Hormones and sex differences: changes in cardiac electrophysiology with pregnancy

Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science

This updated guideline replaces the "Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science" first published in 2014. Based on the older version of the guideline, the authors have reviewed and evaluated the findings on the use of heart rate (HR) and heart rate variability (HRV) that have been published in the meantime and incorporated them into a new version of this guideline.This guideline was developed for application in clinical practice and research purposes in the fields of occupational medicine and occupational science to complement evaluation procedures with respect to exposure and risk assessment at the workplace by the use of objective physiological workload indicators. In addition, HRV is also suitable for assessing the state of health and for monitoring the progress of illnesses and preventive medical measures. It gives an overview of factors influencing the regulation of the HR and HRV at rest and during work. It further illustrates methods for measuring and analyzing these parameters under standardized laboratory and real workload conditions, areas of application as well as the quality control procedures to be followed during the recording and evaluation of HR and HRV.

Trends and Immediate Outcomes of Syncope During Pregnancy: A Narrative Review

Pregnancy-related syncope presents special difficulties due to the rapid physiological changes that occur throughout gestation. This narrative review provides a thorough summary of the patterns and pregnancy outcomes secondary to syncope during pregnancy. There is an increase in syncope burden during pregnancy, and hence it is critical that medical professionals understand the significance of syncope during pregnancy. Syncope can have a negative impact on the health of the mother as well as the fetus. Therefore, this review summarizes data from studies on syncope in pregnancy. It includes observational studies, case reports, and review articles. Early detection and proper management are very important because pregnant women who experience cardiac syncope are at risk of unfavorable neonatal and maternal outcomes. The review reveals diverse trends in syncope incidence during pregnancy, emphasizing the need for a nuanced understanding of temporal variations. Risks of injury, uteroplacental insufficiency, psychological effects, interruptions in prenatal treatment, possible aggravation of pre-existing diseases, and lifestyle changes are examples of immediate maternal repercussions. Pregnancy-related syncope is a complex condition that affects the health of the mother and the fetus. The study stresses the need for careful clinical treatment due to the rapid results and the diversity in incidence patterns. The unique component of a possible relationship to the brain health of offspring justifies further investigation in this area.

Effects of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses

Background and Aim

Pregnancy affects maternal hemodynamics. The changes in autonomic nervous system activity for hemodynamics adaptation in pregnant horses are still unclear. Thus, this study aimed to examine the effect of pregnancy on electrocardiographic, vasovagal tonus index, and echocardiographic variables in horses.

Materials and Methods

A total of 23 Thai native crossbred mares without any cardiac abnormalities were included in this study. The animals were assigned into two groups, a non-pregnant mare group (n =12) and a pregnant mare group (n = 11). Electrocardiogram recordings (paper speed = 25 mm/s and calibration = 10 mm/mV) were performed to obtain six limb leads (leads I, II, III, aVR, aVL, and aVF). The vasovagal tonus index (VVTI) was calculated to assess variability in heart rate over short periods using just 20 consecutive beats. Cardiac structure and function were evaluated by echocardiography.

Results

Heart rate, P wave duration, PR interval, QRS duration, QT interval, and T wave duration were significantly different between non-pregnant and pregnant horses (p < 0.05). Pregnant horses had significantly lower VVTI than non-pregnant (p < 0.05). There were no significant differences in cardiac structures including % interventricular septum (IVS), % left ventricular posterior wall (LVPW), IVS in diastole, left ventricular internal diameter at end-diastole, LVPW thickness at end-diastole, IVS in systole, left ventricular internal diameter at end-systole, LVPW thickness at end-systole, and left atrium/aortic roots ratio between the two groups. However, the pregnant horses had a significantly higher cardiac output and % ejection fraction than non-pregnant horses (p < 0.05).

Conclusion

This study provided the first evidence that hemodynamic adaptations during pregnancy modified cardiac conduction, vasovagal tonus index, and echocardiographic variables in horses.

Interactions of ST-elevation myocardial infarction, age, and sex and the risk of major adverse cardiovascular events among Chinese adults: a secondary analysis of a single-centre prospective cohort

OBJECTIVES

This study aimed to evaluate the interactions of ST-elevation myocardial infarction (STEMI), ageing and sex with respect to the incidence of major adverse cardiovascular events (MACE) among Chinese adults.

