Genes for left ventricular hypertrophy

Echocardiography Predictors of Survival in Hypertensive Patients With Left Ventricular Hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH) is a well-known target organ damage. Concentric hypertrophy is the strongest predictor of increased risk of cardiovascular events, but the predictive value of individual echocardiographic parameters remains unclear.The aim of this study was to search for echocardiographic and hemodynamic variables associated with concentric and eccentric remodeling and their association with long-term cardiovascular outcomes.

METHODS

Patients with echocardiography performed within 1 year prior to the initial clinic visit were included into the study. Logistic regression and multivariable Cox-proportional hazards were calculated according to several risk factors and variables. Additionally, cubic spline interpolation was used.

RESULTS

We observed 690 patients for 10 years. There was a total of 177 major adverse cardiac and cerebrovascular events (MACCE) and 90 deaths over a 10-year period. Left ventricular concentric hypertrophy is associated with worse outcomes than eccentric hypertrophy in hypertensive subjects. Interestingly, different echocardiographic parameters contributed to risk depending on type of hypertrophy. In concentric hypertrophy, relative wall thickness provides linear prediction of risk for all-cause mortality (ACM) and composite endpoint. Systolic blood pressure is a significant predictor of MACCE. Blood pressure variability also showed significant predictive value for MACCE and ACM.

CONCLUSIONS

These data indicate risk stratification based on LVH need to consider different measures based on the type of remodeling.

Left ventricular cardiac geometry and ambulatory blood pressure in children

Limited information is available regarding the relationship between ambulatory blood pressure monitoring (ABPM) and cardiac geometry in hypertensive children. ABPM and 2D-echocardiography were retrospectively reviewed in children and adolescents <21 years old with primary hypertension. A total of 119 participants (median age 15.0 [IQR 12, 16] years) with hypertension were included. Left ventricular hypertrophy was diagnosed in 39.5% of participants. Normal geometry was found in 47.1%, concentric remodeling (CR) in 13.4%, concentric hypertrophy (CH) in 15.1%, and eccentric hypertrophy (EH) in 24.4% of children. After adjustment for age, sex, and body mass index z-score, awake systolic blood pressure (BP) index (BPi) (OR 1.07, 95% CI: 1.001-1.14, P = 0.045), awake diastolic BPi (OR 1.04, 95% CI: 1.00-1.09, P = 0.048), awake systolic BP load (OR 1.02, 95% CI: 1.000-1.04, P = 0.047), and sleep systolic BP load (OR 1.02, 95% CI: 1.001-1.04, P = 0.03) were directly associated with CH. No ABPM parameters were significant predictors of EH. In conclusion, ABPM parameters were found to be independent predictors of cardiac geometry, specifically CH.

A combined linkage, microarray and exome analysis suggests MAP3K11 as a candidate gene for left ventricular hypertrophy

BACKGROUND

Electrocardiographic measures of left ventricular hypertrophy (LVH) are used as predictors of cardiovascular risk. We combined linkage and association analyses to discover novel rare genetic variants involved in three such measures and two principal components derived from them.

METHODS

The study was conducted among participants from the Erasmus Rucphen Family Study (ERF), a Dutch family-based sample from the southwestern Netherlands. Variance components linkage analyses were performed using Merlin. Regions of interest (LOD > 1.9) were fine-mapped using microarray and exome sequence data.

RESULTS

We observed one significant LOD score for the second principal component on chromosome 15 (LOD score = 3.01) and 12 suggestive LOD scores. Several loci contained variants identified in GWAS for these traits; however, these did not explain the linkage peaks, nor did other common variants. Exome sequence data identified two associated variants after multiple testing corrections were applied.

CONCLUSIONS

We did not find common SNPs explaining these linkage signals. Exome sequencing uncovered a relatively rare variant in MAPK3K11 on chromosome 11 (MAF = 0.01) that helped account for the suggestive linkage peak observed for the first principal component. Conditional analysis revealed a drop in LOD from 2.01 to 0.88 for MAP3K11, suggesting that this variant may partially explain the linkage signal at this chromosomal location. MAP3K11 is related to the JNK pathway and is a pro-apoptotic kinase that plays an important role in the induction of cardiomyocyte apoptosis in various pathologies, including LVH.

