Total Excitation of the Isolated Human Heart
TL;DR: In this paper, isolated human heart measurements were made from as many as 870 intramural terminals to obtain information concerning the time course and instantaneous distribution of the excitatory process of the normal human heart.
Abstract: To obtain information concerning the time course and instantaneous distribution of the excitatory process of the normal human heart, studies were made on isolated human hearts from seven individuals who died from various cerebral conditions, but who had no history of cardiac disease. Measurements were made from as many as 870 intramural terminals. In the isolated human hearts three endocardial areas were synchronously excited 0 to 5 msec after the start of the left ventricular activity potential. These areas increased rapidly in size during the next 5 to 10 msec and became confluent in 15 to 20 msec. The left ventricular areas first excited were (1) high on the anterior paraseptal wall just below the attachment of the mitral valve; (2) central on the left surface of the interventricular septum and (3) posterior paraseptal about one third of the distance from apex to base. The last part of the left ventricle to be activated usually was the posterobasal area. Endocardial activation of the right ventricle wa...
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TL;DR: The present article introduces the second part of “Recommendations for Standardization and Interpretation of the Electrocardiogram”, a project initiated by the Council on Clinical Cardiology of the American Heart Association and endorsed by the American College of Cardiology.
1,742 citations
TL;DR: The main shortcomings of conventional mapping-namely, prolonged x-ray exposure, low spatial resolution, and the inability to accurately navigate to a predefined site-can all be overcome with this new method.
Abstract: Background Cardiac mapping is essential for understanding the mechanisms of arrhythmias and for directing curative procedures. A major limitation of the current methods is the inability to accurately relate local electrograms to their spatial orientation. The objective of this study was to present and test the accuracy of a new method for nonfluoroscopic, catheter-based, endocardial mapping. Methods and Results The method is based on using a new locatable catheter connected to an endocardial mapping and navigating system. The system uses magnetic technology to accurately determine the location and orientation of the catheter and simultaneously records the local electrogram from its tip. By sampling a plurality of endocardial sites, the system reconstructs the three-dimensional geometry of the chamber, with the electrophysiological information color-coded and superimposed on the anatomy. The accuracy of the system was tested in both in vitro and in vivo studies and was found to be highly reproducible (SD, ...
847 citations
TL;DR: The fourth in a series of 6 documents focused on providing current guidelines for the standardization and interpretation of the electrocardiogram (ECG) was published by the American Heart Association as discussed by the authors.
842 citations
TL;DR: It is demonstrated that regional LV rotation and torsion can be measured accurately by STE, suggesting a new echocardiographic approach for quantification of LV systolic function.
Abstract: Background— Left ventricular (LV) torsion is due to oppositely directed apical and basal rotation and has been proposed as a sensitive marker of LV function. In the present study, we introduce and validate speckle tracking echocardiography (STE) as a method for assessment of LV rotation and torsion. Methods and Results— Apical and basal rotation by STE was measured from short-axis images by automatic frame-to-frame tracking of gray-scale speckle patterns. Rotation was calculated as the average angular displacement of 9 regions relative to the center of a best-fit circle through the same regions. As reference methods we used sonomicrometry in anesthetized dogs during baseline, dobutamine infusion, and apical ischemia, and magnetic resonance imaging (MRI) tagging in healthy humans. In dogs, the mean peak apical rotation was −3.7±1.2° (±SD) and −4.1±1.2°, and basal rotation was 1.9±1.5° and 2.0±1.2° by sonomicrometry and STE, respectively. Rotations by both methods increased (P<0.001) during dobutamine infus...
736 citations
TL;DR: The value of the transverse internal resistance can be accounted for on the ground of frequent branching in a three‐dimensional network and there is no need to make the additional assumption of current flow through lateral low resistance pathways between parallel fibres.
Abstract: Trabecular bundles from the right ventricle of calf hearts were used. Electrical properties measured by the application of longitudinal current were compared to those measured by the application of transverse current. 2. The following data were obtained on the basis of classical cable analysis: (i) a ratio of 3-0 for longitudinal to transverse conduction velocity, (ii) a ratio of 3-6 for intra- to extracellular longitudinal resistance, (iii) a ratio of 12-6 for intra- to extracellular transverse resistance, (iv) a ratio of 9-4 for intracellular transverse to intracellular longitudinal resistance, (v) a ratio of 2-7 for the extracellular transverse to the extracellular longitudinal resistance. 3. The disparity in conduction velocity could be explained on the sole grounds of differences in the resistivity of the intracellular and extracellular paths for current flow in the two directions, confirming theoretical predictions. 4. The value of the transverse internal resistance can be accounted for on the ground of frequent branching in a three-dimensional network. There is no need to make the additional assumption of current flow through lateral low resistance pathways between parallel fibres.
