Faculty Bibliography

BACKGROUND/UNASSIGNED:Implanted cardioverter-defibrillators (ICDs) have been used in patients with hypertrophic cardiomyopathy (HCM) to prevent sudden death, and have proven lifesaving for many patients. However, experience with ICD therapy has largely been derived from relatively small HCM cohorts confined to specific countries or regions of the world. Therefore, we sought to determine the effectiveness of ICDs in preventing sudden death due to life-threatening ventricular arrhythmias in a large international multicenter HCM population. METHODS/UNASSIGNED:Databases from 25 HCM centers (8 in the United States, 9 in Europe, 4 in Asia, and 1 each in Australia, Africa, Mexico, and South America) were retrospectively interrogated to identify consecutive patients with HCM with ICDs (1992 to 2024) followed for 7±6 years (up to 32 years) for clinical outcomes. RESULTS/UNASSIGNED:A total of 3387 patients were identified (63% men). They had a mean left ventricular thickness of 22±7 mm. The participants had received ICDs at a mean age of 47±17 years. Over follow-up, 550 patients (16%) experienced ≥1 appropriate ICD therapy (2.6%/y), including 86 of the 247 implanted for secondary prevention (35% [6.4%/y]) and 464 of the 3140 implanted for primary prevention (15% [2.2%/y]). Appropriate therapy occurred in the 464 primary prevention patients at a mean age of 49±17 years, with a median time to first appropriate therapy of 4 years after ICD implantation; 16% of these received their first appropriate therapy ≥10 years after implantation, and 47% experienced multiple interventions. Independent predictors of appropriate ICD therapy included unexplained syncope, left ventricular apical aneurysms, left ventricular systolic dysfunction, and nonsustained ventricular tachycardia on ambulatory monitoring. Of the 3140 primary prevention patients, 2946 survived (94%) and 194 died (6%) (0.8%/y), including 68 due to HCM (0.3%/y), predominantly of end-stage heart failure (n=43) or stroke (n=9). In contrast, 11 patients (0.4%) died suddenly, with device failures occurring in 2.4% of those with life-threatening ventricular tachyarrhythmias. Survival free from HCM-related mortality at 10 and 20 years was 97% and 91%, respectively. CONCLUSIONS/UNASSIGNED:In this international multicenter study, the largest to date, including >3300 consecutive patients with HCM and ICDs, device therapy terminated potentially lethal ventricular tachyarrhythmias in 1 of 6 patients, with low HCM-related mortality rates for patients with ICDs. These novel data demonstrate the effectiveness of the ICD initiative, which has probably favorably altered the natural history of many patients with HCM worldwide.

BACKGROUND/UNASSIGNED:Nonobstructive hypertrophic cardiomyopathy (nHCM) is associated with significant morbidity with no approved treatment. Aficamten is a cardiac myosin inhibitor targeting excess contractility and diastolic impairment, the predominant mechanism responsible for adverse outcomes in nHCM. In the ACACIA-HCM trial (Assessment Comparing Aficamten to Placebo on Cardiac Endpoints in Adults With Non-Obstructive HCM; URL: https://www.clinicaltrials.gov; Unique identifier: NCT06081894), aficamten significantly improved outcomes in patients with nHCM versus placebo. To contextualize the observed treatment effects, we performed a responder analysis integrating multiple clinically relevant measures. METHODS/UNASSIGNED:Patients with symptomatic nHCM were randomized to daily aficamten (n=258) or placebo (n=259) assessed at week 36, including (1) symptom burden (≥1 improvement in New York Heart Association class or reported improvement in Patient Global Impression of Change); (2) exercise capacity (≥0.5 mL/kg per min in peak oxygen uptake); (3) >10% decrease in left atrial volume index; (4) >10% improvement in septal early diastolic mitral annular velocity (e'); (5) ≥50% reduction in NT-proBNP (N-terminal pro-B-type natriuretic peptide). Overall clinical response was classified by the number of favorable outcomes achieved: nonresponder (none), limited (1 or 2), partial (3 or 4), or complete (all 5). RESULTS/UNASSIGNED:<0.001). CONCLUSIONS/UNASSIGNED:In patients with nHCM, aficamten was associated with improvements across a broad range of clinically relevant measures including symptom burden and diastolic function. These results underscore a potential benefit of aficamten in the population of patients with nHCM. REGISTRATION/UNASSIGNED:URL: https://www.clinicaltrials.gov; Unique identifier: NCT06081894.

