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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

Once considered rare and essentially untreatable with a grim prognosis and reduced life expectancy, hypertrophic cardiomyopathy (HCM) has evolved substantially over 6 decades. Ultimately, HCM has become a contemporary global disease with pharmacologic and interventional options offering effective personalized treatment for all adverse disease pathways. Striking reduction in HCM‐related mortality to ≤0.5%/year in optimally treated cohorts is now comparable to that expected in the US general population, lower than most other disease risks to living, and 10‐fold less than the earliest estimates. The few deaths directly related to HCM are now largely attributable to advanced (end‐stage) heart failure in patients with nonobstructive HCM. Determinants of this transformation to a lower risk disease are evident in hallmark clinical inflection points and breakthroughs, including dedicated HCM programs assembling large clinical databases in which focused (and unfunded) physician‐investigators have derived data directly from patients in clinical practice. Evidence‐based observational studies report emergence of contemporary treatment strategies enhancing survival: implantable defibrillators prevent arrhythmic sudden death globally with 95% sensitive patient selection using an American Heart Association/American College Cardiology risk stratification algorithm; low‐risk, high‐benefit surgical myectomy reverses outflow obstruction and heart failure in >90% with a long‐term survival benefit; and aggressive anticoagulation has reduced embolic strokes. Recent novel pharmacologic alternatives (cardiac myosin inhibitors) are proving effective in relieving obstruction/symptom burden and changing disease management. These principles and time‐tested patient‐centered research strategies uniquely tailored to the heterogeneous HCM clinical spectrum are pivotal in providing practice insights, offering a vulnerable population more optimistic prognosis including opportunity to achieve normal longevity not available to prior generations of patients.

Abstract Background The functional significance of the left ventricular (LV) hypercontractile phenotype (HP) in hypertrophic cardiomyopathy (HCM) remains unclear. Purpose To assess the systemic and coronary hemodynamic correlates of HP in HCM. Methods We enrolled 1533 HCM patients (age 51 ± 15 years, 965 males, 63%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 27 laboratories from 13 countries. Two-dimensional volumetric TTE assessment included LV outflow tract gradient (LVOTG), end-diastolic volume (EDV), end-systolic volume (ESV), EF, and LV force (systolic blood pressure + LVOTG/ESV, mmHg/mL). Coronary flow velocity in the mid-distal left anterior descending (LAD) coronary artery was assessed in 325 patients. HP was defined as the highest quartile of the force (> 7.32 mmHg/ml). Results Force was moderately related to EF (r = 0.48, p < 0.0001) and weakly to LVOTG (r = 0.36, p < 0.0001). Compared to non-HP patients, HP showed higher heart rate (72 ± 14 vs 67 ± 14 beats per minute, p <0.0001), lower stroke volume (50 ± 22 vs 67 ± 22 ml, p < 0.0001), larger left atrial volume index (44 ± 16 vs 40 ± 16 ml/m2, p = 0.011) and higher coronary flow velocity in the LAD (n = 325, 41 ± 12 vs 37 ± 14 cm/s, p = 0.021), see Figure. Abnormal B-lines (≥ 2) were present in 11 of the 39 HP compared to 39 of the 271 non-HP patients (28% vs 14 %, p = 0.05). E/e’ ratio was higher in HP (n = 59) vs. non-HP (n = 571) patients (11 ± 5.4 vs 9.6 ± 4.2, p = 0.018). Conclusion In patients with HCM, preserved EF, and no history of coronary artery disease, HP identified by resting TTE with supernormal LV force was associated with an unfavorable systemic hemodynamic and coronary flow profile. Compared to non-HP HCM patients, the HP was characterized by reduced stroke volume, impaired diastolic function, and increased resting coronary flow velocity. HP may reflect inefficient myocardial mechanics, with disproportionate energy expenditure mirrored by higher resting coronary flow despite reduced stroke volume generation, ultimately contributing to adverse remodeling and worse prognosisNon-HP vs HP LAVI and coronary LAD flow

