Sexual Dimorphisms, Anti-Hormonal Therapy and Cardiac Arrhythmias

Prevalence of Cardiac Arrhythmias in Transgender and Nonbinary Adult Community Health Center Patients

Purpose: Sex differences in cardiac arrhythmias are well established. This study aimed to explore the prevalence of arrhythmias in transgender and nonbinary (TGNB) adults. Methods: This cross-sectional study utilized electronic medical records from a center specializing in TGNB care. Adults aged ≥18 years with ≥2 medical visits between January 1, 2010, and December 31, 2021, were categorized into self-reported gender groups: TGNB (transgender men, transgender women, nonbinary [NB]-assigned male at birth, NB-assigned female at birth), cisgender men, and cisgender women. The primary outcome was any arrhythmia using age- and race-adjusted regression models comparing transgender patients with cisgender men and cisgender women. Prevalence of arrhythmias was explored in transgender people with a gender-affirming hormone therapy (GAHT) prescription. Results: The sample included 49,862 adults, with 7121 (14%) TGNB persons. Median age was 28 years. Prevalence of arrhythmias was low (0.7-1.4% NB persons, 1.4-1.5% transgender persons). After adjustment, transgender women and transgender men had similar odds of any arrhythmia compared with cisgender men (transgender women: adjusted odds ratio [aOR] 0.89, 95% confidence interval [CI] 0.63-1.24, p = 0.52; transgender men: aOR 1.17, 95% CI 0.82-1.62, p = 0.37), but higher odds of any arrhythmia compared with cisgender women (transgender women: aOR 1.65, 95% CI 1.13-2.34, p = 0.01; transgender men: aOR 2.15, 95% CI 1.48-3.04, p < 0.001). Prevalence of arrhythmias appeared similar among transgender adults regardless of GAHT use (transgender men: 1.5% vs 1.9%, transgender women: 1.2% vs 2.1%). Conclusion: Further research examining arrhythmias in TGNB patients and across gender minority subgroups is warranted, including longitudinal studies evaluating the potential impact of GAHT.

Implantable Cardioverter Defibrillators in Prevention of Sudden Cardiac Death in Kidney Transplant Recipients: A Case Series and an Appraisal of Current Evidence

Background: Cardiovascular diseases, including sudden cardiac death (SCD), are the leading cause of mortality among kidney transplant recipients (KTRs). While implantable cardioverter defibrillators (ICDs) are established for SCD prevention in the general population, data on the benefits in patients with CKD is scarce and controversial, and there is no established general consensus on their use in this group of patients. Furthermore, data for KTRs are lacking. The aim of this study is to present our experience with ICDs in KTRs and evaluate the outcomes in this population. Methods: We retrospectively analyzed medical records of KTRs who received a kidney allograft between October 1973 and December 2023 and received ICDs for the prevention of SCD. Results: Of 2282 KTRs, 10 patients (0.44%) underwent an ICD implantation with an average age of 60.6 years at the time of implantation; 9 were male. Primary prevention of SCD was the most common indication, with only one patient receiving an ICD following sudden cardiac arrest. The female patient received an ICD while on dialysis, and the rest of the patients received ICDs in the posttransplant period with an average time of 9.1 years after KT. Kidney allograft function was reduced in all patients at the time of the ICD implantation with an average estimated glomerular filtration rate (eGFR) of 44 mL/min/1.73 m2. No ICD-related complications were recorded. Six patients are alive with an average follow-up of 5.2 years. Conclusions: ICD implantation in carefully selected KTRs may offer survival benefits and can be a valuable tool in preventing SCD. Larger studies are needed to confirm these findings and establish clear guidelines for ICD use in this specific population.

Exploring the impact of a KCNH2 missense variant on Long QT syndrome: insights into a novel gender-selective, incomplete penetrance inheritance mode

Background

Long QT syndrome (LQTS) is an inherited malignant arrhythmia syndrome that poses a risk of sudden death. Variants in the Potassium Voltage-Gated Channel Subfamily H Member 2 (KCNH2) gene are known to cause Long QT syndrome through an autosomal dominant inheritance pattern. However, as of now, there have been no reports of any KCNH2 variant leading to Long QT syndrome exhibiting incomplete penetrance that is influenced by gender.

Methods

Whole-exome sequencing (WES) was conducted on the proband to identify pathogenic variants. Subsequently, Sanger sequencing was employed to validate the identified likely pathogenic variants in all family members.