BACKGROUND/UNASSIGNED:Aficamten significantly improved both functional capacity and patient-reported health status in patients with symptomatic nonobstructive hypertrophic cardiomyopathy in the phase 3 randomized, placebo-controlled ACACIA-HCM trial (Assessment Comparing Aficamten to Placebo on Cardiac Endpoints in Adults with Non-Obstructive HCM; NCT06081894). Serial echocardiographic examinations may provide insights into the mechanisms underlying the therapeutic effect of aficamten in this prespecified exploratory analysis. METHODS/UNASSIGNED:Symptomatic patients with nonobstructive hypertrophic cardiomyopathy were randomized 1:1 to receive aficamten (range, 5-20 mg, titration based on left ventricular [LV] ejection fraction) or placebo for up to 72 weeks (end of treatment). The effect of aficamten on echocardiographic measures at 36 weeks (time of primary end point) and end of treatment was assessed with linear regression models adjusted for baseline values, intracavity obstruction, and baseline atrial fibrillation. RESULTS/UNASSIGNED:=0.022). Aficamten demonstrated incremental improvements in measures of LV structure and function compared to placebo as doses were increased, with improvement in diastolic indices evident by week 2 of titration. CONCLUSIONS/UNASSIGNED:In patients with nonobstructive hypertrophic cardiomyopathy, aficamten improved echocardiographic measures of diastolic function. These findings suggest that the benefits of aficamten extend beyond the effects of LV outflow tract gradient reduction observed in prior studies. REGISTRATION/UNASSIGNED:URL: https://www.clinicaltrials.gov; Unique identifier: NCT06081894.

BACKGROUND:Nonobstructive hypertrophic cardiomyopathy (HCM) is a common condition that is associated with substantial morbidity and no proven medical therapy. Whether treatment with aficamten, a cardiac myosin inhibitor, can benefit patients with this condition is unknown. METHODS:In this phase 3, multinational, double-blind trial, we randomly assigned adults with symptomatic nonobstructive HCM in a 1:1 ratio to receive aficamten (starting dose, 5 mg; maximum dose, 20 mg) or placebo for up to 72 weeks. The dual primary end points were the change from baseline to week 36 in peak oxygen uptake and in the Kansas City Cardiomyopathy Questionnaire clinical summary score (KCCQ-CSS; range, 0 to 100, with higher scores indicating better health status). RESULTS:A total of 258 patients were assigned to receive aficamten and 259 to receive placebo. The mean age of the patients was 55.1 years, and 53.6% were women. At 36 weeks, the change in the KCCQ-CSS was 11.4 points (95% confidence interval [CI], 9.6 to 13.2) in the aficamten group and 8.4 points (95% CI, 6.6 to 10.2) in the placebo group (least-squares mean difference, 3.0 points; 95% CI, 0.5 to 5.5; P = 0.02). The mean change in the peak oxygen uptake at week 36 was 0.64 ml per kilogram of body weight per minute (95% CI, 0.32 to 0.95) in the aficamten group and -0.03 ml per kilogram per minute (95% CI, -0.35 to 0.28) in the placebo group (least-squares mean difference, 0.67 ml per kilogram per minute; 95% CI, 0.22 to 1.11; P = 0.003). Reversible reductions in left ventricular ejection fraction to less than 50% occurred in 27 patients (10.5%) receiving aficamten and in 2 patients (0.8%) receiving placebo. Serious adverse events occurred in 52 patients (20.2%) and 38 patients (14.7%), respectively. CONCLUSIONS:Among patients with symptomatic nonobstructive HCM, treatment with aficamten resulted in a significantly greater change in exercise capacity and patient-reported health status than placebo at 36 weeks. (Funded by Cytokinetics; ACACIA-HCM ClinicalTrials.gov number, NCT06081894.).

