Heritability of cardiac size: an echocardiographic and electrocardiographic study of monozygotic and dizygotic twins

Cardiac findings in newborn twins

AIMS

To evaluate cardiac findings in newborn twins from the general population and investigate if newborn twins may require systematic evaluation of cardiac parameters.

METHODS

Prospective cohort study of newborns with cardiac evaluation performed during the first month of life. Cardiac findings were compared 1:3 with matched singletons.

RESULTS

We included 412 newborn twins (16% monochorionic; 50% boys) and 1236 singletons. Comparing cardiac findings showed twins had an increased prevalence of non-severe structural heart disease (most common: ventricular septal defects in both groups), thinner left ventricular posterior wall in diastole (LVPWd; 1.82 vs. 1.87 mm, p = 0.02), smaller diameter of the left atrium (10.6 vs. 11.1 mm, p = 0.04), higher heart rate (148 vs. 144 bpm, p = 0.04), more left-shifted QRS axis (106 vs. 111°, p < 0.001), and lower maximum R-wave amplitude in V1 (927 vs. 1015 μV, p = 0.02) compared to singletons. After multifactorial adjustment for potential confounders, the effect of twinning on cardiac parameters persisted only for LVPWd (p < 0.05).

CONCLUSION

Despite contemporary surveillance, we found an increased prevalence of non-severe structural heart disease in a population-based cohort of newborn twins. However, the effect of twinning on cardiac parameters was modest and generally did not persist after correction for likely confounding factors.

Left Ventricular Adaptation to Exercise Training via Magnetic Resonance Imaging: Studies of Twin Responses to Understand Exercise THerapy

PURPOSE

Changes in left ventricular mass (LVM) and end-diastolic volume (EDV) in response to exercise training are important determinants of functional capacity in health and disease, but the impact of different exercise modalities remains unclear.

METHODS

Using a randomized crossover design we studied the impact of resistance (RES) and endurance (END) training using cardiac magnetic resonance imaging in previously untrained monozygotic (MZ) and dizygotic (DZ) twin pairs (n = 72; 22 MZ pairs, 14 DZ same-sex pairs; 26.1 ± 5.4 yr). Twins, as pairs, undertook 3 months of RES and 3 months of END training (order randomized), separated by a 3-month washout.

RESULTS

Group results revealed that END increased LVM (P < 0.001) and EDV (P = 0.007), whereas RES did not (P > 0.05). A higher proportion of individuals responded to END than RES for LVM (72% vs 38%, P < 0.001) and EDV (67% vs 40%, P = 0.003). Baseline cross-sectional intraclass correlations were higher for MZ than DZ twin pairs for all variables (e.g., LVM heritability = 0.42), but no significant correlations were apparent between pairs for change in any variable in response to either RES or END (P > 0.05).

CONCLUSIONS

Our findings indicate that cardiac adaptation in response to exercise is modality-specific and that low responders to one mode of exercise can be high responders to an alternative. Heritability estimates based on cross-sectional data, which suggested a genetic contribution to LVM, do not accord with estimates based on training effects, which indicated limited genetic impact on adaptation in this 3-month study of exercise training. This study has implications for understanding the physiological and health impacts of typically used exercise modalities on cardiac adaptation in previously untrained individuals.

Genetics of Cardiomyopathy: Clinical and Mechanistic Implications for Heart Failure

Genetic cardiomyopathies are an important cause of sudden cardiac death across all age groups. Genetic testing in heart failure clinics is useful for family screening and providing individual prognostic insight. Obtaining a family history of at least three generations, including the creation of a pedigree, is recommended for all patients with primary cardiomyopathy. Additionally, when appropriate, consultation with a genetic counsellor can aid in the success of a genetic evaluation. Clinical screening should be performed on all first-degree relatives of patients with genetic cardiomyopathy.

Genetics has played an important role in the understanding of different cardiomyopathies, and the field of heart failure (HF) genetics is progressing rapidly. Much research has also focused on distinguishing markers of risk in patients with cardiomyopathy using genetic testing. While these efforts currently remain incomplete, new genomic technologies and analytical strategies provide promising opportunities to further explore the genetic architecture of cardiomyopathies, afford insight into the early manifestations of cardiomyopathy, and help define the molecular pathophysiological basis for cardiac remodeling. Cardiovascular physicians should be fully aware of the utility and potential pitfalls of incorporating genetic test results into pre-emptive treatment strategies for patients in the preliminary stages of HF. Future work will need to be directed towards elucidating the biological mechanisms of both rare and common gene variants and environmental determinants of plasticity in the genotype-phenotype relationship. This future research should aim to further our ability to identify, diagnose, and treat disorders that cause HF and sudden cardiac death in young patients, as well as prioritize improving our ability to stratify the risk for these patients prior to the onset of the more severe consequences of their disease.

Heritability of Cardiothoracic Ratio and Aortic Arch Calcification in Twins

Background and Objectives: Aortic arch calcification (AoAC) is associated with a variety of cardiovascular complications. The measurement and grading of AoAC using posteroanterior (PA) chest X-rays are well established. The cardiothoracic ratio (CTR) can be simultaneously measured with PA chest X-rays and used as an index of cardiomegaly. The genetic and environmental contributions to the degree of the AoAC and CTR are not well understood. The purpose of this study was to investigate the effect of genetics and environmental factors on the AoAC and CTR. Materials and Methods: A total of 684 twins from the South Korean twin registry (261 monozygotic, MZ and 81 dizygotic, DZ pairs; mean age 38.6 ± 7.9 years, male/female = 264/420) underwent PA chest X-rays. Cardiovascular risk factors and anthropometric data were also collected. The AoAC and CTR were measured and graded using a standardized method. A structural equation method was used to calculate the proportion of variance explained by genetic and environmental factors behind AoAC and CTR. Results: The within-pair differences were low regarding the grade of AoAC, with only a few twin pairs showing large intra-pair differences. We found that the thoracic width showed high heritability (0.67, 95% CI: 0.59–0.73, p = 1). Moderate heritability was detected regarding cardiac width (0.54, 95% CI: 0.45–0.62, p = 0.572) and CTR (0.54, 95% CI: 0.44–0.62, p = 0.701). Conclusions: The heritable component was significant regarding thoracic width, cardiac width, and the CTR.

Genetic approaches toward understanding the individual variation in cardiac structure, function and responses to exercise training

Cardiovascular disease (CVD) accounts for approximately 30% of all deaths worldwide and its prevalence is constantly increasing despite advancements in medical treatments. Cardiac remodeling and dysfunction are independent risk factors for CVD. Recent studies have demonstrated that cardiac structure and function are genetically influenced, suggesting that understanding the genetic basis for cardiac structure and function could provide new insights into developing novel therapeutic targets for CVD. Regular exercise has long been considered a robust non-therapeutic method of treating or preventing CVD. However, recent studies also indicate that there is inter-individual variation in response to exercise. Nevertheless, the genetic basis for cardiac structure and function as well as their responses to exercise training have yet to be fully elucidated. Therefore, this review summarizes accumulated evidence supporting the genetic contribution to these traits, including findings from population-based studies and unbiased large genomic-scale studies in humans.

Muscle health and performance in monozygotic twins with 30 years of discordant exercise habits

INTRODUCTION

Physical health and function depend upon both genetic inheritance and environmental factors (e.g., exercise training).

PURPOSE

To enhance the understanding of heritability/adaptability, we explored the skeletal muscle health and physiological performance of monozygotic (MZ) twins with > 30 years of chronic endurance training vs. no specific/consistent exercise.

METHODS

One pair of male MZ twins (age = 52 years; Trained Twin, TT; Untrained Twin, UT) underwent analyses of: (1) anthropometric characteristics and blood profiles, (2) markers of cardiovascular and pulmonary health, and (3) skeletal muscle size, strength, and power and molecular markers of muscle health.

RESULTS

This case study represents the most comprehensive physiological comparison of MZ twins with this length and magnitude of differing exercise history. TT exhibited: (1) lower body mass, body fat%, resting heart rate, blood pressure, cholesterol, triglycerides, and plasma glucose, (2) greater relative cycling power, anaerobic endurance, and aerobic capacity (VO₂max), but lower muscle size/strength and poorer muscle quality, (3) more MHC I (slow-twitch) and fewer MHC IIa (fast-twitch) fibers, (4) greater AMPK protein expression, and (5) greater PAX7, IGF1Ec, IGF1Ea, and FN14 mRNA expression than UT.

