Abnormal Central Pulsatile Hemodynamics in Adolescents With Obesity: Higher Aortic Forward Pressure Wave Amplitude Is Independently Associated With Greater Left Ventricular Mass

We hypothesized that increased aortic forward pressure wave amplitude (Pf), which is determined by characteristic impedance (Zc) in the proximal aorta, is the primary hemodynamic determinant of obesity-associated higher left ventricular (LV) mass in adolescents. Aortic pulsatile hemodynamics were measured noninvasively in 60 healthy adolescents (age 14-19 years; 42% male; 50% black) by sequential recordings of pulse waveforms via tonometry, brachial blood pressure, and pulsed Doppler and diameter of the LV outflow tract using 2-dimensional echocardiography. Adolescents who were overweight/obese (n=23; age 16.0±0.3 years; body mass index ≥85th percentile) had higher LV mass index, brachial and carotid systolic blood pressure and pulse pressure, normalized Zc and Pf compared with adolescents with healthy weight (n=37; 16.7±0.3 years; body mass index <85th percentile, all P<0.01). In contrast, there was no difference in mean or diastolic blood pressure, carotid-femoral pulse wave velocity, carotid augmentation index, or aortic backward wave amplitude (all P>0.05). Stepwise multiple linear regression analysis that included age, sex, race, normalized Zc, and brachial systolic blood pressure revealed that body mass index (B±SE; 0.49±0.20, P=0.02, R2=0.26), aortic Pf (0.22±0.07; P<0.02, R2 change=0.11), and cardiac output (2.82±1.02, P<0.01; R2 change=0.08) were significant correlates of LV mass index (total R2=0.44, P<0.01). These findings suggest that higher aortic Pf is a major hemodynamic determinant of increased LV mass in adolescents with elevated adiposity. Improper matching between aortic diameter and pulsatile flow during early systole potentially contributes to the early development of LV hypertrophy in childhood obesity.

Exercise stress echocardiography after childhood Ross surgery: functional outcome in 26 patients from a single institution

Adult studies suggest a better functional outcome after aortic valve replacement with a pulmonary autograft compared with mechanical or homograft valves. Little is known about functional results after Ross surgery in growing children. This study reports formal exercise stress echocardiographic data from 26 pediatric Ross patients. A retrospective cohort study analyzed stress echocardiographic data of patients who underwent Ross surgery as a child (<17 years old). All patients were operated by a single surgeon and underwent a Bruce protocol stress echocardiogram on the treadmill. Twenty-six patients (4 girls) were 9.3 ± 5.0 years at surgery and 14.9 ± 3.5 years (range 6.6-19.7 years) at follow-up. Mean follow-up was 5.4 ± 3.7 years (median 4.2). All were asymptomatic. The exercise time was normal in 87% of cases at 12.8 ± 2.5 min. On stress echocardiography, the mean right-ventricular outflow tract (RVOT) gradient increased from 38 ± 22 mmHg at rest to 82 ± 33 mmHg after exercise, but this did not correlate with exercise times. Stress echocardiography is useful in evaluating patients after childhood Ross surgery for aortic valve disease. In this pediatric cohort, most patients achieved normal exercise capacity. The presence of mild or moderate RVOT obstruction had no significant impact on exercise capacity.

Primary hypertension at a single center: treatment, time to control, and extended follow-up

We present data on presentation, treatment, and follow-up of 65 pediatric patients with primary hypertension treated over the past 12 years, including initial anthropometric data, pharmacologic treatment, time to control for both systolic and diastolic blood pressure (SBP/DBP), and maintenance of control over time. Data was normalized to standard deviation scores (SDS) for mathematical analysis, and antihypertensive medication dosages were converted to dosage equivalents for a single member of each antihypertensive class. We used multiple regression analysis and Kaplan- Meier survival curves to determine the time to control, medication, and dose effectiveness. Patients were seen for an average of seven visits over 25 months. Initial BPs averaged 134/71 mmHg (2.1/0.6 SDS). Patients were taller, heavier, and had higher body mass index than average for age and sex. By the fourth visit, SBP was <90th percentile in 79%. Ninety percent could be controlled, although 32 lost control at some point (at least 16 due to noncompliance). At the last visit, 46 were controlled, and 5/8 patients off medication remained normotensive. Only angiotensin-converting enzyme inhibitors and beta-blockers demonstrated significant association with BP control. This is the first study to document the time to control of BP, and it can serve as an initial standard for quality assessment.

Genetic heterogeneity of Bartter's syndrome revealed by mutations in the K+ channel, ROMK

Mutations in the Na-K-2Cl cotransporter (NKCC2), a mediator of renal salt reabsorption, cause Bartter's syndrome, featuring salt wasting, hypokalaemic alkalosis, hypercalciuria and low blood pressure. NKCC2 mutations can be excluded in some Bartter's kindreds, prompting examination of regulators of cotransporter activity. One regulator is believed to be ROMK, an ATP-sensitive K+ channel that 'recycles' reabsorbed K+ back to the tubule lumen. Examination of the ROMK gene reveals mutations that co-segregate with the disease and disrupt ROMK function in four Bartter's kindreds. Our findings establish the genetic heterogeneity of Bartter's syndrome, and demonstrate the physiologic role of ROMK in vivo.

Bartter's syndrome, hypokalaemic alkalosis with hypercalciuria, is caused by mutations in the Na-K-2Cl cotransporter NKCC2

Inherited hypokalaemic alkalosis with low blood pressure can be divided into two groups-Gitelman's syndrome, featuring hypocalciuria, hypomagnesaemia and milder clinical manifestations, and Bartter's syndrome, featuring hypercalciuria and early presentation with severe volume depletion. Mutations in the renal Na-Cl cotransporter have been shown to cause Gitelman's syndrome. We demonstrate linkage of Bartter's syndrome to the renal Na-K-2Cl cotransporter gene NKCC2, and identify frameshift or non-conservative missense mutations for this gene that co-segregate with the disease. These findings demonstrate the molecular basis of Bartter's syndrome, provide the basis for molecular classification of patients with inherited hypokalaemic alkalosis, and suggest potential phenotypes in heterozygous carriers of NKCC2 mutations.