Atrial Tachyarrhythmias and Stroke: Temporal Relationship and Stroke Subtypes.

BACKGROUND AND PURPOSE: Research into the temporal relationship between atrial tachyarrhythmias (atrial tachycardia [AT] and atrial fibrillation [AF]) and stroke has produced conflicting findings. Systematic categorization of stroke subtypes may help clarify the discussion. OBJECTIVES: The objective of the study was to examine the presence and timing of AT/AF in relation to ischemic stroke subtypes, categorized as either cardioembolic (CE) or non-CE. METHODS: Consecutive patients presenting to the Austin Hospital with acute stroke from 2012 to 2019 and a cardiac implantable electronic device (CIED) were identified. Using a case-control design, the temporal proximity of AT/AF episodes in the 90 days prior to stroke was compared in the CE and non-CE stroke groups. RESULTS: 5,591 patients presented to the Austin Hospital with acute stroke from 2012 to 2019, of whom 31 patients with an ischemic stroke and a CIED with ≥90 days of monitoring were identified. Twelve strokes were adjudicated as CE and 19 as non-CE by a stroke neurologist. Six of the 12 CE stroke patients (50%) experienced AT/AF within 30 days preceding their stroke, while none of the 19 non-CE stroke patients recorded any AT/AF in the same period (p = 0.001). Four CE stroke patients (33%) had no AT/AF preceding their strokes at any time. The odds ratio for CE stroke was highest (39; 95% confidence interval [CI]: 1.92-791.5) when AT/AF occurred in the 30 days prior, declining to 20.65 (95% CI: 1.00-427.66) and 6.07 (95% CI: 0.94-39.04) in the subsequent 31-60- and 61-90-day windows, respectively. CONCLUSIONS: CE strokes were associated with a significantly higher proportion of preceding AT/AF compared with non-CE strokes. These findings support a potential temporal relationship between AT/AF and CE stroke and demonstrate that stroke subtyping can better characterize the relationship between AF and ischemic stroke. However, this study's findings are limited by its sample size and small number of informative cases.

Sudden cardiac death related to physical exercise in the young: a nationwide cohort study of Australia.

BACKGROUND: Sudden cardiac death (SCD) during physical exercise is devastating. AIMS: To evaluate causes and circumstances of exercise-related SCD in the young in Australia. METHODS: We reviewed the National Coronial Information System database for deaths in Australia relating to cardiovascular disease in cases aged 10-35 years between 2000 and 2016. Cases who had undertaken physical exercise at the time of the event were included. We collected demographics, circumstances of death, type of physical exercise, bystander cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) use prior to ambulance arrival. RESULTS: Over a 17-year period, 1925 SCD cases were identified, of which 110 (6%) cases (median age 27 years (interquartile range 21-32 years); 92% male) were related to sports/physical exercise. Thirteen (12%) cases occurred in active athletes. Most common causes were coronary artery disease (CAD; 37%) and sudden arrhythmic death syndrome (SADS; 20%). Among Aboriginal and Torres Strait Islanders (n = 10), all deaths were related to CAD. Australian Rules Football (24%), running/jogging (14%) and soccer (14%) were the most frequent physical exercise activities. Prior symptoms were present in 39% (chest pain 37%, pre-syncope/syncope 26%). Most (87%) were witnessed, with bystander CPR in 70%. AED use prior to ambulance arrival was 8%. CONCLUSIONS: The present study demonstrates the high occurrence of CAD and SADS in SCD in the young related to physical exercise. Aboriginal and Torres Strait Islanders were disproportionately affected by CAD. Although events were commonly witnessed, AED was seldom used prior to ambulance arrival and highlights an important opportunity to improve outcomes in the post-arrest chain of survival.

Ventricular fibrillation episodes related to managed ventricular pacing algorithm in a patient with mitral valve prolapse - "Arrhythmic MVP due to MVP".

We report a case of an implant cardiac defibrillator (ICD) patient who an ICD implanted for ventricular fibrillation (VF) related to mitral valve prolapse. He has 2 episodes of VF in his device lives. First episode of VF in year 2016 was initiated after a pause related to the MVP™ algorithm with a critically timed PVC. MVP™ was turned off which prevented further VF episodes. However, MVP™ was turned back on at the device replacement in 2018. A second VF episode developed with similar mechanism in 2021 and MVP™ was subsequently turned off with no further VF recorded. This case highlights the importance of recognizing the mechanism of initiation of tachy-arrhythmia episodes and serves as an important reminder regarding optimization of device settings at the time of replacement.