Prognostic Application of Thoracic Aortic Calcium Scoring for Adverse Clinical Outcome Risk in Elderly Patients with Left Ventricular Hypertrophy

Background and Objectives

Left ventricular hypertrophy (LVH) is associated with poor cardiovascular outcomes. Heavy aortic calcification exacerbates arterial stiffness, which consequently heightens left ventricular (LV) afterload. We assessed the usefulness of aortic calcification for predicting adverse cardiovascular outcomes and to determine whether the relationship, if any, differed as a function of LVH.

Methods

The analytic sample was comprised of a total of 487 individuals 65 years of age or older. Thoracic aorta calcium score (TACS) was measured by coronary computed tomography, and patients were stratified according to the median (TACS, 446 mm³). LVH obtained from echocardiography was defined as LV mass index >115 g/m² for men and >95 g/m² for women. Cox regression reporting hazard ratios (HRs) with 95% confidence intervals (CIs) was performed to predict the risk for the composite study endpoint, defined as cardiac death, admission for heart failure, obstructive coronary artery disease (CAD) requiring revascularization, or stroke.

Results

A total of 39 composite events (8.0%) occurred during a median follow-up of 65 months (interquartile range [IQR], 17–89 months). For those with LVH, the concurrent presence of high TACS appeared to be an independent predictor (HR, 4.51; 95% CI, 1.71–11.88; p=0.002) for the composite study endpoint. Other combined LVH and TACS subgroups were not associated with significant factors for predicting the composite study endpoint (p>0.050, all).

Conclusion

TACS provides robust predictive utility for a composite of cardiovascular events and cardiac death in persons with LVH. This finding was less pronounced in those with a relatively healthy myocardium, defined by the absence of LVH.

Left ventricular hypertrophy and arrhythmogenesis

Left ventricular hypertrophy (LVH) poses an independent risk of increased morbidity and mortality, including atrial arrhythmias, ventricular arrhythmias, and sudden cardiac death. The most common causes of LVH are hypertension and valvular heart disease. Electrocardiography and echocardiography are the first steps in the diagnosis and evaluation of therapy in patients with LVH. Cardiac MRI is the gold standard in diagnosis and assessment of response to therapy. Management of LVH should be based on etiology, evidence, and guideline adherence. Timely and optimal management of the underlying cause of LVH results in improvement (regression) of LVH and its related complications.

Fetal-adult cardiac transcriptome analysis in rats with contrasting left ventricular mass reveals new candidates for cardiac hypertrophy

Reactivation of fetal gene expression patterns has been implicated in common cardiac diseases in adult life including left ventricular (LV) hypertrophy (LVH) in arterial hypertension. Thus, increased wall stress and neurohumoral activation are discussed to induce the return to expression of fetal genes after birth in LVH. We therefore aimed to identify novel potential candidates for LVH by analyzing fetal-adult cardiac gene expression in a genetic rat model of hypertension, i.e. the stroke-prone spontaneously hypertensive rat (SHRSP). To this end we performed genome-wide transcriptome analysis in SHRSP to identify differences in expression patterns between day 20 of fetal development (E20) and adult animals in week 14 in comparison to a normotensive rat strain with contrasting low LV mass, i.e. Fischer (F344). 15232 probes were detected as expressed in LV tissue obtained from rats at E20 and week 14 (p < 0.05) and subsequently screened for differential expression. We identified 24 genes with SHRSP specific up-regulation and 21 genes with down-regulation as compared to F344. Further bioinformatic analysis presented Efcab6 as a new candidate for LVH that showed only in the hypertensive SHRSP rat differential expression during development (logFC = 2.41, p < 0.001) and was significantly higher expressed in adult SHRSP rats compared with adult F344 (+ 76%) and adult normotensive Wistar-Kyoto rats (+ 82%). Thus, it represents an interesting new target for further functional analyses and the elucidation of mechanisms leading to LVH. Here we report a new approach to identify candidate genes for cardiac hypertrophy by combining the analysis of gene expression differences between strains with a contrasting cardiac phenotype with a comparison of fetal-adult cardiac expression patterns.

