An inherited life-threatening arrhythmia model established by screening randomly mutagenized mice.

Inherited arrhythmia syndromes (IASs) can cause life-threatening arrhythmias and are responsible for a significant proportion of sudden cardiac deaths (SCDs). Despite progress in the development of devices to prevent SCDs, the precise molecular mechanisms that induce detrimental arrhythmias remain to be fully investigated, and more effective therapies are desirable. In the present study, we screened a large-scale randomly mutagenized mouse library by electrocardiography to establish a disease model of IASs and consequently found one pedigree that exhibited spontaneous ventricular arrhythmias (VAs) followed by SCD within 1 y after birth. Genetic analysis successfully revealed a missense mutation (p.I4093V) of the ryanodine receptor 2 gene to be a cause of the arrhythmia. We found an age-related increase in arrhythmia frequency accompanied by cardiomegaly and decreased ventricular contractility in the Ryr2I4093V/+ mice. Ca2+ signaling analysis and a ryanodine binding assay indicated that the mutant ryanodine receptor 2 had a gain-of-function phenotype and enhanced Ca2+ sensitivity. Using this model, we detected the significant suppression of VA following flecainide or dantrolene treatment. Collectively, we established an inherited life-threatening arrhythmia mouse model from an electrocardiogram-based screen of randomly mutagenized mice. The present IAS model may prove feasible for use in investigating the mechanisms of SCD and assessing therapies.

Flecainide causing elevated capture thresholds on pacemaker implantation.

Flecainide is a Vaughan Williams class 1c antiarrhythmic used to treat supraventricular and ventricular arrhythmias. It has been described as a rare cause for increased pacemaker capture thresholds. We describe a report of a patient, in her early 80s, presenting with tachy-brady syndrome on a background of permanent atrial fibrillation. She was treated with metoprolol and flecainide by her private cardiologist. Permanent right ventricular chamber pacing was recommended for her slow heart rate. At insertion of her single chamber pacemaker, she was noted to have elevated capture thresholds despite appropriate lead positioning. A flecainide level was elevated at 1.1 µg/mL, and it was subsequently ceased. This was associated with a rapid improvement in her capture threshold. Flecainide should be considered as a cause for elevated pacing thresholds at the time of implant. Particular care should be taken for at-risk groups such as the elderly and patients with renal impairment.

Insights into adherence to medication and lifestyle recommendations in an international cohort of patients with catecholaminergic polymorphic ventricular tachycardia.

AIMS: In patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), a rare inherited arrhythmia syndrome, arrhythmic events can be prevented by medication and lifestyle recommendations. In patients who experience breakthrough arrhythmic events, non-adherence plays an essential role. We aimed to investigate the incidence and potential reasons for non-adherence to medication and lifestyle recommendations in a large, international cohort of patients with CPVT. METHODS AND RESULTS: An online multilingual survey was shared with CPVT patients worldwide by their cardiologists, through peer-recruitment, and on social media from November 2022 until July 2023. Self-reported non-adherence was measured using the validated Medication Adherence Rating Scale (MARS) and a newly developed questionnaire about lifestyle. Additionally, validated questionnaires were used to assess potential reasons for medication non-adherence. Two-hundred-and-eighteen patients completed the survey, of whom 200 (92%) were prescribed medication [122 (61%) female; median age 33.5 years (interquartile range: 22-50)]. One-hundred-and-three (52%) were prescribed beta-blocker and flecainide, 85 (43%) beta-blocker, and 11 (6%) flecainide. Thirty-four (17%) patients experienced a syncope, aborted cardiac arrest or appropriate implantable cardioverter defibrillator shock after diagnosis. Nineteen (13.4%) patients were exercising more than recommended. Thirty (15%) patients were non-adherent to medication. Female sex [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.3-12.0, P = 0.019], flecainide monotherapy compared to combination therapy (OR 6.8, 95% CI 1.6-31.0, P = 0.010), and a higher agreement with statements regarding concerns about CPVT medication (OR 1.2, 95% CI 1.1-1.3, P < 0.001) were independently associated with non-adherence. CONCLUSION: The significant rate of non-adherence associated with concerns regarding CPVT-related medication, emphasizes the potential for improving therapy adherence by targeted patient education.

