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Physiologic LV remodeling in young trained athletes as a consequence of chronic training can occasionally mimic certain pathologic conditions associated with sudden death, such as HCM. A small but important subset ofelite male athletes may show a borderline increased LV wall thickness of 13 to 15 mm, which defines a gray zone of overlap between the extreme expressions of athlete's heart and a mild HCM phenotype. Such diagnostic ambiguity can be resolved by using the paradigm of noninvasive parameters including testing with echocardiography (and, more recently, with CMR): left atrial and LV chamber dimensions and shape, brief periods of deconditioning to alter LV mass, measurement of oxygen consumption and diastolic filling, and recognition of familial occurrence of HCM or a pathogenic HCM-causing sarcomere mutation. Such distinctions between physiologic/benign athlete's heart and HCM, the most common cause of sudden death in the young in the United States, can be crucial. The recognition of HCM leads to disqualification from intense competitive sports to reduce sudden death risk and, when appropriate, permits initiation of therapeutic interventions.Copyright © 2012 by Elsevier Inc. [ABSTRACT FROM AUTHOR]

Dynamic obstruction to left ventricular (LV) outflow was recognized from the earliest (50 years ago) clinical descriptions of hypertrophic cardiomyopathy (HCM) and has proved to be a complex phenomenon unique in many respects, as well as arguably the most visible and well-known pathophysiologic component of this heterogeneous disease. Over the past 5 decades, the clinical significance attributable to dynamic LV outflow tract gradients in HCM has triggered a periodic and instructive debate. Nevertheless, only recently has evidence emerged from observational analyses in large patient cohorts that unequivocally supports subaortic pressure gradients (and obstruction) both as true impedance to LV outflow and independent determinants of disabling exertional symptoms and cardiovascular mortality. Furthermore, abolition of subaortic gradients by surgical myectomy (or percutaneous alcohol septal ablation) results in profound and consistent symptomatic benefit and restoration of quality of life, with myectomy providing a long-term survival similar to that observed in the general population. These findings resolve the long-festering controversy over the existence of obstruction in HCM and whether outflow gradients are clinically important elements of this complex disease. These data also underscore the important principle, particularly relevant to clinical practice, that heart failure due to LV outflow obstruction in HCM is mechanically reversible and amenable to invasive septal reduction therapy. Finally, the recent observation that the vast majority of patients with HCM have the propensity to develop outflow obstruction (either at rest or with exercise) underscores a return to the characterization of HCM in 1960 as a predominantly obstructive disease. [ABSTRACT FROM AUTHOR]

We found a highly inconsistent relation between the granular and reflective ultrasound ("speckling") pattern frequently observed in the ventricular septum of patients with hypertrophic cardiomyopathy and evidence of myocardial fibrosis by contrast-enhanced cardiovascular magnetic resonance imaging. Therefore, this distinctive echocardiographic appearance of the myocardium does not accurately characterize left ventricular scarring and is most likely explained as an extraneous ultrasound signal pattern. In conclusion, myocardial fibrosis in patients with hypertrophic cardiomyopathy is most reliably identified using contrast-enhanced cardiovascular magnetic resonance imaging. [ABSTRACT FROM AUTHOR]

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease, affecting 1:200 to 1:500 individuals worldwide. Guidelines on the diagnosis and management of HCM have been recently published by the European Society of Cardiology (ESC) and American societies. The ESC guidelines cover a broad range of cardiomyopathies, including HCM, with 119 recommendations, whereas the American guidelines focus exclusively on HCM with 141 specific recommendations. Both guidelines emphasize a comprehensive diagnostic approach, including imaging and genetic testing, but differ in some specific aspects. For example, sudden cardiac death (SCD) risk assessment is a primary point of divergence. The ESC guidelines advocate for the use of a validated Risk-SCD calculator, while the American guidelines rely on specific risk markers for individualized risk evaluation. Management strategies also vary: both guidelines prioritize beta-blockers and calcium channel blockers in patients with resting or provocable left ventricular outflow tract (LVOT) obstruction. If beta-blockers (or verapamil/diltiazem) are ineffective, either disopyramide or the myosin inhibitor mavacamten may be an option with slightly different indications among the two guidelines. Septal reduction therapy is recommended in ESC guidelines for symptomatic patients with significant LVOT gradients, while American guidelines suggest earlier myectomy for certain clinical factors and emphasize shared decision-making. The ESC guidelines recommend sequential atrioventricular pacing and dual-chamber defibrillators for reducing LVOT gradients. The American guidelines focus on genetic testing for risk assessment and suggest periodic cardiac magnetic resonance imaging. This paper provides a detailed comparison of these guidelines, highlighting key differences and areas needing further research and expert debate., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background and Aims: The role of biomarker testing in the management of obstructive hypertrophic cardiomyopathy is not well defined. This pre-specified analysis of SEQUOIA-HCM (NCT05186818) sought to define the associations between clinical characteristics and baseline concentrations of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin I (hs-cTnI), and to evaluate the effect of treatment with aficamten on biomarker concentrations., Methods: Cardiac biomarkers were measured at baseline and serially throughout the study. Regression analyses determined predictors of baseline NT-proBNP and hs-cTnI concentrations, and evaluated whether early changes in these biomarkers relate to later changes in left ventricular outflow tract gradient (LVOT-G), other echocardiographic measures, health status, and functional capacity., Results: Baseline concentration of NT-proBNP was associated with LVOT-G and measures of diastolic function, while hs-cTnI was associated with left ventricular thickness. Within 8 weeks of treatment with aficamten, NT-proBNP was reduced by 79% (95% confidence interval 76%-83%, P < .001) and hs-cTnI by 41% (95% confidence interval 32%-49%, P < .001); both biomarkers reverted to baseline after washout. Reductions in NT-proBNP and hs-cTnI by 24 weeks were strongly associated with a lowering of LVOT-G, improvement in health status, and increased peak oxygen uptake. N-Terminal pro-B-type natriuretic peptide reduction strongly correlated with the majority of improvements in exercise capacity. Furthermore, the change in NT-proBNP by Week 2 was associated with the 24-week change in key endpoints., Conclusions: N-Terminal pro-B-type natriuretic peptide and hs-cTnI concentrations are associated with key variables in obstructive hypertrophic cardiomyopathy. Serial measurement of NT-proBNP and hs-cTnI appears to reflect clinical response to aficamten therapy., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Background: Hypertrophic cardiomyopathy (HCM) is a heterogeneous condition that can lead to atrial fibrillation, heart failure, and sudden cardiac death in many individuals but mild clinical impact in others. The mechanisms underlying this phenotypic heterogeneity are not well defined. The aim of this study was to use plasma proteomic profiling to help illuminate biomarkers that reflect or inform the heterogeneity observed in HCM., Methods: The Olink antibody-based proteomic platform was used to measure plasma proteins in patients with genotype positive (sarcomeric) HCM participating in the HCM Registry. We assessed associations between plasma protein levels with clinical features, cardiac magnetic resonance imaging metrics, and the development of atrial fibrillation., Results: We measured 275 proteins in 701 patients with sarcomeric HCM. There were associations between late gadolinium enhancement with proteins reflecting neurohormonal activation (NT-proBNP [N-terminal pro-B-type natriuretic peptide] and ACE2 [angiotensin-converting enzyme 2]). Metrics of left ventricular remodeling had novel associations with proteins involved in vascular development and homeostasis (vascular endothelial growth factor-D and TM [thrombomodulin]). Assessing clinical features, the European Society of Cardiology sudden cardiac death risk score was inversely associated with SCF (stem cell factor). Incident atrial fibrillation was associated with mediators of inflammation and fibrosis (MMP2 [matrix metalloproteinase 2] and SPON1 [spondin 1])., Conclusions: Proteomic profiling of sarcomeric HCM identified biomarkers associated with adverse imaging and clinical phenotypes. These circulating proteins are part of both established pathways, including neurohormonal activation and fibrosis, and less familiar pathways, including endothelial function and inflammatory proteins less well characterized in HCM. These findings highlight the value of plasma profiling to identify biomarkers of risk and to gain further insights into the pathophysiology of HCM.

