Normal values for noninvasive estimation of left ventricular contractile state and afterload in children

Echocardiographic Normal Reference Ranges for Non-invasive Myocardial Work Parameters in Pediatric Age: Results From an International Multi-Center Study

Aims

This international multi-center study aimed to demonstrate the feasibility and reliability of non-invasive myocardial work (MW) parameters in the pediatric population, and to provide normal reference ranges for this useful echocardiographic tool in this specific subset of patients.

Methods and Results

In this retrospective multi-center study involving three pediatric laboratories, 150 healthy children and adolescents (mean age of 10.6 ± 4.5, 91 males) were enrolled. A complete echocardiographic examination has been performed, including global longitudinal strain (GLS) assessment. The following parameters of non-invasive MW have been obtained through a dedicated software: global work index (GWI), global constructive work (GCW), global work waste (GWW), and global work efficiency (GWE), using left ventricular (LV) strain loops and non-invasive brachial artery cuff pressure values. The lowest expected values were for GWI 1,723 mmHg% in males and 1,682 mmHg% in females, for GCW 2,089 and 2,106 mmHg%, for GWE 95.9 and 95.5% whereas the highest expected value for GWW was 78 mmHg% in men and 90 mmHg% in women. The univariable and multivariable analysis showed significant associations between either GWI or GCW with SBP (β coefficient = 0.446, p < 0.001; β coefficient = 0.456, p < 0.001, respectively) and LV GLS (β coefficient = −0.268, p = 0.001; β coefficient = −0.233, p = 0.003, respectively). Inter- and intra-observer variability showed good reproducibility of non-invasive MW parameters.

Conclusion

Non-invasive MW parameters were feasible and reliable in the pediatric population. This study provided normal reference ranges of these useful echocardiographic indices.

Pediatric systemic lupus erythematosus patients in South Africa have high prevalence and severity of cardiac and vascular manifestations

BACKGROUND

Pediatric onset of systemic lupus erythematosus (SLE) is associated with major organ involvement, and African patients tend to develop more aggressive disease than patients of European descent. Although cardiovascular involvement is common in pediatric SLE, there are few published reports on the subject. This study describes the frequency and characteristics of cardiac and vascular manifestations of pediatric SLE in a multi-ethnic South African cohort.

METHODS

Demographic, clinical, and echocardiographic data were collected from pediatric SLE patients at two centers in Cape Town, South Africa. At the time of investigation, this cohort consisted of 93 participants diagnosed with SLE according to international classification criteria prior to the age of 19. Individuals with cardiac and/or vascular involvement were identified by retrospective chart review. Cardiac manifestations were defined as presence of pericardial effusion, myocarditis, cardiomyopathy, cardiac failure, Libman-Sacks endocarditis, myocardial infarction, and arrhythmia. Vascular manifestations included deep vein thrombosis, pulmonary embolism, sinus thrombosis, stroke, critical limb ischemia, cerebral vasculitis and systemic vasculitis. Statistical analysis was performed using R (v3.4.1).

RESULTS

Cardiac and vascular involvement was present in 47% of the cohort. Previous studies have reported prevalence of 5%-50%. Demographic features of those with cardiac/vascular involvement did not differ from the overall cohort. Echocardiographic data were available for 23 participants. The most common cardiac manifestations were pericardial effusion (n = 24) and cardiac failure (n = 8), while the most common vascular manifestations were cerebral vasculitis (n = 9), stroke (n = 7), and pulmonary embolism (n = 7). Cardiovascular manifestations were frequently severe; one third of pericardial effusion cases required intervention, including three cases of cardiac tamponade. Cardiac and vascular involvement conferred an increased risk of mortality (31.1% versus 10.4%).

CONCLUSIONS

Cardiac and vascular involvement were highly prevalent in this South African cohort. The mortality rate was high, and severe manifestations were frequent. Prospective research is needed to improve knowledge of pediatric SLE in Africa and to improve outcomes for this high-risk population.

Atrial Functions and Aortic Elasticity in Children with Aortic Coarctation

BACKGROUND

Coarctation of the aorta (CoA) is a chronic vascular disease characterized by a persistence of myocardial and vascular alterations. We aimed to evaluate children who have had successful coarctation surgery or balloon dilatation to evaluate the elasticity of the aorta, left atrial ejection force (AEF) and myocardial performance collectively at midterm follow-up.

METHODS

Nineteen patients (7.15 ± 0.9 years of age) and 21 age-sex matched healthy children were included in this study. Left AEF index is defined as the product of mass and acceleration of blood expelled from the left atrium. Aortic stiffness and distensibility were estimated using ascending and descending aorta diameters.

RESULTS

The left atrial force index [(g∙cm/s(2))/m(2)] in the patient group was found to be significantly higher (12.69 ± 7.29, 5.74 ± 2.59, respectively, p = 0.001). Distensibility of the ascending aorta (cm(2)/dynes 10(-6)) was significantly lower in the patient group than in the control group (42.13 ± 24.02, 78.79 ± 20.49, respectively, p < 0.001). The stiffness index of the ascending aorta was significantly higher in the patient group (p < 0.001). We also documented that atrial force index is associated with peak E velocity, right arm systolic blood pressure and left ventricular mass index.

