Difficulties with invasive risk stratification performed under anesthesia in pediatric Wolff-Parkinson-White Syndrome.

BACKGROUND: Children with Wolff-Parkinson-White Syndrome (WPW) are at risk for sudden death. The gold standard for risk stratification in this population is the shortest pre-excited RR interval during atrial fibrillation (SPERRI). OBJECTIVE: The purpose of this study was to determine how closely measurements made in the electrophysiology laboratory in patients with WPW compared to SPERRI obtained during an episode of clinical pre-excited atrial fibrillation (Clinical-SPERRI). METHODS: This was a subgroup analysis of a multicenter study of children with WPW. Subjects in our study (N = 49) were included if they had Clinical-SPERRI measured in addition to 1 or more of 3 surrogate measurements: SPERRI obtained during electrophysiological study (EP-SPERRI), accessory pathway effective refractory period (APERP), or shortest pre-excited paced cycle length with 1:1 conduction (SPPCL). RESULTS: Seventy percent of electrophysiological measurements were made with patients under general anesthesia. Clinical-SPERRI moderately correlated with EP-SPERRI (r = 0.495; P = .012). However, 24% of our patients with Clinical-SPERRI ≤250 ms would have been misclassified as having a low-risk pathway based on EP-SPERRI >250 ms. Clinical-SPERRI did not correlate with APERP or SPPCL (r < 0.3; P >.1). Mean EP-SPERRI, APERP, and SPPCL all were greater than Clinical-SPERRI. CONCLUSION: Electrophysiology laboratory measurements of pathway characteristics made with patients under general anesthesia do not correlate well with Clinical-SPERRI. Of APERP, SPPCL, and EP-SPERRI, only EP-SPERRI had moderate correlation with Clinical-SPERRI. This study questions the predictive ability of invasive risk stratification with patients under general anesthesia, given that 24% of patients with high-risk Clinical-SPERRI (≤250 ms) had EP-SPERRI that may be considered low risk (>250 ms).

Mammillothalamic Disconnection Alters Hippocampocortical Oscillatory Activity and Microstructure: Implications for Diencephalic Amnesia.

Diencephalic amnesia can be as debilitating as the more commonly known temporal lobe amnesia, yet the precise contribution of diencephalic structures to memory processes remains elusive. Across four cohorts of male rats, we used discrete lesions of the mammillothalamic tract to model aspects of diencephalic amnesia and assessed the impact of these lesions on multiple measures of activity and plasticity within the hippocampus and retrosplenial cortex. Lesions of the mammillothalamic tract had widespread indirect effects on hippocampocortical oscillatory activity within both theta and gamma bands. Both within-region oscillatory activity and cross-regional synchrony were altered. The network changes were state-dependent, displaying different profiles during locomotion and paradoxical sleep. Consistent with the associations between oscillatory activity and plasticity, complementary analyses using several convergent approaches revealed microstructural changes, which appeared to reflect a suppression of learning-induced plasticity in lesioned animals. Together, these combined findings suggest a mechanism by which damage to the medial diencephalon can impact upon learning and memory processes, highlighting an important role for the mammillary bodies in the coordination of hippocampocortical activity.SIGNIFICANCE STATEMENT Information flow within the Papez circuit is critical to memory. Damage to ascending mammillothalamic projections has consistently been linked to amnesia in humans and spatial memory deficits in animal models. Here we report on the changes in hippocampocortical oscillatory dynamics that result from chronic lesions of the mammillothalamic tract and demonstrate, for the first time, that the mammillary bodies, independently of the supramammillary region, contribute to frequency modulation of hippocampocortical theta oscillations. Consistent with the associations between oscillatory activity and plasticity, the lesions also result in a suppression of learning-induced plasticity. Together, these data support new functional models whereby mammillary bodies are important for coordinating hippocampocortical activity rather than simply being a relay of hippocampal information as previously assumed.

"Transseptal" technique through atrial baffles for 3-dimensional mapping and ablation of atrial tachycardia in patients with d-transposition of the great arteries.

Access to targets for radiofrequency ablation in patients with congenital heart disease may be limited by anatomy and by surgically placed obstacles. In patients with atrial switch anatomy for d-transposition of the great arteries, the critical isthmus for maintenance of intraatrial macroreentry circuits is found often on the pulmonary venous side of the atrial baffle. A retrograde approach is extremely difficult for these arrhythmias. Use of transseptal techniques for diagnostic catheterization in these patients has been reported. We report the use of a transseptal technique in two cases in conjunction with 3-dimensional electroanatomic mapping for the successful ablation of atrial reentry tachycardias in patients with Mustard and Senning anatomy.

Techniques to avoid atrioventricular block during radiofrequency catheter ablation of septal tachycardia substrates in young patients.

UNLABELLED: Radiofrequency catheter ablation (RFCA) has proven safe for most young patients, but the risk of inadvertent atrioventricular (AV) block remains. The purpose of this report is to describe techniques to avoid inadvertent AV block during effective RFCA in young patients with septal tachycardia substrates. METHODS: The techniques included intubation and apnea during RFCA, coronary sinus pacing during RFCA to observe intact AV conduction during junctional ectopy, localizing the optimal His electrogram prior to RFCA, not ablating during tachycardia and titrating power output with temperature monitoring. RESULTS: In the period January 1995-June 2001, RFCA of 424 tachycardia substrates was performed. A total of 217 consecutive septal tachycardia substrates are included in this report. Apnea eliminated a mean catheter tip displacement of 5.4 +/- 2.5 mm seen during respiration. No patient experienced transient or permanent complete AV block after any of the 217 substrate ablation procedures. All of the patients had normal PR intervals following ablation without development of any degree of AV block in 194 patients at latest follow-up. RFCA success for substrates with septal accessory pathways was 87/96 (91%), permanent junctional reciprocating tachycardia (PJRT) 15/16 (94%), typical atrioventricular node reentry tachycardia (AVNRT) 82/85 (96%), atypical AVNRT 6/7 (86%) and intra-atrial reentry tachycardia (IART) 10/13 (77%). Fluoroscopy time averaged 10.8 minutes. For patients with accessory pathway, 8 (7.9%) developed a recurrence. CONCLUSION: Catheter stability is paramount to safe and effective RFCA in septal locations. Use of these techniques resulted in acceptable success rates and low recurrence rate for RFCA of septal tachycardia substrates while avoiding inadvertent AV block in these young patients.