Genetic polymorphisms in the renin-angiotensin-aldosterone system associated with expression of left ventricular hypertrophy in hypertrophic cardiomyopathy: a study of five polymorphic genes in a family with a disease causing mutation in the myosin binding protein C gene

MYH7 in cardiomyopathy and skeletal muscle myopathy

Myosin heavy chain gene 7 (MYH7), a sarcomeric gene encoding the myosin heavy chain (myosin-7), has attracted considerable interest as a result of its fundamental functions in cardiac and skeletal muscle contraction and numerous nucleotide variations of MYH7 are closely related to cardiomyopathy and skeletal muscle myopathy. These disorders display significantly inter- and intra-familial variability, sometimes developing complex phenotypes, including both cardiomyopathy and skeletal myopathy. Here, we review the current understanding on MYH7 with the aim to better clarify how mutations in MYH7 affect the structure and physiologic function of sarcomere, thus resulting in cardiomyopathy and skeletal muscle myopathy. Importantly, the latest advances on diagnosis, research models in vivo and in vitro and therapy for precise clinical application have made great progress and have epoch-making significance. All the great advance is discussed here.

Impact of the gene polymorphisms in the renin-angiotensin system on cardiomyopathy risk: A meta-analysis

Due to the inconsistent findings from various studies, the role of gene polymorphisms in the renin-angiotensin system in influencing the development of cardiomyopathy remains unclear. In this study, we conducted a systematic review and meta-analysis to summarize the findings regarding the impact of angiotensin converting enzyme (ACE) I/D, angiotensinogen (AGT) M235T, and angiotensin II Type 1 receptor (AGTR1) A1166C gene polymorphisms in patients with cardiomyopathy. We performed a comprehensive search of several electronic databases, including PubMed, Embase, the Cochrane Library, and Web of Science, covering articles published from the time of database creation to April 17, 2023. Studies on the assessment of genetic polymorphisms in genes related to the renin-angiotensin system in relation to cardiomyopathy were included. The primary outcome was cardiomyopathy. Risk of bias was assessed using the Newcastle-Ottawa Scale scale. The meta-analysis includes 19 studies with 4,052 cases and 5,592 controls. The ACE I/D polymorphisms were found to be associated with cardiomyopathy (allelic model D vs I: OR = 1.29, 95CI% = 1.08-1.52; dominant model DD+ID vs II: OR = 1.43, 95CI% = 1.01-2.02; recessive model DD vs ID+II: OR = 0.79, 95CI% = 0.64-0.98). AGT M235T polymorphism and cardiomyopathy were not significantly correlated (allelic model T vs M: OR = 1.26, 95CI% = 0.96-1.66; dominant model TT+MT vs MM: OR = 1.30, 95CI% = 0.98-1.73; recessive model TT vs MT+MM: OR = 0.63, 95CI% = 0.37-1.07). AGTR1 polymorphism and cardiomyopathy were not significantly associated under allelic model A vs C (OR = 0.69, 95CI% = 0.46-1.03) and recessive model AA vs CA+CC (OR = 0.89, 95CI% = 0.34-2.30), but under the dominant model AA+CA vs CC (OR = 0.51, 95CI% = 0.38-0.68). The current meta-analysis reveals that polymorphisms in ACE I/D may be a genetic risk factor for cardiomyopathy. There is an association between AGTR1 gene polymorphisms and risk of cardiomyopathy under the specific model.

Effects of Angiotensin II Receptor Blockers on Ventricular Hypertrophy in Hypertrophic Cardiomyopathy: A Meta-Analysis of Randomized Controlled Trials

PURPOSE

Animal studies have suggested that angiotensin II receptor blockers (ARBs) can attenuate or reverse the progression of hypertrophic cardiomyopathy, while clinical studies yielded conflicting results. We sought to conduct a meta-analysis to investigate the effect of ARBs in patients with hypertrophic cardiomyopathy.

METHODS

PubMed and EMBASE databases were searched through June 2020. Only randomized controlled trials (RCTs) were included, and each study's quality was assessed using the Jadad scale. The primary outcome was left ventricular mass reduction, and the secondary outcome was the change in left ventricular ejection fraction (LVEF). Data were pooled using the random effects model.

RESULTS

A total of 1294 articles were screened. Five RCTs were included in the final analysis, enrolling 209 patients with hypertrophic cardiomyopathy (101 patients were in the ARB arm). ARB treatment was not associated with either significant left ventricular mass reduction (standardized mean difference: - 0.25; 95% CI: - 0.73, 0.22; p = 0.29) or change in LVEF (weighted mean difference: 0.73%; 95% CI: - 1.10%, 2.56%; p = 0.43). Subgroup analysis showed that losartan, one of the most investigated and commonly used ARBs, was also not associated with significant decreases of left ventricular mass (standardized mean difference: - 0.13; 95% CI: - 0.61, 0.36; p = 0.61).

CONCLUSION

This meta-analysis showed that ARB treatment is not associated with reduced left ventricular mass nor remarkable LVEF change among patients with hypertrophic cardiomyopathy. Further studies with a larger number of patients will be required to confirm these findings.

[Hypertrophic cardiomyopathy in elderly: causes, diagnostic and treatment approaches]

Hypertrophic cardiomyopathy is the most common inherited heart disorder with high clinical heterogeneity. Every fifth patient is older than 60 years at first diagnosis. This review discusses the possible causes for the late onset of hypertrophic cardiomyopathy, the diagnostic and treatment approaches in the elderly.

Exome sequencing identifies a FHOD3 p.S527del mutation in a Chinese family with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disease and is characterised by unexplained ventricular myocardial hypertrophy. HCM is highly heterogeneous and is primarily caused by the mutation of genes encoding sarcomere proteins. As a result of its genetic basis, we investigated the underlying cause of HCM in a Chinese family by whole-exome sequencing.

METHODS

Whole-exome sequencing was performed for seven clinically diagnosed HCM family members and the resulting single nucleotide variants associated with cardiac hypertrophy or heart development were analysed by a polymerase chain reaction and Sanger sequencing.

RESULTS

A non-frameshift deletion mutation (p.S527del) of Formin Homology 2 Domain Containing 3 (FHOD3) was detected in all of the affected family members and was absent in all unaffected members, with the exception of one young member. Moreover, three single nucleotide variants associated with heart development and morphogenesis were identified in the proband but were absent in the other affected subjects.