CONCLUSIONS

Our investigation showed that AEF is higher in children who have had successful coarctation surgery or balloon dilatation, and AEF is associated with systolic blood pressure, peak E velocity and left ventricular mass index. Distensibility of the ascending aorta was lower, and stiffness index was higher in children with corrected CoA than in healthy subjects.

KEY WORDS

Atrial ejection force; Balloon dilatation; CoA; Coarctation surgery; Distensibility; Stiffness index.

Rapid cardiovascular effects of growth hormone treatment in short prepubertal children: impact of treatment duration

OBJECTIVE

Previous studies show that growth hormone (GH) treatment increases cardiac dimensions in short children with GH deficiency (GHD) and has diverse cardiac effects in children with idiopathic short stature (ISS). This study was performed to assess the effect of GH on the cardiovascular system in short children with a broad range of GH secretion and GH sensitivity/responsiveness.

DESIGN AND PATIENTS

In this prospective, multicentre study, short prepubertal children diagnosed with isolated GHD (89) or ISS (38) were followed during 2 years of GH treatment. They were randomized to receive either a standard (43 μg/kg/day) or an individualized GH dose (range 17-100 μg/kg/day) based on GH responsiveness estimated by a prediction model and distance to target height. Echocardiography, blood pressure and electrocardiography were performed at baseline, 3, 12 and 24 months.

RESULTS

Left ventricular mass (LVM) indexed to body surface area increased significantly during 2 years of GH treatment in both GHD and ISS irrespective of randomized dose. This change was already apparent at 3 months, when standard deviation scores (SDS) of wall thickness and diameter were increased. At 24 months, left ventricular diameter SDS remained increased, whereas myocardial thickness SDS returned to baseline values. There was no impairment of systolic or diastolic function. There was no correlation with treatment dose and LVM SDS at 24 months.

CONCLUSIONS

Irrespective of GH status, there was a rapid increase in LVM during GH treatment in short children. At 3 months, wall thickness and diameter were increased, whereas only diameter remained increased at 24 months.

Contractility reserve in children undergoing dialysis by dobutamine stress echocardiography

Left ventricular hypertrophy is an adaptive mechanism in children undergoing chronic dialysis to improve contractility at rest. The aim of this study was to determine the left ventricular performance and contractility reserve by "dobutamine stress echocardiography" in children undergoing chronic dialysis. Thirty-five children undergoing dialysis and 24 healthy subjects were enrolled in this prospective study. We evaluated contractility by means of end-systolic wall stress-velocity of circumferential fiber shortening (VCFc) in 24 healthy subjects and 35 dialysis patients. Dobutamine stress echocardiography was obtained only in children undergoing dialysis. Patients were divided into two groups according to left ventricular mass index. Contractile reserve was estimated by the difference in contractility at rest versus during echocardiography. Significantly higher VCFc (p = 0.008) and VCFc (p = 0.002) differences at rest were observed in the patient group compared to healthy subjects. Children undergoing dialysis had a higher left ventricular mass index compared with controls (42.38 ± 12.41 vs. 17.57 ± 3.66 g/m(2.7), respectively; p = 0.001). Patients with left ventricular hypertrophy had a significantly lower contractile reserve compared with patients without left ventricular hypertrophy (p = 0.013). These findings suggest that children undergoing dialysis have increased left ventricular mass and contractility at rest. However, the contractile reserve during dobutamine stress echocardiography was reduced. Dobutamine stress echocardiography may identify children undergoing dialysis at risk of progressing to systolic dysfunction and heart failure.

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.

Predictors of outcome of myocarditis

Heart failure from myocarditis may be transient or may progress to unremitting severe cardiac failure. This study was performed to determine the outcomes and prognostic features of pediatric patients with myocarditis. Patients with the diagnosis of myocarditis between 1990 and 2001 were identified through the coding system of Yale-New Haven Hospital. A total of 28 patients were included, with ages ranging from 1 day to 20 years. Before discharge, 11 patients developed unremitting severe cardiac failure. Of the remaining 17 patients, at the time of discharge 10 had normal systolic function and 7 had decreased systolic function. Unremitting cardiac failure developed in 9 of 14 patients (64%) with an ejection fraction < 30% and in only 2 of 14 (14%) of those with an ejection fraction > or = 30% on admission (p < 0.01). Furthermore, shortening fraction < 15%, left ventricular dilatation, and moderate to severe mitral regurgitation on admission as well as arrhythmia were significantly associated with development of unremitting severe cardiac failure. In this series of patients with myocarditis, by the time of discharge 39% of the patients had developed unremitting severe cardiac failure, 25% had depressed systolic function, and 36% had normal systolic function. Predictive factors at admission for poor outcome were ejection fraction < 30%, shortening fraction < 15%, left ventricular dilatation, and moderate to severe mitral regurgitation.

