Sex-specific triggers for right ventricular outflow tract tachycardia

The 2024 US Medical Eligibility Criteria for Contraceptive Use: Application to Practice in the Care of Patients With Cardiac Disease

Cardiovascular disease is the leading cause of maternal mortality in the United States, with the majority of deaths stemming from preventable causes. Contraception is one of the tools that can be utilized to prevent mortality and morbidity associated with unplanned pregnancy in patients with underlying congenital or acquired heart disease. There are a wide range of contraceptive methods available. While some methods, especially those containing estrogen, may be associated with increased risks in certain cardiac disease states, intrauterine devices, implants, and progestin-only methods may be safely used by the vast majority of patients with cardiac disease. Furthermore, intrauterine devices and implants are the most effective reversible contraceptive methods available. This review provides a summary of the US Centers for Disease Control and Prevention 2024 Medical Eligibility Criteria for Contraceptive Use as it applies to cardiac disease states. This review emphasizes the importance of contraceptive counseling and aims to familiarize the reader with the various forms of contraception available to patients, as well as the risks and benefits of each method in patients with different types of cardiac disease.

Sex differences in the prognosis of nonsustained ventricular tachycardia detected on Holter recording

Background

Nonsustained ventricular tachycardia (NSVT) is a common finding during cardiac evaluation and has been linked to increased mortality. While some studies report a sex difference, most data stem from research cohorts.

Objective

This study aimed to assess the prognostic significance of NSVT in a real-life outpatient clinic, focusing on sex differences in mortality.

Methods

Analysis was performed on a cohort of consecutive patients referred to 48-hour Holter monitoring between 2009 and 2011 at Copenhagen University Hospital - Bispebjerg. Indications for Holter monitoring included palpitations, dizziness, syncope, or arrhythmia testing. Baseline characteristics, blood tests, echocardiography results, and mortality data were obtained from electronic patient records.

Results

A total of 762 females (mean age 59 ± 18 years) and 693 males (mean age 59 ± 17 years) were enrolled. At least 1 episode of NSVT was detected in 9.7% of females and 20.6% of males. The median follow-up was 8.3 years. A total of 20% of females and 24% of males died during follow-up. In multivariable models, NSVT was linked to mortality in males (hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.1-2.3) but not in females (HR 1.2, 95% CI 0.7-2.1). In case-control pairs matched on the propensity of being male conditional on relevant risk factors, NSVT was again linked to mortality in males (HR 3.1, 95% CI 2.0-4.8) but not in females (HR 1.4, 95% CI 0.8-2.4).

Conclusion

In consecutive patients referred to symptom driven Holter monitoring, NSVT was associated with elevated all-cause mortality in males but not in females. These results can contribute to the risk assessment of patients presenting with NSVT.

Sex Related Differences in Electrocardiography

Since its implementation into the clinical medicine by Willem Einthoven electrocardiography had become one of crucial diagnostic method in cardiology. In spite of this fact effects of gender differences on parameters of electrocardiographic recordings started to be studied only recently. Sex related differences in physiological ECG are only minimal in childhood but there are developing during adolescence reflecting rapidly evolving differences particularly in hormonal secretion and activity of an autonomic nervous system. The heart rate is approximately 7 % higher in women than in men, PQ and QRS intervals are longer in men while QT interval is longer in women. The ST segment in females is flatter but generally the sex-related differences in ST-T waveform patterns are relatively very small with higher level of ST segment and taller T wave in men. The effects of sex-related differences, including sex hormones, on cardiac cell injury and death and their influence in determining rhythmogenesis and action potential configuration and conduction play an important role in clinics. Women have a higher prevalence of sick sinus syndrome, inappropriate sinus tachycardia, atrioventricular nodal reentry tachycardia, idiopathic right ventricular tachycardia, and arrhythmic events in the long QT syndrome. In contrast, men have a higher prevalence of atrioventricular block, carotid sinus syndrome, atrial fibrillation, supraventricular tachycardia due to accessory pathways, Wolff-Parkinson-White syndrome, reentrant ventricular tachycardia, ventricular fibrillation and sudden death, and the Brugada syndrome.

