Distribution of light chains and ATPase activity of myosin in the atrioventricular conducting tissue of bovine heart

Summary The relations of the light chains of myosins of the atria, ventricles, and atrioventricular conducting tissue (specialized myocardial tissue) and the distribution of the light chains of myosin in different regions of the atrioventricular conducting tissue in bovine heart were examined. Two-dimensional gel electrophoresis showed that the atrial and ventricular myosins each had two light chains (LC₁ and LC₂). Ventricular LC₁ differed from atrial LC₁, but ventricular LC₂ corresponded to atrial LC₂. The specialized myocardial tissue myosin had three light chains (named here SL₁, SL₂, and SL₃). SL₁ comigrated with ventricular LC₁, SL₂ with atrial LC₁, and SL₃ with ventricular LC₂ and atrial LC₂. The compositions of the three light chains of myosins in various regions of the atrioventricular conducting tissue were determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The percentage proportion of SL₁ decreased in the order—atrioventricular node (AVN), right and left bundle branches (RLBB), His bundle (HIS), false tendon (FT) myosin; while the percentage proportion of SL₂ decreased in the order—FT and HIS, RLBB, AVN myosin. The percentages of SL₃ in these four regions were similar. The Ca²⁺-activated ATPase activity of myosin was highest in the AVN and lowest in the FT. The activities in the HIS and RLBB were intermediate between those in the AVN and FT. Thus, the composition of the light chains and the Ca²⁺-activated ATPase activity were different in various regions of the atrioventricular conducting tissue.     

Reversible cardiogenic shock caused by atrioventricular junctional rhythm after percutaneous coronary intervention

An 82-year-old female patient undergoing cardiogenic shock caused by atrioventricular junctional rhythm immediately after percutaneous coronary intervention (PCI) is described. Pharmacotherapy was invalid, and subsequent application of atrial pacing reversed the cardiogenic shock. PCI-related injury of sinuatrial nodal artery leading to acute atrial contractility loss, accompanied by atrioventricular junctional arrhythmia, was diagnosed. We recommend that preoperative risk evaluation be required for multi-risk patients. Likewise, emergent measures should to be established in advance. This case reminds us that atrial pacing can be an optimal management technique once cardiogenic shock has occurred.     

Gender Differences in the Electrophysiological Characteristics of Atrioventricular Conduction System and their Clinical Implications

Objective - The underlying mechanisms of the differences in sex distribution of patients with atrioventricular (AV) nodal re-entrant tachycardia and Wolff-Parkinson-White syndrome are poorly understood. The objective of this study was to determine potential gender differences in the electrophysiological properties of the normal AV conduction system that may be attributable to differences in sex distribution. Design - The AV conduction properties were studied in 96 patients (52 men and 44 women) who underwent electrophysiological testing, 32 patients with atrial tachycardia, 39 with idiopathic ventricular tachycardia and 25 with unexplained palpitations or syncope. Results - The AH (83 &#45 15 ms) and His-ventricular intervals in men (42 &#45 6 ms) were significantly longer than in women (78 &#45 14, 38 &#45 6 ms, p < 0.05, respectively), as was the PR interval (160 &#45 17 vs 152 &#45 13 ms, p = 0.02). The effective refractory period of AV node in men (349 &#45 75 ms) was longer than in women (297 &#45 45 ms, p = 0.03). However, no significant difference was observed between men and women with respect to the incidence of AV nodal dual pathway and the maximum AH interval achieved during premature stimulation or incremental pacing. The AV block cycle length was significantly longer in men (371 &#45 76 ms) than in women (330 &#45 52 ms, p = 0.02). A longer ventriculoatrial block cycle length was also found in men than in women although not at a significant level (436 &#45 107 vs 384 &#45 90 ms, p = 0.08). In addition, men (23%) were twice as likely to have ventriculoatrial dissociation during ventricular pacing as women were (11%, p = 0.2). Conclusion - The data show that gender-related differences in AV conduction properties may be responsible for the differences in sex distribution observed in patients with AV nodal re-entrant tachycardia and those with ventricular pre-excitation.     

In Vitro Generation of Atrioventricular Heart Valve Neoscaffolds

Tissue engineering of cardiovascular structures represents a novel approach to improve clinical strategies in heart valve disease treatment. The aim of this study was to engineer decellularized atrioventricular heart valve neoscaffolds with an intact ultrastructure and to reseed them with umbilical cord‐derived endothelial cells under physiological conditions in a bioreactor environment. Mitral (n = 38) and tricuspid (n = 36) valves were harvested from 40 hearts of German Landrace swine from a selected abattoir. Decellularization of atrioventricular heart valves was achieved by a detergent‐based cell extraction protocol. Evaluation of the decellularization method was conducted with light microscopy and quantitative analysis of collagen and elastin content. The presence of residual DNA within the decellularized atrioventricular heart valves was determined with spectrophotometric quantification. The described decellularization regime produced full removal of native cells while maintaining the mechanical stability and the quantitative composition of the atrioventricular heart valve neoscaffolds. The surface of the xenogeneic matrix could be successfully reseeded with in vitro‐expanded human umbilical cord‐derived endothelial cells under physiological flow conditions. After complete decellularization with the detergent‐based protocol described here, physiological reseeding of the xenogeneic neoscaffolds resulted in the formation of a confluent layer of human umbilical cord‐derived endothelial cells. These results warrant further research toward the generation of atrioventricular heart valve neoscaffolds on the basis of decellularized xenogeneic tissue.     

