Distal end of the atrioventricular nodal artery predicts the risk of atrioventricular block during slow pathway catheter ablation of atrioventricular nodal re-entrant tachycardia

OBJECTIVE—To search for a reliable anatomical landmark within Koch's triangle to predict the risk of atrioventricular (AV) block during radiofrequency slow pathway catheter ablation of AV nodal re-entrant tachycardia (AVNRT).
PATIENTS AND METHODS—To test the hypothesis that the distal end of the AV nodal artery represents the anatomical location of the AV node, and thus could be a useful landmark for predicting the risk of AV block, 128 consecutive patients with AVNRT receiving slow pathway catheter ablation were prospectively studied in two phases. In phase I (77 patients), angiographic demonstration of the AV nodal artery and its ending was performed at the end of the ablation procedure, whereas in the subsequent phase II study (51 patients), the angiography was performed immediately before catheter ablation to assess the value of identifying this new landmark in reducing the risk of AV block. Multiple electrophysiologic and anatomical parameters were analysed. The former included the atrial activation sequence between the His bundle recording site (HBE) and the coronary sinus orifice or the catheter ablation site, either during AVNRT or during sinus rhythm. The latter included the spatial distances between the distal end of the AV nodal artery and the HBE and the final catheter ablation site, and the distance between the HBE and the tricuspid border at the coronary sinus orifice floor.
RESULTS—In phase I, nine of the 77 patients had complications of transient (seven patients) or permanent (two patients) complete AV block during stepwise, anatomy guided slow pathway catheter ablation. These nine patients had a wider distance between the HBE and the distal end of the AV nodal artery, and a closer approximation of the catheter ablation site to the distal end of the AV nodal artery, which independently predicted the risk of AV block. In contrast, none of the available electrophysiologic parameters were shown to be reliable. When the distance between the distal end of the AV nodal artery and the ablation target site was more than 2 mm, the complication of AV block virtually never occurred. In phase II, all 51 patients had successful elimination of the slow pathways without complication when the ablation procedure was guided by preceding angiography with identification of the distal end of the AV nodal artery.
CONCLUSIONS—The distal end of the AV nodal artery shown by angiography serves as a useful landmark for the prediction of the risk of AV block during slow pathway catheter ablation of AVNRT.


Keywords: atrioventricular nodal artery; atrioventricular nodal re-entrant tachycardia; catheter ablation; heart block.     

Calcium current restitution in mammalian ventricular myocytes is modulated by intracellular calcium

Restitution of the conventional L-type calcium current (ICa) was studied in dog or guinea pig ventricular myocytes to understand its time course and regulation. Whole-cell ICa free of other overlapping currents was recorded with a suction pipette. The intracellular environment was varied by intracellular dialysis. The properties of ICa were similar in dog and guinea pig ventricular myocytes, except that the amplitude of ICa was larger in the latter (2.2 +/- 0.5 nA in guinea pig cells and 0.9 +/- 0.2 nA in dog cells, n = 8 for both). In both types of cells during restitution a holding voltage (Vh) negative to -50 mV induced a transient increase in ICa above the control level (ICa overshoot). This overshoot was inhibited by substituting barium for calcium, lowering [Ca]0, increasing intracellular calcium buffering capacity, ryanodine (1-2 microM), or caffeine (10 mM). The overshoot peaked 30-100 msec after repolarization from the conditioning depolarization and gradually declined over the following 2-3 seconds. During the overshoot, although the amplitude of ICa was larger its half-time of decay was longer than the control. The maximum overshoot occurred following a conditioning step to plateau voltages and it was decreased by prolonging the conditioning step from 50 to 100 or 500 msec. It is concluded that intracellular calcium regulates restitution of the L-type calcium channels in mammalian ventricular myocytes and that the sarcoplasmic reticulum is involved in this process.     

Effects of resynchronization therapy on cardiac function in pacemaker patients "upgraded" to biventricular devices

INTRODUCTION: Cardiac resynchronization therapy (CRT) improves echocardiographic measures of cardiac function and has a variable effect on QRS duration in patients with left bundle branch block (LBBB). How CRT affects these indices in patients with right ventricular (RV) pacing-induced LBBB who are "upgraded" with left ventricular (LV) leads for CRT is unknown. We studied the echocardiographic effects of RV pacing and CRT in patients with prior continuous RV pacing after LV lead placement. METHODS AND RESULTS: Fifteen consecutive patients (age 73 +/- 11 years, LV ejection fraction 24 +/- 6%, QRS duration 190 +/- 27 msec) with New York Heart Association class IIIB-IV symptoms and continuous RV pacing underwent LV lead placement for CRT. Echocardiography and ECG were performed sequentially during RV pacing and CRT. CRT was associated with significantly reduced QRS duration (190 +/- 27 msec vs 165 +/- 18 msec, P = 0.005) and reduced LV electromechanical delay (180 +/- 33 msec vs 161+/- 43 msec). Baseline QRS duration correlated with CRT response. After CRT, patients had significant improvements in indices of systolic function, including LV ejection fraction, myocardial performance index (MPI), and LV ejection time. Abnormal baseline MPI was associated with greater improvement after CRT. LV end-diastolic and systolic volumes were similarly decreased with CRT. Mitral valve deceleration time, an index of diastolic function, was not affected by CRT. CONCLUSION: "Upgrading" RV paced patients with advanced heart failure to CRT improves measures of electrical and LV mechanical synchrony and improves systolic function.     

