Sudden cardiac death in the young athlete.

Sudden cardiac death in athletes is usually due to underlying cardiovascular disease. In the young less than 30 years of age, the most common abnormality is hypertrophic cardiomyopathy, followed by congenital coronary artery anomalies. The final common pathway is usually ventricular fibrillation. Sudden cardiac death in the young is rare but remains a source of concern. A careful screening history and physical examination, especially for potential athletes, should identify the majority of young people at risk.

Tracking of left ventricular mass in children: race and sex comparisons: the MCV Twin Study. Medical College of Virginia.

BACKGROUND: Increased left ventricular (LV) mass is a predictor of cardiovascular disease in adults. The mechanism(s) for these observations are not fully understood. METHODS AND RESULTS: We repeatedly studied a biracial sample of children from ages 11 through 17 years. At visits 1 through 5, height, weight, and pubertal stage were determined. Blood pressure and heart rate were measured. M-mode and two-dimensional echocardiograms were performed with a 3.5-MHz transducer with the subject in the supine position. LV mass was calculated. Repeated-measures analysis using a mixed modeling approach was performed for LV mass. At all ages, boys had greater LV mass than girls. For the population as a whole, we found significant tracking correlations for LV mass between each interval of measurement and throughout the entire period of examination. The tracking correlation for the entire sample from visit 1 through visit 5 was r=.41. The LV mass in white children tracked from the youngest to the oldest. Black children tracked similarly from ages 1 to 15 years, but tracking was not significant across the widest interval, visit 1 through visit 5. Racial differences were found in the interactions of systolic blood pressure and heart rate, which magnified the differences in LV mass. During adolescence, LV mass tracks significantly in both black and white children. CONCLUSIONS: Interactive effects such as weight, blood pressure, and heart rate magnify sex and race differences in LV mass.

Genetic influences on ambulatory blood pressure patterns. The Medical College of Virginia Twin Study.

The genetic influence of ambulatory blood pressure and heart rate was examined in 38 pairs of monozygotic twins, 17 pairs of same-sex dizygotic twins, and 11 pairs of opposite-sex dizygotic twins, all aged 15 or 17 years. The data were analyzed taking into consideration that the response was multivariate (24-h values) instead of the usual univariate response. The results demonstrated the heritability of ambulatory blood pressure and heart rate. This was true regardless of whether the estimate of heritability involved monozygotic twin pairs compared to same-sex dizygotic twin pairs only, or all dizygotic twin pairs. The time-related intraclass correlation coefficient within each twin classification indicated that the patterns of response within twin pairs correlated more for monozygotic twin pairs than within twin pairs for either set of dizygotic twin pairs. In addition, although the opposite-sex dizygotic twin pairs may have different mean levels of response, they exhibit a similarity of patterns of response akin to that seen within same-sex dizygotic twin pairs.

Altered blood pressure reactivity in adolescent diabetics.

OBJECTIVE: We examined hemodynamic responses to a variety of physiologic stimuli in 14 normotensive adolescents with type I diabetes and 45 healthy controls to determine whether structural vascular changes contribute to a reduced vasodilator capacity in adolescent diabetics. We asked, in adolescents with type I diabetes: (1) Are structural vascular changes present? (2) Are changes in the systemic vascular bed reflected in abnormal blood pressure regulation? and (3) Is abnormal vascular reactivity associated with either diabetes duration or control? METHODOLOGY: Diabetic subjects were outpatients treated at the Medical College of Virginia, ages 13 to 18 years. Diabetes duration averaged 7.5 years. Each subject underwent an echocardiogram, dynamic and isometric exercise testing, and forearm plethysmography. RESULTS: Compared to controls, diabetic subjects had (1) higher systolic and diastolic blood pressure during dynamic and handgrip exercise, (2) decreased forearm vasodilator capacity in response to ischemia, and (3) an increased aortic peak velocity. Group diastolic filling abnormalities were found, but these did not persist after adjustment for heart rate. The following variables were related to both diabetes duration and control (average glycosylated hemoglobin): (1) diastolic blood pressure during dynamic exercise, (2) resting forearm vascular resistance, and (3) forearm vascular reactivity. In addition, diabetes duration correlated with isometric exercise diastolic blood pressure, and diabetes control correlated with resting diastolic blood pressure. CONCLUSION: In young diabetics we found that (1) abnormalities of the resistance vessels of the forearm may be present, (2) the degree of vascular change is related to diabetes duration and control, and (3) aortic distensibility may be impaired.

Acute monoblastic leukemia presenting with pericardial effusion and cardiac tamponade.

A previously healthy young child presented with a large pericardial effusion and cardiac tamponade. The chest radiography was key to the recognition of the pericardial effusion. Cytologic examination of the pericardial fluid ultimately established the diagnosis of acute monoblastic leukemia in the absence of associated clinical or laboratory findings. The pericardial fluid was vital for leukemic cell classification because the bone marrow has hypocellular and non-diagnostic. This presentation of acute monoblastic leukemia is very rare, and in the three previously reported pediatric cases has been associated either with peripheral blasts or a history of preleukemia. When the cardiac configuration suggests pericardial effusion in a previously healthy young child, the diagnosis of new onset leukemia should be considered.

Hypertension in infancy.

