The development of inherited cardiac conditions services: current position and future perspectives.

BACKGROUND: Over the last two decades, inherited cardiac conditions (ICC) centres have emerged with the aim of improving outcomes for patients and their families, through early diagnosis, genetic testing, risk assessment and specialist treatment. SOURCES OF DATA: A literature search was performed using PubMed (https://pubmed.ncbi.nlm.nih.gov/). Commissioned ICC service reviews from NHS England, NHS Improvement and PHG Foundation were evaluated. AREAS OF AGREEMENT: ICC patient management requires a multi-disciplinary approach. ICC services are predominantly based within tertiary centres. Despite expansion, provision of care remains inadequate to meet rising demands. Access to services is inconsistent, partly due to geographic variation and lack of standardized pathways. AREAS OF CONTROVERSY: The optimal ICC care model remains undecided, although there is growing interest in 'hub-and-spoke' networks, which could aid secondary and tertiary service integration and repatriation of care. GROWING POINTS: Genetic mainstreaming is a priority for the Genomic Medicine Service Alliance. The benefits of telehealth and virtual clinics have been validated by their use during the COVID-19 pandemic. Other innovations to improve resource efficiency, such as clinical scientist-led and nurse-led clinics, show promise. AREAS TIMELY FOR DEVELOPING RESEARCH: An update for the NHS ICC service specifications is planned that appears well timed given the rapid evolution of the ICC landscape in the decade since last review. This has the potential to address needs including national audit, standardized pathways and ICC networks to improve governance and equity of care. Delegation of commissioning for specialist services to integrated care systems may also provide opportunity for increased regional direction.

Insight Into Myocardial Microstructure of Athletes and Hypertrophic Cardiomyopathy Patients Using Diffusion Tensor Imaging.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) remains the commonest cause of sudden cardiac death among young athletes. Differentiating between physiologically adaptive left ventricular (LV) hypertrophy observed in athletes' hearts and pathological HCM remains challenging. By quantifying the diffusion of water molecules, diffusion tensor imaging (DTI) MRI allows voxelwise characterization of myocardial microstructure. PURPOSE: To explore microstructural differences between healthy volunteers, athletes, and HCM patients using DTI. STUDY TYPE: Prospective cohort. POPULATION: Twenty healthy volunteers, 20 athletes, and 20 HCM patients. FIELD STRENGTH/SEQUENCE: 3T/DTI spin echo. ASSESSMENT: In-house MatLab software was used to derive mean diffusivity (MD) and fractional anisotropy (FA) as markers of amplitude and anisotropy of the diffusion of water molecules, and secondary eigenvector angles (E2A)-reflecting the orientations of laminar sheetlets. STATISTICAL TESTS: Independent samples t-tests were used to detect statistical significance between any two cohorts. Analysis of variance was utilized for detecting the statistical difference between the three cohorts. Statistical tests were two-tailed. A result was considered statistically significant at P ≤ 0.05. RESULTS: DTI markers were significantly different between HCM, athletes, and volunteers. HCM patients had significantly higher global MD and E2A, and significantly lower FA than athletes and volunteers. (MDHCM = 1.52 ± 0.06 × 10-3 mm2 /s, MDAthletes = 1.49 ± 0.03 × 10-3 mm2 /s, MDvolunteers = 1.47 ± 0.02 × 10-3 mm2 /s, P < 0.05; E2AHCM = 58.8 ± 4°, E2Aathletes = 47 ± 5°, E2Avolunteers = 38.5 ± 7°, P < 0.05; FAHCM = 0.30 ± 0.02, FAAthletes = 0.35 ± 0.02, FAvolunteers = 0.36 ± 0.03, P < 0.05). HCM patients had significantly higher E2A in their thickest segments compared to the remote (E2Athickest = 66.8 ± 7, E2Aremote = 51.2 ± 9, P < 0.05). DATA CONCLUSION: DTI depicts an increase in amplitude and isotropy of diffusion in the myocardium of HCM compared to athletes and volunteers as reflected by increased MD and decreased FA values. While significantly higher E2A values in HCM and athletes reflect steeper configurations of the myocardial sheetlets than in volunteers, HCM patients demonstrated an eccentric rise in E2A in their thickest segments, while athletes demonstrated a concentric rise. Further studies are required to determine the diagnostic capabilities of DTI. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY STAGE: 2.