Non-invasive evaluation of therapeutic response in keloid scar using diffuse reflectance spectroscopy

The pathogenesis and ideal treatment of keloid are still largely unknown, and it is essential to develop an objective assessment of keloid severity to evaluate the therapeutic response. We previously reported that our diffuse reflectance spectroscopy (DRS) system could assist clinicians in understanding the functional and structural condition of keloid scars. The purpose of this study was to understand clinical applicability of our DRS system on evaluating the scar severity and therapeutic response of keloid. We analyzed 228 spectral data from 71 subjects with keloid scars. The scars were classified into mild (0-3), moderate (4-7) and severe (8-11) according to the Vancouver scar scale. We found that as the severity of the scar increased, collagen concentration and water content increased, and the reduced scattering coefficient at 800 nm and oxygen saturation (SaO₂) decreased. Using the DRS system, we found that collagen bundles aligned in a specific direction in keloid scars, but not in normal scars. Water content and SaO₂ may be utilized as reliable parameters for evaluating the therapeutic response of keloid. In conclusion, the results obtained here suggest that the DRS has potential as an objective technique with which to evaluate keloid scar severity. In addition, it may be useful as a tool with which to track longitudinal response of scars in response to various therapeutic interventions.OCIS codes: (170.5280) Photon migration, (170.4580) Optical diagnostics for medicine, (170.6510) Spectroscopy, tissue diagnostics, (290.1990) Diffusion     

Types of collagen synthesized by normal rat liver hepatocytes in primary culture

Collagen formation is an important function of liver parenchymal cells that may be relevant to the pathogenesis of hepatic fibrosis. The types of collagen synthesized by cultured normal rat liver hepatocytes were examined. Cells isolated from adult rats by enzymatic dispersion of the liver were established in primary monolayer culture. Cells were then incubated with radiolabeled proline for 20 hr in the presence of ascorbate and the lathrogen beta-aminopropionitrile. Collagen secreted into the cell media was assessed separately from that in the cell layer. The greater proportion of newly synthesized collagen was associated with the cell layer. Collagen types were identified by ion exchange chromatography and by polyacrylamide gel electrophoresis. Types I, III, IV, and V collagen were present in both media and cell layer. Types III and V were the predominant types found. Very little Type I collagen was synthesized by these cultured normal hepatocytes. The percentages of Types I, III, IV, and V collagens, combining media and cell layer, were 6, 38, 19, and 36, respectively.     

Targeting oncogenic interleukin‐7 receptor signalling with N‐acetylcysteine in T cell acute lymphoblastic leukaemia

Activating mutations of the interleukin‐7 receptor (IL7R) occur in approximately 10% of patients with T cell acute lymphoblastic leukaemia (T‐ALL). Most mutations generate a cysteine at the transmembrane domain leading to receptor homodimerization through disulfide bond formation and ligand‐independent activation of STAT5. We hypothesized that the reducing agent N‐acetylcysteine (NAC), a well‐tolerated drug used widely in clinical practice to treat acetaminophen overdose, would reduce disulfide bond formation, and inhibit mutant IL7R‐mediated oncogenic signalling. We found that treatment with NAC disrupted IL7R homodimerization in IL7R‐mutant DND‐41 cells as assessed by non‐reducing Western blot, as well as in a luciferase complementation assay. NAC led to STAT5 dephosphorylation and cell apoptosis at clinically achievable concentrations in DND‐41 cells, and Ba/F3 cells transformed by an IL7R‐mutant construct containing a cysteine insertion. The apoptotic effects of NAC could be rescued in part by a constitutively active allele of STAT5. Despite using doses lower than those tolerated in humans, NAC treatment significantly inhibited the progression of human DND‐41 cells engrafted in immunodeficient mice. Thus, targeting leukaemogenic IL7R homodimerization with NAC offers a potentially effective and feasible therapeutic strategy that warrants testing in patients with T‐ALL.     

Antihyperlipidemic activity of Allium chinense bulbs

Allium chinense is a medicinal plant and nutritional food commonly used in Eastern Asia. In this study, we investigated the in vitro antioxidant activity (scavenging of α,α-diphenyl-β-picrylhydrazyl free radical, total phenol content, reducing power, and total antioxidant activity) and constituents of various extracts from A. chinense. Moreover, we also studied the in vivo hypolipidemic effects of extracts on high-fat-diet Wistar rats. Ethanol extracts from A. chinense showed notable antioxidant activity, and its high-dose essential-oil extract both significantly reduced serum and hepatic total cholesterol, triglyceride, and low-density lipoprotein levels and increased serum high-density lipoprotein levels in high-fat-diet Wistar rats compared with those observed following treatment with the control drug probucol. Additionally, visceral fat in high-fat-diet Wistar rats was reduced. Furthermore, groups with high doses of essential-oil and residue extracts showed protective effects associated with histopathological liver alteration. These results suggested that A. chinense is a valuable plant worthy of further investigation as a potential dietary supplement or botanical drug.