Christian van der Werf

Flecainide therapy reduces exercise-induced ventricular arrhythmias in patients with catecholaminergic polymorphic ventricular tachycardia

OBJECTIVES This study evaluated the efficacy and safety of flecainide in addition to conventional drug therapy in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). BACKGROUND CPVT is an inherited arrhythmia syndrome caused by gene mutations that destabilize cardiac ryanodine receptor Ca(2+) release channels. Sudden cardiac death is incompletely prevented by conventional drug therapy with β-blockers with or without Ca(2+) channel blockers. The antiarrhythmic agent flecainide directly targets the molecular defect in CPVT by inhibiting premature Ca(2+) release and triggered beats in vitro. METHODS We collected data from every consecutive genotype-positive CPVT patient started on flecainide at 8 international centers before December 2009. The primary outcome measure was the reduction of ventricular arrhythmias during exercise testing. RESULTS Thirty-three patients received flecainide because of exercise-induced ventricular arrhythmias despite conventional (for different reasons, not always optimal) therapy (median age 25 years; range 7 to 68 years; 73% female). Exercise tests comparing flecainide in addition to conventional therapy with conventional therapy alone were available for 29 patients. Twenty-two patients (76%) had either partial (n = 8) or complete (n = 14) suppression of exercise-induced ventricular arrhythmias with flecainide (p < 0.001). No patient experienced worsening of exercise-induced ventricular arrhythmias. The median daily flecainide dose in responders was 150 mg (range 100 to 300 mg). During a median follow-up of 20 months (range 12 to 40 months), 1 patient experienced implantable cardioverter-defibrillator shocks for polymorphic ventricular arrhythmias, which were associated with a low serum flecainide level. In 1 patient, flecainide successfully suppressed exercise-induced ventricular arrhythmias for 29 years. CONCLUSIONS Flecainide reduced exercise-induced ventricular arrhythmias in patients with CPVT not controlled by conventional drug therapy.

Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy Pathogenic Desmosome Mutations in Index-Patients Predict Outcome of Family Screening: Dutch Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy Genotype-Phenotype Follow-Up Study

Background— Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an autosomal dominant inherited disease with incomplete penetrance and variable expression. Causative mutations in genes encoding 5 desmosomal proteins are found in ≈50% of ARVD/C index patients. Previous genotype-phenotype relation studies involved mainly overt ARVD/C index patients, so follow-up data on relatives are scarce. Methods and Results— One hundred forty-nine ARVD/C index patients (111 male patients; age, 49±13 years) according to 2010 Task Force criteria and 302 relatives from 93 families (282 asymptomatic; 135 male patients; age, 44±13 years) were clinically and genetically characterized. DNA analysis comprised sequencing of plakophilin-2 ( PKP2 ), desmocollin-2, desmoglein-2, desmoplakin, and plakoglobin and multiplex ligation-dependent probe amplification to identify large deletions in PKP2. Pathogenic mutations were found in 87 index patients (58%), mainly truncating PKP2 mutations, including 3 cases with multiple mutations. Multiplex ligation-dependent probe amplification revealed 3 PKP2 exon deletions. ARVD/C was diagnosed in 31% of initially asymptomatic mutation-carrying relatives and 5% of initially asymptomatic relatives of index patients without mutation. Prolonged terminal activation duration was observed more than negative T waves in V1 to V3, especially in mutation-carrying relatives <20 years of age. In 45% of screened families, ≥1 affected relatives were identified (90% with mutations). Conclusions— Pathogenic desmosomal gene mutations, mainly truncating PKP2 mutations, underlie ARVD/C in the majority (58%) of Dutch index patients and even 90% of familial cases. Additional multiplex ligation-dependent probe amplification analysis contributed to discovering pathogenic mutations underlying ARVD/C. Discovering pathogenic mutations in index patients enables those relatives who have a 6-fold increased risk of ARVD/C diagnosis to be identified. Prolonged terminal activation duration seems to be a first sign of ARVD/C in young asymptomatic relatives. # Clinical Perspective {#article-title-38}

