Bruce S. Alpert

Clinical Stress Testing in the Pediatric Age Group A Statement From the American Heart Association Council on Cardiovascular Disease in the Young, Committee on Atherosclerosis, Hypertension, and Obesity in Youth

This statement is an updated report of the American Heart Associations previous publications on exercise in children. In this statement, exercise laboratory requirements for environment, equipment, staffing, and procedures are presented. Indications and contraindications to stress testing are discussed, as are types of testing protocols and the use of pharmacological stress protocols. Current stress laboratory practices are reviewed on the basis of a survey of pediatric cardiology training programs.

Race and gender influence ambulatory blood pressure patterns of adolescents.

&NA; The purpose of this study was to examine ambulatory blood pressure and heart rate patterns in healthy, normotensive adolescents and to determine the influence of race and gender on these patterns. Ambulatory blood pressure recordings were performed on 199 adolescents; 42 were black males, 55 were white males, 65 were black females, and 37 were white females. The mean age (±SD) was 13±2 years. Blood pressure readings were obtained with an automatic, noninvasive recorder. Black adolescents and white adolescents had similar blood pressures while awake (116/69 vs. 116/69 mm Hg), with boys having higher levels of systolic blood pressure (118 vs. 114 mm Hg) and comparable levels of diastolic blood pressure (69 vs. 69 mm Hg) relative to girls. The patterns while the adolescents were asleep, however, were different. White boys (106 mm Hg), white girls (105 mm Hg), and black girls (105 mm Hg) had similar systolic blood pressures during sleep. Black boys (112 mm Hg), however, had significantly higher systolic blood pressures while asleep. Black adolescents, as a group, had significantly higher diastolic blood pressures than white adolescents while asleep (64 vs. 61 mm Hg). Changes in blood pressure from awake to asleep were not related to changes in heart rate. Results of this study indicate that both race and gender are important determinants of the diurnal pattern of blood pressure and heart rate in adolescents. (Hypertension 1989;14:598‐603)

Race and cardiovascular reactivity. A neglected relationship.

The magnitude of the cardiovascular response to stress has been implicated in the pathogenesis of cardiovascular disease. Psychological stress procedures have received increased usage as an alternative to expensive physical (exercise) stress procedures. In the present investigation, 213 healthy, black or white, male or female children between the ages of 6 and 18 years were exposed to the psychological stress of a video game. The video game challenge was administered by a black or a white experimenter and was played under three levels of increasing stress, 1) personal challenge, 2) experimenters challenge, and 3) experimenters challenge accompanied by a financial incentive, while blood pressure and heart rate were monitored. Results indicated that the video games provoked significant and incremental cardiovascular reactivity across the games. Black children demonstrated significantly greater reactivity than white children; the racial difference was more reliably observed for systolic and diastolic blood pressure than for heart rate. Furthermore, the race of the experimenter exerted a significant effect and often interacted with the race of the child, such that greater reactivity occurred in same-race pairings than in mixed-race pairings. These results suggest that reactivity is affected by an individuals race and social milieu and that reactivity may be one mechanism responsible for the greater prevalence of hypertension among blacks.

Contribution of Superior Vena Caval Flow to Total Cardiac Output in Children A Doppler Echocardiographic Study

BACKGROUND After a cavopulmonary anastomosis, the superior vena caval flow, by virtue of being the effective pulmonary blood flow, is the most important factor influencing the systemic arterial saturation. Determination of the amount of this blood flow will allow a better understanding of the physiology of the circulation after this anastomosis. The purposes of this study were to determine the volumetric flow in the superior vena cava and to evaluate its contribution to the cardiac output as children grow. METHODS AND RESULTS Using two-dimensional and Doppler echocardiography, we measured the diameter of and mean flow velocities in the superior venae cavae and the pulmonary arteries of 145 healthy children. We calculated the volumetric flow in each vessel and determined the ratio of superior vena caval flow to total cardiac output. Cardiac output and superior vena caval flow increased with increasing age and body surface area. The superior vena caval flow accounted for 49% of cardiac output in newborn infants. This contribution increased to a maximum of 55% at the age of 2.5 years. Afterward, there was a slow decline in the ratio of superior vena caval-pulmonary arterial flow; it reached the adult value of 35% by 6.6 years of age. CONCLUSIONS There is a maturational change in the superior vena caval contribution to total cardiac output in children. This is most likely related to somatic growth and changes in body segment proportions. This flow maturation may explain the higher systemic saturation in infants compared with older children after cavopulmonary anastomosis.

Hypertension in young patients after renal transplantation: ambulatory blood pressure monitoring versus casual blood pressure.

