Prognostic value of two polymorphisms in non-sarcomeric genes for the development of atrial fibrillation in patients with hypertrophic cardiomyopathy

BACKGROUND

Several non-sarcomeric genes have been postulated to act as modifiers in the phenotypic manifestations of hypertrophic cardiomyopathy (HCM). The development of atrial fibrillation (AF) in HCM has adverse prognostic implications with increased thromboembolism and functional class impairment.

AIM

We tested the hypothesis that 2 non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] are associated with the development of AF.

DESIGN

Prospective study.

METHODS

Two polymorphisms in non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] were analysed in 159 HCM patients (49.3 ± 14.9 years, 70.6% male) and 136 controls. All subjects were clinically stable and in sinus rhythm at entry in the study, without ischemic heart disease or other significant co-morbidities that could mask the effect of the analysed polymorphisms (i.e. previous AF). Thirty-nine patients (24.4%) developed AF during a median follow-up of 49.5 months.

RESULTS

Patients with the -344T>C polymorphism in CYP11B2 gene had a higher risk for AF development [HR: 3.31 (95% CI 1.29-8.50); P = 0.008]. In a multivariate analysis, the presence of the C allele in CYP11B2 gene [HR: 3.02 (1.01-8.99); P = 0.047], previous AF [HR: 2.81 (1.09-7.23); P = 0.033] and a left atrial diameter of ≥42 mm [HR: 2.69 (1.01-7.18); P = 0.048] were independent predictors of AF development. The presence of the polymorphic allele was associated with higher aldosterone serum levels.

CONCLUSION

We have shown for the first time that the CYP11B2 polymorphism is an independent predictor for AF development in HCM patients. This highlights the importance of non-sarcomeric genes in the phenotypic heterogeneity of HCM. The association with higher aldosterone serum levels could relate to greater fibrosis and cardiac remodelling.

Clinical implications of nonsarcomeric gene polymorphisms in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is characterized by cardiomyocyte hypertrophy and fibrosis. Although is an autosomal dominant trait, a group of nonsarcomeric genes have been postulated as modifiers of the phenotypic heterogeneity.

MATERIAL AND METHODS

We prospectively recruited 168 HCM patients and 136 healthy controls from three referral centres. Patients and controls were clinically stable at entry in the study. Nine polymorphisms previously associated with ventricular remodelling were determined: I/D ACE, AGTR1(A1666C), CYP11B2(C344T), PGC1-α(G482S), COLIA1(G2046T), ADRB1(R389G), NOS3(G894T), RETN(-420C>G) and CALM3(-34T>A). Their potential influence on prognosis, assessed by hospital admissions, and their cause were recorded.

RESULTS

The median follow-up time was 49·5 months. Allele and genotype frequencies did not differ between patients and controls. Thirty-six patients (21·5%) required urgent hospitalization (18·5% for heart failure, 22·2% for atrial arrhythmias, 11·1% for ventricular arrhythmias, 29·6% for ischaemic heart disease, 14·8% for stroke and 3·7% for other reasons) with a hospitalization rate of 8·75% per year. Multivariate analysis showed an independent predictive value for noncarriers of polymorphic COL1A1 allele [HR: 2·76(1·26-6·05), P = 0·011] and a trend in homozygous carriers of ADRB1 Arg389 variant [HR: 1·98(0·99-4·02); P = 0·057].

CONCLUSION

Our study suggests that COL1A1 polymorphism (2046G>T) is an independent predictor of prognosis in HCM patients supporting the importance of nonsarcomeric genes on clinical prognosis in HCM.