Myocardial remodeling in hypertension

Left ventricular (LV) hypertrophy and remodeling are frequently seen in hypertensive subjects and result from a complex interaction of several hemodynamic and non-hemodynamic variables. Although increased blood pressure is considered the major determinant of LV structural alterations, ethnicity, gender, environmental factors, such as salt intake, obesity and diabetes mellitus, as well as neurohumoral and genetic factors might influence LV mass and geometry. The conventional concept of hypertensive LV remodeling has been that hypertension leads to concentric hypertrophy, as an adaptive response to normalize wall stress, which is then followed by chamber dilation and heart failure. However, several lines of evidence have challenged this dogma. Concentric hypertrophy is not the most frequent geometric pattern and is less usually seen than eccentric hypertrophy in hypertensive subjects. In addition, data from recent studies suggested that transition from LV concentric hypertrophy to dilation and systolic dysfunction is not a common finding, especially in the absence of coronary heart disease. LV hypertrophy is also consistently associated with increased cardiovascular morbidity and mortality, raising doubts whether this phenotype is an adaptive response. Experimental evidence exists that a blunting of load-induced cardiomyocyte hypertrophy does not necessarily result in LV dysfunction or failure. Furthermore, the hypertrophic myocardium shows fibrosis, alterations in the coronary circulation and cardiomyocyte apoptosis, which may result in heart failure, myocardial ischemia and arrhythmias. Overall, this body of evidence suggests that LV hypertrophy is a complex phenotype that predicts adverse cardiovascular outcomes and may not be necessarily considered as an adaptive response to systemic hypertension.

Mapping and confirmation of a major left ventricular mass QTL on rat chromosome 1 by contrasting SHRSP and F344 rats

An abnormal increase in left ventricular (LV) mass, i.e., LV hypertrophy (LVH), represents an important target organ damage in arterial hypertension and has been associated with poor clinical outcome. Genetic factors are contributing to variation in LV mass in addition to blood pressure and other factors such as dietary salt intake. We set out to map quantitative trait loci (QTL) for LV mass by comparing the spontaneously hypertensive stroke-prone (SHRSP) rat with LVH and normotensive Fischer rats (F344) with contrasting low LV mass. To this end we performed a genome-wide QTL mapping analysis in 232 F2 animals derived from SHRSP and F344 exposed to high-salt (4% in chow) intake for 8 wk. We mapped one major QTL for LV mass on rat chromosome 1 (RNO1) that demonstrated strong linkage (peak logarithm of odds score 8.4) to relative LV weight (RLVW) and accounted for ∼19% of the variance of this phenotype in F2 rats. We therefore generated a consomic SHRSP-1(F344) strain in which RNO1 from F344 was introgressed into the SHRSP background. Consomic and SHRSP animals showed similar blood pressures during conventional intra-arterial measurements, while RLVW was already significantly lower (-17.7%, P<0.05) in SHRSP-1(F344) in response to a normal-salt diet; a similar significant reduction of LV mass was also observed in consomic rats after high-salt intake (P<0.05 vs. SHRSP). Thus, a major QTL on RNO1 was confirmed with significant impact on LV mass in the hypertensive background of SHRSP.

Usefulness of desirable lifestyle factors to attenuate the risk of heart failure among offspring whose parents had myocardial infarction before age 55 years