Therapeutic approach for patients with catecholaminergic polymorphic ventricular tachycardia: state of the art and future developments

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome characterized by bidirectional or polymorphic ventricular arrhythmias under conditions of increased sympathetic activity in young patients with structurally normal hearts. Patients with CPVT are at high risk of developing life-threatening ventricular arrhythmias when untreated. A wide variety of arrhythmic event rates on conventional therapy, with β-blockers as the cornerstone, has been reported. Here, we systematically review all available studies describing the efficacy of β-blocker therapy for prevention of arrhythmic events in CPVT. Because of heterogeneity between the studies, a random-effects meta-analysis model was used to assess the efficacy of β-blocker therapy in preventing any arrhythmic event [syncope, aborted cardiac arrest (ACA), and sudden cardiac death (SCD)], near-fatal arrhythmic events (ACA and SCD), and fatal arrhythmic events. Eleven studies including 403 patients, of whom 354 (88%) had a β-blocker prescribed, were identified. Mean follow-up ranged from 20 months to 8 years. Estimated 8-year arrhythmic, near-fatal, and fatal event rates were 37.2% [95% confidence interval (CI): 16.6-57.7], 15.3% (95% CI: 7.4-23.3), and 6.4% (95% CI: 3.2-9.6), respectively. In addition, we review the recent developments in alternate chronic treatment options for CPVT patients, including calcium channel blockers, flecainide, left cardiac sympathetic denervation, and implantable cardioverter defibrillators. A new treatment strategy is proposed, including a stepwise addition of the alternate treatment options to β-blockers in patients who do not respond sufficiently to this first-line therapy. Finally, future developments in chronic treatment options and acute treatment options of ventricular arrhythmias are discussed.

Diagnostic yield in sudden unexplained death and aborted cardiac arrest in the young: the experience of a tertiary referral center in The Netherlands.

BACKGROUND In sudden unexplained death (SUD) in the young (age 1-50 years), cardiologic and genetic examination in surviving relatives may unmask the cause of death in a significant proportion. The causes of aborted cardiac arrest (ACA) in this age group likely are similar to those in sudden cardiac death. However, there is a paucity of recent data on this topic. OBJECTIVE The purpose of this study was to gain insight into the yield of current diagnostic strategies used in relatives of SUD victims and in ACA victims aged 1-50 years in our dedicated tertiary referral center. METHODS We studied (1) all consecutive families who presented to the cardiology department for examination because of ≥1 first-degree related SUD victim aged 1-50 years and (2) all consecutive ACA victims aged 1-50 years who presented to the cardiology department from 1996 to 2009. Comprehensive cardiologic and genetic examination was performed in both populations. RESULTS A certain or probable diagnosis was made in 47 (33%) of 140 SUD families, including 45 (96%) cases of inherited cardiac diseases. Long QT syndrome (19%) was the most prevalent diagnosis. In 42 (61%) of 69 ACA victims, the cause of the event was determined (inherited in 31 [74%]). Hypertrophic cardiomyopathy was most prevalent (17%). CONCLUSION The yield of the current diagnostic workup in relatives of young SUD victims is 33% and is almost twice as high in young ACA victims. Inherited cardiac diseases are predominantly causative in both groups.

Incidence, Causes, and Outcomes of Out-of-Hospital Cardiac Arrest in Children: A Comprehensive, Prospective, Population-Based Study in the Netherlands

