Role of left ventricular mass/volume ratio on transmitral flow velocity patterns from infancy to childhood

Myocardial Rotation and Torsion in Child Growth

Background

The speckle tracking echocardiography can benefit to assess the regional myocardial deformations. Although, previous reports suggested no significant change in left ventricular (LV) torsion with aging, there are certain differences in LV rotation at the base and apex. The purpose of this study was to evaluate the change and relationship of LV rotation for torsion with aging in children.

Methods

Forty healthy children were recruited and divided into two groups of twenty based on whether the children were preschool-age (2–6 years of age) or school-age (7–12 years of age). After obtaining conventional echocardiographic data, apical and basal short axis rotation were assessed with speckle tracking echocardiography. LV rotation in the basal and apical short axis planes was determined using six myocardial segments along the central axis.

Results

Apical and basal LV rotation did not show the statistical difference with increased age between preschool- and school-age children. Apical radial strain showed significant higher values in preschool-age children, especially at the anterior (52.8 ± 17.4% vs. 34.7 ± 23.2%, p < 0.02), lateral (55.8 ± 20.4% vs. 36.1 ± 22.7%, p < 0.02), and posterior segments (57.1 ± 17.6% vs. 38.5 ± 21.7%, p < 0.01). The torsion values did not demonstrate the statistical difference between two groups.

Conclusion

This study revealed the tendency of higher rotation values in preschool-age children than in school-age children. The lesser values of rotation and torsion with increased age during childhood warrant further investigation.

Gender differences in diastolic function among youth

BACKGROUND

Youth were studied to determine the influence of gender on diastolic function, which has been shown to express abnormalities early in the course of congestive heart failure.

METHODS

The study participants were 121 normotensive individuals (53 girls, 68 boys) ages 14 to 18 years. Demographics, hemodynamics, and Doppler-derived indices of diastolic function were collected. Dependent measures of diastolic function were the ratio of early (E) to late (A) peak filling velocities and the isovolumetric relaxation time (IVRT).

RESULTS

The girls had a higher relative wall thickness (RWT) (36.58% +/- 4.59% vs 34.60% +/- 4.01%; p < 0.02), higher A (48.40 +/- 8.47 cm/s vs 42.36 +/- 10.43 cm/s; p < 0.001), a lower E/A ratio (1.96 +/- 0.40 vs 2.38 +/- 0.68; p < 0.01), and a shorter IVRT (51.80 +/- 11.14 ms vs 59.00 +/- 14.36 ms; p < 0.01) than the boys. The differences in deceleration time were not significant (181.30 +/- 81.33 ms vs 170.30 +/- 31.06 ms). Hierarchical stepwise regression analysis predicting E/A ratio found gender (male > female) to be the best predictor (R (2 )= 0.09) followed by heart rate (R (2) increase = 0.07; total R (2 )= 0.15; p < 0.01) and by RWT (R (2) increase = 0.05; total R (2 )= 0.21; p < 0.015). For IVRT prediction, gender (male > female) was the best predictor (R (2 )= 0.11), followed by total peripheral resistance (R (2) increase = 0.06; total R (2 )= 0.17; p < 0.017).

CONCLUSION

The study data indicate that gender differences in diastolic function exist already in youth. Girls show a higher RWT, a lower E/A ratio, and a shorter IVRT. The implications of these differences for cardiovascular morbidity and mortality of the two genders require attention.

Left ventricular mass in 169 healthy children and young adults assessed by three-dimensional echocardiography

The aims of this study were to establish normal values of left ventricular (LV) mass in children and young adults using three-dimensional echocardiography (3-DE) and to compare 3-DE LV mass estimates with those obtained by conventional echocardiographic methods. We studied 169 healthy subjects aged 2-27 years by digitized 3-D, two-dimensional (2-D), and M-mode echocardiography. 3-D echocardiography was performed by using rotational acquisition of planes at 18 degrees intervals from apical view with ECG gating and without respiratory gating. 3-DE gave smaller LV mass estimates than 2-DE and M-mode echocardiography (p < 0.001). Agreement analysis resulted in a bias of -9.3 +/- 36.5 g between 3-DE and 2-DE, and -18.5 +/- 47.9 g between 3-DE and M-mode. For the analysis, the subjects were divided into five groups according to body surface area (BSA): 0.5-0.75, 0.75-1.0, 1.0-1.25, 1.25-1.5, and greater than 1.5 m(2). LV mass/BSA by 3-DE was 45.6 (5.1), 54.3 (7.7), 55.2 (7.9), 58.8 (8.1), and 65.0 (9.9) g/m(2). LV mass/end diastolic volume (EDV) by 3-DE was 0.9 (0.1) g/ml in the BSA group of 0.5-0.75 m(2) and 1.0 (0.2) g/ml in the other BSA groups. LV mass increased linearly in relation to BSA, height, and body mass (r = 0.93, 0.90, and 0.92, respectively; p < 0.001 for all). The results showed a linear increase in LV mass, whereas LV mass/EDV ratio remained unchanged. However, LV mass estimates by 3-DE were lower than those obtained by 2-DE and M-mode echocardiography. The data obtained by 3-DE from 169 healthy subjects will serve as a reference for further studies in patients with various cardiac abnormalities.

Maturational and Adaptive Modulation of Left Ventricular Torsional Biomechanics

Background— Left ventricular (LV) torsional deformation, based in part on the helical myocardial fiber architecture, is an important component of LV systolic and diastolic performance. However, there is no comprehensive study describing its normal development during childhood and adult life.

