Extracardiac Factors Research Articles

Myocardial performance after excision of the extrinsic cardiac nerves in the dog.

• The performance of the heart in the intact subject is determined by the complex interplay of cardiac and extracardiac factors; the initial length of the myocardial fibers and the state of activity of the cardiac autonomic nerves are most important. The profound changes in cardiac behavior that attend excitation of the cardiac autonomic nerves have led to the concept of neurogenic dominance in the control of cardiac output, particularly in situations that strongly constrain the cardiovascular system. This concept is basic to an evaluation of the mechanisms by which the heart responds to changes in the peripheral circulation and has important implications in clinical cardiac transplantation. In this review, the behavior of the denervated heart in different stressful situations is considered; the presentation is limited to studies in which dogs have been chronically deprived of both sympathetic and parasympathetic nerves. The role of cardiac receptors and their afferent innervation has recently been reviewed and is not discussed in this paper (1, 2). TECHNIQUES OF CARDIAC DENERVATION

Abnormal Electrocardiogram Without Heart Disease

To the Editor.— Unusual electrocardiographic pattern may arise from extracardiac body movements and electrical or mechanical interferences. 1,2 Recently we observed an unusual electrocardiogram simulating non specific ST changes in a 7-year-old boy who has apparently no heart disease. This (Figure, top) was thought to be abnormal until a second ECG (bottom) using another machine, showed a normal record. This case illustrates again that extracardiac factors should be considered when evaluating electrocardiographic abnormalities.

Experimentally induced automatism in rat isolated ventricle

Exposure to isoprenaline plus electrical stimulation of the isolated right ventricle of the rat produces stable ventricular automatic activity of various types. The incidence of these different types of ventricular arrhythmia is tabulated and analysed. The technique allows the antiarrhythmic activity of drugs to be studied at cellular level where extracardiac factors are excluded.

Ventricular fibrillation

Fibrillation is a chaotic asychronous activity of cardiac muscle. The process can be initiated by rapid impulse formation from a single focus, or by reentry. There are many possibilities for the development of asynchrony in a normal or abnormal myocardium. The analysis of rhythm disturbances immediately preceding fibrillation and the records of transmembrane action potentials from the fibrillating heart do not contribute appreciably to the understanding of the process itself. The mechanisms causing fibrillation are difficult to identify because (1) in most types of experimental fibrillation one cannot localize the fiber or the group of fibers in which the first wave of reentry or the disorganized activity begins; (2) in many types of experimental fibrillation the onset of disorganized activity is due to a combination of factors rather than to any single factor; and (3) an exploration of all cardiac and extracardiac factors that might have contributed to the development of fibrillation rarely has been carried out in any single experiment. No single mechanism or factor can be proposed to explain all types of spontaneous or experimentally produced fibrillation. However, a certain critical mass of myocardium and a certain critical relation between conduction velocity and duration of refractory period in certain parts of the myocardium are required to initiate and maintain the disorder. The factors that increase vulnerability to fibrillation include increased automaticity, currents resulting from differences in the membrane potential during activity or at rest, imbalance between conduction velocity and refractoriness, and nonhomogeneous refractoriness. The role of these factors in experimentally induced and spontaneous fibrillation is discussed. Electrophysiologic alterations produced by stimulation during the vulnerable period, characteristics of the early premature impulses, and factors contributing to reentry are described. The most important conditions facilitating spontaneous ventricular fibrillation are slow heart rate, prolongation of the Q-T interval, electrolyte imbalance, hypothermia, drugs increasing automaticity, slow conduction, disturbances of nervous regulation and myocardial ischemia. Fibrillation in the early phase of ischemia may be due to electrophysiologic abnormalities induced by potassium liberated from the ischemic myocardium.

