Electrical Activity During the P-R Interval

Hoffman, Brian F.; Cranefield, Paul F.; Stuckey, Jackson H.; Bagdonas, Albin A.; Piera, Juan

doi:10.1161/01.res.8.6.1200

Cited by 91 publications

(23 citation statements)

References 16 publications

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“…Activation of these sites is initiated intramurally and spreads bidirectionally toward both the endocardial and the epicardial surfaces, i.e., the reversal phenomenon (4,5,10,46,47). This phenomenon is readily explained by our finding of rapid intramural spread of excitation and by findings of others (12,33,48) that, although the anatomical Purkinje-papillary junction is found at the tip, the actual electrophysiological junction is at the base with resultant early activation of the latter. Activity initiated at the base of the papillary muscle should result in an endocardial and a deep spread of activation.…”

Section: Intramural Conductionsupporting

confidence: 52%

Glass Microelectrode Studies on Intramural Papillary Muscle Cells

Solberg

Singer

Eick

et al. 1974

Circulation Research

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Although the electrophysiological properties of intramural ventricular myocardial cells are important to an understanding of cardiac excitation and conduction, they have not been well defined. The paucity of information stems from limitations on the depth of penetration by glass microelectrodes and from difficulties in perfusing the deep layers. Therefore, a tissue slicing technique that satisfactorily exposes all the layers of a papillary muscle specimen from the endocardium to the epicardium was developed for electrophysiological examination. Glass microelectrodes were then used to explore these slice preparations to define the electrophysiological characteristics of intramural cells in the normal dog. Transmembrane potentials recorded from subendocardial and deep myocardial cells in the papillary muscle slices were comparable to those recorded from standard preparations. Similarities included action potential duration and configuration, relationships among resting potential, action potential configuration, and extracellular potassium concentration, and dependency of action potential duration on cycle length. However, the average magnitudes of measured electrophysiological characteristics were consistently greater in the subsurface cells tested in papillary muscle slices than they were in the surface cells tested in the standard preparations, i.e., resting potential was 2-4 mv more negative, action potential amplitude was 7-9 mv larger, and maximum rate of voltage change (maximum dV/dt) was 40-140 v/sec larger. Deep myocardial tissues also exhibited enhanced responsiveness (the curve relating activation potential to maximum dV/dt of the response shifted up and to the left), cell populations with large maximum dV/dt, and estimated conduction velocities in excess of three times those in the surface cell layers. These findings provide a reasonable explanation for (I) discrepancies between previously reported values for ventricular conduction velocity. (2) rapid impulse spread to the papillary muscle tip. and (3) bidirectional activation of the papillary muscle and large trabeculae. They also suggest the possibility of functional pathways that facilitate rapid activation of the deep myocardial lavers. KEY WORDS intramural cells papillary muscle slice intramural conduction intramyocardial cells electrophysiology• The electrical properties of endocardial and epicardial surface cells from the hearts of various mammalian species have been extensively charac- This work was supported in part by Grant 681875 from the Americsn Heart Association, by Grants A72-6 and C72-7 from the Chicago Heart Association, by the Reingold Estate, and by U. S. Public Health Service Training Grant TO-1-GM00162-14 from the National Institutes of Health.The original work was carried out in partial fulfillment of the requirements for a Ph.D. in Pharmacology by L. Solberg. Dr. Solberg was a J. B. Kahn. Jr. Fellow in Pharmacology and Dr. Singer is an Established Investigator of the American Heart Association.Please terized using intracel...

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Section: Intramural Conductionsupporting

confidence: 52%

Glass Microelectrode Studies on Intramural Papillary Muscle Cells

Solberg

Singer

Eick

et al. 1974

Circulation Research

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“…In addition, he was able to display interdigitating connections between the Purkinje fibers and ventricular muscles, as well as between the node and arterial muscles [2]. Electrical activity of the specialized conducting system of canine hearts has been recorded in situ through electrodes attached to the endocardium during total cardiopulmonary bypass [3]. Armiger et al [4] stated that the connective tissue of the trabeculae got from the puppies and the young dogs had little elastic fibers, but this element was well extended in the connective tissue of the adult dogs.…”

Section: Introductionmentioning

confidence: 99%

Distribution and Structure of Purkinje Fibers in the Heart of Ostrich (Struthio camelus) with the Special References on the Ultrastructure

Parto

Tadjalli

Ghazi

et al. 2013

International Journal of Zoology

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Purkinje fibers or Purkinje cardiomyocytes are part of the whole complex of the cardiac conduction system, which is today classified as specific heart muscle tissue responsible for the generation of the heart impulses. From the point of view of their distribution, structure and ultrastructural composition of the cardiac conduction system in the ostrich heart were studied by light and electron microscopy. These cells were distributed in cardiac conducting system including SA node, AV node, His bundle and branches as well as endocardium, pericardium, myocardium around the coronary arteries, moderator bands, white fibrous sheet in right atrium, and left septal attachment of AV valve. The great part of the Purkinje fiber is composed of clear, structure less sarcoplasm, and the myofibrils tend to be confined to a thin ring around the periphery of the cells. They have one or more large nuclei centrally located within the fiber. Ultrastructurally, they are easily distinguished. The main distinction feature is the lack of electron density and having a light appearance, due to the absence of organized myofibrils. P-cells usually have two nuclei with a mass of short, delicate microfilaments scattered randomly in the cytoplasm; they contain short sarcomeres and myofibrillar insertion plaque. They do not have T-tubules.

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“…But for a given preparation the interval remained constant. Judging from the location of the recording electrodes in reference to anatomical landmarks and comparing the configuration and temporal relation of the potential to the atrial and ventricular potentials with those obtained by previous workers (Burchell et al 1953, Hoffman et al 1959, 1960, the small spiky deflection is considered to be the electrical activity of the right bundle branch. With alteration of stimulus intervals, the time required by an impulse to travel from the atrium to the right bundle branch (AB interval) was changed in parallel with the AV interval.…”

Section: Effect Of Occlusion Of the Psa And Of The Asa On A V Conductionmentioning

confidence: 99%

“…Furthermore, the preparation permitted us the direct visual placement of recording electrodes at any position along the conducting pathways, as the Langendorff preparation (Alanis et al 1958) or the dog on cardio-pulmonary bypass (Hoffman et al 1959(Hoffman et al , 1960 did. The simulta neous recording of the electrical activities both from the right bundle branch and from the underlying myocardium, for example, revealed the differential effects on AB and BV conduction of ACh or l-NE given into the PSA and of ACh or l-NE given into the ASA.…”

Section: Effect Of Occlusion Of the Psa And Of The Asa On A V Conductionmentioning

confidence: 99%