Desai, Milind Y.

Importance Current risk prediction guidelines for hypertrophic cardiomyopathy predict only sudden cardiac death and are imperfect, leading to avoidable deaths and unnecessary implantable cardioverter defibrillators. Objective To combine prospectively collected clinical history, imaging, genetic, and biomarker data to improve risk prediction of adverse events in hypertrophic cardiomyopathy. Design, Setting, and Participants A total of 2750 patients with hypertrophic cardiomyopathy were prospectively enrolled in the registry-based study from 44 sites in North America and Europe with expertise in hypertrophic cardiomyopathy and cardiac magnetic resonance (CMR) imaging. Participants were enrolled from April 1, 2014, to April 7, 2017. Exposures Patients underwent a health history questionnaire, blood sampling for biomarkers and genotyping, and contrast-enhanced CMR. Patients were followed up yearly by telephone and through records review regarding event documentation. Main Outcomes and Measures The predefined composite adjudicated primary end point was time to first event for hypertrophic cardiomyopathy–related deaths; nonfatal sustained ventricular arrhythmias (VAs) requiring cardioversion or defibrillation; and left ventricular (LV) assist device implant or heart transplant. A secondary end point was a composite of sudden cardiac death and nonfatal VA events. The elastic-net method identified the most important predictors. Cox proportional hazards regression assessed associations with time to the first end point. Results Of the 2750 prospectively enrolled patients, 2698 (98%) had analyzable data after 9 were excluded because they had hypertrophic cardiomyopathy phenocopies and 43 withdrew. Of these remaining patients, 1919 (71%) were male, mean age was 50 years (SD, 11 years), and 423 (16%) were from underrepresented racial and minority groups. The mean follow-up was 6.9 years (SD, 2.1 years). The primary event model in 104 patients included LV scar as a percentage of LV mass by late gadolinium enhancement (LGE%; hazard ratio [HR], 1.86; 95% CI, 1.58-2.20; P < .001), LV mass index (HR, 1.09; 95% CI, 1.01-1.17; P = .03), LV end-systolic volume index (HR, 1.28; 95% CI, 1.12-1.46; P < .001 ), all per 10-unit increase, history of heart failure at study entry (HR, 2.89; 95% CI, 1.75-4.77; P < .001), and log N-terminal pro–B-type natriuretic peptide (NT-proBNP; HR, 1.41; 95% CI, 1.17-1.70; P < .001) level per log unit, (C index for all, 0.77). An LGE percentage of the LV mass of 9% or higher substantially increased the primary composite event rate ( P = .001). The secondary sudden cardiac death and VA risk factor model (in 69 patients) included LGE%, LV mass index, LV ejection fraction, and log(NT-proBNP) (C index, 0.76). Conclusions and Relevance These results provide prospective evidence for incorporating cardiac magnetic resonance and NT-proBNP in the evaluation of patients with hypertrophic cardiomyopathy. Trial Registration ClinicalTrials.gov Identifier: NCT01915615

Abstract This brief report details the initial findings from a Phase 1b/2 trial of TN-201, an adeno-associated virus serotype 9 (AAV9) gene therapy for MYBPC3-associated hypertrophic cardiomyopathy (HCM), a condition with significant morbidity, increased risk of mortality, and no approved therapy for the majority of patients. TN-201 was well tolerated, and changes to the management of potential immune responses resulted in a shorter period of immunosuppression. These results show consistent transduction and expression of TN-201 in cardiomyocytes, corresponding with increases in MyBP-C levels, reductions or stabilization of cardiac biomarkers, and reductions in key measures of left ventricular (LV) hypertrophy.

BACKGROUND: In severely symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM), VALOR-HCM trial (Study to Evaluate Mavacamten in Adults With Symptomatic Obstructive HCM Who Are Eligible for Septal Reduction Therapy [URL: https://clinicaltrials.gov ; Unique identifier: NCT04349072]) reported that mavacamten reduced the short-term need for septal reduction therapy (SRT). The current report examined the longer-term effect of mavacamten through end of treatment at week 128. METHODS: A double-blind randomized placebo-controlled multicenter trial at 19 sites in the United States included symptomatic obstructive HCM patients referred for SRT (enrollment July 2020 through October 2021). The group initially randomized to mavacamten continued the drug for 128 weeks and the placebo to mavacamten group from week 16 to 128 (112-week exposure). Dose titrations were performed using echocardiographic left ventricular outflow tract gradient and left ventricular ejection fraction measurements. The principal end point was proportion of patients proceeding with SRT or remaining guideline-eligible at week 128. RESULTS: At week 128, 17 of 108 (15.7%) patients in the total study sample met the composite end point (7 underwent SRT, 1 was SRT-eligible, and 9 SRT-status unevaluable). Additionally, 87 of 108 (80.5%) patients demonstrated ≥1 New York Heart Association class improvement by week 128, and 52 of 108 (48.1%) demonstrated ≥2, with a sustained reduction in resting and Valsalva left ventricular outflow tract gradients of 38.2 mm Hg and 59.4 mm Hg, respectively. Ninety-five of 108 (88%) patients transitioned to commercial mavacamten. Overall, 15 of 108 (13.8%) patients (5.41 per 100 patient-years) had an left ventricular ejection fraction <50% (2 with left ventricular ejection fraction ≤30%; 1 death). Of these, 12 of 15 (80%) continued treatment. New-onset atrial fibrillation occurred in 11 (10.2%) patients (4.55 per 100 patient-years). CONCLUSIONS: In severely symptomatic obstructive HCM patients, sustained freedom from SRT was observed at 128 weeks, with nearly 90% patients remaining on long-term mavacamten. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04349072.