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Idiopathic Ventricular Tachycardia

Idiopathic ventricular tachycardia (VT) is an important cause of morbidity and less commonly, mortality in patients with structurally normal hearts. Appropriate diagnosis and management are predicated on an understanding of the mechanism, relevant cardiac anatomy, and associated ECG signatures. Catheter ablation is a viable strategy to adequately treat and potentially provide a cure in patients that are intolerant to medications or when these are ineffective. In this review, we discuss special approaches and considerations for effective and safe ablation of VT arising from the right ventricular outflow tract, left ventricular outflow tract, left ventricular fascicles, papillary muscles, and moderator band.

Sex differences in heart: from basics to clinics

Sex differences exist in the structure and function of human heart. The patterns of ventricular repolarization in normal electrocardiograms (ECG) differ in men and women: men ECG pattern displays higher T-wave amplitude and increased ST angle. Generally, women have longer QT duration because of reduced repolarization reserve, and thus, women are more susceptible for the occurrence of torsades de pointes associated with drugs prolonging ventricular repolarization. Sex differences are also observed in the prevalence, penetrance and symptom severity, and also in the prognosis of cardiovascular disease. Generally, women live longer, have less clinical symptoms of cardiac diseases, and later onset of symptoms than men. Sex hormones also play an important role in regulating ventricular repolarization, suggesting that hormones directly influence various cellular functions and adrenergic regulation. From the clinical perspective, sex-based differences in heart physiology are widely recognized, but in daily practice, cardiac diseases are often underdiagnosed and untreated in the women. The underlying mechanisms of sex differences are, however, poorly understood. Here, we summarize sex-dependent differences in normal cardiac physiology, role of sex hormones, and differences in drug responses. Furthermore, we also discuss the importance of human induced pluripotent stem cell-derived cardiomyocytes in further understanding the mechanism of differences in women and men.

Arrhythmias in Female Patients: Incidence, Presentation and Management

There is a growing appreciation for differences in epidemiology, treatment, and outcomes of cardiovascular conditions by sex. Historically, cardiovascular clinical trials have under-represented females, but findings have nonetheless been applied to clinical care in a sex-agnostic manner. Thus, much of the collective knowledge about sex-specific cardiovascular outcomes result from post hoc and secondary analyses. In some cases, these investigations have revealed important sex-based differences with implications for optimizing care for female patients with arrhythmias. This review explores the available evidence related to cardiac arrhythmia care among females, with emphasis on areas in which important sex differences are known or suggested. Considerations related to improving female enrollment in clinical trials as a way to establish more robust clinical evidence for the treatment of females are discussed. Areas of remaining evidence gaps are provided, and recommendations for areas of future research and specific action items are suggested. The overarching goal is to improve appreciation for sex-based differences in cardiac arrhythmia care as 1 component of a comprehensive plan to optimize arrhythmia care for all patients.

Intramural Mapping of Intramural Septal Ventricular Arrhythmias

Background

Intramural ventricular arrhythmias (VAs) can originate in patients with or without structural heart disease. Electrogram (EGM) recordings from intramural sources of VA have not been described thoroughly.

Objective

We hypothesized that the presence of scar may be linked to the site of origin (SOO) of focal, intramural VAs.

Methods

In a series of 21 patients (age: 55 ± 11 years, 12 women, mean ejection fraction 43 ± 14%) in whom the SOO of intramural VAs was identified, we analyzed bipolar EGM characteristics at the SOO and compared the findings with the endocardial breakout site. The patients were from a pool of 86 patients with intramural VAs referred for ablation.

Results

In 16/21 patients intramural scarring was detected by cardiac magnetic resonance (CMR) imaging In patients in whom the intramural SOO was reached, intramural bipolar EGMs showed a lower voltage and had broader EGMs compared to the endocardial breakout sites (0.97 ± 0.56 vs. 2.28 ± 0.15 mV, p = .001; and 122.3 ± 31.6 vs. 96.5 ± 26.3 ms, p < .01). All intramural sampled sites at the SOO had either low voltage or broad abnormal EGMs. The activation time was significantly earlier at the intramural SOO than at breakout sites (−36.2 ± 11.8 vs. −23.2 ± 9.1 ms, p < .0001).

Conclusions

Sites of origin of intramural VAs with scar by CMR display EGM characteristics of scarring, supporting that scar tissue localizes to the SOO of intramural outflow tract arrhythmias in some patients. Scarring identified by CMR may be helpful in planning ablation procedures in patients with suspected intramural VAs.

Gender differences in patients with structural heart disease undergoing VT ablation

INTRODUCTION

This study sought to examine gender differences in patients with structural heart disease (SHD) referred for ablation of ventricular tachycardia (VT).