CONCLUSIONS

This is the first HCM family case of FHOD3 (p.S527del) variation in Asia. Additionally, RNF207 (p.Q268P), CCM2 (p. E233K) and SGCZ (p.Q134X) may be related to the clinical heterogeneity of the family. The present study could enable the provision of genetic counseling for this family and provide a basis for future genetic and functional studies.

The Gene Polymorphism of Angiotensin-Converting Enzyme Intron Deletion and Angiotensin-Converting Enzyme G2350A in Patients With Left Ventricular Hypertrophy: A Meta-analysis

Objectives

The aim of the study was to evaluate the correlation between left ventricular hypertrophy and the gene polymorphism of angiotensin-converting enzyme (ACE) intron deletion (I/D) and ACE G2350A.

Methods

Information related to the sample size and genotype frequencies was extracted from each study.

Results

Our results found that the D allele (p = 0.0180) and DD genotype (p = 0.0110) of ACE I/D had a significant association with increasing the risk of left ventricular hypertrophy, whereas the I allele (p = 0.0180), but not II (p = 0.1660) and ID genotypes (p = 0.1430), was associated with decreasing the risk of left ventricular hypertrophy. On other hand, we found that the A allele (p = 0.0020) and GA genotype of ACE G2350A (p = 0.0070) had the correlation with increasing the risk of left ventricular hypertrophy.

Conclusions

Our meta-analysis reveals that the D allele of ACE I/D and the A allele of ACE G2350A are associated with increasing the risk of left ventricular hypertrophy.

Coronary arterial vasculature in the pathophysiology of hypertrophic cardiomyopathy

Alterations in the coronary vascular system are likely associated with a mismatch between energy demand and energy supply and critical in triggering the cascade of events that leads to symptomatic hypertrophic cardiomyopathy. Targeting the early events, particularly vascular remodeling, may be a key approach to developing effective treatments. Improvement in our understanding of hypertrophic cardiomyopathy began with the results of early biophysical studies, proceeded to genetic analyses pinpointing the mutational origin, and now pertains to imaging of the metabolic and flow-related consequences of such mutations. Microvascular dysfunction has been an ongoing hot topic in the imaging of genetic cardiomyopathies marked by its histologically significant remodeling and has proven to be a powerful asset in determining prognosis for these patients as well as enlightening scientists on a potential pathophysiological cascade that may begin early during the developmental process. Here, we discuss questions that continue to remain on the mechanistic processes leading to microvascular dysfunction, its correlation to the morphological changes in the vessels, and its contribution to disease progression.

The genetics of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is most commonly transmitted as an autosomal dominant trait, caused by mutations in genes encoding cardiac sarcomere proteins^1–3. Other inheritable causes of the disease include mutations in genes coding for proteins important in calcium handling or that form part of the cytoskeleton^4–6. At present, the primary clinical role of genetic testing in HCM is to facilitate familial screening to allow the identification of individuals at risk of developing the disease^7,8. It is also used to diagnose genocopies, such as lysosomal^9–11 and glycogen storage disease which have different treatment strategies, rates of disease progression and prognosis^12–14. The role of genetic testing in predicting prognosis is limited at present, but emerging data suggest that knowledge of the genetic basis of disease will assume an important role in disease stratification^15–17 and offer potential targets for disease-modifying therapy in the near future¹⁸.

Next-generation sequencing identifies pathogenic and modifier mutations in a consanguineous Chinese family with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a highly heterogeneous disease displaying considerable interfamilial and intrafamilial phenotypic variation, including disease severity, age of onset, and disease progression. This poorly understood variance raises the possibility of genetic modifier effects, particularly in MYBPC3-associated HCM.In a large consanguineous Chinese HCM family, we identified 8 members harboring the MYBPC3 c.3624delC (p.Lys1209Serfs) disease-causing mutation, but with very disparate phenotypes. Genotyping ruled out the modifying effect of previously described variants in renin-angiotensin-aldosterone system. Afterwards, we screened for modifying variants in all known causing genes and closely related genes for cardiomyopathy and channelopathy by performing targeted next-generation sequencing. For first time, we showed that a c.1598C>T (p.Ser533Leu) mutation in voltage-dependent l-type calcium channel subunit beta-2 (CACNB2) was present in all severely affected HCM patients, but not in those moderately affected or genotype-positive phenotype-negative patients. This CACNB2 p.Ser533Leu mutation is extremely conserved in evolution, and was not found in 550 healthy controls.Our results suggest that CACNB2 is a possible candidate genetic modifier of MYBPC3-associated familial HCM, but more genetic evidence and functional experiments are needed to confirm.

Lack of Phenotypic Differences by Cardiovascular Magnetic Resonance Imaging in MYH7 (β-Myosin Heavy Chain)- Versus MYBPC3 (Myosin-Binding Protein C)-Related Hypertrophic Cardiomyopathy

BACKGROUND

The 2 most commonly affected genes in hypertrophic cardiomyopathy (HCM) are MYH7 (β-myosin heavy chain) and MYBPC3 (β-myosin-binding protein C). Phenotypic differences between patients with mutations in these 2 genes have been inconsistent. Scarce data exist on the genotype-phenotype association as assessed by tomographic imaging using cardiac magnetic resonance imaging.

METHODS AND RESULTS

Cardiac magnetic resonance imaging was performed on 358 consecutive genotyped hypertrophic cardiomyopathy probands at 5 tertiary hypertrophic cardiomyopathy centers. Genetic testing revealed a pathogenic mutation in 159 patients (44.4%). The most common genes identified were MYH7 (n=53) and MYBPC3 (n=75); 33.1% and 47% of genopositive patients, respectively. Phenotypic characteristics by cardiac magnetic resonance imaging of these 2 groups were similar, including left ventricular volumes, mass, maximal wall thickness, morphology, left atrial volume, and mitral valve leaflet lengths (all P=non-significant). The presence of late gadolinium enhancement (65% versus 64%; P=0.99) and the proportion of total left ventricular mass (%late gadolinium enhancement; 10.4±13.2% versus 8.5±8.5%; P=0.44) were also similar.

CONCLUSIONS

This multicenter multinational study shows lack of phenotypic differences between MYH7- and MYBPC3-associated hypertrophic cardiomyopathy when assessed by cardiac magnetic resonance imaging. Postmutational mechanisms appear more relevant to thick-filament disease expression and outcome than the disease-causing variant per se.

The influence of clinical and genetic factors on left ventricular wall thickness in Ragdoll cats

OBJECTIVES

To investigate the effect of various genetic and environmental modifiers on left ventricular (LV) wall thickness in a cohort of cats genotyped for the myosin binding protein C3 mutation (MYBPC3).

