Comparison of formulas for calculation of the corrected QT interval in infants and young children.

OBJECTIVE: To compare 4 heart rate correction formulas for calculation of the rate corrected QT (QTc) interval among infants and young children. STUDY DESIGN: R-R and QT intervals were measured from digital electrocardiograms. QTc were calculated with the Bazett, Fridericia, Hodges, and Framingham formulas. QTc vs R-R graphs were plotted, and slopes of the regression lines compared. Slopes of QTc-R-R regression lines close to zero indicate consistent QT corrections over the range of heart rates. RESULTS: We reviewed electrocardiograms from 702 children, with 233 (33%) <1 year of age and 567 (81%) <2 years. The average heart rate was 122 ± 20 bpm (median 121 bpm). The slopes of the QTc-R-R regression lines for the 4 correction formulas were -0.019 (Bazett); 0.1028 (Fridericia); -0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett formula, a QTc >460 ms was 2 SDs above the mean, compared with "prolonged" QTc values of 414, 443, and 353 ms for the Fridericia, Hodges, and Framingham formulas, respectively. CONCLUSIONS: The Bazett formula calculated the most consistent QTc; 460 ms is the best threshold for prolonged QTc. The study supports continued use of the Bazett formula for infants and children and differs from the use of the Fridericia correction during clinical trials of new medications.

Genetic variants for long QT syndrome among infants and children from a statewide newborn hearing screening program cohort.

OBJECTIVES: Autosomal recessive long QT syndrome (LQTS), or Jervell and Lange-Nielsen syndrome (JLNS), can be associated with sensorineural hearing loss. We aimed to explore newborn hearing screening combined with electrocardiograms (ECGs) for early JLNS detection. STUDY DESIGN: In California, we conducted statewide, prospective ECG screening of children ≤ 6 years of age with unilateral or bilateral, severe or profound, sensorineural or mixed hearing loss. Families were identified through newborn hearing screening and interviewed about medical and family histories. Twelve-lead ECGs were obtained. Those with positive histories or heart rate corrected QT (QTc) intervals ≥ 450 ms had repeat ECGs. DNA sequencing of 12 LQTS genes was performed for repeat QTc intervals ≥ 450 ms. RESULTS: We screened 707 subjects by ECGs (number screened/number of responses = 91%; number of responses/number of families who were mailed invitations = 54%). Of these, 73 had repeat ECGs, and 19 underwent gene testing. No subject had homozygous or compound heterozygous LQTS mutations, as in JLNS. However, 3 individuals (with QTc intervals of 472, 457, and 456 ms, respectively) were heterozygous for variants that cause truncation or missplicing: 2 in KCNQ1 (c.1343dupC or p.Glu449Argfs*14; c.1590+1G>A or p.Glu530sp) and 1 in SCN5A (c.5872C>T or p.Arg1958*). CONCLUSIONS: In contrast to reports of JLNS in up to 4% of children with sensorineural hearing loss, we found no examples of JLNS. Because the 3 variants identified were unrelated to hearing, they likely represent the prevalence of potential LQTS mutations in the general population. Further studies are needed to define consequences of such mutations and assess the overall prevalence.

Benefits of care coordination for children with complex disease: a pilot medical home project in a resident teaching clinic.

OBJECTIVE: To study the integration of comprehensive care coordination for children with complex disease in our resident education clinic at University of California Los Angeles by analyzing alterations in medical resource use. STUDY DESIGN: The Pediatric Medical Home Project at University of California Los Angeles was designed to include 4 basic elements: 1) 60-minute intake appointment; 2) follow-up appointments twice the length of a standard visit; 3) access to a "family liaison"; and 4) a family notebook ("All about Me" binder). From the initial cohort of 43 patients, encounter data on 30 were analyzed to determine use of outpatient, urgent, emergency department (ED), and inpatient services. Encounters for each patient were compared for a period of 1 year before and 1 year after enrollment. RESULTS: The average number of ED visits per patient decreased from 1.1 +/- 1.7 before enrollment to 0.5 +/- 0.9 after medical home enrollment (P = .02). However, no significant change was found in use of any of the other health care resources studied. CONCLUSIONS: Incorporating a program of care coordination according to the principles of the medical home into an outpatient pediatric residency teaching clinic may not only serve as a training vehicle for pediatric residents, but also create favorable alterations in medical resource use.

