Physiological determinants of the variation in left ventricular mass from early adolescence to late adulthood in healthy subjects

BACKGROUND: The physiological determinants of left ventricular mass (LVM) measured by cardiac magnetic resonance (CMR) imaging are not well defined as prior investigators have studied either adults or adolescents in isolation or have not strictly excluded hypertension or accounted for the effects of exercise habits, haemodynamic, demographic, or body shape characteristics. METHODS: A total of 102 healthy volunteers (12-81 years, 53 males) underwent CMR. All parameters [unstandardized and adjusted for body surface area (BSA)] were analysed according to gender and by adolescence versus adulthood (adolescents <20 years, adults > or = 20 years). The influence of haemodynamic factors, exercise, and demographic factors on LVM were determined with multivariate linear regression. Results: LVM rose during adolescence and declined in adulthood. LVM and LVMBSA were higher in males both in adults (LVM: 188 +/- 22 g versus 139 +/- 21 g, P < 0.001; LVMBSA: 94 +/- 11 g m(-2) versus 80 +/- 11 g m(-2), P < 0.001) and in adolescents when adjusted for BSA (LVM: 128 +/- 29 g versus 107 +/- 20 g, P = 0.063; LVMBSA: 82 +/- 8 g m(-2) versus 71 +/- 10 g m(-2), P = 0.025). In adults, systolic blood pressure (SBP) and self-reported physical activity increased while meridional and circumferential wall stress were constant with age. Multivariate regression analysis revealed age, gender, and BSA as the major determinants of LVM (global R2 = 0.69). CONCLUSIONS: Normal LVM shows variation over a broad age range in both genders with a rise in adolescence and subsequent decline with increasing age in adulthood despite an increase in SBP and physical activity. BSA, age, and gender were found to be major contributors to the variation in LVM in healthy adults, while haemodynamic factors, exercise, and wall stress were not.     

Echocardiographic measurements of left ventricle in normal infants and children

Echocardiographic studies were performed on 110 normal infants and children ranging in age from 2 days to 15 years. The following parameters of the left ventricle were measured: left ventricular end-diastolic and end-systolic diameters (LVEDd and LVESd), shortening fraction (LVSF), end-diastolic volume (LVEDV), ejection fraction (LVEF), posterior wall thickness in end-diastole (LVPWED) and end-systole (LVPWES), mass (LVM), LVEDd/LVPWED, LVESd/LVPWES and mean velocity of circumferential fiber shortening (LV mean Vcf). Each parameter was compared with body surface area (BSA). LVEDd, LVESd, LVEDV, LVPWED, LVPWES and LVM were expressed as a function of body surface area with exponential equations: LVEDd = 41.4 (BSA)0.49 mm, LVESd = 28.1 (BSA)0.49 mm, LVEDV = 74.1 (BSA)1.48 ml, LVPWED = 4.4 (BSA)0.45 mm, LVPWES = 9.2 (BSA)0.44 mm and LVM = 46.4 (BSA)1.48 g. LVSF, LVEDd/LVPWED, LVESd/LVPWES and LV mean Vcf were independent of body surface area: LVSF averaged 32 +/- 1 (mean +/- standard error of the mean)%, LVEF 68 +/- 1%, LVEDd/LVPWED 10.0 +/- 0.2, LVESd/LVPWES 3.1 +/- 0.1 and LV mean Vcf 1.08 +/- 0.02 circ/sec. Thus, normal values of these parameters can be applied to estimate them in pediatric patients with heart diseases.     

Gender,exercise, and health: A life‐course cross‐sectional study

The purpose of this study is to explore relationships between the practice of exercise, gender, and health, from adolescence to old age, testing the magnitude of gender differences throughout the life cycle in the practice of exercise of Spanish people. A cross‐sectional study with 4,575 women and 4,334 men, aged 13–85 years, was conducted. The participants were assessed on the weekly hours they dedicated to the practice of exercise, masculine/instrumental and feminine/expressive traits, mental health symptomatology, and self‐rated health). Univariate and multivariate analyses were performed in the age groups of adolescence, late adolescence, young adulthood, middle adulthood, and older age. Results showed that men dedicated significantly more hours to the practice of exercise than women within all age groups, except in older age (men´s average = 4.07; women´s average = 2.55). The masculine/instrumental trait played a mediating role between gender and practice of exercise hours. Furthermore, a decline in the amount of time dedicated to exercise from adolescence to older age was found, with higher drops in men. Finally, the practice of exercise was associated with better self‐rated health and less mental symptoms. These results underline the important role that gender and masculine‐instrumental trait play on the practice of exercise .     

