Imperial College London

Dr Francesco Mazzarotto

Faculty of MedicineNational Heart & Lung Institute

Honorary Research Associate
 
 
 
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Contact

 

+44 (0)20 7352 8121 ext 3009f.mazzarotto

 
 
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Location

 

2058Sydney StreetRoyal Brompton Campus

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Summary

 

Publications

Publication Type
Year
to

47 results found

Walsh R, Adler A, Amin AS, Abiusi E, Care M, Bikker H, Amenta S, Feilotter H, Nannenberg EA, Mazzarotto F, Trevisan V, Garcia J, Hershberger RE, Perez MV, Sturm AC, Ware JS, Zareba W, Novelli V, Wilde AAM, Gollob MHet al., 2021, Evaluation of gene validity for CPVT and short QT syndrome in sudden arrhythmic death, European Heart Journal, ISSN: 0195-668X

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Aims</jats:title> <jats:p>Catecholaminergic polymorphic ventricular tachycardia (CPVT) and short QT syndrome (SQTS) are inherited arrhythmogenic disorders that can cause sudden death. Numerous genes have been reported to cause these conditions, but evidence supporting these gene–disease relationships varies considerably. To ensure appropriate utilization of genetic information for CPVT and SQTS patients, we applied an evidence-based reappraisal of previously reported genes.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods and results</jats:title> <jats:p>Three teams independently curated all published evidence for 11 CPVT and 9 SQTS implicated genes using the ClinGen gene curation framework. The results were reviewed by a Channelopathy Expert Panel who provided the final classifications. Seven genes had definitive to moderate evidence for disease causation in CPVT, with either autosomal dominant (RYR2, CALM1, CALM2, CALM3) or autosomal recessive (CASQ2, TRDN, TECRL) inheritance. Three of the four disputed genes for CPVT (KCNJ2, PKP2, SCN5A) were deemed by the Expert Panel to be reported for phenotypes that were not representative of CPVT, while reported variants in a fourth gene (ANK2) were too common in the population to be disease-causing. For SQTS, only one gene (KCNH2) was classified as definitive, with three others (KCNQ1, KCNJ2, SLC4A3) having strong to moderate evidence. The majority of genetic evidence for SQTS genes was derived from very few variants (five in KCNJ2, two in KCNH2, one in KCNQ1/SLC4A3).</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Seven CPVT and four SQTS genes have valid

Journal article

Smole T, Zunkovic B, Piculin M, Kokalj E, Robnik-Sikonja M, Kukar M, Fotiadis D, Pezoulas VC, Tachos NS, Barlocco F, Mazzarotto F, Popovic D, Maier L, Velicki L, MacGowan GA, Olivotto I, Filipovic N, Jakovljevic DG, Bosnic Zet al., 2021, A machine learning-based risk stratification model for ventricular tachycardia and heart failure in hypertrophic cardiomyopathy, COMPUTERS IN BIOLOGY AND MEDICINE, Vol: 135, ISSN: 0010-4825

Journal article

Finocchiaro G, Sheikh N, Leone O, Westaby J, Mazzarotto F, Pantazis A, Ferrantini C, Sacconi L, Papadakis M, Sharma S, Sheppard MN, Olivotto Iet al., 2021, Arrhythmogenic potential of myocardial disarray in hypertrophic cardiomyopathy: genetic basis, functional consequences and relation to sudden cardiac death., Europace, Vol: 23, Pages: 985-995

Myocardial disarray is defined as disorganized cardiomyocyte spatial distribution, with loss of physiological fibre alignment and orientation. Since the first pathological descriptions of hypertrophic cardiomyopathy (HCM), disarray appeared as a typical feature of this condition and sparked vivid debate regarding its specificity to the disease and clinical significance as a diagnostic marker and a risk factor for sudden death. Although much of the controversy surrounding its diagnostic value in HCM persists, it is increasingly recognized that myocardial disarray may be found in physiological contexts and in cardiac conditions different from HCM, raising the possibility that central focus should be placed on its quantity and distribution, rather than a mere presence. While further studies are needed to establish what amount of disarray should be considered as a hallmark of the disease, novel experimental approaches and emerging imaging techniques for the first time allow ex vivo and in vivo characterization of the myocardium to a molecular level. Such advances hold the promise of filling major gaps in our understanding of the functional consequences of myocardial disarray in HCM and specifically on arrhythmogenic propensity and as a risk factor for sudden death. Ultimately, these studies will clarify whether disarray represents a major determinant of the HCM clinical profile, and a potential therapeutic target, as opposed to an intriguing but largely innocent bystander.

Journal article

Simoes Monteiro de Marvao A, McGurk K, Zheng S, Thanaj M, Bai W, Duan J, Biffi C, Mazzarotto F, Statton B, Dawes T, Savioli N, Halliday B, Xu X, Buchan R, Baksi A, Quinlan M, Tokarczuk P, Tayal U, Francis C, Whiffin N, Theotokis A, Zhang X, Jang M, Berry A, Pantazis A, Barton P, Rueckert D, Prasad S, Walsh R, Ho C, Cook S, Ware J, O'Regan Det al., 2021, Phenotypic expression and outcomes in individuals with rare genetic variants of hypertrophic cardiomyopathy, Journal of the American College of Cardiology, ISSN: 0735-1097