Textbook of Vectorcardiography

Complexity of presentation has been the bedevilment of teaching methods in vectorcardiography. This text successfully escapes via a style which minimizes theoretic intricacies while retaining the practicalities of a sophisticated diagnostic method. Each short chapter is complemented by a few well-chosen references. Strong points include clear presentations of sequential vectors by number and distribution and of angular orientation of effective lead axes and relative lead sensitivity. Tables and figures effectively summarize and depict normal orientations of maximal and component vectors and loop inscriptions. The presentation of LVH is a model of clarity, with appropriate nods at prevailing hypotheses for QRS voltage increase and angular abnormalities. The authors avoid the pitfalls of many texts by treating left axis deviation independently, by appropriate emphasis on extracardiac factors and clear distinction from cor pulmonale in the VCG of emphysema, and by healthy skepticism regarding some interpretations and criteria. This book can be heartily

The effects of training on the heart rate during arm and leg exercise.

AbstractThe effect on heart rate obtained by training of the arm and leg muscles respectively was studied in healthy subjects. Training performed by arm work on a bicycle ergometer caused a significant reduction of the heart rate during this type of exercise but not during leg work. Neither did training performed with the legs reduce the group mean heart rate during arm work. In two subjects, however, training of the leg muscles caused heart rate reduction during leg as well as arm work. A further decline in heart rate during arm work was obtained by a subsequent arm-training program in these two subjects. It is concluded that a substantial part of the effect of short-term physical training on the heart rate derives from extra cardiac factors, i. e. alterations in the trained muscles.

Coronary artery disease and the concept of cardiac failure

A plea is made to abandon the abstract, nonoperational term heart failure and to describe the ways in which the heart functions abnormally. Such an operational approach clearly shows that any type of failure—clinical, biophysical, biochemical, molecular—may be present in the absence of congestive heart failure, a type that requires the participation of extramyocardial factors. Furthermore, the operational approach clearly indicates that one cannot distinguish the cause from effect without knowledge of the temporal relations of the two. Lastly, an event may be the effect of one phenomenon and the cause of another which, in turn, can modify the first. It is because of these vicious circles that death is usually not caused by exhaustion of the heart but by extracardiac factors that are incompatible with life. The fundamental cause of failure of the ischemic heart to function normally lies in loss of contractile power of the block of muscles supplied by the occluded artery. The degree and subsequent types of failures will depend upon the size of the block of tissue deprived of its blood supply, its location, reactive fibrosis, the capacity of the uninvolved portion of the myocardium to compensate for the lesion, the extracardiac effects of abnormal vascular pressures, reflex and hormonal relations to the injury and the integrity of organs other than the heart. Each of these factors is discussed.

Electrocardiographic Findings in 98 Consecutive Non-penetrating Chest Injuries

Ninety consecutive patients with nonpenetrating chest injuries were observed for evidence of cardiac trauma. Eleven were arbitrarily considered to have sustained severe trauma, 18 light trauma and 69 moderately severe. No signs or symptoms of traumatic cardiac involvement were found on clinical and radiologic examinations. Electrocardiography revealed abnormalities related to trauma in 19 cases (19 per cent). In 15 cases changes were limited to flattening of inversion of T wave in leads III, aVF and V1 or in flattening of T waves in one or two chest leads. In five cases, which are reported in detail, there were diffuse light depression of the ST segment and shallow inversion of the T waves. Such changes have not been attributed to myocardial injury, since several extracardiac factors, such as tachycardia, emotion, pulmonary circulation derangements, pulmonary dysfunction, appeared to be more convincing factors in their production.

Serum Enzyme Determinations in Diagnosis of Ischemic Heart Disease

The SGOT test is said to have greater sensitivity than electrocardiography in the diagnosis of myocardial infarction. The LDH test is of particular aid when testing is started several days following the infarction. The temporal relationship betiveen infarction and enzyme elevations has an important bearing on the determinations. Consideration must also be given to the many extracardiac factors that affect the enzyme levels.

