Functional and morphological evidence for a ventricular conduction system in zebrafish and Xenopus hearts

2003 ◽  
Vol 284 (4) ◽  
pp. H1152-H1160 ◽  
Author(s):  
David Sedmera ◽  
Maria Reckova ◽  
Angela deAlmeida ◽  
Martina Sedmerova ◽  
Martin Biermann ◽  
...  
Keyword(s):  
Polysialic Acid ◽  
Conduction System ◽  
Model Organisms ◽  
Morphological Evidence ◽  
Apical Region ◽  
Atrioventricular Canal ◽  
Organ Systems ◽  
Ventricular Activation ◽  
Activation Times ◽  
Ventricular Conduction

Zebrafish and Xenopus have become popular model organisms for studying vertebrate development of many organ systems, including the heart. However, it is not clear whether the single ventricular hearts of these species possess any equivalent of the specialized ventricular conduction system found in higher vertebrates. Isolated hearts of adult zebrafish ( Danio rerio) and African toads ( Xenopus laevis) were stained with voltage-sensitive dye and optically mapped in spontaneous and paced rhythms followed by histological examination focusing on myocardial continuity between the atrium and the ventricle. Spread of the excitation wave through the atria was uniform with average activation times of 20 ± 2 and 50 ± 2 ms for zebrafish and Xenopus toads, respectively. After a delay of 47 ± 8 and 414 ± 16 ms, the ventricle became activated first in the apical region. Ectopic ventricular activation was propagated significantly more slowly (total ventricular activation times: 24 ± 3 vs. 14 ± 2 ms in zebrafish and 74 ± 14 vs. 35 ± 9 ms in Xenopus). Although we did not observe any histologically defined tracts of specialized conduction cells within the ventricle, there were trabecular bands with prominent polysialic acid-neural cell adhesion molecule staining forming direct myocardial continuity between the atrioventricular canal and the apex of the ventricle; i.e., the site of the epicardial breakthrough. We thus conclude that these hearts are able to achieve the apex-to-base ventricular activation pattern observed in higher vertebrates in the apparent absence of differentiated conduction fascicles, suggesting that the ventricular trabeculae serve as a functional equivalent of the His-Purkinje system.

scholarly journals Characterization of embryonic cardiac pacemaker and atrioventricular conduction physiology in Xenopus laevis using noninvasive imaging

2004 ◽  
Vol 286 (6) ◽  
pp. H2035-H2041 ◽  
Author(s):  
Heather L. Bartlett ◽  
Thomas D. Scholz ◽  
Fred S. Lamb ◽  
Daniel L. Weeks
Keyword(s):  
Xenopus Laevis ◽  
Congenital Heart ◽  
Morphological Changes ◽  
Heart Defects ◽  
Cardiac Pacemaker ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Model Organisms ◽  
Morphological Evidence ◽  
Video Images

Congenital heart defects often include altered conduction as well as morphological changes. Model organisms, like the frog Xenopus laevis, offer practical advantages for the study of congenital heart disease. X. laevis embryos are easily obtained free living, and the developing heart is readily visualized. Functional and morphological evidence for a conduction system is available for adult frog hearts, but information on the normal properties of embryonic heart contraction is lacking, especially in intact animals. With the use of fine glass microelectrodes, we were able to obtain cardiac recordings and make standard electrophysiological measurements in 1-wk-old embryos ( stage 46). In addition, a system using digital analysis of video images was adapted for measurement of the standard cardiac intervals and compared with invasive measurements. Video images were obtained of the heart in live, pharmacologically paralyzed, stage 46 X. laevis embryos. Normal values for the timing of the cardiac cycle were established. Intervals determined by video analysis ( n = 53), including the atrial and ventricular cycle lengths (473 ± 10 ms and 464 ± 19 ms, respectively) and the atrioventricular interval (169 ± 5 ms) were not statistically different from those determined by intrathoracic cardiac recordings. We also present the data obtained from embryos treated with standard medications that affect the human conduction system. We conclude that the physiology of embryonic X. laevis cardiac conduction can be noninvasively studied by using digital video imaging. Additionally, we show the response of X. laevis embryonic hearts to chronotropic agents is similar but not identical to the response of the human heart.

scholarly journals Relationship Between the ECG, Ventricular Activation, and the Ventricular Conduction System in Ostium Primum ASD

Circulation ◽  
1973 ◽  
Vol 48 (3) ◽  
pp. 556-564 ◽  
Author(s):  
JOHN P. BOINEAU ◽  
E. NEIL MOORE ◽  
DONALD F. PATTERSON
Keyword(s):  
Conduction System ◽  
Ventricular Activation ◽  
Ventricular Conduction

