Faculty Bibliography

BACKGROUND:Disopyramide, used in obstructive hypertrophic cardiomyopathy (oHCM) for its negative inotropic properties mediated by its reduction in cytosolic calcium, has been recommended for decades as an option to relieve resistant obstruction. Aficamten is a selective cardiac myosin inhibitor that reduces hypercontractility directly by reducing myosin-actin interaction. OBJECTIVES/OBJECTIVE:This study aims to investigate the safety and efficacy of concomitant use and withdrawal of disopyramide in patients with symptomatic oHCM receiving aficamten. METHODS:Patients with oHCM enrolled in REDWOOD-HCM Cohort 3 (open-label), SEQUOIA-HCM (placebo-controlled), and FOREST-HCM (open-label) were analyzed. The authors identified 4 groups, each with patients symptomatic despite background therapy with disopyramide who received: 1) disopyramide plus aficamten and subsequent aficamten withdrawal per protocol (Diso-Afi Withdrawal); 2) disopyramide plus placebo (Diso-Pbo); 3) aficamten plus disopyramide with subsequent disopyramide withdrawal (Afi-Diso Withdrawal); and 4) continued both disopyramide and aficamten (Diso+Afi Continuous). Assessments were performed at baseline, after aficamten or placebo add-on therapy, and after washout (except at week 24 for Diso+Afi Continuous group). RESULTS:Overall, 50 unique patients from 3 trials enrolled, resulting in 93 subjects (segments) across 4 groups: Diso-Afi Withdrawal (n = 29), Diso-Pbo (n = 20), Afi-Diso Withdrawal (n = 17), and Diso+Afi Continuous (n = 27); mean disopyramide dose was 331 ± 146 mg/d. The addition of aficamten to disopyramide alleviated left ventricular outflow tract (LVOT) obstruction (resting: change [Δ] in least squares mean -27.0 ± 3.6, Valsalva: Δ least squares mean -39.2 ± 5.0, both P < 0.0001), symptoms (≥1 NYHA functional class improvement: 77.8% [95% CI: 61.0-94.5]; P < 0.0001; Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score: 12.3 ± 3.3 [P < 0.001]), and reduced N-terminal pro-B-type natriuretic peptide ratio: 0.35 [95% CI: 0.26-0.48]; P < 0.0001, and there was no significant change with placebo. Withdrawal of aficamten while on disopyramide resulted in return of LVOT obstruction, worsening of symptoms, and increase in NT-proBNP to baseline values. Conversely, withdrawal of disopyramide while on aficamten did not impact efficacy. There were no safety events associated with aficamten or disopyramide withdrawal, and no episodes of atrial fibrillation after disopyramide withdrawal. CONCLUSIONS:In this cohort of patients with symptomatic oHCM with persistent LVOT obstruction, combination therapy with aficamten and disopyramide was safe and well tolerated but did not enhance clinical efficacy vs aficamten alone. For such oHCM patients, aficamten treatment may be considered with an option to discontinue disopyramide. (Dose-finding Study to Evaluate the Safety, Tolerability, PK, and PD of CK-3773274 in Adults With HCM [REDWOOD-HCM]; NCT04219826) (Aficamten vs Placebo in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy [SEQUOIA-HCM]; NCT05186818) (Open-label Extension Study to Evaluate the Long-term Safety and Tolerability of Aficamten in Adults With HCM [FOREST-HCM]; NCT04848506).

Hypertrophic cardiomyopathy is a common but underrecognized cardiac disorder characterized by a heterogenous phenotype that includes increased left ventricular thickness, outflow obstruction, diastolic dysfunction, and arrhythmia. Hypertrophic cardiomyopathy is often heritable and associated with pathogenic variants in sarcomeric genes. While not curable, an integrated approach involving medical, interventional, and surgical care can have a considerable impact on disease burden, quality of life, and mortality. This review provides a practical overview of important topics in hypertrophic cardiomyopathy, including evaluation of differential diagnosis, imaging, provocation of left ventricular outflow obstruction, treatment of obstructive and nonobstructive hypertrophic cardiomyopathy with negative inotropic therapy and myosin inhibition, as well as surgical and interventional approaches to septal reduction and mitral valve intervention.

BACKGROUND:Disopyramide is used to treat heart failure symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM) with known medium-term efficacy and safety, while long-term outcomes are unknown. METHODS AND RESULTS/RESULTS:=0.51). Ventricular tachyarrhythmias and left ventricular systolic dysfunction were uncommon (n=3 and n=1) and were not attributed to disopyramide. Death on disopyramide was exceedingly rare (n=3 [5%]) and non-HCM-related occurring at age ≥90 years. CONCLUSIONS:In patients with obstructive HCM, disopyramide is safe and effective at relieving heart failure symptoms from outflow obstruction in a subgroup of patients who were maintained on disopyramide for >5 years.

