Hans H. Hecht

Recommendations for Standardization of Leads and of Specifications for Instruments in Electrocardiography and Vectorcardiography

By COMMITTEE MEMBERS: CHARLES E. KOSSMANN, M.D., CHAIRMAN, DANIEL A. BRODY, M.D., GEORGE E. BURCH, M.D., HANs H. HECHT, M.D., FRANKLIN D. JOHNSTON, M.D., CALVIN KAY, M.D., EUGENE LEPESCHKIN, M.D., HUBERT V. PIPBERGER, M.D., AND by MEMBERS OF THE SUBCOMMITTEE ON INSTRUMENTATION: * HUBERT V. PIPBERGER, M.D., CHAIRMAN, GERHARD BAULE, PH.D., ALAN S. BERSON, M.S., STANLEY A. BRILLER, M.D., DAVID B. GESELOWITZ, Ph.D., LEO G. HORAN, M.D., AND OTTO H. SCHMITT, Ph.D.

Atrioventricular and intraventricular conduction: Revised nomenclature and concepts☆

Abstract Under the organizing chairmanship of the late Hans Hecht, a symposium on Atrioventricular and Intraventricular Conduction was held in Chicago on May 28–29, 1970 under the auspices of the American College of Chest Physicians and the Center for Continuing Education, University of Chicago. After an extended discussion on nomenclature in this area by more than 150 participants, the present authors convened themselves as a self-appointed committee to create a framework for a revised nomenclature.

Electrophysiological Study of Human Heart Muscle

Membrane potential changes in human ventricular and atrial muscle, excised from patients undergoing open-heart surgery, were recorded by micro-electrodes in vitro. Mean ventricular resting and action potentials were −87 mv. and 115 mv., respectively. The mean atrial resting potential was −70 mv., mean action potential 75 mv. Two forms of atrial action potential were found, one having conventional contour, the other with prominent spike and plateau. A disturbance in repolarization is believed to underlie the latter type of atrial potential cycle. The relation between the upstroke velocity of the action potential and the extracellular sodium concentration and membrane potential was shown to be similar to that in other mammalian cardiac tissue. The mean conduction velocity determined in ventricular fibers (1.3 M./sec.) was somewhat greater than that of the dog, and the possible relationship to hypertrophy of the cardiac fibers in the preparations studied is described. The effect of increased rate and anoxia in reducing the action potential duration is like that found in the hearts of other mammals. The conductance type of inhibition was produced by acetylcholine in spontaneously beating atrial tissue. The excitatory effect of epinephrine was preceded by a transitory inhibition. The basic mechanisms underlying the action potential, automaticity and transmitter effects, derived from investigation of other mammalian cardiac tissue are applicable to the human heart.

Acute Pulmonary Edema of Altitude Clinical and Physiologic Observations

Three separate episodes of acute pulmonary edema are described that developed in two otherwise healthy individuals during heavy exertion at high altitudes. Detailed physical examination and laboratory studies failed to demonstrate pulmonary infection or cardiac disease. Data obtained by cardiac catheterization during one of these episodes revealed elevation of the pulmonary artery pressure and a normal left atrial pressure. This syndrome appears to be the consequence of pulmonary vascular obstruction distal to the capillary bed, presumably in the pulmonary veins. It is brought about by exposure of susceptible individuals to high altitudes, and is completely reversed by oxygen administration.

Brisket disease: II. Clinical features and hemodynamic observations in altitude-dependent right heart failure of cattle

Abstract In cattle grazing during the summer months at altitudes between 8,000 and 12,000 feet (2,500 to 3,700 meters) in Utah and Colorado severe congestive heart failure develops. The disease is apparently the consequence of severe pulmonary hypertension which develops in this species in response to moderate altitudes. This form of chronic mountain sickness has many similarities to pulmonary hypertensive heart disease in man. It differs from Monges disease in certain significant aspects. It is assumed that the peculiar structure of the pulmonary vascular bed in this species causes an excessive vasoconstrictive response at a reduction in partial pressure of oxygen which is still easily tolerated by man.

Potential variations of the right auricular and ventricular cavities in man.

Abstract 1.1. Electrocardiograms from the endocardial surfaces of the right side of the heart and from the large veins have been obtained by means of a catheter-like electrode inserted through the right or left antecubital veins. 2.2. The potential variations which have been recorded are in agreement with the basic concepts of origin, spread, and distribution of the action current of the heart upon which modern electrocardiographic interpretation is based. The conclusions which have been drawn from animal experiments can safely be applied to human electrocardiography. 3.3. The potential variations recorded from unipolar right arm leads represent auricular deflections similar to those present in the large veins. The ventricular deflection in V R is a faithful reproduction of records obtained from the endocardial surface of the upper portion of the right auricle. They represent a mixture of potentials from the right and left ventricular cavities.