Ventilatory efficiency and rate of perceived exertion in obese and non-obese children performing standardized exercise

Sixty children, in the age span 6-17 years originally divided into two groups, matched by age, sex and height--30 obese subjects [15 girls/15 boys; body mass index (BMI) = 27.4 +/- 4.5 m kg-2; ideal body weight (IBW) range = 122-185%] and 30 controls (BMI = 18.8 +/- 2.7 m kg-2) performed incremental treadmill exercise test. Perceived exertion was assessed by means of Category-Ratio Borg scale. The duration of the exercise for the children in the obesity group was significantly shorter than controls (P = 0.010) but obese children have greater absolute values for oxygen uptake (VO2peak ml min-1 = 1907 +/- 671 versus 1495 +/- 562; P = 0.013) and ventilatory variables (VE, VT), which adjusted for body mass decrease significantly (VO2/kg ml min-1 kg-1 = 29.2 +/- 3.8 versus 33.6 +/- 3.5; P < 0.001). Among the various methods for 'normalizing' absolute values of VO2peak for body size, dividing it by body surface area (BSA) yielded the best results (VO2/BSA ml min-1 m-2 = 43.5 +/- 4.6 versus 44.7 +/- 5.6; P = 0.335). The ventilatory efficiency determined either as a slope of VE versus VCO2 or as a simple ratio at anaerobic threshold did not differ between obese and non-obese children in the incremental and recovery periods of exercise. There was a negative correlation of VE/VCO2 slope with age and anthropometric parameters. Obese children rated perceived exertion significantly higher than controls despite the standard workload (Borg score = 6.2 +/- 1.2 versus 5.2 +/- 1.1; P = 0.001). In conclusion, the absolute metabolic cost of exercise is higher in the obesity group compared with the control subjects. Both groups have similar ventilatory efficiency but an increased awareness of fatigue that furthermore limits their physical capacity.     

Tissue cardiovascular magnetic resonance demonstrates regional diastolic dysfunction in remote tissue early after inferior myocardial infarction.

PURPOSE: To investigate regional diastolic and systolic function using tissue cardiovascular magnetic resonance (CMR), early after transmural myocardial infarction of the inferior wall due to single proximal right coronary artery disease. MATERIALS AND METHODS: Velocity encoded CMR was used to measure early diastolic transmitral flow velocity (E), and regional, longitudinal, myocardial systolic (Sa) and early diastolic (Ea) velocities (tissue CMR) in 15 patients with a recent transmural inferior myocardial infarction and in 15 age and LV-mass index matched control subjects. An unpaired two-tailed t test was used to assess significance of continuous variables. RESULTS: Global systolic (ejection fraction 46 +/- 7% versus 57 +/- 4%, p = 0.000052) and global diastolic LV function (average Ea of infarcted or inferior, remote or anterior, adjacent or septal and lateral myocardium 6.8 +/- 1.7 cm/s versus 10.4 +/- 1.5 cm/s, p = 0.0000012) were impaired in patients as compared to controls. Regional systolic and diastolic LV velocities were impaired in infarcted and adjacent tissue in patients. However, in remote or anterior tissue, systolic velocities were preserved (Sa 6.6 +/- 2.0 cm/s versus 6.8 +/- 1.4 cm/s, p = 0.70), but diastolic velocities were impaired in patients as compared to controls (Ea 7.2 +/- 2.3 cm/s versus 10.2 +/- 2.5 cm/s, p = 0.0026). CONCLUSIONS: Regional diastolic velocities early after inferior myocardial infarction are impaired in the infarcted, adjacent and remote tissue, but regional systolic velocities are preserved in remote tissue.     