ANIMALS

Sixty-four Ragdoll cats.

METHODS

All cats were screened for HCM with echocardiography and genotyping for the HCM-associated MYBPC3:R820W mutation. Cats were also genotyped for previously identified variant polymorphisms of the angiotensin-converting enzyme (ACE) and cardiac beta-adrenergic receptor (ADRB1) genes. Plasma N-terminal pro-B-type natriuretic peptide and cardiac troponin I were also measured. Associations were evaluated between genotype (MYBPC3 negative/positive, and ACE and ADRB1 negative/heterozygous/homozygous), patient factors (body weight, age and sex) and echocardiographic measurements of LV wall thickness.

RESULTS

Male cats had greater maximum wall thickness (LVmax; 5.8 mm, IQR 5.1-6.4 mm) than females (4.7 mm, IQR 4.4-5.3 mm, p = 0.002). Body weight positively correlated with LVmax (ρ = 0.604, p < 0.001). The MYBPC3:R820W-positive cats had a greater LVmax (5.44 mm, IQR 4.83-6.28 mm) than the negative cats (4.76 mm, IQR 4.36-5.32 mm, p = 0.001). Also, the ACE polymorphism genotype was associated with LVmax: the homozygous cats (5.37 mm, IQR 5.14-6.4 mm) had greater LVmax than the heterozygous cats (4.73 mm, IQR 4.41-5.55 mm, p = 0.014). Only the MYBPC3 genotype and body weight were independently associated with wall thickness in multivariable analysis.

CONCLUSIONS

This study provides evidence that the MYBPC3:R820W mutation is independently associated with LV wall thickness in Ragdoll cats. Body weight is also independently associated with maximum LV wall thickness, but is not currently accounted for in HCM screening. In addition, other genetic modifiers may be associated with variation in LV wall thickness in Ragdolls.

Update on hypertrophic cardiomyopathy and a guide to the guidelines

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder, affecting 1 in 500 individuals worldwide. Existing epidemiological studies might have underestimated the prevalence of HCM, however, owing to limited inclusion of individuals with early, incomplete phenotypic expression. Clinical manifestations of HCM include diastolic dysfunction, left ventricular outflow tract obstruction, ischaemia, atrial fibrillation, abnormal vascular responses and, in 5% of patients, progression to a 'burnt-out' phase characterized by systolic impairment. Disease-related mortality is most often attributable to sudden cardiac death, heart failure, and embolic stroke. The majority of individuals with HCM, however, have normal or near-normal life expectancy, owing in part to contemporary management strategies including family screening, risk stratification, thromboembolic prophylaxis, and implantation of cardioverter-defibrillators. The clinical guidelines for HCM issued by the ACC Foundation/AHA and the ESC facilitate evaluation and management of the disease. In this Review, we aim to assist clinicians in navigating the guidelines by highlighting important updates, current gaps in knowledge, differences in the recommendations, and challenges in implementing them, including aids and pitfalls in clinical and pathological evaluation. We also discuss the advances in genetics, imaging, and molecular research that will underpin future developments in diagnosis and therapy for HCM.

Contribution of Post-translational Phosphorylation to Sarcomere-Linked Cardiomyopathy Phenotypes

Secondary shifts develop in post-translational phosphorylation of sarcomeric proteins in multiple animal models of inherited cardiomyopathy. These signaling alterations together with the primary mutation are predicted to contribute to the overall cardiac phenotype. As a result, identification and integration of post-translational myofilament signaling responses are identified as priorities for gaining insights into sarcomeric cardiomyopathies. However, significant questions remain about the nature and contribution of post-translational phosphorylation to structural remodeling and cardiac dysfunction in animal models and human patients. This perspective essay discusses specific goals for filling critical gaps about post-translational signaling in response to these inherited mutations, especially within sarcomeric proteins. The discussion focuses primarily on pre-clinical analysis of animal models and defines challenges and future directions in this field.

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.

Involvement of the -420C>G RETN polymorphism in myocardial fibrosis in patients with hypertrophic cardiomyopathy

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and fibrosis. HCM is an autosomal-dominant disease caused by more than 400 mutations in sarcomeric genes. Changes in nonsarcomeric genes contribute to its phenotypic heterogeneity. Cardiac fibrosis can be studied using late gadolinium enhancement (LGE) cardiac magnetic resonance imaging. We evaluated the potential role of two polymorphisms in nonsarcomeric genes on interstitial fibrosis in HCM.

MATERIALS AND METHODS

Two polymorphisms in nonsarcomeric genes [ACE (deletion of 287 bp in the 16th intron) and RETN (-420C>G)] were analysed in 146 HCM patients. Cardiac fibrosis was assessed using LGE to determine the number of affected segments.

RESULTS

Allelic frequencies in ACE and RETN polymorphisms were consistent with the Hardy-Weinberg equilibrium (both P > 0.05). We found that the presence of the polymorphic allele in the -420C>G RETN polymorphism was independently associated with the number of affected segments of LGE (P = 0.038). Increased circulating resistin concentration, measured by enzyme-linked immunosorbent assay, was associated with a higher degree of cardiac fibrosis. Myocardial fibrosis, assessed by Masson's trichrome staining, was associated with the -420C>G RETN polymorphism in 46 tissue samples obtained by septal myectomy (P = 0.044).

CONCLUSIONS

The -420C>G RETN polymorphism was independently associated with the degree of cardiac fibrosis, assessed by LGE, in patients with HCM. In addition, there was an association between the polymorphism and the circulating resistin levels as well as with myocardial fibrosis in tissues obtained by myectomy. Investigating the physiological implication of the RETN polymorphism in HCM in combination with the use of imaging technologies might help to establish the severity of disease in patients with HCM.

Association between angiotensinogen M235T polymorphism and hypertrophic cardiomyopathy

BACKGROUND

To investigate the relationship between angiotensinogen (AGT) gene M235T polymorphism and hypertrophic cardiomyopathy (HCM) to explore the potential role of the AGT polymorphism in HCM.

METHODS

PubMed, Embase, OVID, Cochrane library, CNKI, Wan Fang Database were searched to identify the studies involving AGT M235T polymorphism and HCM. Two authors performed independent literature review and study quality assessment using the Newcastle-Ottawa Scale (NOS) checklist. A random-effects model was used to calculate the overall combined risk estimates.