Heart failure (HF) is one of the leading causes of hospitalization and death in the United States and throughout Europe. Although a higher risk for HF with antecedent myocardial infarction (MI) has been reported in offspring whose parents had MIs before age 55 years, it is unclear whether adherence to healthful behaviors can mitigate that risk. The aim of the present study was therefore to prospectively examine if adherence to healthy weight, regular exercise, moderate alcohol consumption, and abstinence from smoking can attenuate such increased HF risk. Information on parental history of MI and lifestyle factors was collected using questionnaires. Subjects adhering to ≥3 healthy lifestyle factors were classified as having good versus poor lifestyle scores. Incident HF was assessed via yearly follow-up questionnaires and validated in a subsample. During an average follow up of 21.7 ± 6.5 years, 1,323 new HF cases (6.6%), of which 190 (14.4%) were preceded by MI, occurred. Compared to subjects with good lifestyle scores and no parental histories of premature MI, multivariate adjusted hazard ratios for incident HF with antecedent MI were 3.21 (95% confidence interval 1.74 to 5.91) for subjects with good lifestyle score and parental histories of premature MI, 1.52 (95% confidence interval 1.12 to 2.07) for those with poor lifestyle score and no parental histories of premature MI, and 4.60 (95% confidence interval 2.55 to 8.30) for those with poor lifestyle scores and parental histories of premature MI. In conclusion, our data suggest that even in subjects at higher risk for HF because of genetic predisposition, adherence to healthful lifestyle factors may attenuate such an elevated HF risk.

A follow-up study for left ventricular mass on chromosome 12p11 identifies potential candidate genes

Background

Left ventricular mass (LVM) is an important risk factor for cardiovascular disease. Previously we found evidence for linkage to chromosome 12p11 in Dominican families, with a significant increase in a subset of families with high average waist circumference (WC). In the present study, we use association analysis to further study the genetic effect on LVM.

Methods

Association analysis with LVM was done in the one LOD critical region of the linkage peak in an independent sample of 897 Caribbean Hispanics. Genotype data were available on 7085 SNPs from 23 to 53 MB on chromosome 12p11. Adjustment was made for vascular risk factors and population substructure using an additive genetic model. Subset analysis by WC was performed to test for a difference in genetic effects between the high and low WC subsets.

Results

In the overall analysis, the most significant association was found to rs10743465, downstream of the SOX5 gene (p = 1.27E-05). Also, 19 additional SNPs had nominal p < 0.001. In the subset analysis, the most significant difference in genetic effect between those with high and low WC occurred with rs1157480 (p = 1.37E-04 for the difference in β coefficients), located upstream of TMTC1. Twelve additional SNPs in or near 6 genes had p < 0.001.

Conclusions

The current study supports previously identified evidence by linkage for a genetic effect on LVM on chromosome 12p11 using association analysis in population-based Caribbean Hispanic cohort. SOX5 may play an important role in the regulation of LVM. An interaction of TMTC1 with abdominal obesity may contribute to phenotypic variation of LVM.

Genetic variants associated with cardiac structure and function: a meta-analysis and replication of genome-wide association data

CONTEXT

Echocardiographic measures of left ventricular (LV) structure and function are heritable phenotypes of cardiovascular disease.

OBJECTIVE

To identify common genetic variants associated with cardiac structure and function by conducting a meta-analysis of genome-wide association data in 5 population-based cohort studies (stage 1) with replication (stage 2) in 2 other community-based samples.

DESIGN, SETTING, AND PARTICIPANTS

Within each of 5 community-based cohorts comprising the EchoGen consortium (stage 1; n = 12 612 individuals of European ancestry; 55% women, aged 26-95 years; examinations between 1978-2008), we estimated the association between approximately 2.5 million single-nucleotide polymorphisms (SNPs; imputed to the HapMap CEU panel) and echocardiographic traits. In stage 2, SNPs significantly associated with traits in stage 1 were tested for association in 2 other cohorts (n = 4094 people of European ancestry). Using a prespecified P value threshold of 5 x 10(-7) to indicate genome-wide significance, we performed an inverse variance-weighted fixed-effects meta-analysis of genome-wide association data from each cohort.

MAIN OUTCOME MEASURES

Echocardiographic traits: LV mass, internal dimensions, wall thickness, systolic dysfunction, aortic root, and left atrial size.

RESULTS

In stage 1, 16 genetic loci were associated with 5 echocardiographic traits: 1 each with LV internal dimensions and systolic dysfunction, 3 each with LV mass and wall thickness, and 8 with aortic root size. In stage 2, 5 loci replicated (6q22 locus associated with LV diastolic dimensions, explaining <1% of trait variance; 5q23, 12p12, 12q14, and 17p13 associated with aortic root size, explaining 1%-3% of trait variance).