儿童暴发性心肌炎临床分析

目的：探讨儿童暴发性心肌炎的临床特征。方法对北京儿童医院2007年1月至2013年5月收治的50例暴发性心肌炎患儿的病历资料进行回顾性分析,对其性别、年龄、临床表现及治疗、预后等进行总结。结果50例暴发性心肌炎患儿中,存在消化道症状16例（32．0％）,心血管系统症状14例（28．0％）,神经系统症状8例（16．0％）,26．0％（13例）的患儿以阿斯综合征为首发表现,46例（92．0％）存在心电图异常表现,心肌酶指标及心脏彩色多普勒超声阳性率分别为48．0％（24例）和50．0％（25例）;32例给予丙种球蛋白输注,44例应用甲泼尼龙,28例Ⅲ度房室传导阻滞患儿在综合治疗基础上安装临时起搏器,4例患儿最终安装永久起搏器;对发生室性心动过速的20例患儿,6例应用利多卡因,7例应用胺碘酮进行转复,8例给予同步电复律,17例心动过速终止,1例安装临时起搏器后转复窦性心律,2例合并心室颤动的患儿经抢救无效死亡。结论儿童暴发性心肌炎的症状多样,多数不典型,误诊、漏诊率高;联合心电图、心脏彩色多普勒超声及心肌酶学指标诊断暴发性心肌炎的阳性率高,并对疾病的严重程度、预后有一定的提示作用。     

Acute changes in blood pressure as a cause of cardiac arrhythmias

The effect of an acute change in blood pressure (BP) on ventricularectopic activity and the influence of antiarrhythmic agentson this effect were examined in 24 patients. In 11 patientswith premature ventricular complexes (PVCs), the BP was temporarilyreduced by a sodium nitroprusside drip. In all of them the incidenceof PVCs was reduced (or annihilated) by the induced hypotension.In 13 patients without ventricular ectopic activity, a metaraminoldrip was given until either a PVC appeared or the systolic BPreached 200 mmHg, or symptoms appeared. In 12 cases at leastone PVC appeared and in 8 of them the total number of PVCs was13 or more, usually in the form of bigeminy. The repetitionof the test following quinidine administration (serum quinidinelevel 1.7 ±0.5 ng ml^–1) in 6 cases did not changethis pattern, with one exception. It prevented the appearanceof idioventricular accelerated rhythm in one case in whom thisrhythm had been induced by the hypertension provocative testbefore the quinidine administration. All cases, in whom thetest failed to induce more than 3 PVCs, had no cardiac problemat all. Six of the 8 cases in whom the test induced 13 or morePVCs had organic cardiac disease or palpitation. Other arrhythmiasobserved on BP elevation, were supraventricular extra beats,nodal escape rhythms and atrioventricular block. In one casewith cardiomyopathy, the BP elevation was associated with earlysigns of heart failure that subsided quickly. In conclusion, acute elevation on BP may be associated withthe generation of PVCs and its reduction with their reductionor disappearance.     

Protein synthesis in the atrioventricular node during acute experimental cardiac hypertrophy in the rat

The relative concentration of autoradiographic grains was measured over the atrioventricular node of the adult rat heart 2 h after the intravenous injection of [³H]-leucine and 20 h after the induction of left ventricular cardiac hypertrophy by constriction of the abdominal aorta. In comparison with control tissues, the grain counts in equal area samples show a 32% greater concentration in the hypertrophying hearts. The results indicate a significantly increased rate of incorporation of amino acid into the proteins of nodal tissues accompanying early hypertrophic changes.     

Junctional rhythm quantity and duration during slow pathway radiofrequency ablation in patients with atrioventricular nodal re-entry supraventricular tachycardia.

AIM: The occurrence of accelerated junctional rhythm during radiofrequency energy delivery at the region of the slow pathway is a well-recognized marker of successful treatment of atrioventricular nodal re-entry tachycardia (AVNRT). Our aim was to evaluate if the quantity and duration of accelerated junctional rhythm during radiofrequency ablation of the slow pathway is correlated with residual slow pathway conduction. METHODS AND RESULTS: Forty consecutive patients with AVNRT undergoing radiofrequency ablation of slow pathway who developed accelerated junctional rhythm during ablation were included. We compared accelerated junctional rhythm quantity and duration between two groups: group A, without echo beats and group B, with echo beats on post-ablation electrophysiology study. The total amount of accelerated junctional rhythm was significantly greater in group A than in group B [75.0 (63.5-165.0) vs. 36.0 (24.0-65.0), P=0.006], as well as total duration of accelerated junctional rhythm [47.0(33.5-81.0) s vs. 23.0 (16.0-42.0) s, P=0.006]. The cycle length of accelerated junctional rhythm did not differ between the two groups [510.0 (445.0-545.0) ms vs. 500.0 (450.0-585.0) ms, P=0.5). CONCLUSIONS: The amount and duration of accelerated junctional rhythm is correlated with the total abolishment abolition of slow pathway conduction. A higher amount and duration of accelerated junctional rhythm during radiofrequency applications may be an additional marker of successful ablation.