, n = 21) or dexmedetomidine-sevoflurane (Group D, n = 20) group for controlled hypotension during orthognathic surgery. Electrocardiogram data acquisition was done after vital sign stabilization following anaesthesia induction (T1) and 30 min after controlled hypotension was induced (T2).

RESULTS

Total power and low frequency (LF) power was significantly decreased at T2 compared with T1 in all groups, while a decrease in high frequency (HF) power was only observed in Group N (P < 0.001). LF/HF ratios of Group R and D were significantly suppressed at T2 compared with T1 (P = 0.001 and P < 0.001, respectively), but was increased Group N (P = 0.009). The LF/HF ratio of Group N was significantly higher than Group R and D at T2 (P < 0.001 in both), with Group D showing a significantly lower LF/HF ratio compared with Group R (P < 0.001).

CONCLUSIONS

Remifentanil and dexmedetomidine did not have sympathetic nervous system-stimulating effects during controlled hypotension, while remifentanil seemed to be superior in preserving the overall balance in autonomic nervous system activity. Nicardipine was found to stimulate the sympathetic nervous system, which may be problematic in patients vulnerable to disturbances in the autonomic nervous system.

Modeling the effects of the circadian clock on cardiac electrophysiology

An internal circadian clock regulates the electrical activity of cardiac myocytes controlling the expression of potassium channel interacting protein-2 (KChIP2), which is a key regulator of cardiac electrical activity. Here, we examine how the circadian rhythm of KChIP2 expression affects the dynamics of human and murine ventricular action potentials (APs), as well as the intervals in the equivalent electrocardiograms (ECGs) reflecting the duration of depolarization and repolarization phases of the cardiac ventricular APs (QRS and QT intervals), with mathematical modeling. We show how the internal circadian clock can control the shape of APs and, in particular, predict AP, QRS, and QT interval prolongation following KChIP2 downregulation, as well as shortening of AP, QRS, and QT interval duration following KChIP2 upregulation. Based on the circadian expression of KChIP2, we can accurately predict the circadian rhythm in cardiac electrical activity and suggest the transient outward potassium currents as the key current for circadian rhythmicity. Our modeling work predicts a smaller effect of KChIP2 on AP and QT interval dynamics in humans. Taken together, these results support the role of KChIP2 as the key regulator of circadian rhythms in the electrical activity of the heart; we provide computational models that can be used to explore circadian rhythms in cardiac electrophysiology and susceptibility to arrhythmia.

No evidence of QT prolongation with supratherapeutic doses of aleglitazar

Aleglitazar is a dual peroxisome proliferator-activated receptor (PPAR)-α/γ agonist in clinical development, designed to offer a balanced activation of PPAR-α and PPAR-γ. A phase 2 trial has demonstrated improvements in dyslipidemia and glycemic control and reduction of cardiovascular risk markers in patients with type 2 diabetes mellitus treated with aleglitazar. This study evaluated whether supratherapeutic doses of aleglitazar affect cardiac repolarization, as detected by changes in the QT interval.Healthy subjects were randomized to receive single oral doses of placebo, 300 μg aleglitazar, 3000 μg aleglitazar, and 400 mg moxifloxacin, in 1 of 4 sequences. Triplicate 12-lead electrocardiogram measurements were recorded predose and regularly (0.75-72 hours) after each treatment. The primary outcome was measurement of QT interval using a study-specific correction factor for heart rate.Administration of aleglitazar (300 μg and 3000 μg) did not cause any significant QT prolongation and after aleglitazar treatment any mean increases from placebo were <5 msec, at all time points. There was a trend for aleglitazar to cause a small dose-dependent decrease in QT interval using a study-specific correction factor for heart rate. The incidence of adverse events was similar with aleglitazar (18%-20%) and placebo (26%).Single supratherapeutic doses of aleglitazar are not associated with prolongation of the QT interval corrected for heart rate.

Exercise-related QT interval shortening with a peaked T wave in a healthy boy with a family history of sudden cardiac death

An asymptomatic 15-year-old boy, who had a family history of sudden cardiac death, was referred for screening for cardiac disease. The 12-lead electrocardiogram at rest showed a short QT/QTc(Bazett)/QTc(Fredericia) interval of 320/388/364 ms, but the intervals were further shortened to 200/339/284 ms after the treadmill test concomitant with appearance of a peaked T wave. Other conventional cardiac examinations were normal, but effective refractory period was less than 180 ms in both ventricles, and double ventricular extrastimulation reproducibly induced nonsustained polymorphic ventricular tachycardia. Intravenous administration of epinephrine also induced a short QT interval and a peaked T wave, and a hump was manifested on the T wave of the first postpacing beat with a longer preceding R-R interval. Furthermore, a couple of premature ventricular complexes originated from a similar timing as the hump. Genetic analysis did not show the mutation in KCNQ1, KCNH2, KCNE1, KCNE2, KCNJ2, SCN5A genes but revealed single nucleotide polymorphism (C5457T) in SCN5A gene.