Postoperative Atrial Fibrillation and Long-Term Risk of Stroke in Patients Undergoing Liver Transplantation.

BACKGROUND AND PURPOSE: Postoperative atrial fibrillation (POAF) is the commonest cardiovascular complication following liver transplantation (LT). This study sought to assess a possible association of POAF with subsequent thromboembolic events in patients undergoing LT. METHODS: A retrospective cohort study of consecutive adults undergoing LT between 2010 and 2018 was undertaken. Patients were classified as POAF if atrial fibrillation (AF) was documented within 30 days of LT without a prior history of AF. Cases of ischemic stroke or systemic embolism were adjudicated by a panel of 2 independent physicians. RESULTS: Among the 461 patients included, POAF occurred in 47 (10.2%) a median of 3 days following transplantation. Independent predictors of POAF included advancing age, postoperative sepsis and left atrial enlargement. Over a median follow-up of 4.9 (interquartile range, 2.9-7.2) years, 21 cases of stroke and systemic embolism occurred. Rates of thromboembolic events were significantly higher in patients with POAF (17.0% versus 3.1%; P<0.001). After adjustment, POAF remained a strong independent predictor of thromboembolic events (hazard ratio, 8.36 [95% CI, 2.34-29.79]). Increasing CHA2DS2VASc score was also an independent predictor of thromboembolic events (hazard ratio, 1.58 [95% CI, 1.02-2.46]). A model using POAF and a CHA2DS2VASc score ≥2 alone yielded a C statistic of 0.77, with appropriate calibration for the prediction of thromboembolic events. However, POAF was not an independent predictor of long-term mortality. CONCLUSIONS: POAF following LT is associated with an 8-fold increased risk of thromboembolic events and the use of the CHA2DS2VASc score may facilitate risk stratification of these patients. Prospective studies are warranted to assess whether the use of oral anticoagulants can reduce the risk of thromboembolism following LT.

Relationship between QT interval prolongation and structural abnormalities in cirrhotic cardiomyopathy: A change in the current paradigm.

It is postulated that cardiac structural abnormalities observed in cirrhotic cardiomyopathy (CCM) contribute to the electrophysiologic abnormality of QT interval (QTc) prolongation. We sought to evaluate whether QTc prolongation is associated with intrinsic abnormalities in cardiac structure and function that characterize CCM. Consecutive patients undergoing liver transplant work-up between 2010 and 2018 were included. Measures of cardiac function on stress testing including cardiac reserve and chronotropic incompetence were collected prospectively and a corrected QTc ≥ 440 ms was considered prolonged. Overall, 439 patients were included and 65.1% had a prolonged QTc. There were no differences in markers of left ventricular and atrial remodeling, or resting systolic and diastolic function across QTc groups. The proportion of patients that met the criteria for a low cardiac reserve (39.2 vs 36.6%, p = .66) or chronotropic incompetence (18.1 vs 21.3%, p = .52) was not different in those with a QTc ≥ 440 vs <440 ms. Further, there was no association between QTc prolongation and CCM by either the 2005 World College of Gastroenterology or modified 2020 Cirrhotic Cardiomyopathy Consortium criteria. QT interval prolongation was not associated with structural or functional cardiac abnormalities that characterize CCM. These findings suggest that CCM and QT interval prolongation in cirrhosis may be two separate entities with distinct pathophysiological origins.

Effect of QT interval prolongation on cardiac arrest following liver transplantation and derivation of a risk index.