CONCLUSIONS

Several measured differences are the largest reported between MZ twins (TT expressed 55% more MHC I fibers, 12.4 ml/kg/min greater VO₂max, and 8.6% lower body fat% vs. UT). These data collectively (a) support utilizing chronic endurance training to improve body composition and cardiovascular health and (b) suggest the cardiovascular and skeletal muscle systems exhibit greater plasticity than previously thought, further highlighting the importance of studying MZ twins with large (long-term) differences in exposomes.

Exercise-induced arterial hypertension - an independent factor for hypertrophy and a ticking clock for cardiac fatigue or atrial fibrillation in athletes?

Background : Exercise-induced arterial hypertension (EIAH) leads to myocardial hypertrophy and is associated with a poor prognosis. EIAH might be related to the "cardiac fatigue" caused by endurance training. The goal of this study was to examine whether there is any relationship between EIAH and left ventricular hypertrophy in Ironman-triathletes.

METHODS

We used echocardiography and spiroergometry to determine the left ventricular mass (LVM), the aerobic/anaerobic thresholds and the steady-state blood pressure of 51 healthy male triathletes. The main inclusion criterion was the participation in at least one middle or long distance triathlon.

RESULTS

When comparing triathletes with LVM <220g  and athletes with LVM >220g there was a significant difference between blood pressure values (BP) at the anaerobic threshold (185.2± 21.5 mmHg vs. 198.8 ±22.3 mmHg, p=0.037). The spiroergometric results were: maximum oxygen uptake (relative VO 2max) 57.3 ±7.5ml/min/kg vs. 59.8±9.5ml/min/kg (p=ns). Cut-point analysis for the relationship of BP >170 mmHg at the aerobic threshold and the probability of LVM >220g showed a sensitivity of 95.8%, a specificity of 33.3%, with a positive predictive value of 56.8 %, a good negative predictive value of 90%. The probability of LVM >220g increased with higher BP during exercise (OR: 1.027, 95% CI 1.002-1.052, p= 0.034) or with higher training volume (OR: 1.23, 95% CI 1.04 -1.47, p = 0.019). Echocardiography showed predominantly concentric remodelling, followed by concentric hypertrophy.

CONCLUSION

Significant left ventricular hypertrophy with LVM >220g is associated with higher arterial blood pressure at the aerobic or anaerobic threshold. The endurance athletes with EIAH may require a therapeutic intervention to at least prevent extensive stiffening of the heart muscle and exercise-induced cardiac fatigue.

Genetic profiling for risk reduction in human cardiovascular disease

Cardiovascular disease is a major health concern affecting over 80,000,000 people in the U.S. alone. Heart failure, cardiomyopathy, heart rhythm disorders, atherosclerosis and aneurysm formation have significant heritable contribution. Supported by familial aggregation and twin studies, these cardiovascular diseases are influenced by genetic variation. Family-based linkage studies and population-based genome-wide association studies (GWAS) have each identified genes and variants important for the pathogenesis of cardiovascular disease. The advent of next generation sequencing has ushered in a new era in the genetic diagnosis of cardiovascular disease, and this is especially evident when considering cardiomyopathy, a leading cause of heart failure. Cardiomyopathy is a genetically heterogeneous disorder characterized by morphologically abnormal heart with abnormal function. Genetic testing for cardiomyopathy employs gene panels, and these panels assess more than 50 genes simultaneously. Despite the large size of these panels, the sensitivity for detecting the primary genetic defect is still only approximately 50%. Recently, there has been a shift towards applying broader exome and/or genome sequencing to interrogate more of the genome to provide a genetic diagnosis for cardiomyopathy. Genetic mutations in cardiomyopathy offer the capacity to predict clinical outcome, including arrhythmia risk, and genetic diagnosis often provides an early window in which to institute therapy. This discussion is an overview as to how genomic data is shaping the current understanding and treatment of cardiovascular disease.

Lack of exercise is a major cause of chronic diseases

Chronic diseases are major killers in the modern era. Physical inactivity is a primary cause of most chronic diseases. The initial third of the article considers: activity and prevention definitions; historical evidence showing physical inactivity is detrimental to health and normal organ functional capacities; cause versus treatment; physical activity and inactivity mechanisms differ; gene-environment interaction (including aerobic training adaptations, personalized medicine, and co-twin physical activity); and specificity of adaptations to type of training. Next, physical activity/exercise is examined as primary prevention against 35 chronic conditions [accelerated biological aging/premature death, low cardiorespiratory fitness (VO2max), sarcopenia, metabolic syndrome, obesity, insulin resistance, prediabetes, type 2 diabetes, nonalcoholic fatty liver disease, coronary heart disease, peripheral artery disease, hypertension, stroke, congestive heart failure, endothelial dysfunction, arterial dyslipidemia, hemostasis, deep vein thrombosis, cognitive dysfunction, depression and anxiety, osteoporosis, osteoarthritis, balance, bone fracture/falls, rheumatoid arthritis, colon cancer, breast cancer, endometrial cancer, gestational diabetes, pre-eclampsia, polycystic ovary syndrome, erectile dysfunction, pain, diverticulitis, constipation, and gallbladder diseases]. The article ends with consideration of deterioration of risk factors in longer-term sedentary groups; clinical consequences of inactive childhood/adolescence; and public policy. In summary, the body rapidly maladapts to insufficient physical activity, and if continued, results in substantial decreases in both total and quality years of life. Taken together, conclusive evidence exists that physical inactivity is one important cause of most chronic diseases. In addition, physical activity primarily prevents, or delays, chronic diseases, implying that chronic disease need not be an inevitable outcome during life.

Family history of cardiovascular disease and offspring echocardiographic left ventricular structure and function: the Asklepios Study

BACKGROUND

Moderate to small heritability has been observed for left ventricular (LV) structure and function in genetic epidemiology and genomewide association studies. The aim of this study was to explore whether this would be mirrored in an independent association between LV structure and function and a family history (FH) of cardiovascular disease (CVD) in a large population of middle-aged adults.

METHODS

Subjects enrolled in the Asklepios Study, a population-based sample of 2,524 male and female volunteers, aged 35 to 55 years, free of overt CVD at baseline, were studied. LV structure and function were assessed using transthoracic echocardiography (by a single sonographer). FH data spanning 4 generations were acquired using a questionnaire.

RESULTS

In unadjusted analyses, only small effects of FH of CVD on LV structure (relative wall thickness, P = .042; interventricular septal thickness, P = .002; LV mass, P = .038; allometrically adjusted LV mass, P = .014) and diastolic function (mitral annular e', P = .02) were observed. After adjusting for the more adverse risk factor profile associated with FH, no significant associations persisted. These results did not appreciably change using a more extended definition of FH of CVD or FH of hypertension.

CONCLUSIONS

A positive FH for CVD was associated with differences in offspring cardiac structure and function, largely mediated by (but not independent from) a more adverse risk profile in those subjects with positive FH.

Variant on chromosome 9p is associated with left ventricular mass: results from two cohorts of essential hypertensive individuals

OBJECTIVES

It is well known that among hypertensive patients, an increased left ventricular mass (LVM) is a powerful predictor of cardiovascular morbidity and mortality. However, the mechanisms underlying LVM in hypertension are not completely understood, as the absolute value of blood pressure and other risk factors associated do not predict alone a definite LVM progression. Recently, the 9p21 chromosomal region has been consistently associated with coronary heart disease.

METHODS AND RESULTS

We examined the association of 384 single nucleotide polymorphisms (SNPs) in the short arm of chromosome 9 with LVM in 821 hypertensive individuals from northern Italy. We identified a SNP (rs894379) in the intronic region of the centlein, centrosomal protein (CNTLN) gene on chromosome 9p22, whose minor allele G is associated with an increased LVM. We performed a follow-up validation analysis for the top SNP in 1038 hypertensive individuals from southern Italy. We then combined the results and found a nominal association for rs894379 (β  =  2.46, P  =  0.0026).

CONCLUSION

We describe a new variant associated with echocardiography LVM. This result, though it needs to be further investigated, may improve our understanding of the genetic determination of this prognostically relevant trait.

Elements of 'missing heritability'

PURPOSE OF REVIEW

To discuss the basis of 'missing heritability', which has emerged as an enigma in the post-genome-wide association studies (GWAS) era.