Evidence of exposure to flecainide in a newborn by keratinous matrices testing and interpretation of the findings.

Pediatric poisoning represents a serious problem all around the world. Abuse or neglect of children by adults must be highlighted in children exposed to drugs to which they would not normally have access. Usually, segmental hair analysis would allow in these contexts to determine whether the exposure was unique or repetitive. Hair and nail samples from a 9-month-old girl were received in our laboratory for analysis, after the child was hospitalized due to severe dehydration caused by her mother's neglect. At the admission, flecainide, an antiarrhythmic never prescribed to the child, was identified in the daughter urine. Using an LC-MS/MS method, flecainide tested positive in the child's hair at the following concentrations: 66 pg/mg (root to 1 cm), 61 pg/mg (1-2 cm), and 125 pg/mg (2-3 cm). Traces below the limit of quantification (1 pg/mg) were also present in the nail clippings. These concentrations are much lower than those obtained in adults under daily treatment. Given the different pharmacokinetic and dynamic parameters in children, the different rate of hair growth, and the greater porosity of the hair, which makes it more prone to external contamination, the interpretation of hair findings in children remains very complicated. In this case, it can be assumed that the presence of the drug in the urine indicates systemic incorporation and that administration had occurred for some months (three positive segments). The interpretation of hair tests from young children needs a global review of all the findings, as a positive result cannot stand alone to claim repetitive exposures.

Effect of Flecainide and Ibutilide Alone and in Combination to Terminate and Prevent Recurrence of Atrial Fibrillation.

BACKGROUND: There is a need for improved approaches to rhythm control therapy of atrial fibrillation (AF). METHODS: The effectiveness of flecainide (1.5 µmol/L) and ibutilide (20 nmol/L), alone and in combination, to cardiovert and prevent AF recurrence was studied in canine-isolated coronary-perfused right atrioventricular preparations. We also examined the safety of the combination of flecainide (1.5 µmol/L) and ibutilide (50 nmol/L) using canine left ventricular wedge preparations. RESULTS: Sustained AF (>1 hour) was inducible in 100%, 60%, 20%, and 0% of atria in the presence of acetylcholine alone, acetylcholine+ibutilide, acetylcholine+flecainide, and acetylcholine+ibutilide+flecainide, respectively. When used alone, flecainide and ibutilide cardioverted sustained AF in 40% and 20% of atria, respectively, but in 100% of atria when used in combination. Ibutilide prolonged atrial and ventricular effective refractory period by 15% and 8%, respectively, at a cycle length of 500 ms (P<0.05 for both). Flecainide increased the effective refractory period in atria by 27% (P<0.01) but by only 2% in the ventricles. The combination of the 2 drugs lengthened the effective refractory period by 42% in atria (P<0.01) but by only 7% (P<0.05) in the ventricles. In left ventricular wedges, ibutilide prolonged QT and Tpeak-Tend intervals by 25 and 55%, respectively (P<0.05 for both; cycle length, 2000 ms). The addition of flecainide (1.5 µmol/L) partially reversed these effects (P<0.05 for both parameters versus ibutilide alone). Torsades de Pointes score was relatively high with ibutilide alone and low with the drug combination. CONCLUSIONS: In our experimental model, a combination of flecainide and ibutilide significantly improves cardioversion and prevents the recurrence of AF compared with monotherapies with little to no risk for the development of long-QT-mediated ventricular proarrhythmia.

Electrophysiological Characteristics and Ablation Outcomes in Patients With Catecholaminergic Polymorphic Ventricular Tachycardia.