Liver transplantation (LT) has a 4-fold higher risk of periprocedural cardiac arrest and ventricular arrhythmias (CA/VAs) compared with other noncardiac surgeries. Prolongation of the corrected QT interval (QTc) is common in patients with liver cirrhosis. Whether it is associated with an increased risk of CA/VAs following LT is unclear. Rates of 30-day CA/VAs post-LT were assessed in consecutive adults undergoing LT between 2010 and 2017. Pretransplant QTc was measured by a cardiologist blinded to clinical outcomes. Among 408 patients included, CA/VAs occurred in 26 patients (6.4%). QTc was significantly longer in CA/VA patients (475 ± 34 vs 450 ± 34 ms, P < .001). Optimal QTc cut-off for prediction of CA/VAs was ≥480 ms. After adjustment, QTc ≥480 ms remained the strongest predictor for the occurrence of CA/VAs (odds ratio [OR] 5.2, 95% confidence interval [CI] 2.2-12.6). A point-based cardiac arrest risk index (CARI) was derived with the bootstrap method for yielding optimism-corrected coefficients (2 points: QTc ≥480, 1 point: Model for End-Stage Liver Disease [MELD] ≥30, 1 point: age ≥65, and 1 point: male). CARI score ≥3 demonstrated moderate discrimination (c-statistic 0.79, optimism-corrected c-statistic 0.77) with appropriate calibration. QTc ≥480 ms was associated with a 5-fold increase in the risk of CA/VAs. The CARI score may identify patients at higher risk of these events. Whether heightened perioperative cardiac surveillance, avoidance of QT prolonging medications, or beta blockers could mitigate the risk of CA/VAs in this population merits further study.

Epidemiology of cardiac implantable electronic device infections: incidence and risk factors.

Cardiac implantable electronic device (CIED) infection is a potentially devastating complication of CIED procedures, causing significant morbidity and mortality for patients. Of all CIED complications, infection has the greatest impact on mortality, requirement for re-intervention and additional hospital treatment days. Based on large prospective studies, the infection rate at 12-months after a CIED procedure is approximately 1%. The risk of CIED infection may be related to several factors which should be considered with regards to risk minimization. These include technical factors, patient factors, and periprocedural factors. Technical factors include the number of leads and size of generator, the absolute number of interventions which have been performed for the patient, and the operative approach. Patient factors include various non-modifiable underlying comorbidities and potentially modifiable transient conditions. Procedural factors include both peri-operative and post-operative factors. The contemporary PADIT score, derived from a large cohort of CIED patients, is useful for the prediction of infection risk. In this review, we summarize the key information regarding epidemiology, incidence and risk factors for CIED infection.

Impaired Cardiac Reserve on Dobutamine Stress Echocardiography Predicts the Development of Hepatorenal Syndrome.

OBJECTIVES: Cardiac dysfunction has been implicated in the genesis of hepatorenal syndrome (HRS). It is unclear whether a low cardiac output (CO) or attenuated contractile response to hemodynamic stress can predict its occurrence. We studied cardiovascular hemodynamics in cirrhosis and assessed whether a diminished cardiac reserve with stress testing predicted the development of HRS on follow-up. METHODS: Consecutive patients undergoing liver transplant workup with dobutamine stress echocardiography (DSE) were included. CO was measured at baseline and during low-dose dobutamine infusion at 10 µg/kg/min. HRS was diagnosed using guideline-based criteria. RESULTS: A total of 560 patients underwent DSE, of whom 488 were included after preliminary assessment. There were 64 (13.1%) patients with established HRS. The HRS cohort had a higher baseline CO (8.0 ± 2 vs 6.9 ± 2 L/min; P < 0.001) and demonstrated a blunted response to low-dose dobutamine (ΔCO 29 ± 22% vs 44 ± 32%, P < 0.001) driven primarily by inotropic incompetence. Optimal cutpoint for ΔCO in patients with HRS was determined to be <25% and was used to define a low cardiac reserve. Among the 424 patients without HRS initially, 94 (22.1%) developed HRS over a mean follow-up of 1.5 years. Higher proportion with a low cardiac reserve developed HRS (52 [55.0%] vs 56 [16.9%]; hazard ratio 4.5; 95% confidence interval 3.0-6.7; P < 0.001). In a Cox multivariable model, low cardiac reserve remained the strongest predictor for the development of HRS (hazard ratio 3.9; 95% confidence interval 2.2-7.0; P < 0.001). DISCUSSION: Patients with HRS demonstrated a higher resting CO and an attenuated cardiac reserve on stress testing. On longitudinal follow-up, low cardiac reserve was an independent predictor for the development of HRS. Assessment of cardiac reserve with DSE may provide a novel noninvasive risk marker for developing HRS in patients with advanced liver disease.HRS is a life-threatening complication of liver disease. We studied whether an inability to increase cardiac contraction in response to stress can assist in the prediction of HRS. We demonstrate that patients with liver disease who exhibit cardiac dysfunction during stress testing had a 4-fold increased risk of developing HRS. This may improve our ability for early diagnosis and treatment of patients at a higher risk of developing HRS.