RECENT FINDINGS

Alleles identified through GWAS account for a relatively small fraction of heritability of the complex phenotypes. Accordingly, a significant part of heritability of the complex traits remains unaccounted for ('missing heritability'). Recent findings offer several explanations, including overestimation of heritability of the complex traits and underestimation of the effects of alleles identified through GWAS. In addition, yet-to-be identified common as well as rare alleles might in part explain the 'missing heritability'. Moreover, gene-gene (epistasis) and gene-environmental interactions might explain another fraction of heritability of complex traits. Moreover, transgenerational epigenetic changes, regulated in part by microRNAs, might also contribute to the 'missing heritability'.

SUMMARY

The new findings suggest a multifarious nature of the 'missing heritability'. The findings de-emphasize the focus on delineating the basis of 'missing heritability' and shift the focus to elucidation of the molecular mechanisms by which genomic and genetic factors govern the pathogenesis of the complex phenotypes.

Medical DNA sequencing

PURPOSE OF REVIEW

To discuss implications of information garnered through whole-genome and exome sequencing in the practice of cardiovascular medicine.

RECENT FINDINGS

Whole-genome and exome sequencing unveils medical information embedded in individual genomes and exomes, which could be incorporated into the practice of medicine for diagnostic and therapeutic gains. The human, however, has considerable genetic diversity, as each genome encompasses about 4 million DNA sequence variants (DSVs). The challenging task is to identify the variants that have clinical implications. DSVs exert a continuum of effect sizes on the phenotype that ranges from negligible to large. From a clinical perspective, selected categories, in order of their significance, are disease-causing, likely disease-causing, disease-associated, biologically functional but unknown clinical significance, and unknown functional and clinical significance variants. The frequency of DSVs in the genome also follows a gradient from rare for the disease-causing variants to common for variants with unknown clinical and biological significance. A subset of DSVs might have implications in accurate and preclinical diagnosis, prognostication and individualization of therapy. Clinical phenotypes, however, are too complex to be determined solely by a single DSV. Even in the case of disease-causing variants, the severity of the disease is determined by multiple additional genetic and nongenetic factors.

SUMMARY

Medical DNA sequencing is expected to retool clinicians with the information content of DSVs. DSVs with large effect sizes are likely to offer clinical utility in early and preclinical diagnosis, prognostication and individualization of therapy.

Strategic approaches to unraveling genetic causes of cardiovascular diseases

DNA sequence variants are major components of the "causal field" for virtually all medical phenotypes, whether single gene familial disorders or complex traits without a clear familial aggregation. The causal variants in single gene disorders are necessary and sufficient to impart large effects. In contrast, complex traits are attributable to a much more complicated network of contributory components that in aggregate increase the probability of disease. The conventional approach to identification of the causal variants for single gene disorders is genetic linkage. However, it does not offer sufficient resolution to map the causal genes in small families or sporadic cases. The approach to genetic studies of complex traits entails candidate gene or genome-wide association studies. Genome-wide association studies provide an unbiased survey of the effects of common genetic variants (common disease-common variant hypothesis). Genome-wide association studies have led to identification of a large number of alleles for various cardiovascular diseases. However, common alleles account for a relatively small fraction of the total heritability of the traits. Accordingly, the focus has shifted toward identification of rare variants that might impart larger effect sizes (rare variant-common disease hypothesis). This shift is made feasible by recent advances in massively parallel DNA sequencing platforms, which afford the opportunity to identify virtually all common as well as rare alleles in individuals. In this review, we discuss various strategies that are used to delineate the genetic contribution to medically important cardiovascular phenotypes, emphasizing the utility of the new deep sequencing approaches.

Heritability of left ventricular structure and function in Caucasian families

AIMS

The aim of this study was to investigate the heritability as well as genetic and environmental correlations of left ventricular (LV) structural and functional traits in complex pedigrees of a Caucasian population.

METHODS AND RESULTS

We randomly recruited 459 white European subjects from 52 families (50% women; mean age 45 years). LV structure was measured by M-mode and 2D echocardiography and LV function was measured by conventional Doppler and tissue Doppler imaging (TDI). Other measurements included blood pressure, anthropometric, and biochemical measurements. We estimated the heritability of LV traits while adjusting for covariables, including sex, age, body height and weight, systolic and diastolic blood pressures, and heart rate. With full adjustment, heritability of LV mass was 0.23 (P= 0.025). The TDI-derived mitral annular velocities Ea and Aa showed moderate heritability (h(2)= 0.36 and 0.53, respectively), whereas the mitral inflow A peak had weak heritability (h(2) = 0.25) and the E peak was not heritable (h(2) = 0.11). We partitioned the total phenotypic correlation when it reached significance, into a genetic and an environmental component. The genetic correlations were 0.61 between the E and Ea peaks and 0.90 between the A and Aa peaks.

CONCLUSION

Our study demonstrated moderate heritability for LV mass as well as the mitral annular Ea and Aa peaks. We also found significant genetic correlations between the E and Ea peaks and between the A and Aa peaks. Our current findings support the ongoing research to map and detect genetic variants that contribute to the variation in LV mass and other LV structural and functional phenotypes.

Natriuretic peptides and the genomics of left-ventricular hypertrophy

Left-ventricular hypertrophy (LVH) is one of the strongest independent predictors of cardiovascular morbidity and mortality in the general population. Although hypertension and obesity are well-established, independent risk factors for the development of LVH, they explain less than 25% to 50% of the variance of left ventricular mass (LVM) in humans. A substantial body of evidence suggests that there is a genetic basis to the observed inter-individual variability in the susceptibility to the development of LVH. Given the continuous relationship between LVM and cardiovascular morbidity and mortality, elucidating the genetic determinants of inter-individual differences in the susceptibility to LVH is of considerable public health importance. It promises the opportunity to identify high-risk individuals for targeted intervention and may identify novel therapeutic targets for improved prevention and treatment strategies.

Influence of angiotensin-converting enzyme gene polymorphism on development of athlete's heart

BACKGROUND AND HYPOTHESIS

Genetic influence on development of athlete's heart is uncertain. This study investigated whether angiotensin-converting enzyme (ACE) gene polymorphism influenced development of athlete's heart.

METHODS

Forty-three participants in a 100-km ultramarathon were classified on the basis of ACE gene polymorphism into a deletion group (n = 26) and an insertion group (n = 17). Echocardiograms were recorded to determine left ventricular end-diastolic and end-systolic diameters, interventricular septal thickness, left ventricular posterior wall thickness, left ventricular mass, and ejection fraction.

RESULTS

Left ventricular end-diastolic diameter (65.5 +/- 4.0 mm) and left ventricular mass (369.5 +/- 73.9 g) were significantly larger in the subjects with deletion than in those with insertion (57.4 +/- 4.2 mm, 306.5 +/- 93.7 g). However, no significant differences in the other parameters were noted.

CONCLUSIONS

In long-distance runners, ACE gene polymorphism of the D/D and D/I genotypes has a stronger influence on left ventricular hypertrophy than polymorphism of the I/I genotype.

Genetische Determinanten des EKG

Schon bald nach der Erfindung des EKG wurden die hohen Heritabilitäten vieler EKG-Parameter erkannt. Seit etwa einer Dekade wird intensiv an der Aufklärung zugrunde liegender genetischer Varianten gearbeitet, mit der Einführung genomweiter Assoziationsstudien steht dafür nun auch eine adäquate Methode zur Verfügung. Die molekulare Identifizierung und Charakterisierung bisher unbekannter herzrhythmusassoziierter Gene und Genvarianten verspricht nicht nur eine Vertiefung unseres Verständnisses der kardialen Elektrophysiologie, sondern auch eine Option auf bessere therapeutische und präventive Strategien für Arrhythmien und den plötzlichen Herztod.

Left ventricular geometric patterns in the Jackson cohort of the Atherosclerotic Risk in Communities (ARIC) Study: clinical correlates and influences on systolic and diastolic dysfunction

BACKGROUND

The distribution and determinants of left ventricular (LV) geometric patterns and their relation to LV function in African Americans is not well described despite higher rates of LV hypertrophy and cardiovascular mortality reported in this group.

PURPOSE

This study investigates the distribution and clinical correlates of LV geometric patterns and how these patterns relate to function in a population-based African American cohort.

METHODS

The study population included participants in the Jackson cohort of ARIC, who underwent echocardiograms between 1993 and 1995. We defined 4 geometric patterns (normal geometry, concentric remodeling [CR], eccentric hypertrophy [EH], and concentric hypertrophy [CH]) according to LV mass index and relative wall thickness. Multiple logistic regression was used to assess the association of geometric patterns to systolic dysfunction and diastolic dysfunction, adjusting for traditional coronary risk factors.