DESIGN

Secondary analysis of a single-centre prospective cohort.

SETTING

Patients who were admitted to cardiology clinics of the Affiliated Hospital of Jiangsu University due to acute myocardial infarction (MI) from June 2017 to November 2019 were eligible for inclusion in the study. This research only examined in-hospital cases.

PARTICIPANTS

Patients aged <18 years or confirmed dead within 24 hours from admission were excluded. A total of 843 adults were included in the analysis.

PRIMARY AND SECONDARY OUTCOME MEASURES

MACE was defined as any occurrence of cardiovascular mortality, MI recurrence, cardiogenic shock or heart failure. The relative excess risk due to interaction (RERI), attributable proportion (AP) and the synergy index were computed to quantify the interactions. Men without STEMI and adults without STEMI aged <60 years were the reference groups when examining the risk of MACE.

RESULTS

The female participants with STEMI showed a statistically higher risk of MACE compared with the male participants without STEMI (relative risk (RR): 2.713, CI: 1.350 to 5.426, p=0.005). A 3.327 times higher risk of MACE was detected in the older adults with STEMI (aged ≥60 years) compared with the adults without STEMI aged <60 years (RR: 3.327, CI: 1.414 to 8.955, p=0.01). Older female patients also had an increased risk of MACE (RR: 3.033, CI: 1.432 to 6.777, p=0.005). A positive additive interaction was detected between STEMI and age (RERI: 1.917, CI: 0.196 to 3.637; AP: 0.576, CI: 0.174 to 0.979). STEMI and sex also indicated an additive interaction (AP: 0.459, CI: 0.018 to 0.899).

CONCLUSION

In this Chinese population with MI, the risk of MACE was increased by about 2.7 times in women with STEMI compared with men without STEMI. MACE incidence increased by about 3.3 times in older patients with STEMI compared with younger patients without STEMI. STEMI and age, and STEMI and sex, may have a positive additive interaction.

Progesterone Changes the Pregnancy-Induced Adaptation of Cardiomyocyte Kv2.1 Channels via MicroRNA-29b

The cardiovascular system adaptation occurs during pregnancy to ensure adequate maternal circulation. Progesterone (P4) is widely used in hormone therapy to support pregnancy, but little is known about its effects on maternal cardiac function. In this study, we investigated the cardiac repolarization and ion channel expression in pregnant subjects and mice models and studied the effects of P4 administrations on these pregnancy-mediated adaptations. P4 administrations shortened the prolongation of QTC intervals and action potential duration (APD) that occurred during pregnancy, which was mainly attributable to the reduction in the voltage-gated potassium (Kv) current under basal conditions. In vitro studies indicated that P4 regulated the Kv2.1 channel in a bidirectional manner. At a low dose (1 μM), P4 induced upregulation of Kv2.1 through P4 receptor, while at a higher dose (5 μM), P4 downregulated Kv2.1 by targeting microRNA-29b (miR-29b). Our data showed that P4 modulated maternal cardiac repolarization by regulating Kv2.1 channel activity during pregnancy. Kv2.1, as well as miR-29b, might be used as potential therapeutic targets for adaptations of the maternal cardiovascular system or evaluation of progesterone medication during pregnancy.

Arrhythmias in Pregnancy

Increasing maternal mortality and incidence of arrhythmias in pregnancy have been noted over the past 2 decades in the United States. Pregnancy is associated with a greater risk of arrhythmias, and patients with a history of arrhythmias are at significant risk of arrhythmia recurrence during pregnancy. The incidence of atrial fibrillation in pregnancy is rising. This review discusses the management of tachyarrhythmias and bradyarrhythmias in pregnancy, including management of cardiac arrest. Management of fetal arrhythmias are also reviewed. For patients without structural heart disease, β-blocker therapy, especially propranolol and metoprolol, and antiarrhythmic drugs, such as flecainide and sotalol, can be safely used to treat tachyarrhythmias. As a last resort, catheter ablation with minimal fluoroscopy can be performed. Device implantation can be safely performed with minimal fluoroscopy and under echocardiographic or ultrasound guidance in patients with clear indications for devices during pregnancy. Because of rising maternal mortality in the United States, which is partly driven by increasing maternal age and comorbidities, a multidisciplinary and/or integrative approach to arrhythmia management from the prepartum to the postpartum period is needed.