OBJECTIVES This study sought to determine comprehensively the incidence of pediatric out-of-hospital cardiac arrest (OHCA) and its contribution to total pediatric mortality, the causes of pediatric OHCA, and the outcome of resuscitation of pediatric OHCA patients. BACKGROUND There is a paucity of complete studies on incidence, causes, and outcomes of pediatric OHCA. METHODS In this prospective, population-based study, OHCA victims younger than age 21 years in 1 province of the Netherlands were registered through both emergency medical services and coroners over a period of 4.3 years. Death certificate data on total pediatric mortality, survival status, and neurological outcome at hospital discharge also were obtained. RESULTS With a total mortality of 923 during the study period and 233 victims of OHCA (including 221 who died and 12 who survived), OHCA caused 24% (221 of 923) of total pediatric mortality. Natural causes of OHCA amounted to 115 (49%) cases, with cardiac causes being most prevalent (n = 90, 39%). The incidence of pediatric OHCA was 9.0 per 100,000 pediatric person-years (95% confidence interval: 7.8 to 10.3), whereas the incidence of pediatric OHCA from cardiac causes was 3.2 (95% confidence interval: 2.5 to 3.9). Of 51 resuscitated patients, 12 (24%) survived; among survivors, 10 (83%) had a neurologically intact outcome. CONCLUSIONS Out-of-hospital cardiac arrest accounts for a significant proportion of pediatric mortality, and cardiac causes are the most prevalent causes of OHCA. The vast majority of OHCA survivors have a neurologically intact outcome.

Derivation and validation of a simple exercise-based algorithm for prediction of genetic testing in relatives of LQTS probands

Background— Genetic testing can diagnose long-QT syndrome (LQTS) in asymptomatic relatives of patients with an identified mutation; however, it is costly and subject to availability. The accuracy of a simple algorithm that incorporates resting and exercise ECG parameters for screening LQTS in asymptomatic relatives was evaluated, with genetic testing as the gold standard. Methods and Results— Asymptomatic first-degree relatives of genetically characterized probands were recruited from 5 centers. QT intervals were measured at rest, during exercise, and during recovery. Receiver operating characteristics were used to establish optimal cutoffs. An algorithm for identifying LQTS carriers was developed in a derivation cohort and validated in an independent cohort. The derivation cohort consisted of 69 relatives (28 with LQT1, 20 with LQT2, and 21 noncarriers). Mean age was 35±18 years, and resting corrected QT interval (QTc) was 466±39 ms. Abnormal resting QTc (females ≥480 ms; males ≥470 ms) was 100% specific for gene carrier status, but was observed in only 48% of patients; however, mutations were observed in 68% and 42% of patients with a borderline or normal resting QTc, respectively. Among these patients, 4-minute recovery QTc ≥445 ms correctly restratified 22 of 25 patients as having LQTS and 19 of 21 patients as being noncarriers. The combination of resting and 4-minute recovery QTc in a screening algorithm yielded a sensitivity of 0.94 and specificity of 0.90 for detecting LQTS carriers. When applied to the validation cohort (n=152; 58 with LQT1, 61 with LQT2, and 33 noncarriers; QTc=443±47 ms), sensitivity was 0.92 and specificity was 0.82. Conclusions— A simple algorithm that incorporates resting and exercise-recovery QTc is useful in identifying LQTS in asymptomatic relatives.

Familial evaluation in catecholaminergic polymorphic ventricular tachycardia disease penetrance and expression in cardiac ryanodine receptor mutation-carrying relatives