RESULTS

There were 1849 participants in the study population (mean age 59 years, 65% women). Concentric remodeling and CH were highly prevalent. Concentric hypertrophy and EH groups had the highest rates of hypertension, obesity, and diabetes mellitus. Compared to the normal geometric pattern, EH was related to systolic dysfunction (OR 24.27, CI 6.71-87.80), and CH was related to diastolic dysfunction 1.58 (1.04-2.39). Concentric remodeling was not related to systolic or diastolic dysfunction.

CONCLUSION

In this large middle-aged African American cohort, CR and CH are prevalent. Hypertension, diabetes mellitus, and obesity are associated with both CH and EH. Concentric hypertrophy is strongly associated with diastolic dysfunction; EH is strongly associated with systolic dysfunction. Concentric remodeling, however, is not related to either systolic or diastolic dysfunction.

The genetics of left ventricular remodeling in competitive athletes

Left ventricular (LV) remodeling in competitive athletes is a complex phenomenon, in which genetic and environmental determinants are implicated. In recent years, several investigations have demonstrated an association between LV remodeling and the angiotensin-converting enzyme (ACE I/D) and/or angiotensinogen (AGT M/T) polymorphism, with athletes with the DD and/or TT alleles, respectively, showing the greatest increase in LV mass, independent from other determinants. However, the impact of the known genetic determinants on LV remodeling is at present incomplete, and comparative assessment of the genetic and environmental factors, such as the type and intensity of athletic conditioning, suggests that genetic determinants may explain up to one-quarter of the overall variability of LV dimensions. A better understanding of genetic factors may provide an insight into the pathways producing physiological cardiac remodeling, and will be important in understanding the intrinsic nature and clinical significance of the extreme LV morphologic changes observed in highly trained and elite athletes.

Changes over time in echocardiographic measurements in young Standardbred racehorses undergoing training and racing and association with racing performance

OBJECTIVE

To evaluate changes over time in echocardiographic measurements in young Standardbred racehorses undergoing training and racing and determine whether there was any relationship between cardiac dimensions and racing performance.

DESIGN

Longitudinal observational study.

ANIMALS

103 horses.

PROCEDURE

2-dimensional and M-mode echocardiography was performed 4 times at 6-month intervals.

RESULTS

Significant cardiac enlargement took place during the study period as indicated by increases in left ventricular internal diameter in diastole (LVIDd), estimated left ventricular muscle mass (LV mass), and mean wall thickness attributable to eccentric left ventricular hypertrophy. Estimated body weight was positively correlated with left ventricular size, and males had significantly larger LVIDd and LV mass than did females. Horses that were racing regularly had larger LVIDd and LV mass than did unraced horses. A significant relationship between left ventricular size and racing performance was observed. The relationship was strongest at the time of the fourth examination.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that age must be taken into account when interpreting results of echocardiography in young Standardbred racehorses because significant cardiac enlargement takes place with age and training. A larger heart was found in horses that were racing, and size of the heart was correlated with athletic performance of the horse.

Physiological upper limits of ventricular cavity size in highly trained adolescent athletes

OBJECTIVES

To define physiological upper limits of left ventricular (LV) cavity size in trained adolescent athletes.

DESIGN

Cross sectional echocardiographic study.

SETTING

British national sports training grounds and Olympic Medical Institute.

SUBJECTS

900 elite adolescent athletes (77% boys) aged 15.7 (1.2) years participating in ball, racket, and endurance sports and 250 healthy controls matched for age, sex, and size.

MAIN OUTCOME MEASURES

LV end diastolic cavity size.

RESULTS

Compared with controls, athletes had a larger LV cavity (50.8 (3.7) v 47.9 (3.5) mm), a difference of 6%. The LV cavity was > 54 mm in 18% athletes, whereas none of the controls had an LV cavity > 54 mm. The LV cavity exceeded predicted sizes in 117 (13%) athletes. Among the athletes with LV dilatation, 78% were boys, LV size ranged from 52-60 mm, and left atrial diameter and LV wall thickness were enlarged. Systolic and diastolic function were normal. None of the athletes in the study had an LV cavity size > 60 mm. LV cavity size correlated with age, sex, heart rate, and body surface area.

CONCLUSION

Highly trained junior athletes usually have only modest increases in LV cavity size. A proportion of trained adolescent athletes have LV cavity size exceeding predicted values but, in absolute terms, LV cavity rarely exceeds 60 mm as in patients with dilated cardiomyopathy. In highly trained adolescent athletes with an LV cavity size > 60 mm and any impairment of systolic or diastolic function, the diagnosis of dilated cardiomyopathy should be considered.

Heritability of left ventricular dimensions and mass in American Indians: The Strong Heart Study

OBJECTIVE

We sought to determine the heritability of left ventricular dimensions and mass in adult American Indians.

METHODS

Echocardiograms were analysed in 1373 American Indian participants, from 445 families, in the Strong Heart Study (SHS) to determine the heritability of left ventricular dimensions and mass. Heritability calculations were performed using variance component analysis in SOLAR, a computer analysis program.

RESULTS

The SHS participants analysed in this study included 1305 relative pairs, predominantly (n = 1077) sib-pairs. After simultaneously adjusting for sex, age and centre, the proportion of the residual phenotypic variance due to additive genetic effects or heritability (h2) of left ventricular mass was 0.27 (SE = 0.08, P < 0.001). Addition of body weight, height, systolic blood pressure, heart rate, medications and diabetes into the polygenic model attenuated the residual h2 of left ventricular mass to 0.17 (SE = 0.09, P < 0.05). The residual h2 for left ventricular end-diastolic chamber diameter (LVID), after simultaneously adjusting for sex, age and centre was 0.36 (SE = 0.08, P < 0.001) for the analysed families. The residual h2 for interventricular septal wall thickness was 0.26 (SE = 0.07), while that of left ventricular posterior wall thickness was 0.19 (SE = 0.08, both P < 0.001). While adjustment for body weight, height, systolic blood pressure, heart rate, medications and diabetes reduced the h2 of LVID to 0.33 (SE = 0.09, P < 0.001), the h2 of septal (0.12, SE = 0.10) and posterior wall thickness (0.09, SE = 0.09) were no longer significant after similar adjustment. The residual h2 for relative wall thickness, a measure of left ventricular geometry, was 0.22 (SE = 0.07, P < 0.001) after adjusting for sex, age and centre, and 0.17 (SE = 0.08, P < 0.05) after additional adjustment for body weight, height, systolic blood pressure, heart rate, medications and diabetes.

CONCLUSIONS

A substantial proportion of the variance of left ventricular dimensions and mass can be explained by heredity, independent of the effects of sex, age, body size, blood pressure, heart rate, medications and diabetes. Identification of genes influencing left ventricular size and geometry may provide mechanistic and therapeutic targets to prevent left ventricular hypertrophy.

ACE gene polymorphism, left ventricular geometry, and mortality in diabetic patients with end-stage renal disease

The objectives of this study were to determine the association between angiotensin converting enzyme (ACE) gene polymorphism and left ventricular (LV) geometry, and to clarify independent effects of ACE genotype on mortality after commencing dialysis in diabetic patients with end-stage renal disease (ESRD). A total of 106 diabetic patients, 71 men and 35 women, 11 type 1 and 95 type 2 diabetic, 57 +/- 12 (mean +/- standard deviation (S.D.)) years of age, who started dialysis were studied. Patients with cardiac diseases and those treated with ACE inhibitors were excluded because of potential effects on LV performance. Echocardiographic examination was performed within +/-2 months of the start of dialysis. Relation between ACE genotype and LV mass index (LVMI) or relative wall thickness (RWT) at onset of dialysis, and impact of ACE genotype on survival after commencing dialysis were evaluated. There were no significant differences in LVMI or RWT in the three ACE genotype groups at onset of dialysis. However, mortality of patients with the ACE-DD genotype was significantly higher than patients with the DI and II genotypes (hazard ratio, 2.318; P=0.043), based on a survival analysis with a mean follow-up duration of 60 months. The higher mortality in patients with the DD genotype was confirmed to be independent of LV hypertrophy and increases in RWT. In diabetic patients with ESRD, ACE genotype has no association with LV mass or RWT at the start of dialysis, but does have an independent impact on patient survival thereafter.