BACKGROUND: Catheter ablation of premature ventricular contractions (PVCs) that trigger polymorphic ventricular tachycardia (PVT) or ventricular fibrillation has been reported as a novel therapy to reduce the syncope events in patients with catecholaminergic PVT, whereas the long-term ablation outcome and its value in improving exercise-induced ventricular arrhythmias remain unclear. METHODS AND RESULTS: Fourteen consecutive selected patients with catecholaminergic PVT (mean±SD age, 16±6 years; 43% male patients) treated with maximum ß-blockers with no possibility of adding flecainide were prospectively enrolled for catheter ablation. The primary end point was syncope recurrence, and the secondary end point was the reduction of the ventricular arrhythmia score during exercise testing. Twenty-six PVT/ventricular fibrillation-triggering PVCs were identified for ablation. The trigger beats arose from the left ventricle in 50% of the cases and from both ventricles in 36% of the cases. Purkinje potentials were observed at 27% of the targets. After a mean follow-up of 49 months after ablation, 8 (57%) patients were free from syncope recurrence. Ablation of trigger beat significantly reduced the syncope frequency (mean±SD, 4.3±1.6 to 0.5±0.8 events per year; P<0.001) and improved the ventricular arrhythmia scores at the 3-month (5 [range, 3-6] to 1.5 [range, 0-5]; P=0.002) and 12-month (5 [range, 3-6] to 2 [range, 0-5]; P=0.014) follow-ups. The induction of nontriggering PVCs postablation was closely associated with syncope recurrence (hazard ratio, 6.8 [95% CI, 1.3-35.5]; P=0.026). CONCLUSIONS: Catheter ablation of PVT/ventricular fibrillation-triggering PVCs in patients with catecholaminergic PVT who cannot receive flecainide treatment seems to be a safe and feasible adjunctive treatment that may reduce the syncope burden and improve exercise-related ventricular arrhythmias. Induction of nontriggering PVCs after ablation is associated with a higher risk of syncope recurrence.

Refractory supraventricular fetal tachycardia as a cause of non-immune hydrops: management conundrum.

Supraventricular tachyarrhythmia (SVT) is the most common form of fetal tachyarrhythmias. The presentation can vary from ill-defined, non-sustained episodes of tachyarrhythmia to frank non-immune hydrops. The standard of care is transplacental therapy by treating the mother with oral antiarrhythmic drugs, followed by direct fetal therapy in refractory cases. We report a case of primigravida in her late 20s, who presented at 28.1 weeks of gestation with fetal hydrops and SVT. She was initially managed with oral digoxin and flecainide, but due to worsening hydrops, risk of fetal demise and extreme prematurity, further management by direct fetal therapy was given in terms of intramuscular digoxin and intraperitoneal flecainide. Following which, the fetus had a favourable outcome. This case highlights the possible role of direct fetal therapy in refractory cases of SVT.

Insights on the mechanism of flecainide in catecholaminergic polymorphic ventricular tachycardia.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome characterized by defective cardiac ryanodine receptor (RyR2) calcium release during times of adrenergic stimulation, resulting in bidirectional or polymorphic ventricular tachycardia. Flecainide is a class 1c anti-arrhythmic drug that has demonstrated therapeutic efficacy in treating CPVT. However, its mechanism of action remains disputed. One group proposes a direct effect of flecainide on RyR2-mediated calcium release, while another proposes an indirect effect via sodium channel blockade and modulation of intracellular calcium dynamics. In light of recent studies, this commentary aims to explore and discuss the evidence base for these potential mechanisms.

Flecainide Is Associated With a Lower Incidence of Arrhythmic Events in a Large Cohort of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia.