CONCLUSIONS

We identified 5 genetic loci harboring common variants that were associated with variation in LV diastolic dimensions and aortic root size, but such findings explained a very small proportion of variance. Further studies are required to replicate these findings, identify the causal variants at or near these loci, characterize their functional significance, and determine whether they are related to overt cardiovascular disease.

Parental history of myocardial infarction and risk of heart failure in male physicians

BACKGROUND

Although heart failure (HF) remains a major public health issue, limited data are available on the utility of parental information on the risk of HF in offspring.

MATERIALS AND METHODS

We prospectively examined the association between parental history of myocardial infarction (MI) and incident HF among 20,187 offspring in the Physicians' Health Study I. Parental history and age at MI was assessed by a questionnaire and a Cox regression was used to estimate relative risks of HF.

RESULTS

After an average follow-up of 19.6 years, 1036 new HF cases were documented. Overall, while a history of early parental MI (before age 55) was associated with a 32% increased risk of HF in offspring compared with subjects whose parent did not have MI, parental MI at older ages was not associated with HF risk. However, the relation between parental history of MI and HF was stronger and mainly observed for HF with antecedent MI. Compared with subjects without parental history of MI, multivariable adjusted hazard ratios (95% CI) for HF with antecedent MI were 3.44 (2.15-5.51), 2.24 (1.20-4.21), 1.26 (0.63-2.51), and 1.37 (0.92-2.03) for parental MI occurred at the age of < 55, 55-59, 60-64, and 65 + y, respectively.

CONCLUSIONS

Our data suggest that parental MI at an early age is a strong and independent predictor of HF with antecedent MI among US male physicians. This information, along with existing tools, may help clinicians identify patients at risk of HF with antecedent MI.

Ability of blood pressure to predict left ventricular hypertrophy in children with primary hypertension

OBJECTIVE

To determine whether casual blood pressure (BP) or ambulatory BP monitoring (ABPM) measurements obtained at the initial visit of a child with confirmed hypertension (HTN) might predict left ventricular hypertrophy (LVH), possibly obviating the need for echocardiography.

STUDY DESIGN

We conducted a cross-sectional study of 184 children aged 3 to 20 years who were referred for initial evaluation of elevated BP at 3 tertiary care centers. Casual BP and various ambulatory BP variables were analyzed to determine their association with LVH, defined after echocardiography by cardiologist diagnosis or a left ventricular mass index equal to or greater than the sex-specific 95th percentile.

RESULTS

A total of 41% of children who had echocardiograms had LVH. Children with LVH were significantly more likely to be non-white and have a higher body mass index z-score. There was no difference in casual systolic or diastolic BP index in children with hypertension who had LVH and children with hypertension without LVH. Children with systolic or diastolic BP loads > or = 50% were no more likely to have LVH than children with loads < 50%.

CONCLUSION

LVH is common in children with newly diagnosed HTN. The initial examination of these children should include echocardiography, because neither the severity of casual BP elevation nor the presence of abnormal ambulatory BP results at initial diagnosis are predictive of LVH.

Genome-wide association of echocardiographic dimensions, brachial artery endothelial function and treadmill exercise responses in the Framingham Heart Study

BACKGROUND

Echocardiographic left ventricular (LV) measurements, exercise responses to standardized treadmill test (ETT) and brachial artery (BA) vascular function are heritable traits that are associated with cardiovascular disease risk. We conducted a genome-wide association study (GWAS) in the community-based Framingham Heart Study.

METHODS

We estimated multivariable-adjusted residuals for quantitative echocardiography, ETT and BA function traits. Echocardiography residuals were averaged across 4 examinations and included LV mass, diastolic and systolic dimensions, wall thickness, fractional shortening, left atrial and aortic root size. ETT measures (single exam) included systolic blood pressure and heart rate responses during exercise stage 2, and at 3 minutes post-exercise. BA measures (single exam) included vessel diameter, flow-mediated dilation (FMD), and baseline and hyperemic flow responses. Generalized estimating equations (GEE), family-based association tests (FBAT) and variance-components linkage were used to relate multivariable-adjusted trait residuals to 70,987 SNPs (Human 100K GeneChip, Affymetrix) restricted to autosomal SNPs with minor allele frequency > or =0.10, genotype call rate > or =0.80, and Hardy-Weinberg equilibrium p > or = 0.001.