Prevalence and prevention of oesophageal injury during atrial fibrillation ablation: a systematic review and meta-analysis.

AIMS: Atrio-oesophageal fistula (AOF) is a potentially lethal complication of atrial fibrillation (AF) ablation. Many studies have evaluated the presence and prevention of endoscopically-detected oesophageal lesions (EDOL) as a proxy measure for risk of AOF. This systematic review and meta-analysis sought to determine the prevalence of EDOL and effectiveness of general preventive measures during AF ablation. METHODS AND RESULTS: We searched electronic databases for studies reporting prevalence or prevention of EDOL post-AF ablation. Pooled prevalence were reported with 95% confidence intervals (CI) while studies evaluating preventive measures including oesophageal temperature monitoring (OTM), esophageal manipulation and type of anaesthesia were analyzed descriptively or by random-effects modeling. Twenty-five studies were included in the analysis. Any and ulcerated EDOL pooled prevalence was 11% (95%CI, 6-15%) and 5% (95%CI, 3-7%), respectively. In six studies, there was no difference in EDOL with or without OTM (pooled OR 1.65, 95%CI, 0.22-12.55). There was no difference using a multi-sensor versus single-sensor OTM (one study) nor when using a deflectable probe (two studies). Oesophageal displacement was associated with significant instrumentation injury in one study. Two studies evaluating Oesophageal cooling showed conflicting results. General anaesthesia was associated with more EDOL than conscious sedation in two studies. CONCLUSION: The pooled prevalence of any and ulcerated EDOL post-ablation was 11% and 5%, but varied between studies. Techniques such as OTM and oesophageal displacement or cooling have not conclusively demonstrated a reduction in EDEL, while general anaesthesia may be associated with higher EDOL risk. Further randomized data are critically needed to validate and develop measures to prevent EDOL and AOF.

Predictors of ManuScript Rejection sYndrome (MiSeRY): a cohort study.

OBJECTIVES: To assess whether specific factors predict the development of ManuScript Rejection sYndrome (MiSeRY) in academic physicians. DESIGN: Prospective pilot study; participants self-administered a questionnaire about full manuscript submissions (as first or senior author) rejected at least once during the past 5 years. SETTING: Single centre (tertiary institution). PARTICIPANTS: Eight academic physician-authors. MAIN OUTCOME MEASURES: Duration of grief. MiSeRY was pre-specified as prolonged grief (grief duration longer than the population median). RESULTS: Eight participants provided data on 32 manuscripts with a total of 93 rejections (median, two rejections per manuscript; interquartile range [IQR], 1-3 rejections per manuscript). Median age at rejection was 37 years (IQR, 33-45 years); 86% of 80 rejections involved male authors (86%), 56 of the authors providing data about these rejections were first authors (60%). The median journal impact factor was 5.9 (IQR, 5.2-17). In 48 cases of rejection (52%), pre-submission expectations of success had been high, and in 54 cases (58%) the manuscripts had been sent for external review. Median grief duration was 3 hours (IQR, 1-24 h). Multivariate analysis indicated that higher pre-submission expectation (adjusted odds ratio [aOR], 5.0; 95% CI, 1.5-18), first author status (aOR, 9.5; 95% CI, 1.1-77), and external review (aOR, 19.0; 95% CI 2.9-126) were independent predictors of MiSeRY. CONCLUSIONS: To help put authors out of their MiSeRY, journal editors could be more selective in the manuscripts they send for external review. Tempering pre-submission expectations and mastering the Coping and reLaxing Mechanisms (CaLM) of senior colleagues are important considerations for junior researchers.

Challenges and limitations in the diagnosis of atrioesophageal fistula.