Abstract Background In severely symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM), the VALOR-HCM phase 3 randomized, double-blind, placebo-controlled clinical trial demonstrated that mavacamten, reduces the need for septal reduction therapy with sustained improvement in left ventricular outflow tract gradients and symptoms. As a cardiac myosin inhibitor, mavacamten’s mechanism of action reduces myocardial hypercontractility. Global longitudinal strain (GLS), a measure of regional myocardial function, is a more sensitive marker of systolic function and can complement left ventricular ejection fraction (LVEF). Objective We sought to assess serial changes in LV and right ventricular (RV)-GLS in patients enrolled in the VALOR-HCM study. Methods VALOR-HCM included 112 symptomatic obstructive HCM patients (mean 60 years, 51% male, LVEF 68%). Patients assigned to mavacamten at baseline continued the drug for 56 weeks (n=56) and those assigned to placebo crossed over to mavacamten (n=52) from week 16-56 (40-week exposure). LV and RV-GLS assessment was performed according to the current American and European guideline recommendations using a vendor-neutral post processing software. Non-foreshortened apical (4, 3 and 2-chamber) views were used to obtain peak value of LV-GLS. For RV-GLS, RV focused 4-chamber view was used to calculate RV 4-chamber and free wall strain. A more negative strain value is favorable. Results Serial changes in LVEF, average LV-GLS, and RV-GLS (4-chamber and free wall) from baseline to week 56 are shown in the Figure. Despite preserved LVEF at baseline, average baseline LV-GLS was abnormal. There were significant and continued improvements in LV-GLS in the total group from baseline to week 56. 12 patients had transient reduction in LVEF (&lt;50%) requiring temporary drug interruption (permanent discontinuation in 3). The LV-GLS in this subgroup was worse at baseline compared to the total study population, with no significant worsening from baseline through week 56. In the overall population, excluding these 12 patients, LV-GLS demonstrated an improvement sustained through week 56. Both free wall and 4-chamber RV-GLS were abnormal at baseline and remained unchanged from baseline to week 56. Conclusions In the VALOR-HCM trial, despite hypercontractile LVEF at baseline, average baseline LV-GLS was worse than normal reference values. Treatment with mavacamten resulted in an improvement in LV-GLS from baseline through Week 56 (with no significant worsening of LV-GLS in the subgroup who experienced any reduction in LVEF &lt;50%), suggesting a favorable long-term impact on regional LV systolic function due to the reduction of cardiac hypercontractility. Additionally, there was no significant detrimental impact on RV systolic function on serial GLS assessment.Serial changes in LV and RV GLS in VALOR

Abstract Background In severely symptomatic patients with obstructive hypertrophic cardiomyopathy (HCM), the VALOR-HCM phase 3 randomized, double-blind, placebo-controlled clinical trial demonstrated that mavacamten, a cardiac myosin inhibitor, reduces the eligibility for septal reduction therapy with sustained improvement in left ventricular (LV) outflow tract gradients and symptoms. Mavacamten also resulted in favorable cardiac remodeling, including improvement in left atrial volume index (LAVI), LV diastolic function, and biomarkers (NT-proBNP and troponin T). However, the impact of mavacamten on LA function is not known. Objective We sought to assess serial changes in LA strain measures in patients enrolled in the VALOR-HCM trial. Methods VALOR-HCM included 112 symptomatic obstructive HCM patients (mean age 60 years, 51% male). Patients assigned to mavacamten at baseline (n=56) continued therapy for 56 weeks and those assigned to placebo crossed over to mavacamten (n=52) from week 16-56 (40-week exposure). Echocardiographic LA strain assessment was performed according to the current American and European guideline recommendations, using a vendor-neutral post processing software. For assessment of LA strain components (reservoir, conduit, and contraction), the non-foreshortened apical 4-chamber view was utilized. The zero reference was set at end-diastole. Results Serial changes in LAVI and all components of mean LA strain from baseline to week 56 are shown in the Figure. At baseline, LAVI and all mean LA strain values were worse than reported normal mean thresholds. There was a continued and significant improvement in all 3 LA strain values, from baseline to week 56, along with a significant reduction in LAVI. Improvement in LAVI was seen earlier than improvements in LA strain. There was a significant inverse correlation between change in mean LAVI and LA reservoir strain from baseline to week 56 (r= -0.42, p&lt;0.001). Conclusions In the VALOR-HCM trial, average LAVI and baseline LA strain values were significantly worse than reported normal thresholds. Treatment with mavacamten resulted in an improvement in LAVI and LA strain values from baseline through week 56 suggesting a sustained favorable impact on cardiac remodeling. The advantageous cardiac remodeling associated with long-term treatment with mavacamten may in turn have a favorable impact on the observed high burden of atrial tachyarrhythmias in HCM.Serial changes in LA strain in VALOR-HCM