Background— Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome associated with mutations in the cardiac ryanodine receptor gene ( Ryr2 ) in the majority of patients. Previous studies of CPVT patients mainly involved probands, so current insight into disease penetrance, expression, genotype-phenotype correlations, and arrhythmic event rates in relatives carrying the Ryr2 mutation is limited. Methods and Results— One-hundred sixteen relatives carrying the Ryr2 mutation from 15 families who were identified by cascade screening of the Ryr2 mutation causing CPVT in the proband were clinically characterized, including 61 relatives from 1 family. Fifty-four of 108 antiarrhythmic drug-free relatives (50%) had a CPVT phenotype at the first cardiological examination, including 27 (25%) with nonsustained ventricular tachycardia. Relatives carrying a Ryr2 mutation in the C-terminal channel-forming domain showed an increased odds of nonsustained ventricular tachycardia (odds ratio, 4.1; 95% CI, 1.5–11.5; P =0.007, compared with N-terminal domain) compared with N-terminal domain. Sinus bradycardia was observed in 19% of relatives, whereas other supraventricular dysrhythmias were present in 16%. Ninety-eight (most actively treated) relatives (84%) were followed up for a median of 4.7 years (range, 0.3–19.0 years). During follow-up, 2 asymptomatic relatives experienced exercise-induced syncope. One relative was not being treated, whereas the other was noncompliant. None of the 116 relatives died of CPVT during a 6.7-year follow-up (range, 1.4–20.9 years). Conclusions— Relatives carrying an Ryr2 mutation show a marked phenotypic diversity. The vast majority do not have signs of supraventricular disease manifestations. Mutation location may be associated with severity of the phenotype. The arrhythmic event rate during follow-up was low.Background— Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome associated with mutations in the cardiac ryanodine receptor gene (Ryr2) in the majority of patients. Previous studies of CPVT patients mainly involved probands, so current insight into disease penetrance, expression, genotype-phenotype correlations, and arrhythmic event rates in relatives carrying the Ryr2 mutation is limited. Methods and Results— One-hundred sixteen relatives carrying the Ryr2 mutation from 15 families who were identified by cascade screening of the Ryr2 mutation causing CPVT in the proband were clinically characterized, including 61 relatives from 1 family. Fifty-four of 108 antiarrhythmic drug-free relatives (50%) had a CPVT phenotype at the first cardiological examination, including 27 (25%) with nonsustained ventricular tachycardia. Relatives carrying a Ryr2 mutation in the C-terminal channel-forming domain showed an increased odds of nonsustained ventricular tachycardia (odds ratio, 4.1; 95% CI, 1.5–11.5; P=0.007, compared with N-terminal domain) compared with N-terminal domain. Sinus bradycardia was observed in 19% of relatives, whereas other supraventricular dysrhythmias were present in 16%. Ninety-eight (most actively treated) relatives (84%) were followed up for a median of 4.7 years (range, 0.3–19.0 years). During follow-up, 2 asymptomatic relatives experienced exercise-induced syncope. One relative was not being treated, whereas the other was noncompliant. None of the 116 relatives died of CPVT during a 6.7-year follow-up (range, 1.4–20.9 years). Conclusions— Relatives carrying an Ryr2 mutation show a marked phenotypic diversity. The vast majority do not have signs of supraventricular disease manifestations. Mutation location may be associated with severity of the phenotype. The arrhythmic event rate during follow-up was low.

Sudden death in the young: what do we know about it and how to prevent?

Sudden death (SD) of children and adults ages 1 to 40 years has received increasing attention over the past decades. In this report, we provide an overview of this problem, consider several mass screening strategies to prevent these events, and critically appraise these strategies in light of the well known Wilson and Jungner criteria (Table 1).1 Finally, we present an alternative approach: optimal assessment of first-degree relatives of newly diagnosed patients with an inherited cardiac disease and young SD victims to identify those relatives at risk of sudden cardiac death (SCD). View this table: Table 1. Wilson and Jungner Criteria for Assessment of Screening ### Definitions SD or its synonyms are generally defined as natural, unexpected death within 1 hour of the onset of symptoms.2 Four temporal elements should be considered in the use of this definition, that is, prodromes, onset of the terminal event, cardiac arrest, and biological death. The 1-hour definition refers to the period between onset of the terminal event, that is, acute changes in cardiovascular status, and cardiac arrest. Nonspecific prodromal symptoms, for example, chest pain, palpitations, or dyspnea, can be present during the days or weeks before a cardiac arrest.3 The biological legal death can occur days or weeks after the cardiac arrest, as patients can survive with irreversible brain damage and life support. In addition, when death occurs unwitnessed within 24 hours of being seen alive and functioning normally, this is also termed SD.2 In this report, the 1-hour definition is applied unless otherwise indicated. Depending on the underlying cause, SD can be divided into SCD, defined as SD from a cardiac cause,2 and SD due to noncardiac causes, for example, intracranial hemorrhage, epilepsy, pulmonary embolism, or asthma.4,5⇓ This subdivision is clinically relevant because cardiac causes are inherited in a significant …