Abstract Background The presence of the significant left ventricular outflow tract gradient (LVOTG) changes clinical symptoms, prognosis and treatment in hypertrophic cardiomyopathy enabling the classification into its obstructive (HOCM) and non-obstructive form (non-HOCM). However, the more detailed functional characteristics and comparison of these forms remains poorly known. Purpose To compare the demographic, clinical and echocardiographic features between non-HOCM (defined as LVOTG < 30 mmHg) and HOCM patients enrolled into multi-centred study in years 1996-2024 as well as to analyse their long –term prognosis in relation to registered LVOTG. Methods We enrolled 1533 HCM patients (age 51 ± 15 years, 965 males, 63%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 27 centers, nevertheless quantitative assessment of LVOTG was available in 1252 patients. Survival analysis was performed in a subset of 1200 patients with follow-up information. Beyond standard TTE, the number of B-lines, the maximal diastolic velocity of coronary flow in left anterior descending artery (LAD) as well as left ventricular force defined as the ratio of systolic blood pressure plus LVOTG divided by left ventricular end-systolic volume was assessed with specification of hypercontractile phenotype (HP) as the highest force quartile. Additionally age and sex matched control group was included. Results Compared to non-HOCM patients, HOCM showed a bit higher body mass index (27 ± 4 vs 26 ± 4 kg/m2, p = 0.001), were often burdened with diabetes and hypertension, presented more advanced NYHA class and higher risk of SCD, see Table. In the echocardiographic assessment HOCM presented lower end-systolic left ventricular volume (LV ESV: 27 ± 14 vs 29 ± 13 ml, p = 0.014) although maintained equal stroke volume and even higher ejection fraction (EF: 69 ± 8% vs 67 ± 7%, p < 0.001), cardiac output (CO: 4.3 ± 1.7 vs 4.0 ± 1.4 l/min, p < 0.001) and force in comparison to counterparts without LVOTG. This high-contractility performance was however sustained at the cost of larger left atrium volume index (LAVI: 49 ± 19 vs 40 ± 15 ml/m2, p < 0.001), higher coronary flow velocity (43 ± 12 vs 27 ± 13 cm/s, p < 0.001) as well as more frequent B-lines in the lung assessment. During a median follow-up of 87 months (interquartile range 45 – 143 months), 131 all-cause deaths occurred and not only patients with HOCM but also those with HP showed the worse long-term survival, see Figure. Conclusion HOCM remains the form of HCM burdened with more overt clinical symptoms, signs and prognosis. On the other hand LVOTG seems to be important but not always necessary element of this presentation, which seems to be related even more tightly to general hypercontractility phenotype reflected by higher force and resting coronary flow.Table.Non-HOCM vs HOCM comparison Figure.Force and LVOTG prognostic value

Abstract Aims Our aim was to assess the clinical and prognostic significance of the left ventricular (LV) hypercontractile phenotype (HP) in hypertrophic cardiomyopathy (HCM), which until now remains unclear. Methods and results We enrolled 1533 HCM patients (age 51 ± 15 years, 965 males, 63%) with ejection fraction (EF) ≥ 50%, referred for rest transthoracic echocardiography (TTE) in 27 laboratories from 13 countries. Two-dimensional volumetric TTE assessment included LV outflow tract gradient (LVOTG), LV EF, and LV force (systolic blood pressure + LVOTG/ESV, mmHg/mL). HP was defined as the highest quartile of the force (> 7.32 mmHg/mL). Survival analysis was performed in a subset of 1200 patients with follow-up information. Compared with non-HP patients, HP showed higher heart rate (72 ± 14 vs. 67 ± 14 beats per minute, P < 0.001), lower stroke volume (50 ± 22 vs. 67 ± 22 mL, P < 0.001), larger left atrial volume index (44 ± 16 vs. 40 ± 16 mL/m2, P = 0.011) and higher coronary flow velocity in the mid-distal left anterior descending artery (n = 325, 41 ± 12 vs. 37 ± 14 cm/s, P = 0.021). Force was moderately related to LV EF (r = 0.48, P < 0.001) and weakly to LVOTG (r = 0.36, P < 0.001). During a median follow-up of 87 months (interquartile range 45–143 months), 131 all-cause deaths occurred. At multivariable Cox analysis, a force > 7.32 mmHg (the fourth quartile for analyzed patients) was associated with a hazard ratio of 1.44 (95% Confidence intervals 1.00–2.07) for all-cause death, independently of LVOTG and LV EF. Conclusion HP in HCM is associated with a disadvantageous systemic, cardiac and coronary hemodynamic profile as well as lower survival in the long-term.