Circulatory Effects of Acute Expansion of Blood Volume:

The maximum cardiac output that can be achieved during exercise might be limited either by extracardiac factors influencing ventricular filling, or by the heart itself. In order to investigate this problem, the effect on the cardiac response to maximum exertion of an acute expansion of blood volume was studied in six men with essentially normal cardiovascular systems. Augmentation of blood volume produced by infusion of 1000 to 1200 ml of the subject's own blood resulted in a small increase in central venous pressure at rest (avg = + 1.9 mm Hg) and a substantial increase in cardiac output (avg = + 1.47 liters/min). During exercise, however, the expansion of blood volume caused a large increase in central venous pressure (avg = + 7.4 mm Hg), but no significant increase in cardiac output or maximum O 2 uptake. This finding suggests that the maximum cardiac output is not restricted by extracardiac factors and that the upper limit must therefore be determined by the heart itself.

Extracardiac factors contributing to hypotension during coronary occlusion

1. 1. The sudden occlusion of a major coronary artery in the dog or cat has been shown to produce a reflex decrease in sympathetic activity to the vascular bed of the hindlimb in the dog and to the heart in the cat. The peripheral vasodilatation occurred without the activation of the cholinergic vasodilator nerves. 2. 2. The data suggest that the receptors involved in this reflex are located in the ventricle. They may be ventricular stretch receptors responding to the abnormal stimulus of systolic expansion of the infarcted portion of myocardium and compensatory dilatation of the remainder of the heart, or they may be specific “ischemia receptors.” 3. 3. The afferent pathway for this reflex is the vagus nerves. The control mechanism is not dependent on the participation of cortical or hypothalamic centers since the reflex is present in decerebrate animals. 4. 4. The possible participation of this reflex in the hypotension that accompanies clinical myocardial infarction is discussed, and the hypothesis is advanced that the pathophysiology of myocardial infarction may involve not only a decrease in functional cardiac muscle mass but also a failure of certain neurocirculatory compensatory mechanisms.

Electrocardiographic studies in Asian influenza

Eighty-seven University of North Carolina students who had clinical and serologic evidence of infection with type A influenza viruses related to Asian strains were studied electrocardiographically, both during the illness and after recovery. The electrocardiograms were evaluated by comparison with those of a control series similar in age, sex, and social distribution. Extracardiac factors were taken into consideration. Twelve electrocardiograms were considered to be abnormal because of S-T segment deviation, depression of T waves, and auricular arrhythmias. Four of these abnormalities, including all the arrhythmias, occurred in the recovery stage. It was concluded that although these changes were minor, they could have been caused by myocarditis due to infection with influenza virus.

Reversible forms of heart disease.

For many years the diagnosis of heart disease connoted a life of invalidism with probable death by virtue of the affliction. In recent years, however, the marked advances in medical science have not only enabled the heart patient to live a more useful life but also have shown that many forms of heart disease are entirely curable. It is important to remember that a normal heart or one that is only slightly diseased may show symptoms that are solely the expression of some extracardiac disease, and that this extracardiac condition may manifest itself entirely or largely in the cardiovascular system. As a result, the cardiac symptoms may be so marked that they completely overshadow the underlying extracardiac disease. As a result the patient is often considered a cardiac invalid, whereas recognition of the effect of the extracardiac disease with treatment directed to the extracardiac condition usually brings about a reversibility in the cardiovascular symptoms. Failure on our part to recogni e that many extracardiac diseases are expressed clinically through the cardiovascular system has led to unnecessary invalidism and even death. In every cardiac patient we must constantly be aware of the possibility that the heart itself may not be actually diseased but that rather it is acting secondarily to other conditions in the body. It is only by recognizing these extracardiac factors before they produce structural changes in the heart muscle that the treatment of the extracardiac disease may be instituted sufficiently early for the patient to be cured. It is the purpose of this paper to point out in a general way some conditions that are manifested entirely or largely through the cardiovascular system, with the result that a normal or a previously damaged heart may be precipitated into actual cardiac failure. It is apparent that all of the diseases that may produce such changes cannot be listed in the space permitted, and under these circumstances only a brief mention will be made of the various illnesses that can affect the cardiovascular system. We are familiar with the symptoms presented by the markedly obese patient. He frequently complains of dyspnea, palpitation and precordial distress. Physical examination may often reveal an