Background: Standard-of-care (SoC) medications for the treatment of obstructive hypertrophic cardiomyopathy (oHCM) are recommended as first-line therapy despite the lack of evidence from controlled clinical trials and well known off-target side effects., Objectives: We describe the impact of SoC therapy downtitration and withdrawal in patients already receiving aficamten in FOREST-HCM (Follow-Up, Open-Label, Research Evaluation of Sustained Treatment with Aficamten in Hypertrophic Cardiomyopathy; NCT04848506)., Methods: Patients receiving SoC therapy (beta-blocker, nondihydropyridine calcium-channel blocker, and/or disopyramide) were eligible for protocol-guided SoC downtitration and withdrawal at the discretion of the investigator and after achieving a stable dose of aficamten for ≥4 weeks. Successful SoC withdrawal was defined as at least a 50% dose-reduction in ≥1 medication. Adverse events (AEs) were prospectively evaluated 1 to 2 weeks after any SoC withdrawal., Results: Of 145 patients with oHCM who were followed for at least 24 weeks (mean age 60.5 ± 13.2 years; 44.8% female; 42% NYHA functional class III), 136 (93.8%) were receiving ≥1 SoC therapy; of those, 64 (47%) had an attempt at withdrawal, with 59 (92.2%) successful. Thirty-eight (64.4%) patients completely discontinued ≥1 medication, and 27 (45.8%) achieved aficamten monotherapy with 2 later restarting a SoC medication. There were no significant differences in baseline characteristics on day 1 in FOREST-HCM in those with a SoC-withdrawal vs no-withdrawal attempt. In patients who underwent successful SoC therapy withdrawal, NYHA functional class improved by ≥1 class in 79.2% from baseline, Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score improved to 83.0 ± 15.8 points, and resting and Valsalva left ventricular outflow tract gradient improved to 14.3 ± 10.9 and 32.9 ± 21.4 mm Hg, respectively. N-terminal pro-B-type natriuretic peptide levels improved to a median of 220.0 pg/mL (Q1-Q3: 102.0-554.0.0 pg/mL) and high-sensitivity troponin I improved to a median of 6.0 ng/L (Q1-Q3:3.5-10.7 ng/L). Downtitration and withdrawal of SoC therapy did not impact these results (all P values for change were >0.05), and these changes were similar in patients who did not undergo SoC therapy withdrawal. There were no serious AEs attributed to SoC withdrawal and treatment emergent AEs were similar between groups., Conclusions: In FOREST-HCM, one-half of the patients with oHCM attempted downtitration and withdrawal of SoC medications while receiving aficamten treatment, with infrequent instances of resumption of SoC. Stopping and dose reduction of SoC medications were well tolerated with no adverse consequences in clinical measures of efficacy (Follow-Up, Open-Label, Research Evaluation of Sustained Treatment with Aficamten in Hypertrophic Cardiomyopathy [FOREST-HCM]; NCT04848506)., Competing Interests: Funding Support and Author Disclosures The FOREST-HCM trial is funded by Cytokinetics, Incorporated. Dr Masri has received consulting/advisor fees from Tenaya, Attralus, Cytokinetics, Bristol Myers Squibb, Eidos, Pfizer, Haya, Lexion, BioMarin, Alexion, and Ionis; and has received research grants from Ionis, Pfizer, Cytokinetics, and Attralus. Dr Choudhury has received advisor fees from Cytokinetics. Dr Barriales-Villa has received consulting/advisor fees from MyoKardia/Bristol Myers Squibb. Dr Elliott has received consulting fees from Bristol Myers Squibb, Pfizer, and Cytokinetics; has received speaker fees from Pfizer; and has received an unrestricted grant from Sarepta. Dr Maron has received consulting/advisor fees from Imbria, Edgewise, and Biomarin; and has received steering committee fees for SEQUIOA-HCM from Cytokinetics, Incorporated. Dr Nassif has received research and grant support from AstraZeneca and Cytokinetics; and has received consulting/advisory fees from Vifor and Cytokinetics. Dr Oreziak has received investigator fees from Cytokinetics and MyoKardia/Bristol Myers Squibb. Dr Owens has received consulting/advisor fees from Bristol Myers Squibb; and has received research grants from Bristol Myers Squibb, Cytokinetics, Novartis, and Actelion Pharmaceuticals. Dr Saberi has received consulting fees from Bristol Myers Squibb and Cytokinetics. Dr Tower-Rader has received research grants from Bristol Myers Squibb and Cytokinetics. Dr Rader has received consulting fees/honoraria from Medtronic, Cytokinetics, Bristol Myers Squibb, and Recor. Dr Garcia-Pavia has received Speakers Bureau fees from Bristol Myers Squibb, Pfizer, BridgeBio, Ionis, AstraZeneca, NovoNordisk, Intellia, and Alnylam; has received consulting fees from Bristol Myers Squibb, Cytokinetics, Rocket Pharma, Lexeo Therapeutics, Pfizer, BridgeBio, Daiichi-Sankyo, Neurimmune, Alnylam, AstraZeneca, Novo Nordisk, Attralus, Intellia, Idoven, General Electric, and Alexion; and has received research/educational support to his institution from Pfizer, BridgeBio, NovoNordisk, AstraZeneca, Intellia, and Alnylam. Dr Olivotto has received Speakers Bureau fees from Bristol Myers Squibb, Amicus, and Genzyme; has received consulting/advisor fees from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Tenaya, Rocket Pharma, and Lexeo; and has received research grant funding from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Menarini International, Chiesi, and Boston Scientific. Dr Wang has received Speakers Bureau fees from Bristol Myers Squibb; has received consulting/advisor fees from Bristol Myers Squibb and Cytokinetics; and has received research grants from Bristol Myers Squibb, Cytokinetics, and Abbott Vascular. Drs Heitner, Jacoby, Kupfer, Malik, Melloni, Meng, and Wei are employees of and hold stock in Cytokinetics Incorporated. Dr Sherrid has received consulting fees/honoraria from Pfizer Inc; and has served as a consultant for Cytokinetics Inc without payment. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Aficamten is a cardiac myosin inhibitor that mitigates left ventricular outflow gradients in obstructive hypertrophic cardiomyopathy (oHCM). The clinical efficacy of aficamten across multiple outcome domains in oHCM has not been fully defined., Objectives: This responder analysis from the SEQUOIA-HCM (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM) trial characterizes the clinical impact of aficamten., Methods: Patients who were symptomatic of oHCM were randomized to aficamten (n = 142) or placebo (n = 140) daily for 24 weeks. Outcomes assessed included the proportion of patients with complete hemodynamic response (rest and Valsalva gradient <30 mm Hg and <50 mm Hg, respectively), relief in limiting symptoms (≥1 improvement in NYHA functional class and/or ≥10-point change in Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score), enhanced exercise capacity (≥1.5 mL/kg/min change in peak oxygen uptake), and ≥50% reduction in N-terminal pro-B-type natriuretic peptide. Eligibility for septal reduction therapy was also evaluated., Results: At 24 weeks, patients treated with aficamten vs placebo showed significant improvement in limiting symptoms (71% vs 42%), were more likely to have complete hemodynamic response (68% vs 7%), demonstrated enhanced exercise capacity (47% vs 24%), and showed a decrease ≥50% in N-terminal pro-B-type natriuretic peptide (84% vs 8%) (P ≤ 0.002 for all). An improvement in ≥1 of these outcome measures was achieved in 97% of patients treated with aficamten (vs 59% placebo), including 23% on aficamten who achieved all 4 outcomes compared with none in placebo. Among 32 patients receiving aficamten and 29 patients receiving placebo who were eligible for septal reduction therapy, 28 (88%) from the aficamten group were no longer eligible at 24 weeks compared with 15 (52%) from the placebo group (P = 0.002)., Conclusions: Treatment with aficamten was associated with substantial improvements across a broad range of clinically relevant efficacy measures. These results underscore the wide-ranging potential of aficamten for treatment of patients with symptomatic oHCM (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults with oHCM [SEQUOIA-HCM]; NCT05186818)., Competing Interests: Funding Support and Author Disclosures The SEQUOIA-HCM study was funded by Cytokinetics, Incorporated. Dr Maron has received consultant/advisor fees from Imbria, Edgewise, and BioMarin; and has received steering committee fees for SEQUIOA-HCM from Cytokinetics. Dr Masri has received consultant/advisor fees from Tenaya, Attralus, Cytokinetics, Bristol Myers Squibb, and Ionis; and has received research grants from Ionis, Akcea, Pfizer, Ultromics, and the Wheeler Foundation. Dr Nassif has received research and grant support from AstraZeneca and Cytokinetics; and has received consulting/advisory fees from Vifor and Cytokinetics. Dr Barriales-Villa has received consultant/advisor fees from MyoKardia/Bristol Myers Squibb. Dr Arad has received consulting and lecture fees from Bristol Myers Squibb. Dr Cardim has received consultant/advisor fees from Cytokinetics, Bristol Myers Squibb, Pfizer, Menarini, Boehinger Ingelheim, and Bial. Dr Coats has received speaker fees from Alnylam and Roche; and has received advisor fees from Cytokinetics. Dr Düngen has received grants from Novartis, CSL Behring, and Cytokinetics. Dr Garcia-Pavia has received speakers’ bureau fees from Pfizer, AstraZeneca, Novo Nordisk, Ionis, Bridgebio, Bristol Myers Squibb, Intelllia, and Alnylam; has received consulting/advisor fees from Pfizer, Alnylam, MyoKardia/Bristol Myers Squibb, Cytokinetics, Neuroimmune, Intellia, Ionis, Bridgebio, Lexeo, Rocket, Attralus, and AstraZeneca; and has received research/educational grants to his institution from Pfizer, AstraZeneca, Novo Nordisk, BridgeBio, and Alnylam. Dr Hagège has received consulting/advisor fees from Alnylam, Amicus Therapeutics, Bayer, MyoKardia/Bristol Myers Squibb, Pfizer, and Sanofi Genzyme; and has received steering committee fees for SEQUOIA-HCM from Cytokinetics. Dr Januzzi is funded in part by the Hutter Family Professorship; is a Trustee of the American College of Cardiology; has served as a board member for Imbria Pharmaceuticals; has served as a Director at Jana Care; has received grant support from Abbott, Applied Therapeutics, HeartFlow, Innolife, and Roche Diagnostics; has received consulting fees from Abbott, Beckman, Bristol Myers Squibb, Boehringer Ingelheim, Janssen, Novartis, Pfizer, Merck, Roche Diagnostics, and Siemens; and has participated in clinical endpoint committees/data safety monitoring boards for Abbott, AbbVie, CVRx, Intercept, and Takeda. Dr Lee has received research grants through his institution from AstraZeneca, Boehringer Ingelheim, and Roche Diagnostics; has been a member of a Clinical Endpoints Committee for Bayer; and has been a member of the Trial Steering Committee for Cytokinetics. Dr Lewis has received research funding from the National Institutes of Health (R01-HL 151841, R01-HL131029, and R01-HL159514), American Heart Association (15GPSGC-24800006), Amgen, Cytokinetics, Applied Therapeutics, AstraZeneca, and SoniVie; has received honoraria for advisory boards from Pfizer, Merck, Boehringer Ingelheim, Novartis, American Regent, Cyclerion, Cytokinetics, and Amgen; and has received royalties from UpToDate for scientific content authorship related to exercise physiology. Dr Michels has received consulting/advisor fees from Bristol Myers Squibb, Cytokinetics, and Pfizer; and has received research grant funding from Bristol Myers Squibb. Dr Olivotto has received speakers’ bureau fees from Bristol Myers Squibb, Amicus, and Sanofi Genzyme; has received consulting/advisor fees from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Tenaya, Rocket Pharma, and Lexeo; and has received research grant funding from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Menarini International, Chiesi, and Boston Scientific. Dr Oreziak has received investigator fees from Cytokinetics and MyoKardia/Bristol Myers Squibb. Dr Owens has received consulting/advisor fees from Cytokinetics, Bristol Myers Squibb/MyoKardia. Dr Spertus is the principal investigator of grants from the NIH, Abbott Vascular, and the American College of Cardiology Foundation; has received consulting fees from Janssen, Novartis, Amgen, Myokardia, AstraZeneca, Bayer, and Merck; has served on the Scientific Advisory Board of United Healthcare and the Board of Directors for Blue Cross Blue Shield of Kansas City; owns the copyright to the KCCQ, SAQ, and PAQ; and has an equity interest in Health Outcomes Sciences. Dr Solomon has received consulting/advisor fees from Abbott, Action, Akros, Alnylam, Amgen, Arena, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Cardior, Cardurion, Corvia, Cytokinetics, Daiichi-Sankyo, GlaxoSmithKline, Lilly, Merck, MyoKardia, Novartis, Roche, Theracos, Quantum Genomics, Cardurion, Janssen, Cardiac Dimensions, Tenaya, Sanofi-Pasteur, DiNAQOR, Tremeau, CellProThera, Moderna, American Regent, Sarepta, Lexicon, Anacardio, Akros, and Puretech Health; and has received research grants from Actelion, Alnylam, Amgen, AstraZeneca, Bellerophon, Bayer, Bristol Myers Squibb, Celladon, Cytokinetics, Eidos, Gilead, GlaxoSmithKline, Ionis, Lilly, Mesoblast, MyoKardia, NIH/NHLBI, Neurotronik, Novartis, Novo Nordisk, Respicardia, Sanofi Pasteur, Theracos, and US2.AI. Dr Tfelt-Hansen has received consulting fees from Leo Pharma, MicroPort, and Johnson and Johnson. Ms van Sinttruije is a patient advisory committee member and a SEQUOIA-HCM Steering Committee member for Cytokinetics. Dr Watkins has received consulting/advisor fees from Cytokinetics, BioMarin, and BridgeBio. Drs Jacoby, Heitner, Kupfer, Malik, and Meng and Ms Wohltman are employees of Cytokinetics Incorporated and hold stock in Cytokinetics. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: A primary goal in treating obstructive hypertrophic cardiomyopathy (oHCM) is to improve patients' health status: their symptoms, function, and quality of life. The health status benefits of aficamten, a novel cardiac myosin inhibitor, have not been comprehensively described., Objectives: This study sought to determine the effect of aficamten on patient-reported health status, including symptoms of fatigue, shortness of breath, chest pain, physical and social limitations, and quality of life., Methods: SEQUOIA-HCM (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM) randomized symptomatic adults with oHCM to 24 weeks of aficamten (n = 142) or placebo (n = 140), followed by a 4-week washout. The Kansas City Cardiomyopathy Questionnaire (KCCQ) and Seattle Angina Questionnaire 7-item (SAQ7) were serially administered. Changes in mean KCCQ-Overall Summary Score (KCCQ-OSS) and SAQ7-Summary Score (SAQ7-SS) from baseline to 24 weeks and following treatment withdrawal were compared using linear regression adjusted for baseline scores and randomization strata. Proportions of patients with clinically important changes were compared., Results: Among 282 participants, the mean age was 59 ± 13 years, 115 (41%) were female, and 223 (79%) were White. Baseline KCCQ-OSS (69.3 ± 20.1 vs 67.3 ± 18.8) and SAQ7-SS (72.0 ± 21.0 vs 72.4 ± 18.3) were similar between aficamten and placebo groups. Treatment with aficamten, compared with placebo, improved both the mean KCCQ-OSS (13.3 ± 16.3 vs 6.1 ± 12.6; mean difference: 7.9; 95% CI: 4.8-11.0; P < 0.001) and SAQ7-SS (11.6 ± 17.4 vs 3.8 ± 14.4; mean difference: 7.8; 95% CI: 4.7-11.0; P < 0.001) at 24 weeks, with benefits emerging within 4 weeks. No heterogeneity in treatment effect was found across subgroups. A much larger proportion of participants experienced a very large health status improvement (≥20 points) with aficamten vs placebo (KCCQ-OSS: 29.7% vs 12.4%, number needed to treat: 5.8; SAQ7-SS: 31.2% vs 13.9%, number needed to treat: 5.8). Participants' health status worsened significantly more after withdrawal from aficamten than placebo (KCCQ-OSS: -16.2 ± 19.0 vs -3.0 ± 9.6; P < 0.001; SAQ7-SS: -17.4 ± 21.4 vs -2.5 ± 13.3), further confirming a causal effect of aficamten., Conclusions: In patients with symptomatic oHCM, treatment with aficamten resulted in markedly improved health status, including significant improvement in chest pain-related health status, than placebo. (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM [SEQUOIA-HCM]; NCT05186818)., Competing Interests: Funding Support and Author Disclosures The SEQUOIA-HCM study was funded by Cytokinetics, Incorporated. Study design and data analysis were supported by the funder and aided by coauthors. Manuscript drafting was completed independently but reviewed by the funder. Dr Sherrod has received support from the National Heart, Lung, and Blood Institute (award number T32HL110837). Dr Saberi has received consultant/advisor fees from Bristol Myers Squibb; and has received research grants from Bristol Myers Squibb, Cytokinetics, Novartis, and Actelion Pharmaceuticals. Dr Nassif has received research and grant support from AstraZeneca and Cytokinetics; and has received consulting/advisory fees from Vifor and Cytokinetics. Dr Coats has received speaker fees from Alnylam and Pfizer; and has received advisory fees from Cytokinetics and Roche Diagnostics. Dr Garcia-Pavia has received speaker fees from Pfizer, AstraZeneca, Novo Nordisk, Ionis, BridgeBio, Bristol Myers Squibb, Intellia, and Alnylam; has received consultant/advisor fees from Pfizer, Alnylam, MyoKardia/Bristol Myers Squibb, Cytokinetics, Neuroimmune, Intellia, Ionis, BridgeBio, Lexeo, Rocket, Attralus, and AstraZeneca; and has received research/educational grants to his institution from Pfizer, AstraZeneca, Novo Nordisk, BridgeBio, and Alnylam. Dr Januzzi has received funding from the Hutter Family Professorship; has served as a board member for Imbria Pharmaceuticals; has served as a Director at Jana Care; has received grant support from Abbott, Applied Therapeutics, HeartFlow, Innolife, and Roche Diagnostics; has received consulting income from Abbott, Beckman, Bristol Myers Squibb, Boehringer Ingelheim, Janssen, Novartis, Pfizer, Merck, Roche Diagnostics, and Siemens; and has participated in clinical endpoint committees/Data Safety Monitoring Boards for Abbott, AbbVie, CVRx, Intercept, and Takeda. Dr Lewis has received research funding from the National Institutes of Health (R01-HL 151841, R01-HL131029, and R01-HL159514), American Heart Association (15GPSGC-24800006), Amgen, Cytokinetics, Applied Therapeutics, AstraZeneca, and SoniVie; has received honoraria for Advisory Boards from Pfizer, Merck, Boehringer Ingelheim, Novartis, American Regent, Cyclerion, Cytokinetics, and Amgen; and has received royalties from UpToDate for scientific content authorship related to exercise physiology. Dr Maron has received consultant/advisor fees from Imbria, Edgewise, and BioMarin; and has received Steering Committee fees for SEQUIOA-HCM from Cytokinetics, Incorporated. Dr Olivotto has received Speakers Bureau fees from Bristol Myers Squibb, Amicus, and Genzyme; has received consultant/advisor fees from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Tenaya, Rocket Pharma, and Lexeo; and has received research grant funding from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Menarini International, Chiesi, and Boston Scientific. Drs Butzner, Jacoby, Heitner, Kupfer, Malik, and Meng, and Ms Wohltman are employees of Cytokinetics Incorporated; and hold stock in Cytokinetics Incorporated. Dr Spertus has provided consultative services on patient-reported outcomes and evidence evaluation to Alnylam, AstraZeneca, Bayer, Merck, Janssen, Bristol Myers Squibb, 4DT Medical, Terumo, Cytokinetics, Imbria, and United Healthcare; holds research grants from Bristol Myers Squibb, and Janssen; owns the copyrights to the Seattle Angina Questionnaire, Kansas City Cardiomyopathy Questionnaire, and Peripheral Artery Questionnaire; and has served on the Board of Directors for Blue Cross Blue Shield of Kansas City. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Obstructive hypertrophic cardiomyopathy (oHCM) is characterized by left ventricular (LV) hypertrophy, LV outflow tract obstruction, and left atrial dilation, which can be associated with progressive heart failure, atrial fibrillation, and stroke. Aficamten is a next-in-class cardiac myosin inhibitor that reduces outflow tract obstruction by modulating cardiac contractility, with the potential to reverse pathological remodeling and, in turn, reduce cardiovascular events., Objectives: This study sought to investigate the effect of aficamten on cardiac remodeling compared with placebo using cardiovascular magnetic resonance (CMR) and its association with key clinical endpoints in the SEQUOIA-HCM (Safety, Efficacy, and Quantitative Understanding of Obstruction Impact of Aficamten in HCM) CMR substudy., Methods: SEQUOIA-HCM was a phase 3 double-blind, placebo-controlled trial for adults with symptomatic oHCM who were randomized 1:1 to 24 weeks of aficamten (dose range: 5-20 mg) or placebo. Eligible participants were offered enrollment in the CMR substudy with studies performed at baseline and week 24. Image analysis was performed in a blinded fashion by a core laboratory., Results: Of the 282 randomized patients, 57 (20%) participated in the substudy, and of those, 50 (88%) completed both baseline and week 24 CMR. Baseline characteristics of the CMR cohort were similar to the overall study population. Of these 50 patients, 21 received aficamten and 29 received placebo. Relative to placebo, patients receiving aficamten demonstrated significant reductions (Δ least-squares mean) in LV mass index (-15 g/m 2 ; 95% CI: -25 to -6 g/m 2 ; P = 0.001), maximal LV wall thickness (-2.1 mm; 95% CI: -3.1 to -1.1 mm; P < 0.001), left atrial volume index (-13 mL/m 2 ; 95% CI: -19 to -7 mL/m 2 ; P < 0.001), native T1 relaxation time (-37 ms; 95% CI: -69 to -5 ms; P = 0.026), indexed extracellular volume fraction (-3.9 g/m 2 ; 95% CI: -7.0 to -0.9 g/m 2 ; P = 0.014), and indexed myocyte mass (-14 g/m 2 ; 95% CI: -23 to -4 g/m 2 ; P = 0.004), while there were no significant changes in LV chamber volumes, LV replacement fibrosis (late gadolinium enhancement mass -0.7 g; 95% CI: -2.9 to 1.6 g; P = 0.54), or extracellular volume (0.7%; 95% CI: -2.2% to 3.6%; P = 0.61)., Conclusions: The CMR substudy of SEQUOIA-HCM demonstrated that treatment with aficamten relative to placebo for 24 weeks resulted in favorable cardiac remodeling. These changes, particularly with regard to LV mass, wall thickness, and left atrial size, could potentially lead to reduced cardiovascular events including heart failure and atrial fibrillation with longer follow-up. (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM [SEQUOIA-HCM]; NCT05186818)., Competing Interests: Funding Support and Author Disclosures The SEQUOIA-HCM study was funded by Cytokinetics. Dr Masri has received research grants from Pfizer, Ionis, Attralus, and Cytokinetics; and has received fees from Cytokinetics, Bristol Myers Squibb, Eidos/BridgeBio, Pfizer, Ionis, Lexicon, Attralus, Alnylam, Haya, Alexion, Akros, Prothena, BioMarin, AstraZeneca, and Tenaya. Dr Coats has received speaker fees from Alnylam and Roche; and has received advisory fees from Cytokinetics. Dr Hegde has received fees paid to institution for core lab services from Bristol Myers Squibb and Cytokinetics. Dr Lee has received research grants through his employer, the University of Glasgow, from AstraZeneca, Boehringer Ingelheim, and Roche Diagnostics; and is a member of a Trial Steering Committee for Cytokinetics and the Clinical Endpoints Committee for Bayer. Dr Maron has received consulting/advisor fees from Imbria, Edgewise, and Biomarin; and has received steering committee fees for SEQUIOA-HCM from Cytokinetics. Dr Michels has received research grant support through her employer, the Erasmus Medical Center, from Bristol Myers Squibb; and has received fees from Cytokinetics, Bristol Myers Squibb, and Alnylam. Dr Olivotto has received research grants from Bristol Myers Squibb, Cytokinetics, Amicus, Genzyme, Shire Takeda, Menarini International, Chiesi, and Boston Scientific; and has received fees from Bristol Myers Squibb, Cytokinetics, Amicus, Genzyme, Shire Takeda, Menarini International, Chiesi, Boston Scientific, Tenaya, Rocket Pharma, and Lexeo. Dr Oreziak has received investigator fees from Cytokinetics and MyoKardia/Bristol Myers Squibb. Dr Jacoby, Dr Heitner, Dr Kupfer, Dr Malik, Ms Meng, and Ms Wohltman are employees of and own stock in Cytokinetics. Dr Solomon has received consulting/advisor fees from Abbott, Action, Akros, Alnylam, Amgen, Arena, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Cardior, Cardurion, Corvia, Cytokinetics, Daiichi-Sankyo, GlaxoSmithKline, Lilly, Merck, MyoKardia, Novartis, Roche, Theracos, Quantum Genomics, Cardurion, Janssen, Cardiac Dimensions, Tenaya, Sanofi Pasteur, Dinaqor, Tremeau, CellProThera, Moderna, American Regent, Sarepta, Lexicon, Anacardio, Akros, and Puretech Health; and has received research grants from Actelion, Alnylam, Amgen, AstraZeneca, Bellerophon, Bayer, Bristol Myers Squibb, Celladon, Cytokinetics, Eidos, Gilead, GlaxoSmithKline, Ionis, Lilly, Mesoblast, MyoKardia, National Institutes of Health/National Heart, Lung, and Blood Institute, Neurotronik, Novartis, Novo Nordisk, Respicardia, Sanofi Pasteur, Theracos, and US2.AI. Dr Kramer has received research grants from Bristol Myers Squibb and Eli Lilly; and has served as a consultant for Eli Lilly. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Aficamten, a next-in-class cardiac myosin inhibitor, improved peak oxygen uptake (pVO 2 ) and lowered resting and Valsalva left ventricular outflow (LVOT) gradients in adults with symptomatic obstructive hypertrophic cardiomyopathy (oHCM) in SEQUOIA-HCM (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM), a phase 3, multicenter, randomized, double-blinded, placebo-controlled study., Objectives: The authors sought to evaluate the effect of aficamten on echocardiographic measures of cardiac structure and function in SEQUOIA-HCM., Methods: Serial echocardiograms were performed over 28 weeks in patients randomized to receive placebo or aficamten in up to 4 individually titrated escalating doses (5-20 mg daily) over 24 weeks based on Valsalva LVOT gradients and left ventricular ejection fraction (LVEF)., Results: Among 282 patients (mean age 59 ± 13 years; 41% female, 79% White, 19% Asian), mean LVEF was 75% ± 6% with resting and Valsalva LVOT gradients of 55 ± 30 mm Hg and 83 ± 32 mm Hg, respectively. Over 24 weeks, aficamten significantly lowered resting and Valsalva LVOT gradients, and improved left atrial volume index, lateral and septal e' velocities, and lateral and septal E/e' (all P ≤ 0.001). LV end-systolic volume increased and wall thickness decreased (all P ≤ 0.003). Aficamten resulted in a mild reversible decrease in LVEF (-4.8% [95% CI: -6.4% to -3.3%]; P < 0.001) and absolute LV global circumferential strain (-3.7% [95% CI: 1.8%-5.6%]; P < 0.0010), whereas LV global longitudinal strain was unchanged. Several measures, including LVEF, LVOT gradients, and E/e' returned to baseline following washout. Among those treated with aficamten, improved pVO 2 and reduction in N-terminal