Myocardial contractility in premature neonates with and without patent ductus arteriosus

Controversy exists as to whether a hemodynamically significant left-to-right shunt due to a patent ductus arteriosus (PDA) affects ventricular contractility. Load-dependent indices such as ejection fraction and shortening fraction have traditionally been used to assess contractility, but the relationship between the rate-corrected velocity of fiber shortening (MVCFc) and wall stress may be more suitable, as it is a preload-independent, afterload-adjusted method of assessing ventricular contractility. Age-related differences have been established for these variables in normal adults and children and it has been recommended for use in the premature neonate. The study was performed to assess left ventricular contractility in premature neonates with a significant left-to-right shunt due to a PDA. Using echocardiography, we measured the relationship of MVCFc to stress at peak systole (SPS) in two groups of premature infants. Group 1 consisted of 15 controls (680-1495 g, 25-32 weeks' gestation), and Group 2 of 15 neonates with hemodynamically significant PDA (840-1635 g, 26-33 weeks' gestation). In both groups, MVCFc was linearly and inversely related to SPS ( p < 0.001). The regression equations were as follows: Group 1, MVCFc = -0.0153SPS + 1.70 ( R(2) = 0.68); and Group 2, MVCF = - 0.019SPS + 1.89 ( R(2) = 0.76). There was no significant difference in the relationship between the two groups, but their slopes were significantly steeper and had a higher Y-intercept than the relationship we previously reported for older children. This preliminary study establishes the normal MVCFc/SPS relationship in the premature neonate (25-33 weeks' gestation) and suggests that premature infants function at a higher resting contractile state than older children. A hemodynamically significant PDA has no effect on contractility. These data will be useful in assessing left ventricular contractility in premature neonates with other types of ventricular loading and noncardiac stress.

Left ventricular remodelling, and systolic and diastolic function in young adults with beta thalassaemia major: a Doppler echocardiographic assessment and correlation with haematological data

OBJECTIVE

To evaluate left ventricular morphology and function in a large population of patients with beta thalassaemia.

DESIGN

Echo Doppler assessment of left ventricular function and correlation of cardiovascular data with haematological data.

SETTING

Thalassaemia unit in a tertiary referral centre.

PATIENTS

197 young adults with beta thalassaemia, following an adequate transfusional and chelation treatment regimen, without clinical signs of cardiopulmonary involvement. The control group consisted of 213 healthy subjects.

RESULTS

Left ventricular volumes, mass index, and mass/volume ratio were increased. Diastolic and systolic shapes were different, the left ventricle maintaining an ellipsoidal shape. The ejection fraction was reduced, and was < 50% in 33 patients. Stroke volume and cardiac index were increased, and systemic vascular resistance was decreased. Fractional shortening and mean velocity of circumferential shortening were decreased. Meridional end systolic and peak systolic stress were increased, as was circumferential end systolic stress. The contractile state was reduced while the functional preload index did not differ. Left ventricular diastolic function, evaluated from the mitral inflow, showed a slightly prolonged isovolumic relaxation time, increased flow velocity integrals, and an increased E/A ratio. Among the haematological data, only serum ferritin showed a weak negative correlation with left ventricular ejection fraction. The patients with the highest serum ferritin (> 2500 ng/ml) had the lowest ejection fraction.

CONCLUSIONS

Patients with beta thalassaemia on an adequate transfusion and chelation treatment regimen show abnormal left ventricular remodelling with increased volumes, mass, and mass/volume ratio. Systolic chamber function and contractile state are reduced, with a slightly increased afterload. These findings seem mainly to be related to the increased cardiac output caused by chronic anaemia. Left ventricular performance is better preserved when chelation treatment is adjusted to maintain the serum ferritin concentration at < 1000 ng/ml.

Left ventricular remodeling, systolic function, and diastolic function in young adults with beta-thalassemia intermedia: a Doppler echocardiography study

BACKGROUND

The aim of this study was to investigate the left ventricular (LV) remodeling and function in 24 asymptomatic young adults affected by beta-thalassemia intermedia (TI), in order to compare the obtained data with that of 80 patients affected by beta-thalassemia major (TM) and 65 healthy subjects.

METHODS

LV volumes and shapes, mass index, mass/volume ratio, systolic and diastolic function, stroke volume, and cardiac index were determined by two-dimensional and M-mode echocardiography.