Effect of cellular and extracellular pathology assessed by T1 mapping on regional contractile function in hypertrophic cardiomyopathy.

BACKGROUND: Regional contractile dysfunction is a frequent finding in hypertrophic cardiomyopathy (HCM). We aimed to investigate the contribution of different tissue characteristics in HCM to regional contractile dysfunction. METHODS: We prospectively recruited 50 patients with HCM who underwent cardiovascular magnetic resonance (CMR) studies at 3.0 T including cine imaging, T1 mapping and late gadolinium enhancement (LGE) imaging. For each segment of the American Heart Association model segment thickness, native T1, extracellular volume (ECV), presence of LGE and regional strain (by feature tracking and tissue tagging) were assessed. The relationship of segmental function, hypertrophy and tissue characteristics were determined using a mixed effects model, with random intercept for each patient. RESULTS: Individually segment thickness, native T1, ECV and the presence of LGE all had significant associations with regional strain. The first multivariable model (segment thickness, LGE and ECV) demonstrated that all strain parameters were associated with segment thickness (P < 0.001 for all) but not ECV. LGE (Beta 2.603, P = 0.024) had a significant association with circumferential strain measured by tissue tagging. In a second multivariable model (segment thickness, LGE and native T1) all strain parameters were associated with both segment thickness (P < 0.001 for all) and native T1 (P < 0.001 for all) but not LGE. CONCLUSION: Impairment of contractile function in HCM is predominantly associated with the degree of hypertrophy and native T1 but not markers of extracellular fibrosis (ECV or LGE). These findings suggest that impairment of contractility in HCM is mediated by mechanisms other than extracellular expansion that include cellular changes in structure and function. The cellular mechanisms leading to increased native T1 and its prognostic significance remain to be established.

Intra-cardiac and peripheral levels of biochemical markers of fibrosis in patients undergoing catheter ablation for atrial fibrillation.

AIMS: Measurement of circulating biomarkers of fibrosis may have a role in selecting patients and treatment strategy for catheter ablation. Pro-collagen type III N-terminal pro-peptide (PIIINP), C-telopeptide of type I collagen (ICTP), fibroblast growth factor 23 (FGF-23), and galectin 3 (gal-3) have all been suggested as possible biomarkers for this indication, but studies assessing whether peripheral levels reflect intra-cardiac levels are scarce. METHODS AND RESULTS: We studied 93 patients undergoing ablation for paroxysmal atrial fibrillation (AF) (n = 63) or non-paroxysmal AF (n = 30). Femoral venous, left and right atrial, and coronary sinus blood were analysed using ELISA to determine biomarker levels. Levels were compared with control patients (n = 36) and baseline characteristics, including left atrial voltage mapping data. C-telopeptide of type I collagen levels were higher in AF than in non-AF patients (P = 0.007). Peripheral ICTP levels were higher than all intra-cardiac levels (P < 0.001). Peripheral gal-3 levels were higher than left atrial levels (P = 0.001). Peripheral levels of FGF-23 and PIIINP were not significantly different from intra-cardiac levels. CS levels of ICTP were higher than right and left atrial levels (P < 0.001). gal-3 was higher in women vs. men (P ≤ 0.001) and with higher body mass index (P ≤ 0.001). ICTP levels increased with reducing ejection fraction (P ≤ 0.012). CONCLUSIONS: Atrial fibrillation patients have higher levels of circulating ICTP than matched non-AF controls. In AF ablation patients, intra-cardiac sampling of FGF-23 or PIIINP gives no further information over peripheral sampling. For gal-3 and ICTP, intra-cardiac sampling may be necessary to assess their association with intra-cardiac processes. None of the biomarkers is related to fibrosis assessed by left atrial voltage.

Periprocedural stroke risk in patients undergoing catheter ablation for atrial fibrillation on uninterrupted warfarin.