BACKGROUND: In severely affected patients with catecholaminergic polymorphic ventricular tachycardia, beta-blockers are often insufficiently protective. The purpose of this study was to evaluate whether flecainide is associated with a lower incidence of arrhythmic events (AEs) when added to beta-blockers in a large cohort of patients with catecholaminergic polymorphic ventricular tachycardia. METHODS: From 2 international registries, this multicenter case cross-over study included patients with a clinical or genetic diagnosis of catecholaminergic polymorphic ventricular tachycardia in whom flecainide was added to beta-blocker therapy. The study period was defined as the period in which background therapy (ie, beta-blocker type [beta1-selective or nonselective]), left cardiac sympathetic denervation, and implantable cardioverter defibrillator treatment status, remained unchanged within individual patients and was divided into pre-flecainide and on-flecainide periods. The primary end point was AEs, defined as sudden cardiac death, sudden cardiac arrest, appropriate implantable cardioverter defibrillator shock, and arrhythmic syncope. The association of flecainide with AE rates was assessed using a generalized linear mixed model assuming negative binomial distribution and random effects for patients. RESULTS: A total of 247 patients (123 [50%] females; median age at start of flecainide, 18 years [interquartile range, 14-29]; median flecainide dose, 2.2 mg/kg per day [interquartile range, 1.7-3.1]) were included. At baseline, all patients used a beta-blocker, 70 (28%) had an implantable cardioverter defibrillator, and 21 (9%) had a left cardiac sympathetic denervation. During a median pre-flecainide follow-up of 2.1 years (interquartile range, 0.4-7.2), 41 patients (17%) experienced 58 AEs (annual event rate, 5.6%). During a median on-flecainide follow-up of 2.9 years (interquartile range, 1.0-6.0), 23 patients (9%) experienced 38 AEs (annual event rate, 4.0%). There were significantly fewer AEs after initiation of flecainide (incidence rate ratio, 0.55 [95% CI, 0.38-0.83]; P=0.007). Among patients who were symptomatic before diagnosis or during the pre-flecainide period (n=167), flecainide was associated with significantly fewer AEs (incidence rate ratio, 0.49 [95% CI, 0.31-0.77]; P=0.002). Among patients with ≥1 AE on beta-blocker therapy (n=41), adding flecainide was also associated with significantly fewer AEs (incidence rate ratio, 0.25 [95% CI, 0.14-0.45]; P<0.001). CONCLUSIONS: For patients with catecholaminergic polymorphic ventricular tachycardia, adding flecainide to beta-blocker therapy was associated with a lower incidence of AEs in the overall cohort, in symptomatic patients, and particularly in patients with breakthrough AEs while on beta-blocker therapy.

Medical cardioversion of atrial fibrillation and flutter with class IC antiarrhythmic drugs in young patients with and without congenital heart disease.

INTRODUCTION: The use of flecainide and propafenone for medical cardioversion of atrial fibrillation (AF) and atrial flutter/intra-atrial reentrant tachycardia (IART) is well-described in adults without congenital heart disease (CHD). Data are sparse regarding their use for the same purpose in adults with CHD and in adolescent patients with anatomically normal hearts and we sought to describe the use of class IC drugs in this population and identify factors associated with decreased likelihood of success. METHODS: Single center retrospective cohort study of patients who received oral flecainide or propafenone for medical cardioversion of AF or IART from 2000 to 2022. The unit of analysis was each episode of AF/IART. We performed a time-to-sinus rhythm analysis using a Cox proportional hazards model clustering on the patient to identify factors associated with increased likelihood of success. RESULTS: We identified 45 episodes involving 41 patients. As only episodes of AF were successfully cardioverted with medical therapy, episodes of IART were excluded from our analyses. Use of flecainide was the only factor associated with increased likelihood of success. There was a statistically insignificant trend toward decreased likelihood of success in patients with CHD. CONCLUSIONS: Flecainide was more effective than propafenone. We did not detect a difference in rate of conversion to sinus rhythm between patients with and without CHD and were likely underpowered to do so, however, there was a trend toward decreased likelihood of success in patients with CHD. That said, medical therapy was effective in >50% of patients with CHD with AF.

Can specific ECG markers identify a pharmacologically induced type 1 Brugada pattern? Insights from a large, single-center cohort.