Cardiac remodeling in systemic hypertension

Experimental and clinical studies provide evidence that hypertension is causally related to adverse cardiac structural changes, such as LA enlargement, LV hypertrophy and myocardial fibrosis, and functional changes inclusive of LV systolic and diastolic dysfunction. These changes are induced by both hemodynamic and nonhemodynamic factors. There is accumulating evidence from several small and large clinical trials that various classes of antihypertensive therapy prevent and regress LVH and myocardial fibrosis. Prevention and reversal of LVH are associated with an improvement in cardiac function and with a decline in risk of adverse cardiovascular outcomes. Prevention of LVH should be a priority in subjects with hypertension. In patients with hypertensive heart disease, the components of therapy must comprise optimization of BP and regression of LVH. Future targets of therapy in hypertensive heart disease may include regression of myocardial fibrosis, normalization of LA size, and improvement in LV diastolic function.

Lack of association of the renin-angiotensin system genes polymorphisms and left ventricular hypertrophy in hypertension

OBJECTIVE

The aim of the present study was to determine if there is an association of different gene polymorphisms of renin-angiotensin system and left ventricular hypertrophy (LVH) in patients with essential hypertension (EH) in St Petersburg population.

PATIENTS AND METHODS

We examined 156 patients (the mean age 49+/-8 years) with mild-to-moderate EH recruited from the general population of the outpatient clinic. Left ventricular mass was measured by echocardiography and left ventricular mass index (LVMI) was calculated. Subjects were genotyped for I/D polymorphism of the angiotensin-converting enzyme (ACE) gene, A1166C polymorphism of the AT1 receptor gene, M235T polymorphism of angiotensinogen gene and -6G/A polymorphism of its promoter region.

RESULTS

Genotype distribution of the sample obeyed Hardy-Weinberg equilibrium and was comparable to that reported previously for hypertensive individuals. Groups of patients with II, ID and DD polymorphism of ACE gene did not differ significantly in their LVMI levels. Furthermore, neither ID ACE-gene polymorphism nor ATI-receptor gene and angiotensinogen gene polymorphism was associated with LVH. Additionally, no any significant gene-gene interactions were found to be associated with LVH in the group studied.

CONCLUSIONS

In the light of these observations it seems reasonable to make a preliminary conclusion about lack of association between LVH and distinct polymorphisms of renin-angiotensin system genes in the population studied.

Genetic contribution to the variance in left ventricular mass: the Tecumseh Offspring Study

OBJECTIVE

To estimate the contribution of heredity to the variance in left ventricular mass (LVM), and to ascertain whether genetic factors may interact with non-genetic factors in promoting LVM growth.

SUBJECTS AND SETTING

The study population consisted of 290 healthy parents and 251 healthy children living in Tecumseh, Michigan, USA.

MAIN OUTCOME MEASURE

Correlation of parents' LVM with offspring's LVM adjusting for a number of clinical variables.

METHODS

LVM in parents and offspring was measured with M-mode echocardiography by the same investigators.

RESULTS

Parents unadjusted LVM was unrelated to offspring unadjusted LVM, but after removing the confounding effect of age, sex, anthropometric measurements, systolic blood pressure, plasma insulin and urinary sodium excretion, parent-child correlation for LVM was 0.28 (P = 0.006). The relative contribution of parental-adjusted LVM and of several offspring phenotypic and environmental variables on offspring LVM was evaluated by multivariable regression analysis. When age, gender, anthropometric measurements and systolic blood pressure were accounted for, adjusted LVM of parents explained only 1.6% of the total variance in offspring LVM. However, after inclusion of insulin and urinary sodium in the model heredity explained 7.6% of the total variance in offspring LVM, and its predictive power was second only to that of child's height. Furthermore, an interactive effect of parental LVM with offspring systolic blood pressure was found on child's left ventricular mass.

CONCLUSION

Heredity can explain a small, but definite proportion of the variance in LVM. Higher blood pressure favors the phenotypic expression of the genes that regulate LVM growth.

Effect of the angiotensin II type 2-receptor gene (+1675 G/A) on left ventricular structure in humans

OBJECTIVES

Our study goal was to analyze whether gene variants of angiotensin II type 2-receptor (AT2-R) modulate the effects of angiotensin II on the left ventricle (LV).

BACKGROUND

Experimental data suggest that angiotensin II modifies ventricular growth responses via angiotensin II type 1-receptors (AT1-R) and AT2-R.

METHODS

In 120 white, young male subjects with normal or mildly elevated blood pressure, we assessed plasma angiotensin II and aldosterone concentrations (RIA), 24-h urinary sodium excretion, 24-h ambulatory blood pressure and LV structure (two-dimensional guided M-mode echocardiography). The intronic +1675 G/A polymorphism of the X-chromosomal located AT2-R gene was investigated by single-strand conformational polymorphism analysis and DNA-sequencing.

RESULTS

Hypertensive subjects with the A-allele had a greater LV posterior (11.0 +/- 1.3 vs. 9.9 +/- 1.3 mm, p < 0.001), septal (11.8 +/- 1.4 vs. 10.1 +/- 1.2 mm, p < 0.001) and relative wall thickness (0.44 +/- 0.06 vs. 0.39 +/- 0.06, p < 0.01) as well as LV mass index (138 +/- 23 vs. 120 +/- 13 g/m2, p < 0.001) than those with the G-allele. Confounding factors (i.e., body mass index and surface area, plasma angiotensin II, sodium excretion, systolic and diastolic ambulatory blood pressure) were similar between the two genotypes. In normotensive subjects, relative wall thickness (0.36 +/- 0.05 vs. 0.35 +/- 0.05) and LV mass index (115 +/- 21 vs. 112 +/- 17 g/m2) were nearly identical across the two genotypes, with similar confounding variables.

CONCLUSIONS

Our data indicate that the X-chromosomal located +1675 G/A-polymorphism of the AT2-R gene is associated with LV structure in young male humans with early structural changes of the heart due to arterial hypertension.

Effects of antihypertensive agents on the left ventricle: clinical implications

Hypertensive heart disease (HHD) is characterized by left ventricular hypertrophy (LVH), alterations of cardiac function, and coronary flow abnormalities. LVH is an independent cardiovascular risk factor related to cardiovascular complications in patients with hypertension. Therefore, a decrease in left ventricular mass is a therapeutic goal in these patients. The effect of the different antihypertensive agents on LVH regression has been studied in nearly 500 clinical trials. Most studies conclude that there is regression of LVH after significant decrease in blood pressure with most commonly prescribed antihypertensive agents. However, the ability to regress LVH is different between antihypertensive drug classes. ACE inhibitors and calcium channel antagonists are more potent in reducing left ventricular mass than beta-blockers, with diuretics falling in the intermediate group. Recent data suggest that angiotensin AT(1) receptor antagonists reduce left ventricular mass to a similar extent as ACE inibitors or calcium channel antagonists. Although a large number of studies have established that reversal of LVH decreases the occurrence of adverse cardiovascular events in patients with hypertension, the hypothesis that LVH regression is beneficial has not yet been conclusively proven. On the other hand, the time has come to revisit the current management of HHD simply focused on controlling blood pressure and reducing left ventricular mass. In fact, it is necessary to develop new approaches aimed to repair myocardial structure and protect myocardial perfusion and function and, in doing so, to reduce in a more effective manner, adverse risk associated with HHD. The identification of genes involved in both the process of HHD and the response to therapy may be critical for the development of these new approaches. This article will review briefly the available data on the effects of antihypertensive agents on HHD. In addition, the emerging new concepts on the pharmacology of hypertensive myocardial remodeling and the pharmacogenetic basis of the treatment of HHD will be also considered.

