The impact of adrenoceptor-1 gene polymorphism on structural and functional features in patients with hypertrophic cardiomyopathy
Authors: Raimoglou D , Karpuz M H , Enar R , Karadag B , Ikitimur B , Raimoglu U , Soysal A U , Mutlu D , Incesu G , Gulfidan A , Atici A , Durmaz E 
Published: October 2022

Abstract

Background
The adrenergic system plays a central role during the clinical course of hypertrophic cardiomyopathy (HCM) and hence beta-blocker therapy is the first-line treatment option according to current guidelines. Previous studies demonstrated variable cellular response to an adrenergic stimulus due to adrenoceptor-1 (ADRB-1) gene polymorphism in several patient groups including hypertension and dilated cardiomyopathy. Moreover, the impact of beta-blockers is also variable in these patients.

Purpose
We aimed to investigate the impact of ADRB-1 gene polymorphism on structural and functional features among patients with HCM.

Methods
In this study, we investigated the roles of Arginin389Glycine and Glycine49Serine polymorphism. Patients with a clear diagnosis of HCM according to current guidelines were included. Structural features including maximal wall thickness, interstitial fibrosis and left ventricular/atrial volumes were obtained using cardiac MRI and transthoracic echocardiography. Functional features including heart rate, blood pressure, left ventricular outflow obstruction were also recorded. The risk of sudden cardiac death was calculated using the HCM risk score. The impact of beta-blocker therapy on heart rate and blood pressure were also compared.

Results
After the exclusion of patients, 147 patients were included in the study. 77% of the study population were male and the mean age was 49.5 years. The hypertrophic segment was septum in 83% of the study population. The mean maximum wall thickness was 20 mm (19–23). With respect to Ser49Gly polymorphism, Serine homozygotes demonstrated higher late-gadolinium enhancement and indicator of interstitial fibrosis (p: 0.007). In concordance with higher LGE, the presence of fragmented QRS on surface ECG (p: 0.026) and a higher prevalence of non-sustained ventricular tachycardia (p: 0.016) in these patients were observed. The risk of sudden cardiac death was also higher in Ser49 homozygotes (p: 0.041). However, with respect to Arg389Gly gene polymorphism, there was no significant difference between Arg389 homozygotes, Arg389Gly heterozygotes and Gly389 homozygotes in terms of structural and functional features. The vast majority of patients reported improved functional capacity and decreased shortness of breath during the follow-up regardless of ADRB-1 gene polymorphism which is objectively validated by decreased pro-BNP levels in all patients.

Conclusion
Our results indicated that ADRB-1 gene polymorphism, particularly Ser49Gly gene polymorphism may have a significant role during the clinical course of HCM. Since Ser49 homozygote patients demonstrated higher interstitial fibrosis and a higher risk of sudden cardiac death, further studies are required to determine the significance of Ser49Gly gene polymorphism in HCM patients.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): Bilimsel Arastırma Projesi (BAP) - Istanbul University - Cerrahpasa, Cerrahpasa Medical School