pro-B-type natriuretic peptide (NT-proBNP) were associated with improvement in lateral e' velocity and septal and lateral E/e' (all P < 0.03), whereas improvement in Kansas City Cardiomyopathy Questionnaire Clinical Summary Scores (KCCQ-CSS) was associated with a decrease in both LVOT gradients (all P < 0.001)., Conclusions: Compared with placebo, patients receiving aficamten demonstrated significant improvement in LVOT gradients and measures of LV diastolic function, and several of these measures were associated with improvements in pVO 2 , KCCQ-CSS, and NT-proBNP. A modest decrease in LVEF occurred yet remained within normal range. These findings suggest aficamten improved multiple structural and physiological parameters in oHCM without significant adverse changes in LV systolic function. (Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic oHCM [SEQUOIA-HCM]; NCT05186818)., Competing Interests: Funding Support and Author Disclosures The SEQUOIA-HCM trial is funded by Cytokinetics, Incorporated. Representatives of Cytokinetics have been involved in the design and conduct of the study reported in this paper. Study design and data analysis was supported by the funder and aided by coauthors. Manuscript drafting was completed independently but reviewed by the funder. Dr Wang is supported by a ACC/Merck Research Fellowship. Dr Hegde’s and Dr Wang’s institutions have received fees for core lab services from Cytokinetics and Bristol Myers Squibb. Dr Masri has received research grants from Pfizer, Ionis, Attralus, and Cytokinetics; and has received fees from Cytokinetics, BMS, Eidos/BridgeBio, Pfizer, Ionis, Lexicon, Attralus, Alnylam, Haya, Alexion, Akros, Prothena, BioMarin, AstraZeneca, and Tenaya. Dr Nassif has received research and grant support from AstraZeneca and Cytokinetics; and has received consulting/advisory fees from Vifor and Cytokinetics. Dr Barriales-Villa has received consultant/advisor fees from MyoKardia/Bristol Myers Squibb. Dr Cardim has received speaker fees from Cytokinetics and Bristol Myers Squibb. Dr Coats has received speaker fees from Alnylam and Pfizer; and has received advisory fees from Cytokinetics and Roche Diagnostics. Dr Kramer has received research grants from Cytokinetics, BMS, and Eli Lilly; and is a consultant for Eli Lilly. Dr Maron has received consultant/advisor fees from Imbria and Takeda; and has received steering committee fees for SEQUOIA-HCM from Cytokinetics, Incorporated. Dr Michels’ institution has received a research grant from Bristol Myers Squibb; has received consultant/ advisor fees from Cytokinetics and Bristol Myers Squibb/Myokardia and Alnylam; and has received speaker fees from Bristol Myers Squibb and Pfizer. Dr Olivotto has received research grants from Bristol Myers Squibb, Cytotinetics, Sanofi, Benzyme, Amicus, Bayer, Menarini International, Chiesi, and Boston Scientific; has received consulting fees from Bristol Myers Squibb, Amicus, Sanofi, and Genzyme; and has served as an Advisory Board member for Cytokinetics, Bristol Myers Squibb, Chiesi, and Rocket Pharma. Dr Saberi has received consultant/advisor fees from Bristol Myers Squibb; and has received research grants from Cytokinetics, Bristol Myers Squibb, Cytokinetics, Novartis, and Actelion Pharmaceuticals. Drs Jacoby, Heitner, Kupfer, Meng, and Malik, and Ms Wohltman are employees of and hold stock in Cytokinetics, Incorporated. Dr Solomon has received research grants from Alexion, Alnylam, Applied Therapeutics, AstraZeneca, Bellerophon, Bayer, BMS, Boston Scientific, Cytokinetics, Edgewise, Eidos/Bridgebio, Gossamer, GSK, Ionis, Lilly, NIH/NHLBI, Novartis, NovoNordisk, Respicardia, Sanofi Pasteur, Tenaya, Theracos, and US2.AI; and has consulted for Abbott, Action, Akros, Alexion, Alnylam, Amgen, Arena, AstraZeneca, Bayer, BMS, Cardior, Cardurion, Corvia, Cytokinetics, GSK, Lilly, Novartis, Roche, Theracos, Quantum Genomics, Tenaya, Sanofi-Pasteur, Dinaqor, Tremeau, CellProThera, Moderna, American Regent, Sarepta, Lexicon, Anacardio, Akros, and Valo. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Importance: The ability to predict sudden cardiac death (SCD) in children and adolescents with hypertrophic cardiomyopathy (HCM) is currently inadequate. Late gadolinium enhancement (LGE) by cardiovascular magnetic resonance (CMR) imaging is associated with SCD events in adults with HCM., Objective: To examine the prognostic significance of LGE in patients with HCM who are younger than 21 years., Design, Setting, and Participants: This multicenter, retrospective cohort study was conducted from April 8, 2015, to September 12, 2022, in patients with HCM who were younger than 21 years and had undergone CMR imaging across multiple sites in the US, Europe, and South America. Observers of CMR studies were masked toward outcomes and demographic characteristics., Exposure: Natural history of HCM., Main Outcome and Measures: The primary outcome was SCD and surrogate events, including resuscitated cardiac arrest and appropriate discharges from an implantable defibrillator. Continuous and categorical data are expressed as mean (SD), median (IQR), or number (percentage), respectively. Survivor curves comparing patients with and without LGE were constructed by the Kaplan-Meier method, and likelihood of subsequent clinical events was further evaluated using univariate and multivariable Cox proportional hazards models., Results: Among 700 patients from 37 international centers, median (IQR) age was 14.8 (11.9-17.4) years, and 518 participants (74.0%) were male. During a median (IQR) [range] follow-up period of 1.9 (0.5-4.1) [0.1-14.8] years, 35 patients (5.0%) experienced SCD or equivalent events. LGE was present in 230 patients (32.9%), which constituted an mean (SD) burden of 5.9% (7.3%) of left ventricular myocardium. The LGE amount was higher in older patients and those with greater left ventricular mass and maximal wall thickness; patients with LGE had lower left ventricular ejection fractions and larger left atrial diameters. The presence and burden of LGE was associated with SCD, even after correcting for existing risk stratification tools. Patients with 10% or more LGE, relative to total myocardium, had a higher risk of SCD (unadjusted hazard ratio [HR], 2.19; 95% CI, 1.59-3.02; P < .001). Furthermore, the addition of LGE burden improved the performance of the HCM Risk-Kids score (before LGE addition: 0.66; 95% CI, 0.58-0.75; after LGE addition: 0.73; 95% CI, 0.66-0.81) and Precision Medicine in Cardiomyopathy score (before LGE addition: 0.68; 95% CI, 0.49-0.77; after LGE addition: 0.73; 95% CI, 0.64-0.82) SCD predictive models., Conclusions and Relevance: In this retrospective cohort study, quantitative LGE was a risk factor for SCD in patients younger than 21 years with HCM and improved risk stratification.