RESULTS

Nine studies involving 887 cases and 1407 controls were included in our meta-analysis. No significant associations were found between AGT M235T polymorphism and HCM (allele model T vs M: OR = 1.17, 95% CI = 0.95-1.45; dominant model TT vs (MM/MT): OR = 1.21, 95% CI = 1.00-1.45; recessive model (TT/MT) vs MM: OR = 1.12, 95% CI = 0.87-1.45; heterozygous comparison MT vs MM: OR = 1.07, 95% CI = 0.82-1.41; homozygous comparison TT vs MM OR = 1.19, 95% CI = 0.88-1.61. In subgroup analysis, the significant difference of association between AGT M235T polymorphism and HCM existed in Asian and sporadic hypertrophic cardiomyopathy (SHCM), but no significant difference was found in Europeans and familial hypertrophic cardiomyopathy (FHCM).

CONCLUSIONS

There is no association between AGT M235T polymorphism and HCM in general populations, but such a relationship exists in Asians and SHCM.

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.

Gender specific association of RAS gene polymorphism with essential hypertension: a case-control study

Renin-angiotensin system (RAS) polymorphisms have been studied as candidate risk factors for hypertension with inconsistent results, possibly due to heterogeneity among various genetic and environmental factors. A case-control association study was conducted to investigate a possible involvement of polymorphisms of three RAS genes: AGT M235T (rs699), ACE I/D (rs4340) and G2350A (rs4343), and AGTR1 A1166C (rs5186) in essential hypertensive patients. A total of 211 cases and 211 controls were recruited for this study. Genotyping was performed using PCR-RFLP method. The genotype and allele distribution of the M235T variant differed significantly in hypertensives and normotensives (OR-CI = 2.62 (1.24–5.76), P = 0.006; OR-CI = 0.699 (0.518–0.943), P = 0.018), respectively. When the samples were segregated based on sex, the 235TT genotype and T allele were predominant in the female patients (OR-CI = 5.68 (1.60-25.10), P = 0.002; OR-CI = 0.522 (0.330–0.826), P = 0.005) as compare to the male patients (OR-CI = 1.54 (1.24–5.76), P = 0.34; OR-CI = 0.874 (0.330–0.826), P = 0.506), respectively. For ACE DD variant, we found overrepresentation of “I”-allele (homozygous II and heterozygous ID) in unaffected males which suggest its protective role in studied population (OR-CI = 0.401 (0.224–0.718); P = 0.0009). The M235T variant of the AGT is significantly associated with female hypertensives and ACE DD variant could be a risk allele for essential hypertension in south India.

The influence of Angiotensin converting enzyme and angiotensinogen gene polymorphisms on hypertrophic cardiomyopathy

Some studies have reported that angiotensin converting enzyme (ACE) and angiotensinogen (AGT) genes have been associated with hypertrophic cardiomyopathy (HCM). However, there have been inconsonant results among different studies. To clarify the influence of ACE and AGT on HCM, a systemic review and meta-analysis of case-control studies were performed. The following databases were searched to indentify related studies: PubMed database, the Embase database, the Cochrane Central Register of Controlled Trials database, China National Knowledge Information database, and Chinese Scientific and Technological Journal database. Search terms included "hypertrophic cardiomyopathy", "angiotensin converting enzyme" (ACE) or "ACE" and "polymorphism or mutation". For the association of AGT M235T polymorphism and HCM, "angiotensin converting enzyme" or "ACE" was replaced with "angiotensinogen". A total of seventeen studies were included in our review. For the association of ACE I/D polymorphism and HCM, eleven literatures were included in the meta-analysis on association of penetrance and genotype. Similarly, six case-control studies were included in the meta-analysis for AGT M235T. For ACE I/D polymorphism, the comparison of DI/II genotype vs DD genotype was performed in the present meta-analysis. The OR was 0.73 (95% CI: 0.527, 0.998, P = 0.049, power = 94%, alpha = 0.05) after the study which deviated from Hardy-Weinberg Equilibrium was excluded, indicating that the ACE I/D gene polymorphism might be associated with HCM. The AGT M235T polymorphism did not significantly affect the risk of HCM. In addition, ACE I/D gene polymorphism did not significantly influence the interventricular septal thickness in HCM patients. In conclusion, the ACE I/D polymorphism might be associated with the risk of HCM.

Temporal and morphological impact of pressure overload in transgenic FHC mice

Although familial hypertrophic cardiomyopathy (FHC) is characterized as cardiac disease in the absence of overt stressors, disease penetrance, and pathological progression largely depend on modifying factors. Accordingly, pressure overload by transverse aortic constriction (TAC) was induced in 2-month-old, male mice with and without a FHC (R403Q) mutation in α-myosin heavy chain. A significantly greater number of FHC mice (n = 8) than wild-type (WT) mice (n = 5) died during the 9-week study period. TAC induced a significant increase in cardiac mass whether measured at 2 or 9 weeks post-TAC in both WT and FHC mice, albeit to a different extent. However, the temporal and morphological trajectory of ventricular remodeling was impacted by the FHC transgene. Both WT and FHC hearts responded to TAC with an early (2 weeks post-TAC) and significant augmentation of the relative wall thickness (RWT) indicative of concentric hypertrophy. By 9 weeks post-TAC, RWT decreased in WT hearts (eccentric hypertrophy) but remained elevated in FHC hearts. WT hearts following TAC demonstrated enhanced cardiac function as measured by the end-systolic pressure-volume relationship, pre-load recruitable stroke work (PRSW), and myocardial relaxation indicative of compensatory hypertrophy. Similarly, TAC induced differential histological and cellular remodeling; TAC reduced expression of the sarcoplasmic reticulum Ca(2+)-ATPase (2a) (SERCA2a; 2 and 9 weeks) and phospholamban (PLN; 2 weeks) but increased PLN phosphorylation (2 weeks) and β-myosin heavy chain (β-MyHC; 9 weeks) in WT hearts. FHC-TAC hearts showed increased β-MyHC (2 and 9 weeks) and a late (9 weeks) decrease in PLN expression concomitant with a significant increase in PLN phosphorylation. We conclude that FHC hearts respond to TAC induced pressure overload with increased premature death, severe concentric hypertrophy, and a differential ability to undergo morphological, functional, or cellular remodeling compared to WT hearts.

