[Clinical observation on six children of left bundle branch area pacing].

Objective: To explore the safety and effectiveness of left bundle branch area pacing (LBBAP) in children. Methods: Clinical data, pacing electrocardiogram and parameters of 6 patients (5 females and 1 male) who underwent permanent pacemaker implantation and LBBAP from January to June 2019 in the Department of Pediatric Cardiology of Anzhen Hospital were retrospectively analyzed. Results: The weight of the 6 patients aged between 9 and 14 years ranged from 26 to 48 kg. Five patients were diagnosed with third degree atrioventricular block, and 1 patient was diagnosed with cardiac dysfunction after right ventricular apical pacing. Cardiac function decreased in one patient and remained normal in the other five patients. Left ventricular end diastolic diameter (LVEDD) Z score was 1.85±0.65. V(1) lead showed changes like right bundle branch block in pacing electrocardiogram. No significant difference was found regarding QRS wave duration ((95±13) ms vs. (111±20) ms, t=-1.610, P>0.05) between preoperation and postoperation. Pacing threshold was (0.85±0.26) V. The sensing threshold was (15.0±4.3) mV and the impedance was (717±72) Ω. P potential was recorded in 3 cases. The earliest left ventricular local activation time was (56±5) ms and remained stable at different output voltages. Postoperative echocardiography revealed that the electrodes were located near the endocardium of the left ventricular septum. No complications such as myocardial perforation and electrode dislocation occurred during follow-up. The pacing threshold, sensing threshold and impedance were (0.60±0.09)V, (16.1±3.9)mV, (662±78)Ω respectively at 3 months after operation. The patient with low left ventricular ejection fraction (LVEF) recovered to normal on the 3 rd day after LBBAP (45% vs. 57%). The LVEDD Z score decreased to (1.1±0.3) at 3 months after operation and was significantly lower than that before operation (t=2.38, P<0.05). Conclusions: LBBAP in children can achieve narrow QRS pacing andphysiological pacing with stablepacing parameters. It can improve left ventricular enlargement caused by long-term bradycardia, and cardiac dysfunction and cardiac enlargement caused by long-term right ventricular apical pacing quickly and effectively.LBBAP is safe and feasible for older children in the near future. However, the long term potential risks of LBBAP need further observation and study.

[An analysis of clinical characteristics and acute treatment of supraventricular tachycardia in children from a multicenter study].

Objective: The study assessed the clinical characteristics and response to acute intravenous antiarrhythmic drug therapy of supraventricular tachycardia (SVT) in children. Methods: This was a multicenter prospective descriptive study including 257 children from First Hospital of Tsinghua University, Peking University First Hospital, Children's Hospital Affiliated to Capital Institute of Pediatrics and Beijing Anzhen Hospital who received intravenous antiarrhythmic drug therapy for SVT from July 2014 to February 2017. The clinical and tachycardia features, response to intravenous antiarrhythmic drug therapy of these children were characterized. Statistical analyses were performed using t test, Mann-Whitney U test, χ(2) test and H test. Results: The onset of SVT occurred at any age with a distribution with positive skewness, 57.6% (n=148) children<1 year, 17.5% (n=45) children1~<3 years, 10.5% (n=27) children 3~<6 years and 14.4% (n=37) children ≥ 6 years of age. The percentages of SVT types were 49.4% (n=127) for atrioventricular reentry tachycardia (AVRT), 4.3% (n=11) for atrioventricular nodal reentry tachycardia (AVNRT), 26.8% (n=69) for unclassified paroxysmal SVT and 19.5% (n=50) for atrial tachycardia (AT), respectively. Tachycardia-induced cardionyopathy (TIC) secondary to SVT developed in 30 of 225 (13.3%). Left ventricular ejection fraction (LVEF) of the 27 children attacked by TIC returned to normal after successful control of SVT (41.1%±6.3% vs. 60.3%±9.2%, t=-10.397, P=0.000). Complete termination of SVT by antiarrhythmic drugs was achieved in 164 of 257 (63.8%), partial termination rate was 18.7% (48 of 257) and failure to terminate rate was 17.5% (45 of 257). Propafenone (complete cardioversion in 98 (73.1%) of 134) and amiodarone (complete cardioversion in 23 (76.7%) of 30) showed better efficacy for SVT termination than adenosine (complete cardioversion in 26 (44.1%) 59) (χ(2)=20.524, P=0.000). Paroxysmal SVT had a higher termination rate on pharmacological therapy than AT (67.1% vs. 50.0%, χ(2)=6.337, P=0.042). Patients of different age groups had significantly different response to antiarrhythmic therapy (χ(2)=13.904, P=0.031). Children<1 year of age showed the least response to antiarrhythmic drug therapy with complete termination in 51 (55.4%) of 92. Adverse effects occurred in 9 patients (3.5%): Four patients had severe hypotensive shock using propafenone (n=3) and adenosine (n=1), and 3 patients had sinus arrest using adenosine. Conclusion: Most (57.6%) children with SVT have their first clinical episode within 1 year of age, and AVRT is the most common type. TIC occurs in 13.3% of children with SVT. Intravenous antiarrhythmic drug therapy has a 63.8% complete termination rate for children with SVT and incidence of adverse effects is 3.5%. Propafenone and amiodarone are more effective for SVT termination in children than adenosine. Serious adverse effects may occur when using propafenone.

