Atriofascicular Pathways: Where to Ablate?

BACKGROUND: Atriofascicular accessory pathway (AP), often referred to as Mahaim pathway, is an uncommon form of preexcitation. The usual target for ablation is at the site of a high-frequency potential along the tricuspid annulus (TA). We present our observations in mapping and ablation of 29 patients with atriofascicular APs. METHODS AND RESULTS: Twenty-nine consecutive patients who underwent radiofrequency ablation (RFA) for atriofascicular pathways comprised the series. Demographic factors, clinical features of the tachycardia, ablation site, and results were analyzed. The mean age was 19 +/- 8 years; 15 were men. Three patients had Ebstein's anomaly of the tricuspid valve. Four patients had an additional AP and two patients had concomitant typical atrioventricular nodal reentrant tachycardia. RFA was successful in 28 patients (97%); repeat ablation was required in two patients. The site of successful ablation was on the TA at the site of a sharp, high frequency potential in 15 patients (52%). In the remaining 14 patients, a potential was not found along the TA, and ablation was targeted at the ventricular insertion of the AP into the distal right bundle. At the successful ventricular ablation site, local ventricular activation preceded the surface electrocardiogram by 20 +/- 6 ms. Eight of the 14 patients (57%) undergoing ablation in the ventricle, developed right bundle branch block (RBBB). One patient who underwent successful ablation along the TA also manifested RBBB after ablation; however, this patient had Ebstein's anomaly and preexcitation had completely masked the RBBB. The mean procedure and fluoroscopy time was 150 +/- 32 and 35 +/- 12 minutes, respectively. CONCLUSIONS: In atriofascicular pathways, an AP potential was found along the TA in only 52% of patients. Ablation at the ventricular insertion site often resulted in RBBB (57%), but the AP was also successfully ablated.     

TNF-alpha and IL-1beta increase pericyte/endothelial cell co-culture permeability

BACKGROUND: Pericytes (PC) have a unique synergistic relationship with microvascular endothelial cells (MVEC) in the regulation of capillary permeability. This study investigates the effect of TNF-alpha, IL-1beta, and IL-6 on the microvasculature by measuring changes in PC contractility, and also, albumin permeability across MVEC/PC co-cultures. MATERIALS AND METHODS: Semi-permeable inserts were plated first with rat lung MVEC and then PCs (on the fourth day) at a ratio of 10:1 MVEC/PC. On day 5, 50 ng/ml of TNF-alpha, IL-1beta, and IL-6 were added with or without a secretory phospholipase A(2)-IIA (sPLA(2)-IIA) inhibitor for 24 h. After treatments, albumin clearances were quantified. For measuring contractility, PCs were cultured on collagen matrices and exposed for 24 h to TNF-alpha, IL-1beta, and IL-6 at 1 ng/ml, 10 ng/ml, and 50 ng/ml with/without inhibitors for sPLA(2)-IIA, phospholipase A(2) (PLA(2)), and cyclooxygenase-II (COX-II). After treatments, the surface area of the collagen disks was digitally quantified. RESULTS: TNF-alpha and IL-1beta significantly increased albumin clearance in MVEC/PC co-cultures (P < 0.05) and induced dose-dependent relaxation of PCs (P < 0.05). PC relaxation was completely attenuated with the sPLA(2)-IIA and pLA(2) inhibitors; the COX-II inhibitor provided partial blockade. IL-6 had no effect on PC contractility or permeability. CONCLUSION: TNF-alpha and IL-1beta directly increased microvascular permeability in co-cultures. They also induced relaxation of PCs through a sPLA(2)-IIA dependent mechanism. Interestingly, IL-6 had no effect, although its presence in high levels has been demonstrated in inflamed lungs. These findings may help elucidate the significance of PC in regulating the capillary response to various pro-inflammatory cytokines.     

Transcatheter fenestration of a total cavopulmonary connection baffle

Transcatheter creation of a de novo fenestration of a total cavopulmonary connection baffle has not been previously reported from India. We present our experience with such a procedure in a 4-year-old child with recurrent pleural effusions in the early postoperative period.