RESULTS

In the TM and TI groups, LV volumes, diastolic and systolic shapes were significantly different from the control subjects, but the ejection fraction was slightly reduced only in the TM group. The TI group had larger LV volumes than did the TM group (mean [+/- SD] end-diastolic volume index, 99.4 +/- 21.9 vs 82.7 +/- 21.5 mL/m(2), respectively [p < 0.005]; mean end-systolic volume index, 42.8 +/- 12.2 vs 36.1 +/- 12.9 mL/m(2), respectively [p < 0.05]). Both groups showed an increase of the LV mass index, but the mass/volume ratio did not differ from the control subjects. The systolic volume index and the cardiac index were increased in both groups, but the increase was more pronounced in the TI group. Fractional shortening (FS) and the mean velocity of circumferential shortening (mVCFc) were decreased in the TM group (FS, 33.6 +/- 5.5% vs 36.9 +/- 4.1, respectively [p < 0.001]; mVCFc, 1.06 +/- 0.18 vs 1.17 +/- 0.12 circumference per second, respectively [p < 0.0001]). The LV contractile state was depressed only in the TM group, and the preload index was normal in both. LV filling showed an increase in the total flow velocity integral due to increases in the peak E wave (E) and peak A wave (A) velocities and integrals, with an increase of the E/A ratio in the TM group and a slight decrease in the TI group. The isovolumic relaxation time was prolonged in both groups. There was no major derangement in the pulmonary venous flow.

CONCLUSIONS

Asymptomatic young adults with TI show significant increases in LV volumes, LV mass, and cardiac index that are more pronounced than those in TM patients. LV systolic function is preserved in the TI group but is slightly depressed in the TM group due to the increase of afterload and to reduced contractility. The hemodynamic and hematologic factors involved in the etiopathogenesis of these findings are discussed, such as the treatment strategy.

Plasma levels of natriuretic peptides in relation to doxorubicin-induced cardiotoxicity and cardiac function in children with cancer

BACKGROUND

Anthracyclines are effective anticancer drugs for childhood cancer with dose-limiting cardiotoxicity. Children who have received anthracyclines thus need periodical cardiac evaluation. The plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) have been shown to increase in proportion to severity of cardiac dysfunction. We examined whether plasma levels of ANP and BNP, in addition to echocardiographic evaluation, can be used as specific markers for doxorubicin-induced cardiotoxic effects in children.

PROCEDURE

Consecutively, 34 patients (18 boys and 16 girls) who had previously received doxorubicin-containing chemotherapy were enrolled in this study. Plasma ANP and BNP were assayed simultaneously at the time of first cardiac function evaluation by echocardiography.

RESULTS

Of the 34 patients, 8 (23.5%) had left ventricular dysfunction as assessed by echocardiography. Both ANP and BNP plasma levels in these patients were significantly elevated in comparison with healthy controls (P < 0.01) or patients with normal cardiac function (P < 0.05). It should be also noted that ANP and BNP levels were correlated significantly with cardiac systolic function, but not with diastolic function.

CONCLUSIONS

These results suggest that plasma ANP and BNP levels could be markers for doxorubicin-induced cardiotoxicity in children. Measurement of natriuretic peptide levels during treatment may allow earlier-identification of individuals at risk for severe cardiac damage.

Normal values of regional left ventricular endocardial motion: multicenter color kinesis study

Our goal was to establish normal values for quantitative color kinesis indexes of left ventricular (LV) wall motion over a wide range of ages, which are required for objective diagnosis of regional systolic and diastolic dysfunction. Color-encoded images were obtained in 194 normal subjects (95 males, 99 females, age 2 mo to 79 yr) in four standard views. Quantitative indexes of magnitude and timing of systolic and diastolic function were studied for age- and gender-related differences. Normal limits of all ejection and filling indexes were in a narrow range (< or =25% of the mean), with no major gender-related differences. Despite invariable ejection fractions, both peak filling and ejection rates decreased with age (30 and 20%, correspondingly) with a concomitant increase in mean filling and ejection times, resulting in five- and twofold increases in the late to early filling and ejection ratios, correspondingly. Diastolic asynchrony increased with age (from 4.7 +/- 2.0 to 6.4 +/- 3.2 from the 2nd to 7th decade). The normal values of color kinesis indexes should allow objective detection of regional LV systolic and diastolic dysfunction.

The influence of low afterload on the nature of the stress-velocity relationship

OBJECTIVES

Correct assessment of contractility by conventional methods during manipulation of afterload is often disappointing. To this purpose, the stress-velocity relationship offers assessment of contractility at different levels of afterload. We decided to study the influence of afterload on the nature of the stress-velocity relation.

BACKGROUND

Although linear at baseline conditions in a population older than two years, data in newborns or after administration of low-dose dobutamine suggest a different nature of this relationship at low afterload.

METHODS

Ten healthy piglets (five to six weeks; 11 to 13 kg) were studied. End-systolic meridional wall stress (ESWS) and rate-corrected velocity of circumferential fiber shortening (VcFc) were measured in these piglets at baseline, after balloon occlusion of the descending aorta, and at nitroprusside infusion rates of 1, 2 and 5 microg/kg/min. To eliminate inotropic influences mediated by reflex tachycardia, we subsequently studied five piglets and six adult pigs after bilateral cervical vagotomy.