BACKGROUND: In patients with a type 2 or 3 Brugada pattern, the pharmacological (IC drugs) induction of a type 1 pattern confirms the diagnosis of Brugada syndrome. OBJECTIVE: To evaluate the value of various ECG markers in predicting IC drug test results. METHODS: We retrospectively analysed 443 consecutive patients referred to our Center (from January 2010 to December 2019) to undergo Ajmaline/Flecainide testing; all had a type 2 or 3 Brugada pattern or were relatives with Brugada syndrome. Clinical parameters and ECG markers (r1V1 and SV6 duration and amplitude, QRSV1/QRSV6 duration, V1 and V2 ST amplitude) were independently evaluated for their association to pharmacological test positivity, and a logistic regression model was applied. RESULTS: The drug test was positive in 151 (34%) patients. On multivariate logistic regression analysis, age > 45 years, female gender, HR >60 bpm, QRSV1/QRSV6 duration >1 and non-isoelectric pattern in V2 were associated with a positive test. The percentage of patients who tested positive increased according to the presence of the above ECG markers (from 11.3% in the absence to 57.6% in the presence of both factors). During long-term follow-up, the clinical event rate was higher in patients with predictive ECG markers and very low in those without. CONCLUSIONS: In our population we confirmed the ability of QRSV1/QRSV6 duration >1 and of a non-isoelectric pattern in V2 to predict a pharmacologically induced type 1 Brugada pattern. Patients with neither of these ECG markers had a rather low event rate during follow-up.

Personalized medicine in the dish to prevent calcium leak associated with short-coupled polymorphic ventricular tachycardia in patient-derived cardiomyocytes.

BACKGROUND: Polymorphic ventricular tachycardia (PMVT) is a rare genetic disease associated with structurally normal hearts which in 8% of cases can lead to sudden cardiac death, typically exercise-induced. We previously showed a link between the RyR2-H29D mutation and a clinical phenotype of short-coupled PMVT at rest using patient-specific hiPSC-derived cardiomyocytes (hiPSC-CMs). In the present study, we evaluated the effects of clinical and experimental anti-arrhythmic drugs on the intracellular Ca2+ handling, contractile and molecular properties in PMVT hiPSC-CMs in order to model a personalized medicine approach in vitro. METHODS: Previously, a blood sample from a patient carrying the RyR2-H29D mutation was collected and reprogrammed into several clones of RyR2-H29D hiPSCs, and in addition we generated an isogenic control by reverting the RyR2-H29D mutation using CRIPSR/Cas9 technology. Here, we tested 4 drugs with anti-arrhythmic properties: propranolol, verapamil, flecainide, and the Rycal S107. We performed fluorescence confocal microscopy, video-image-based analyses and biochemical analyses to investigate the impact of these drugs on the functional and molecular features of the PMVT RyR2-H29D hiPSC-CMs. RESULTS: The voltage-dependent Ca2+ channel inhibitor verapamil did not prevent the aberrant release of sarcoplasmic reticulum (SR) Ca2+ in the RyR2-H29D hiPSC-CMs, whereas it was prevented by S107, flecainide or propranolol. Cardiac tissue comprised of RyR2-H29D hiPSC-CMs exhibited aberrant contractile properties that were largely prevented by S107, flecainide and propranolol. These 3 drugs also recovered synchronous contraction in RyR2-H29D cardiac tissue, while verapamil did not. At the biochemical level, S107 was the only drug able to restore calstabin2 binding to RyR2 as observed in the isogenic control. CONCLUSIONS: By testing 4 drugs on patient-specific PMVT hiPSC-CMs, we concluded that S107 and flecainide are the most potent molecules in terms of preventing the abnormal SR Ca2+ release and contractile properties in RyR2-H29D hiPSC-CMs, whereas the effect of propranolol is partial, and verapamil appears ineffective. In contrast with the 3 other drugs, S107 was able to prevent a major post-translational modification of RyR2-H29D mutant channels, the loss of calstabin2 binding to RyR2. Using patient-specific hiPSC and CRISPR/Cas9 technologies, we showed that S107 is the most efficient in vitro candidate for treating the short-coupled PMVT at rest.

The Antiarrhythmic Drug Flecainide Enhances Aversion to HCl in Mice.