Sudden infant death syndrome: changing epidemiologic patterns in California 1989-2004.

OBJECTIVE: To evaluate the changes of sudden infant death syndrome (SIDS) epidemiology in California. STUDY DESIGN: We used 1989 to 2004 California statewide death registry data. SIDS cases were selected by "age of decedent" <1 year and "cause of death" listed as SIDS. RESULTS: We identified 6303 cases (61% males) of SIDS. SIDS incidence rate decreased by 77%, from 1.38 per 1000 births in 1989 to 0.31 per 1000 births in 2004. No further decrease in SIDS incidence was noted from 2002 to 2004. The incidence rate was highest among blacks (2.02 per 1000 births) and lowest in Asian/Pacific Islanders (0.46 per 1000 births). The overall median age at death was 82 days, with no significant change over time. However, the peak age at death shifted from 2 months of age in 1989 to 2001 to 3 months of age in 2002 to 2004. Seasonal variation in the incidence of SIDS was attenuated. The difference in incidence rates between weekdays and weekends increased over the study period. CONCLUSIONS: The incidence rate of SIDS declined in California from 1989 to 2001, with no further decline after 2002. Several epidemiologic changes were noted: The peak age of SIDS death shifted from 2 months to 3 months of age; seasonal variation diminished; and weekday to weekend difference became more pronounced.

Decreasing number of deaths of infants with hypoplastic left heart syndrome.

OBJECTIVE: To assess mortality rates and demographic characteristics for infants with hypoplastic left heart syndrome (HLHS) in California. STUDY DESIGN: We used California death registry files from 1990 to 2004 to compare overall mortality and demographic characteristics between infants with HLHS (n = 856) who received surgical intervention and those who received comfort care. The California discharge database was used to calculate the annual incidence of disease and survival rates for infants with HLHS undergoing surgery between 1995 and 1999. RESULTS: The annual number of deaths for infant with HLHS decreased by nearly 50% over the study period, even though the incidence of the disease remained constant during this period. For all deaths, the proportion of infants receiving comfort care decreased significantly over time compared with those infants who underwent surgery. Although the total number of deaths in infants with HLHS who underwent surgical intervention increased, the mortality rate for this cohort decreased. Interstage unexpected mortality and the median age at death both increased in the infants who underwent surgery. CONCLUSIONS: Over the study period of 1990 to 2004 in California, fewer families chose comfort care for infants diagnosed with HLHS, and the number of deaths for those infants who underwent surgical intervention increased. These changes likely reflect improved treatment outcomes and an increased number of families desiring surgical intervention in higher-risk infants.

Right ventricular abnormalities in sickle cell anemia: evidence of a progressive increase in pulmonary vascular resistance.

OBJECTIVE: To assess the effects of sickle cell anemia (SCA) on the right ventricle (RV). STUDY DESIGN: Echocardiograms of 32 children with SCA were compared with age-matched healthy controls. RV measurements included diastolic area index, fractional area change, free-wall mass index, ejection time corrected for heart rate (ET(c)), and tricuspid regurgitation (TR) gradient. RESULTS: SCA subjects had elevated RV ETc (mean +/- standard deviation, 0.369 +/- 0.030 sec vs 0.351 +/- 0.022 sec; P < .01), diastolic area index (19.9 +/- 2.4 cm(2)/m(2) vs 13.2 +/- 2.1 cm(2)/m(2); P < .01) and free-wall mass index (33.2 +/- 4.4 g/m(2) vs 23.9 +/- 4.3 g/m(2); P < .01), whereas RV fractional area change (37 +/- 8% vs 36 +/- 4%) was not different from controls. Although RV diastolic area index in SCA paralleled the normal range over time, RV free-wall mass index continued to gradually rise throughout childhood (r = .42; P < .05). TR gradients > 2.5 m/sec, consistent with pulmonary hypertension, were found in 5 (16%) of SCA subjects, all older than 9 years. CONCLUSIONS: RV preload and systolic function do not worsen during childhood in SCA; however, RV mass index and the prevalence of pulmonary hypertension increase consistent with rising pulmonary vascular resistance.