The results of ambulatory blood pressure monitoring (ABPM) in children after kidney transplant were analyzed to ascertain any alteration in circadian BP profile, degree of hypertension, and efficacy of therapy. The data were also compared with casual BP data and left ventricular mass index (LVMI). We have examined 30 patients (17 male, 13 female), mean age 16.1+/-3.6 years after kidney transplant. All patients were receiving triple immune-suppressive therapy and 20 of them were also taking antihypertensive therapy. They underwent clinical examination with measurement of BP at rest, echocardiogram mono-2D, and ABPM. The following ABPM parameters were recorded: systolic (S) and diastolic (D) BP at rest; mean 24-h SBP and DBP; mean daytime SBP and DBP; mean nighttime SBP and DBP; nocturnal fall in SBP and DBP; and mean daytime and nighttime heart rate (HR). The patients were divided in two groups. Group A consisted of 20 patients taking antihypertensive treatment; group B consisted of 10 patients not taking antihypertensive treatment. Casual and ABPM data for the two groups were compared using the Student t test for unpaired data. Blood pressure at rest and LVMI were not statistically different between the two patient groups. The ABPM data showed statistical differences between the two groups for mean 24-h SBP and DBP, daytime and nighttime SBP, nighttime DBP, fall in nocturnal DBP, and nighttime HR. Mean 24-h SBP and DBP, mean daytime SBP and DBP, and mean nighttime SBP and DBP were significantly correlated to LVMI (respectively, P = .009, P = .005, P = .008, P = .007, P = .05, and P = .01). Twenty-four-hour ABPM was more useful in the diagnosis and management of hypertension than was casual BP at rest.

Ambulatory blood pressure and increased left ventricular mass in children at risk for hypertension.

OBJECTIVE To relate ambulatory blood pressure (ABP) to cardiac target organ measurement in children at risk for primary hypertension (HTN). STUDY DESIGN Left ventricular mass index (LVMI) and ABP were measured concomitantly in children (6 to 18 years) at risk for hypertension using a cross-sectional study design. RESULTS LVMI showed a significant positive correlation with 24-hour systolic blood pressure (SBP) load, SBP index (SBPI), and standard deviation score (SDS). When subjects were stratified by LVMI percentile, there were significant differences in SBP load, 24-hour SBPI, and 24-hour SSDS. The odds ratio (OR) of having elevated LVMI increased by 54% for each incremental increase of SDS in 24-hour SSDS after controlling for race and BMI (OR = 1.54, unit = 1 SDS, CI = 1.1, 2.15, P = .011) and increased by 88% for each increase of 0.1 in BPI (OR = 1.88, CI = 1.03, 3.45, P = .04). Subjects with stage 3 HTN had significantly greater mean LVMI compared with normal subjects (P = .002 by ANOVA; LMVI, 31.6 +/- 7.9 versus 39.5 +/- 10.4). CONCLUSIONS As systolic ABP variables increase, there is greater likelihood for increased LVMI. Staging based on ABPM allows assessment of cardiovascular risk in children with primary hypertension.

Blood pressure response to dynamic exercise in healthy children--black vs white.

In order to determine normal values for systolic blood pressure response to cycle ergometer stress testing in children, we performed 405 studies in subjects from 6 to 15 years of age, of whom 184 were black and 221 were white. We analyzed the data in relation to sex, color, age, and body surface area. Resting systolic blood pressure showed no differences between groups of black and white children, analyzed either by age or surface area. Peak exercise blood pressures were higher in the black females, in comparison to their white counterparts, only when separated into groups by body surface area. The black males had higher exercise blood pressure values than the whites, both by age and surface area evaluation. Our data suggest a difference in the blood pressure response to dynamic exercise within the black population. Further studies are needed to define the mechanism of this difference and whether this difference may provide a clue to the identification of children at increased risk for developing hypertension later in life.

Aortic dimensions in tall men and women

Abstract Subjects with the Marfan syndrome are at risk for sudden death from aortic regurgitation, dissection or rupture. The severity of aortic regurgitation correlates with the degree of aortic root dilation, not annular dilation.1,2 The risk of aortic dissection increases with aortic enlargement.1,2 Aortic dissection may occur with only moderate aortic root dilation.1 Because Marfan patients with nonenlarged aortic roots are thought to be at low risk for aortic dissection and rupture,1 it is critical to define an enlarged aortic root. Nomograms that have been published for normal aortic root dimensions have not included a sufficient number of healthy subjects whose height exceeds the 95th percentile,3–7 usually present in Marfan patients. Thus, we do not know the normal aortic root dimensions for subjects whose body size is equivalent to those with the Marfan syndrome. This study examines the acceptable upper limit of normal for the aortic root in healthy subjects taller than the 95th percentile. The data were sought for use in determining which Marfan patients have aortic roots of greater than normal size, thus warranting pharmacologic intervention and activity restriction.

Responses to ergometer exercise in a healthy biracial population of children.

To determine normal values for the exercise variables heart rate, blood pressure, maximal workload, physical working capacity index, J point displacement, and ST segment slope, we stress tested 405 healthy children. We analyzed the data for four body surface area-determined groups, to discover whether there were any racial differences between healthy white children and black children. There were numerous racial differences in blood pressure, maximal workload, and physical working capacity index; there were no differences in the heart rate values. The incidence of false-positive J point displacement was less than or equal to 3% when the PR isoelectric line method was used. The ST segment slope in healthy children was always greater than zero at maximal exercise. Thus, norms for exercise variables must be expressed in relation to both sex and race. The nomograms presented in this report provide an easy-to-use set of normative data for cycle ergometer stress testing in children.

Cardiac size and function in children with sickle cell anemia

Cardiac size and function were studied echocardiographically in 124 children with sickle cell anemia. A group of 78 healthy black children served as control subjects. Sickle cell patients exhibited progressive chamber enlargement and progressively increasing left ventricular mass. Although contractility indices were normal, when the opposing influences of volume overload due to anemia and ventricular dysfunction were separated, abnormalities of systolic time intervals were identified. Left ventricular systolic time interval ratio and left ventricular preejection period were higher in the sickle cell group and became increasingly abnormal with growth, suggesting that left ventricular function deteriorated with time.