Effects of Cardiac Glycosides upon the Electrical Activity of Single Ventricular Fibers of the Frog Heart, and Their Relation to the Digitalis Effect of the Electrocardiogram

Using microelectrodes having an external diameter of less than 1, &mgr;, potential variations of single cardiac fibers were obtained from frog ventricular muscle in situ. The normal membrane potential consists of a rapid depolarization and slow recovery, the latter occurring in three distinct phases. Digitalis glycosides alter profoundly the slopes of these various phases and drastically shorten the entire period of recovery. The characteristic cardiac action potential is thus converted into a spike which resembles the electrical events recorded for skeletal muscle or nerve. These changes occur independently of mechanical systole which remains essentially unaltered. The deformation of the action potential occurs uniformly throughout the ventricular muscle. They are related to the RS-T segment depression of the surface electrocardiogram which in this instance cannot be explained as being caused by a failure of the diastolic repolarization of the endocardial surface but must be an expression of uniform shortening of the entire process of recovery.

Model studies on the effect of the intracardiac blood on the electrocardiogram.

Abstract Perfused dog bladders to simulate the intracardiac blood mass were placed in an electrolytic tank in the shape of an elliptical cylinder. An artificial dipole was placed adjacent to the preparation, and wall and limb potentials were measured. Measurements were made with the dipole axis tangential, radial, or at intermediate angles to the bladder wall. In one group of experiments the leads were measured for ratios of bladder fluid to tank fluid of from about 0.14 to 1.20. In the second series of experiments the ratio was kept constant at 0.15, and field potentials were measured as a function of the distance between the dipole and the bladder. The results show that the contribution of a dipole component to the potential at a given electrode depends on the ratio of the resistivity of the blood to the resistivity of myocardial and thorax tissue, the distance of the dipole from the cavity, its direction relative to the cavity wall, as well as on the orientation of the dipole with respect to the electrode.

Membrane Resting and Action Potentials of Single Cardiac Muscle Fibers

An initial report is made on the electrocardiogram of a single heart muscle cell in vivo. The potential variations obtained by electrodes placed on opposite sides of the membrane of a heart muscle fibre are 50 to 100 times as large as those recorded by standard limb leads. The observations support the assumption that during activation the cell interior becomes positive with respect to its surrounding (depolarization, followed by polarization reversal). Induced alterations in shape and form of the action current of a single heart muscle fiber should provide further insight into the nature of the normal and abnormal electrocardiogram.

ANOMALOUS ATRIOVENTRICULAR EXCITATION: PANEL DISCUSSION

H. H. HECHT (University of Utah, Salt Lake City, Utah) : Although we are not primarily concerned with the clinical and physiological aspects of abnormal ventricular excitation, it would seem beneficial to follow the searching analysis of the normal propagation of depolarization presented on the preceding pages with an account of a peculiar syndrome that may occur in otherwise normal individuals-a syndrome characterized by an unusual deformation of the early portion of the QRS complex. Detailed electrocardiographic analyses have led to certain inevitable conclusions that presented the anatomist and the histologist with pointed questions. FIGURE 1 illustrates the general configuration of the entity, a short PR interval with a wide QRS complex in a subject who a t other times displayed an entirely normal atrioventricular (AV) and intraventricular conduction, and who, in the sequence from which the illustration was taken, alternated between normal and abnormal complexes. When the two types of complexes are superimposed (FIGURE 2) it is clear that a relationship exists between the normal and the abnormal complex: the QRS deformation involves only the early portion of QRS, and ventricular depolarization obviously begins earlier in the abnormal complex, encroaching upon the normal PR interval. PR is, therefore, short, while PS and the interval from the beginning of P to the summit of R are identical with those of the normal complexes. Because of its shape, the abnormal early portion of QRS has been termed the “delta wave.”’ If the disorder is due to some unusual spread of excitation over ventricular musculature, the spread of recovery will be altered correspondingly and, therefore, T will change in size and direction (FIGURES 1 and 2). The basic myocardial function will remain unchanged and the total area of QRS and T, the ventricular gradient, will therefore remain unaltered. Some frontal plane measurements for normal and abnormal complexes are listed in TABLE 1. I t is generally referred to as the Wolff-Parkinson-White (WPW) syndrome according to the authors of the first definite account: although isolated cases were reported before, the first by Wilson in 1915.3 The more descriptive term “anomalous atrioventricular excitation,” coined in 194S14 implies no more than the existence of an unusual excitatory sequence, the presence of which cannot be denied. We have made this term the title for the panel. Prinzmetal has demonstrated that experimental procedures involving the atrioventricular junction may result in similar electrocardiographic complexes, and he has proposed the concept of “accelerated conduction.llS Others have demonstrated that complexes of this type may occur as a consequence of damage to certain portions of the ventricular musculature, including the septum.6