INTRODUCTION: Atrioesophageal fistula (AEF) is a dire complication of atrial fibrillation ablation. The diagnostic yield of computed tomography (CT) chest, the role and timing of repeat testing, and the value of other investigations in the diagnosis of AEF is uncertain. METHODS: We systematically reviewed published AEF cases to evaluate radiological, bedside, and biochemical investigations for AEF (registered on PROSPERO [CRD42017077493]). RESULTS: Eighty-seven articles with 126 patients (median age, 59 years; male, 71%) were included in the analysis. CT chest was performed in 88% (111/126) and was abnormal in 87%. A clear diagnosis of AEF (fistula/perforation) was only detected in 35% (34/97). Other major findings included free air in mediastinum (26%), left atrium (LA), or LA wall (24%). In 11 patients with normal/nonspecific initial CT chest, major abnormalities were detected in 91% (10/11) of repeat CT chest performed 6 days (median; range, 4-22) after initial scan. Initial CT head was normal in 51%; diffuse air emboli was identified in 79% (22/28). Initial transthoracic echocardiography was normal in 61% of cases. The spectrum of radiological abnormalities included Air (mediastinum/LA), Effusion (pleural/pericardial), Fistula/Perforation, and Thickening (esophagus/LA) - "AEF-Tests." Esophagram demonstrated contrast extravasation in 87% (13/15). Blood culture was consistently positive (100%; 28/28), particularly for streptococcus species (93%; 26/28). CONCLUSION: The diagnosis of AEF remains challenging. Clinicians should be aware of the limitations in the yield of CT chest, the variety of major abnormalities reported, the need for repeat testing, unique brain imaging findings, and the importance of positive blood cultures and raised inflammatory markers.

Provocation testing in congenital long QT syndrome: A practical guide.

Congenital long QT syndrome (LQTS) is a hereditary cardiac channelopathy with an estimated prevalence of 1 in 2500. A prolonged resting QT interval corrected for heart rate (QTc interval) remains a key diagnostic component; however, the QTc value may be normal in up to 40% of patients with genotype-positive LQTS and borderline in a further 30%. Provocation of QTc prolongation and T-wave changes may be pivotal to unmasking the diagnosis and useful in predicting genotype. LQTS provocation testing involves assessment of repolarization during and after exercise, in response to changes in heart rate or autonomic tone, with patients with LQTS exhibiting a maladaptive repolarization response. We review the utility and strengths and limitations of 4 forms of provocation testing-stand-up test, exercise stress test, epinephrine challenge, and mental stress test-in diagnosing LQTS and provide some practical guidance for performing provocation testing. Ultimately, exercise testing, when feasible, is the most useful form of provocation testing when considering diagnostic sensitivity and specificity.

Commotio Cordis in Non-Sport-Related Events: A Systematic Review.

BACKGROUND: Commotio cordis is an increasingly recognized cause of sudden cardiac death. Although commonly linked with athletes, many events occur in non-sport-related settings. OBJECTIVES: The goal of this study was to characterize and compare non-sport-related vs sport-related commotio cordis. METHODS: PubMed and Embase were searched for all cases of commotio cordis from inception to January 5, 2022. RESULTS: Of 334 commotio cordis cases identified, 121 (36%) occurred in non-sport-related contexts, which included assault (76%), motor vehicle accidents (7%), and daily activities (16%). Projectiles were implicated significantly less in non-sport-related events (5% vs 94%, respectively; P < 0.001). Nonprojectile etiologies in non-sport-related events mostly consisted of impacts with body parts (79%). Both categories affected similar younger aged demographic (P = 0.10). The proportion of female victims was significantly higher in non-sport-related events (13% vs 2%, respectively; P = 0.025). Mortality was significantly higher in non-sport-related events (88% vs 66%, respectively; P < 0.001). In non-sport-related events, rates of cardiopulmonary resuscitation (27% vs 97%, respectively; P < 0.001) and defibrillation (17% vs 81%, respectively; P < 0.001) were both lower and resuscitation was more commonly delayed beyond 3 min (80% vs 5%, respectively; P < 0.001). CONCLUSIONS: Commotio cordis occurs across a spectrum of non-sport-related settings including assault, motor vehicle accidents, and daily activities. Both categories affected a younger and male-predominant demographic. Mortality is higher in non-sport-related commotio cordis, likely owing to lower rates of cardiopulmonary resuscitation, defibrillation, automated external defibrillator availability, and extended time to resuscitation. Increased awareness of non-sport-related commotio cordis is essential to develop a means of prevention and mortality reduction, with earlier recognition and prompt resuscitation measures.

