Short QT Interval Prevalence and Clinical Outcomes in a Pediatric Population.

BACKGROUND: Risk associated with short QT interval has recently received recognition. European studies suggest a prevalence of 0.02% to 0.1% in the adult population, but similar studies in pediatric patients are limited. We sought to determine the prevalence of short QT interval in a pediatric population and associated clinical characteristics and outcomes. METHODS AND RESULTS: Retrospective review of an ECG database at a single pediatric institution. The database was queried for ECGs on patients ≤21 years with electronically measured QTc of 140 to 340 ms. Patients with QTc of 140 to 340 ms confirmed by a pediatric electrophysiologist were identified for chart review for associated clinical characteristics, symptoms, and outcome. Patients with and without symptoms were compared in an attempt to identify variables associated with outcome. The query included 272 504 ECGs on 99 380 unique patients. Forty-five patients (35 men, 76%) had QTc ≤340 ms, for a prevalence of 0.05%. Median age was 15 years (interquartile range, 2-17), median QT 330 ms (interquartile range, 280-360), and median QTc 323 ms (IQR, 313-332). Women had significantly shorter QTc compared with men (312 versus 323 ms; P=0.03). Two deaths were noted in chart review--one from respiratory failure and the second of unknown pathogenesis in a patient with dilated cardiomyopathy. CONCLUSIONS: Short QT interval was a rare finding in this pediatric population, with a prevalence of 0.05%. Male predominance was identified, although the median QT interval was significantly shorter in women. There seem to be no unifying clinical characteristics for this pediatric patient cohort with short QT interval.

Consequence of use of lower dose flat plate fluoroscopy in pediatric patients undergoing ablation for supraventricular tachycardia.

Traditional imaging for ablation of supraventricular tachycardia has been fluoroscopy, although 3-dimensional electroanatomic mapping (3D) has been demonstrated to reduce radiation exposure. This study compares a technique for the reduction of radiation, low-dose fluoroscopy (LD), with standard-dose fluoroscopy (SD) and 3D with SD (3D-SD). This was a single institutional retrospective cohort study. All patients undergoing initial ablation for atrioventricular reentrant tachycardia (AVRT) or atrioventricular nodal reentrant tachycardia (AVNRT) from 2009 to 2012 were reviewed and divided into 3 groups: (1) SD, (2) 3D (CARTO or NavX) with SD, or (3) LD. LD uses the same equipment as SD but includes customized changes to the manufacturer's lowest settings by decreasing the requested dose to the detector. Primary outcomes were fluoroscopy time and dose area product exposure. One hundred eighty-one patients were included. The median age was 15.0 years (3.3-20.8); 59% had AVRT, 35% had AVNRT, and 6% had both AVRT and AVNRT. LD decreased the dose area product (DAP) compared with SD (637.0 vs 960.1 cGy*cm², p = 0.01) with no difference in fluoroscopy time. 3D-SD decreased fluoroscopy time compared with SD (9.9 vs 18.3 minutes, p <0.001) with DAP of 570.1.0 versus 960.1 cGy*cm² (p = 0.16). LD and 3D-SD had comparable DAP (637.0 vs 570.1 cGy*cm², p = 0.67), even though LD had significantly longer fluoroscopy time (19.9 vs 9.9 minutes, p <0.001). In conclusion, LD during catheter ablation of AVRT and AVNRT significantly reduced the DAP compared with SD and had similar radiation exposure compared with 3D with SD.

The age-related discrepancy in the effect of neuropeptide Y on select catecholamine biosynthetic enzymes in the adrenal medulla and hypothalamus in rats.

The elevated levels of circulating catecholamines (CAs) with age may be related to the increased expression of CA biosynthetic enzymes, tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DbetaH) in the adrenal medulla of senescent compared with younger animals. Neuropeptide Y (NPY) is co-synthesized and co-released with CAs in the adrenal medulla. NPY inhibits the stimulated secretion of CAs, however, its role in regulation of the genes encoding CA biosynthetic enzymes is not clear. We hypothesized that NPY up-regulates TH, DbetaH and NPY expression in the adrenal medullae of young and old Fischer-344 rats. NPY increased mRNA expression of TH, DbetaH, NPY and also enhanced TH protein level in the adrenal medullae of young rats by 50%, 35%, 45% and by 20%, respectively. We also examined the effect of NPY on TH and NPY mRNA in the hypothalamus. Basal expression of TH mRNA was decreased in the hypothalamus with age. DNA binding activities of activator protein-1 and cAMP response element binding protein were also augmented only in the young by 140% and 125%, respectively. We conclude that NPY stimulates the CA biosynthetic pathway in the adrenal medulla and positive auto-regulation of NPY might be involved in this process. The stimulatory effect of NPY on adrenomedullary CA biosynthetic pathway is blunted with age.