BACKGROUND: Catheter ablation is an effective treatment for symptomatic individuals with atrial fibrillation (AF) but is associated with a risk of periprocedual stroke. Recent data suggest that this risk may be abolished if catheter ablation is performed with uninterrupted warfarin (UW). We sought to compare the incidence, severity and timing of periprocedural stroke between 2 periprocedural anticoagulation protocols: bridging low-molecular-weight heparin (LMWH) and UW. METHODS AND RESULTS: Periprocedural stroke (≤14 days) was assessed in 2,855 ablations performed in 1,813 patients. Thromboembolic stroke occurred in 11/1,653 (0.7%) procedures with bridging LMWH and in 5/1,202 (0.4%) procedures on UW (P = 0.5). Four of the 5 strokes (80%) on UW occurred despite a therapeutic INR and a mean activated clotting time of ≥300 seconds and 4/5 strokes (80%) occurred in patients with a CHADS2 score of 0. Eleven of 16 (69%) strokes overall occurred within 24 hours of the procedure. All 4 strokes resulting in major neurological deficit occurred in the LMWH group. Major bleeding complications occurred in 6.0% of patients in the bridging LMWH group compared to 4.0% in the UW group (P = 0.02). CONCLUSIONS: In contrast to existing data, periprocedural stroke still occurs despite therapeutic anticoagulation throughout the operative period. The optimal strategy to protect patients against thromboembolic stroke remains unclear.

Ischemic ventricular tachycardia presenting as a narrow complex tachycardia.

This report describes a patient presenting with a narrow complex tachycardia in the context of prior myocardial infarction and impaired ventricular function. Electrophysiological studies confirmed ventricular tachycardia and activation and entrainment mapping demonstrated a critical isthmus within an area of scar involving the His-Purkinje system accounting for the narrow QRS morphology. This very rare case shares some similarities with upper septal ventricular tachycardia seen in patients with structurally normal hearts, but to our knowledge has not been seen previously in patients with ischemic heart disease.

Mode and Characteristics of Arrhythmia Initiation in Idiopathic Ventricular Fibrillation: A THESIS Substudy.

BACKGROUND: There is limited information on the mode of arrhythmia initiation in idiopathic ventricular fibrillation (IVF). A non-pause-dependent mechanism has been suggested to be the rule. OBJECTIVES: The aim of this study was to assess the mode and characteristics of initiation of polymorphic ventricular tachycardia (PVT) in patients with short or long-coupled PVT/IVF included in THESIS (THerapy Efficacy in Short or long-coupled idiopathic ventricular fibrillation: an International Survey), a multicenter study involving 287 IVF patients treated with drugs or radiofrequency ablation. METHODS: We reviewed the initiation of 410 episodes of ≥1 PVT triplet in 180 patients (58.3% females; age 39.6 ± 13.6 years) with IVF. The incidence of pause-dependency arrhythmia initiation (prolongation by >20 ms of the preceding cycle length) was assessed. RESULTS: Most arrhythmias (n = 295; 72%) occurred during baseline supraventricular rhythm without ambient premature ventricular complexes (PVCs), whereas 106 (25.9%) occurred during baseline rhythm including PVCs. Nine (2.2%) arrhythmias occurred during atrial/ventricular pacing and were excluded from further analysis. Mode of PVT initiation was pause-dependent in 45 (15.6%) and 64 (60.4%) of instances in the first and second settings, respectively, for a total of 109 of 401 (27.2%). More than one type of pause-dependent and/or non-pause-dependent initiation (mean: 2.6) occurred in 94.4% of patients with ≥4 events. Coupling intervals of initiating PVCs were <350 ms, 350-500 ms, and >500 ms in 76.6%, 20.72%, and 2.7% of arrhythmia initiations, respectively. CONCLUSIONS: Pause-dependent initiation occurred in more than a quarter of arrhythmic episodes in IVF patients. PVCs having long (between 350 and 500 ms) and very long (>500 ms) coupling intervals were observed at the initiation of nearly a quarter of PVT episodes.

Epicardial catheter ablation for ventricular tachycardia in heparinized patients.

