Structure and function of the sinus node, AV node and his bundle of the human heart: Part I—Structure

2002 ◽  
Vol 45 (3) ◽  
pp. 235-267 ◽  
Author(s):  
Thomas N. James
Keyword(s):  
Human Heart ◽  
Sinus Node ◽  
Structure And Function ◽  
Av Node ◽  
His Bundle ◽  
And Function

Differential effect of verapamil isomers on sinus node and AV junctional region

1983 ◽  
Vol 244 (1) ◽  
pp. H80-H88
Author(s):  
H. O. Gloor ◽  
F. Urthaler
Keyword(s):  
Sinus Rhythm ◽  
Sinus Node ◽  
Conduction Time ◽  
Av Node ◽  
Junctional Rhythm ◽  
His Bundle ◽  
Sinus Node Artery ◽  
Rate Dependent ◽  
Av Conduction ◽  
Differential Responsiveness

The l- and d-isomers of verapamil were selectively perfused into the sinus node artery and atrioventricular (AV) node artery of 48 dogs. Injection of l-verapamil into the sinus node artery during sinus rhythm and into the AV node artery during AV junctional rhythm depresses both sinus rhythm and AV junctional rhythm significantly more than does the d-isomer. l-Verapamil is three to four times more powerful than d-verapamil. Injection of the isomers into the AV node artery during sinus rhythm rapidly impairs AV conduction. Increments in conduction time are measured exclusively at the level of the A-H interval of the His bundle electrogram, and l-verapamil is six times more powerful than d-verapamil. Neither d- nor l-verapamil in concentrations that exert a profound negative chronotropic effect or cause AV block, has any significant effect on transatrial or His bundle conduction. Thus these concentrations of d-verapamil have little or no significant effect on the fast sodium channel, but both verapamil isomers affect the slow channel. The main difference in action between l- and d-verapamil appears to be only quantitative in nature. The sinus node is significantly more sensitive to the negative chronotropic action of verapamil than is the AV junctional pacemaker, and this differential responsiveness appears to be related to the different intrinsic rates of the two pacemakers. During sinus rhythm (either in the presence or absence of atropine) sinus node automaticity is less affected than AV conduction when verapamil is given parenterally. We propose that this greater negative dromotropic effect of verapamil is also in part due to a rate-dependent process, since during sinus rhythm AV junctional cells have to be depolarized at frequencies significantly higher than their intrinsic rates.

Anatomy of the sinus node, av node, and his bundle of the heart of the sperm whale (Physeter macrocephalus), with a note on the absence of an os cordis

1995 ◽  
Vol 242 (3) ◽  
pp. 355-373 ◽  
Author(s):  
Thomas N. James ◽  
Keishiro Kawamura ◽  
Frits L. Meijler ◽  
Shoji Yamamoto ◽  
Fumio Terasaki ◽  
...  
Keyword(s):  
Sinus Node ◽  
Sperm Whale ◽  
Physeter Macrocephalus ◽  
Av Node ◽  
His Bundle

Distribution of cholinesterase within the sinus node and AV node of the human heart

1966 ◽  
Vol 155 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Thomas N. James ◽  
Caryle A. Spence
Keyword(s):  
Human Heart ◽  
Sinus Node ◽  
Av Node

How many patients treated for bradycardia may be eligible for His bundle pacing?

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
R Chattopadhyay ◽  
P Chousou ◽  
R Thomas ◽  
J O"brien ◽  
F Pierres ◽  
...  
Keyword(s):  
Heart Block ◽  
Sinus Node ◽  
Conduction System ◽  
Ventricular Pacing ◽  
Av Node ◽  
His Bundle ◽  
His Bundle Pacing ◽  
Funding Sources ◽  
System Disease ◽  
Class Iib