RESULTS

We summarize results from 17 traits in up to 1238 related middle-aged to elderly men and women. Results of all association and linkage analyses are web-posted at http://ncbi.nlm.nih.gov/projects/gap/cgi-bin/study.cgi?id=phs000007 webcite. We confirmed modest-to-strong heritabilities (estimates 0.30-0.52) for several Echo, ETT and BA function traits. Overall, p < 10(-5) in either GEE or FBAT models were observed for 21 SNPs (nine for echocardiography, eleven for ETT and one for BA function). The top SNPs associated were (GEE results): LV diastolic dimension, rs1379659 (SLIT2, p = 1.17*10(-7)); LV systolic dimension, rs10504543 (KCNB2, p = 5.18*10(-6)); LV mass, rs10498091 (p = 5.68*10(-6)); Left atrial size, rs1935881 (FAM5C, p = 6.56*10(-6)); exercise heart rate, rs6847149 (NOLA1, p = 2.74*10(-6)); exercise systolic blood pressure, rs2553268 (WRN, p = 6.3*10(-6)); BA baseline flow, rs3814219 (OBFC1, 9.48*10(-7)), and FMD, rs4148686 (CFTR, p = 1.13*10(-5)). Several SNPs are reasonable biological candidates, with some being related to multiple traits suggesting pleiotropy. The peak LOD score was for LV mass (4.38; chromosome 5); the 1.5 LOD support interval included NRG2.

CONCLUSION

In hypothesis-generating GWAS of echocardiography, ETT and BA vascular function in a moderate-sized community-based sample, we identified several SNPs that are candidates for replication attempts and we provide a web-based GWAS resource for the research community.

Genetic Variations Associated With Echocardiographic Left Ventricular Traits in Hypertensive Blacks

Echocardiographic measures of cardiac target organ damage, including left ventricular mass and relative wall thickness, are powerful predictors of heart disease morbidity and mortality. The aim of this study is to investigate whether single nucleotide polymorphisms in candidate genes for hypertension and heart disease have effects on quantitative measures of hypertensive cardiac target organ damage, independent of their actions on blood pressure levels, in a cohort of hypertensive black sibships. To detect replication of genetic effects across samples, this study took advantage of the affected sibling pair design and created 2 samples, each with 448 unrelated individuals. As part of the Genetic Epidemiology Network of Arteriopathy Study, subjects were screened using 2D echocardiography, and 395 single nucleotide polymorphisms in 80 candidate genes were genotyped. Linear regression was used to test for single nucleotide polymorphisms significantly associated with left ventricular mass index (g/m 2.7 ) or relative wall thickness after adjusting for associated covariates. Significant single nucleotide polymorphisms were subsequently tested for consistent directionality in genotype–phenotype relationships across samples. Three single nucleotide polymorphisms, 1 each in the APOE , SCN7A , and SLC20A1 genes, were significantly associated in both samples with left ventricular mass index and had replicate genotype–phenotype relationships. One in the ADRB1 gene was significantly associated with relative wall thickness with replicate effects in both samples. We identified genetic variation that significantly influences left ventricular traits with replicable effects in a cohort of hypertensive, black siblings.

Screening of the endothelin1 gene (EDN1) in a cohort of patients with essential left ventricular hypertrophy