Effects of flecainide on exercise-induced ventricular arrhythmias and recurrences in genotype-negative patients with catecholaminergic polymorphic ventricular tachycardia

BACKGROUND Conventional therapy with beta-blockers is incompletely effective in preventing arrhythmic events in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT). We have previously discovered that flecainide in addition to conventional drug therapy prevents ventricular arrhythmias in patients with genotype-positive CPVT. OBJECTIVE To study the efficacy of flecainide in patients with genotype-negative CPVT. METHODS We studied the efficacy of flecainide for reducing ventricular arrhythmias during exercise testing and preventing arrhythmia events during long-term follow-up. RESULTS Twelve patients with genotype-negative CPVT were treated with flecainide. Conventional therapy failed to control ventricular arrhythmias in all patients. Flecainide was initiated because of significant ventricular arrhythmias (n = 8), syncope (n = 3), or cardiac arrest (n = 1). At the baseline exercise test before flecainide, 6 patients had ventricular tachycardia and 5 patients had bigeminal or frequent ventricular premature beats. Flecainide reduced ventricular arrhythmias at the exercise test in 8 patients compared to conventional therapy, similar to that in patients with genotype-positive CPVT in our previous report. Notably, flecainide completely prevented ventricular arrhythmias in 7 patients. Flecainide was continued in all patients except for one who had ventricular tachycardia at the exercise test on flecainide. During a follow-up of 48±94 months, arrhythmia events (sudden cardiac death and aborted cardiac arrest) associated with noncompliance occurred in 2 patients. Flecainide was not discontinued owing to side effects in any of the patients. CONCLUSIONS Flecainide was effective in patients with genotype-negative CPVT, suggesting that spontaneous Ca(2+) release from ryanodine channels plays a role in arrhythmia susceptibility, similar to that in patients with genotype-positive CPVT.

Utility of Post-Mortem Genetic Testing in Cases of Sudden Arrhythmic Death Syndrome

Background Sudden arrhythmic death syndrome (SADS) describes a sudden death with negative autopsy and toxicological analysis. Cardiac genetic disease is a likely etiology. Objectives This study investigated the clinical utility and combined yield of post-mortem genetic testing (molecular autopsy) in cases of SADS and comprehensive clinical evaluation of surviving relatives. Methods We evaluated 302 expertly validated SADS cases with suitable DNA (median age: 24 years; 65% males) who underwent next-generation sequencing using an extended panel of 77 primary electrical disorder and cardiomyopathy genes. Pathogenic and likely pathogenic variants were classified using American College of Medical Genetics (ACMG) consensus guidelines. The yield of combined molecular autopsy and clinical evaluation in 82 surviving families was evaluated. A gene-level rare variant association analysis was conducted in SADS cases versus controls. Results A clinically actionable pathogenic or likely pathogenic variant was identified in 40 of 302 cases (13%). The main etiologies established were catecholaminergic polymorphic ventricular tachycardia and long QT syndrome (17 [6%] and 11 [4%], respectively). Gene-based rare variants association analysis showed enrichment of rare predicted deleterious variants in RYR2 (p = 5 × 10-5). Combining molecular autopsy with clinical evaluation in surviving families increased diagnostic yield from 26% to 39%. Conclusions Molecular autopsy for electrical disorder and cardiomyopathy genes, using ACMG guidelines for variant classification, identified a modest but realistic yield in SADS. Our data highlighted the predominant role of catecholaminergic polymorphic ventricular tachycardia and long QT syndrome, especially the RYR2 gene, as well as the minimal yield from other genes. Furthermore, we showed the enhanced utility of combined clinical and genetic evaluation.