Drug-induced taste disorders reduce quality of life, but little is known about the molecular mechanisms by which drugs induce taste disturbances. In this study, we investigated the short-term and long-term effects of the antiarrhythmic drug flecainide, which is known to cause taste dysfunction. Analyses of behavioral responses (licking tests) revealed that mice given a single intraperitoneal injection of flecainide exhibited a significant reduction in preference for a sour tastant (HCl) but not for other taste solutions (NaCl, quinine, sucrose, KCl and monopotassium glutamate) when compared with controls. Mice administered a single dose of flecainide also had significantly higher taste nerve responses to HCl but not to other taste solutions. Compared with controls, mice administered flecainide once-daily for 30 d showed a reduced preference for HCl without any changes in the behavioral responses to other taste solutions. The electrophysiological experiments using HEK293T cells transiently expressing otopetrin-1 (Otop1; the mouse sour taste receptor) showed that flecainide did not alter the responses to HCl. Taken together, our results suggest that flecainide specifically enhances the response to HCl in mice during short-term and long-term administration. Although further studies will be needed to elucidate the molecular mechanisms, these findings provide new insights into the pathophysiology of drug-induced taste disorders.

Idiopathic premature ventricular complexes treatment: Comparison of flecainide, propafenone, and sotalol.

BACKGROUND: Beta-blockers (BB) or dihydropyridine calcium channel blockers (CCBs) are still the first choices in the treatment of idiopathic premature ventricular complexes (PVCs), with low-modest efficacy. Antiarrhythmic drugs (AADs) of Ic class are moderate to highly efficient but the evidence on their benefits is still limited. AIM: To compare effectiveness and safety of flecainide, propafenone, and sotalol in the treatment of symptomatic idiopathic PVCs. METHODS: Our single-center retrospective study analyzed 104 consecutive patients with 130 medication episodes of frequent idiopathic PVCs treated with AADs flecainide, propafenone (Ic class) or sotalol (III class). The primary outcome was complete/near complete reduction of PVCs after medication episode (PVCs burden reduction >99%), and the secondary outcome was significant PVC burden reduction (≥80%). RESULTS: The complete/near complete PVCs burden reduction occurred in 31% and was significant in 43% of treated patients. A reduction of PVC burden for >99% was achieved in 56% of patients on flecainide, in 11% of patients on propafenone (p = .002), and in 21% of patients receiving sotalol (p = .031). There was no difference between propafenone and sotalol (p = .174). A reduction of PVC burden for ≥80% was achieved in 64% of patients on flecainide, in 30% of patients on propafenone (p = .009), and 33% of patients on sotalol (p = .020). There was no difference between propafenone and sotalol (p = .661). CONCLUSIONS: The efficacy of AADs class Ic and III in the treatment of idiopathic PVCs was modest. Flecainide was the most effective AAD in the achievement of complete/near complete or significant PVC burden reduction, compared to propafenone and sotalol.

Calcium Release Deficiency Syndrome: A New Inherited Arrhythmia Syndrome.

Calcium release deficiency syndrome (CRDS) is a newly described form of inherited arrhythmia caused by damaging loss-of-function variants in the cardiac ryanodine receptor (RyR2). Unlike the prototypical RyR2 gain-of-function channelopathy, known as catecholaminergic polymorphic ventricular tachycardia, patients with CRDS are predisposed to sudden death usually in the absence of any electrical abnormalities at rest or during stress electrocardiography. This makes diagnosis incredibly challenging, however, an invasive electrophysiologic test appears to be effective in unmasking the phenotype, called the long-burst, long-pause, short-coupled ventricular extra-stimulus protocol. Optimal therapies for patients with CRDS remain unestablished, although flecainide appears to be a promising candidate drug.

Failure of diltiazem to prevent 1:1 conduction of atrial flutter: a case report.