Our objective was to analyse the role of endothelin1 gene (EDN1) variation in essential left ventricular hypertrophy (LVH). We searched for EDN1 variants in 145 Spanish patients with an essential form of LVH (not secondary to hypertension, aortic stenosis, or any other disease that could explain the hypertrophy). The five EDN1 coding exons and 1.5 kilobases of the promoter region were analysed through single strand conformation analysis and direct sequencing. We found four nucleotide changes: -1224 C/A (promoter), -131 ins/del A (exon 1, 5'-non-translated sequence), A/G in codon 106 (exon 3, silent), and G/T in codon 198 (exon 5, lys198asn). To determine the association between these polymorphisms and cardiac hypertrophy, we compared the genotype frequencies from these 145 patients with 250 healthy controls. We found a higher frequency of patients homozygous for 198 lys (198 KK) (65% vs. 52%; p = 0.01; OR = 1.76) and for -1224 AA (73% vs. 66%; p = 0.19). Homozygotes for -1224 A + 198 K (AA+KK) were significantly more frequent in patients (62% vs. 45%; p = 0.0007; OR = 2.10; 95% CI = 1.35-3.25). The expression of the -1224 C/A and exon 5 K198N variants was analysed with cells in culture. These in vitro studies showed that these variations did not differ in their expression levels. In conclusion, our work has shown that EDN1 variation, and in particular homozygosity for the -1224A/198K haplotype, is associated with the risk of developing cardiac hypertrophy. However, these EDN1 variants do not affect in vitro gene expression.

Adiposity and cardiac dimensions among 9- to 18-year-old youth: the Québec Family Study

The relationship between adiposity and cardiac dimensions were considered in healthy 9- to 18-year-old boys (n=198) and girls (n=154). Indicators of adiposity included the body mass index (BMI), sum of skinfolds (SSF) and trunk-to-extremity ratio (TER). The following left ventricular (LV) dimensions were measured by echocardiography: internal diameter (LVIDd); posterior wall thickness (PWT) and intraventricular septal wall thickness. LV mass (LVM) was estimated. In boys, 11 of 45 correlations were significant. The magnitude of the correlations increased across age groups and most of the correlations were significant in the oldest age group. In girls, 18 of 45 correlations were significant, but there were inconsistent patterns in the magnitude of the correlations across age groups. Correlations between BMI and LVIDd and LVM were highest in youth 13-15 years, whereas other correlations involving the BMI were rather constant across age groups. Correlations involving SSF were significant only in 9-12 and 13-15 year olds. There were no significant correlations involving TER in female subjects. In the total sample of boys, only correlations between the BMI and LV parameters were significant (r=0.14-0.38), except for the relationship between SSF and PWT (r=0.21). The TER was weakly associated with LV parameters. In the total sample of girls, correlations for LV parameters were significant for both the BMI (r=0.20-0.43) and SSF (r=0.18-0.28; except for LVIDd). TER was not significantly related to LV parameters except LVIDd (r=0.16). The findings indicate that the BMI is an important determinant of LV structure.

Transcriptional alterations in the left ventricle of three hypertensive rat models

Left ventricular hypertrophy (LVH) is commonly associated with hypertension and represents an independent cardiovascular risk factor. The aim of this study was to test the hypothesis that the cardiac overload related to hypertension is associated to a specific gene expression pattern independently of genetic background. Gene expression levels were obtained with microarrays for 15,866 transcripts from RNA of left ventricles from 12-wk-old rats of three hypertensive models [spontaneously hypertensive rat (SHR), Lyon hypertensive rat (LH), and heterozygous TGR(mRen2)27 rat] and their respective controls. More than 60% of the detected transcripts displayed significant changes between the three groups of normotensive rats, showing large interstrain variability. Expression data were analyzed with respect to hypertension, LVH, and chromosomal distribution. Only four genes had significantly modified expression in the three hypertensive models among which a single gene, coding for sialyltransferase 7A, was consistently overexpressed. Correlation analysis between expression data and left ventricular mass index (LVMI) over all rats identified a larger set of genes whose expression was continuously related with LVMI, including known genes associated with cardiac remodeling. Positioning the detected transcripts along the chromosomes pointed out high-density regions mostly located within blood pressure and cardiac mass quantitative trait loci. Although our study could not detect a unique reprogramming of cardiac cells involving specific genes at early stage of LVH, it allowed the identification of some genes associated with LVH regardless of genetic background. This study thus provides a set of potentially important genes contained within restricted chromosomal regions involved in cardiovascular diseases.

Single-gene mutations and increased left ventricular wall thickness in the community: the Framingham Heart Study

BACKGROUND

Mutations in sarcomere protein, PRKAG2, LAMP2, alpha-galactosidase A (GLA), and several mitochondrial genes can cause rare familial cardiomyopathies, but their contribution to increased left ventricular wall thickness (LVWT) in the community is unknown.