AT1 blockade abolishes left ventricular hypertrophy in heterozygous cMyBP-C null mice: role of FHL1

This research investigated the impact of angiotensin AT1 receptor (Agtr1) blockade on left ventricular (LV) hypertrophy in a mouse model of human hypertrophic cardiomyopathy (HCM), which carries one functional allele of Mybpc3 gene coding cardiac myosin-binding protein C (cMyBP-C). Five-month-old heterozygous cMyBP-C knockout (Het-KO) and wild-type mice were treated with irbesartan (50 mg/kg/day) or vehicle for 8 weeks. Arterial blood pressure was measured by tail cuff plethysmography. LV dimension and function were accessed by echocardiography. Myocardial gene expression was evaluated using RT-qPCR. Compared with wild-type littermates, Het-KO mice had greater LV/body weight ratio (4.0 ± 0.1 vs. 3.3 ± 0.1 mg/g, P < 0.001), thicker interventricular septal wall (0.70 ± 0.02 vs. 0.65 ± 0.01 mm, P < 0.02), lower Mybpc3 mRNA level (-43%, P < 0.02), higher four-and-a-half LIM domains 1 (Fhl1, +110%, P < 0.01), and angiotensin-converting enzyme 1 (Ace1, +67%, P < 0.05), but unchanged Agtr1 mRNA levels in the septum. Treatment with irbesartan had no effect in wild-type mice but abolished septum-predominant LV hypertrophy and Fhl1 upregulation without changes in Ace1 but with an increased Agtr1 (+42%) in Het-KO mice. Thus, septum-predominant LV hypertrophy in Het-KO mice is combined with higher Fhl1 expression, which can be abolished by AT1 receptor blockade, indicating a role of the renin-angiotensin system and Fhl1 in cMyBP-C-related HCM.

New polymorphisms in human MEF2C gene as potential modifier of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is caused by mutations in genes encoding sarcomeric proteins. Its variable phenotype suggests the existence of modifier genes. Myocyte enhancer factor (MEF) 2C could be important in this process given its role as transcriptional regulator of several cardiac genes. Any variant affecting MEF2C expression and/or function may impact on hypertrophic cardiomyopathy clinical manifestations. In this candidate gene approach, we screened 209 Caucasian hypertrophic cardiomyopathy patients and 313 healthy controls for genetic variants in MEF2C gene by single-strand conformation polymorphism analysis and direct sequencing. Functional analyses were performed with transient transfections of luciferase reporter constructions. Three new variants in non-coding exon 1 were found both in patients and controls with similar frequencies. One-way ANOVA analyses showed a greater left ventricular outflow tract obstruction (p = 0.011) in patients with 10C+10C genotype of the c.-450C(8_10) variant. Moreover, one patient was heterozygous for two rare variants simultaneously. This patient presented thicker left ventricular wall than her relatives carrying the same sarcomeric mutation. In vitro assays additionally showed a slightly increased transcriptional activity for both rare MEF2C alleles. In conclusion, our data suggest that 15 bp-deletion and C-insertion in the 5'UTR region of MEF2C could affect hypertrophic cardiomyopathy, potentially by affecting expression of MEF2C and therefore, the expression of their target cardiac proteins that are implicated in the hypertrophic process.

The role of renin-angiotensin-aldosterone system polymorphisms in phenotypic expression of MYBPC3-related hypertrophic cardiomyopathy

The phenotypic variability of hypertrophic cardiomyopathy (HCM) in patients with identical pathogenic mutations suggests additional modifiers. In view of the regulatory role in cardiac function, blood pressure, and electrolyte homeostasis, polymorphisms in the renin-angiotensin-aldosterone system (RAAS) are candidates for modifying phenotypic expression. In order to investigate whether RAAS polymorphisms modulate HCM phenotype, we selected a large cohort of carriers of one of the three functionally equivalent truncating mutations in the MYBPC3 gene. Family-based association analysis was performed to analyze the effects of five candidate RAAS polymorphisms (ACE, rs4646994; AGTR1, rs5186; CMA, rs1800875; AGT, rs699; CYP11B2, rs1799998) in 368 subjects carrying one of the three mutations in the MYBPC3 gene. Interventricular septum (IVS) thickness and Wigle score were assessed by 2D-echocardiography. SNPs in the RAAS system were analyzed separately and combined as a pro-left ventricular hypertrophy (LVH) score for effects on the HCM phenotype. Analyzing the five polymorphisms separately for effects on IVS thickness and Wigle score detected two modest associations. Carriers of the CC genotype in the AGT gene had less pronounced IVS thickness compared with CT and TT genotype carriers. The DD polymorphism in the ACE gene was associated with a high Wigle score (P=0.01). No association was detected between the pro-LVH score and IVS thickness or Wigle score. In conclusion, in contrast to previous studies, in our large study population of HCM patients with functionally equivalent mutations in the MYBPC3 gene we did not find major effects of genetic variation within the genes of the RAAS system on phenotypic expression of HCM.

A polymorphic miR-155 binding site in AGTR1 is associated with cardiac hypertrophy in Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition with a heterogeneous cardiac phenotype caused primarily by an expanded GAA trinucleotide repeat in the frataxin gene (FXN). FXN is important in mitochondrial iron efflux, sensitivity to oxidative stress, and cell death. The number of GAA repeats on the smaller FXN allele (GAA1) only accounts for a portion of the observed variability in cardiac phenotype. Genetic modifying factors, such as single nucleotide polymorphisms (SNPs) in genes of the Renin-Angiotensin-Aldosterone system (RAAS), may contribute to phenotype variability. This study investigated genetic variability in the angiotensin-II type-1 receptor (AGTR1), angiotensin-converting enzyme (ACE), and ACE2 genes as cardiac phenotype modifying factors in FRDA patients. Comprehensive review of the AGTR1, ACE and ACE2 genes identified twelve haplotype tagging SNPs. Correlation of these SNPs with left ventricular internal diameter in diastole (LVIDd), interventricular septal wall thickness (SWT) and left ventricular mass (LVM) was examined in a large Australian FRDA cohort (n=79) with adjustments performed for GAA repeats, age, sex, body surface area and diastolic blood pressure. A significant inverse relationship was observed between GAA1 and LVIDd (p=0.010) but not with SWT or LVM after adjustment for covariates. The AGTR1 polymorphism rs5186 was more common in FRDA patients than in a control population (p=0.002). Using a recessive model of inheritance, the C allele of rs5186 was associated with a significant increase in SWT (p=0.003) and LVM (p=0.001). This functional polymorphism increases expression of AGTR1 by altering the binding site for miR-155, a regulatory microRNA. No significant associations with left ventricular structure were observed for the remaining RAAS polymorphisms. The AGTR1 polymorphism rs5186 appears to modify the FRDA cardiac phenotype independently of GAA1. This study supports the role of RAAS polymorphisms as modifiers of cardiac phenotype in FRDA patients.