BACKGROUND: Atrial flutter with 1:1 conduction to the ventricles is a dangerous cardiac arrhythmia. Contemporary guidelines recommend atrioventricular nodal blocking agents should be co-administered with class 1C anti-arrhythmics, as prophylaxis against 1:1 flutter. No guidance is provided on the type or strength of atrioventricular nodal blockade required, and in practice, these agents are frequently prescribed at low dose, or even omitted, due to their side effect profile. CASE PRESENTATION: A 62 year old Caucasian man with a history of paroxysmal atrial fibrillation treated with flecainide, presented with atrial flutter with 1:1 conduction to the ventricles and was cardioverted. Diltiazem was added to prevent this complication and he again presented with atrial flutter with 1:1 conduction to the ventricles, despite prophylaxis with coadministration of diltiazem. CONCLUSIONS: This case report demonstrates failure of diltiazem to prevent 1:1 flutter in a patient chronically treated with flecainide for paroxysmal atrial fibrillation.

What determines the optimal pharmacological treatment of atrial fibrillation? Insights from in silico trials in 800 virtual atria.

The best pharmacological treatment for each atrial fibrillation (AF) patient is unclear. We aim to exploit AF simulations in 800 virtual atria to identify key patient characteristics that guide the optimal selection of anti-arrhythmic drugs. The virtual cohort considered variability in electrophysiology and low voltage areas (LVA) and was developed and validated against experimental and clinical data from ionic currents to ECG. AF sustained in 494 (62%) atria, with large inward rectifier K+ current (IK1 ) and Na+ /K+ pump (INaK ) densities (IK1 0.11 ± 0.03 vs. 0.07 ± 0.03 S mF-1 ; INaK 0.68 ± 0.15 vs. 0.38 ± 26 S mF-1 ; sustained vs. un-sustained AF). In severely remodelled left atrium, with LVA extensions of more than 40% in the posterior wall, higher IK1 (median density 0.12 ± 0.02 S mF-1 ) was required for AF maintenance, and rotors localized in healthy right atrium. For lower LVA extensions, rotors could also anchor to LVA, in atria presenting short refractoriness (median L-type Ca2+ current, ICaL , density 0.08 ± 0.03 S mF-1 ). This atrial refractoriness, modulated by ICaL and fast Na+ current (INa ), determined pharmacological treatment success for both small and large LVA. Vernakalant was effective in atria presenting long refractoriness (median ICaL density 0.13 ± 0.05 S mF-1 ). For short refractoriness, atria with high INa (median density 8.92 ± 2.59 S mF-1 ) responded more favourably to amiodarone than flecainide, and the opposite was found in atria with low INa (median density 5.33 ± 1.41 S mF-1 ). In silico drug trials in 800 human atria identify inward currents as critical for optimal stratification of AF patient to pharmacological treatment and, together with the left atrial LVA extension, for accurately phenotyping AF dynamics. KEY POINTS: Atrial fibrillation (AF) maintenance is facilitated by small L-type Ca2+ current (ICaL ) and large inward rectifier K+ current (IK1 ) and Na+ /K+ pump. In severely remodelled left atrium, with low voltage areas (LVA) covering more than 40% of the posterior wall, sustained AF requires higher IK1 and rotors localize in healthy right atrium. For lower LVA extensions, rotors can also anchor to LVA, if the atria present short refractoriness (low ICaL ) Vernakalant is effective in atria presenting long refractoriness (high ICaL ). For short refractoriness, atria with fast Na+ current (INa ) up-regulation respond more favourably to amiodarone than flecainide, and the opposite is found in atria with low INa . The inward currents (ICaL and INa ) are critical for optimal stratification of AF patient to pharmacological treatment and, together with the left atrial LVA extension, for accurately phenotyping AF dynamics.

Trans-2,3-enoyl-CoA reductase-like-related catecholaminergic polymorphic ventricular tachycardia with regular ventricular tachycardia and response to flecainide.

INTRODUCTION: We describe a unique case of TECRL-CPVT presented with cardiac arrest. METHODS: Post resuscitation, the patient developed regular ventricular tachycardia featuring a left purkinje system morphology. RESULTS: There was clear suppression of arrhythmia with the addition of flecainide and isolated ventricular ectopy causing secondary T-wave changes. CONCLUSION: A high index of suspicion was required to eventually make the diagnosis through whole exome sequencing.