Background: Hypertrophic cardiomyopathy (HCM) is caused by rare variants in sarcomereencoding genes, but little is known about the clinical significance of these variants in thegeneral population.Objectives: To compare lifetime outcomes and cardiovascular phenotypes according to thepresence of rare variants in sarcomere-encoding genes amongst middle-aged adults.Methods: We analysed whole exome sequencing and cardiac magnetic resonance (CMR)imaging in UK Biobank participants stratified by sarcomere-encoding variant status.Results: The prevalence of rare variants (allele frequency <0.00004) in HCM-associatedsarcomere-encoding genes in 200,584 participants was 2.9% (n=5,712; 1 in 35), and theprevalence of variants pathogenic or likely pathogenic for HCM (SARC-HCM-P/LP) was0.25% (n=493, 1 in 407). SARC-HCM-P/LP variants were associated with increased risk ofdeath or major adverse cardiac events compared to controls (HR 1.69, 95% CI 1.38 to 2.07,p<0.001), mainly due to heart failure endpoints (HR 4.23, 95% CI 3.07 to 5.83, p<0.001). In21,322 participants with CMR, SARC-HCM-P/LP were associated with asymmetric increasein left ventricular maximum wall thickness (10.9±2.7 vs 9.4±1.6 mm, p<0.001) buthypertrophy (≥13mm) was only present in 18.4% (n=9/49, 95% CI 9 to 32%). SARC-HCMP/LP were still associated with heart failure after adjustment for wall thickness (HR 6.74,95% CI 2.43 to 18.7, p<0.001).Conclusions: In this population of middle-aged adults, SARC-HCM-P/LP variants have lowaggregate penetrance for overt HCM but are associated with increased risk of adversecardiovascular outcomes and an attenuated cardiomyopathic phenotype. Although absoluteevent rates are low, identification of these variants may enhance risk stratification beyondfamilial disease.

Journal article

Jordan E, Peterson L, Ai T, Asatryan B, Bronicki L, Brown E, Celeghin R, Edwards M, Fan J, Ingles J, James CA, Jarinova O, Johnson R, Judge DP, Lahrouchi N, Lekanne Deprez RH, Lumbers RT, Mazzarotto F, Medeiros Domingo A, Miller RL, Morales A, Murray B, Peters S, Pilichou K, Protonotarios A, Semsarian C, Shah P, Syrris P, Thaxton C, van Tintelen JP, Walsh R, Wang J, Ware J, Hershberger REet al., 2021, An evidence-based assessment of genes in dilated cardiomyopathy, Circulation, Vol: 144, Pages: 7-19, ISSN: 0009-7322

Background: The cardiomyopathies, classically categorized as hypertrophic (HCM), dilated (DCM), and arrhythmogenic right ventricular (ARVC), each have a signature genetic theme. HCM and ARVC are largely understood as genetic diseases of sarcomere or desmosome proteins, respectively. In contrast, >250 genes spanning more than 10 gene ontologies have been implicated in DCM, representing a complex and diverse genetic architecture. To clarify this, a systematic curation of evidence to establish the relationship of genes with DCM was conducted.Methods: An international Panel with clinical and scientific expertise in DCM genetics evaluated evidence supporting monogenic relationships of genes with idiopathic DCM. The Panel utilized the ClinGen semi-quantitative gene-disease clinical validity classification framework with modifications for DCM genetics to classify genes into categories based on the strength of currently available evidence. Representation of DCM genes on clinically available genetic testing panels was evaluated.Results: Fifty-one genes with human genetic evidence were curated. Twelve genes (23%) from eight gene ontologies were classified as having definitive (BAG3, DES, FLNC, LMNA, MYH7, PLN, RBM20, SCN5A, TNNC1, TNNT2, TTN) or strong (DSP) evidence. Seven genes (14%) (ACTC1, ACTN2, JPH2, NEXN, TNNI3, TPM1, VCL) including two additional ontologies were classified as moderate evidence; these genes are likely to emerge as strong or definitive with additional evidence. Of these 19 genes, six were similarly classified for HCM and three for ARVC. Of the remaining 32 genes (63%), 25 (49%) had limited evidence, 4 (8%) were disputed, 2 (4%) had no disease relationship, and 1 (2%) was supported by animal model data only. Of 16 evaluated clinical genetic testing panels, most definitive genes were included, but panels also included numerous genes with minimal human evidence.Conclusions: In the curation of 51 genes, 19 had high evidence (12 definitive/strong; seven m

Journal article

Thompson AD, Helms AS, Kannan A, Yob J, Lakdawala NK, Wittekind SG, Pereira AC, Jacoby DL, Colan SD, Ashley EA, Saberi S, Ware JS, Ingles J, Semsarian C, Michels M, Mazzarotto F, Olivotto I, Ho CY, Day SMet al., 2021, Computational prediction of protein subdomain stability in MYBPC3 enables clinical risk stratification in hypertrophic cardiomyopathy and enhances variant interpretation, Genetics in Medicine, Vol: 23, Pages: 1281-1287, ISSN: 1098-3600

Purpose: Variants in MYBPC3 causing loss of function are the most common cause of hypertrophic cardiomyopathy (HCM). However, a substantial number of patients carry missense variants of uncertain significance (VUS) in MYBPC3. We hypothesize that a structural-based algorithm, STRUM, which estimates the effect of missense variants on protein folding, will identify a subgroup of HCM patients with a MYBPC3 VUS associated with increased clinical risk.Methods: Among 7,963 patients in the multicenter Sarcomeric Human Cardiomyopathy Registry (SHaRe), 120 unique missense VUS in MYBPC3 were identified. Variants were evaluated for their effect on subdomain folding and a stratified time-to-event analysis for an overall composite endpoint (first occurrence of ventricular arrhythmia, heart failure, all-cause mortality, atrial fibrillation, and stroke) was performed for patients with HCM and a MYBPC3 missense VUS.Results: We demonstrated that patients carrying a MYBPC3 VUS predicted to cause subdomain misfolding (STRUM+, ΔΔG ≤ −1.2 kcal/mol) exhibited a higher rate of adverse events compared with those with a STRUM- VUS (hazard ratio = 2.29, P = 0.0282). In silico saturation mutagenesis of MYBPC3 identified 4,943/23,427 (21%) missense variants that were predicted to cause subdomain misfolding.Conclusion: STRUM identifies patients with HCM and a MYBPC3 VUS who may be at higher clinical risk and provides supportive evidence for pathogenicity.