Renin-angiotensin-aldosterone genotype influences ventricular remodeling in infants with single ventricle

BACKGROUND

We investigated the effect of polymorphisms in the renin-angiotensin-aldosterone system (RAAS) genes on ventricular remodeling, growth, renal function, and response to enalapril in infants with single ventricle.

METHODS AND RESULTS

Single ventricle infants enrolled in a randomized trial of enalapril were genotyped for polymorphisms in 5 genes: angiotensinogen, angiotensin-converting enzyme, angiotensin II type 1 receptor, aldosterone synthase, and chymase. Alleles associated with renin-angiotensin-aldosterone system upregulation were classified as risk alleles. Ventricular mass, volume, somatic growth, renal function using estimated glomerular filtration rate, and response to enalapril were compared between patients with ≥2 homozygous risk genotypes (high risk), and those with <2 homozygous risk genotypes (low risk) at 2 time points: before the superior cavopulmonary connection (pre-SCPC) and at age 14 months. Of 230 trial subjects, 154 were genotyped: Thirty-eight were high risk, and 116 were low risk. Ventricular mass and volume were elevated in both groups pre-SCPC. Ventricular mass and volume decreased and estimated glomerular filtration rate increased after SCPC in the low-risk (P<0.05), but not the high-risk group. These responses were independent of enalapril treatment. Weight and height z-scores were lower at baseline, and height remained lower in the high-risk group at 14 months, especially in those receiving enalapril (P<0.05).

CONCLUSIONS

Renin-angiotensin-aldosterone system-upregulation genotypes were associated with failure of reverse remodeling after SCPC surgery, less improvement in renal function, and impaired somatic growth, the latter especially in patients receiving enalapril. Renin-angiotensin-aldosterone system genotype may identify a high-risk subgroup of single ventricle patients who fail to fully benefit from volume-unloading surgery. Follow-up is warranted to assess long-term impact.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00113087.

Impact of polymorphisms in the renin–angiotensin–aldosterone system on hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous autosomal dominant heart disease characterised by left ventricular hypertrophy in the absence of another cardiac or systemic disease that is capable of producing significant wall thickening. Microscopically it is characterised by cardiomyocyte hypertrophy, myofibrillar disarray and fibrosis. The phenotypic expression of HCM is multifactorial, with the majority of cases occurring secondary to mutations in genes encoding the sarcomere proteins. In conjunction with the genetic heterogeneity of HCM, phenotypic expression also exhibits a high level of variability even within families with the same aetiological mutation, and may be influenced by additional genetic factors. Polymorphisms of the renin–angiotensin–aldosterone system (RAAS) represent an attractive hypothesis as potential disease modifiers, as these genetic variants alter the ‘activation status’ of the RAAS, which leads to more left ventricular hypertrophy through different pathways. The main objective of this review is to provide an overview of the role of different polymorphisms identified in the RAAS, in patients with HCM.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy has important differences in children compared with adults, particularly with regard to the range of causes and the outcomes in infants. Survival is highly dependent on etiology, particularly in the youngest patients, and pursuit of the specific cause is therefore necessary. The clinical utility of defining the genotype in children with familial hypertrophic cardiomyopathy exceeds that at other ages and has a highly favorable cost/benefit ratio. Although most of the available information concerning treatment and prevention of sudden death is derived in adults, management of children requires consideration of the differences in age-specific risk/benefit ratios.

Genetic variation in angiotensin II type 2 receptor gene influences extent of left ventricular hypertrophy in hypertrophic cardiomyopathy independent of blood pressure

Introduction. Hypertrophic cardiomyopathy (HCM), an inherited primary cardiac disorder mostly caused by defective sarcomeric proteins, serves as a model to investigate left ventricular hypertrophy (LVH). HCM manifests extreme variability in the degree and distribution of LVH, even in patients with the same causal mutation. Genes coding for renin—angiotensin—aldosterone system components have been studied as hypertrophy modifiers in HCM, with emphasis on the angiotensin (Ang) II type 1 receptor (AT1R). However, Ang II binding to Ang II type 2 receptors (AT2R) also has hypertrophy-modulating effects.

Methods. We investigated the effect of the functional +1675 G/A polymorphism (rs1403543) and additional single nucleotide polymorphisms in the 3’ untranslated region of the AT2R gene ( AGTR2) on a heritable composite hypertrophy score in an HCM family cohort in which HCM founder mutations segregate.

Results. We find significant association between rs1403543 and hypertrophy, with each A allele decreasing the average wall thickness by ~0.5 mm, independent of the effects of the primary HCM causal mutation, blood pressure and other hypertrophy covariates ( p = 0.020).

Conclusion. This study therefore confirms a hypertrophy-modulating effect for AT2R also in HCM and implies that +1675 G/A could potentially be used in a panel of markers that profile a genetic predisposition to LVH in HCM.

Mutational Heterogeneity, Modifier Genes, and Environmental Influences Contribute to Phenotypic Diversity of Arrhythmogenic Cardiomyopathy

Background—

Arrhythmogenic cardiomyopathy is one of the leading causes of sudden cardiac death in the ≤35-year age group. The broad phenotypic spectrum encompasses left-dominant and biventricular subtypes, characterized by early left ventricular involvement, as well as the classic right-dominant form, better known as arrhythmogenic right ventricular cardiomyopathy. Mendelian inheritance patterns are accompanied by incomplete penetrance and variable expressivity, the latter manifesting as diversity in morphology, arrhythmic burden, and clinical outcomes.

Methods and Results—

To investigate the role of mutational heterogeneity, genetic modifiers and environmental influences in arrhythmogenic cardiomyopathy, we studied phenotype variability in 9 quantitative traits among an affected-only sample of 231 cases from 48 families. Heritability was estimated by variance component analysis as a guide to the combined influence of mutational and genetic background heterogeneity. Nested ANOVA was used to distinguish mutational and genetic modifier effects. Heritability estimates ranged from 20% to 77%, being highest for left ventricular ejection fraction and right–to–left ventricular volume ratio and lowest for the ventricular arrhythmia grade, suggesting differing genetic and environmental contributions to these traits. ANOVA models indicated a predominant mutation effect for the left ventricular lesion score, an indicator of the extent of fat and late enhancement on cardiovascular magnetic resonance. In contrast, the modifier genetic effect appeared significant for right ventricular end-diastolic volume, ejection fraction, and lesion score; left ventricular ejection fraction; ventricular volume ratio; and arrhythmic events.