METHODS AND RESULTS

We studied 1862 unrelated participants (52% women; age, 59+/-9 years) from the community-based Framingham Heart Study who had echocardiograms and provided DNA samples but did not have severe hypertension, aortic prosthesis, or significant aortic stenosis. Eight sarcomere protein genes, 3 storage cardiomyopathy-causing genes, and 27 mitochondrial genes were sequenced in unrelated individuals with increased LVWT (maximum LVWT >13 mm). Fifty eligible participants (9 women) had unexplained increased LVWT. We detected 8 mutations in 9 individuals (2 women); 7 mutations in 5 sarcomere protein genes (MYH7, MYBPC3, TNNT2, TNNI3, MYL3), and 1 GLA mutation. In individuals with increased LVWT, participants with sarcomere protein and storage mutations were clinically indistinguishable from those without mutations.

CONCLUSIONS

In a community-based cohort, about 3% of eligible participants had increased LVWT, of whom 18% had sarcomere protein or lipid storage gene mutations. Increased LVWT in the community is a very heterogeneous condition, which sometimes may arise from single-gene variants in one of a number of genes.

Heritability of left ventricular mass in a large cohort of twins

INTRODUCTION

Left ventricular hypertrophy is recognized as one of the most important independent predictors of adverse cardiovascular outcome. The aetiology of LVH includes a number of well-recognized causes but there is considerable interest in the genetics of cardiac muscle hypertrophy. We used a large prospective twin database in order to establish the heritability of left ventricular mass (LVM).

METHODS

Normotensive twins were prospectively recruited. Demographic data were collected. The LVM was determined using the Penn formulae derived from data collected from echocardiography.

RESULTS

A total of 376 Caucasian twin pairs (182 monozygotic and 194 dizygotic) aged 25-79 years were recruited. All subjects were normotensive with no significant differences in blood pressure (mean blood pressure: monozygotic twins, 132/83 mmHg; dizygotic twins, 131/82 mmHg) or body mass index between the monozygotic and dizygotic twins. The mean LVM for monozygotic twins was 140.9 g, compared with 140.2 g for dizygotic twins. Heritability estimates suggest that the genetic variance of LVM is 0.59 (95% confidence interval, 0.5-0.67). No common shared environmental effects were identified under this model.

CONCLUSION

Our data from the largest set of twin pairs studied to date show that LVM has a sizeable genetic basis that is probably polygenic. This result has important implications for the understanding of normal and abnormal cardiac morphology at the molecular level.

Identification of quantitative trait loci for cardiac hypertrophy in two different strains of the spontaneously hypertensive rat

Cardiac hypertrophy and left ventricular hypertrophy are known to be substantially controlled by genetic factors. As an experimental model, we undertook genome-wide screens for cardiac mass in F2 populations bred from the stroke-prone spontaneously hypertensive rats (SHRSP) and normal spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) of a Japanese colony. Two F2 cohorts were independently produced: F2(SHRSP x WKY) (110 male and 110 female rats) and F2(SHR x WKY) (151 male rats). The ratio of heart weight to body weight (Hw/Bw) was evaluated at 12 months of age in F2(SHRSP x WKY) after salt-loading for 7 months, and at around 15 weeks of age in F2(SHR x WKY) who had been fed a normal rat chow diet. Subsequent to an initial screen with 251 markers in F2(SHRSP x WKY) male progeny, 170 and 161 markers were selected and characterized in F2(SHRSP x WKY) female progeny and F2(SHR x WKY) male progeny, respectively. Markers from four chromosomal regions showed suggestive or significant linkage to Hw/Bw. The strongest and the most consistent linkage was found in the vicinity of D3Mgh16 on rat chromosome (RNO) 3 (a maximal log of the odds score reached 4.0 to 6.6 across the F2 populations studied). In the other three regions on RNO6, RNO10 and RNO13, the degree of linkage was more prominent in either males or females. These data provide solid evidence for a "principal" RNO3 quantitative trait loci regulating Hw/Bw in SHRSP and SHR, and also suggest the possible presence of sexual dimorphism in regard to genetic susceptibility for cardiac hypertrophy.