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Background: In patients with hypertrophic cardiomyopathy (HCM), impaired augmentation of stroke volume and diastolic dysfunction contribute to exercise intolerance. Systolic-diastolic (S-D) coupling characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during early diastole. Impaired S-D coupling may contribute to the impaired cardiac response to exercise in patients with HCM., Methods: Patients with HCM (n = 25, age = 47 ± 9 years) and healthy adults (n = 115, age = 49 ± 10 years) underwent a cardiopulmonary exercise testing (CPET) and echocardiogram. S-D coupling was defined as the ratio of LV longitudinal excursion of the mitral annulus during early diastole (ED exc ) and systole (S exc ) and compared between groups. Peak oxygen uptake (peak V̇O 2 ) (Douglas bags), cardiac index (C 2 H 2 rebreathe), and stroke volume index (SVi) were assessed during CPET. Linear regression was performed between S-D coupling and peak V̇O 2 , peak cardiac index, and peak SVi., Results: S-D coupling was lower in HCM (Controls: 0.63 ± 0.08, HCM: 0.56 ± 0.10, p < 0.001). Peak V̇O 2 and stroke volume reserve were lower in patients with HCM (Peak VO 2 Controls: 28.5 ± 5.5, HCM: 23.7 ± 7.2 mL/kg/min, p < 0.001, SV reserve: Controls 39 ± 16, HCM 30 ± 18 mL, p = 0.008). In patients with HCM, S-D coupling was associated with peak V̇O 2 (r = 0.47, p = 0.018), peak cardiac index (r = 0.60, p = 0.002), and peak SVi (r = 0.63, p < 0.001)., Conclusion: Systolic-diastolic coupling was impaired in patients with HCM and was associated with fitness and the cardiac response to exercise. Inefficient S-D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM., (© 2024 The Author(s). Echocardiography published by Wiley Periodicals LLC.)

Background Moderate intensity exercise training (MIT) is safe and effective for patients with hypertrophic cardiomyopathy, yet the efficacy of high intensity training (HIT) remains unknown. This study aimed to compare the efficacy of HIT compared with MIT in patients with hypertrophic cardiomyopathy. Methods and Results Patients with hypertrophic cardiomyopathy were randomized to either 5 months of MIT, or 1 month of MIT followed by 4 months of progressive HIT. Peak oxygen uptake (V˙O 2 ; Douglas bags), cardiac output (acetylene rebreathing), and arteriovenous oxygen difference (Fick equation) were measured before and after training. Left ventricular outflow gradient and volumes were measured by echocardiography. Fifteen patients completed training (MIT, n=8, age 52±7 years; HIT, n=7, age 42±8 years). Both HIT and MIT improved peak V˙O 2 by 1.3 mL/kg per min ( P =0.009). HIT (+1.5 mL/kg per min) had a slightly greater effect than MIT (+1.1 mL/kg per min) but with no statistical difference (group×exercise P =0.628). A greater augmentation of arteriovenous oxygen difference occurred with exercise (Δ1.6 mL/100 mL P =0.005). HIT increased left ventricular end-diastolic volume (+17 mL, group×exercise P =0.015) compared with MIT. No serious arrhythmias or adverse cardiac events occurred. Conclusions This randomized trial of exercise training in patients with hypertrophic cardiomyopathy demonstrated that both HIT and MIT improved fitness without clear superiority of either. Although the study was underpowered for safety outcomes, no serious adverse events occurred. Exercise training resulted in salutary peripheral and cardiac adaptations. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03335332.