RESULTS

The ESWS changed from a baseline mean of 50 g/cm2 to 137 g/cm2 after balloon occlusion and to 19 g/cm2 at 5 microg/kg/min of nitroprusside. The VcFc changed from 1.19 c/s (circumference/second) to values of 0.9 c/s and 1.73 c/s, respectively. The ensuing stress-velocity regression line proved to be curvilinear instead of linear. The steeper slope at low afterload could suggest enhanced contractility compared to expected values had the relationship been linear.

CONCLUSIONS

Data from young piglets and adult pigs suggest a curvilinear relationship of the stress-velocity relationship. This could probably explain some of the "hypercontractile states" encountered in conditions with low afterload.

Pediatric echocardiography: applications and limitations

Echocardiography is an extraordinarily useful imaging technique in fetuses, infants, children, and adolescents. Recent technologic innovations have expanded its versatility in the pediatric population. However, limited societal resources, limitations inherent to ultrasound imaging, and numerous imaging options even within the field of pediatric echocardiography necessitate the discriminate and thoughtful use of echocardiography in children. The clinical assessment remains a critical prelude to echocardiographic examination of the pediatric cardiovascular system.

Late effects of chemotherapy compared to bone marrow transplantation in the treatment of pediatric acute myeloid leukemia and myelodysplasia

BACKGROUND

As more pediatric patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) survive, comparison of the late effects of various therapies becomes increasingly important. This study of survivors of AML is the largest to date comparing the late effects of patients treated with chemotherapy (CT) with or without irradiation (RT) or CT followed by bone marrow transplantation (BMT).

PROCEDURE

In a retrospective review of 228 patients with AML or MDS from 1970 to 1995, 62 survived and had follow-up data available more than 1 year following completion of therapy. Ten patients with Down syndrome were excluded. Twenty-six received CT and 26 underwent BMT. Weight and height Z scores, endocrine, ophthalmologic, renal, and cardiac function following CT +/- RT or BMT +/- total body irradiation (TBI) were compared at a mean follow-up of 7.4 and 5.6 years, respectively.

RESULTS

Both groups experienced a decrement in height and increase in weight. The mean height Z score in the CT group fell from -0.29 to -0.72 (P = 0.02) and mean weight Z score rose from -0.06 at diagnosis (T0) to 0.51 at last follow-up (T2) (P = 0.02), a finding no longer significant when patients who received RT were excluded. The mean height Z score in the BMT group fell from -0.17 at TO to -0.65 at T2 (P = 0.02), while the mean weight rose from 0.29 at T0 to 0.84 at T2, (P = 0.07). Six of 9 BMT adolescent girls experienced ovarian failure versus 0 of 11 girls treated with CT (P = 0.002). Seven adolescent CT males and seven BMT males showed normal pubertal progression. Two BMT patients require thyroid hormone supplementation, and one receives growth hormone. Six BMT patients and one CT patient developed cataracts, all of whom received irradiation (P = 0.10). Serum creatinine level, hypertension, or left ventricular shortening fraction were not different in the two groups. One BMT patient has chronic graft versus host disease.

CONCLUSIONS

Growth, renal, and cardiac functions were similar in the two groups. The need for estrogen supplementation was more frequent following BMT. Recommendations concerning therapy for AML should depend on the probability of cure.

Influence of age and low afterload on the stress-velocity relation of the left ventricle

The relation between systolic meridional wall stress (WS) and velocity of circumferential fiber shortening (VcFc) is widely accepted as a preload-independent index of contractility, with a linear relation in most subjects older than 2 y. However, this relation seems to become different in infants and after administration of inotropic agents. We decided to study the nature of the stress-velocity relation by a cross-sectional assessment of the influence of age, low afterload, and increased contractility. Study subjects were 30 healthy infants, 32 healthy older children, and 35 asymptomatic older children after completion of anthracycline chemotherapy. WS and VcFc at rest were studied in these infants and children. WS and VcFc were also studied after dobutamine infusion in both groups of older children. Linear regression analysis of the stress-velocity relation showed parallel slopes between the older children at rest and the post anthracycline children after dobutamine. The regression lines between the infants at rest and the healthy older children after dobutamine were also parallel, but with a different and steeper slope compared with the former groups. When comparing the stress-velocity relation of the overall population at rest with the overall population after dobutamine, the resulting regression lines are curvilinear and parallel, with a steeper slope at low afterload. The stress-velocity relation in infants and after dobutamine, resulting in low afterload is different compared with the stress- velocity relation in older children at rest and at higher afterload. Data of the overall population at rest and after dobutamine suggest a curvilinear relation.

