Gender and Age at Enrolment: the Predictor of Advanced Heart failure in Gene-negative Patients with Hypertrophic Cardiomyopathy

BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) may develop concomitant advanced heart failure (HF). However, there is a paucity of data on the clinical outcomes of HCM patients without mutations who have advanced HF. Methods: A total of 1529 unrelated patients with HCM were enrolled and followed up. All patients were genotyped by whole exome or panel sequencing. Patients without mutations were studied to assess the impact of family history, clinical findings and echocardiographic parameters on advanced HF. Results: A total of 735unrelated patients with HCM were included in the study. The mean follow up duration was 3.2 ± 2.3years. During follow-up,97 patients had advanced HF. Multivariable analysis revealed that risk factors significantly associated with advanced HF were gender [adjusted hazard ratio (HR)2.499, 95% confidence interval (CI) 1.531-4.081, P<0.001]and age at enrolment (adjusted HR 1.298,95% CI 1.00-1.682, P= 0.049) during the follow-up period. Conclusion: Female and older at enrolment can increase risk of advanced HF in gene-negative patients with HCM. Early detection and treatment have an important role to play in management and prevention of disease-related complications for gene-negative patients.

Hypertrophic cardiomyopathy (HCM) is a complex type of genetic heart disease that is defined by left ventricular hypertrophy unexplained by secondary causes [1].Over the past 20 years, a lot of evidence has supported the prevalence of HCM at about 1/500 USA [2], as well as in China [3].However, recent studies have shown that HCM is more common than previously estimated, with an estimated prevalence ranging from 1 in 500 to 1 in 200 [4].
The demographics and epidemiology of HCM have changed, and there is increasing recognition of the dysfunction caused by exertion dyspnea, which has traditionally been considered a form of heart failure (HF) [5,6].With the decrease in sudden cardiac death (SCD) caused by the use of implantable defibrillators in HCM, HF has become an increasingly prominent management problem. Exercising dyspnea with disease levels ranging from mild to severe (New York Heart Association Function Class III to IV) is often difficult to treat, leading to progressive disability. So, the early and accurate identification of risk factors for advanced HF have aroused widespread concern.
Studies have shown that many gene mutations cause HCM. So the current research mainly focuses on the effect of gene mutation on HF, including genetic status [7]and mutation dosage [8].At the same time, many studies have suggested that HCM patients with genetic mutations have worse symptoms and more severe adverse outcomes than those with negative mutations [9].Unfortunately, patients with negative mutations are ignored. Moreover, studies have found that the risk of poor prognosis remains in patients with negative genetic mutations [8].Therefore, it is urgent to study the prognostic factors of HCM patients without mutations and the influence of these risk factors.
In this study, we sought to analyze the correlation between the prognostic factors and the clinical phenotype in gene-negative patients with HCM, and evaluate the value of the factors in predicting the advanced HF, so as to provide a reference for the prognosis assessment of such patients.

FOLLOW UP and OUTCOMES MEASUREMENT
The patients were prospectively recruited and followed up by clinical visits or telephone consultation. The clinical outcomes measured in this study were advanced HF. We defined New York Heart Association class III or IV (NYHA III/IV) HF as advanced HF.

STATISTICAL ANALYSIS
Continuous variables, reported as means with mean ± standard deviation (SD), were compared between groups with t-test or nonparametric tests, as appropriate. Multiple groups were compared using one-way ANOVA. Categorical variables, reported as number (%), were compared between groups with x2 or Fisher exact tests. Survival was modelled using Kaplan-Meier analysis and log-rank test. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated with univariable or multivariable Cox proportional hazard regression models. All probability values were 2-sided, and P<0.05 was considered significant. SPSS (V.23.0.0.0) was used for the analyses.

Characteristics of Patients
A total of 735(48.1%) unrelated patients with HCM were included in this study following the inclusion and exclusion criteria. The mean age at enrolment the studied patients was 52.54± 1 3.24 years and 69.5% was male. The demographic and clinical characteristics of the studied patients were summarized in Table 1.

Clinical Outcomes
During the mean follow-up period of 3.18±2.28years, there were 95 advanced HF. The univariate analysis showed that gender, age at enrolment, BSA and AF were related to advanced HF events. The multivariate Cox regression analysis and Kaplan-Meier analysis revealed that female was associated with a significantly higher risk of advanced HF than male (adjusted HR 2.499,95% CI 1.531-4.081, P<0.001Table 2, Figure 1). The analysis also showed that older at enrolment (adjusted HR 1.298,95% CI 1.000-1.682, P=0.049, Table 2 Figure 1).

DISCUSSION
The presence of different phenotypes in any of the pathogenic mutations suggests that other factors besides genetic mutations may influence the development of HCM. And the 2014 guidelines of the European Society of Cardiology suggested that the cause of HCM in 25-30% of patients remains unknown [11].In our study, we enrolled sarcomere gene mutation-negative HCM patients, and found that female and older at enrolment are associated with increased risk of advanced HF in HCM patients without mutations during the follow-up period.
HCM patients may have a high prevalence of HF. One of the studies, in a cohort of 1000 patients diagnosed with HCM, showed a HF incidence of nearly 50%, with symptoms ranging from mild to severe [12]. Another study, with a larger cohort of 3208 patients, showed that the prevalence of HF was 67% [13]. Thus, early and accurate identification of risk factors for advanced HF is of great value for the treatment and management of patients with HCM. Some biomarkers have been related to the disease severity of HCM, However, due to lack of sensitivity and specificity, they cannot be a reliable clinical tool to guide treatment. For example, Brain natriuretic peptide (or N-terminal pro-brain natriuretic peptide) may be useful for nonobstructive HCM patients, but it is not a liable prognostic predictor for individuals with HCM [14]. In the past 15 years, genetic testing has played an important role in guiding the clinical management of patients with HCM. Genetic testing maybe offer excellent opportunities to identify individuals with mutations who will develop HCM before typical clinical manifestations arise.
However, there is insufficient evidence that sarcomere gene mutations can predict the development of HF in patients with HCM, although mutation-positive patients are associated with a worse cardiovascular prognosis than mutation-negative patients [15].
During the past 20 years, a large number of studies have been conducted on HCM patients of different groups and races to determine whether the prognosis of women is worse than that of men. [16][17][18][19][20][21]. Studies have found that patients with gene mutations have a worse prognosis than mutation-negative patients [8].After excluding the influence of genetic mutations on patients, we conducted research and found that women still can increase the risk of advanced HF during follow-up. This is consistent with previous studies [22] .This indicates that gender is an important determinant in HCM treatment, and women may need more aggressive diagnosis and treatment methods.
A major risk factor for HF and overall cardiovascular disease is age. About 1% of people over the age of 50 suffer from HF, which doubles every 10 years, making HF the leading cause of death for the elderly. [23].In the present study, HCM patients with sarcomere gene mutations are younger at enrolment [8]. It can be seen that gene mutations have an impact on the age at enrolment of patients with HCM. Thus, in the case of excluding this factor of gene mutation, our study found that older at enrolment was significantly increased the risk of advanced HF during follow-up. We warn that negative-mutation patients with HCM should still pay attention to the disease, and seek medical treatment in time after diagnosis and review them regularly to minimize the possibility of adverse events.

CONCLUSION
Our study demonstrates that gender and age at enrolment are predictor of advanced HF events in gene-negative patients with HCM. This study may have implications for the management of HCM patients without gene mutations.    In follow-up time, survival curves for advanced HF events of genders(A), age at enrolment(B). The log rank test was used to calculate the P value