699 citations
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TL;DR: An account of experiments designed to investigate the cardiac action potential by applying suitable pulses of current at various stages in the cardiac cycle is contained.
Abstract: Microcapillaries with an external tip diameter of 0 5p. (Ling & Gerard, 1949) can be inserted into single fibres of the cardiac syncytium and may be used to record resting and action potentials. The technique has so far been applied to the frog ventricle (Woodbury, Hecht & Christopherson, 1951) and to 'false tendons' of the dog and kid heart (Draper & Weidmann, 1951). The conductive system of the kid contains typical Purkinje fibres which are larger in diameter (40-lOOup.) than ordinary heart muscle fibres and which are only slightly contractile. In this preparation it is possible to insert two microelectrodes into the same fibre and to leave them intracellular for many minutes. Polarizing current can be applied through one electrode and the change in membrane potential -resulting from current flow recorded through the other electrode. The present paper contains an account of experiments designed to investigate the cardiac action potential by applying suitable pulses of current at various stages in the cardiac cycle.
468 citations
TL;DR: The results suggest that the conducting tracts in the right ventricle of man may differ from those of the dog, and the electrocardiogram is dominated by right ventricular effects and vice versa.
158 citations
TL;DR: A description of total excitation of the adult human heart is given and the value of the intrinsicoid deflection in precordial leads are briefly discussed.
Abstract: A description of total excitation of the adult human heart is given. Atrial testing stimuli were used for the analysis of the genesis of attacks of supraventricular tachycardia in the W.P.W. syndrome; the short PR, normal QRS-syndrome; incomplete left bundle branch block; atrial echo beats; and gap in atrioventricular conduction. The E.C.G. in cardiomyopathy and the value of the intrinsicoid deflection in precordial leads are briefly discussed.
140 citations
TL;DR: The interatrial band (Bachmann's bundle) was studied both in situ, in the adult dog, and in vitro, using excised canine atria, and contains two fiber types; in addition to ordinary atrial muscle, specialized conducting fibers are present in the inter atrial band.
Abstract: The interatrial band (Bachmann's bundle) was studied both in situ, in the adult dog, and in vitro, using excised canine atria. Electrograms recorded from this structure in the intact animal had a double intrinsic deflection during sinus rhythm, and responded to rapid rates of atrial stimulation with alternation in both configuration and cycle length. Potassium infusions which produced atrial arrest with a sinoventricular rhythm did not abolish electrical activity in the interatrial band. Single fibers of the interatrial band, studied in vitro with microelectrodes, had distinctive transmembrane potentials different from those of ordinary atrial muscle fibers. Action potentials were characterized particularly by a high rising velocity (maximum dv/dt), of the same magnitude as that recorded from Purkinje fibers, and a prominent plateau. These fibers were sensitive to acetylcholine and more resistant to potassium arrest than ordinary atrial fibers. Conduction velocity in the interatrial band was consistently ...
140 citations
TL;DR: An understanding of electrocardiographic complexes will be achieved when the potential a t a given body-surface point can be predicted from a knowledge of ventricular depolarization and repolarization pathways, and basic principles of current flow in volume conductors are understood.
Abstract: An understanding of electrocardiographic complexes will be achieved when the potential a t a given body-surface point can be predicted from a knowledge of ventricular depolarization and repolarization pathways. To do this for QRS we must have exact information on three factors. First, we must know the time course and magnitude of potential changes across the membranes of the ventricular syncytium as depolarization takes place.’ Second, we must know the pathway of ventricular depolarization. Third, we must understand the basic principles of current flow in volume conductors2 and the modifications of these principles necessitated by the resistive inhomogeneity of the tissues and the irregular shape of the body. The potential Ep a t a given point P in a homogeneous conducting medium is a product (1) of the solid angle fl subtended a t P by the boundary between resting and active tissue, and (2) of the dipole moment per unit area CP across the boundary between resting and active tissue. To determine the solid angle 3, a sphere of radius R is drawn with origin a t P and intersecting all lines from P to the boundary. A is then the area of the sphere within the lines from P to the boundary, and the solid angle is equal to A/RZ. The dipole moment per unit area, CP, is determined by dividing the voltage V across the “cell” membrane by 4 ~ . Then 9 = V / h
119 citations