[Multicenter investigation of the correlation between supraventricular tachycardia and tachycardia-induced cardiomyopathy in children].

Objective: This study aimed to investigate the correlation between supraventricular tachycardia (SVT) and tachycardia-induced cardiomyopathy(TIC) in children and assess the risk factors for the development of TIC. Method: One hundred and eighty-three patients were recruited in four hospitals of Beijing diagnosed as SVT were divided into two groups depending on whether or not complicated with TIC. The age, gender, tachycardia type, ventricular rate during tachycardia, frequency of tachycardia episodes and duration of tachycardia were compared between the two groups and risk factors associated with TIC were analyzed. Statistical analyses were performed using t test, Mann-Whitney U and χ(2) test. Result: Totally 183 patients were included in this study (paroxysmal supraventricular tachycardia, PSVT, n=149; atrial tachycardia, AT, n=34). The incidence of TIC was 13.1%. There was significant difference regarding the incidence of TIC between children with AT and children with PSVT (26.5% vs. 10.1%, χ(2)=6.537, P=0.011). The percentage of AT in patients with TIC was significantly higher than patients without TIC (37.5% vs. 15.7%, χ(2)=6.537, P=0.011). Patients with TIC had a higher frequency of tachycardia episodes(2.5(1.0-4.8) beats/year vs 4.0(1.0-10.0) beats/year, Z=-2.223, P=0.026)and longer duration of tachycardia(11.0(1.1-36.0) h vs 2.5(1.0-12.0) h, Z=-2.154, P=0.031)compared with patients without TIC. Multivariate predictors of TIC was longer duration of tachycardia (OR=2.041, P=0.028). Conclusion: TIC occurs in 13.1% of children with SVT. The incidence of TIC in children with AT is higher than in children with PSVT. Risk factor for the development of TIC is longer duration of tachycardia.

Structure of C-phycocyanin from Spirulina platensis at 2.2 A resolution: a novel monoclinic crystal form for phycobiliproteins in phycobilisomes.

The crystal structure of C-phycocyanin from the cyanobacterium S. platensis has been determined at 2.2 A resolution. The crystals belong to the monoclinic crystal form, which has not been previously reported for phycobiliprotein structures. The structure was solved using the molecular-replacement method with a final R value of 18.9% (R(free) = 23.7%) after model building and refinement. In the crystals used for the study, the C-phycocyanin hexamers formed by face-to-face association of two trimers are arranged in layers rather than in columns. Three different kinds of packing between adjacent hexamers in the layer were compared. The tight packing of two adjacent hexamers formed by four trimers in the asymmetric unit brings beta155 PCB chromophores close together, so it is possible that lateral energy transfer takes place through the beta155-beta155 route.

[Research progress in physiological functions of selenoenzyme and other selenocompounds].

Selenium (Se) is an essential trace element for animals. Selenocysteine (Sec), the 21st aminoacid, is a component of selenoproteins and has been founded in the active center of selenoenzymes. The functions of Se within the body have been primarily shown in the forms of selenoproteins, especially selenoenzymes. Incorporation of selenocysteine occurs on the basis of genetic expression and Se is the only trace element under direct genetic control. Recently, findings have shown that Se and selenocompounds conducted many other potential functions such as protection against inflammatory factors, inhibition of protein kinase C (PKC), stimulation of MAP kinase (mitogen activated protein kinase/myelin basic protein kinase) and S6 kinase (ribosomal S6 protein kinase), regulation of the immune system and interaction with other elements and vitamins etc, suggesting that the roles of Se in human health may be more diverse than previously suspected.

Extension of focal depth by using an encoded source.

An idea for extending the focal depth by using an encoded source is presented, and the principle is explained by investigating the clarity of the defocus image. By using partial coherence theory, we show that not only the resolving power can be improved but also the focal depth. We correct the conventional conclusion that focal depth is dependent only on the numerical aperture.

Image superresolution by using a source-encoding technique.

A source-encoding technique is utilized to achieve image superresolution. The method overcomes several drawbacks of previous methods and shows a new approach for further study of practical applications of the superresolution technology.

Radioprotective effect of extract from Spirulina platensis in mouse bone marrow cells studied by using the micronucleus test.

The radioprotective effect of an extract of Spirulina platensis has been studied using the micronucleus test in polychromatic erythrocytes of bone marrow of mice. In this system the extract caused a significant reduction of the micronucleus frequencies induced by gamma-radiation.