Similarity in amplitude of the nocturnal fall in blood pressure in old and young patients with essential hypertension

The influence of age on the nocturnal fall in blood pressure (BP) was examined in essential hypertensive patients as well as normal subjects. BP was monitored every 5 min for 24 hr by means of a finger volume oscillometric device. Average daytime BP was similar in the 3 age groups [young: less than 40 (years), n = 49, average daytime systolic BP (ASBP) = 132 +/- 20 mmHg, average daytime diastolic BP (ADBP) = 82 +/- 17 mmHg; adult: 40 less than or equal to less than 60, n = 110, ASBP = 127 +/- 19 mmHg, ADBP = 86 +/- 13 mmHg; old: 60 less than or equal to, n = 33, ASBP = 131 +/- 17 mmHg. ADBP = 83 +/- 11, mean +/- S.D.]. The nocturnal fall in BP was observed in all age groups and its amplitude (delta BP = average daytime BP - average nighttime BP) in the old patients (delta SBP = 13 +/- 11 mmHg, delta DBP = 10 + 8 mmHg) was similar to that in the young patients (delta SBP = 11 +/- 8 mmHg, delta DBP = 10 +/- 8 mmHg). The results suggests that information on the nocturnal behavior of BP is valuable in treating aged essential hypertensives to prevent cerebral and/or myocardial ischemia during sleep.     

Effects of exercise training on aerobic and functional capacity of end-stage renal disease patients

The aim was to assess the effects of exercise training on aerobic and fuctional capacity of patients with end-stage renal disease (ESRD). Patients completed an incremental exercise test on a cycle ergometer to determine VO2 peak and VO2 at ventilatory threshold (VT; V-slope). On a separate day they performed two constant load exercise tests on a cycle ergometer at 90% of VT and at a workload of 33 W, to determine VO2 kinetics. Functional capacity was assessed using measurements of sit-to-stands (STS-5, STS-60) and a walk test. Dialysis patients were randomly allocated to an exercise (ET: n = 18, age = 57.3 years) or control (C: n = 15, age = 50.5 - 5 years) group. The ET group participated in an exercise training programme involving cycling for 3 months. Repeated measures ANOVA revealed significant time by group interactions (P < 0.05) following training for VO2 peak (ET: 17 +/- 6.1 versus 19.9 +/- 6-3, C: 19.5 +/- 4.7 versus 188 +/- 4.9 ml kg min(-1)) and VO2-VT (ET: 10.7 +/- 3.5 versus 11.8 +/- 3.3, C:12.9 +/- 3.2 versus 119 +/- 3.5 ml kg min(-10). VO2 kinetics remained unchanged in both groups at 90% -VT, but a trend (P = 0.059) towards faster kinetics at the 33 W was observed (ET: 49.6 +/- 19.5 versus 37.8 +/- 12.7, C: 42.8 +/- 13 versus 49.4 +/- 20.2 s). Significant time by group interactions (P < 0.05) were also observed for STS-5 (ET: 14.7 +/- 6.2 versus 11.0 +/- 3.3, C: 12.8 +/- 4.4 versus 12.7 +/- 4.8 s) and STS-60 measurements (ET: 21.2 + 7.2 versus 26.9 +/- 6.2, C: 23.7 +/- 6.8 versus 24.1 +/- 7.2). Three months of exercise rehabilitation significantly improves peak exercise capacity of patients with ESRD. Measurements of VO2 kinetics and functional capacity suggest that longer time might be needed to induce peripheral adaptations.     