Variants of trophic factors and expression of cardiac hypertrophy in patients with hypertrophic cardiomyopathy

Patients with hypertrophic cardiomyopathy (HCM) exhibit variable expression of left ventricular hypertrophy (LVH), a major determinant of mortality and morbidity, which is partly due to the diversity of causal mutations, genetic background (modifier genes), and probably environmental factors. We determined association of functional variants of tumor necrosis factor (TNF)- alpha, interleukin-6 (IL6), insulin-like growth factor-2 (IGF2), transforming growth factor- beta 1 (TGFB1), and aldosterone synthase (CYP11B2) genes, all previously implicated in cardiac hypertrophy, with the severity of LVH in patients with HCM. Two-dimensional echocardiography was performed and demographic variables were recorded in 142 genetically independent patients. Indices of LVH including interventricular septal thickness (IVST), left ventricular mass index (LVMI), and LVH score were measured/calculated. TNF-alpha-308G/A, IL6-174G/C, IGF2 820G/A, TGFB1-509C/T, and CYP11B2-344T/C genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Genotypes were identified by the presence of specific electrophoretic patterns and their distributions were according to the Hardy-Weinberg equilibrium. Demographic variables were not significantly different among the genotypes. Subjects with the AA genotype of TNF-alpha (n=8) were approximately 13 years younger at the time of clinical diagnosis. Despite a younger age, they had a greater mean LVMI than those with the GG (n=94) or GA (n=33) genotypes (191.8+/-59.5 v 139.1+/-47.3 v 132.1+/-34.3, respectively, P=0.004). TNF-alpha-308G/A genotypes accounted for 6.0% of variability of LVMI (P=0.002). Mean IVST, LVEDD, and LVH score were not significantly different. Variants of IL6, IGF2, TGFB1, and CYP11B2 were not associated with indices of LVH. The uncommon allele of TNF-alpha-308G/A polymorphism, known to produce more TNF- alpha, was associated with greater LVMI and clinical diagnosis at a younger age in patients with HCM. Functional variants of other trophic factors, previously implicated in cardiac hypertrophy, were not associated with the indices of LVH. These results suggest that TNF-alpha is a modifier gene for HCM.

Effects of acute hyperglycaemia on cardiac function: an echocardiographic study of monozygotic twins

BACKGROUND

A major cause of morbidity in type I diabetes is congestive heart failure due predominantly to left ventricular diastolic dysfunction. The mechanism of diastolic dysfunction remains unknown and does not relate to blood pressure, microvascular complications and glycated haemoglobin. Hyperglycaemia is the hallmark of diabetes and is a potential determinant of left ventricular diastolic dysfunction.

OBJECTIVE

To determine whether acute hyperglycaemia can induce changes in left ventricular diastolic function in normal subjects similar to those observed in insulin-dependent diabetes mellitus (IDDM).

DESIGN

Cross-sectional study.

SETTING

London teaching hospital.

SUBJECTS

Sixteen twins from eight identical twin pairs discordant for IDDM (age 18-38 years, five male) were studied; none had a history or evidence of myocardial ischaemia, valvular or primary heart muscle disease, systemic hypertension or nephropathy.

INTERVENTIONS

Non-diabetic twins underwent a hyperglycaemic clamp at 10 mmol/l.

MAIN OUTCOME MEASURES

Doppler echocardiography was performed in basal condition in identical twin pairs discordant for IDDM and repeated in the non-diabetic twins during hyperglycaemia. Blood glucose, insulin and catecholamines were measured at baseline and during hyperglycaemia.

RESULTS

Transmitral Doppler E/A velocity ratio was significantly lower in diabetic than non-diabetic twins at baseline (1.44 (0.38) vs. 1.51 (0.19), P<0.05). Glucose infusion in the non-diabetic twins resulted in an increase in their E/A ratio (1.51 (0.19) vs. 1.82 (0. 47), P<0.05) due to an increase in E velocity (68 (12) to 64.7 (10. 7), P<0.05) and a decrease in the peak A velocity (42.7 (3.85) to 38. 0 (4.1), P<0.05). No significant changes were observed in peak E velocity or isovolumic relaxation time in the non-diabetic twins between baseline and hyperglycaemia.

CONCLUSIONS

The alterations in left ventricular diastolic function induced by acute hyperglycaemia and consequent increase in plasma catecholamines do not mimic those demonstrated in IDDM patients.

Determinants of left ventricular mass in a French male population

The aim of this analysis was to study the determinants of left ventricular mass evaluated by echocardiography. A total of 843 healthy men aged 47-61 years, who had a standard health check-up at the Centre d'Investigations Preventives et Cliniques (IPC Center), were included in the study. None of the subjects were being treated for cardiovascular disease at the time of their visit and each had a standard clinical and biological examination. The answers to a lifestyle questionnaire, weight at 20 years and family history were recorded. All subjects had an echocardiogram to evaluate left ventricular mass. Left ventricular mass values were adjusted for height using the ratio of left ventricular mass to height. Current body mass index, systolic and diastolic blood pressure, brachial circumference, triglycerides and a family history of sudden death were positively associated with this ratio (p < 0.01). Physical activity and tobacco consumption were associated with left ventricular mass. Body mass index at 20 years, variation of body mass index since that age, systolic blood pressure and family history of sudden death explain 21% of the ratio of left ventricular mass/height (body mass index at 20 years: 11.8%; variation of body mass index: 5.1%; systolic blood pressure: 2.3%; and family history of sudden death: 0.4%). The other factors explain only 1.4% of this variance and were not significantly associated with the ratio of left ventricular mass to height. Body mass index at 20 years was the strongest determinant of left ventricular mass, suggesting that left ventricular mass at middle age is in large measure determined much earlier in life. A family history of sudden death before the age of 60 years is also an important determinant of left ventricular mass, independent of obesity. These factors must be taken into account in order to prevent an increase in left ventricular mass.

Genetic aspects of heart failure

Heart failure is a major health problem and is associated with a high mortality and morbidity. Recently, the role of the genetic background in the onset and the development of the disease has been evidenced in both heart failure with and without systolic dysfunction and in familial and non-familial forms of this condition. Preliminary studies suggest that the I/D polymorphism of the Angiotensin Converting Enzyme gene influence the development of left ventricular hypertrophy, a major determinant of heart failure. Familial hypertrophic cardiomyopathy (FHC) is a highly heterogenous autosomal dominant disease. Seven genes have been identified which all encode proteins of the sarcomere or proteins involved in the regulation of contraction. More than one hundred mutations have been evidenced. Modifier genes such as the I/D polymorphism seem to play a role in the expression of the disease. Susceptibility genes have been searched for in sporadic forms of dilated cardiomyopathy and conflicting results have been published with regard to the I/D polymorphism. Finally, familial forms of dilated cardiomyopathy (FDC) are frequent. Various modes of inheritance and phenotypes have been reported and this condition appears genetically highly heterogenous. It has been postulated that the molecular defect involved in FDC is an abnormality in the transmission of contractile force. The analysis of genetic factors that predispose to heart failure looks promising: it should allow better understanding of the underlying mechanisms that promote the progression of the disease, to identify subjects at risk of the disease who would benefit from early medical management and promote the development of pharmacogenetics.

Ambulatory blood pressure monitoring and echocardiography--noninvasive techniques for evaluation of the hypertensive patient

Clinic blood pressure measurements have only limited ability to determine which hypertensive patients are at greatest risk of cardiovascular events. Ambulatory blood pressure monitoring allows for noninvasive measurement of blood pressure throughout the 24-hour period. This may help to clarify discrepancies between blood pressure values obtained in and out of the clinic and confirm the presence of white-coat hypertension, broadly defined as an elevated clinic blood pressure but a normal ambulatory blood pressure. Ambulatory blood pressure values have been shown to have a better relationship to cardiovascular morbidity and mortality and end-organ damage than clinic blood pressure values. Further, patients with white-coat hypertension appear to be at greater risk of cardiovascular morbidity and end-organ damage than a normotensive population, although they are at less overall risk than a hypertensive population. Hypertensive heart disease is characterized by diastolic dysfunction, increased left ventricular mass, and coronary flow abnormalities. Left ventricular hypertrophy increases the risk of coronary heart disease, congestive heart failure, stroke, ventricular arrhythmias, and sudden death. A variety of invasive and noninvasive techniques are described herein that measure left ventricular mass, diastolic function, and coronary blood flow abnormalities. Most antihypertensive treatments promote regression of left ventricular hypertrophy and reversal of diastolic dysfunction, which may decrease symptoms of congestive heart failure and improve survival.

Familial predisposition of left ventricular hypertrophy

OBJECTIVES

The study evaluated the contribution of familial predisposition to the risk of left ventricular hypertrophy (LVH).

BACKGROUND

Left ventricular hypertrophy is a multifactorial condition that serves as an important predictor of cardiovascular mortality. At present it is unclear whether familial predisposition contributes to the manifestation of LVH. Thus, we determined whether siblings of subjects with LVH are at increased risk to present with an elevation of LV mass or an abnormal LV geometry.

METHODS

Echocardiographic and anthropometric measurements were performed in 2,293 individuals who participated in the echocardiographic substudies of population-based MONICA Augsburg surveys. In addition, a total of 319 siblings of survey participants with echocardiographic evidence of LVH were evaluated. The risk of these siblings to present with LVH or abnormal LV geometry was estimated by comparison with 636 subjects matched for gender and age that were selected from the entire echocardiography study base.