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

Age-related changes in left ventricular diastolic filling have been reported to occur in normal children in studies using Doppler echocardiographic methods. However, little information currently exists on the relationships between transmitral flow velocity patterns and the left ventricular mass. We measured left ventricular end-diastolic volume, left ventricular mass, mass/volume ratio, and transmitral flow velocity patterns by M-mode and Doppler echocardiography in 165 normal children aged 5 days to 195 months. Subjects were divided into 6 age groups: <1; 1 to <3; 3 to <5; 5 to <7; 7 to <9; and > or = 9 years old. The left ventricular end-diastolic volume and mass increased progressively with increasing age. However, the mass/volume ratio in infants <1 year was significantly higher than that in infants 1 to <3 years (1.32+/-0.25 vs. 1.14+/-0.16, p<0.01) without any changes of the ratio thereafter. The peak E wave in infants <1 year was significantly lower than that in 1 to <3 years (71+/-18 vs. 92+/-13 cm/s, p<0.01) without changes thereafter. As the flow velocity time integral of E wave increased and that of A wave remained constant, the flow velocity time integral of E/A wave increased with increasing age. The early diastolic tilling fraction in infants <1 year was lower than that in infants 1 to 3 years. (0.61+/-0.07 vs. 0.70+/-0.06, p<0.01). The atrial filling fraction in infants <1 year was higher than that in infants 1 to <3 years (0.40+/-0.08 vs. 0.30+/-0.06, p<0.01) with a little decrease thereafter. The peak E wave, early diastolic tilling fraction, and the atrial filling fraction correlated with the logarithm of age (p<0.01). Age-related changes in these Doppler echocardiographic findings suggest reduced left ventricular early diastolic filling patterns. The mass/volume ratio correlated linearly with peak E wave, early diastolic filling fraction, and atrial filling fraction (r=-0.38, -0.33, and 0.26, p<0.01). No significant relationships between mass/volume ratio and the other Doppler indices were found. Thus, the age-related reduction in the mass/volume ratio may be one of the mechanisms underlying age-related changes in the early diastolic ventricular filling as assessed by Doppler echocardiography.

Peak systolic stress-rate-corrected mean velocity of fiber shortening in preterm and fullterm infants

The relation of rate-corrected mean velocity of fiber shortening (mVcfc)-end-systolic wall stress (ESS) is a load-independent index of left ventricular contractility, but involves simultaneous M-mode echocardiography, carotid or axillary pulse tracing and blood pressure determination, which may be impractical in younger infants. We examined whether the relation of the peak systolic wall stress (PSS)-mVcfc could be used as a simpler method of assessing left ventricular contractility in preterm and fullterm infants. In 45 preterm and fullterm infants, mVcfc, ESS, and PSS were determined using echocardiography, axillary pulse tracing and blood pressure measurement. Five patients with left ventricular dysfunction or low cardiac output state were also studied. The relation of PSS and ESS was PSS=5.19+1.04 ESS (r=0.98, p<0.01). The slope of mVcfc=1.58-0.012 ESS (r=-0.78, p<0.01) was nearly identical to that of mVcfc=1.60-0.011 PSS (r=-0.75, p<0.01), with no difference in the regression coefficients. The relationship of PSS and ESS in 5 patients was very close and the slope of the regression line was nearly identical to that of 45 infants. The relation of mVcfc PSS correlates well with the relation using ESS and can be used as a simple method of assessing left ventricular contractility.

Short- and long-term variability of echocardiographic stress-velocity indexes of cardiac function in a pediatric population

This study determined the short- and long-term variability of stress-velocity relationships at end systole and peak systole. A prospective study during the short term (0 to 15 and 0 to 30 minutes) and long term (0 to 1 and 0 to 12 months) was performed calculating variability by the limits of agreement method. The study was performed in a tertiary-care pediatric echocardiographic laboratory. Twenty-five normal children underwent repeat testing as described. Standard blood pressure, carotid pulse tracing, and M-echocardiography of the left ventricle was performed at the intervals described. The rate-corrected mean velocity of fiber shortening (MVCFC), echocardiographic stress at end systole (SES), and echocardiographic stress at peak systole (SPS) were calculated for all recordings. The slopes of MVCFC-SES and MVCFC-SPS were determined by regression and plotted. With these slopes, the second and third stress values were normalized to the first stress value for the short and long term. The differences in normalized MVCFC and MVCFC (delta MVCFC) for 15 to 0 minutes, 30 to 0 months, 1 to 0 month, and 12 to 1 month were obtained for both SES and SPS, and 95% limits of agreement were estimated. The mean delta MVCFC for SES and SPS for the short and long term were not different from 0 or each other, indicating no bias. The 95% limits of agreement of delta MVCFCs (i.e., variability for SES at 15 to 0 minutes, 30 to 0 minutes, 1 to 0 month, and 12 to 0 month) were +/- 0.18, +/- 0.24, +/- 0.34, and +/- 0.27, respectively, and for SPS +/- 0.18, +/- 0.24, +/- 0.33, and +/- 0.28. Variability showed an increasing trend with time but was significant only from 15 to 0 minutes and 1 to 0 month (p = 0.006). This study has established short- and long-term variability in the stress-velocity relationship that is essential for monitoring acute and chronic changes in ventricular contractility in an individual patient.

