Shared genetic pathways contribute to risk of hypertrophic and dilated cardiomyopathies with opposite directions of effect

The heart muscle diseases hypertrophic (HCM) and dilated (DCM) cardiomyopathies are leading causes of sudden death and heart failure in young, otherwise healthy, individuals. We conducted genome-wide association studies and multi-trait analyses in HCM (1,733 cases), DCM (5,521 cases) and nine left ventricular (LV) traits (19,260 UK Biobank participants with structurally normal hearts). We identified 16 loci associated with HCM, 13 with DCM and 23 with LV traits. We show strong genetic correlations between LV traits and cardiomyopathies, with opposing effects in HCM and DCM. Two-sample Mendelian randomization supports a causal association linking increased LV contractility with HCM risk. A polygenic risk score explains a significant portion of phenotypic variability in carriers of HCM-causing rare variants. Our findings thus provide evidence that polygenic risk score may account for variability in Mendelian diseases. More broadly, we provide insights into how genetic pathways may lead to distinct disorders through opposing genetic effects.

Sex Differences at the Time of Myectomy in Hypertrophic Cardiomyopathy

BACKGROUND

One of the first clinically detectable alterations in heart function in hypertrophic cardiomyopathy (HCM) is a decline in diastolic function. Diastolic dysfunction is caused by changes in intrinsic properties of cardiomyocytes or an increase in fibrosis. We investigated whether clinical and cellular parameters of diastolic function are different between male and female patients with HCM at the time of myectomy.

METHODS AND RESULTS

Cardiac tissue from the interventricular septum of patients with HCM (27 women and 44 men) was obtained during myectomy preceded by echocardiography. At myectomy, female patients were 7 years older than male patients and showed more advanced diastolic dysfunction than men evident from significantly higher values for E/e' ratio, left ventricular filling pattern, tricuspid regurgitation velocity, and left atrial diameter indexed for body surface. Whereas most male patients (56%) showed mild (grade I) diastolic dysfunction, 50% of female patients showed grade III diastolic dysfunction. Passive tension in HCM cardiomyocytes was comparable with controls, and myofilament calcium sensitivity was higher in HCM compared with controls, but no sex differences were observed in myofilament function. In female patients with HCM, titin was more compliant, and more fibrosis was present compared with men. Differences between female and male patients with HCM remained significant after correction for age.

CONCLUSIONS

Female patients with HCM are older at the time of myectomy and show greater impairment of diastolic function. Furthermore, left ventricular and left atrial remodeling is increased in women when corrected for body surface area. At a cellular level, HCM women showed increased compliant titin and a larger degree of interstitial fibrosis.

Effect of Gender and Genetic Mutations on Outcomes in Patients With Hypertrophic Cardiomyopathy

Gender has been proposed to impact the phenotype and prognosis of hypertrophic cardiomyopathy (HC). Our aims were to study gender differences in the clinical presentation, phenotype, genotype, and outcome of HC. This retrospective single-center cohort study included 1,007 patients with HC (62% male, 80% genotyped) evaluated between 1977 and 2017. Hazard ratios (HR) were calculated using multivariable Cox proportional hazard regression models. At first evaluation, female patients presented more often with symptoms (43% vs 35%, p = 0.01), were older than male patients (56 ± 16 vs 49 ± 15 years, p <0.001), and more frequently had hypertension (38% vs 27%, p <0.001), left ventricular outflow tract obstruction (37% vs 27%, p <0.001), and impaired left ventricular systolic (17% vs 11%, p = 0.01) and diastolic (77% vs 62%, p <0.001) function. Overall, the genetic yield was similar between genders (54% vs 51%, p = 0.4); however, in patients ≥70 years, the genetic yield was less in women (15% vs 36%, p = 0.03). During 6.8-year follow-up (interquartile range 3.2 to 10.9), female gender was not independently associated with all-cause mortality (HR 1.25 [0.91 to 1.73]), cardiovascular mortality (HR 1.22 [0.83 to 1.79]), heart failure-related mortality (HR 1.77 [0.95 to 3.27]), or sudden cardiac death (SCD) and/or aborted SCD (HR 0.75 [0.44 to 1.30]). Interventions and nonfatal clinical events did not differ between the genders. In conclusion, female patients with HC present at a more advanced age with a different clinical, phenotypic, and genetic status. There is no independent association between female gender and all-cause mortality, cardiovascular mortality, heart failure-related mortality, or SCD.