Importance: Impaired exercise capacity is a cardinal manifestation of obstructive hypertrophic cardiomyopathy (HCM). The Phase 3 Trial to Evaluate the Efficacy and Safety of Aficamten Compared to Placebo in Adults With Symptomatic Obstructive HCM (SEQUOIA-HCM) is a pivotal study characterizing the treatment effect of aficamten, a next-in-class cardiac myosin inhibitor, on a comprehensive set of exercise performance and clinical measures., Objective: To evaluate the effect of aficamten on exercise performance using cardiopulmonary exercise testing with a novel integrated measure of maximal and submaximal exercise performance and evaluate other exercise measures and clinical correlates., Design, Setting, and Participants: This was a prespecified analysis from SEQUOIA-HCM, a double-blind, placebo-controlled, randomized clinical trial. Patients were recruited from 101 sites in 14 countries (North America, Europe, Israel, and China). Individuals with symptomatic obstructive HCM with objective exertional intolerance (peak oxygen uptake [pVO2] ≤90% predicted) were included in the analysis. Data were analyzed from January to March 2024., Interventions: Randomized 1:1 to aficamten (5-20 mg daily) or matching placebo for 24 weeks., Main Outcomes and Measures: The primary outcome was change from baseline to week 24 in integrated exercise performance, defined as the 2-component z score of pVO2 and ventilatory efficiency throughout exercise (minute ventilation [VE]/carbon dioxide output [VCO2] slope). Response rates for achieving clinically meaningful thresholds for change in pVO2 and correlations with clinical measures of treatment effect (health status, echocardiographic/cardiac biomarkers) were also assessed., Results: Among 282 randomized patients (mean [SD] age, 59.1 [12.9] years; 115 female [40.8%], 167 male [59.2%]), 263 (93.3%) had core laboratory-validated exercise testing at baseline and week 24. Integrated composite exercise performance improved in the aficamten group (mean [SD] z score, 0.17 [0.51]) from baseline to week 24, whereas the placebo group deteriorated (mean [SD] z score, -0.19 [0.45]), yielding a placebo-corrected improvement of 0.35 (95% CI, 0.25-0.46; P <.001). Further, aficamten treatment demonstrated significant improvements in total workload, circulatory power, exercise duration, heart rate reserve, peak heart rate, ventilatory efficiency, ventilatory power, and anaerobic threshold (all P <.001). In the aficamten group, large improvements (≥3.0 mL/kg per minute) in pVO2 were more common than large reductions (32% and 2%, respectively) compared with placebo (16% and 11%, respectively). Improvements in both components of the primary outcome, pVO2 and VE/VCO2 slope throughout exercise, were significantly correlated with improvements in symptom burden and hemodynamics (all P <.05)., Conclusions and Relevance: This prespecified analysis of the SEQUOIA-HCM randomized clinical trial found that aficamten treatment improved a broad range of exercise performance measures. These findings offer valuable insight into the therapeutic effects of aficamten., Trial Registration: ClinicalTrials.gov Identifier: NCT05186818.

Background: This open-label phase 2 trial evaluated the safety and efficacy of aficamten in patients with nonobstructive hypertrophic cardiomyopathy (nHCM)., Methods: Patients with symptomatic nHCM (left ventricular outflow tract obstruction gradient ≤ 30 mmHg, left ventricular ejection fraction [LVEF] ≥ 60%, N-terminal pro-B-type natriuretic peptide [NT-proBNP] > 300 pg/mL) received aficamten 5-15 mg once daily (doses adjusted according to echocardiographic LVEF) for 10 weeks., Results: We enrolled 41 patients (mean ± SD age 56 ± 16 years; 59% female). At Week 10, 22 (55%) patients experienced an improvement of ≥ 1 New York Heart Association class; 11 (29%) became asymptomatic. Clinically relevant improvements in Kansas City Cardiomyopathy Questionnaire Clinical Summary Scores occurred in 22 (55%) patients. Symptom relief was paralleled by reductions in NT-proBNP levels (56%; P < 0.001) and high-sensitivity cardiac troponin I (22%; P < 0.005). Modest reductions in LVEF (mean ± SD) of -5.4% ± 10 to 64.6% ± 9.1 were observed. Three (8%) patients had asymptomatic reduction in LVEF < 50% (range: 41%-48%), all returning to normal after 2 weeks of washout. One patient with prior history of aborted sudden cardiac death experienced a fatal arrhythmia during the study., Conclusions: Aficamten administration for symptomatic nHCM was generally safe and was associated with improvements in heart failure symptoms and cardiac biomarkers., Trial Registration: ClinicalTrials.gov Identifier: NCT04219826., (Crown Copyright © 2024. Published by Elsevier Inc. All rights reserved.)

Competing Interests: Dr M. Maron serves as a consultant for Cytokinetics, iRhythm (with grant), Imbria Pharmaceuticals, and TAKEDA Pharmaceuticals (with grant). Dr Rowin serves as a consultant for Cytokinetics and iRhythm. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Background: In hypertrophic cardiomyopathy (HCM), 48-hour ambulatory monitoring has been standard practice to detect nonsustained ventricular tachycardia (NSVT), a sudden death risk marker. Extended-wear ambulatory electrocardiographic (ECG) devices have more recently used for monitoring patients with HCM., Objective: We aimed to evaluate NSVT burden identified with continuous ambulatory monitoring for up to 2 weeks compared with initial 48 hours., Methods: 236 consecutive patients with HCM (49 ± 12 years) underwent 14-day continuous ambulatory monitoring (Zio XT, iRhythm Technologies, San Francisco, CA); diagnostic yield of NSVT compared for initial 48 hours vs extended for 14 days., Results: Of the 236 patients, 114 (48%) had ≥ 1 runs of NSVT (median 2) over 14 days. Median length of NSVT was 7 beats (range: 3 to 67) at rates of 120 to 240 beats per minute (bpm) (median, 167 bpm). In 42 of the 114 patients (37%), initial NSVT occurred ≤ 48 hours and in 72 (63%) only during the extended monitoring period (3 to 14 days). Diagnostic yield for detecting NSVT over 14 days was 2.7-fold greater than ≤ 48 hours (P < .001). NSVT judged at higher risk (≥ 8 beats, > 200 bpm, ≥ 2 runs in consecutive 2-day period) was identified more frequently during extended monitoring, diagnostic yield over 14 days was 3-fold greater than ≤ 48 hours (P < .001)., Conclusion: In HCM, NSVT episodes are frequent; however, in most patients, both NSVT and higher-risk NSVT were not detected during initial 48 hours and were confined solely to extended monitoring period. These data support additional clinical studies to evaluate the significance of NSVT on extended monitoring on sudden death risk in HCM., Competing Interests: Disclosures Dr Maron has served as consultant for Cytokinetics, iRhythm (with grant), Imbria Pharmaceuticals, and TAKEDA Pharmaceuticals (with grant). Dr Rowin has received research funding from Pfizer and iRhythm. Dr Hsu and Dr Crosson are employees of iRhythm Technologies. Dr Turakhia has received research grants from Bristol Myers Squibb, American Heart Association, Bayer, Gilead Sciences, and the Food and Drug Administration and has received equity from iRhythm, Connect America, Forward, Evidently, PocketRN, AliveCor, and Hippocratic.ai. Dr Turakhia is an employee and corporate officer of iRhythm Technologies Inc. The other authors have no conflicts of interest to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Percutaneous left atrial appendage closure (LAAC) is an effective alternative strategy for stroke prevention in patients with atrial fibrillation (AF) at high risk for bleeding with anticoagulation (AC). Efficacy of this strategy in hypertrophic cardiomyopathy (HCM) remains uncertain., Objective: The study aimed to compare risk of stroke in HCM-AF patients treated with LAAC with those treated with AC., Methods: By use of the TriNetX Global Research Network, HCM-AF patients from 2015 to 2024 were assigned to categories