Cardiovascular Testing and Imaging in Pregnant Women

Cardiovascular disease is a major contributor to maternal morbidity and mortality and frequently preventable. Women with known cardiovascular disease should undergo cardiac evaluation before pregnancy. Many women with pregnancy-associated cardiac complications are not previously known to have cardiac disease. Women at high risk or who have signs or symptoms suggestive of heart failure, angina, or arrhythmias should undergo prompt evaluation. This article describes various diagnostic imaging modalities that can be used in pregnancy, including indications, strengths, and limitations.

The relationship between gestational week and QT dispersion in cesarean section patients undergoing spinal anaesthesia: A prospective study

BACKGROUND

Pregnancy affects the cardiovascular system, particularly the cardiac conduction system, thereby increasing the susceptibility of patients towards arrhythmia. QT interval results in ventricular arrhythmias, predominantly polymorphic ventricular tachycardia. The present study was planned to investigate the relationship between a gestational week and QT dispersion in cesarean section patients undergoing spinal anaesthesia.

METHODS

The study included 40 patients between the ages of 18 and 45 who had no symptoms of anaemia and undergoing elective cesarean section. The patients were separated into two groups based on the gestational week as Group I <39 weeks and Group II ≥39 weeks. The patient was given a sitting position and the puncture site was cleansed with 10% povidone-iodine antiseptic solution. After placing a sterile drape on the patient, the subarachnoid space was punctured through an appropriate vertebral space (L3-L4 or L4-L5) using a pencil-point 25G spinal needle, followed by intrathecal injection of 12.5 mg (2.5 mL) 5% hyperbaric bupivacaine hydrochloride. Electrocardiographic (ECG) records were obtained both preoperatively and at 1, 5, and 10 minutes after spinal block, and the QT, QTc, QTd, and corrected QTd (QTcd) intervals were estimated using Bazett's formula.

RESULTS

There was no significant difference between the two groups within the QT and QTc intervals. QTcd measured after post-operative was significantly higher in Group II (P = .007).

CONCLUSION

The results indicated that spinal anaesthesia may prolong the QTdc interval in patients with a gestational week of ≥39 weeks undergoing cesarean section.

Pregnancy-induced increased heart rate is independent of thyroid hormones

Background

The heart rate increases by 10–20 beats per minute (bpm) throughout pregnancy in women, reaching maximum heart rate in the third trimester. During pregnancy, important changes in thyroid hormones also occur, with increases of up to 50% in the levels of triiodothyronine (T₃), the biological active thyroid hormone. In addition, T₃ has been shown to regulate cardiac electrophysiology.

Objective

Thus, in the present study the potential contribution of T₃ in pregnancy-induced increased heart rate was explored.

Methods

We compared the heart rate between nonpregnant and pregnant mice under control conditions and after altering thyroid hormone levels with T₃ and propylthiouracil (PTU, an antithyroid drug) treatments.

Results

Consistent with the clinical data, we found a 58% rise in T₃ levels during pregnancy in mice. Although pregnant mice had a higher baseline heart rate (607 ± 8 bpm, P = .004) and higher T₃ levels (1.9 ± 0.4 nM, P = .0005) than nonpregnant mice (heart rate: 546 ± 16 bpm; T₃ levels: 1.2 ± 0.1 nM), their heart rate responded similarly to T₃ treatment as nonpregnant mice (nonpregnant: Δ130 ± 22 bpm; pregnant: Δ126 ± 17 bpm, P = .858). Additionally, the heart rate remained significantly elevated (607 ± 11 bpm, P = .038) and comparable to untreated pregnant mice, after the use of the antithyroid drug PTU, although T₃ levels (1.3 ± 0.2 nM, P = .559) returned to nonpregnant values.