DUPLICATE MEASUREMENTS OF CIRCULATION TIME MADE WITH THE SACCHARIN METHOD

Article1 July 1943DUPLICATE MEASUREMENTS OF CIRCULATION TIME MADE WITH THE SACCHARIN METHODKURT H. ESSER, M.D., KURT BERLINER, M.D.KURT H. ESSER, M.D.Search for more papers by this author, KURT BERLINER, M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-19-1-64 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptMeasurements of the velocity of blood flow, repeated at intervals on the same patient, are sometimes used to evaluate the treatment of congestive heart failure. It is obvious that such serial tests can be of value only if their results chiefly reflect changes in the degree of heart failure and are not materially influenced by other factors. That such extracardiac factors are operative has recently been proved by Lilienfeld and Berliner1who used alpha lobeline hydrochloride as an agent and found wide "spontaneous" variations in the results of duplicate measurements. The present study was undertaken to determine whether duplicate measurements...Bibliography1. LILIENFELDBERLINER AK: Duplicate measurements of circulation time made with the alpha lobeline method, Arch. Int. Med., 1942, lxix, 739. CrossrefGoogle Scholar2. FISHBERGHITZIGKING AMWHFH: Measurement of circulation time with saccharin, Proc. Soc. Exper. Biol. and Med., 1933, xxx, 651. CrossrefGoogle Scholar3. TARROPPENHEIMERSAGER LBSRV: The circulation time in various clinical conditions determined by the use of sodium dehydrocholate, Am. Heart Jr., 1933, viii, 766. CrossrefGoogle Scholar4. WEISSROBBBLUMGART SGPHL: The velocity of blood flow in health and disease, Am. Heart Jr., 1929, iv, 670. Google Scholar This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAffiliations: New York, N. Y.*Received for publication June 1, 1942.From the Department of Cardiology, Sydenham Hospital, New York, N. Y. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics Cited byAcute cardiac tamponade pathologic physiology, diagnosis and managementEFFECT OF POSTURE ON VENOUS VELOCITY, MEASURED WITH 24NaClAlgunos aspectos de las cardiopatías y la mecánica circulatoria durante el embarazoDetermination of the Circulation Time in Children by the Decholin Method 1 July 1943Volume 19, Issue 1Page: 64-69KeywordsBlood flowHeart failure ePublished: 1 December 2008 Issue Published: 1 July 1943 PDF downloadLoading ...

Low voltage of the QRS waves in the electrocardiogram, with especial reference to lead IV

Analysis was made of 300 cases showing low voltage of the QRS complexes of the elecrtrocardiogram. Three groups of 100 cases each were compared with one another; Group 1 having low voltage of QRS in the classical leads but normal voltage in the precordial (fourth) lead, Group 2 having low voltage of QRS in the fourth lead alone, and Group 3 having low QRS complexes in all four leads. Evidence of heart disease was found in only 57 per cent of the entire series, and only 47 per cent of the group with low voltage in the chest lead alone had evidence of heart disease. Generalized debilitating diseases, changes in the position of the heart, series, and only 47 per cent of the group with low voltage in the chest lead alone had evidence of heart disease. Generalized debilitating diseases, changes in the position of the heart, and changes in the conductivity of adjacent tissues seemed to be important factors in the production of low voltage of the QRS complexes. Furthermore, the thickness of the chest wall and the position of the precordial electrode influenced the voltage of QRS in Lead IV. Heart disease was of no greater relative importance than extracardiac factors in cases showing extreme reduction in ARS voltage (for instance, 0.3 mv. or less). However, in such cases the responsible factor was likely to be more obvious than in cases with moderate degrees of low voltage. Analysis of the literature likewise indicates the importance of the factors mentioned above. Even in the patients with considerable heart disease, fluctuations in the voltage, with changes in the state of compensation, suggested that the heart lesions were of less importance than the secondary manifestations of heart failure in the production of lowered potential. Ten per cent of the entire series showed no evident explanation of any sort for the occurrence of low voltage, being apparently healthy normal persons in every respect. Our study indicates that the solitary finding of low voltage of the QRS complexes is of little or no diagnostic value regarding the presence or absence of heart disease or of any other trouble. The wider use of electrocardiograms on normal people outside of hospitals will probably show a higher incidence of low voltage than the literature suggests at present.