Outcomes of Contemporary Family Screening in Hypertrophic Cardiomyopathy

Background:

Contemporary hypertrophic cardiomyopathy (HCM) family screening includes clinical evaluation and genetic testing (GT). This screening strategy requires the identification of a pathogenic mutation in the proband. Our aim was to examine the results of this HCM screening strategy.

Methods:

Between 1985 and 2016, 777 relatives of 209 probands were assessed in the context of HCM screening. Genotype-positive (G+) relatives and relatives without genetic testing (GT) underwent repeated clinical evaluations. In genotype-negative (G-) relatives mortality was assessed during follow-up.

Results:

A pathogenic mutation was identified in 72% of probands. After counseling, GT was performed in 620 (80%) relatives: 264 (43%) were G+ (age 41±18 y) and 356 (57%) were G- (age 48±17 y). At first screening, HCM was diagnosed in 98 (37%) G+ relatives and 28 (17%) relatives without GT ( p <0.001). During 9 years follow-up of relatives diagnosed with HCM, 8 (6%) underwent septal reduction therapy, 16 (16%) received primary prevention ICDs, and cardiac mortality was 0.3%/year. During 7 years follow-up of relatives without HCM, 29 (16%) developed HCM. Survival at 5/10 years was 99%/95% in G+ relatives, 97%/94% in G- relatives ( p =0.8), and 100%/100% in relatives without GT.

Conclusions:

HCM was identified in 30% of relatives at first screening, and 16% developed HCM during 7 years of repeated evaluation. GT led to a discharge from clinical follow-up in 46% of the study population. Survival in the relatives was good.

Three-dimensional echocardiography for the assessment of left ventricular geometry and papillary muscle morphology in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HC) is characterized by left ventricular (LV) hypertrophy and associated with papillary muscle (PM) abnormalities. The aim of this study was to evaluate the utility of three-dimensional echocardiography (3DE) for the geometric assessment of LV hypertrophy and PM morphology.

METHODS

The study included 24 patients with an established diagnosis of HC and 31 healthy controls. 3DE was performed using an iE33 or EPIQ 7C ultrasound system with an X5-1 transducer. QLAB software was used for the 3D analysis of LV wall thickness (LVWT) and PM morphology and hypertrophy; the number and cross-sectional area (CSA) of anterolateral and posteromedial PMs; and the presence of bifid or accessory PMs.

RESULTS

Patients with HC had a larger LVWT compared to controls in all segments (p < 0.001), and LVWT was largest in the midventricular septal segment (2.12 ± 0.68 cm). The maximum LVWT followed a spiral pattern from the LV base to the apex. The CSA of both anterolateral and posteromedial PMs was larger in patients with HC than in controls (1.92 vs. 1.15 cm2; p = 0.001 and 1.46 vs. 1.08 cm2; p = 0.033, respectively). The CSA of the posteromedial PM was larger in patients with LVOT obstruction than in those without (2.64 vs 1.16 cm2, p = 0.021).

CONCLUSIONS

3DE allows the assessment of LV geometry and PM abnormalities in patients with HC. 3DE demonstrated that the maximum hypertrophy was variable and generally located in a spiral from the LV base to the apex.

Clinical Characteristics and Long-Term Outcome of Hypertrophic Cardiomyopathy in Individuals With a MYBPC3 (Myosin-Binding Protein C) Founder Mutation

BACKGROUND

MYBPC3 (Myosin-binding protein C) founder mutations account for 35% of hypertrophic cardiomyopathy (HCM) cases in the Netherlands. We compared clinical characteristics and outcome of MYBPC3 founder mutation (FG+) HCM with nonfounder genotype-positive (G+) and genotype-negative (G-) HCM.

METHODS AND RESULTS

The study included 680 subjects: 271 FG+ carriers, 132 G+ probands with HCM, and 277 G- probands with HCM. FG+ carriers included 134 FG+ probands with HCM, 54 FG+ relatives diagnosed with HCM after family screening, 74 FG+/phenotype-negative relatives, and 9 with noncompaction or dilated cardiomyopathy. The clinical phenotype of FG+ and G+ probands with HCM was similar. FG+ and G+ probands were younger with less left ventricular outflow tract obstruction than G- probands, however, had more hypertrophy, and nonsustained ventricular tachycardia. FG+ relatives with HCM had less hypertrophy, smaller left atria, and less systolic and diastolic dysfunction than FG+ probands with HCM. After 8±6 years, cardiovascular mortality in FG+ probands with HCM was similar to G+ HCM (22% versus 14%; log-rank P=0.14), but higher than G- HCM (22% versus 6%; log-rank P<0.001) and FG+ relatives with HCM (22% versus 4%; P=0.009). Cardiac events were absent in FG+/phenotype-negative relatives; subtle HCM developed in 11% during 6 years of follow-up.