Cardiovascular effects of high-dose growth hormone treatment in growth hormone-deficient children

Growth hormone (GH) hypersecretion is associated with an increased incidence of cardiac hypertrophy and subclinical abnormalities of left ventricular (LV) function. The unlimited availability of biosynthetic GH has led to progressively increased dosage when treating GH-deficient children, raising the question of its cardiovascular effects during long-term therapy. We compared 22 children (8 girls, 14 boys), mean age 12.1 years (range 3-17 years) with GH deficiency who were receiving chronic GH treatment (GH group) with 22 normal controls matched for sex and body size in order to evaluate: (1) LV volume, mass, and systolic function by two-dimensional guided M-mode echocardiography; (2) LV diastolic function by pulsed-wave Doppler sampling of the transmitral flow; and (3) cardiac output and systemic vascular resistance by Doppler echocardiography. All patients had been on chronic GH therapy for 13.8 +/- 7.6 months (range 5-30 months) with an average dose of 0.95 +/- 0.12 IU/kg per week (range 0.69-1.17 IU/kg per week). Blood pressure did not differ between the two groups. LV volume, mass, ejection fraction, and mean velocity of circumferential shortening did not differ significantly between the GH group and controls; nor did the peak- and end-systolic meridional stress. All patients had a normal contractile state as estimated by the relation between mean velocity of circumferential shortening and end-systolic meridional stress. The LV filling parameters did not differ between the two groups, and there was no difference in cardiac index and systemic vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of myocardial contractility, preload, and afterload in healthy newborn infants

Assessment of ventricular contractility in the newborn infant using standard echocardiographic indexes can result in error due to the unique physiologic state that exists in the neonatal period. It has been suggested from animal and human studies that maturational alterations in contractility occur with birth and continue throughout infancy. To further investigate these developmental changes, 41 newborn infants aged 3 to 10 days and 37 children aged 3 to 18 years were evaluated with 2-dimensional and M-mode echocardiography. The rate-corrected velocity of circumferential fiber shortening (VCFc)-end-systolic wall stress (ESWS) relation was used as a load-independent estimate of contractility. Preload, afterload, and ventricular mass were also measured. Despite similar shortening fractions, the infant group had significantly higher mean VCFc and lower ESWS than the older age group (1.28 vs 1.08 circ/s and 30.2 vs 37.3 gm/m2, respectively). An inverse linear relation between VCFc and ESWS was found in both age groups. The y-intercept was higher in the infant group (p < 0.01), and the slope of the mean regression line was steeper than in the older children (p < 0.01). Ventricular mass in relation to body surface area increased with age. We conclude that (1) newborn infants have a higher basal contractile state that cannot be accounted for by lower afterload, (2) myocardial performance is more sensitive to afterload in the immature heart, and (3) shortening fraction may underestimate ventricular function in the newborn.

Left ventricular contractile state in preterm infants: relation between wall stress and velocity of circumferential fiber shortening

Fetal and newborn lambs' hearts have limited capacity to adapt to increased afterload. In human preterm infants, however, this limited left ventricular pump function has not been investigated. To determine the normal left ventricular resting contractile state in preterm infants, we studied the relation of end-systolic wall stress to the rate-corrected velocity of circumferential fiber shortening (VCF) in 11 preterm infants of gestational ages 28 to 36 weeks. We performed the first (7 to 14 days of postnatal age) and the second (29 to 39 days of postnatal age) examinations. There was a significant inverse linear correlation between wall stress and VCF in the first and the second examinations (r = -0.616 and r = -0.715, respectively). Both regression lines had slopes that were steeper than those previously reported for older age groups. The preterm infants had high VCF values (mean 1.05 and 1.09 cir/sec, respectively) and low-wall stress values (mean 36.0 and 36.9 gm/cm2, respectively) in the first and the second examinations. We therefore suggest that the preterm infants have a high resting contractile state, but left ventricular performance may deteriorate in the face of increased afterload.

Left ventricular performance in neonates on extracorporeal membrane oxygenation

The evaluation of left ventricular systolic performance in infants undergoing extracorporeal membrane oxygenation (ECMO) using traditional ejection-phase indices is hampered by significant alterations in preload and afterload. Therefore, a load-independent index, which relates heart-rate-corrected mean velocity of circumferential fiber shortening (VCFc) to afterload, measured as end-systolic wall stress (ESS), was used to assess left ventricular function in 18 term neonates undergoing ECMO. The mean age at the onset of ECMO was 75.5 h and the duration of therapy was 171 +/- 106 h. Left ventricular performance was highest before the onset of ECMO (VCFc = 1.65 +/- 0.49 circ/s) and decreased toward normal during (1.38 +/- 0.33 circ/s) and following ECMO (1.29 +/- 0.16 circ/s). Initially, nine of 17 (53%) patients had enhanced performance for the degree of afterload but in only 16 of 48 (33%) studies during ECMO and none following ECMO was VCFc elevated beyond the normal range predicted for ESS. These changes in left ventricular performance may be the result of variations in exogenous, as well as endogenous, catecholamines rather than intrinsic alterations in myocardial contractility. It is concluded that the VCFc/ESS relation permits a meaningful assessment of ventricular performance in critically ill neonates undergoing ECMO.