BACKGROUND:Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac disease. Signaling pathways that link genetic sequence variants to clinically overt HCM and progression to severe forms of HCM remain unknown. OBJECTIVES/OBJECTIVE:The purpose of this study was to identify signaling pathways that are differentially regulated in HCM, using proteomic profiling of human myocardium, confirmed with transcriptomic profiling. METHODS:In this multicenter case-control study, myocardial samples were obtained from cases with HCM and control subjects with nonfailing hearts. Proteomic profiling of 7,289 proteins from myocardial samples was performed using the SomaScan assay (SomaLogic). Pathway analysis of differentially expressed proteins was performed, using a false discovery rate <0.05. Pathway analysis of proteins whose concentrations correlated with clinical indicators of severe HCM (eg, reduced left ventricular ejection fraction, atrial fibrillation, and ventricular tachyarrhythmias) was also executed. Confirmatory analysis of differentially expressed genes was performed using myocardial transcriptomic profiling. RESULTS:The study included 99 HCM cases and 15 control subjects. Pathway analysis of differentially expressed proteins revealed dysregulation of the Ras-mitogen-activated protein kinase, ubiquitin-mediated proteolysis, angiogenesis-related (eg, hypoxia-inducible factor-1, vascular endothelial growth factor), and Hippo pathways. Pathways known to be dysregulated in HCM, including metabolic, inflammatory, and extracellular matrix pathways, were also dysregulated. Pathway analysis of proteins associated with clinical indicators of severe HCM and of differentially expressed genes supported these findings. CONCLUSIONS:The present study represents the most comprehensive (>7,000 proteins) and largest-scale (n = 99 HCM cases) proteomic profiling of human HCM myocardium to date. Proteomic profiling and confirmatory transcriptomic profiling elucidate dysregulation of both newly recognized (eg, Ras-mitogen-activated protein kinase) and known pathways associated with pathogenesis and progression to severe forms 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/OBJECTIVE: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).

BACKGROUND:This open-label phase 2 trial evaluated the safety and efficacy of aficamten in patients with non-obstructive 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 5-20 mg once daily (doses adjusted according to echocardiographic LVEF) for 10 weeks. RESULTS:41 patients were enrolled (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 (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 associated with improvements in heart failure symptoms and cardiac biomarkers. TRIAL REGISTRATION/BACKGROUND:ClinicalTrials.gov Identifier: NCT04219826 LAY SUMMARY: Non-obstructive hypertrophic cardiomyopathy (nHCM) is a disease in which the heart muscle becomes abnormally thickened. There are no proven medical therapies. Aficamten is a new cardiac myosin inhibitor designed to target the underlying cause of HCM. REDWOOD-HCM Cohort 4 was the first study exploring the efficacy and safety of aficamten in people with symptoms from nHCM. Most patients reported improved health and functional status. There was also significant decrease in blood levels of biomarkers indicating excessive pressure within the heart and damage to heart muscle cells. These results support a larger placebo-controlled study of aficamten for people with nHCM (ACACIA-HCM).

BACKGROUND/UNASSIGNED:There is controversy about risk of malignant arrhythmias and stroke in patients with apical aneurysms in hypertrophic cardiomyopathy (HCM). OBJECTIVES/UNASSIGNED:The aim of this study was to estimate the associations of aneurysm size and major HCM risk factors with the incidence of lethal and potentially lethal arrhythmias and to estimate incidence of unexplained stroke. METHODS/UNASSIGNED:In 108 patients (age 57.4 ± 13.5 years, 37% female) from 3 HCM centers, we assessed American Heart Association/American College of Cardiology guidelines risk factors and initial aneurysm size by echocardiography and cardiac magnetic resonance imaging and assessed outcomes after median 5.9 (IQR: 3.7-10.0) years. RESULTS/UNASSIGNED:and also without risk factors VT, VF, or SCD occurred in only 2.5%. Clinical atrial fibrillation (AF) was prevalent, occurring in 49 (45%). Stroke was commonly associated with AF. Stroke without conventional cause had an incidence of 0.5%/year. Surgery in 19% was effective in reducing symptoms. VT ablation and surgery were moderately effective in preventing recurrent VT. CONCLUSIONS/UNASSIGNED:Risk factors and aneurysm size were associated with subsequent VT, VF, or SCD. Patients with aneurysms in the lowest tercile of size have a low cumulative 5-year risk. Clinical AF occurred frequently. Stroke prevalence in absence of known stroke etiologies is uncommon and comparable to risk of severe bleeding.

BACKGROUND:Latent left ventricular outflow tract obstruction (LVOTO) is an important cause of symptoms in patients with hypertrophic cardiomyopathy (HCM) but can be challenging to provoke. OBJECTIVES AND METHODS/OBJECTIVE:To examine the value of postprandial resting and stress echocardiography and utilization of invasive or enhanced drug therapies (surgical myectomy, alcohol septal ablation, disopyramide, and mavacamten) in patients with postprandial LVOTO. Consecutive HCM patients without LVOTO underwent routine and postprandial echocardiography at rest, with provocation (Valsalva and standing) and after symptom-limited treadmill stress. RESULTS:Among 252 patients (mean age, 58 years, 39% women), postprandial LVOT gradients were higher compared with routine echocardiography at rest (median, 9.0 [0-38.0] vs 0 [0-14.0] mm Hg; P < .0001) and with provocation (18.5 [0-70.3] vs 1.5 [0-41.0] mm Hg; P < .0001). Postprandial exercise stress echocardiogram (PPXSE) gradients were higher in a subset of 44 patients who underwent both postprandial and fasting stress echocardiography (47.0 [5.3-81.0] vs 17.5 [0-46.0] mm Hg; P < .0001). In total, 49 (19.5%) patients achieved the ≥50 mm Hg threshold under routine conditions (rest/provocation); 90 (35.7%) additional patients achieved postprandial gradients ≥50 mm Hg (rest/provocation/exercise), 38 (15.1%) with PPXSE alone. A total of 71 patients were treated with 91 invasive or enhanced drug therapies, 32 (45.1%) of whom had gradients ≥50 mm Hg only after eating (rest/provocation) and 8 (11.3%) only with PPXSE, with symptom relief in the majority. CONCLUSIONS:Postprandial echocardiography was useful at unmasking LVOTO in more than one-third of patients who did not have high gradients otherwise. Eating before echocardiography is a powerful provocative tool in the evaluation of patients with HCM.