RESULTS

Blood pressure, body mass index, age, and gender (i.e., known determinants of LV mass) were comparable in LVH-siblings and the matched comparison group. However, septal and posterior wall thicknesses, relative wall thickness as well as LV mass index were significantly elevated in LVH-siblings (p < 0.001, each) whereas LV dimensions did not differ. Likewise, the prevalence of LVH was raised in LVH-siblings, as was the relative risk of LVH after adjustment for confounders (p < 0.05). More specifically, LVH-siblings displayed increased prevalences of concentric remodeling and concentric LVH (p < 0.05) but not of eccentric LVH.

CONCLUSIONS

Familial predisposition appears to contribute to increased LV wall thickness, to the development of LV hypertrophy and abnormal LV geometry.

Impact of different sports and training on cardiac structure and function

There is overwhelming evidence, particularly from echocardiography, that the heart of competitive athletes may differ from that of nonathletes, matched for age, gender, and body size. A larger left ventricular mass has been shown in athletes performing predominantly dynamic aerobic and anaerobic sports, in athletes engaged in static training, and in players of ball sports. Enlargement of the left ventricular internal diameter was most pronounced and reached about 10% in athletes performing predominantly dynamic sports; mainly strength training athletes had a lesser increase of the internal dimension, which was limited to 2.5%. Also the left ventricular wall appeared to be thickened in all types of athletes compared with controls. In sports with high dynamic and low static demands, wall thickness was proportionate or slightly disproportionate to the size of the internal diameter so that relative wall thickness was not different from controls or slightly increased (predominantly eccentric hypertrophy). In strength athletes, the disproportionate increase of wall thickness averaged about 12% (predominantly concentric hypertrophy). In sports with high dynamic and high static demands and requiring prolonged training, such as cycling, the increases of absolute and relative wall thickness reached 29% and 19% and were more pronounced than in runners (mixed hypertrophy). A plausible interpretation of these results is that the development of so-called eccentric or concentric left ventricular hypertrophy according to the type of sports cannot be regarded as an absolute or dichotomous concept because training regimens and sports activities are not exclusively dynamic or static and because the load on the heart is not purely of the volume or the pressure type. Most studies agree that left ventricular systolic and diastolic function is normal in the athlete at rest, whereas diastolic function seems to be enhanced in the exercising endurance athlete. The consistency of the results of studies on athletes in the competitive and the resting season, of training of sedentary subjects, and of spinal cord-injured patients suggests that variations in physical activity can alter left ventricular structure; genetic factors do not seem to be involved in the size of the left ventricular internal diameter but have to be taken into account to interpret wall thickness.

Longitudinal association of ambulatory pulse pressure with left ventricular mass and vascular hypertrophy in essential hypertension

OBJECTIVE

To determine the longitudinal relationship between clinic and ambulatory blood pressures and subsequent left ventricular and carotid artery structure.

DESIGN

A retrospective follow-up study.

SETTING

A large district general hospital in Harrow, UK.

PATIENTS

One hundred and forty patients who had been subjected to 24 h ambulatory intra-arterial blood pressure monitoring on the basis of their having an elevated clinic blood pressure were followed up randomly a mean of 9.4 +/- 3.4 years later. The ambulatory blood pressure parameters measured were the mean systolic, mean diastolic and mean pulse pressures. Follow-up variables assessed included the clinic blood pressure, body mass index, total cholesterol, number of years of follow-up, left ventricular mass index, carotid intima-media thickness and carotid artery cross-sectional area.

MAIN OUTCOME MEASURES

The left ventricular mass index, carotid intima-media thickness and carotid artery cross-sectional area.

RESULTS

The mean pulse pressure and mean systolic blood pressure were correlated significantly with the left ventricular mass index (r = 0.46, P < 0.001 and r = 0.36, P < 0.001, respectively), carotid intima-media thickness (r = 0.45, P < 0.001 and r = 0.37, P < 0.001, respectively) and carotid artery cross-sectional area (r = 0.46, P < 0.001 and r = 0.41, P < 0.001, respectively). The mean pulse pressure was associated independently with all three outcome measures. In addition, the body mass index was an independent determinant of the left ventricular mass index, whereas the serum cholesterol level was associated independently with the carotid artery cross-sectional area; the number of years of follow-up was related independently to the left ventricular mass index and carotid intima-media thickness, but not to the cross-sectional area.

CONCLUSIONS

These findings suggest that ambulatory blood pressure monitoring can play a role in guiding the choice of doses in drug therapy to limit potential target organ damage.

Prediction of left ventricular mass changes after renal transplantation by polymorphism of the angiotensin-converting-enzyme gene

Cardiac complications are the main cause of death in renal transplant patients and left ventricular hypertrophy (LVH) may play a determinant role. An association between the insertion-deletion polymorphism of the angiotensin-converting enzyme (ACE) gene and LVH has been reported in adults. However, little is known about the genetic influence on left ventricular mass changes after renal transplantation, where unique environmental factors, such as cyclosporine A (CsA) and prednisone treatment concur. In fact, CsA treatment has recently been associated with the development of LVH. We prospectively determined the changes on cardiac structure and function, assessed by echocardiographic criteria, in 38 consecutive nondiabetic adults who received a cadaveric renal allograft. They were treated with cyclosporine and prednisone and maintained a good renal function during the follow-up. Echocardiographic studies (M-mode, 2-B and color flow Doppler) were performed without previous knowledge of the genetic typing, at the time of transplantation, and 6 and 12 months later. ACE alleles were typed using a PCR-based assay developed to ascertain the presence of an insertion (I)-deletion (D) polymorphism in intron 16 of the ACE gene. Patients with the so-called "unfavorable" DD genotype (N = 16) were compared with the ID or II genotypes (N = 22). The baseline left ventricular mass index was similar in patients with or without the unfavorable DD genotype (X +/- SE; 166.6 +/- 10.4 vs. 181.3 +/- 9 g/m2, respectively) and a similar proportion fulfilled the criteria of LVH (88% vs. 82%, respectively). The mean percent increase of the left ventricular mass index 12 months after renal transplantation was significantly higher in patients with the DD genotype compared to those with other genotypes (21.3 +/- 7.9 vs. -0.08 +/- 4.9%, respectively; P < 0.05). As a result, 94% of DD patients showed LVH at the end of the follow-up, while 68% of the ID or II patients had LVH (P < 0.05). In addition, the left ventricular ejection fraction significantly increased only in ID or II patients 12 months after transplantation with respect to baseline (ID/II patients, 70.4 +/- 1.5 vs. 63.7 +/- 1.8%; P < 0.05; DD patients, 68.3 +/- 2.1 vs. 63.3 +/- 2.9%). The deleterious effect of the DD genotype was independent of blood pressure, biochemical parameters, weight gain, and cumulative steroids dosages or cyclosporine levels. In conclusion, genetic factors determine the changes on cardiac structure and function after renal transplantation. The presence of the DD genotype of the ACE gene is a marker associated with an elevated risk of LVH in this population.

One year of exercise training does not alter resting left ventricular systolic or diastolic function

Few studies have examined the effect of prolonged exercise training on left ventricular diastolic function in previously sedentary subjects. We performed M-mode, 2-D, and Doppler echocardiography on 16 previously sedentary men before and after 1 yr of exercise training. Six men served as controls. Exercise subjects participated in four 1-h supervised sessions weekly at 60-80% of their measured maximal heart rate. Maximal oxygen uptake, maximal exercise cardiac output, and resting left ventricular systolic and diastolic function were determined before and after training. Maximal oxygen uptake and peak cardiac output increased 27.3% and 8.5% in the trainers (P < 0.001 for both) and 1.3% and 1.0% in the controls. Left ventricular diastolic and systolic dimensions changed slightly in both groups. Maximal early inflow velocity decreased in both trainers (-9.9 +/- 14.0 cm.s-1, mean +/- SD, P < or = 0.01) and controls (-7.2 +/- 10.2 cm.s-1). Maximal atrial inflow velocity decreased (-7.8 +/- 10.9 cm.s-1, P < or = 0.01) only in the trainers possibly because of a reduction in resting heart rate (-6 +/- 11 beats.m-1, P < or = 0.05). Acceleration and deceleration times were unchanged in both groups. These results demonstrate that substantial increases in exercise performance and exercise cardiac output can occur without detectable changes in resting cardiac dimensions or left ventricular systolic and diastolic function.