Conclusion

Based on these results, it is unlikely that T₃ contributes significantly to the pregnancy-induced increased heart rate.

The Link Between Sex Hormones and Susceptibility to Cardiac Arrhythmias: From Molecular Basis to Clinical Implications

It is well-known that gender is an independent risk factor for some types of cardiac arrhythmias. For example, males have a greater prevalence of atrial fibrillation and the Brugada Syndrome. In contrast, females are at increased risk for the Long QT Syndrome. However, the underlying mechanisms of these gender differences have not been fully identified. Recently, there has been accumulating evidence indicating that sex hormones may have a significant impact on the cardiac rhythm. In this review, we describe in-depth the molecular interactions between sex hormones and the cardiac ion channels, as well as the clinical implications of these interactions on the cardiac conduction system, in order to understand the link between these hormones and the susceptibility to arrhythmias.

The Pharmacodynamics of Antipsychotic Drugs in Women and Men

Background: Animal and human experiments have confirmed sex differences in the expression of hepatic enzymes that metabolize antipsychotic drugs and that may, in this way, be partly responsible for the clinical sex/gender differences observed in the efficacy and tolerability of antipsychotic treatment. Aim: The aim of this mini review is to synthesize the literature on the pharmacodynamics of male/female differential response to antipsychotic drugs. Method: Relevant search terms were used to search for pre-clinical and human trials and analysis of antipsychotic differential drug response and occurrence/severity of adverse effects in women and men. Results: The search found that sex influences drug response via the amount of a given drug that enters the brain and the number of neurotransmitter receptors to which it can bind. Consequently, sex partly determines the efficacy of a specific drug and its liability to induce unwanted effects. There are other factors that can overshadow or enhance the dimorphic effect of sex, for instance, the host's age, hormonal status, diet and life style as well as the molecular structure of the drug and its dose, and the method of its administration. Most of all, the host's individual genetics affects each step of a drug's pharmacodynamics. Conclusion: On average, women's psychotic symptoms respond to antipsychotic drugs at doses lower than men's. This means that many women may be de facto overdosed and, thus, experience unnecessary adverse effects. That being said, factors such as genetics and age probably determine drug response and tolerability to a greater degree than do biological sex or gender social roles.

Cardioautonomic control in healthy singleton and twin pregnancies

In conjunction with significant cardiovascular adaptation, changes in cardioautonomic balance, specifically greater sympathetic activation and vagal withdrawal, are considered normal adaptations to healthy singleton pregnancy. Cardiovascular adaptation to twin pregnancy is more profound than that of singleton pregnancies; however, the changes in cardioautonomic control during multifetal gestation are unknown. To address this gap, beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured continuously in 25 twin pregnancies and 25 singleton pregnancies (matched for age, prepregnancy body mass index, and gestational age) during 10 min of rest. Data extracted from a 3- to 5-min period were used to analyze heart rate variability (HRV), blood pressure variability (BPV), cardiovagal baroreflex gain, and cardiac intervals as indicators of cardioautonomic control. Independent t tests were used to determine statistical differences between groups (α = 0.05), and the false rate discovery was determined to adjust for multiple comparisons. Resting heart rate was greater in twin compared with singleton pregnancies (91 ± 10 vs. 81 ± 10 beats/min; P = 0.001), but blood pressure was not different. Individuals with twin pregnancies had lower HRV, evidenced by lower standard deviation of R-R intervals (32 ± 11 vs. 47 ± 18 ms; P = 0.001), total power (1,035 ± 810 vs. 1,945 ± 1,570 ms²; P = 0.004), and high frequency power (224 ± 262 vs. 810 ± 806 ms²; P < 0.001) compared with singleton pregnancies. There were no differences in cardiac intervals, BPV, and cardiovagal baroreflex gain between groups. Our findings suggest that individuals with twin pregnancies have greater sympathetic and lower parasympathetic contributions to heart rate and that cardiac, but not vascular, autonomic control is impacted during twin compared with singleton pregnancy.NEW & NOTEWORTHY Individuals with healthy twin pregnancies had lower overall heart rate variability compared with those with singleton pregnancies at similar gestational ages. These results suggest a greater sympathetic and reduced parasympathetic contribution to cardiac control in twin pregnancies. Baseline heart rate was elevated, while arterial pressure and spontaneous cardiovagal baroreflex gain were not different between groups. This was result of the upward resetting of the cardiovagal baroreflex during healthy twin pregnancy, thus maintaining arterial pressure.