BACKGROUND: In severely symptomatic patients with obstructive hypertrophic cardiomyopathy, VALOR-HCM (A Study to Evaluate Mavacamten in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy Who Are Eligible for Septal Reduction Therapy) demonstrated that mavacamten reduces the need for septal reduction therapy with sustained improvement in left ventricular (LV) outflow tract gradients and symptoms. Global longitudinal strain (GLS), a measure of regional myocardial function, is a more sensitive marker of systolic function. In VALOR-HCM, we assessed serial changes in LV and right ventricular (RV) strain. METHODS: VALOR-HCM included 112 patients with symptomatic obstructive hypertrophic cardiomyopathy (mean, 60 years; 51% male; LV ejection fraction, 68%). Patients assigned to mavacamten at baseline continued the drug for 56 weeks (n=56) and those assigned to placebo (n=52) transitioned to mavacamten from weeks 16 to 56 (40-week exposure). LV-GLS and RV-GLS assessment was performed using a vendor-neutral software. Non-foreshortened apical (4-, 3-, and 2-chamber) views were used to obtain peak LV-GLS. RV focused 4-chamber view was used to calculate RV 4-chamber and free wall strain. A more negative strain value is favorable. RESULTS: At baseline, the mean LV-GLS, RV 4-chamber, and free wall strain values were −14.7%, −22.2%, and −16.8%, respectively (all worse than reported normal means). In the total study sample, LV-GLS significantly improved from baseline to week 56 ( P =0.02). Twelve patients had transient reduction in LV ejection fraction (<50%) requiring temporary drug interruption (including 3 permanent discontinuations). The LV-GLS in this subgroup was worse at baseline versus total study population (−11.4%), with no significant worsening from baseline through week 56 ( P =0.64). Both free wall and 4-chamber RV-GLS remained unchanged from baseline to week 56 ( P =0.62 and P =0.56, respectively). CONCLUSIONS: In VALOR-HCM, treatment with mavacamten improved LV-GLS from baseline through week 56 (with no significant worsening of LV-GLS in patients with a reduction in LV ejection fraction ≤50%), suggesting a favorable long-term impact on regional LV systolic function. Additionally, there was no detrimental impact on RV systolic function. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04349072.

Background: Treatment of progressive heart failure, due to left ventricular (LV) outflow tract obstruction has been a major component of hypertrophic cardiomyopathy (HCM) disease management for 50 years. Septal myectomy has been the primary treatment option to abolish gradients and relieve heart failure symptoms. The role of myectomy in HCM management has depended on effectiveness in relieving heart failure symptoms, but also an acceptable operative risk. Methods: Over the most recent 15-year period, we reviewed 3,700 consecutive isolated myectomy operations performed at major North American HCM institutions. Composite operative mortality (first 30 days) was only 0.4%. Seventeen operative deaths were at ages 24 to 82 (≥70 years), and only 6 occurred after 2010. Notably, 2 of the 4 Mayo Clinic deaths were in patients with prior alcohol septal ablation. Septal myectomy, when performed in experienced HCM centers, was much safer when compared to operative mortality with coronary artery bypass grafting (2.3%); valve replacement (3.5%); mitral valve replacement specifically (5.7%) (STS Database), similar to atrial or ventricular septal defect closure and 15-fold less than myectomy in community hospital or low volume surgical settings. Conclusions: Surgical myectomy performed in dedicated HCM centers with experienced surgeons and staff is one of the safest open-heart procedures currently practiced, with a mortality rate as low as 0.4%. The large mortality discrepancy for myectomy between community hospitals and dedicated HCM centers underscores that this operation should be considered a specialized procedure best performed in high volume HCM institutions.