Effects of type 1 diabetes mellitus on cardiac function: a study of monozygotic twins

OBJECTIVE

To investigate left ventricular size and function in type 1 diabetes and their relation with diabetes duration, glycaemic control, autonomic dysfunction, and complications of diabetes.

DESIGN

Cross sectional study using a pulsed wave Doppler echocardiogram to assess left ventricular dimensions, wall thickness, and transmitral blood flow velocity signals.

PATIENTS

40 monozygotic twin pairs (23 male, mean age 26 years) discordant for type 1 diabetes and 40 non-diabetic singleton controls with no clinical evidence of cardiac ischaemia.

RESULTS

For all Doppler echocardiographic measurements there were strong correlations between monozygotic twins but not between twins and control subjects. Left ventricular dimensions, wall thickness and systolic function, peak E velocity, and the velocity integrals of early left ventricular filling were similar in all three groups. Peak A velocity and the velocity integrals of late ventricular filling (mean (SD)) were greater in diabetic twins (45 (12) v 38 (8) cm/s, P = 0.002; and 32 (11) v 26 (6), P = 0.0002). Diabetic twins had lower E/A ratio (1.59 (0.39) v 1.83 (0.39), P < 0.001), greater atrial filling fraction to total diastolic filling (28 (6) v 25 (5)%, P = 0.002), and prolonged isovolumic relaxation time (72 (12) v 63 (9) ms, P < 0.001). The differences in Doppler findings between diabetic and non-diabetic twins were related to disease duration whereas the prolongation of the isovolumic relaxation time was related to cardiac autonomic dysfunction.

CONCLUSIONS

These results show that twins with type 1 diabetes have left ventricular diastolic dysfunction related to diabetes duration and cardiac autonomic dysfunction but not to glycaemic control or microvascular complications. In addition, genetic factors contribute to left ventricular dimension and function.

Association between a deletion polymorphism of the angiotensin-converting-enzyme gene and left ventricular hypertrophy

BACKGROUND

Epidemiologic studies have shown that left ventricular hypertrophy is often found in the absence of an elevated cardiac workload. To investigate whether such hypertrophy is determined in part by genetic factors, we studied the association between this condition, as assessed by electrocardiographic criteria, and a deletion (D)-insertion (I) polymorphism of the angiotensin-converting-enzyme (ACE) gene.

METHODS

A population-based random sample of 711 women and 717 men 45 to 59 years of age was studied cross-sectionally in Augsburg, Germany. Electrocardiographic indexes, including the Sokolow-Lyon index, Minnesota Code 3.1, and the Rautaharju equations, were used to detect left ventricular hypertrophy. The status of the ACE gene with respect to the deletion-insertion allele was determined by the polymerase chain reaction in all subjects with left ventricular hypertrophy and an identical number of control subjects without the condition who were matched for age, sex, and blood-pressure status.

RESULTS

We identified 141 women and 149 men with evidence of left ventricular hypertrophy. Among these subjects, an excess were homozygous for the D allele of the ACE gene (odds ratio, 1.76; 95 percent confidence interval, 1.22 to 2.53; P = 0.003). The association of the DD genotype with left ventricular hypertrophy was stronger in men (odds ratio, 2.63; 95 percent confidence interval, 1.50 to 4.64; P < 0.001) than in women and was most prominent when blood-pressure measurements were normal (odds ratio, 4.05; 95 percent confidence interval, 1.76 to 9.28; P = 0.001). This association was evident for each of the scores recorded in the electrocardiographic testing for left ventricular hypertrophy.

CONCLUSIONS

The findings suggest that left ventricular hypertrophy is partially determined by genetic disposition. They identify the DD genotype of ACE as a potential genetic marker associated with an elevated risk of left ventricular hypertrophy in middle-aged men.

Exercise electrocardiography and aortic Doppler velocimetry in asymptomatic identical twins discordant for type 1 (insulin dependent) diabetes

OBJECTIVE

To determine the influence of insulin dependent diabetes on the prevalence of myocardial ischaemia and on global left ventricular systolic performance.

DESIGN

Stress treadmill electrocardiograms and simultaneous Doppler measurement of aortic maximum acceleration were obtained during exercise on symptom free subjects. The electrocardiograms were scored blindly according to the Minnesota code.

PARTICIPANTS

39 identical twin pairs (22 male) discordant for insulin dependent diabetes and 39 non-diabetic controls of similar age and sex were examined. The twins and controls had a mean age of 37 (range 25-69) with a mean (SD) duration of diabetes in the diabetic twin of 17 (7) years. Those selected were normotensive and had no renal impairment.

RESULTS

Systolic blood pressure was significantly higher in the diabetic twins than in their non-diabetic cotwins both at rest (p < 0.05) and at peak exercise (p < 0.01). Electrocardiographic evidence of ischaemia was not correlated within twin pairs and was found in similar numbers of diabetic twins, their non-diabetic cotwins, and control subjects. Abnormal electrocardiograms were found in a similar number of diabetic twins (23%), non-diabetic cotwins (18%), and controls (15%). There was a significant correlation in Doppler measurements of global left ventricular systolic function within the identical twins; no significant difference was found for these Doppler measurements in the diabetic twins, non-diabetic cotwins, or controls.

CONCLUSION

Exercise characteristics and cardiac function seem to be subject to shared genetic or shared environmental influences or both, whereas electrocardiographic features of ischaemia seem to be environmentally determined. In a selected cohort of diabetic identical twins without evidence of nephropathy there was no evidence that diabetes influenced the prevalence of myocardial ischaemia or global left ventricular systolic function.

Relation of left ventricular mass, preload, afterload and contractility in pediatric patients with essential hypertension

OBJECTIVES

The aim of this study was to determine if left ventricular preload, afterload or contractility is a correlate of left ventricular mass index in hypertensive pediatric patients.

BACKGROUND

It is believed that decreased contractility and increased preload are associated with left ventricular hypertrophy in adult hypertensive patients.

METHODS

Ninety pediatric hypertensive patients underwent echocardiography to assess left ventricular mass, preload (diastolic dimension and volume) and afterload (end-systolic wall stress, vascular resistance and blood pressure). Contractility was assessed by 1) the end-systolic stress/volume ratio, and 2) the difference between measured and predicted velocity of circumferential fiber shortening. Univariate and multivariate analyses were performed.

RESULTS

Univariate analysis showed significant correlations between left ventricular mass and 1) body mass (r = 0.33, p < 0.001), 2) black race (r = 0.37, p < 0.0003), 3) diastolic dimension (r = 0.26, p < 0.01), 4) diastolic volume (r = 0.20, p < 0.05), and 5) stress/volume ratio (r = -0.53, p < 0.0001) but not the difference between measured and predicted velocity of circumferential fiber shortening. A multivariate model included body mass, age at diagnosis, diastolic dimension, wall stress and vascular resistance but not the difference between measured and predicted velocity of circumferential fiber shortening.

CONCLUSIONS

Contractility is not significantly related to left ventricular mass. The positive correlation between mass and stress/volume may be due to the dependence of the latter variable on loading conditions. We speculate that both elevated preload and systemic vascular resistance may have a role in the development of hypertrophy in hypertensive pediatric patients.

Bivariate genetic analysis of left ventricular mass and weight in pubertal twins (the Medical College of Virginia twin study)

Left ventricular (LV) hypertrophy in adults is a recognized risk factor for the subsequent development of cardiovascular morbidity. To make informed preventive health decisions it is important to understand the interaction of genes and environment on LV mass. In both children and adults, weight is a strong correlate of LV mass. We hypothesized that genetic influences common to both of these variables could in part explain the strong relation between weight and LV mass in children. In a population of 341 twins (11 years old), these questions were asked: (1) How much of the total variance of LV mass is under genetic control? (2) After accounting for weight and weight adjusted for sexual maturity, how much of the remaining variance is genetic? (3) Of the total genetic variance, what proportion is specific for LV mass and what proportion is common to both weight and LV mass? (4) How much of the correlation between these 2 variables is explained by genes common to both LV mass and weight? Univariate genetic analyses documented that genes operating at different magnitudes in boys (63%) and girls (71%) explain a significant proportion of the variance of LV mass. After removing the effect of weight and sexual maturity by regression methods, genes remain an important influence. Bivariate genetic analyses confirmed that genes common to LV mass and weight significantly influence the covariation of these variables and that greater than 90% of the correlation of LV mass and weight is due to common genes.