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Pacing-Induced Cardiomyopathy (PICM) can lead to significant morbidity, requiring treatment by device upgrade procedures. The risk of occurrence is directly related to the burden of right ventricular pacing, which can be reduced by careful device programming. When frequent ventricular stimulation cannot be avoided, pacing the conduction system may offer an alternative to myocardial pacing and reduce the risk of PICM. The most recent international pacing guidelines recommend that His-bundle pacing should be considered among 1) patients with EF 36-50% and expected to require >40% ventricular pacing (Vp > 40%) (class IIa); and 2) patients requiring pacing who have block at the level of the AV node (class IIb). Purpose This study sought to determine how many patients undergoing bradycardia pacing would have fulfilled those criteria. Methods This was a single-centre retrospective study over a 5 year period to the end of April 2020. Demographic and clinical details of patients receiving device implants were obtained from the Pacing Service Database, along with the indication for pacing, electrocardiographic and echocardiographic data. A cardiology consultant with a special interest in pacing reviewed each case with regards to the likelihood of requiring >40% ventricular pacing. Heart block at the level of the AV node was considered present if patients presented with a narrow QRS in conjunction with second or third degree heart block. Results 1,265 patients underwent pacemaker implant for bradycardia during the study period, 888 for conduction system disease (198 second degree block, 333 complete heart block), 349 for sinus node disease and 28 for other indication. Figure 1 gives a breakdown of patients with conduction system block according to i) level of block; ii) ejection fraction; iii) expectation or not of Vp > 40%.  In total, 166 patients had a class IIa indication for His-bundle pacing. 227 patients had block at the level of the AV node, of whom 36 also fulfilled the class IIa criteria for His-bundle pacing; 191 patients (16% of the total) had a sole class IIb indication for His-bundle pacing. Adjusting for the 176 patients who did not undergo echocardiography, up to an additional 45 patients may be expected to have an indication for His-bundle pacing Conclusion As many as 32% of patients in a bradycardia pacing population may be eligible for His-bundle pacing. This has significant implications for training and service provision. Abstract Figure 1. Flowsheet showing distribution

scholarly journals Resistance training alters skeletal muscle structure and function in human heart failure: effects at the tissue, cellular and molecular levels

2012 ◽  
Vol 590 (5) ◽  
pp. 1243-1259 ◽  
Author(s):  
Michael J. Toth ◽  
Mark S. Miller ◽  
Peter VanBuren ◽  
Nicholas G. Bedrin ◽  
Martin M. LeWinter ◽  
...  
Keyword(s):  
Heart Failure ◽  
Skeletal Muscle ◽  
Resistance Training ◽  
Human Heart ◽  
Structure And Function ◽  
Human Heart Failure ◽  
Muscle Structure ◽  
And Function

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Osseointegration interface of calcified bone and endosseous implants

1992 ◽  
Vol 50 (2) ◽  
pp. 1096-1097
Author(s):  
K.E. Krizan ◽  
J.E. Laffoon ◽  
M.J. Buckley
Keyword(s):  
Structure And Function ◽  
Titanium Implants ◽  
En Bloc ◽  
Endosseous Implants ◽  
Ultrastructural Studies ◽  
The Past ◽  
Cacodylate Buffer ◽  
One Year ◽  
And Function

With increase use of tissue-integrated prostheses in recent years it is a goal to understand what is happening at the interface between haversion bone and bulk metal. This study uses electron microscopy (EM) techniques to establish parameters for osseointegration (structure and function between bone and nonload-carrying implants) in an animal model. In the past the interface has been evaluated extensively with light microscopy methods. Today researchers are using the EM for ultrastructural studies of the bone tissue and implant responses to an in vivo environment. Under general anesthesia nine adult mongrel dogs received three Brånemark (Nobelpharma) 3.75 × 7 mm titanium implants surgical placed in their left zygomatic arch. After a one year healing period the animals were injected with a routine bone marker (oxytetracycline), euthanized and perfused via aortic cannulation with 3% glutaraldehyde in 0.1M cacodylate buffer pH 7.2. Implants were retrieved en bloc, harvest radiographs made (Fig. 1), and routinely embedded in plastic. Tissue and implants were cut into 300 micron thick wafers, longitudinally to the implant with an Isomet saw and diamond wafering blade [Beuhler] until the center of the implant was reached.

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