Relationship between birthweight and arterial elasticity in childhood

There is a considerable debate about the potential influence of 'fetal programming' on cardiovascular diseases in adulthood. In the present prospective epidemiological cohort study, the relationship between birthweight and arterial elasticity in 472 children between 5 and 8 years of age was assessed. LAEI (large artery elasticity index), SAEI (small artery elasticity index) and BP (blood pressure) were assessed using the HDI/PulseWave CR-2000 CardioVascular Profiling System. Blood concentrations of glucose, total cholesterol and its fractions [LDL (low-density lipoprotein)-cholesterol and HDL (high-density lipoprotein)-cholesterol] and triacylglycerols (triglycerides) were determined by automated enzymatic methods. Insulin was assessed by a chemiluminescent method, insulin resistance by HOMA (homoeostasis model assessment) and CRP (C-reactive protein) by immunonephelometry. Two linear regression models were applied to investigate the relationship between the outcomes, LAEI and SAEI, and the following variables: birthweight, gestational age, glucose, LDL-cholesterol, HDL-cholesterol, triacylglycerols, insulin, CRP, HOMA, age, gender, waist circumference, per capita income, SBP (systolic BP) and DBP (diastolic BP). LAEI was positively associated with birthweight (P=0.036), waist circumference (P<0.001) and age (P<0.001), and negatively associated with CRP (P=0.024) and SBP (P<0.001). SAEI was positively associated with birthweight (P=0.04), waist circumference (P=0.001) and age (P<0.001), and negatively associated with DBP (P<0.001). Arterial elasticity was decreased in apparently healthy children who had lower birthweights, indicating an earlier atherogenetic susceptibility to cardiovascular diseases in adolescence and adult life. Possible explanations for the results include changes in angiogenesis during critical phases of intrauterine life caused by periods of fetal growth inhibition and local haemodynamic anomalies as a way of adaptation to abnormal pressure and flow.     

24-h Systolic blood pressure and heart rate recordings in lean and obese adolescents

OBJECTIVE: We assessed the hypothesis that differences in day and night-time systolic blood pressure (SBP) and heart rate (HR) recordings were smaller in obese versus lean children and adolescents, and whether measurements obtained during a school week or during weekends or holidays influenced these nocturnal falls. We also wanted to determine whether the results were influenced by gender. METHODS: Ambulatory 24-h BP and HR measurements were performed in 80 subjects, 51 girls and 29 boys. Lean (n = 25) and obese (n = 55) subjects were classified according to body mass index (BMI)-standard deviation (SD) criteria. Forty-eight subjects had their 24-h recordings performed during a school week and 32 during leisure time. RESULTS: The SBP nocturnal dipping response was less pronounced in obese subjects (16.2 +/- 6.3 mmHg) compared with lean controls (21.1 +/- 5.7 mmHg) (P < 0.01) of which the girls constituted most of the difference. HR change between day and night was similar in both groups being approximately 15 b/min. A small but statistical negative correlation was observed between BMI-SD and nocturnal fall in SBP (r = -0.3, P = 0.0065). In all subjects, regardless of BMI-SD, daytime SBP was higher when readings were obtained during a school week (123 +/- 7 mmHg) than during weekends or holidays (119 +/- 7 mmHg) (P = 0.029). CONCLUSION: Obese children and adolescents showed smaller nocturnal falls in SBP compared with lean subjects. This pattern may cause increased cardiovascular loading; thus, it may reflect an early sign of high blood pressure development and adds to cardiovascular risk in young obese individuals.     

Blood pressure and heart rate effects following a single dose of bitter orange

BACKGROUND: The ingredients of numerous "ephedra-free" dietary supplements used for weight loss include bitter orange, which contains sympathomimetic alkaloids such as synephrine. Due to the similarity in chemical structure to ephedrine and the potential sympathomimetic effects of synephrine, it is hypothesized that bitter orange may increase blood pressure (BP) and heart rate (HR). OBJECTIVE: To determine the effects on BP and HR after a single dose of bitter orange in healthy adults. METHODS: In a prospective, randomized, double-blind, placebo-controlled, crossover study, 15 young, healthy, adult subjects received either a single dose of Nature's Way Bitter Orange--a 900 mg dietary supplement extract standardized to 6% synephrine--or matching placebo, with a one week washout period. Systolic BP (SBP), diastolic BP (DBP), and HR were measured at baseline and every hour for 6 hours after administration. RESULTS: SBP after bitter orange was significantly increased versus placebo at hours 1-5 (p < 0.0001); the peak difference was 7.3 +/- 4.6 mm Hg. Although the baseline DBP was higher than after administration of both placebo and bitter orange, DBP after bitter orange was significantly increased versus placebo at hours 4 and 5 (p < or = 0.02); the peak difference was 2.6 +/- 3.8 mm Hg. HR was significantly increased after bitter orange versus placebo for hours 2-5 (p < 0.01); the peak difference was 4.2 +/- 4.5 beats/min. CONCLUSIONS: SBP, DBP, and HR were higher for up to 5 hours after a single dose of bitter orange versus placebo in young, healthy adults.     