CONCLUSIONS

Clinical phenotype and outcome of FG+ HCM was similar to G+ HCM but worse than G- HCM and FG+ HCM diagnosed in the context of family screening. These findings indicate the need for more intensive follow-up of FG+ and G+ HCM versus G- HCM and FG+ HCM in relatives.

Incidence of Device-Detected Atrial Fibrillation and Long-Term Outcomes in Patients With Hypertrophic Cardiomyopathy

Atrial fibrillation (AF) is a common complication of hypertrophic cardiomyopathy (HC) and associated with adverse clinical outcomes, such as thromboembolisms. Cardiac implantable electronic devices (CIEDs) enable early detection of AF. The aim of this study was to assess the incidence of device-detected AF and the impact on long-term outcomes in patients with HC. The cohort consisted of 132 patients (63% men, mean age 52 ± 16 years) with a diagnosis of HC and a CIED. Follow-up started at the date of CIED implantation to assess the incidence of device-detected AF. Patients with persistent AF at the time of implantation were excluded from the analysis of the incidence of AF. End points were all-cause and cardiac mortality, device-detected AF, and thromboembolism (stroke, transient ischemic attack, or peripheral arterial embolism). In total, 114 patients were in sinus rhythm at time of CIED implantation. During the median 2.8 (interquartile range 1.2 to 5.4) years of follow-up, device-detected AF occurred in 29 patients (25%), resulting in an annual incidence of 7.0%/year. Device-detected AF led to a change in the clinical management in 22 patients (76%). Anticoagulation therapy was started in 13 (45%), antiarrhythmic medication in 9 (31%), and electrical cardioversion in 8 (28%) patients. Six patients (5%) suffered a thromboembolic complication. All-cause mortality was 27 (20%), and cardiac mortality was 21 (16%). A history of AF at time of implantation was an independent predictor of cardiac death (hazard ratio 4.7, p = 0.003). In conclusion, the incidence of device-detected AF in patients with HC was 7.0%/year, leading to a change in clinical management in the majority (76%) of cases to reduce the risk of thromboembolic complications. These findings stress the importance of AF detection in HC and advocate vigilant interrogation of the device.

Value of Genetic Testing for the Prediction of Long-Term Outcome in Patients With Hypertrophic Cardiomyopathy

Pathogenic gene mutations are found in about 50% of patients with hypertrophic cardiomyopathy (HC). Previous studies have shown an association between sarcomere mutations and medium-term outcome. The association with long-term outcome has not been described. The aim of this cohort study was to assess the long-term outcomes of patients with genotype positive (G+) and genotype negative (G-) HC. The study population consisted of 626 patients with HC (512 probands and 114 relatives) who underwent phenotyping and genetic testing from 1985 to 2014. End points were all-cause mortality, cardiovascular (CV) mortality, heart failure (HF)-related mortality, and sudden cardiac death/aborted sudden cardiac death (SCD/aborted SCD). Kaplan-Meier and multivariate Cox regression analyses were performed. A pathogenic mutation was detected in 327 patients (52%). G+ probands were younger than G- probands (46 ± 15 vs 55 ± 15 years, p <0.001), had more non sustained ventricular tachycardia (34% vs 13%; p <0.001), more often a history of syncope (14% vs 7%; p = 0.016), and more extreme hypertrophy (maximal wall thickness ≥30 mm, 7% vs 1%; p <0.001). G- probands were more symptomatic (New York Heart Association ≥II, 73% vs 53%, p <0.001) and had higher left ventricular outflow tract gradients (42 ± 39 vs 29 ± 33 mm Hg, p = 0.001). During 12 ± 9 years of follow-up, G+ status was an independent risk factor for all-cause mortality (hazard ratio [HR] 1.90, 95% CI 1.14 to 3.15; p = 0.014), CV mortality (HR 2.82, 95% CI 1.49 to 5.36; p = 0.002), HF-related mortality (HR 6.33, 95% CI 1.79 to 22.41; p = 0.004), and SCD/aborted SCD (HR 2.88, 95% CI 1.23 to 6.71; p = 0.015). In conclusion, during long-term follow-up, patients with G+ HC are at increased risk of all-cause death, CV death, HF-related death, and SCD/aborted SCD.