BACKGROUND

Female patients are often underrepresented in large studies. Significant differences in the clinical presentation, treatment, and prognosis of female patients have been described in previous studies.

METHODS AND RESULTS

We investigated 88 female patients with SHD undergoing VT ablation (mean age 59 years, 56% nonischemic cardiomyopathy, mean left ventricular ejection fraction 35%, 82% in electrical storm). A case-control study with 88 male patients was performed and the results regarding clinical and procedural characteristics, acute and long-term results of the two groups were compared. The female patients had more arrhythmogenic substrate, as they more commonly presented with electrical storm (p = .016) and had a higher number of inducible VT morphologies during the procedure (p = .018). Moreover, the female patients were less likely to have an optimized heart failure medical treatment at baseline (p = .030) and required more time from the first manifestation of the VT to ablation referral (p = .034). Although fewer epicardial ablations were performed in female patients (p = .019), the two groups showed similar results regarding VT noninducibility as ablation endpoint (p = .844), major procedure-related complications (p = .719) and freedom from VT during follow-up (p = .268). Moreover, the overall mortality in the two groups was similar (p = .176). Advanced NYHA class was associated with worse transplant and assist-device-free survival in the female group.

CONCLUSION

Female patients presenting for VT ablation had more arrhythmogenic substrate and were less likely to have an optimized heart failure medical treatment. Nevertheless, the procedural acute and long-term outcomes between the two genders were similar.

Management of tachyarrhythmias in pregnancy - A review

The most common arrhythmias detected during pregnancy include sinus tachycardia, sinus bradycardia, and sinus arrhythmia, identified in 0.1% of pregnancies. Isolated premature atrial or ventricular arrhythmias are observed in 0.03% of pregnancies. Arrhythmias may become more frequent during pregnancy or may manifest for the first time.

Idiopathic Outflow Tract Ventricular Arrhythmia Ablation: Pearls and Pitfalls

Idiopathic outflow tract ventricular arrhythmias (VAs) occur typically in patients without structural heart disease. They are often symptomatic and can sometimes lead to left ventricular systolic dysfunction. Both activation and pace mapping are utilised for successful ablation of these arrhythmias. Pace mapping is particularly helpful when the VA is infrequent and/or cannot be elucidated during the ablation procedure. VAs originating from different sites in the outflow tract region have distinct QRS patterns on the 12-lead ECG and careful analysis of the latter can help predict the site of origin of these arrhythmias. Successful ablation of these VAs requires understanding of the detailed anatomy of the OT region, which can be accomplished through electroanatomic mapping tools and intracardiac echocardiography.

Ventricular Arrhythmias in the Patient with a Structurally Normal Heart

Ventricular arrhythmias (VAs) are among the most common cardiac rhythm disturbances encountered in clinical practice. Patients presenting with frequent ventricular ectopy or sustained ventricular tachycardia represent a challenging and worrisome clinical scenario for many practitioners because of concerning symptoms, frequent associated acute hemodynamic compromise, and the adverse prognostic implications inherent to these cases. While an underlying structural or functional cardiac abnormality, metabolic derangement, or medication toxicity is often readily apparent, many patients have no obvious underlying condition, despite a comprehensive diagnostic evaluation. Such patients are diagnosed as having an idiopathic VA, which is a label with specific implications regarding arrhythmia origin, prognosis, and potential for pharmacologic and invasive management. Further, a subset of patients with otherwise benign idiopathic ventricular ectopy can present with polymorphic ventricular tachycardia and ventricular fibrillation, adding a layer of complexity to a clinical syndrome previously felt to have a benign clinical course. Thus, this review seeks to highlight the most common types of idiopathic VAs with a focus on their prognostic implications, underlying electrophysiologic mechanisms, unique electrocardiographic signatures, and considerations for invasive electrophysiologic study and catheter ablation. We further address some of the data regarding idiopathic ventricular fibrillation with respect to the heterogeneous nature of this diagnosis.

De Novo FGF12 (Fibroblast Growth Factor 12) Functional Variation Is Potentially Associated With Idiopathic Ventricular Tachycardia

Background

Idiopathic ventricular tachycardia (VT) is a type of cardiac arrhythmia occurring in structurally normal hearts. The heritability of idiopathic VT remains to be clarified, and numerous genetic factors responsible for development of idiopathic VT are as yet unclear. Variations in FGF12 (fibroblast growth factor 12), which is expressed in the human ventricle and modulates the cardiac Na⁺ channel Na_V1.5, may play an important role in the genetic pathogenesis of VT.