Hypertension in infants is rare and requires a thorough evaluation. The incidence of hypertension in infancy has risen in recent years, reflecting both better monitoring methods and increasingly successful salvage of smaller and smaller newborns. Overall mortality and morbidity rates for uncontrolled hypertension in infants are unknown. With appropriate treatment, the prognosis for resolution of hypertension is good. In most cases, hypertension is short-lived and blood pressures return to normal even when medication is discontinued. Recent experience with improved antihypertensive agents in infancy has meant that nephrectomy for renovascular hypertension is rarely required. There is still much to learn about the indications for treatment of elevated blood pressures in infancy and the potential adverse effects of therapy. Infants with a history of neonatal hypertension should be followed closely because the long-term prognosis is not known and recurrence of hypertension remains a possibility. Because hypertension can develop in high-risk newborns following discharge from the nursery, these infants deserve routine blood pressure measurements as part of their outpatient follow-up.

Atrioventricular conduction in children of women with systemic lupus erythematosus.

The neonatal lupus syndrome consists of transient cutaneous lupus lesions or permanent congenital complete heart block (or hepatic fibrosis), or both, in infants born to mothers with systemic lupus erythematosus (SLE). The frequency of conduction abnormalities was examined in 86 offspring of 53 women affected by SLE. Electrocardiograms from the offspring demonstrated normal sinus rhythm in 84 of 86 offspring. The PR interval was normal for age (< 95th percentile) in 82 offspring and normal for heart rate in 81. Three children had a PR interval > 95th percentile (i.e., first-degree heart block) for both age and heart rate. The PR interval of the other 6 subjects with first-degree heart block for age or heart rate (> or = 95th percentile) was < or = 0.18 second. In contrast, using a rank assignment of PR intervals in relation to heart rate and age derived from published standards, grouped data indicated that heart rate adjusted for age was greater and PR interval adjusted for heart rate longer in offspring of mothers who had the onset of SLE before or during pregnancy than in the normal population; this observation did not hold for offspring whose mothers developed SLE after the pregnancy. These findings indicate that offspring of mothers with SLE, even in the absence of an abnormal electrocardiogram, may have experienced a maternal internal environment that produces subclinical changes in atrioventricular conduction. However, newborns with a normal pulse rate are unlikely to have significant abnormalities in atrioventricular conduction and do not need screening electrocardiograms at birth.

Multivariate genetic analysis of blood pressure and body size. The Medical College of Virginia Twin Study.

BACKGROUND: In subjects of all ages, those who weigh the most often have the highest blood pressure. Thus, in epidemiological studies, weight is the most important correlate of blood pressure. Using the data from the Medical College of Virginia Twin Study, we asked these questions: 1) Do the same genetic paths that regulate body size also regulate systolic and diastolic blood pressure? 2) Are there distinct genetic pathways that regulate each of these variables? 3) Does environment play a major regulatory role? 4) Are the correlations among these variables mainly due to genetic or environmental effects? 5) Do genetic paths that regulate body size mediate the correlation between systolic blood pressure and diastolic blood pressure? METHODS AND RESULTS: We ascertained 253 Caucasian twin pairs living in the Commonwealth of Virginia. The average age was 11.2 +/- 0.2 years. We used multivariate path analyses to investigate the genetic relations among systolic blood pressure, diastolic blood pressure, and body size. We found that there was a highly significant genetic relation between systolic blood pressure and body size and between systolic and diastolic blood pressure. There are genetic paths that are shared within these two sets of variables, but in each case, the paths for each pair appear to be separate from one another. CONCLUSIONS: These analyses provide a method to partition correlation coefficients found in epidemiological studies into genetic and environmental components. The correlations found among these three variables are in large part due to these genetic relations. We found no genetic relation between diastolic blood pressure and body size.

Sex differences in the determinants of left ventricular mass in childhood. The Medical College of Virginia Twin Study.

BACKGROUND: Left ventricular (LV) hypertrophy is a predictor of cardiovascular events in adults and has been observed in children and adolescents with hypertension. We wanted to establish the determinants of LV mass in normotensive preadolescent children. Our objectives were 1) to produce a simplified and generalizable model of the clinical variables that determine normal cardiac growth during childhood and 2) to understand better why males have an increased LV mass relative to females, even as children. METHODS AND RESULTS: In a group of 243 eleven-year-old children, we analyzed anthropometric, hemodynamic, and echocardiographic data to define which variables were predictors of echocardiographically determined LV mass. Stepwise regression was used to predict LV mass overall, by sex, and by body size (body mass index). Overall, LV mass was directly related to weight, male sex, and systolic and diastolic blood pressure and inversely related to resting heart rate and skin-fold thicknesses. Systolic blood pressure was a determinant in boys but not in girls. Heart rate was a weak inverse correlate in both sexes. When the data were analyzed by body mass index quartile, weight was the sole predictor of LV mass in the largest children. CONCLUSIONS: We conclude that in normotensive preadolescent children, 1) weight, but not pondersity, is a strong predictor of LV mass; 2) body fat is negatively associated with LV mass; 3) boys have an increased LV mass relative to girls; and 4) boys and girls have similar anthropometric determinants and may have different hemodynamic determinants. Our data suggest that body size, and in particular lean body mass, explains much of the variability in cardiac growth seen in children. The influence of hemodynamic variables seems to be more limited. Our findings are of general interest because, although hypertensive heart disease is well described, the early developmental stages are not well understood.

Blood pressure response to exercise. A marker for future hypertension?

Whether or not an exaggerated blood pressure response to exercise in childhood predicts adult-onset essential hypertension is not known. While peak systolic blood pressure during exercise can indicate future hypertension, left ventricular mass (measured echocardiographically) and resting systolic blood pressure seem to be much better predictors. However, the blood pressure response to exercise in groups of normotensive individuals, such as those with a family history of hypertension, may identify physiologic changes associated with the early hypertensive state.