Results

We analyzed a pedigree spanning three-generations afflicted by Long QT syndrome. WES revealed a novel KCNH2 missense variant (p.Val630Gly, c.1889 T>G) as the causative factor for the family's phenotype. Within this family, all three male carriers of the KCNH2 variant carriers exhibited the Long QT syndrome phenotype: one experienced sudden death during sleep, another received an implantable cardioverter defibrillator (ICD), and a younger man displayed a prolonged QTc interval without any instances of syncope or malignant arrhythmia to date. Interestingly, the middle-aged female carrier showed no Long QT Syndrome phenotype. However, her offspring, diagnosed with Turner syndrome (45, X) and also a carrier of this variant, experienced frequent syncope starting at 12 years old and was diagnosed with Long QT syndrome, leading to an ICD implantation when she was 15 years old. These observations suggest that the manifestation of Long QT syndrome associated with this KCNH2 variant exhibits incomplete penetrance influenced by gender within this family, indicating potential protective mechanisms against the syndrome in females affected by this variant.

Conclusion

Our investigation has led to the identification of a novel pathogenic KCNH2 variant responsible for Long QT syndrome within a familial context characterized by gender-selective, incomplete penetrance. This discovery highlights a unique pathogenic inheritance pattern for the KCNH2 gene associated with Long QT syndrome, and could potentially shed light on the distinct penetrance behaviors and patterns of the KCNH2 gene. This discovery broadens our exploration of the KCNH2 gene in cardiac arrhythmias, highlighting the intricate genetic dynamics behind Long QT syndrome.

KCNH2 mutation c.3099_3112del causes congenital long QT syndrome type 2 with gender differences

INTRODUCTION

Long QT Syndrome (LQTS) is an inherited disease with an abnormal electrical conduction system in the heart that can cause sudden death as a result of QT prolongation. LQT2 is the second most common subtype of LQTS caused by loss of function mutations in the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene. Although more than 900 mutations are associated with the LQTS, many of these mutations are not validated or characterized.

METHODS AND RESULTS

Sequencing analyses of genomic DNA of a family with LQT2 identified a putative mutation. i.e., KCNH2(NM_000238.3): c.3099_3112del, in KCNH2 gene which appeared to be a definite pathogenic mutation. The family pedigree information showed a gender difference in clinical features and T-wave morphology between male and female patients. The female with mutation exhibited recurring ventricular arrhythmia and syncope, while two male carriers did not show any symptoms. In addition, T-wave in females was much flatter than in males. The female proband showed a positive reaction to the lidocaine test. Lidocaine injection almost completely blocked ventricular arrhythmia and shortened the QT interval by ≥30 ms. Treatment with propranolol, mexiletine, and implantation of cardioverter-defibrillators prevented the sustained ventricular tachycardia, ventricular fibrillation, and syncope, as assessed by a 3-year follow-up evaluation.

CONCLUSIONS

A putative mutation c.3099_3112del in the KCNH2 gene causes LQT2 syndrome, and the pathogenic mutation mainly causes symptoms in female progeny.

Injectable Contraceptive, Depo-Provera, Produces Erratic Beating Patterns in Patient-Specific Induced Pluripotent Stem Cell-derived Cardiomyocytes with Type 2 Long QT Syndrome

BACKGROUND

Long QT syndrome type 2 (LQT2) is caused by pathogenic variants in KCNH2. LQT2 may manifest as QT prolongation on an ECG and present with arrhythmic syncope/seizures, sudden cardiac arrest/death. Oral progestin-based contraceptives may increase the risk of LQT2-triggered cardiac events in women. We previously reported on a LQT2 woman with recurrent cardiac events temporally related and attributed to the progestin-based contraceptive, medroxyprogesterone acetate ("Depo-Provera", Depo).

OBJECTIVE

To evaluate the arrhythmic-risk of Depo in a patient-specific induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM) model of LQT2.

METHODS

An iPSC-CM line was generated from a 40-year-old female with p.G1006Afs*49-KCNH2. A CRISPR/Cas9 gene-edited/variant-corrected, isogenic control (IC) iPSC-CM line was generated. FluoVolt was used to measure the action potential duration (APD) following treatment with 10 μM Depo. Erratic beating patterns characterized as alternating spike amplitudes, alternans, or early after depolarization-like phenomena were assessed using multi-electrode array (MEA) following 10 μM Depo, 1 μM isoproterenol (ISO), or combined Depo + ISO treatment.

RESULTS

Depo treatment shortened the APD-90 of the G1006Afs*49 iPSC-CMs from 394±10 ms to 303±10 ms (p<0.0001). Combined Depo and ISO treatment increased the percent of electrodes displaying erratic beating in G1006Afs*49 iPSC-CMs [baseline 18±5% vs. Depo + ISO 54±5% (p<0.0001)] but not in IC iPSC-CMs [baseline 0±0% vs. Depo + ISO 10±3% (p=0.9659)].

CONCLUSION

This cell study provides a potential mechanism for the patient's clinically documented Depo-associated episodes of recurrent ventricular fibrillation. This in-vitro data should prompt a large-scale clinical assessment of Depo's potential pro-arrhythmic effect in women with LQT2.