Abstract Background The left ventricular (LV) hypercontractile phenotype (HP) plays a critical role in hypertrophic cardiomyopathy (HCM) and is usually identified with the left ventricular outflow tract gradient (LVOTG). Purpose To assess the systemic and coronary hemodynamic profile associated with HP identified with increased LV elastance (also known as force) at rest in patients with HCM. Methods We enrolled 1248 HCM patients (age 50 ± 15 years, 798 males, 64%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 14 quality-controlled sites from 7 countries TTE assessment included LVOTG, EF, and LV force (systolic blood pressure + LVOTG/LV end-systolic volume, mmHg/mL). Volumetric echocardiography with Simpson’s method was used to measure EF from end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), arterial elastance (AE) and ventricular-arterial coupling (VAC). We also assessed resting peak diastolic coronary flow velocity (D-CFV) in the mid-distal left anterior descending artery in a subset of 275 patients. Results EF equaled 68 ± 7%, force = 6.8 ± 5.3 mmHg/ml and LVOTG = 22 ± 28 mmHg. HP was identified as the highest quartile of force (> 7.85 mmHg/ml, mean value= 13.3 ± 7.0). HP showed the lowest SV (46 ± 18 ml) and EDV (61 ± 20 ml), with the highest AE (3.19 ± 1.35 mmHg/ml) and VAC (3.46 ± 1.59) compared to other quartiles (p<0.001) ( see Picture) . D-CFV was not higher in patients with HP (n = 65) compared to those (n = 210) without HP (41± 11 vs 38 ± 14 cm/s, p=ns, but higher in comparison to joint first and second Force quartile (n=122) vs 37 ±14 p =0.0472). Table displays the demografic, clinical and TTE parameters related to HP (Table). In multivariate logistic analysis 4 independent predictors of HP were identified: SBP >130 mmHg with OR 2.5, female sex with OR 5.4, LV EF >70% with OR 6.1 and LVOTG >30 mmHg with the highest OR = 6.3. Conclusion: HCM patients with HP exhibit a distinctive systemic hemodynamic and coronary physiology profile, characterized by low SV, high VAC, and supranormal baseline D-CFV compared to non-HP patients. These findings suggest reduced cardiovascular efficiency and increased myocardial oxygen demand, possibly detrimental over time.

Abstract Background The left ventricular (LV) force, also known as elastance, serves as a load-independent indicator of contractility and can be noninvasively assessed through echocardiography. In hypertrophic cardiomyopathy (HCM), the heightened presence of the active state of myosin heads results in an increased LV force. Purpose To assess the prognostic value of increased LV elastance at rest in patients with HCM. Methods We enrolled 1420 HCM patients (age 50±16 years, 907 males, 64%) with ejection fraction (EF) ≥50%, referred for rest transthoracic echocardiography (TTE) in 10 quality-controlled labs from 7 countries. TTE assessment included peak left ventricular outflow tract gradient (LVOTG), EF, and LV force (systolic blood pressure + LVOTG/LV end-systolic volume assessed with 2-D, mmHg/mL). All patients were followed up. All-cause death was the outcome measure. Results At a median follow-up of 83 months, 150 deaths occurred (Group 1). At study entry, Group 1 patients had the same ESC-Sudden cardiac death score compared to survivors (Group 2). In Group 1 compared to Group 2, TTE showed higher values of MR severity, E/e’ , left atrial volume index, estimated systolic pulmonary artery pressure, and force (see table). At multivariable Cox analysis, only age (HR =1.08, 95% CI=1.03-1.14, p=0.001) and force > median value of 5.3 mmHg/mL (HR = 2.14, 95% CI 1.53-2.99, p=0.020) were independent predictors of mortality. Ten-year survival was 95% in the pooled first (<3.8 mmHg/mL) and second (3.8-5.2 mmHg/mL) quartiles vs 80% in the pooled third (5.3-7.8 mmHg/mL) and fourth quartiles (>7.8 mmHg/mL), see figure. Conclusion HCM patients with higher values of resting LV elastance show a worse survival, highlighting the dark prognostic side of an excess of force in these patients. Table Legends E/e’, early mitral inflow to early mitral annulus motion ratio, EF, left ventricular ejection fraction, LAVI, left atrial volume index; LVOTG, left ventricular outflow tract peak gradient, MR, mitral regurgitation; MWT, maximal wall thickness, NYHA, New York Heart Association classification, RWT, relative wall thickness; SCD risk, risk score for sudden cardiac death in hypertrophic cardiomyopathy, SPAP, systolic pulmonary arterial pressure.Table.Clinical and TTE findingsFigure.Survival in the force quartiles