Conclusions—

Systematic investigation of modifier genes and environmental influences will be pivotal to understanding clinical diversity in arrhythmogenic cardiomyopathy, refining prognostication, and developing targeted therapies.

Prevalence and spectrum of mutations in a cohort of 192 unrelated patients with hypertrophic cardiomyopathy

Hypertrophic Cardiomyopathy (HCM), a common and clinically heterogeneous disease characterized by unexplained ventricular myocardial hypertrophy and a high risk of sudden cardiac death, is mostly caused by mutations in sarcomeric genes but modifiers genes may also modulate the phenotypic expression of HCM mutations. The aim of the current study was to report the frequency of single and multiple gene mutations in a large French cohort of HCM patients and to evaluate the influence of polymorphisms previously suggested to be potential disease modifiers in this myocardial pathology. We report the molecular screening of 192 unrelated HCM patients using denaturing high-performance liquid chromatography/sequencing analysis of the MYBPC3, MYH7, TNNT2 and TNNI3 genes. Genotyping of 6 gene polymorphisms previously reported as putative HCM modifiers (5 RAAS polymorphisms and TNF-α -308 G/A) was also performed. Seventy-five mutations were identified in 92 index patients (48%); 32 were novel. MYBPC3 mutations (25%) represent the most prevalent cause of inherited HCM whereas MYH7 mutations (12%) rank second in the pathogenesis. The onset age was older in patients carrying MYBPC3 mutations than in those with MYH7 mutations. The MYBPC3 IVS20-2A>G splice mutation was identified in 7% of our HCM population. Multiple gene mutations were identified in 9 probands (5%), highlighting the importance of screening other HCM-causing genes even after a first mutation has been identified, particularly in young patients with a severe phenotype. No single or cumulative genetic modifier effect could be evidenced in this HCM cohort.

Renin-angiotensin-aldosterone system gene polymorphisms in coronary artery bypass graft surgery patients

INTRODUCTION

Candidates for coronary artery bypass grafting (CABG) represent a group of patients with well documented, severe coronary artery disease (CAD). Genetic polymorphisms of renin-angiotensin-aldosterone system (RAAS) components have been associated with CAD. We examined the association of polymorphisms of angiotensin-converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II type 1 receptor (AT(1) receptor) with severe CAD in CABG patients.

MATERIALS AND METHODS

One hundred and fifty-four CABG patients and 155 non-CAD controls were included in the study. Established PCR methods were used for genotyping of AGT M235T, AGT T174M, AT(1) receptor A1166C, and ACE I/D polymorphisms. Cumulative effect of analysed polymorphisms was assessed by calculation of each individual's RAAS gene score (addition of 0.5 points for each variant allele and then calculating the sum for all four polymorphisms).

RESULTS

No association between AGT M235T, AGT T174M, ACE I/D and AT(1) receptor A1166C polymorphisms and CAD was observed. Within CABG patients, the frequency of homozygous AGT 235TT genotype was higher in hypertensive compared to normotensive CABG patients (21.7% vs. 6.3%, p=0.03). RAAS gene score did not differ between CABG patients and non-CAD controls.

CONCLUSIONS

There is no association of the analysed RAAS polymorphisms with severe CAD in CABG patients. However, within these patients, an association was found between AGT 235TT genotype and hypertension.

Histologic characterization of hypertrophic cardiomyopathy with and without myofilament mutations

BACKGROUND

Between 30% and 60% of clinical cases of hypertrophic cardiomyopathy (HC) can be attributed to mutations in the genes encoding cardiac myofilament proteins. Interestingly, it appears that the likelihood of an underlying myofilament mutation can be predicted by echocardiographic assessment of left ventricular morphology. However, it is not known whether genotypically characterized HC exists as a separate entity with discrete phenotypic morphology and histology or to what extent recognized polymorphisms of the renin-angiotensin-aldosterone system (RAAS) influence this relationship. The presence of cardiac myofilament and mutations and RAAS polymorphisms will have a strong association with the severity of histologic features of HC and characteristic septal shape.

METHODS

We conducted a retrospective review of histology specimens, obtained at septal myectomy among 181 patients with medically refractory symptomatic HC. All patients underwent comprehensive genetic analysis for mutations in 8 myofilament-encoding genes; a subset was genotyped for 6 known RAAS-polymorphisms. Patients underwent comprehensive echocardiography by an expert blinded to genotype and microscopic status.

RESULTS

Microscopically, severity of myocyte hypertrophy appears to be associated with the presence of recognized HC cardiac myofilament mutations (P = .03). Other histologic features characteristic of HC were not consistently associated with myofilament mutation status. A higher burden of pro-LVH RAAS polymorphisms also appeared to predict only myocyte hypertrophy (P = .01). The presence of RAAS polymorphisms was not associated with the development of a specific septal morphology (P = .6).

CONCLUSION

Myofilament-positive HC does not appear to represent a distinct clinical phenotypic entity as evidenced by specific histologic characteristics and septal shape.

Polymorphism in the angiotensin II type 1 receptor (AGTR1) is associated with age at diagnosis in pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare, lethal disease associated with single gene disorders, connective tissue disease, exposures to anorexigens, and often, idiopathic etiology. Genes can modify the risk of PAH: (1) monogenic disorders associated with PAH are incompletely penetrant, and (2) not all patients with associated conditions at increased risk for PAH develop the disease. The renin angiotensin aldosterone system (RAAS) provides a set of candidate genes that could modulate pulmonary vascular disease similar to its effects on renal and peripheral vasculature.

METHODS

We studied 247 patients with PAH, comprising 177 with idiopathic PAH (IPAH), 63 with PAH/connective tissue disease (CTD), and 7 with PAH associated with anorexigens. Patients were genotyped for 5 common polymorphisms in angiotensinogen (AGT), angiotensin-converting enzyme (ACE), cardiac chymase A (CMA1), angiotensin II type 1 receptor (AGTR1), and aldosterone synthase (CYP11B2). Genotypes were tested for associations with age at diagnosis, hemodynamic parameters at diagnosis, and/or response to acute pulmonary vasodilator testing at diagnosis.