Arrhythmias in transgender individuals

The need to improve access to health services for the transgender community has become evident, especially concerning cardiovascular risk, which is higher compared to the general population. Surgical procedures and hormone therapies are common in this population to affirm gender identity, but they pose challenges as they are associated with disruptions in lipid metabolism, body fat concentration, and insulin resistance. Additionally, there is an increased risk of adverse cardiovascular events such as venous thromboembolism, stroke, and myocardial infarction. The influence of sex hormones on the electrophysiological properties of the heart has been studied, highlighting gender differences that may predispose the transgender population to cardiac arrhythmias. Exogenous hormone therapy, for both transgender women and men, can affect the QT interval and increase the risk of arrhythmias, including atrial fibrillation. Although the incidence of arrhythmias in the transgender population is not entirely clear, evidence suggests the need for careful cardiovascular monitoring and consideration of risk factors before initiating hormone therapies.

Cardiac Repolarization in Health and Disease

Abnormal cardiac repolarization is at the basis of life-threatening arrhythmias in various congenital and acquired cardiac diseases. Dysfunction of ion channels involved in repolarization at the cellular level are often the underlying cause of the repolarization abnormality. The expression pattern of the gene encoding the affected ion channel dictates its impact on the shape of the T-wave and duration of the QT interval, thereby setting the stage for both the occurrence of the trigger and the substrate for maintenance of the arrhythmia. Here we discuss how research into the genetic and electrophysiological basis of repolarization has provided us with insights into cardiac repolarization in health and disease and how this in turn may provide the basis for future improved patient-specific management.

Cardiovascular outcomes in transgender individuals in Sweden after initiation of gender-affirming hormone therapy

AIMS

We compared the incidence of cardiovascular disease (CVD) in transgender participants with a diagnosis of gender dysphoria (GD) with and without gender-affirming hormone therapy (GAHT) to the incidence observed in the general population.

METHODS AND RESULTS

The population-based cohort included all individuals >10 years in Sweden linked to Swedish nationwide healthcare Registers (2006-2016). Two comparator groups without GD/GAHT were matched (1:10) on age, county of residence, and on male and female birth-assigned sex, respectively. Cox proportional models provided hazard ratios (HR) and 95% confidence intervals (CI) for CVD outcomes. Among 1779 transgender individuals (48% birth-assigned males [AMAB], 52% birth-assigned females [AFAB]) 18 developed CVD, most of which were conduction disorders. The incidence of CVD for AFAB individuals with GD was 3.7 per 1000 person-years (95%CI: 1.4-10.0). AMAB individuals with GD had an incidence of CVD event of 7.1 per 1000 person-years (95%CI: 4.2-12.0). The risk of CVD event was 2.4 times higher in AMAB individuals (HR: 2.4, 95%CI: 1.3-4.2) compared to cisgender women, and 1.7 higher compared to cisgender men (HR: 1.7, 95%CI: 1.0-2.9). Analysis limited to transgender individuals without GAHT yielded similar results to those with GAHT treatment.

CONCLUSION

The incidence of CVD among GD/GAHT individuals was low, although increased compared to matched individuals without GD and similar to the incidence among GD/no GAHT individuals, thus not lending support for a causal relationship between treatment and CVD outcomes. Larger studies with longer follow-up are needed to verify these findings, as well as possible effect modification by comorbidity.

Use of oral contraceptives in women with congenital long QT syndrome

BACKGROUND

Use of oral contraceptives (OCs) may modulate the clinical course of women with congenital long QT syndrome (LQTS). The safety of OC use by sex hormone content has not been assessed in women with LQTS.

OBJECTIVE

We aimed to evaluate the association of OCs with the risk of cardiac events (CEs) in women with LQTS.

METHODS

Beginning in 2010, information on menarche onset, OC use, pregnancy, and menopause were obtained from women enrolled in the Rochester LQTS Registry. Type of OC was categorized as progestin-only, estrogen-only, or combined (estrogen/progestin). Andersen-Gill multivariate modeling was used to evaluate the association of time-dependent OC use with the burden of CE (total number of syncope, aborted cardiac arrest, and LQTS-related sudden cardiac death) from menarche onset through 40 years. Findings were adjusted for genotype, corrected QT duration, and time-dependent β-blocker therapy.

RESULTS

A total of 1659 women with LQTS followed through March 2021, of whom 370 (22%) were treated with an OC. During a cumulative follow-up of 35,797 years, there were a total of 2027 CE. Multivariate analysis showed that progestin-only OC was associated with a pronounced 2.8-fold (P = .01) increased risk of CEs in women who did not receive β-blocker therapy, while β-blockers were highly protective during progestin-only OC treatment (hazard ratio 0.22; P = .01; P = .006 for β-blocker-by-OC interaction). The risk associated with OC use without concomitant β-blocker treatment was pronounced in women with LQTS type 2.

CONCLUSION

Our findings suggest that progestin-only OC should not be administered in women with LQTS without concomitant β-blocker therapy. OCs should be used with caution in women with LQTS type 2.