Journal article

Mazzarotto F, Hawley MH, Beltrami M, Beekman L, De Marvao A, McGurk K, Statton B, Boschi B, Girolami F, Roberts AM, Lodder EM, Allouba M, Romeih S, Aguib Y, Baksi J, Pantazis A, Prasad SK, Cerbai E, Yacoub M, O'Regan D, Cook S, Ware J, Funke B, Olivotto I, Bezzina C, Barton P, Walsh Ret al., 2021, Systematic large-scale assessment of the genetic architecture of left ventricular non-compaction reveals diverse aetiologies, Genetics in Medicine, Vol: 23, Pages: 856-864, ISSN: 1098-3600

Purpose: To characterise the genetic architecture of left ventricular non-compaction (LVNC) and investigate the extent to which it may represent a distinct pathology or a secondary phenotype associated with other cardiac diseases.Methods: We performed rare variant association analysis with 840 LVNC cases and 125,748 gnomAD population controls, and compared results to similar analyses on dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Results: We observed substantial genetic overlap indicating that LVNC often represents a phenotypic variation of DCM or HCM. In contrast, truncating variants (TV) in MYH7, ACTN2 and PRDM16 were uniquely associated with LVNC and may reflect a distinct LVNC aetiology. In particular, MYH7 TV, generally considered non-pathogenic for cardiomyopathies, were 20-fold enriched in LVNC cases over controls. MYH7 TV heterozygotes identified in the UK Biobank and healthy volunteer cohorts also displayed significantly greater non-compaction compared to matched controls. RYR2 exon deletions and HCN4 transmembrane variants were also enriched in LVNC, supporting prior reports of association with arrhythmogenic LVNC phenotypes.Conclusions: LVNC is characterised by substantial genetic overlap with DCM/HCM but is also associated with distinct non-compaction and arrhythmia aetiologies. These results will enable enhanced application of LVNC genetic testing and help to distinguish pathological from physiological non-compaction.

Journal article

de Marvao A, McGurk KA, Zheng SL, Thanaj M, Bai W, Duan J, Biffi C, Mazzarotto F, Statton B, Dawes TJW, Savioli N, Halliday BP, Xu X, Buchan RJ, Baksi AJ, Quinlan M, Tokarczuk P, Tayal U, Francis C, Whiffin N, Theotokis PI, Zhang X, Jang M, Berry A, Pantazis A, Barton PJR, Rueckert D, Prasad SK, Walsh R, Ho CY, Cook SA, Ware JS, ORegan DPet al., 2021, Outcomes and phenotypic expression of rare variants in hypertrophic cardiomyopathy genes amongst UK Biobank participants, Publisher: Cold Spring Harbor Laboratory

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Hypertrophic cardiomyopathy (HCM) is caused by rare variants in sarcomere-encoding genes, but little is known about the clinical significance of these variants in the general population.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We compared outcomes and cardiovascular phenotypes in UK Biobank participants with whole exome sequencing stratified by sarcomere-encoding variant status.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The prevalence of rare variants (allele frequency &lt;0.00004) in HCM-associated sarcomere-encoding genes in 200,584 participants was 2.9% (n=5,727; 1 in 35), of which 0.24% (n=474, 1 in 423) were pathogenic or likely pathogenic variants (SARC-P/LP). SARC-P/LP variants were associated with increased risk of death or major adverse cardiac events compared to controls (HR 1.68, 95% CI 1.37-2.06, p&lt;0.001), mainly due to heart failure (HR 4.40, 95% CI 3.22-6.02, p&lt;0.001) and arrhythmia (HR 1.55, 95% CI 1.18-2.03, p=0.002). In 21,322 participants with cardiac magnetic resonance imaging, SARC-P/LP were associated with increased left ventricular maximum wall thickness (10.9±2.7 vs 9.4±1.6 mm, p&lt;0.001) and concentric remodelling (mass/volume ratio: 0.63±0.12 vs 0.58±0.09 g/mL, p&lt;0.001), but hypertrophy (≥13mm) was only present in 16% (n=7/43, 95% CI 7-31%). Other rare sarcomere-encoding variants had a weak effect on wall thickness (9.5±1.7 vs 9.4±1.6 mm, p=0.002) with no combined excess cardiovascular risk (HR 1.00 95% CI 0.92-1.08, p=0.9).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>In the general population, SARC-P/LP variants have low aggregate penetrance for overt HCM bu

Working paper

Ware J, Tadros R, Francis C, Xu X, Matthews P, watkins H, Bezzina Cet al., 2021, Shared genetic pathways contribute to risk of hypertrophic and dilated cardiomyopathies with opposite directions of effect, Nature Genetics, Vol: 53, Pages: 128-134, ISSN: 1061-4036

The heart muscle diseases hypertrophic (HCM) and dilated (DCM) cardiomyopathies are leading causes of sudden death and heart failure in young otherwise healthy individuals. We conducted genome-wide association studies (GWAS) and multi-trait analyses in HCM (1,733 cases), DCM (5,521 cases), and nine left ventricular (LV) traits in 19,260 UK Biobank participants with structurally-normal hearts. We identified 16 loci associated with HCM, 13 with DCM, and 23 with LV traits. We show strong genetic correlations between LV traits and cardiomyopathies, with opposing effects in HCM and DCM. Two-sample Mendelian randomization supports a causal association linking increased contractility with HCM risk. A polygenic risk score (PRS) explains a significant portion of phenotypic variability in carriers of HCM-causing rare variants. Our findings thus provide evidence that PRS may account for variability in Mendelian diseases. More broadly, we provide insights into how genetic pathways may lead to distinct disorders through opposing genetic effects.