AIMS: In patients undergoing epicardial catheter ablation of ventricular tachycardia (VT), current guidelines recommend obtaining pericardial access prior to heparinization to minimize bleeding complications. Consequently, access is obtained before endocardial mapping (leading to unnecessary punctures) or during an additional procedure. We present our experience of obtaining pericardial access during the index procedure in heparinized patients. METHODS AND RESULTS: Patients undergoing catheter ablation of VT in whom pericardial access was performed after heparinization were included. Clinical and procedural data and complications were recorded. Electrocardiograms (ECGs) were analysed for published criteria suggesting an epicardial ablation target and compared with patients (matched for substrate) undergoing successful endocardial ablation. Seventeen patients (13 males, age 58 ± 16 years, 8 (47%) ischaemic) were evaluated. Pericardial access was achieved in 16 (94%), including 2 patients with prior epicardial ablation. The mean activated clotting time was 273 ± 36 s. No bleeding complications occurred. In three patients, inadvertent puncture of the right ventricle caused no adverse consequences. An epicardial ablation target was found in nine of which three (33%) had ECG criteria, suggesting an epicardial circuit. In comparison 5 of 17 patients undergoing successful endocardial ablation had at least one ECG criterion suggesting an epicardial ablation target. CONCLUSION: Obtaining pericardial access for epicardial catheter ablation for VT appears to be safe in heparinized patients. Electrocardiogram criteria suggesting an epicardial ablation target lack the sensitivity and specificity accurately to predict which patients might need epicardial ablation. Performing pericardial access in heparinized patients therefore may reduce unnecessary punctures and reduce the number of additional procedures in some patients.

Improved electrogram attenuation during ablation of paroxysmal atrial fibrillation with the Hansen robotic system.

BACKGROUND: Robotic catheter ablation aims to improve outcomes after ablation of atrial fibrillation (AF) through improved lesion quality. This study examined electrogram attenuation as a measure of efficacy in response to robotic (ROB) and manual (MAN) ablation. METHODS: Patients with paroxysmal AF undergoing ablation as part of an ongoing randomized controlled trial were studied (Clinical Trials Registration NCT01037296). Patients underwent pulmonary vein isolation using NavX (St. Jude Medical, St. Paul, MN, USA). Patients were randomized to MAN or ROB catheter ablation using a 3.5-mm irrigated-tip catheter with standardized ablation settings. Bipolar electrogram voltage was measured at 0, 5, 10, 20, and 30 seconds after ablation onset. Distance from ablation lesion to the left atrial surface on NavX were calculated. RESULTS: Similar ablation energy was delivered in ROB and MAN groups, achieving comparable rates of PV isolation (100% vs 98%). The bipolar voltages of 4,434 electrograms from 303 ablation lesions (146 ROB, 157 MAN) were measured. At 30 seconds, signal attenuation was greater in the ROB group than MAN (mean 65 ± 4% vs 55 ± 4% of baseline voltage, P < 0.01). A total of 2,064 NavX ablation lesions were assessed (906 ROB and 1,158 MAN). ROB lesions were on average 0.52 mm further inside the geometry than MAN (P < 0.0001). CONCLUSIONS: Robotic ablation results in greater signal attenuation in man. This is achieved despite manual lesions being closer to the left atrial surface. Catheter stability and constant energy delivery may be key to achieving signal attenuation, rather than increased contact force.

Catheter ablation for atrial fibrillation on uninterrupted warfarin: can it be done without echo guidance?

INTRODUCTION: Catheter ablation for atrial fibrillation is an effective treatment for symptomatic patients who have failed drug therapy. Recent studies using intracardiac echocardiography have demonstrated that ablation can be performed safely on uninterrupted warfarin and may be superior to bridging low molecular weight heparin (LMWH). We sought to assess the safety of an uninterrupted warfarin protocol using a simplified ablation protocol in a prospective controlled study. METHODS: Two anticoagulation regimes for patients undergoing catheter ablation for atrial fibrillation were evaluated--a bridging LMWH group and an uninterrupted warfarin group. Bleeding complications were compared between the 2 groups. RESULTS: In total 198 patients were evaluated (109 bridging LMWH, 89 uninterrupted warfarin). The preprocedure INR in the LMWH group (mean age 60.6 years, 72% male) was 1.2 ± 0.3 compared to 2.3 ± 0.5 in the uninterrupted warfarin group (mean age 60.9 years, 69% male). The primary outcome (a composite of major and minor bleeding complications) was observed in 78% in the LMWH group compared to 56% in the warfarin group (P = 0.001), mainly due to increased pain at the venous access site (41% vs 16%, P = 0.001). Two patients undergoing ablation on warfarin required pericardiocentesis for cardiac tamponade. Drug costs were lower in the warfarin group ($64.77 ± 31.86 vs $20.76 ± 15.60, P = 0.005), but the overall cost of treatment per patient (including bed occupancy costs) was similar in the LMWH group compared to the warfarin group ($883.96 ± 278.78 vs $816.59 ± 182.72, P = 0.06). CONCLUSION: Catheter ablation for atrial fibrillation can be performed safely on uninterrupted warfarin without intracardiac echocardiography, with a reduced risk of bleeding complications.