of treatment with LAAC and treatment solely with AC and observed for 3 years for ischemic stroke, systemic embolism, and all-cause mortality. Propensity score matching was used to limit confounders., Results: Of 14,867 HCM-AF patients identified, 364 (2.5%) were treated with LAAC vs 14,503 (97.5%) treated with AC. HCM LAAC patients were older (72 vs 67 years; P < .001) and had more comorbidities and more prior bleeding events, including higher rate of prior gastrointestinal bleeding (68% vs 18%; P < .001), compared with HCM patients treated solely with AC. After propensity score matching, there was no baseline difference between groups including prior bleeding events (P > .05). During follow-up, HCM patients treated with LAAC had higher rates of ischemic stroke (13% vs 8%; hazard ratio, 1.9; P = .006) and systemic embolism (14% vs 9%; hazard ratio, 1.8; P = .006) but no difference in mortality compared with matched HCM patients receiving AC., Conclusion: These real-world data do not support percutaneous LAAC in HCM-AF patients as the primary treatment strategy during long-term AC to reduce stroke risk. However, LAAC may remain a reasonable option for HCM-AF patients who are unable to tolerate AC because of prohibitive bleeding risk., Competing Interests: Disclosures Martin S. Maron: consultant for Cytokinetics, iRhythm (with grant), Imbria Pharmaceuticals, Takeda Pharmaceuticals (with grant). Ethan J. Rowin: research funding from Pfizer, iRhythm. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Aficamten, a novel cardiac myosin inhibitor, reversibly reduces cardiac hypercontractility in obstructive hypertrophic cardiomyopathy. We present a prespecified analysis of the pharmacokinetics, pharmacodynamics, and safety of aficamten in SEQUOIA-HCM (Safety, Efficacy, and Quantitative Understanding of Obstruction Impact of Aficamten in HCM)., Methods and Results: A total of 282 patients with obstructive hypertrophic cardiomyopathy were randomized 1:1 to daily aficamten (5-20 mg) or placebo between February 1, 2022, and May 15, 2023. Aficamten dosing targeted the lowest effective dose for achieving site-interpreted Valsalva left ventricular outflow tract gradient <30 mm Hg with left ventricular ejection fraction (LVEF) ≥50%. End points were evaluated during titration (day 1 to week 8), maintenance (weeks 8-24), and washout (weeks 24-28), and included major adverse cardiac events, new-onset atrial fibrillation, implantable cardioverter-defibrillator discharges, LVEF <50%, and treatment-emergent adverse events. At week 8, 3.6%, 12.9%, 35%, and 48.6% of patients achieved 5-, 10-, 15-, and 20-mg doses, respectively. Baseline characteristics were similar across groups. Aficamten concentration increased by dose and remained stable during maintenance. During the treatment period, LVEF decreased by -0.9% (95% CI, -1.3 to -0.6) per 100 ng/mL aficamten exposure. Seven (4.9%) patients taking aficamten underwent per-protocol dose reduction for site-interpreted LVEF <50%. There were no treatment interruptions or heart failure worsening for LVEF <50%. No major adverse cardiovascular events were associated with aficamten, and treatment-emergent adverse events were similar between treatment groups, including atrial fibrillation., Conclusions: A site-based dosing algorithm targeting the lowest effective aficamten dose reduced left ventricular outflow tract gradient with a favorable safety profile throughout SEQUOIA-HCM., Registration: URL: https://www.clinicaltrials.gov; Unique Identifier: NCT05186818.

Background: Patients with hypertrophic cardiomyopathy (HCM) are at risk of sudden death, and individuals with ≥1 major risk markers are considered for primary prevention implantable cardioverter-defibrillators. Guidelines recommend cardiac magnetic resonance (CMR) imaging to identify high-risk imaging features. However, CMR imaging is resource intensive and is not widely accessible worldwide., Objective: The purpose of this study was to develop electrocardiogram (ECG) deep-learning (DL) models for the identification of patients with HCM and high-risk imaging features., Methods: Patients with HCM evaluated at Tufts Medical Center (N = 1930; Boston, MA) were used to develop ECG-DL models for the prediction of high-risk imaging features: systolic dysfunction, massive hypertrophy (≥30 mm), apical aneurysm, and extensive late gadolinium enhancement. ECG-DL models were externally validated in a cohort of patients with HCM from the Amrita Hospital HCM Center (N = 233; Kochi, India)., Results: ECG-DL models reliably identified high-risk features (systolic dysfunction, massive hypertrophy, apical aneurysm, and extensive late gadolinium enhancement) during holdout testing (c-statistic 0.72, 0.83, 0.93, and 0.76) and external validation (c-statistic 0.71, 0.76, 0.91, and 0.68). A hypothetical screening strategy using echocardiography combined with ECG-DL-guided selective CMR use demonstrated a sensitivity of 97% for identifying patients with high-risk features while reducing the number of recommended CMRs by 61%. The negative predictive value with this screening strategy for the absence of high-risk features in patients without ECG-DL recommendation for CMR was 99.5%., Conclusion: In HCM, novel ECG-DL models reliably identified patients with high-risk imaging features while offering the potential to reduce CMR testing requirements in underresourced areas., Competing Interests: Disclosures Dr Maron is a consultant for Cytokinetics, iRhythm, Imbria Pharmaceuticals, and Takeda Pharmaceuticals. Dr Rowin has received research funding from Pfizer and iRhythm. The remaining authors have nothing to disclose., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Purpose To develop a deep learning model for increasing cardiac cine frame rate while maintaining spatial resolution and scan time. Materials and Methods A transformer-based model was trained and tested on a retrospective sample of cine images from 5840 patients (mean age, 55 years ± 19 [SD]; 3527 male patients) referred for clinical cardiac MRI from 2003 to 2021 at nine centers; images were acquired using 1.5- and 3-T scanners from three vendors. Data from three centers were used for training and testing (4:1 ratio). The remaining data were used for external testing. Cines with downsampled frame rates were restored using linear, bicubic, and model-based interpolation. The root mean square error between interpolated and original cine images was modeled using ordinary least squares regression. In a prospective study of 49 participants referred for clinical cardiac MRI (mean age, 56 years ± 13; 25 male participants) and 12 healthy participants (mean age, 51 years ± 16; eight male participants), the model was applied to cines acquired at 25 frames per second (fps), thereby doubling the frame rate, and these interpolated cines were compared with actual 50-fps cines. The preference of two readers based on perceived temporal smoothness and image quality was evaluated using a noninferiority margin of 10%. Results The model generated artifact-free interpolated images. Ordinary least squares regression analysis accounting for vendor and field strength showed lower error ( P < .001) with model-based interpolation compared with linear and bicubic interpolation in internal and external test sets. The highest proportion of reader choices was "no preference" (84 of 122) between actual and interpolated 50-fps cines. The 90% CI for the difference between reader proportions favoring collected (15 of 122) and interpolated (23 of 122) high-frame-rate cines was -0.01 to 0.14, indicating noninferiority. Conclusion A transformer-based deep learning model increased cardiac cine frame rates while preserving both spatial resolution and scan time, resulting in images with quality comparable to that of images obtained at actual high frame rates. Keywords: Functional MRI, Heart, Cardiac, Deep Learning, High Frame Rate Supplemental material is available for this article. © RSNA, 2024.