Journal article

Zhang X, Walsh R, Whiffin N, Buchan R, Midwinter W, Wilk A, Govind R, Li N, Ahmad M, Mazzarotto F, Roberts A, Theotokis P, Mazaika E, Allouba M, de Marvao A, Pua CJ, Day SM, Ashley E, Colan SD, Michels M, Pereira AC, Jacoby D, Ho CY, Olivotto I, Gunnarsson GT, Jefferies J, Semsarian C, Ingles J, ORegan DP, Aguib Y, Yacoub MH, Cook SA, Barton PJR, Bottolo L, Ware JSet al., 2021, Disease-specific variant pathogenicity prediction significantly improves variant interpretation in inherited cardiac conditions, Genetics in Medicine, Vol: 23, Pages: 69-79, ISSN: 1098-3600

Background: Accurate discrimination of benign and pathogenic rare variation remains a priority for clinical genome interpretation. State-of-the-art machine learning tools are useful for genome-wide variant prioritisation but remain imprecise. Since the relationship between molecular consequence and likelihood of pathogenicity varies between genes with distinct molecular mechanisms, we hypothesised that a disease-specific classifier may outperform existing genome-wide tools. Methods: We present a novel disease-specific variant classification tool, CardioBoost, that estimates the probability of pathogenicity for rare missense variants in inherited cardiomyopathies and arrhythmias, trained with variants of known clinical effect. To benchmark against state-of-the-art genome-wide pathogenicity classification tools, we assessed classification of hold-out test variants using both overall performance metrics, and metrics of high-confidence (&gt;90%) classifications relevant to variant interpretation. We further evaluated the prioritisation of variants associated with disease and patient clinical outcomes, providing validations that are robust to potential mis-classification in gold-standard reference datasets.Results: CardioBoost has higher discriminating power than published genome-wide variant classification tools in distinguishing between pathogenic and benign variants based on overall classification performance measures with the highest area under the Precision-Recall Curve as 91% for cardiomyopathies and as 96% for inherited arrhythmias. When assessed at high-confidence (&gt;90%) classification thresholds, prediction accuracy is improved by at least 120% over existing tools for both cardiomyopathies and arrhythmias, with significantly improved sensitivity and specificity. Finally, CardioBoost improves prioritisation of variants significantly associated with disease, and stratifies survival of patients with cardiomyopathies, confirming biologically relevant vari

Journal article

Walsh R, Lahrouchi N, Glinge C, Krijger C, Skoric-Milosavljevic D, Whiffin N, Mazzarotto F, Ware JS, Tadros R, Bezzina CRet al., 2020, Enhancing rare variant interpretation in inherited arrhythmias through quantitative analysis of 5182 cases from long QT syndrome and Brugada syndrome consortia cohorts and gnomAD population controls, Publisher: SPRINGERNATURE, Pages: 63-63, ISSN: 1018-4813

Conference paper

Thompson AD, Helms AS, Kannan A, Yob J, Lakdawala NK, Wittekind S, Pereira AD, Jacoby DL, Colan SD, Saberi S, Ware JS, Ingles J, Semsarian C, Michels M, Mazzarotto F, Olivotto I, Ho C, Day Set al., 2020, Computational Prediction of Protein Subdomain Stability as a Novel Approach to Cardiac Myosin Binding ProteinC Variant Adjudication and Clinical Risk Stratification in Hypertrophic Cardiomyopathy, Publisher: LIPPINCOTT WILLIAMS & WILKINS, ISSN: 0009-7322

Conference paper

Walsh R, Lahrouchi N, Glinge C, Krijger C, Skoric-Milosavljevic D, Whiffin N, Mazzarotto F, Ware J, Tadros R, Bezzina Cet al., 2020, Enhancing rare variant interpretation in inherited arrhythmias through quantitative analysis of 5182 cases from long QT syndrome and Brugada syndrome consortia cohorts and gnomAD population controls, Publisher: OXFORD UNIV PRESS, Pages: 3686-3686, ISSN: 0195-668X

Conference paper

Walsh R, Mazzarotto F, Hawley M, Beltrami M, Beekman L, Boschi B, Girolami E, Roberts A, Cerbai E, Cook S, Ware J, Funkel B, Olivotto I, Bezzina C, Barton Pet al., 2020, The genetic architecture of left ventricular non-compaction reveals both substantial overlap with other cardiomyopathies and a distinct aetiology in a subset of cases, Publisher: OXFORD UNIV PRESS, Pages: 3715-3715, ISSN: 0195-668X

Conference paper

Canepa M, Fumagalli C, Tini G, Vincent-Tompkins J, Day SM, Ashley EA, Mazzarotto F, Ware J, Michels M, Jacoby M, Ho CY, Olivotto I, The SHaRe Investigatorset al., 2020, Temporal trend of age at diagnosis in hypertrophic cardiomyopathy: an analysis of the international SHaRe Registry, Circulation, Vol: 13, Pages: 376-381, ISSN: 0009-7322