SCN5A Mutation Type and a Genetic Risk Score Associate Variably With Brugada Syndrome Phenotype in SCN5A Families.

BACKGROUND: Brugada syndrome (BrS) is characterized by the type 1 Brugada ECG pattern. Pathogenic rare variants in SCN5A (mutations) are identified in 20% of BrS families in whom incomplete penetrance and genotype-negative phenotype-positive individuals are observed. E1784K-SCN5A is the most common SCN5A mutation identified. We determined the association of a BrS genetic risk score (BrS-GRS) and SCN5A mutation type on BrS phenotype in BrS families with SCN5A mutations. METHODS: Subjects with a spontaneous type 1 pattern or positive/negative drug challenge from cohorts harboring SCN5A mutations were recruited from 16 centers (n=312). Single nucleotide polymorphisms previously associated with BrS at genome-wide significance were studied in both cohorts: rs11708996, rs10428132, and rs9388451. An additive linear genetic model for the BrS-GRS was assumed (6 single nucleotide polymorphism risk alleles). RESULTS: In the total population (n=312), BrS-GRS ≥4 risk alleles yielded an odds ratio of 4.15 for BrS phenotype ([95% CI, 1.45-11.85]; P=0.0078). Among SCN5A-positive individuals (n=258), BrS-GRS ≥4 risk alleles yielded an odds ratio of 2.35 ([95% CI, 0.89-6.22]; P=0.0846). In SCN5A-negative relatives (n=54), BrS-GRS ≥4 alleles yielded an odds ratio of 22.29 ([95% CI, 1.84-269.30]; P=0.0146). Among E1784K-SCN5A positive family members (n=79), hosting ≥4 risk alleles gave an odds ratio=5.12 ([95% CI, 1.93-13.62]; P=0.0011). CONCLUSIONS: Common genetic variation is associated with variable expressivity of BrS phenotype in SCN5A families, explaining in part incomplete penetrance and genotype-negative phenotype-positive individuals. SCN5A mutation genotype and a BrS-GRS associate with BrS phenotype, but the strength of association varies according to presence of a SCN5A mutation and severity of loss of function.

Multicentre randomised trial comparing contact force with electrical coupling index in atrial flutter ablation (VERISMART trial).

INTRODUCTION: Electrical coupling index (ECI) and contact force (CF) have been developed to aid lesion formation during catheter ablation. ECI measures tissue impedance and capacitance whilst CF measures direct contact. The aim was to determine whether the presence of catheter / tissue interaction information, such as ECI and CF, reduce time to achieve bidirectional cavotricuspid isthmus block during atrial flutter (AFL) ablation. METHODS: Patients with paroxysmal or persistent AFL were randomised to CF visible (range 5-40g), CF not visible, ECI visible (change of 12%) or ECI not visible. Follow-up occurred at 3 and 6 months and included a 7 day ECG recording. The primary endpoint was time to bidirectional cavotricuspid isthmus block. RESULTS: 114 patients were randomised, 16 were excluded. Time to bidirectional block was significantly shorter when ECI was visible (median 30.0 mins (IQR 31) to median 10.5mins (IQR 12) p 0.023) versus ECI not visible. There was a trend towards a shorter time to bidirectional block when CF was visible. Higher force was applied when CF was visible (median 9.03g (IQR 7.4) vs. 11.3g (5.5) p 0.017). There was no difference in the acute recurrence of conduction between groups. The complication rate was 2%, AFL recurrence was 1.1% and at 6 month follow-up, 12% had atrial fibrillation. CONCLUSION: The use of tissue contact information during AFL ablation was associated with reduced time taken to achieve bidirectional block when ECI was visible. Contact force data improved contact when visible with a trend towards a reduction in the procedural endpoint. ClinicalTrials.gov trial identifier: NCT02490033.