Studies of the electrical field of the heart. I. Invariants of the electrocardiogram

1. 1. Every electrocardiogram depends on the electrical changes in the heart muscle and on extracardiac factors, some of which are independent of, and others dependent on, the particular lead employed. 2. 2. By using many different leads (about 150) on one individual the invariance of various properties of the electrocardiogram was investigated to determine which properties were invariants, i. e., independent of the particular lead used. 3. 3. The only known independent invariants of the electrocardiogram are its time relations, namely, the sequence of cycles, their rhythm, the division of each cycle into three complexes, the duration of P, of QRS, of QRST, of T, and of the P-R (P-Q) and S-T intervals. 4. 4. All other properties studied, such as direction, amplitude, contour, notching, slurring, the algebraic sum of the initial and final ventricular deflections, and the Einthoven quantity were found to be noninvariants.

THE EFFECT OF ADRENALIN ON THE BLOOD PRESSURE OF THE ELASMOBRANCH, SQUALUS ACANTHIAS

1. Intravenous injection of adrenalin, in doses as low as 2 cc. of 1 : 500,000, produced long-sustained pressor effects in Squalus acanthias, together with marked increase of pulse pressure and a tendency toward decrease of heart rate.2. Subsequent doses of adrenalin following doses stronger than 1: 500,000 were ineffective. This is interpreted as being due to already existing maximum pressor action. Doses subsequent to a dose of 2 cc. of 1: 500,000 were effective.3. The pressor effect is interpreted as being due to extra-cardiac factors, peripheral to the gill capillaries, but the region of action of the adrenalin was not located.

ISOLATED CONGENITAL DEXTROCARDIA

<h3>ROENTGEN OBSERVATIONS</h3> The roentgenogram serves to disclose extracardiac factors for the displacement of the heart. The position of the mediastinal contents and the nature of the shadows in the pulmonary fields indicate whether the displacement is the result of traction of a fibrotic process, tumor or fluid. Mobility of the diaphragm and change in the position of the apex with change of posture signify the absence of pleuropulmonary and diaphragmatic adhesions. In the uncomplicated mirror-picture dextrocardia, the contour of the heart, with definite apex pointing to the right, is the mirror-image of the normal situation and identical with the heart in situs inversus. The course of the aortic arch, however, varies crossing the right bronchus more frequently than the left. In complicated cases the apical region is rounded and the normal cardiac contour modified by the hypertrophy of the right side of the heart, rarely the left, so that distinction

Electrocardiographic Study of Movements of the Heart with Change of Posture.

The human electrocardiogram, as recorded, leading off from points on the surface of the body, is influenced by extracardiac factors, particularly by the effects of the tissues about the heart and the relation of the heart to the surrounding tissues. It is possible for a variation in the electrocardiogram to occur by a change in the extracardiac relations, even though the processes within the heart remain unaltered. Several observers have noted a variation in the form of the electrocardiogram on change of position of the body from the reclining to the lateral positions. There is no agreement as to the type and degree of the alterations nor as to the mechanism underlying these changes. The previous observations have been limited to a small group of subjects and no analysis of a sufficiently large number exists to justify definite conclusions. In the present study, electrocardiograms were made of 60 individuals in 3 positions, in the reclining, in the left lateral and right lateral positions. The material consisted of normal subjects and of cardiac patients in whom a fixed heart was improbable, such as cases of hypertension heart and coronary disease. The latter were included to determine the effect of cardiac enlargement. The influence of such factors as habitus of the individual, size and displacement of the heart, was noted. Of the 60 cases, 55, or 91%, presented some definite electrocardiographic alteration on change of position of the body.