BACKGROUNDOver the last 50 years, the epidemiology of hypertrophic cardiomyopathy (HCM) has changed dueto increased awareness and availability of advanced diagnostic tools. We aim to describe thetemporal trends in age, gender and clinical characteristics at HCM diagnosis over >4 decades.METHODSWe retrospectively analyzed records from the ongoing multinational SHaRe registry. Overall, 7,286HCM patients diagnosed at an age ≥18 years between 1961 and 2019 were included in the analysisand divided into three eras of diagnosis (<2000, 2000-2010, >2010).RESULTSAge at diagnosis increased markedly over time (40±14 vs. 47±15 vs. 51±16 years, p<0.001), both inUS and non-US sites, with a stable male-to-female ratio of about 3:2. Frequency of familial HCMdeclined over time (38.8% vs. 34.3% vs. 32.7%, p<0.001), as well as heart failure symptoms atpresentation (NYHA III/IV: 18.1% vs. 15.8% vs. 12.6%, p<0.001). Left ventricular hypertrophybecame less marked over time (maximum wall thickness: 20±6 vs. 18±5 vs. 17±5 mm, p<0.001),while prevalence of obstructive HCM was greater in recent cohorts (peak gradient >30 mmHg:31.9% vs. 39.3% vs. 39.0%, p=0.001). Consistent with decreasing phenotypic severity, yield ofpathogenic/likely-pathogenic variants at genetic testing decreased over time (57.7% vs. 45.6% vs.38.4%, p<0.001).CONCLUSIONSEvolving HCM populations include progressively greater representation of older patients withsporadic disease, mild phenotypes and genotype-negative status. Such trend suggests a prominentrole of imaging over genetic testing in promoting HCM diagnoses and urges efforts to understandgenotype-negative disease eluding the classic monogenic paradigm

Journal article

Ware J, Mazzarotto F, 2020, Enhancing rare variant interpretation in inherited arrhythmias through quantitative analysis of consortium disease cohorts and population controls, Genetics in Medicine, Vol: 23, Pages: 47-58, ISSN: 1098-3600

PURPOSE:Stringent variant interpretation guidelines can lead to high rates of variants of uncertain significance (VUS) for genetically heterogeneous disease like long QT syndrome (LQTS) and Brugada syndrome (BrS). Quantitative and disease-specific customization of American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines can address this false negative rate. METHODS:We compared rare variant frequencies from 1847 LQTS (KCNQ1/KCNH2/SCN5A) and 3335 BrS (SCN5A) cases from the International LQTS/BrS Genetics Consortia to population-specific gnomAD data and developed disease-specific criteria for ACMG/AMP evidence classes-rarity (PM2/BS1 rules) and case enrichment of individual (PS4) and domain-specific (PM1) variants. RESULTS:Rare SCN5A variant prevalence differed between European (20.8%) and Japanese (8.9%) BrS patients (p = 5.7 × 10-18) and diagnosis with spontaneous (28.7%) versus induced (15.8%) Brugada type 1 electrocardiogram (ECG) (p = 1.3 × 10-13). Ion channel transmembrane regions and specific N-terminus (KCNH2) and C-terminus (KCNQ1/KCNH2) domains were characterized by high enrichment of case variants and >95% probability of pathogenicity. Applying the customized rules, 17.4% of European BrS and 74.8% of European LQTS cases had (likely) pathogenic variants, compared with estimated diagnostic yields (case excess over gnomAD) of 19.2%/82.1%, reducing VUS prevalence to close to background rare variant frequency. CONCLUSION:Large case-control data sets enable quantitative implementation of ACMG/AMP guidelines and increased sensitivity for inherited arrhythmia genetic testing.

Journal article

Helms AS, Thompson AD, Glazier AA, Hafeez N, Kabani S, Rodriguez J, Yob JM, Woolcock H, Mazzarotto F, Lakdawala NK, Wittekind SG, Pereira AC, Jacoby DL, Colan SD, Ashley EA, Saberi S, Ware JS, Ingles J, Semsarian C, Michels M, Olivotto I, Ho CY, Day SMet al., 2020, Spatial and functional distribution of MYBPC3 pathogenic variants and clinical outcomes in patients with hypertrophic cardiomyopathy, Circulation: Genomic and Precision Medicine, Vol: 13, Pages: 396-405, ISSN: 2574-8300

Background - Pathogenic variants in MYBPC3, encoding cardiac MyBP-C, are the most common cause of familial hypertrophic cardiomyopathy. A large number of unique MYBPC3 variants and relatively small genotyped HCM cohorts have precluded detailed genotype-phenotype correlations.Methods - Patients with HCM and MYBPC3 variants were identified from the Sarcomeric Human Cardiomyopathy Registry (SHaRe). Variant types and locations were analyzed, morphologic severity was assessed, and time-event analysis was performed (composite clinical outcome of sudden death, class III/IV heart failure, LVAD/transplant, atrial fibrillation). For selected missense variants falling in enriched domains, myofilament localization and degradation rates were measured in vitro.Results - Among 4,756 genotyped HCM patients in SHaRe, 1,316 patients were identified with adjudicated pathogenic truncating (N=234 unique variants, 1047 patients) or non-truncating (N=22 unique variants, 191 patients) variants in MYBPC3. Truncating variants were evenly dispersed throughout the gene, and hypertrophy severity and outcomes were not associated with variant location (grouped by 5' - 3' quartiles or by founder variant subgroup). Non-truncating pathogenic variants clustered in the C3, C6, and C10 domains (18 of 22, 82%, p<0.001 vs. gnomAD common variants) and were associated with similar hypertrophy severity and adverse event rates as observed with truncating variants. MyBP-C with variants in the C3, C6, and C10 domains was expressed in rat ventricular myocytes. C10 mutant MyBP-C failed to incorporate into myofilaments and degradation rates were accelerated by ~90%, while C3 and C6 mutant MyBP-C incorporated normally with degradation rate similar to wild-type.Conclusions - Truncating variants account for 91% of MYBPC3 pathogenic variants and cause similar clinical severity and outcomes regardless of location, consistent with locus-independent loss-of-function. Non-truncating MYBPC3 pathogenic variants are regi

