Proarrhythmic effect of automatic threshold testing algorithm in dual chamber devices.

BACKGROUND: Operation of auto-threshold testing (ATT) algorithm in current dual chamber cardiac devices require temporary shortening of atrio-ventricular (AV) delay to accurately measure evoked potential (capture) after a pacing pulse. Near simultaneous AV pacing causes atrial pressure elevation and may be associated with atrial arrhythmias. OBJECTIVE: We evaluated the prevalence of atrial arrhythmias induced by ATT in Abbott devices. METHODS: Device clinic records were reviewed at a single center for patients with dual chamber Abbott pacemaker/ICD. ATT-induced atrial fibrillation (AF) cases were defined as new appropriate mode switch episodes while the ATT was operating. The auto-capture test trends were defined as unstable if there were deviations >1 V in capture threshold trend events that did not correlate with routine in-office testing. RESULTS: One hundred and seventy patients were programmed in dual chamber pacing mode. The ventricular ATT was active in 118 patients and of these 78 had true mode switch episodes. Six patients developed AF during ventricular ATT. Three patients had most recorded atrial arrhythmias in close association with ATT (63%, 66%, 100% vs 2%,9%, 33% in other patients with known prior AF). An unstable auto-capture trend curve was seen in 33 patients (6 showing ATT-induced AF) versus 85 patients with stable auto-capture curve and no ATT-induced AF (P = .0001, the χ2 test). CONCLUSION: Ventricular auto-capture algorithm use is associated with induction of AF in dual chamber Abbott devices with a prevalence of over 5%. AF occur more frequently (18%) in patients with erratic ventricular ATT trend results.

Comparison of three oral contrast preparations for magnetic resonance enterography in pediatric patients with known or suspected Crohn disease: a prospective randomized trial.

BACKGROUND: Oral contrast preparation is fundamental to ensuring diagnostic examination quality for magnetic resonance enterography (MRE), yet little is known about the relative palatability and tolerability of various oral contrast agents in pediatric patients with known or suspected inflammatory bowel disease. OBJECTIVE: We prospectively compared three MRE oral preparations in pediatric patients with known or suspected Crohn disease with respect to patient-reported tolerability and radiologist-determined small-bowel distension and opacification. MATERIALS AND METHODS: Seventy-five pediatric patients (mean age 14.8 years, 55% female) with known or suspected Crohn disease referred for MRE were randomized to an oral preparation with a sugar alcohol-based flavored beverage (Breeza), polyethylene glycol preparation (MiraLAX), or low-concentration barium sulfate suspension (VoLumen). Patients were instructed to consume oral contrast agent (using a weight-based protocol) beginning 60 min prior to MRE imaging. Following MRE, patients completed a questionnaire regarding their oral preparation solution including: taste (1-5 scale), feeling of well-being (1-5 scale) and willingness to consume again (yes/no). Two radiologists reviewed all MRE exams and rated exams for global features (active disease, overall small-bowel distention [1-4 scale]) and features specific to individual small-bowel segments (extent of distention, maximal luminal diameter, opacification, and susceptibility artifact). Statistical methods included one-way analysis of variance (ANOVA) with Tukey honest difference and Fisher exact tests. RESULTS: The overall rate of completion of the entire prescribed contrast volume was 53% (40/75), with a significantly higher rate of completion for MiraLAX than for VoLumen (70% vs. 30%, P=0.007). Crossover to a different preparation occurred in nine patients (12%) and was significantly more frequent when the initial preparation was VoLumen versus MiraLAX (29% vs. 0%, P=0.005). Mean subjective taste ratings for both MiraLAX (3.4, P<0.0001) and Breeza (2.8, P=0.006) were superior to those of VoLumen (1.9), which persisted in the subset of patients with MRE evidence of active Crohn disease. Patients who consumed MiraLAX were more likely to be willing to drink it again compared to those consuming VoLumen (82% vs. 46%, P=0.009). Overall small-bowel distention and bowel-segment-specific metrics (distention, maximal diameter, opacification and susceptibility) did not significantly differ among groups. CONCLUSION: In pediatric patients with known or suspected Crohn disease, MiraLAX and Breeza were rated as more palatable than VoLumen, and all three preparations achieved a similar degree of small-bowel distension and opacification on MRE. Imaging centers performing MRE should stock multiple oral contrast preparations because a sizable proportion of children require more than one agent to ingest the requisite oral contrast volume.