Background: Left ventricular outflow tract (LVOT) obstruction is a major determinant of heart failure symptoms in obstructive hypertrophic cardiomyopathy (oHCM). Aficamten, a next-in-class cardiac myosin inhibitor, may lower gradients and improve symptoms in these patients., Objectives: This study aims to evaluate the safety and efficacy of aficamten in patients with oHCM., Methods: Patients with oHCM and LVOT gradients ≥30 mm Hg at rest or ≥50 mm Hg with Valsalva were randomized 2:1 to receive aficamten (n = 28) or placebo (n = 13) in 2 dose-finding cohorts. Doses were titrated based on gradients and ejection fraction (EF). Safety and changes in gradient, EF, New York Heart Association functional class, and cardiac biomarkers were assessed over a 10-week treatment period and after a 2-week washout., Results: From baseline to 10 weeks, aficamten reduced gradients at rest (mean difference: -40 ± 27 mm Hg, and -43 ± 37 mm Hg in Cohorts 1 and 2, P = 0.0003 and P = 0.0004 vs placebo, respectively) and with Valsalva (-36 ± 27 mm Hg and -53 ± 44 mm Hg, P = 0.001 and <0.0001 vs placebo, respectively). There were modest reductions in EF (-6% ± 7.5% and -12% ± 5.9%, P = 0.007 and P < 0.0001 vs placebo, respectively). Symptomatic improvement in ≥1 New York Heart Association functional class was observed in 31% on placebo, and 43% and 64% on aficamten in Cohorts 1 and 2, respectively (nonsignificant). With aficamten, N-terminal pro-B-type natriuretic peptide was reduced (62% relative to placebo, P = 0.0002). There were no treatment interruptions and adverse events were similar between treatment arms., Conclusions: Aficamten resulted in substantial reductions in LVOT gradients with most patients experiencing improvement in biomarkers and symptoms. These results highlight the potential of sarcomere-targeted therapy for treatment of oHCM., Competing Interests: Funding Support and Author Disclosures The REDWOOD-HCM study was funded by Cytokinetics, Incorporated. Dr Maron has received consultant/advisor fees from Imbria and Takeda; and has received steering committee fees for REDWOOD-HCM from Cytokinetics, Incorporated. 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 Wheeler Foundation. Dr Olivotto has received Speakers Bureau fees from Boston Scientific, Amicus, and Novartis; has received consultant/advisor fees from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, and Tenaya; and has received research grant funding from Bristol Myers Squibb, Cytokinetics, Sanofi Genzyme, Amicus, Bayer, Menarini International, and Boston Scientific. 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 Wang has received Speakers Bureau fees from Bristol Myers Squibb; has received consultant/advisor fees from Bristol Myers Squibb and Cytokinetics; and has received research grants from Bristol Myers Squibb, Cytokinetics, and Abbott Vascular. Dr Garcia-Pavia has received Speakers Bureau fees from Pfizer and Alnylam; has received consultant/advisor fees from Pfizer, Alnylam, MyoKardia/Bristol Myers Squibb, Cytokinetics, Neuroimmune, BridgeBio, Attralus, and AstraZeneca; and has received research/educational grants to his institution from Pfizer, BridgeBio, and Alnylam. Dr Lakdawala has received consultant/advisor fees from Tenaya, Pfizer, Bristol Myers Squibb, Cytokinetics, and Sarepta; and has received a research grant from Pfizer. Dr Rader has received Speakers Bureau fees from Bristol Myers Squibb and Medtronic; and has received consultant/advisor fees from Bristol Myers Squibb, Cytokinetics, ReCor, and Medtronic. Dr Turer has received consultant/advisor fees from Cytokinetics. Dr Coats has received consultant/advisor fees from Cytokinetics. Dr Fifer has received consultant/advisor fees from Cytokinetics; and has received research grants from Bristol Myers Squibb and Novartis. Dr Owens has received consultant/advisor fees from Cytokinetics, Bristol Myers Squibb/MyoKardia, and Pfizer. Dr Solomon has received consultant/advisor fees from Abbott, Action, Akros, Alnylam, Amgen, Arena, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol Myers Squibb, Cardior, Cardurion, Corvia, Cytokinetics, Daiichi-Sankyo, GSK, 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, GSK, Ionis, Lilly, Mesoblast, MyoKardia, NIH/NHLBI, Neurotronik, Novartis, NovoNordisk, Respicardia, Sanofi Pasteur, Theracos, and US2.AI. Dr Watkins has received consultant/advisor fees from Cytokinetics, BioMarin, and BridgeBio. Dr Barriales-Villa has received consultant/advisor fees from MyoKardia/Bristol Myers Squibb. Dr Kramer has received consultant/advisor fees from Cytokinetics, and Bristol Myers Squibb; and has received research grants from Cytokinetics and Bristol Myers Squibb. Dr Wong has received Speakers Bureau fees from Projects in Knowledge, PCM Scientific; and has served as an unpaid consultant/advisor for Bristol Myers Squibb and Cytokinetics. Drs Heitner, Kupfer, Malik, Meng, and Wohltman are employees of Cytokinetics Incorporated; and holds stock in Cytokinetics Incorporated. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Patients with hypertrophic cardiomyopathy (HCM) often have reduced exercise capacity, and it is unclear whether cardiovascular regulation during exercise is intact in these patients. We aimed to determine the relationship between cardiac output (Q̇ c ) and oxygen uptake (V̇o 2 ), and stroke volume (SV) reserve in HCM compared with healthy participants and participants with left ventricular hypertrophy (LVH) but not HCM. Sixteen patients with HCM (48 ± 7 yr, 44% female), 16 participants with LVH (49 ± 5 yr, 44% female), and 61 healthy controls (CON: 52 ± 5 yr, 52% female) completed submaximal steady-state treadmill exercise followed by a maximal exercise test. V̇o 2 , Q̇ c , SV, and arteriovenous oxygen difference were measured during rest and exercise, and Q̇ c /V̇o 2 slopes were constructed, The Q̇ c /V̇o 2 slope was blunted in HCM compared with CON and LVH [HCM 4.9 ± 0.7 vs. CON 5.5 ± 1.0 ( P = 0.027) vs. LVH 6.0 ± 1.0 AU ( P = 0.002)] and participants with HCM had a lower SV reserve (HCM 53 ± 33%, controls 83 ± 33%, LVH 82 ± 22%; HCM vs. controls P = 0.002; HCM vs. LVH P = 0.015). Despite a blunted Q̇ c /V̇o 2 slope, 75% of patients with HCM achieved ≥80% predicted V̇o 2max by augmenting a-vo 2 difference at maximal exercise (16.0 ± 0.8 mL/100 mL vs. 13.8 ± 2.7 mL/100 mL, P = 0.021). Patients with HCM do not appropriately match Q̇ c to metabolic demand, primarily due to inadequate stroke volume augmentation. Despite this central limitation, many patients achieve normal exercise capacities by significantly increasing peripheral oxygen extraction. NEW & NOTEWORTHY Through state-of-the-art hemodynamic and oxygen uptake methodologies, this study found the cardiac output response to increasing metabolic demand is blunted among patients with hypertrophic cardiomyopathy (HCM), primarily due to a reduced stroke volume reserve. Many patients with HCM augment their peripheral oxygen extraction during maximal exercise to achieve normal exercise capacity and overcome ineffective matching of cardiac output. Peripheral adaptations that compensate for cardiac limitations may contribute to the heterogeneity of functional limitations observed within this patient population.