Methods and Results

We tested the hypothesis that genetic variations in FGF12 are associated with VT in 2 independent Chinese cohorts and resequenced all the exons and exon–intron boundaries and the 5′ and 3′ untranslated regions of FGF12 in 320 unrelated participants with idiopathic VT. For population‐based case–control association studies, we chose 3 single‐nucleotide polymorphisms—rs1460922, rs4687326, and rs2686464—which included all the exons of FGF12. The results showed that the single‐nucleotide polymorphism rs1460922 in FGF12 was significantly associated with VT after adjusting for covariates of sex and age in 2 independent Chinese populations: adjusted P=0.015 (odds ratio: 1.54 [95% CI, 1.09–2.19]) in the discovery sample, adjusted P=0.018 (odds ratio: 1.64 [95% CI, 1.09–2.48]) in the replication sample, and adjusted P=2.52E‐04 (odds ratio: 1.59 [95% CI, 1.24–2.03]) in the combined sample. After resequencing all amino acid coding regions and untranslated regions of FGF12, 5 rare variations were identified. The result of western blotting revealed that a de novo functional variation, p.P211Q (1.84% of 163 patients with right ventricular outflow tract VT), could downregulate FGF12 expression significantly.

Conclusions

In this study, we observed that rs1460922 of FGF12 was significantly associated with VT and identified that a de novo variation of FGF12 may be an important genetic risk factor for the pathogenesis of VT.

Incidence of Idiopathic Ventricular Arrhythmias: A Population-Based Study

BACKGROUND

Ventricular tachycardia and premature ventricular complexes (PVCs) most frequently occur in the context of structural heart disease. However, the burden of idiopathic ventricular arrhythmias (IVA) in the general population is unknown.

METHODS AND RESULTS

We identified incident cases of IVA between 2005 and 2013 from Olmsted County, Minnesota, using the Rochester Epidemiology Project database. For PVC cohorts, we included those with frequent (defined as ≥100 PVC/24 hours) symptomatic PVCs. We defined IVA-associated cardiomyopathy as a drop in ejection fraction of ≥10% from baseline. Between 2005 and 2013, we identified 614 individuals with incident IVA (229 [37.3%] were male; average age was 52.1±17.2 years). Of these, 177 (28.8%) had idiopathic ventricular tachycardia, 408 (66.5%) had symptomatic PVCs, and 29 (4.7%) had IVA-associated cardiomyopathy. The age- and sex-adjusted incidence rates in 2005 to 2007, 2008 to 2010, and 2011 to 2013 were 44.9 per 100 000 (95% confidence interval [CI], 38.0-51.8), 47.6 per 100 000 (95% CI, 40.8-54.5), and 62.0 per 100 000 (95% CI, 54.4-69.6), respectively. In idiopathic ventricular tachycardia, there was an increase in incidence rate with ages (P<0.001) but not between sexes (P=0.12). The age-adjusted incidence of symptomatic PVC was higher in females than in males (46.2 per 100 000 [95% CI, 40.9-51.6] versus 20.5 per 100 000 [95% CI, 16.8-24.3]; P<0.001). The small number of individuals with IVA-associated cardiomyopathy precluded any formal testing.

CONCLUSIONS

The incidence of IVA is increasing. Furthermore, overall incidence increases with age. Although the rate of idiopathic ventricular tachycardia is similar across sexes, women have a higher incidence of symptomatic PVC.

Mapping and ablation procedures for the treatment of ventricular tachycardia

INTRODUCTION

Ventricular tachycardia (VT) may occur in the presence or absence of structural heart disease. Given that the management of VT hinges on the presence of symptoms and risk of sudden cardiac death (SCD), the main treatment goals are elimination of symptoms (including frequent implantable cardioverter defibrillator [ICD] therapies) and prevention of SCD. Unfortunately, medical management is suboptimal in a significant proportion of patients. As such, ablative therapy plays a prominent role in the treatment of ventricular tachycardia.

AREAS COVERED

In this review, we will discuss various VT disorders that are encountered in patients with and without structural heart disease. Further, we will highlight salient features regarding mapping and ablation of the various VT syndromes. Finally, we will discuss what lies on the horizon for VT ablation. Expert commentary: Meticulous mapping should aim to find the region that is most likely to be successful and least likely to result in a complication. Although recognition of the various mechanisms of VT, familiarity with different methods to mapping and ablation, and awareness of potential limitations of current approaches is critical, a thorough understanding of the fundamental principles and nuances of each facet within EP is required to ensure optimal outcomes for our patients.