Abstract Background and Aims Implantable cardioverter-defibrillators (ICDs) are critical for preventing sudden cardiac death (SCD) in arrhythmogenic right ventricular cardiomyopathy (ARVC). This study aims to identify cross-continental differences in utilization of primary prevention ICDs and survival free from sustained ventricular arrhythmia (VA) in ARVC. Methods This was a retrospective analysis of ARVC patients without prior VA enrolled in clinical registries from 11 countries throughout Europe and North America. Patients were classified according to whether they received treatment in North America or Europe and were further stratified by baseline predicted VA risk into low- (<10%/5 years), intermediate- (10%–25%/5 years), and high-risk (>25%/5 years) groups. Differences in ICD implantation and survival free from sustained VA events (including appropriate ICD therapy) were assessed. Results One thousand ninety-eight patients were followed for a median of 5.1 years; 554 (50.5%) received a primary prevention ICD, and 286 (26.0%) experienced a first VA event. After adjusting for baseline risk factors, North Americans were more than three times as likely to receive ICDs {hazard ratio (HR) 3.1 [95% confidence interval (CI) 2.5, 3.8]} but had only mildly increased risk for incident sustained VA [HR 1.4 (95% CI 1.1, 1.8)]. North Americans without ICDs were at higher risk for incident sustained VA [HR 2.1 (95% CI 1.3, 3.4)] than Europeans. Conclusions North American ARVC patients were substantially more likely than Europeans to receive primary prevention ICDs across all arrhythmic risk strata. A lower rate of ICD implantation in Europe was not associated with a higher rate of VA events in those without ICDs.

Introduction: Deep-learning artificial intelligence (AI) algorithms can identify hypertrophic cardiomyopathy (HCM) from the electrocardiogram (ECG). Preliminary data indicate that AI-ECG may also track treatment response in HCM patients (pts) receiving mavacamten (Mava). In this placebo-controlled analysis, we investigated the performance of AI-ECG in HCM detection and its changes during Mava treatment compared to placebo in the phase 3, EXPLORER-HCM trial. Methods: Pts with non-paced ECGs enrolled in EXPLORER-HCM, evaluating Mava over 30 weeks of treatment, were included. All pts had a 12-lead ECG pre-treatment, at each study visit, and 8 weeks after treatment end. Two independently developed AI-ECG convolutional neural network algorithms from the Mayo Clinic and the University of California, San Francisco (UCSF) were applied to all ECGs suitable for analysis. Serial AI-ECG-predicted scores, which correlate with HCM likelihood (range 0-1), were examined between Mava and placebo groups. Results: A total of 101 Mava and 110 placebo pts were included (mean age 58.6, female 40%). At baseline, the mean Mayo and UCSF AI-ECG scores for HCM were 0.82 and 0.65, with 94% and 88% of pts exceeding the respective diagnostic thresholds of 0.11 (Mayo) and 0.4 (UCSF). During 30 weeks of follow-up in the Mava group, the algorithms showed a mean AI-ECG score reduction of 0.32 (Mayo) and 0.17 (UCSF) in all pts between start and end of treatment. In comparison, AI-ECG scores decreased by 0.05 (Mayo) and increased by 0.02 (UCSF) in the placebo group (Mava vs placebo, t-test p-values <0.001 for both algorithms; Figure ) Conclusion: In the EXPLORER-HCM trial population, two independent deep-learning AI-ECG algorithms correctly identified most HCM pts and demonstrated significant reductions in predicted HCM scores after treatment with Mava when compared to placebo. This relative normalization of the ECG suggests disease-modifying properties of Mava, deserving further investigation.

Abstract Background The risk of adverse cardiovascular events in patients with acute myocarditis (AM) and desmosomal gene variants (DGV) remains unknown. Purpose To ascertain the risk of death, ventricular arrhythmias, recurrent myocarditis, and heart failure (main endpoint) in patients with AM and pathogenic or likely pathogenetic DGV. Methods In a retrospective international study from 23 hospitals, 97 patients were included: 36 with AM and DGV (DGV(+)), 25 with AM and negative gene testing (DGV(−)), and 36 AM patients without genetics (w/o genetics). All patients had troponin elevation plus findings consistent with AM on histology or at cardiac magnetic resonance imaging (CMRI). In 86 patients CMRI changes in function and structure were re-assessed at follow-up. Results In the DGV(+) AM group (88.9% DSP variants), median age was 24 years, 91.7% presented with chest pain, and median left ventricular (LV) ejection fraction was 56% on CMRI (p=NS vs. the other 2 groups). Kaplan-Meier curves demonstrated a higher risk of the main endpoint in DGV(+) AM compared to DGV(−) and w/o genetics patients (62.3% vs. 17.5% vs. 5.3% at 5 years respectively; p&lt;0.0001), driven by myocarditis recurrence and ventricular arrhythmias (Figure 1A, B). At follow-up CMRI, a higher number of late-gadolinium enhanced segments was found in DGV(+) AM. Conclusions Patients with AM and evidence of DGV have a higher incidence of adverse cardiovascular events compared with AM patients without DGV. Further prospective studies are needed to ascertain if genetic testing might improve risk stratification of patients with AM who are considered at low risk. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Italian Ministry of Health