Background: Dyspnea and the resulting functional impairment are a common complication in hypertrophic cardiomyopathy (HCM). The relationship between physician-perceived functional status, patient-perceived health status, and objective exercise test results has not been evaluated in this condition., Purpose: To evaluate the correlation between the Kansas City Cardiomyopathy Questionnaire (KCCQ) and (1) physician's perceived (NYHA class) and (2) objective measurement (cardiopulmonary exercise test) of functional capacity in patients with HCM., Methods: In 24 outpatients with HCM at a single, referral center, the KCCQ instrument was administered and cardiopulmonary exercise testing (CPX) was performed. Severity of symptoms as determined by physician (NYHA classification) and patient (KCCQ instrument) was obtained before exercise test results were known. Pearson correlation was used to assess the independent correlation between KCCQ score and the various exercise parameters; Spearman correlation was used to assess correlation between KCCQ score and NYHA class., Results: KCCQ results demonstrated moderate reductions in all domains, with greatest reduction in quality-of-life domain. CPX testing showed reduction in peak oxygen consumption (mean absolute VO2 20.5 ± 7.8 ml/kg/min and percent predicted VO2 76.8 ± 4.1 %). There were negative correlations between NYHA class and all KCCQ components except the self-efficacy score. The strongest correlations were between NYHA class and the overall summary score (r = -0.623, p = 0.001) as well as the physical limitation score (r = -0.604, p = 0.002). Similarly, there were statistically significant positive correlations between the KCCQ components and percent predicted peak VO2. The strongest correlation was between percent predicted peak VO2 and the physical limitation score (r = 0.474, p = 0.019), but there was also correlation between percent predicted peak VO2 and the quality-of-life score (r = 0.456, p = 0.025), the functional status score (r = 0.455, p = 0.025), and the clinical summary score (r = 0.444, p = 0.030)., Conclusions: The multiple domains of the KCCQ provide data on patient-perceived health status, which correlate with physician-perceived and objective measurement of functional capacity in HCM. Additional studies are needed to evaluate the sensitivity of the KCCQ to changes in functional capacity over time or in response to therapies for this condition.

Unlabelled: Aim The presence of septal hypertrophy in hypertrophic cardiomyopathy (HCM) is common. To date, there has been no accepted classification of septal morphology in HCM. Furthermore, the possible relationship between septal morphology and clinical features of HCM is undefined., Methods and Results: Seventy-five consecutive adult patients with HCM were enrolled. Septal morphologies were retrospectively categorized into one of four patterns of hypertrophy based on transthoracic echocardiography. Left ventricular diastolic function by Doppler echocardiography and late gadolinium enhancement (LGE) by magnetic resonance imaging were assessed in all patients. Patients were followed for a mean of 45 ± 32 months. Catenoid septum was the most common morphologic subtype (46 of 75, 61%), followed by simple sigmoid (22 of 75, 29%), neutral (4 of 75, 5%), and apical (3 of 75, 4%). Inter-observer reproducibility of septal classifications was high (κ = 0.95). Patients with the catenoid subtype presented at a younger age, had worse diastolic function, and high rates of LGE. The presence of catenoid septal morphology was independently associated with LGE in multivariable logistic regression analysis. Implantable cardioverter-defibrillator implantation for prevention of sudden cardiac death occurred only in patients with this septal morphology., Conclusion: We propose a simple, reproducible classification system of patterns of septal hypertrophy in HCM. These patterns of hypertrophy are associated with significant differences in clinical, haemodynamic, and myocardial characteristics. Further studies are needed to evaluate the relationship between septal morphology and outcome or response to therapies in HCM.