Impact of endo- and exogenous estrogens on heart rate variability in women: a review

Measurement of heart rate variability (HRV) is an established method to assess the activity of the autonomic nervous system. The aim of this review was to examine the link between HRV, reproductive life stages and menopausal hormone therapy. A literature review was performed using the Medline database. Based on title and abstract, 45 studies were extracted out of 261 citations screened. Due to different study designs and evaluation methods, HRV indices were not directly comparable. Qualitative comparisons in between the vast majority of studies, however, demonstrated a decrease of the vagal dominance on the heart from the follicular to the luteal cycle phase, although some studies asserted no change. The intake of oral contraceptives appeared not to alter the vagal modulation of the heart. All investigations agreed on a decline of HRV towards higher sympathetic control after menopause. Different menopausal hormone therapy approaches showed a supporting impact of estrogen on HRV in most studies. A combined therapy of estrogen and progestogens revoked this benefit. Further research is needed to demonstrate how this process might be attenuated by different menopausal hormone therapies.

Gender differences in electrophysiological characteristics of idiopathic ventricular tachycardia originating from right ventricular outflow tract

It has become increasingly apparent in recent years that there are important differences of many cardiovascular disorders including ventricular tachycardias in men and women. Nevertheless, so far just few studies have addressed possible gender differences in electrophysiological characteristics of idiopathic ventricular tachycardia from right ventricular outflow tract (RVOT-VT), other than epidemiological ones. This study explored possible gender differences in electrophysiological characteristics and catheter ablation outcome in RVOT-VT patients. Ninety-three patients (mean age 38.7+/-15.5 years, 30 males) with idiopathic RVOT-VT were enrolled and analyzed in our study. Male patients had longer QRS width (99.9+/-19.4 ms vs. 88.4+/-20.7 ms, p=0.02). Female patients had lower right ventricular mean voltage (3.0+/-0.7 mV vs. 3.7+/-0.9 mV, p=0.03), and more low voltage zone over the right ventricular outflow tract free wall (27.0 % vs. 6.7 %, p=0.02). Eighty-one patients passed catheter ablation (23 males). The acute success rate, repeated catheter ablation rate and VT recurrence rate were similar in both genders. The present study provides evidence of the gender differences in electrophysiological findings in patients with idiopathic RVOT-VT. Studies on gender-specific differences in arrhythmia could lead to a better understanding of its mechanism(s) and provide valuable information for the development of optimal treatment strategies.

Atypical Presentation of Right Ventricular Outflow Tract Ventricular Tachycardia

BACKGROUND

Ventricular tachycardia (VT) in the pediatric population is rare, has a wide differential diagnosis, and can present in numerous ways. In the absence of underlying heart disease, VT is considered idiopathic and is associated with an excellent prognosis. Right ventricular outflow tract ventricular tachycardia (RVOT-VT) represents the most common form of idiopathic VT. The differential diagnosis, mechanism, presentation, management, and prognosis of RVOT-VT in the pediatric population will be discussed.

CASE REPORT

We report a case of RVOT-VT that was incidentally discovered in an 11-year-old girl during an emergency department workup for severe headache. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: It is essential for emergency physicians to have an approach to pediatric VT and appreciate the wide range of potential presentations. Differentiating idiopathic VT, such as RVOT-VT, from more malignant forms of VT can be challenging and requires expert consultation for further diagnostic workup and management.

Infrequent intraprocedural premature ventricular complexes: implications for ablation outcome

BACKGROUND

Frequent premature ventricular complexes (PVCs) can be eliminated with an ablation procedure. Ablation success rates have been reported to be in the 80% range. Reasons for failure of ablation have not been described in detail. The purpose of this study was to determine whether the paucity of PVCs at the beginning of the ablation procedure affects the outcome.

METHODS

Catheter ablation was attempted in a consecutive series of 194 patients (age: 50 ± 14 years, 91 male, ejection fraction: 56.4 ± 8.4%) with frequent idiopathic PVCs. Based on receiver operator characteristics (ROC) analysis, patients were divided into 2 groups: Patients with frequent PVCs (≥32 PVCs within the first 30 minutes of the procedure: n = 135 [70%]); and patients with infrequent PVCs (<32 PVCs within the first 30 minutes of the procedure: n = 59 [30%]). Procedural outcomes were compared at 3 months postablation. A successful ablation was defined as a ≥80% reduction in the PVC burden compared to baseline.