Association of the Timing and Extent of Cardiac Implantable Electronic Device Infections With Mortality.

Importance: Cardiac implantable electronic device (CIED) infection is a potentially devastating complication with an estimated 12-month mortality of 15% to 30%. The association of the extent (localized or systemic) and timing of infection with all-cause mortality has not been established. Objective: To evaluate the association of the extent and timing of CIED infection with all-cause mortality. Design, Setting, and Participants: This prospective observational cohort study was conducted between December 1, 2012, and September 30, 2016, in 28 centers across Canada and the Netherlands. The study included 19 559 patients undergoing CIED procedures, 177 of whom developed an infection. Data were analyzed from April 5, 2021, to January 14, 2023. Exposures: Prospectively identified CIED infections. Main Outcomes and Measures: Time-dependent analysis of the timing (early [≤3 months] or delayed [3-12 months]) and extent (localized or systemic) of infection was performed to determine the risk of all-cause mortality associated with CIED infections. Results: Of 19 559 patients undergoing CIED procedures, 177 developed a CIED infection. The mean (SD) age was 68.7 (12.7) years, and 132 patients were male (74.6%). The cumulative incidence of infection was 0.6%, 0.7%, and 0.9% within 3, 6, and 12 months, respectively. Infection rates were highest in the first 3 months (0.21% per month), reducing significantly thereafter. Compared with patients who did not develop CIED infection, those with early localized infections were not at higher risk for all-cause mortality (no deaths at 30 days [0 of 74 patients]: adjusted hazard ratio [aHR], 0.64 [95% CI, 0.20-1.98]; P = .43). However, patients with early systemic and delayed localized infections had an approximately 3-fold increase in mortality (8.9% 30-day mortality [4 of 45 patients]: aHR, 2.88 [95% CI, 1.48-5.61]; P = .002; 8.8% 30-day mortality [3 of 34 patients]: aHR, 3.57 [95% CI, 1.33-9.57]; P = .01), increasing to a 9.3-fold risk of death for those with delayed systemic infections (21.7% 30-day mortality [5 of 23 patients]: aHR, 9.30 [95% CI, 3.82-22.65]; P < .001). Conclusions and Relevance: Findings suggest that CIED infections are most common within 3 months after the procedure. Early systemic infections and delayed localized infections are associated with increased mortality, with the highest risk for patients with delayed systemic infections. Early detection and treatment of CIED infections may be important in reducing mortality associated with this complication.

Latent Causes of Sudden Cardiac Arrest.

Inherited arrhythmia syndromes are a common cause of apparently unexplained cardiac arrest or sudden cardiac death. These include long QT syndrome and Brugada syndrome, with a well-recognized phenotype in most patients with sufficiently severe disease to lead to cardiac arrest. Less common and typically less apparent conditions that may not be readily evident include catecholaminergic polymorphic ventricular tachycardia, short QT syndrome and early repolarization syndrome. In cardiac arrest patients whose extensive testing does not reveal an underlying etiology, a diagnosis of idiopathic ventricular fibrillation or short-coupled ventricular fibrillation is assigned. This review summarizes our current understanding of the less common inherited arrhythmia syndromes and provides clinicians with a practical approach to diagnosis and management.

Brugada Syndrome.

Brugada syndrome (BrS) is an "inherited" condition characterized by predisposition to syncope and cardiac arrest, predominantly during sleep. The prevalence is ∼1:2,000, and is more commonly diagnosed in young to middle-aged males, although patient sex does not appear to impact prognosis. Despite the perception of BrS being an inherited arrhythmia syndrome, most cases are not associated with a single causative gene variant. Electrocardiogram (ECG) findings support variable extent of depolarization and repolarization changes, with coved ST-segment elevation ≥2 mm and a negative T-wave in the right precordial leads. These ECG changes are often intermittent, and may be provoked by fever or sodium channel blocker challenge. Growing evidence from cardiac imaging, epicardial ablation, and pathology studies suggests the presence of an epicardial arrhythmic substrate within the right ventricular outflow tract. Risk stratification aims to identify those who are at increased risk of sudden cardiac death, with well-established factors being the presence of spontaneous ECG changes and a history of cardiac arrest or cardiogenic syncope. Current management involves conservative measures in asymptomatic patients, including fever management and drug avoidance. Symptomatic patients typically undergo implantable cardioverter defibrillator insertion, with quinidine and epicardial ablation used for patients with recurrent arrhythmia. This review summarizes our current understanding of BrS and provides clinicians with a practical approach to diagnosis and management.