Incidence of Syncope During Pregnancy: Temporal Trends and Outcomes

Background

We examined temporal trends, timing, and frequency, as well as adverse neonatal and maternal outcomes occurring in the first year postpartum among women experiencing syncope during pregnancy.

Methods and Results

This was a retrospective study of pregnancies between January 1, 2005, and December 31, 2014, in the province of Alberta, Canada. Of 481 930 pregnancies, 4667 had an episode of syncope. Poisson regression analysis found a 5% increase/year (rate ratio, 1.05; 95% CI, 1.04–1.06) in the age‐adjusted incidence of syncope. Overall, 1506 (32.3%) of the syncope episodes first occurred in the first trimester, 2058 (44.1%) in the second trimester, and 1103 (23.6%) in the third trimester; and 8% (n=377) of pregnancies had >1 episode of syncope. Compared with women without syncope, women who experienced syncope were younger (age <25 years; 34.7% versus 20.8%; P<0.001), and primiparous (52.1% versus 42.4%; P<0.001). The rate of preterm birth was higher in pregnancies with syncope during the first trimester (18.3%), compared with the second (15.8%) and third trimesters (14.2%) and pregnancies without syncope (15.0%; P<0.01). The incidence of congenital anomalies among children born of pregnancies with multiple syncope episodes was significantly higher (4.9%) compared with children of pregnancies without syncope (2.9%; P<0.01). Within 1 year after delivery, women with syncope during pregnancy had higher rates of cardiac arrhythmias and syncope episodes than women with no syncope during pregnancy.

Conclusions

Pregnant women with syncope, especially when the syncopal event occurs during the first trimester, may be at a higher risk of adverse pregnancy outcomes as well as an increased incidence of cardiac arrhythmia and syncope postpartum.

Metabolic Coordination of Physiological and Pathological Cardiac Remodeling

Metabolic pathways integrate to support tissue homeostasis and to prompt changes in cell phenotype. In particular, the heart consumes relatively large amounts of substrate not only to regenerate ATP for contraction but also to sustain biosynthetic reactions for replacement of cellular building blocks. Metabolic pathways also control intracellular redox state, and metabolic intermediates and end products provide signals that prompt changes in enzymatic activity and gene expression. Mounting evidence suggests that the changes in cardiac metabolism that occur during development, exercise, and pregnancy as well as with pathological stress (eg, myocardial infarction, pressure overload) are causative in cardiac remodeling. Metabolism-mediated changes in gene expression, metabolite signaling, and the channeling of glucose-derived carbon toward anabolic pathways seem critical for physiological growth of the heart, and metabolic inefficiency and loss of coordinated anabolic activity are emerging as proximal causes of pathological remodeling. This review integrates knowledge of different forms of cardiac remodeling to develop general models of how relationships between catabolic and anabolic glucose metabolism may fortify cardiac health or promote (mal)adaptive myocardial remodeling. Adoption of conceptual frameworks based in relational biology may enable further understanding of how metabolism regulates cardiac structure and function.

Sympathetic nervous system control of vascular function and blood pressure during pregnancy and preeclampsia