Micro-exons of the cardiac myosin binding protein C gene: flanking introns contain a disproportionately large number of hypertrophic cardiomyopathy mutations.

Hypertrophic cardiomyopathy is primarily caused by mutations in genes encoding cardiac sarcomere proteins. Large screening studies identify mutations in 35-65% of the diagnosed patients and 15-30% of these are discovered within the MYBPC3 gene encoding the cardiac myosin binding protein C. The aim of this study is to determine whether intronic variation flanking the three micro-exons in MYBPC3 is disease-causing. Two hundred and fifty unrelated patients with hypertrophic cardiomyopathy were genotyped in MYBPC3, using automated single-strand conformation polymorphism, and sequenced for confirmation. Mutations located in the flanking introns of the MYBPC3 micro-exons were examined using in silico methods. Ectopic expression of mRNA in blood leukocytes in the respective patients was examined using reverse transcription-PCR. A total of seven mutations were discovered in the introns flanking the two micro-exons 10 and 14, but none were found in introns flanking exon 11. Functional studies together with co-segregation analysis indicate that four mutations are associated with HCM, in the respective patients. All four mutations result in premature termination codons, which suggests that haploinsufficiency is a pathogenic mechanism of this type of mutation. It is demonstrated that the use of in silico methods together with RNA studies on peripheral blood leukocytes is a useful tool to evaluate the potential effects of mutations on pre-mRNA splicing.

Left atrial voltage, circulating biomarkers of fibrosis, and atrial fibrillation ablation. A prospective cohort study.

AIMS: To test the ability of four circulating biomarkers of fibrosis, and of low left atrial voltage, to predict recurrence of atrial fibrillation after catheter ablation. BACKGROUND: Circulating biomarkers potentially may be used to improve patient selection for atrial fibrillation ablation. Low voltage areas in the left atrium predict arrhythmia recurrence when mapped in sinus rhythm. This study tested type III procollagen N terminal peptide (PIIINP), galectin-3 (gal-3), fibroblast growth factor 23 (FGF-23), and type I collagen C terminal telopeptide (ICTP), and whether low voltage areas in the left atrium predicted atrial fibrillation recurrence, irrespective of the rhythm during mapping. METHODS: 92 atrial fibrillation ablation patients were studied. Biomarker levels in peripheral and intra-cardiac blood were measured with enzyme-linked immunosorbent assay. Low voltage (<0.5mV) was expressed as a proportion of the mapped left atrial surface area. Follow-up was one year. The primary endpoint was recurrence of arrhythmia. The secondary endpoint was a composite of recurrence despite two procedures, or after one procedure if no second procedure was undertaken. RESULTS: The biomarkers were not predictive of either endpoint. After multivariate Cox regression analysis, high proportion of low voltage area in the left atrium was found to predict the primary endpoint in sinus rhythm mapping (hazard ratio 4.323, 95% confidence interval 1.337-13.982, p = 0.014) and atrial fibrillation mapping (hazard ratio 5.195, 95% confidence interval 1.032-26.141, p = 0.046). This effect was also apparent for the secondary endpoint. CONCLUSION: The studied biomarkers do not predict arrhythmia recurrence after catheter ablation. Left atrial voltage is an independent predictor of recurrence, whether the left atrium is mapped in atrial fibrillation or sinus rhythm.

Role of T1 Mapping in Inherited Cardiomyopathies.

T1 mapping by cardiovascular magnetic resonance is a rapidly evolving method for the quantitative assessment of tissue characteristics in cardiac disease. The myocardial T1 time can be measured without contrast (native T1) or following the administration of intravenous gadolinium-based contrast agent (post-contrast T1). By combining both of these measures, the myocardial extracellular volume fraction can be approximated. This value has been validated histologically in various inherited cardiomyopathies. Due to overlapping phenotypes, the diagnosis of inherited cardiomyopathy can at times be challenging. In this article we discuss when T1 mapping may be a useful tool in the differential diagnosis of cardiomyopathy. We also present evidence of when T1 mapping provides incremental risk stratification over other biomarkers.