RESULTS

A successful procedure was performed in 148 patients (76%) resulting in a decrease in the PVC burden from 19.1 ± 13.6% to 0.38 ± 0.98%(P < 0.0001). Patients with frequent intraprocedural PVCs had a higher success rate than patients with infrequent intraprocedural PVCs (85% vs. 56%, P = 0.0001). Administration of sedation was no different in the 2 groups. The paucity of PVCs was independent of the site of origin in predicting procedural failure (OR: 6.9, 95% CI: 3.0-16.2 P = 0.0001).

CONCLUSION

Paucity of PVCs at the beginning of an ablation procedure is associated with a lower ablation success rate independent of the site of origin.

Sex-Based Differences in Cardiac Arrhythmias, ICD Utilisation and Cardiac Resynchronisation Therapy

Many important differences in the presentation and clinical course of cardiac arrhythmias are present between men and women that should be accounted for in clinical practice. In this paper, we review published data on gender differences in cardiac excitable properties, supraventricular tachycardias, ventricular tachycardias, sudden cardiac death, and the utilisation of implantable defibrillators and cardiac resynchronisation therapy. Women have a higher heart rate at rest, and a longer QT interval than men. They further have a narrower QRS complex and lower QRS voltages on the 12-lead ECG with more often non-specific repolarisation abnormalities at rest. Supraventricular tachycardias, such as AV nodal reentrant tachycardia, are twice as frequent in women compared with men. Atrial fibrillation, however, has a 1.5-fold higher prevalence in men. The triggers for idiopathic right ventricular outflow tract tachycardia (VT) initiation are gender specific, i.e. hormonal changes play an important role in the occurrence of these VTs in women. There are clear-cut gender differences in acquired and congenital LQTS. Brugada syndrome affects men more commonly and severely than women. Sudden cardiac death is less prevalent in women at all ages and occurs 10 years later in women than in men. This may be related to the later onset of clinically manifest coronary heart disease in women. Among patients who receive ICDs and CRT devices, women appear to be under-represented, while they may benefit even more from these novel therapies.

Radiofrequency catheter ablation of idiopathic right ventricular outflow tract arrhythmias

Idiopathic ventricular arrhythmias (VA) consist of various subtypes of VA that occur in the absence of clinically apparent structural heart disease. Affected patients account for approximately 10% of all patients referred for evaluation of ventricular tachycardia (VT). Arrhythmias arising from the outflow tract (OT) are the most common subtype of idiopathic VA and more than 70-80% of idiopathic VTs or premature ventricular contractions (PVCs) originate from the right ventricular (RV) OT. Idiopathic OT arrhythmias are thought to be caused by adenosine-sensitive, cyclic adenosine monophosphate (cAMP) mediated triggered activity and, in general, manifest at a relatively early age. Usually they present as salvos of paroxysmal ventricular ectopic beats and are rarely life-threatening. When highly symptomatic and refractory to antiarrhythmic therapy or causative for ventricular dysfunction, ablation is a recommended treatment with a high success rate and a low risk of complications.

Caffeine and cardiac arrhythmias: a review of the evidence

Limited data exist on the safety and physiologic effects of caffeine in patients with known arrhythmias. The studies presented suggest that in most patients with known or suspected arrhythmia, caffeine in moderate doses is well tolerated and there is therefore no reason to restrict ingestion of caffeine. A review of the literature is presented.

Diverse modulating effects of estradiol and progesterone on the monophasic action potential duration in Langendorff-perfused female rabbit hearts