Developmental modulation of myocardial mechanics: age- and growth-related alterations in afterload and contractility

Somatic growth is associated with alterations in myocardial mechanics in children with heart disease and in most animal models of congenital heart disease. However, the effect of age and body size on myocardial contractility and loading conditions in normal infants and children is not known. Therefore, 256 normal children aged 7 days to 19 years (34% less than 3 years old) were evaluated with noninvasive indexes of left ventricular contractility and loading conditions. Two-dimensional and M-mode echocardiographic recordings of the left ventricle were obtained with a phonocardiogram, indirect pulse tracing and blood pressure recordings. Left ventricular dimensions, wall thickness and pressure measurements obtained from these data were used to calculate peak and end-systolic circumferential and meridional wall stress and mean and integrated meridional wall stress. Velocity of shortening adjusted for heart rate was compared with end-systolic stress to assess contractility independently of loading status. The subjects were stratified for gender and each of the derived variables was related to age and body surface area. Ventricular shape, assessed as the major/minor axis ratio, and the circumferential/meridional stress ratio were found to be invariant with growth. The ratio of posterior wall thickness to minor axis dimension did not change with age, despite the normal age-related increase in blood pressure. The increase in pressure despite unvarying ventricular shape and wall thickness/dimension ratio resulted in a substantial increase in wall stress that was most dramatic during the first few years of life. In association with the increase in afterload, systolic function decreased with age. However, the age-related decrease in the velocity of shortening was greater than that expected from the increase in afterload alone, indicating a higher level of contractility in infants and children during the first years of life than in older subjects. The process of normal growth and development, similar to that in children with heart disease, is associated with a rapid decrease in the trophic response to hemodynamic loads, resulting in an age-associated increase in wall stress. There is a similar but somewhat more rapid decrease in contractility, with the highest values seen in the youngest patients.

Rate-corrected mean velocity of fiber shortening-stress at peak systole as a load-independent measure of contractility

The relation of mean velocity of fiber shortening-stress at end-systole is a good load-independent index of left ventricular contractility, but involves simultaneous M-mode echocardiography, carotid tracing and blood pressure determination, which may be impractical in children. As stress at peak systole and end-systole are closely related, this study examined whether the relation of mean velocity of fiber shortening-stress at peak systole could be used as a simpler method of assessing left ventricular contractility in a normal population of children. In addition, the cross-sectional normal range for a pediatric population was obtained. In 25 normal children aged 4 to 17 years (mean age 11), rate-corrected mean velocity of fiber shortening (MVCFc), stress at peak systole (sigma PS), and end-systolic stress (sigma ES) were determined using echocardiography, carotid pulse tracing and blood pressure measurement. Six patients with cardiomyopathy (mean age 8 years) were also studied. The relation of stress at peak systole and end-systolic stress was sigma PS = 1.004 sigma ES + 12.0 (r = 0.91, SEE = 4.98; p less than 0.001) for the normal group, and sigma PS = 1.083 sigma ES + 7.7 (r = 0.99, SEE = 4.07; p less than .001) for the cardiomyopathic group. This slope of the regression line was slightly higher and the difference was statistically significant. The slope of MVCFc = 0.0066 sigma PS + 1.55 (SEE = 0.131, r = -0.52) was nearly identical to that of MVCFc = 0.0065 sigma ES + 1.46, (SEE = 0.135, r = -0.46), with no difference in the regression coefficients.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related variation in contractility estimate in patients less than or equal to 20 years of age

The relation between velocity of circumferential fiber shortening (VCF) and wall stress (WS) is being used to estimate contractile state in a variety of disease states and patient ages more frequently. However, its relation to age has not been established. To determine reproducibility and age and sex dependence of this relation, 204 normal children (113 boys, 91 girls) underwent echographic determination of VCF and WS. The children were enrolled in 3 groups: group 1 less than 6 months old (n = 27); group 2 greater than 6 months and less than 3 years old (n = 38); and group 3 greater than 3 and less than 20 years old (n = 139). Twenty-five children also underwent serial echocardiography (n = 44) to determine reproducibility of the relation. Only 1 of the 44 repeat data pairs of VCF and WS was outside the 95% confidence limits of that relation. In all 3 groups, VCF was significantly inversely and linearly related to WS (p less than 0.001). The regression equation in the oldest group was very similar to previous reports (VCF = -0.0031 [WS] + 1.21). The regression lines in the 2 younger groups were significantly steeper and had a significantly higher y-intercept (p less than 0.01). Group 1 had the steepest slope and highest y-intercept. There was no difference in the regression lines of different sexes in any of the patient groups. It is concluded that the relation of VCF to WS is reproducible over time. It is age-dependent but has no relation to gender. VCF in patients less than 6 months old is more highly dependent on WS.(ABSTRACT TRUNCATED AT 250 WORDS)