Role of retrograde flow in the shear stimulus associated with exercise blood flow

To test the hypothesis that retrograde flow influences the shear stimulus of exercise blood flow, eight healthy men [25.6+/-3.1 years (SD)] performed 20 min of single-leg knee-extension exercise at two contraction velocities: fast (FR, 1.5 m s(-1)) and slow (SR, 0.4 m s(-1)). Contraction frequency (30 cpm) and workload (5 kg) were kept constant resulting in a work rate of 15.25 W for both contraction velocities. Common femoral artery diameter and blood velocity were measured at rest and during exercise using ultrasound Doppler. Mean blood flow was not different between contraction velocities while antegrade (2012.4+/-379.9 versus 1745.6+/-601.5 ml min(-1); P=0.05) and retrograde (121.7+/-43.0 versus 11.2+/-6.6 ml min(-1); P<0.001) flows were higher during FR than SR contractions, respectively. Despite the similar mean blood flow response, vascular resistance was lower during FR than SR contractions (0.06+/-0.01 versus 0.08+/-0.03 units; P=0.03) and was closely related to shear rate (pooled data: r=-0.77, P<0.01). Retrograde flow was associated with a lower vascular resistance during exercise (pooled data: r=-0.48, P相似文献   

Determination of normal gender-specific left atrial dimensions by cardiovascular magnetic resonance imaging.

BACKGROUND: Because cardiovascular magnetic resonance imaging (CMR) is becoming increasingly available in clinical practice, there is a need to establish normal values for left atrial dimensions as determined by this method to allow accurate assessment of cardiac dimensions and to provide standardization for follow up studies. For clinical purpose measurements of the left atrial end diastolic diameter (LAEDD) are most appropriate to assess left atrial size. We aimed to establish normal values for LAEDD using CMR and a fast gradient-echo sequence with steady-state free precession (SSFP). METHODS: A total of 111 healthy subjects (52 women and 59 men, mean age 51.5 +/- 14.5 years) were examined by CMR. Images were acquired using SSFP in the horizontal (HLA) and vertical (VLA) long axis planes and the left ventricular outflow tract plane (LVOT) to measure the LAEDD. RESULTS: Age between men and women was not different (p = 0.7050). CMR yielded the following normal ranges for LAEDD: HLA 4.5 +/- 0.4 cm for men and 4.2 +/- 0.5 for women, VLA 4.5 +/- 0.5 cm for men and 4.2 +/- 0.4 for women, and LVOT 2.8 +/- 0.3 cm for men and 2.8 +/- 0.4 for women. LAEDD were significantly larger in HLA and VLA than in LVOT (p < or = 0.0001). There was no significant difference in the measurements between HLA and VLA (p = 0.4617). Gender-related differences for LAEDD were found in HLA (p = 0.0087) and VLA (p = 0.0015) but not in LVOT (p = 0.5281). LAEDD were not found to be age-related (p > or = 0.0994). CONCLUSIONS: LAEDD differ significantly according to the image plane. We provide reference values for CMR using prospective triggering in the evaluation of left atrial diameters to identify patients with enlarged left atria and for follow-up studies.     

Assessment of left and right ventricular parameters in healthy Korean volunteers using cardiac magnetic resonance imaging: change in ventricular volume and function based on age,gender and body surface area