This study aimed to comparatively investigate the acute modulating effects of oestrogen and progesterone on the repolarization and the susceptibility of female rabbits to class III anti-arrhythmic agents. The acute influence of estradiol and progesterone on the cardiac repolarization and the drug sensitivity of the rapidly activating delayed rectifier K(+) channel to sotalol was comparatively studied in Langendorff-perfused rabbit hearts at pharmacological concentrations through recording of epicardial monophasic action potentials. In Langendorff-perfused rabbit hearts, estradiol (1-30 μm) concentration-dependently prolonged the monophasic action potential durations (MAPD(30) and MAPD(90) ) (P < 0.05); while the effects of progesterone on MAPD were biphasic: it prolonged MAPD(30) and MAPD(90) at lower concentrations (1-3 μm) but shortened MAPD(30) and MAPD(90) at higher concentrations (10-30 μm). Sotalol-induced prolongation of MAPD(90) was significantly less in the hearts pretreated with progesterone than those treated with estradiol (P < 0.05). The incidence of the pro-arrhythmic events induced by sotalol in the hearts pretreated with progesterone was also significantly lower than those pretreated with estradiol (P < 0.05). In conclusion, estradiol and progesterone have different modulating effects on cardiac repolarization: estradiol can concentration-dependently prolong the cardiac repolarization time and thus may reduce the repolarization reserve and increase the susceptibility of female rabbits to sotalol-induced arrhythmias, whereas progesterone may shorten the cardiac repolarization time at concentrations above 10 μm, thus protecting the heart from drug-induced arrhythmias.

Influence of the menstrual cycle on nonlinear properties of heart rate variability in young women

This study was designed to assess the changes in nonlinear properties of heart rate (HR) variability (HRV) during the menstrual cycle by means of complexity measures, including sample entropy (SampEn) and correlation dimension (CD), and explore probable physiological interpretations for them. In 16 healthy women (mean age: 23.8 +/- 2.7 yr), complexity measures along with the spectral components of HRV (sympathovagal markers) were analyzed over 1,500 R-R intervals recorded during both the follicular phase (day 11.9 +/- 1.4) and the luteal phase (day 22.0 +/- 1.4) of each woman's menstrual cycle. Simultaneously, serum ovarian hormone (estradiol-17 and progesterone) and thyroid-related hormone [free triiodothyronine, free thyroxine (T(4)), and thyroid-stimulating hormone] concentrations were measured. With regard to HRV measures, SampEn, CD, and high-frequency (HF) components decreased from the follicular phase to the luteal phase, whereas normalized low-frequency (LF) components and the LF-to-HF ratio as well as resting HR increased. In regard to hormone levels, whereas progesterone was increased, the other hormone concentrations were unchanged. Furthermore, across the menstrual cycle, both SampEn and CD were well correlated with the spectral indexes and free T(4) concentrations, and SampEn also showed significant correlations with the ratio of estradiol-17 to progesterone concentrations. These results suggest that the nonlinear properties in HRV are altered during the regular menstrual cycle and that the autonomic nervous system, ovarian hormone balance, and free T(4) may be involved in nonlinear HR control in healthy women. All of these factors may enrich the physiological meanings of complexity measures.

Management of ventricular tachycardia in the absence of structural heart disease

Ventricular tachycardia most often arises from the ventricular outflow tracts in patients with apparently structurally normal hearts, and is often termed idiopathic ventricular tachycardia. These tachycardias are characterized by a left bundle branch block, inferior axis QRS morphology, and a unique electropharmacologic profile. The choice of treatment is dictated by the severity of symptoms, and ranges from observation for asymptomatic patients, to antiarrhythmic agents for those who are mildly to moderately symptomatic (eg, palpitations), to catheter-based ablation for those with more troubling symptoms or those who develop tachycardia-mediated cardiomyopathy. Antiarrhythmic therapy can be effective for arrhythmia suppression, and radiofrequency ablation has a high success rate (> 90%) with few procedural complications. In general, ventricular outflow tract tachycardia has a favorable prognosis. Exclusion of arrhythmogenic right ventricular dysplasia/cardiomyopathy is important due to significant disparities in prognosis and treatment.

ECG clues for diagnosing ventricular tachycardia mechanism

Three mechanisms underlie the initiation and maintenance of ventricular tachycardia: automaticity, triggered activity, and reentry. As straightforward as these mechanisms are, assessing which mechanism is operative in a particular patient's ventricular tachycardia can be difficult. The optimal treatment strategy for ventricular tachycardia in a given patient can be influenced by the mechanism underlying the ventricular tachycardia. Appropriately counseling patients, choosing the optimal pharmacologic agent that maximizes efficacy while minimizing undesirable side effects, risks, and toxicities, as well as recommending and timing ablative therapy all hinge on identifying the probable mechanism of ventricular tachycardia. Much has been published regarding invasive electrophysiologic maneuvers that allow for correct diagnosis of ventricular tachycardia mechanism. The aim of this clinical review is to provide insight into VT mechanisms based on ECG clues of spontaneous arrhythmia events and the response to pharmacologic manipulation prior to invasive electrophysiologic evaluation.