Tachyarrhythmia discriminator for implantable cardioverter-defibrillators in bundle branch block.

BACKGROUND: Inaccurate arrhythmia classification by implantable cardioverter-defibrillators (ICDs) contributes to inappropriate shocks and increased health care utilization. OBJECTIVE: The purpose of this study was to evaluate the ability of a novel discriminator using far-field (FF) and near-field (NF) right ventricular lead electrograms (EGMs) to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) in patients with underlying conducted narrow QRS, right bundle branch block (RBBB), and left bundle branch block (LBBB). METHODS: ICD interrogations were reviewed, identifying subjects with tachycardia events at least 5 beats in duration with stable morphology and cycle length. FF to NF (FF-NF) EGM intervals during tachycardia and baseline conducted rhythm were measured using digital calipers. Events with uncertain tachycardia rhythm mechanism were excluded. RESULTS: Ninety-five subjects were included. Mean FF-NF interval during tachycardia was significantly lower during SVT than VT (25.8 ± 12.0 ms vs 91.0 ± 37.2 ms; P <.001). Participants with LBBB (n = 22) and RBBB (n = 21) had significantly lower mean FF-NF intervals during SVT compared with VT (LBBB 25.6 ± 7.26 ms vs 93.1 ± 41.5 ms; P <.001; RBBB 30.0 ± 16.6 ms vs 101.7 ± 34.3 ms; P <.001). In this cohort, FF-NF interval cutoff of 100 ms was 100% specific for VT discrimination regardless of underlying QRS morphology, with sensitivity of 46%, 50%, and 38% for LBBB, RBBB, and narrow QRS, respectively. CONCLUSION: Prolonged FF-NF interval on intracardiac EGM during tachycardia is a highly specific discriminator for VT, regardless of baseline QRS morphology.

What can parents do to reduce youth obesity? An initial study with a diverse sample.

The body mass index (BMI) of diverse, low-income fifth grade students (n = 36) was regressed on physical activity (Child Adolescent Activity Log), percentage dietary fat (Food Habits Questionnaire), and the Food/Activity Parenting Practices Questionnaire. The model explained 50% of the variance in student BMI, adjusted R(2) = .50, F (4, 19) = 6.84, p = .001. Students accurately perceived their weight status. Students' perception of parenting strategies, along with dietary fat, was significantly associated with their BMI. Parent's (n = 14) BMI, not the child's, was associated with the strategies they used. Three parents tested an online authoritative parenting program. Further research is needed.