Congenital Long QT Syndrome.

Congenital long QT syndrome (LQTS) encompasses a group of heritable conditions that are associated with cardiac repolarization dysfunction. Since its initial description in 1957, our understanding of LQTS has increased dramatically. The prevalence of LQTS is estimated to be ∼1:2,000, with a slight female predominance. The diagnosis of LQTS is based on clinical, electrocardiogram, and genetic factors. Risk stratification of patients with LQTS aims to identify those who are at increased risk of cardiac arrest or sudden cardiac death. Factors including age, sex, QTc interval, and genetic background all contribute to current risk stratification paradigms. The management of LQTS involves conservative measures such as the avoidance of QT-prolonging drugs, pharmacologic measures with nonselective ß-blockers, and interventional approaches such as device therapy or left cardiac sympathetic denervation. In general, most forms of exercise are considered safe in adequately treated patients, and implantable cardioverter-defibrillator therapy is reserved for those at the highest risk. This review summarizes our current understanding of LQTS and provides clinicians with a practical approach to diagnosis and management.

Arrhythmogenic Right Ventricular Cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) encompasses a group of conditions characterized by right ventricular fibrofatty infiltration, with a predominant arrhythmic presentation. First described in the late 1970s and early 1980s, it is now frequently recognized to have biventricular involvement. The prevalence is ∼1:2,000 to 1:5,000, depending on geographic location, and it has a slight male predominance. The diagnosis of ARVC is determined on the basis of fulfillment of task force criteria incorporating electrophysiological parameters, cardiac imaging findings, genetic factors, and histopathologic features. Risk stratification of patients with ARVC aims to identify those who are at increased risk of sudden cardiac death or sustained ventricular tachycardia. Factors including age, sex, electrophysiological features, and cardiac imaging investigations all contribute to risk stratification. The current management of ARVC includes exercise restriction, ß-blocker therapy, consideration for implantable cardioverter-defibrillator insertion, and catheter ablation. This review summarizes our current understanding of ARVC and provides clinicians with a practical approach to diagnosis and management.

Sex Differences and Utility of Treadmill Testing in Long-QT Syndrome.

Background Diagnosis of congenital long-QT syndrome (LQTS) is complicated by phenotypic ambiguity, with a frequent normal-to-borderline resting QT interval. A 3-step algorithm based on exercise response of the corrected QT interval (QTc) was previously developed to diagnose patients with LQTS and predict subtype. This study evaluated the 3-step algorithm in a population that is more representative of the general population with LQTS with milder phenotypes and establishes sex-specific cutoffs beyond the resting QTc. Methods and Results We identified 208 LQTS likely pathogenic or pathogenic KCNQ1 or KCNH2 variant carriers in the Canadian NLQTS (National Long-QT Syndrome) Registry and 215 unaffected controls from the HiRO (Hearts in Rhythm Organization) Registry. Exercise treadmill tests were analyzed across the 5 stages of the Bruce protocol. The predictive value of exercise ECG characteristics was analyzed using receiver operating characteristic curve analysis to identify optimal cutoff values. A total of 78% of male carriers and 74% of female carriers had a resting QTc value in the normal-to-borderline range. The 4-minute recovery QTc demonstrated the best predictive value for carrier status in both sexes, with better LQTS ascertainment in female patients (area under the curve, 0.90 versus 0.82), with greater sensitivity and specificity. The optimal cutoff value for the 4-minute recovery period was 440 milliseconds for male patients and 450 milliseconds for female patients. The 1-minute recovery QTc had the best predictive value in female patients for differentiating LQTS1 versus LQTS2 (area under the curve, 0.82), and the peak exercise QTc had a marginally better predictive value in male patients for subtype with (area under the curve, 0.71). The optimal cutoff value for the 1-minute recovery period was 435 milliseconds for male patients and 455 milliseconds for femal patients. Conclusions The 3-step QT exercise algorithm is a valid tool for the diagnosis of LQTS in a general population with more frequent ambiguity in phenotype. The algorithm is a simple and reliable method for the identification and prediction of the 2 major genotypes of LQTS.