The clinical utility of cardiac magnetic resonance imaging (CMR) is growing and is being used predominantly as a means of measuring ventricular function. The normal reference range of ventricular function may vary based on age, sex and ethnicity. At present, most CMR reference values for healthy individuals have been reported from Western countries. The intent of this study was to investigate the normal CMR reference range for left ventricular (LV) and right ventricular (RV) parameters in healthy Koreans. Healthy volunteers between the ages of 20–70 years without any history of cardiovascular disease or associated risk factors were prospectively recruited to be a part of this study. A total of 124 patients were recruited for this study. Steady-state free precession pulse sequences were used to obtain the cine images for LV and RV volume analysis. All parameters were analyzed based on age and gender, and normalized to body surface area (BSA). LV volume, mass and cardiac output were significantly greater in males than in females. However, all of these parameters which are associated with BSA and gender differences disappeared when corrected for BSA. RV volume was less in females even after the data was normalized for BSA. LV and RV volumes normalized for BSA gradually decreased with greater age, whereas the ejection fraction increased with age, thus maintaining the stroke volume index and cardiac index. LV and RV volumes, mass and function values for a healthy population largely depend on BSA and should be evaluated after normalization by BSA. LV parameters show no difference based on gender, but RV volume is less in the female. Greater age is associated with less ventricular volume, suggesting the possibility of volume sensitivity in the elderly.     

The effects of home-based resistance exercise on balance, power, and mobility in adults with multiple sclerosis

OBJECTIVE: To examine the effects of an 8-week home-based resistance exercise program on balance, power, and mobility in adults with multiple sclerosis. DESIGN: Experimental group design. SETTING: General community. PARTICIPANTS: Twenty-nine women (age, 50.3+/-8.5 y) and 8 men (age, 51.1+/-7.1 y) were stratified by disability level and age and were randomized into exercise (n=19) and control (n=17) groups. INTERVENTION: The exercise group had lower-extremity resistance training 3 times a week. The control group maintained current level of physical activity.Main outcome measures Primary outcome measures included balance, as measured by anteroposterior sway, mediolateral sway, and sway velocity using the AccuSway(PLUS) force platform; mobility as assessed with the Up and Go test; and leg power as assessed with the Leg Extensor Power Rig. RESULTS: Leg extensor power improved significantly in the exercise group (pretest, 3.19+/-1.36 W/kg; posttest, 3.95+/-1.23 W/kg; P=.004), although measures of balance and mobility did not change. CONCLUSIONS: The home-based resistance program was well tolerated by participants and offered a practical means to improve leg extensor power in a short period of time.     

Comparison between fundamental and second-harmonic imaging echocardiography for calculation of left ventricular mass in children

In adults, calculation of left ventricular mass (LVM) has been shown to give higher values when based on M-mode measurements obtained by the second-harmonic imaging (SHI) technique than with the older fundamental imaging (FI) technique. No information is available in paediatric subjects. This study, therefore, compares LVM calculated from measurements obtained with SHI and FI in 14 children, aged 6.9-13.0 years. M-mode tracings were obtained in accordance with American Society of Echocardiography (ASE) recommendations. Three experienced sonographers performed measurements on each subject with both SHI and FI. The mean value was used in all calculations. LVM was calculated according to ASE convention and indexed by body surface area. LVM mean values were 58.9 +/- 9.7 g m(-2) for SHI and 57.8 +/- 8.2 g m(-2) for FI (P = 0.45). This preliminary study in a small group of paediatric subjects demonstrates no systematic differences between FI and SHI modalities in the calculation of LVM. The likely explanation is that the left ventricular endocardial border is usually well visualized with SHI as well as with FI in children.     

The alpha-adducin Gly460Trp polymorphism and the antihypertensive effects of exercise among men with high blood pressure