RESULTS

Associations were demonstrated for AGTR1 and age at diagnosis in IPAH (p = 0.005). Homozygotes for the 1166C allele (n = 13) were associated with an age at diagnosis 26 years later than those with A/A (n = 139) or A/C (n = 90) genotypes. No associations were demonstrated for AGT, ACE, CMA1, or CYP11B2.

CONCLUSIONS

The 1166C polymorphism in AGTR1 appears to be associated with a later age at diagnosis in IPAH, suggesting that this pathway could be involved in the biologic variability that is known to occur in PAH.

Diagnostic, prognostic, and therapeutic implications of genetic testing for hypertrophic cardiomyopathy

Over the last 2 decades, the pathogenic basis for the most common heritable cardiovascular disease, hypertrophic cardiomyopathy (HCM), has been investigated extensively. Affecting approximately 1 in 500 individuals, HCM is the most common cause of sudden death in young athletes. In recent years, genomic medicine has been moving from the bench to the bedside throughout all medical disciplines including cardiology. Now, genomic medicine has entered clinical practice as it pertains to the evaluation and management of patients with HCM. The continuous research and discoveries of new HCM susceptibility genes, the growing amount of data from genotype-phenotype correlation studies, and the introduction of commercially available genetic tests for HCM make it essential that the modern-day cardiologist understand the diagnostic, prognostic, and therapeutic implications of HCM genetic testing.

A study of the relationships between angiotensin- converting enzyme gene, chymase gene polymorphisms, pharmacological treatment with ACE inhibitor and regression of left ventricular hypertrophy in essential hypertension patients treated with benazepril

BACKGROUND

About 15-37% of the adult population worldwide suffers from hypertension. Hypertension is responsible for one-third of all global deaths. Left ventricular hypertrophy (LVH) is one of the most important characteristics of hypertension target organ damage and is also an independent risk factor for cardiovascular events. Therefore, effective regression of LVH is a main aim of hypertension treatment and also an important public health concern. However, few studies of the regression of LVH have been reported. In particular, little is known about the relationship between the genotypes of angiotensin-converting enzyme (ACE) and chymase (CMA) genes, and the effectiveness of antihypertensive drugs in regression of LVH.

AIM

The study investigated whether the insertion/deletion (I/D) polymorphism of ACE gene and the A/B polymorphism of the CMA gene are related to the regression of LVH in essential hypertension patients who were participants in a long-term trial of therapy with benazepril.

SUBJECTS AND METHODS

Data from 157 patients was collected and used in the analysis. The genotypes of ACE and CMA genes were identified by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Left ventricular mass (LVM) was measured by echocardiography, and left ventricular mass index (LVMI) was calculated.

RESULTS

Blood pressure was markedly reduced and heart rate was unchanged by long-term treatment with benazepril. Regression of LVH was observed. The mean reduction in LVMI was 41.50+/-28.48 g m-2. Reduction of LVM, LVMI and percentage reduction of LVMI were more in the DD group than in the II and ID groups (P<0.05). No significant difference in other indices was found in the different genotype groups of ACE (P>0.05). No significant difference in all indices was found among the different genotype groups of CMA (P>0.05). No interaction was found between the genotypes of ACE and CMA.

CONCLUSION

Hypertension patients with the DD genotype are more likely to have regression of LVH when treated with benazepril than patients with other genotypes of ACE. No evidence was found to support an association between CMA genotype and regression of LVH in patients or to support the interaction between the two genes in regression of LVH.

Association of angiotensin-converting enzyme activity and polymorphism with echocardiographic measures in familial and nonfamilial hypertrophic cardiomyopathy

Angiotensin-converting enzyme (ACE) activity and polymorphism contribute significantly to the prognosis of patients with cardiomyopathy. The aim of this study was to determine the activity and type of ACE polymorphism in patients with familial and nonfamilial hypertrophic cardiomyopathy (HCM) and to correlate these with echocardiographic measurements (echo-Doppler). We studied 136 patients (76 males) with HCM (69 familial and 67 nonfamilial cases). Mean age was 41 +/- 17 years. DNA was extracted from blood samples for the polymerase chain reaction and the determination of plasma ACE levels. Left ventricular mass, interventricular septum, and wall thickness were measured. Mean left ventricular mass index, interventricular septum and wall thickness in familial and nonfamilial forms were 154 +/- 63 and 174 +/- 57 g/m(2) (P = 0.008), 19 +/- 5 and 21 +/- 5 mm (P = 0.02), and 10 +/- 2 and 12 +/- 3 mm (P = 0.0001), respectively. ACE genotype frequencies were DD = 35%, ID = 52%, and II = 13%. A positive association was observed between serum ACE activity and left ventricular mass index (P = 0.04). Logistic regression showed that ACE activity was twice as high in patients with familial HCM and left ventricular mass index >or=190 g/m(2) compared with the nonfamilial form (P = 0.02). No other correlation was observed between ACE polymorphisms and the degree of myocardial hypertrophy. In conclusion, ACE activity, but not ACE polymorphisms, was associated with the degree of myocardial hypertrophy in the patients with HCM.

Rationale and design of a trial of angiotensin-converting enzyme inhibition in infants with single ventricle

BACKGROUND

Angiotensin converting enzyme (ACE) inhibitors are known to improve clinical outcome and ventricular function in adults with heart failure. Infants with single-ventricle physiology show abnormalities in ventricular function as well as poor growth. The ability of an ACE inhibitor to preserve ventricular function and improve growth in these infants is unknown.

METHODS

The Pediatric Heart Network designed a randomized, double-blind trial to compare outcomes in infants with single-ventricle physiology receiving enalapril or placebo. Neonates < or =45 days old were eligible. The primary outcome is weight-for-age Z-score at 14 months of age. Secondary outcomes include other measures of somatic growth, laboratory and functional measures of heart failure, developmental indices, measures of ventricular size and function, and the relationship of the renin-angiotensin-aldosterone system genotype to the response to enalapril. The incidence and spectrum of adverse events will also be compared between treatment groups.

RESULTS

A total of 1,245 neonates were screened and 533 (43%) were eligible. The consent rate was 43%; 230 subjects were enrolled. Parental reluctance to participate was the primary reason for non-consent in 79% of the eligible nonconsenting patients. Randomized patients were older, more likely to be male, and more likely to have hypoplastic left heart syndrome than the eligible patients who did not enroll.

CONCLUSIONS

The results of this randomized trial will make an important contribution to the management of infants with single-ventricle physiology by determining whether initiation of ACE inhibition therapy in the neonatal period improves growth, clinical outcome, and ventricular function.