Methods and Results— Forty-five normal subjects (25 children and 20 adults; aged 9 days to 49 years; divided into 5 groups: infants, children, adolescents, and young and middle-age adults) underwent assessment of LV torsion and untwisting rate by Doppler tissue imaging. LV torsion increased with age, primarily owing to augmentation in basal clockwise rotation during childhood and apical counterclockwise rotation during adulthood. Although LV torsion and untwisting overall showed age-related increases, when normalized by LV length, they showed higher values in infancy and middle age. The proportion of untwisting during isovolumic relaxation was lowest in infancy, increased during childhood, and leveled off thereafter, whereas peak untwisting performance (peak untwisting velocity normalized by peak LV torsion) showed a decrease during adulthood.

Conclusions— We have shown the maturational process of LV torsion in normal subjects. Net LV torsion increases gradually from infancy to adulthood, but the determinants of this were different in the 2 age groups. The smaller LV isovolumic untwisting recoil during infancy and its decline in adulthood may suggest mechanisms for alterations in diastolic function.

Doppler flow parameters of left ventricular filling in infants: how long does it take for the maturation of the diastolic function in a normal left ventricle to occur?

OBJECTIVE

To study the impact of the maturational process of diastolic left ventricular function on trans-mitral Doppler flow parameters.

METHODS AND PARTICIPANTS

In a survey we examined pulsed-wave Doppler signals and diastolic time intervals from 238 healthy neonates and infants. Using multiple linear regression analysis, we evaluated the impact of physiological determinants on parameter expression.

RESULTS

Early-filling and atrial-filling peak velocities, early-filling acceleration and deceleration rates, and the atrial-filling time velocity integral reached a climax within 2 months after birth, while early-filling time velocity integral followed increasing throughout the study period. The isovolumic relaxation time was found to be significantly longer for neonates than for infants older than 2 months. The observed parameter movements could be attributed to changes of stroke volume and mitral valve area for early filling-time velocity integral (R2 = 0.93), and of heart rate, stroke volume, and mitral valve area for early filling peak velocity (R2 = 0.84), and atrial-filling time velocity integral (R2 = 0.65). Isovolumic relaxation time and atrial-filling peak velocity became heart rate dependent not before 3 months after birth.

CONCLUSIONS

The observed parameter changes are powerful indicators for the maturational process in diastolic function. This process is mainly completed by 3 months of age.

Diastolic biomechanics in normal infants utilizing MRI tissue tagging

BACKGROUND

Most of what is known about diastolic function in normal infants is derived from flow and pressure measurements. Little is known about regional diastolic strain and wall motion.

METHODS AND RESULTS

Magnetic resonance tissue tagging was performed in 11 normal infants to determine regional diastolic strain and wall motion. Tracking diastolic motion of the intersection points and finite strain analysis yielded regional rotation, radial displacement, and E(1) and E(2) strains at 3 short-axis levels (significance was defined as P<0.05). E(2) "circumferential lengthening" strains were significantly greater at the lateral wall, regardless of short-axis level, whereas E(1) "radial thinning" strains were similar in all wall regions at all short-axis levels. In general, no differences were noted in strain dispersion within a wall region or in endocardial/epicardial strain at all short-axis levels. At all short-axis levels, septal radial motion was significantly less than in other wall regions. No significant differences in radial wall motion between short-axis levels were noted. Rotation was significantly greater at the apical short-axis level in all wall regions than in other short-axis levels, and it was clockwise. At the atrioventricular valve, septal and anterior walls rotated slightly clockwise, whereas the lateral and inferior walls rotated counterclockwise.

CONCLUSIONS

Diastolic biomechanics in infants are not homogeneous. The lateral walls are affected most by strain, and the septal walls undergo the least radial wall motion. Apical walls undergo the most rotation. These normal data may help in the understanding of diastolic dysfunction in infants with congenital heart disease.

Efficiency of left ventricular diastolic function increases in healthy full-term infants during the first months of life. A prospective follow-up study

Postnatal changes in left ventricular diastolic filling and systolic cardiac performance were studied monthly by serial echocardiographic measurements from days 3-5 up to six months in 20 healthy full-term infants. The fractional shortening area (FSA = (left ventricular end-diastolic area - end-systolic area)/end-diastolic area) was assessed for systolic performance, and transmitral pulsed-wave Doppler flow velocity patterns were analysed for diastolic function. FSA remained stationary during the observation. After birth, left ventricular peak early (E) and atrial (A) velocities and the respective integrals were lower than at one month of age (47+/-5 vs. 63+/-6 cm/s and 44+/-6 vs. 57+/-5 cm/s and 3.33+/-0.40 vs. 4.05+/-0.53 cm and 2.74+/-0.40 vs. 3.18+/-0.53 cm; P < 0.05). During the next five months, the early parameters (E velocity and E integral) increased but the atrial indices (A velocity and A integral) did not change. During the whole observation the E/A velocity ratio, the E/A integral ratio and the early filling fraction (EFF) increased. The early filling deceleration time was longer during the first month than later (87+/-10 vs. 72+/-13 ms; P < 0.05). In conclusion, age-related changes were observed in the diastolic but not in the systolic performance in healthy full-term infants during the first six months. The most intensive changes took place in the early and atrial transmitral parameters during the first month of life, suggesting an improvement in both left ventricular relaxation and compliance. During the following five months, the early mitral parameters increased but the atrial diastolic values remained stable. These changes may mainly be determined by the improvement in left ventricular relaxation.