: Proper vascular tone and blood pressure regulation during pregnancy are important for immediate and long-term cardiovascular health of the mother and her offspring. Preeclampsia is clinically defined as new-onset maternal hypertension accompanied by cardiovascular, renal, and/or neural abnormalities presenting in the second half of pregnancy. There is strong evidence to support that preeclampsia is mediated by attenuations in uteroplacental vascular remodeling and increases in vasoconstriction with subsequent placental ischemia/reperfusion-induced release of hypertensive substances into the maternal circulation. These include antiangiogenic and pro-inflammatory factors. There is also evidence implicating increased sympathetic nervous system activity (SNA) in this maternal disorder, but this mostly includes data correlating severity of disease with catecholamine levels and elevated muscle SNA. These measurements have not confirmed a causative role for SNA in the pathogenesis of preeclampsia. Therefore, studies are needed to provide a comprehensive understanding of SNA and its control of vascular function and blood pressure regulation during normal pregnancy in order to set the stage for exploring the mechanisms mediating the exaggerated SNA and signaling during preeclampsia. This review examines the role of SNA in control of uteroplacental vascular tone and blood pressure regulation during normal pregnancy. Furthermore, it is proposed that over-activation of the SNA contributes to altered uteroplacental vascular tone and perfusion leading to placental ischemic events and modulates the systemic vasoconstriction and hypertensive responses to soluble placenta ischemic factors. Recognizing the integrative role and importance of SNA in the pathophysiology of preeclampsia will advance our understanding of this maternal disorder.

Cardiac Arrhythmias and Pregnancy

PURPOSE OF REVIEWS

In this review, the challenges of managing cardiac arrhythmias and syncope in the setting of pregnancy will be discussed.

RECENT FINDINGS

Arrhythmias in pregnancy are increasing, as diagnostic and therapeutic options have advanced and women are older at the time of gestation. Atrial fibrillation has become the most common arrhythmia in pregnancy. Inherited arrhythmia has become a more common entity, with advances in treatments and genetic testing, and require specialized treatments in pregnancy. The majority of arrhythmias in pregnancy are benign. The potential risk of increased cardiac morbidity and mortality exists for mother and fetus, especially in women with structural heart disease, which is becoming increasingly common. Early evaluation, diagnosis, and appropriate treatment are necessary to achieve optimal outcomes for both mother and fetus.

The effects of gender on electrical therapies for the heart: physiology, epidemiology, and access to therapies

The difference between men and women is clear even just by looking at an electrocardiogram: females present higher resting heart rate, a shorter QRS complex length and greater corrected QT interval. The development of these differences from pubertal age onward suggests that sexual hormones play a key role, although their effect is far from being completely understood. Different incidences between sexes have been reported for many arrhythmias, both ventricular and supraventricular, and also for sudden cardiac death. Moreover, arrhythmias are an important issue during pregnancy, both for diagnosis and treatment. Interestingly, cardiovascular structural and electrophysiological remodelling promoted by exercise training enhances this 'gender effect'. Despite all these relevant issues, we lack gender specific recommendations in the current guidelines for electrical therapies for heart rhythm disorders and heart failure. Even more, we continue to see that fewer women are included in clinical trials and are less referred than men for these treatments.

Hemodynamic and Electrocardiographic Aspects of Uncomplicated Singleton Pregnancy

Pregnancy is associated with significant changes in maternal hemodynamics, which are triggered by profound systemic vasodilation and mediated through the autonomic nervous system as well as the renin-angiotensin-aldosterone system. Vascular function changes to help accommodate an increase in intravascular volume due to blood volume expansion associated with pregnancy while maintaining the efficiency of ventricular-arterial coupling and diastolic perfusion pressure. The heart undergoes physiological (eccentric) hypertrophy due to increased volume load and cardiac stroke work, whereas the functional change of the left ventricle remains controversial. There are changes in cardiac electrical activity during pregnancy which can be detected in the electrocardiogram that are not related to disease. Sympathetic activation is a common phenomenon during uncomplicated pregnancy and may be a compensatory mechanism induced by profound systemic vasodilation and a decrease in mean arterial pressure. Despite marked sympathetic activation, vasoconstrictor responsiveness is blunted during uncomplicated pregnancy. There are race and ethnic differences in maternal hemodynamic adaptations to uncomplicated pregnancy, which may be attributed to differences in socioeconomic status or in prevalence rates of cardiovascular risk factors.

Pregnancy in a woman with a Fontan circulation: A review

More women with congenital heart disease survive to childbearing ages, due to improvements in surgical practice and postoperative care. This review discusses pregnancy in women with a single ventricle, describing maternal obstetric and cardiovascular complications and the increased risks of prematurity and adverse neonatal outcomes. Recommendations are made based on current understanding, guidelines and published literature, with recognition that there is much knowledge yet to be gained.