Journal article

Mazzarotto F, Olivotto I, Boschi B, Girolami F, Poggesi C, Barton P, Walsh Ret al., 2020, Contemporary insights into the genetics of hypertrophic cardiomyopathy: towards a new era in clinical testing?, Journal of the American Heart Association, Vol: 21, Pages: 1-22, ISSN: 2047-9980

Genetic testing for hypertrophic cardiomyopathy (HCM) is an established clinical technique, supported by30 years of research into its genetic aetiology. Although pathogenic variants are often detected in patientsand used to identify at-risk relatives, the effectiveness of genetic testing has been hampered by ambiguousgenetic associations (yielding uncertain and potentially false-positive results), difficulties in classifyingvariants and uncertainty about genotype-negative patients. Recent case-control studies on rare variation,improved data sharing and meta-analysis of case cohorts contributed to new insights into the genetic basisof HCM. In particular, while research into new genes and mechanisms remains essential, re-assessment ofMendelian genetic associations in HCM argues that current clinical genetic testing should be limited to asmall number of validated disease genes that yield informative and interpretable results. Accurate andconsistent variant interpretation has benefitted from new standardised variant interpretation guidelines andinnovative approaches to improve classification. Most cases lacking a pathogenic variant are now believedto indicate non-Mendelian HCM, with more benign prognosis and minimal risk to relatives.Here, we discuss recent advances in the genetics of HCM and their application to clinical genetic testingtogether with practical issues regarding implementation. While this review focuses on HCM, many of theissues discussed are also relevant to other inherited cardiac diseases.

Journal article

Mazzarotto F, Olivotto I, Walsh R, 2020, Advantages and perils of clinical whole-exome and whole-genome sequencing in cardiomyopathy., Cardiovascular Drugs and Therapy, Vol: 34, Pages: 241-253, ISSN: 0920-3206

As the price of next-generation sequencing keeps decreasing, cost is becoming a less important discriminator for diagnostic laboratories in choosing the preferred type of approach to genetic testing. Genome-wide sequencing strategies will plausibly become the standard first-tier tools for genetic testing, with the potential for deeper understanding of the genetic architecture of cardiomyopathies and discovery of the underlying aetiology in the many patients in whom the genetic cause remains elusive. Routine usage of extended sequencing assays will also enable "genetic-first diagnostics", particularly for those patients affected with syndromic conditions of unclear genetic origin, often resulting in costly and distressing diagnostic odysseys before reaching a diagnosis. However, access to genome-wide data for all patients will need to be managed with rigour and caution by (cardiovascular) genetic professionals to avoid erroneous variant pathogenicity assertions and over-reporting uncertain findings, both damaging scenarios to patients and their family members. Researchers will also be required to adopt robust methods to demonstrate novel genetic associations with disease, given the high "narrative potential" of such large datasets and the dangers of generating further false positive associations (that have previously blighted the field of cardiac genetics). Here, we discuss advantages and dangers associated with the routine adoption of whole-exome (and whole-genome) sequencing in diagnostic facilities and in the research setting in the context of cardiomyopathies but relevant to several other conditions.

Journal article

Mazzarotto F, Hawley M, Beltrami M, Beekman L, Boschi B, Girolami F, Roberts A, Lodder E, Cerbai E, Cook S, Ware J, Funke B, Olivotto I, Bezzina C, Barton PJR, Walsh Ret al., 2020, The genetic architecture of left ventricular non-compaction reveals both substantial overlap with other cardiomyopathies and a distinct aetiology in a subset of cases, Publisher: bioRxiv

Rationale: Left ventricular non-compaction (LVNC) is a condition characterised by trabeculations in the myocardial wall and is the subject of considerable conjecture as to whether it represents a distinct pathology or a secondary phenotype associated with other cardiac diseases, particularly cardiomyopathies. Objective: To investigate the genetic architecture of LVNC by identifying genes and variant classes robustly associated with disease and comparing these to other genetically characterised cardiomyopathies. Methods and Results: We performed rare variant association analysis using six different LVNC cohorts comprising 840 cases together with 125,748 gnomAD population controls and compared results to similar analyses with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) cases. We observed substantial overlap in genes and variant classes enriched in LVNC and DCM/HCM, indicating that in many cases LVNC belongs to a spectrum of more established cardiomyopathies, with non-compaction representing a phenotypic variation in patients with DCM- or HCM-causing variants. In contrast, five variant classes were uniquely enriched in LVNC cases, of which truncating variants in MYH7, ACTN2 and PRDM16 may represent a distinct LVNC aetiology. MYH7 truncating variants are generally considered as non-pathogenic but were detected in 2% of LVNC cases compared to 0.1% of controls, including a cluster of variants around a single splice region. Additionally, structural variants (exon deletions) in RYR2 and missense variants in the transmembrane region of HCN4 were enriched in LVNC cases, confirming prior reports regarding the association of these variant classes with combined LVNC and arrhythmia phenotypes. Conclusions: We demonstrated that genetic association analysis can clarify the relationship between LVNC and established cardiomyopathies, highlighted substantial overlap with DCM/HCM but also identified variant classes associated with distinct LVNC and with joint LVN

Working paper

Mazzarotto F, Tayal U, Buchan RJ, Midwinter W, Wilk A, Whiffin N, Govind R, Mazaika E, De Marvao A, Dawes TJW, Felkin LE, Ahmad M, Theotokis PI, Edwards E, Ing AY, Thomson KL, Chan LLH, Sim D, Baksi AJ, Pantazis A, Roberts AM, Watkins H, Funke B, O'Regan DP, Olivotto I, Barton PJR, Prasad SK, Cook SA, Ware JS, Walsh Ret al., 2020, Reevaluating the Genetic Contribution of Monogenic Dilated Cardiomyopathy, Circulation, Pages: 387-398, ISSN: 0009-7322