Introduction: The performance of automated left ventricular ejection fraction (LVEF) assessment in patients with altered cardiac chamber geometry, such as those with obstructive hypertrophic cardiomyopathy (HCM), is not well described. Aims: Accurate assessment of LVEF is required for dose titration and continuation of myosin inhibitors in obstructive HCM. From the VALOR-HCM trial (NCT04349072), the agreement of two commercially available software packages was compared with blinded core lab assessment of LVEF. Methods: From baseline and week 16, among 112 patients randomized to either mavacamten or placebo, 178 echocardiograms were analyzed. Representative clips were manually selected, and automated LVEFs were calculated. Comparisons of LVEFs were made using Pearson’s correlation coefficients and Bland-Altman analysis. Results: With core lab assessment, the overall median LVEF was 68% (Q1 66%, Q3 70%). The correlation with vendor 1 was moderate (r = 0.47, 95% CI 0.35-0.58, p <0.001) and weak with vendor 2 (r =0.21, 95% CI 0.07-0.35, p =0.004). Correlation was also weak between vendor 1 and 2 (r = 0.14, 95% CI 0.00-0.28, p = 0.06). Vendors 1 and 2 had an underestimation bias of LVEF of 8% (95% CI 6-9%) and 8% (95% CI 7-9%), respectively, compared to core lab LVEF (Figure 1). Conclusions: In VALOR-HCM, the concordance of LVEF between different commercially available software packages with each other and with a core lab assessment was limited. Further study is needed to evaluate and improve the performance of automated LVEF tools in obstructive HCM patients who have altered cardiac chamber geometry.

Importance There is an unmet need for novel medical therapies before recommending invasive therapies for patients with severely symptomatic obstructive hypertrophic cardiomyopathy (HCM). Mavacamten has been shown to improve left ventricular outflow tract (LVOT) gradient and symptoms and may thus reduce the short-term need for septal reduction therapy (SRT). Objective To examine the cumulative longer-term effect of mavacamten on the need for SRT through week 56. Design, Setting, and Participants This was a double-blind, placebo-controlled, multicenter, randomized clinical trial with placebo crossover at 16 weeks, conducted from July 2020 to November 2022. Participants were recruited from 19 US HCM centers. Included in the trial were patients with obstructive HCM (New York Heart Association class III/IV) referred for SRT. Study data were analyzed April to August 2023. Interventions Patients initially assigned to mavacamten at baseline continued the drug for 56 weeks, and patients taking placebo crossed over to mavacamten from week 16 to week 56 (40-week exposure). Dose titrations were performed using echocardiographic LVOT gradient and LV ejection fraction (LVEF) measurements. Main Outcome and Measure Proportion of patients undergoing SRT, remaining guideline eligible or unevaluable SRT status at week 56. Results Of 112 patients with highly symptomatic obstructive HCM, 108 (mean [SD] age, 60.3 [12.5] years; 54 male [50.0%]) qualified for the week 56 evaluation. At week 56, 5 of 56 patients (8.9%) in the original mavacamten group (3 underwent SRT, 1 was SRT eligible, and 1 was not SRT evaluable) and 10 of 52 patients (19.2%) in the placebo crossover group (3 underwent SRT, 4 were SRT eligible, and 3 were not SRT evaluable) met the composite end point. A total of 96 of 108 patients (89%) continued mavacamten long term. Between the mavacamten and placebo-to-mavacamten groups, respectively, after 56 weeks, there was a sustained reduction in resting (mean difference, −34.0 mm Hg; 95% CI, −43.5 to −24.5 mm Hg and −33.2 mm Hg; 95% CI, −41.9 to −24.5 mm Hg) and Valsalva (mean difference, −45.6 mm Hg; 95% CI, −56.5 to −34.6 mm Hg and −54.6 mm Hg; 95% CI, −66.0 to −43.3 mm Hg) LVOT gradients. Similarly, there was an improvement in NYHA class of 1 or higher in 51 of 55 patients (93%) in the original mavacamten group and in 37 of 51 patients (73%) in the placebo crossover group. Overall, 12 of 108 patients (11.1%; 95% CI, 5.87%-18.60%), which represents 7 of 56 patients (12.5%) in the original mavacamten group and 5 of 52 patients (9.6%) in the placebo crossover group, had an LVEF less than 50% (2 with LVEF ≤30%, one of whom died), and 9 of 12 patients (75%) continued treatment. Conclusions and Relevance Results of this randomized clinical trial showed that in patients with symptomatic obstructive HCM, mavacamten reduced the need for SRT at week 56, with sustained improvements in LVOT gradients and symptoms. Although this represents a useful therapeutic option, given the potential risk of LV systolic dysfunction, there is a continued need for close monitoring. Trial Registration ClinicalTrials.gov Identifier: NCT04349072