BACKGROUND/UNASSIGNED:The conventional view holds that left ventricular (LV) apical ballooning in stress cardiomyopathy is caused by a hyperadrenergic state related to emotional or physical stress. However, some suggest ballooning also occurs in obstructive hypertrophic cardiomyopathy (HCM) when obstruction becomes severe. Nearly all cases of apical ballooning in HCM were reported in patients with LV outflow tract obstruction. Herein, we present a case due to mid-ventricular obstruction. CASE SUMMARY/UNASSIGNED:A 52-year-old woman presented with dyspnoea and chest pain. She denied any recent emotional or physical stress. Physical examination was notable for a Grade 2/6 systolic murmur along the left sternal border. The peak high-sensitivity troponin level was 315 ng/L (normal < 6 ng/L). Coronary angiography was unremarkable. Echocardiography revealed LV apical ballooning with severely reduced LV ejection fraction. In addition, there was severe septal hypertrophy with mid-cavity obstruction. Continuous-wave Doppler interrogation across the obstruction revealed a bifid ('lobster claw') configuration with a characteristic abrupt early systolic drop in flow velocity. The patient was treated with beta-blockers. Follow-up examination revealed resolution of apical ballooning. DISCUSSION/UNASSIGNED:We believe apical ballooning in our patient with HCM resulted from severe afterload mismatch (produced by mid-cavity obstruction) and supply-demand ischaemia, as well as the limited contractile reserve that characterizes myopathic muscle. This is supported by the rapid decline in early systolic flow velocity seen with Doppler interrogation (lobster claw configuration) across the obstruction.

BACKGROUND:Apical aneurysms in hypertrophic cardiomyopathy (HCM) have been linked to sudden cardiac death (SCD) and a nidus for thromboembolism. Uncertainty remains regarding the level of risk and significance of aneurysm size. OBJECTIVES/OBJECTIVE:The objective of the study was to determine the rate of SCD events and prevalence of apical thrombus or embolic events by size (maximum transverse dimension). METHODS:Apical aneurysms were identified in 510 patients from 10 centers, followed a median of 4.1 years for SCD events (SCD, appropriate implantable cardioverter defibrillator therapy, and resuscitated SCD) or development of apical thrombus/thromboembolism. Relationship between size and SCD events was analyzed using multivariable Cox proportional hazard models. RESULTS:In 510 HCM patients: 19% had small aneurysms (<10 mm), 39% medium (10-19 mm), 39% large (20-39 mm), and 3% very large (≥40 mm). SCD event rate was 2.1%/year, with risk increasing with increasing aneurysm size: 0.2%/year in small, 2.3%/year in medium, 3.0%/year in large and 8.2%/year in very large (P < 0.001). On multivariable analysis, greater size was associated with SCD events, independent of other risk markers or European Society of Cardiology-SCD score. Either an embolic event (3.6% of patients) or apical thrombus (10% of patients) occurred in 13% of patients and was independently associated with greater aneurysm size, 3% in small to 25% in very large aneurysms (P < 0.001). CONCLUSIONS:In a large cohort of HCM patients with apical aneurysms, rates of SCD events were high, with continuous relationship between size and risk. Small aneurysms (<10 mm) were associated with low risk for SCD events (0.2%/year), whereas aneurysms ≥10 mm with high risk (>2%/year). Although embolic events were uncommon, increasing aneurysm size was associated with the prevalence of apical thrombi.

IMPORTANCE/UNASSIGNED: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/UNASSIGNED: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/UNASSIGNED: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/UNASSIGNED: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/UNASSIGNED: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/UNASSIGNED: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/UNASSIGNED:These results provide prospective evidence for incorporating cardiac magnetic resonance and NT-proBNP in the evaluation of patients with hypertrophic cardiomyopathy. TRIAL REGISTRATION/UNASSIGNED:ClinicalTrials.gov Identifier: NCT01915615.

MR imaging is increasingly used in evaluation of patients with known or suspected hypertrophic cardiomyopathy (HCM), as it provides useful information on cardiac structure, function, and tissue characterization that is complementary to echocardiography. While the adverse effect of left ventricle (LV) outflow tract obstruction on blood flow patterns is well characterized by the midsystolic drop in LV ejection velocities and flow, flow patterns in HCM with mid-LV obstruction, with or without apical aneurysm, are less well characterized. MR imaging can provide additional information on alterations of blood flow patterns in these HCM phenotypes and "paradoxic" flows associated with apical aneurysms.