Effects of mechanical loading on early conduction system differentiation in the chick

2010 ◽  
Vol 298 (5) ◽  
pp. H1571-H1576 ◽  
Author(s):  
Barbora Sankova ◽  
Jakub Machalek ◽  
David Sedmera
Keyword(s):  
Silicone Oil ◽  
Conduction System ◽  
Primary Ring ◽  
Morphological Examination ◽  
Atrioventricular Canal ◽  
Activation Patterns ◽  
Conduction Pathway ◽  
Myocyte Proliferation ◽  
System Differentiation ◽  
Ventricular Conduction

The primary ring, a horseshoe-shaped structure situated between the left and right ventricle and connected superiorly to the atrioventricular canal, is the first specialized fast ventricular conduction pathway in the embryonic heart. It has been first defined immunohistochemically and is characterized as a region of slow myocyte proliferation. Recent studies have shown that it participates in spreading the ventricular electrical activation during stages preceding ventricular septation in the mouse, chick, and rat. Here we demonstrate its presence using optical mapping in chicks between embryonic days (ED) 3–5. We then tested the effects of hemodynamic unloading in the organ culture system upon its functionality. In ED3 hearts cultured without hemodynamic loading for 24 h, we observed a significant decrease in the percentage activated through the primary ring conduction pathway. A morphological examination revealed arrested growth, collapse, and elongation of the outflow tract and disorganized trabeculation. A similar reversal toward more primitive activation patterns was observed with culture between ED4 and ED5. This phenotype was completely rescued with the artificial loading of the ventricles with a droplet of silicone oil. We conclude that an appropriate loading is required during the early phases of the conduction system formation and maturation.

Ultrasound examination of pregnant women in diagnosing fetal cardiac pathology

2020 ◽  
Vol 69 (2) ◽  
pp. 43-50
Author(s):  
Viktoria A. Lim
Keyword(s):  
Pregnant Women ◽  
Fetal Heart ◽  
Fetal Echocardiography ◽  
Heart Defects ◽  
Care Service ◽  
Ultrasound Screening ◽  
Atrioventricular Canal ◽  
Cardiac Pathology ◽  
Organ Systems ◽  
Atrioventricular Canal Defect

Hypothesis/aims of study. Fetal heart defects are the most common malformations causing infant mortality. The task of the obstetric care service is to make a timely diagnosis, which includes high-quality ultrasound screening and, if necessary, fetal echocardiography. This study aimed to compare fetal echocardiography with postpartum echocardiography. Study design, materials and methods. 101 pregnant women with both isolated fetal heart defects and combined pathology were examined for the period 20172019. Results. The greatest number of heart defects was detected at 2331 weeks of gestation. The structure of the malformations is diverse, the most common one being a complete form of the atrioventricular canal defect. In multiple pregnancies, complex heart defects were often combined with abnormalities in other organ systems. Conclusion. It is recommended to describe the heart structure in detail from 2122 weeks of pregnancy. If cardiac pathology is detected in utero, it is mandatory to conduct an examination of other fetal organs.

scholarly journals Stretch–excitation correlation in the toad heart

2020 ◽  
Vol 223 (23) ◽  
pp. jeb228882
Author(s):  
Vladimir A. Vityazev ◽  
Jan E. Azarov
Keyword(s):  
Bolus Injection ◽  
Ventricular Myocardium ◽  
Bufo Bufo ◽  
Interquartile Range ◽  
Video Recordings ◽  
Ventricular Activation ◽  
Potential Mapping ◽  
Activation Times ◽  
The Right ◽  
Activation Sequence

ABSTRACTThe activation sequence of the ventricular myocardium in ectotherms is a matter of debate. We studied the correlation between the ventricular activation sequence and the pattern of local stretches in 13 toads (Bufo bufo). Epicardial potential mapping was done with a 56-lead sock array. Activation times were determined as dV/dt (min) in each lead. Initial epicardial foci of activation were found on the left side of the ventricular base, whereas regions on the apex and the right side of the base demonstrated late activation. Video recordings (50 frames s−1) showed that the median presystolic stretch in left-side ventricular regions was greater than that in right-side regions [4.70% (interquartile range 3.25–8.85%) versus 1.45% (interquartile range 0.38–3.05%), P=0.028, respectively]. Intracardiac bolus injection elicited ventricular activation with a similar sequence and duration. Thus, ventricular areas of earliest activation were associated with greater presystolic stretch, implying the existence of a stretch–excitation relationship in ectotherm hearts.

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