The alpha-adducin Gly460Trp polymorphism alters renal sodium transport and is associated with hypertension. Despite the immediate sodium- and volume-depleting effects of aerobic exercise, the influence of the alpha-adducin Gly460Trp polymorphism on PEH (postexercise hypotension) has not been studied. In the present study we examined the effects of the alpha-adducin Gly460Trp polymorphism on PEH among 48 men (42.6+/-1.6 years; mean+/-S.E.M.) with high BP (blood pressure; 144.0+/-1.7/84.7+/-1.1 mmHg). Subjects completed three experiments: non-exercise control and two cycle exercise sessions at 40% (light exercise) and 60% (moderate exercise) of maximal oxygen consumption. Subjects left the laboratory wearing an ambulatory BP monitor. PCR and restriction enzyme digestion determined the genotypes. No subjects had the Trp460Trp genotype due to the low frequency of 5% in the population. Repeated measure ANCOVA tested whether BP differed over time between experimental conditions and genotypes (Gly460Gly, n=36; Gly460Trp, n=12). Among Gly460Gly genotypes, SBP (systolic BP) was reduced by 5.2+/-1.4 mmHg after moderate exercise compared with non-exercise controls over 9 h (P<0.01). Among Gly460Trp genotypes, SBP was lowered by 7.8+/-2.3 mmHg; after light exercise compared with non-exercise controls over 9 h (P<0.05). The SBP reductions after light exercise (0.6+/-1.3 compared with 7.8+/-2.3 mmHg; P<0.05) but not moderate exercise (5.2+/-1.4 compared with 3.8+/-2.4 mmHg; P> or =0.05) differed between the Gly460Gly and Gly460Trp genotypes respectively. Men with Gly460Gly had a reduced SBP after moderate exercise, whereas men with Gly460Trp had a reduced SBP after light exercise. However, only the SBP reductions after light exercise differed between genotypes. Our findings indicate that the alpha-adducin Gly460Trp genotype may be useful in identifying men who have a reduced BP after lower intensity aerobic exercise.     

Reference left atrial dimensions and volumes by steady state free precession cardiovascular magnetic resonance

Background

Left atrial (LA) size is related to cardiovascular morbidity and mortality. Cardiovascular magnetic resonance (CMR) provides high quality images of the left atrium with high temporal resolution steady state free precession (SSFP) cine sequences. We used SSFP cines to define normal ranges for LA volumes and dimensions relative to gender, age and body surface area (BSA), and examine the relative value of 2D atrial imaging techniques in patients.For definition of normal ranges of LA volume we studied 120 healthy subjects after careful exclusion of cardiovascular abnormality (60 men, 60 women; 20 subjects per age decile from 20 to 80 years). Data were generated from 3-dimensional modeling, including tracking of the atrioventricular ring motion and time-volume curves analysis. For definition of the best 2D images-derived predictors of LA enlargement, we studied 120 patients (60 men, 60 women; age range 20 to 80 years) with a clinical indication for CMR.

Results

In the healthy subjects, age was associated with LA 4-chamber transverse and 3-chamber anteroposterior diameters, but not with LA volume. Gender was an independent predictor of most absolute LA dimensions and volume, but following normalization to BSA, some associations became non-significant. CMR normal ranges were modeled and are tabled for clinical use with normalization, where appropriate, for BSA and gender and display of parameter variation with age. The best 2D predictors of LA volume were the 2-chamber area and 3-chamber area (both r = 0.90, p < 0.001).

Conclusions

These CMR data show that LA dimensions and volume in healthy, individuals vary significantly by BSA, with lesser effects of age and gender.     

Effect of body surface area calculations on body fat estimates in non-obese and obese subjects

The purpose of the present study was to compare body surface area (BSA) estimates using two equations (Dubois and Dubois versus Livingston) and their respective effects on per cent body fat (%BF) obtained with two molecular approaches of body composition analysis, two-compartment (2C) and five-compartment (5C) models. Body composition data using the 2C model were studied in healthy adults, 432 women (body mass index (BMI): 28.3 +/- 4.4 kg m(-2)) and 147 men (BMI: 26.8 +/- 3.9 kg m(-2)), while another sample of 126 women (BMI: 30.4 +/- 3.7 kg m(-2)) was evaluated using the 5C model. Measures of body volume (BV) assessed by air displacement plethysmography, bone mineral content by dual energy x-ray absorptiometry (DXA) and total-body water by deuterium dilution were used to estimate %BF with the 5C model. Comparison of means and linear regression analysis was performed. Using BSA(Dubois), either in 2C and 5C models, BV and %BF estimates were significantly underestimated compared to results obtained using BSA(Livingston) (p < 0.05). BMI was strongly associated with %BF differences using BSA(Dubois) and BSA(Livingston) in both 2C (men: r = 0.90; women: r = 0.88) and 5C models (r = 0.88). Though %BF(Dubois) and %BF(Livingston) were strongly associated (r(2) = 1.000), some variability was observed on %BF differences using BSA(Dubois) and BSA(Livingston). These findings suggest that BSA calculation is critical in BF estimation, supporting the use of a more accurate equation for non-obese and obese subjects.