Background: Dilated cardiomyopathy (DCM) is genetically heterogeneous, with >100 purported disease genes tested in clinical laboratories. However, many genes were originally identified based on candidate-gene studies that did not adequately account for background population variation. Here we define the frequency of rare variation in 2538 patients with DCM across protein-coding regions of 56 commonly tested genes and compare this to both 912 confirmed healthy controls and a reference population of 60 706 individuals to identify clinically interpretable genes robustly associated with dominant monogenic DCM. Methods: We used the TruSight Cardio sequencing panel to evaluate the burden of rare variants in 56 putative DCM genes in 1040 patients with DCM and 912 healthy volunteers processed with identical sequencing and bioinformatics pipelines. We further aggregated data from 1498 patients with DCM sequenced in diagnostic laboratories and the Exome Aggregation Consortium database for replication and meta-analysis. Results: Truncating variants in TTN and DSP were associated with DCM in all comparisons. Variants in MYH7, LMNA, BAG3, TNNT2, TNNC1, PLN, ACTC1, NEXN, TPM1, and VCL were significantly enriched in specific patient subsets, with the last 2 genes potentially contributing primarily to early-onset forms of DCM. Overall, rare variants in these 12 genes potentially explained 17% of cases in the outpatient clinic cohort representing a broad range of adult patients with DCM and 26% of cases in the diagnostic referral cohort enriched in familial and early-onset DCM. Although the absence of a significant excess in other genes cannot preclude a limited role in disease, such genes have limited diagnostic value because novel variants will be uninterpretable and their diagnostic yield is minimal. Conclusions: In the largest sequenced DCM cohort yet described, we observe robust disease association with 12 genes, highlighting their importance in DCM and translating into high

Journal article

Canepa M, Fumagalli C, Tini G, Mazzarotto F, Vincent-Tompkins J, Day S, Ashley E, Michels M, Colan SD, Jacoby D, Ho C, Olivotto Iet al., 2019, Temporal trend in age at diagnosis of hypertrophic cardiomyopathy: an analysis of the share registry, 80th SIC National Congress, Publisher: OXFORD UNIV PRESS, Pages: J181-J182, ISSN: 1520-765X

Conference paper

Canepa M, Fumagalli C, Tini G, Mazzarotto F, Vincent-Tompkins J, Day SM, Ashley EA, Michels M, Colan SD, Jacoby D, Ho C, Olivotto Iet al., 2019, Temporal Trend in Age at Diagnosis of Hypertrophic Cardiomyopathy: An Analysis of the Share Registry, Scientific Sessions of the American-Heart-Association, Publisher: LIPPINCOTT WILLIAMS & WILKINS, ISSN: 0009-7322

Conference paper

Ghiselli L, Marchi A, Fumagalli C, Maurizi N, Oddo A, Pieri F, Girolami F, Rowin E, Mazzarotto F, Cicoira M, Ribichini F, Arretini A, Targetti M, Passantino S, Cecchi F, Marchionni N, Maron M, Mori F, Olivotto Iet al., 2019, Sex-related differences in exercise performance and outcome of patients with hypertrophic cardiomyopathy., Eur J Prev Cardiol, Pages: 2047487319886961-2047487319886961

AIMS: Exercise performance is known to predict outcome in hypertrophic cardiomyopathy (HCM), but whether sex-related differences exist is unresolved. We explored whether functional impairment, assessed by exercise echocardiography, has comparable predictive accuracy in females and males with HCM. METHODS: We retrospectively evaluated 292 HCM patients (46 ± 16 years, 72% males), consecutively referred for exercise echocardiography; 242 were followed for 5.9 ± 4.2 years. RESULTS: Peak exercise capacity was 6.5 ± 1.6 metabolic equivalents (METs). Sixty patients (21%) showed impaired exercise capacity (≤5 METs). Exercise performance was reduced in females, compared with males (5.6 ± 1.6 vs 6.9 ± 1.5 METs, p < 0.001; peak METs ≤ 5 in 40% vs 13%, p < 0.001), largely driven by a worse performance in women >50 years of age. At multivariable analysis, female sex was independently associated with impaired exercise capacity (odds ratio: 4.67; 95% confidence interval (CI): 1.83-11.90; p = 0.001). During follow-up, 24 patients (10%) met the primary endpoint (a combination of cardiac death, heart failure requiring hospitalization, sustained ventricular tachycardia, appropriate implantable cardioverter defibrillator discharge, resuscitated sudden cardiac death and cardioembolic stroke). Event-free survival was reduced in females (p = 0.035 vs males). Peak METs were inversely related to outcome in males (hazard ratio (HR) per unit increase: 0.57; 95% CI: 0.39-0.84; p = 0.004) but not in females (HR: 1.22; 95% CI: 0.66-2.24; p = 0.53). CONCLUSIONS: Female patients with HCM showed significant age-related impairment in functional capacity compared with males, particularly evident in post-menopausal age groups. While women were at greater risk of HCM-related complications

Journal article

Cappelli F, Mazzarotto F, Frusconi S, Contini E, Polimanti R, Buxbaum J, Martone R, Morini S, Taborchi G, Bartolini S, Olivotto I, Pelo E, Di Mario C, Perfetto Fet al., 2019, Genetic ancestry analysis of the Italian founder population carrying the cardiac amyloidosis-causing variant Val122Ile in the transthyretin gene, Congress of the European-Society-of-Cardiology (ESC) / World Congress of Cardiology, Publisher: OXFORD UNIV PRESS, Pages: 1682-1682, ISSN: 0195-668X

Conference paper

Walsh R, Mazzarotto F, Whiffin N, Buchan R, Li N, Felkin L, Thomson KL, Watkins H, Barton PJR, Olivotto I, Cook SA, Bezzina CR, Ware JSet al., 2019, Quantitative approaches to variant classification increase the yield and precision of genetic testing in Mendelian diseases, 52nd Conference of the European-Society-of-Human-Genetics (ESHG), Publisher: NATURE PUBLISHING GROUP, Pages: 1720-1720, ISSN: 1018-4813

Conference paper

Fumagalli C, Fedele E, Beltrami M, Maurizi N, Passantino S, Targetti M, Arretini A, Baldini K, Tomberli A, Mazzarotto F, Coppini R, Ferrantini C, Cecchi F, Poggesi C, Olivotto Iet al., 2019, Comparison of long-term clinical course and outcome of MYBPC3-versus MYH7-related hypertrophic cardiomyopathy, Congress of the European-Society-of-Cardiology (ESC) / World Congress of Cardiology, Publisher: OXFORD UNIV PRESS, Pages: 699-699, ISSN: 0195-668X

Conference paper

Mazzarotto F, Tayal P, Buchan R, Midwinter W, Wilk A, Whiffin N, Govind R, Mazaika E, De Marvao A, Felkin L, Dawes T, Ahmad M, Edwards E, Ing A, Thomson K, Chan L, Sim D, Baksi J, Pantazis A, Roberts A, Watkins H, Funke B, O'Regan D, Olivotto I, Barton P, Prasad S, Cook S, Ware J, Walsh Ret al., 2019, RE-EVALUATING THE GENETIC CONTRIBUTION OF MONOGENIC DILATED CARDIOMYOPATHY, Annual Conference of the British-Cardiovascular-Society (BCS) - Digital Health Revolution, Publisher: BMJ PUBLISHING GROUP, Pages: A100-A100, ISSN: 1355-6037

Conference paper

Mazzarotto F, Girolami F, Boschi B, Barlocco F, Tomberli A, Baldini K, Coppini R, Tanini I, Bardi S, Contini E, Cecchi F, Pelo E, Cook SA, Cerbai E, Poggesi C, Torricelli F, Walsh R, Olivotto Iet al., 2019, Defining the diagnostic effectiveness of genes for inclusion in panels: the experience of two decades of genetic testing for hypertrophic cardiomyopathy at a single center, Genetics in Medicine, Vol: 21, Pages: 284-292, ISSN: 1098-3600

PurposeGenetic testing in hypertrophic cardiomyopathy (HCM) has long relied on Sanger sequencing of sarcomeric genes. The advent of next-generation sequencing (NGS) has catalyzed routine testing of additional genes of dubious HCM-causing potential. We used 19 years of genetic testing results to define a reliable set of genes implicated in Mendelian HCM and assess the value of expanded NGS panels.MethodsWe dissected genetic testing results from 1,198 single-center HCM probands and devised a widely applicable score to identify which genes yield effective results in the diagnostic setting.ResultsCompared with early panels targeting only fully validated sarcomeric HCM genes, expanded NGS panels allow the prompt recognition of probands with HCM-mimicking diseases. Scoring by “diagnostic effectiveness” highlighted that PLN should also be routinely screened besides historically validated genes for HCM and its mimics.ConclusionThe additive value of expanded panels in HCM genetic testing lies in the systematic screening of genes associated with HCM mimics, requiring different patient management. Only variants in a limited set of genes are highly actionable and interpretable in the clinic, suggesting that larger panels offer limited additional sensitivity. A score estimating the relative effectiveness of a given gene’s inclusion in diagnostic panels is proposed.

Journal article

Walsh R, Mazzarotto F, Whiffin N, Buchan R, Midwinter W, Wilk A, Li N, Felkin L, Ingold N, Govind R, Ahmad M, Mazaika E, Allouba M, Zhang X, de Marvao A, Day SM, Ashley E, Colan SD, Michels M, Pereira AC, Jacoby D, Ho CY, Thomson KL, Watkins H, Barton PJR, Olivotto I, Cook SA, Ware JSet al., 2019, Quantitative approaches to variant classification increase the yield and precision of genetic testing in Mendelian diseases: The case of hypertrophic cardiomyopathy, Genome Medicine, Vol: 11, ISSN: 1756-994X

BackgroundInternational guidelines for variant interpretation in Mendelian disease set stringent criteria to report a variant as (likely) pathogenic, prioritising control of false-positive rate over test sensitivity and diagnostic yield. Genetic testing is also more likely informative in individuals with well-characterised variants from extensively studied European-ancestry populations. Inherited cardiomyopathies are relatively common Mendelian diseases that allow empirical calibration and assessment of this framework.MethodsWe compared rare variants in large hypertrophic cardiomyopathy (HCM) cohorts (up to 6179 cases) to reference populations to identify variant classes with high prior likelihoods of pathogenicity, as defined by etiological fraction (EF). We analysed the distribution of variants using a bespoke unsupervised clustering algorithm to identify gene regions in which variants are significantly clustered in cases.ResultsAnalysis of variant distribution identified regions in which variants are significantly enriched in cases and variant location was a better discriminator of pathogenicity than generic computational functional prediction algorithms. Non-truncating variant classes with an EF ≥ 0.95 were identified in five established HCM genes. Applying this approach leads to an estimated 14–20% increase in cases with actionable HCM variants, i.e. variants classified as pathogenic/likely pathogenic that might be used for predictive testing in probands’ relatives.ConclusionsWhen found in a patient confirmed to have disease, novel variants in some genes and regions are empirically shown to have a sufficiently high probability of pathogenicity to support a “likely pathogenic” classification, even without additional segregation or functional data. This could increase the yield of high confidence actionable variants, consistent with the framework and recommendations of current guidelines. The techniques outlined offer a consisten

Journal article

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