Showing papers in "American Journal of Cardiology in 1964"

Detecting the threshold of anaerobic metabolism in cardiac patients during exercise

Abstract: The measurement of the respiratory gas exchange ratio (R) during a standard exercise test is used to detect the onset of anaerobic metabolism during exercise, which results from failure of the cardiovascular system to supply the oxygen requirements of the tissues. The method described uses end-tidal gas concentrations to calculate R while the exercise test is taking place. Blood sampling is unnecessary, and the results can be determined during the test, thus avoiding exhaustive exercise. The method provides an objective measurement of one of the factors influencing exercise tolerance.

Left retrograde cardioangiography in acquired cardiac disease: Technic, indications and interpretations in 700 cases∗

Abstract: Application of retrograde left cardioangiography to 700 patients, both adults and children, with acquired valvular diseases is described. The technic employed for the test is described. Pressures from the aorta and left ventricle are obtained during the same procedure as angiography to determine whether stenosis of the aortic valve is present. The method may be used to estimate the degree of aortic or mitral insufficiency or both. Mitral stenosis may be identified by a fixed filling defect of the left ventricular cavity. The value of this information in the surgical management of many forms of cardiac disease is emphasized. Complications have occurred infrequently and, in most instances, the patients have responded to appropriate therapy. Three deaths occurred. These were caused by ventricular fibrillation in 1 patient and cardiac tamponade in 2. The most common complication was thrombosis of the femoral artery at the site of arteriotomy. This complication occurred in about 4 per cent of cases; but in none did gangrene occur, and pulsatile flow was restored in all cases by immediate re-exploration of the femoral artery as soon as the diagnosis was made.

Anatomic types of single or common ventricle in man. morphologic and geometric aspects of 60 necropsied cases.

Abstract: In 60 necropsied cases of single or common ventricle in man, four major unrelated ventricular malformations were found: (1) absence of the right ventricular sinus, in 47 cases (78%), designated type A; (2) absence of the left ventricular sinus, in 3 cases (5%), type B; (3) absence or rudimentary development of the ventricular septum, in 4 cases (7%), type C; and (4) absence of both ventricular sinuses and of the ventricular septum, in 6 cases (10%), type D. Three types of relationship between the great arteries were present: a normal (solitus) interrelationship, in 9 cases (15%), designated type I; d -transposition, the transposed aortic valve lying to the right (dextro, or d ), relative to the transposed pulmonary valve, in 25 cases (42%), type II; and l -transposition, the transposed aortic valve lying to the left (levo or l ), relative to the transposed pulmonary valve, in 26 cases (43%), type III. In none was the inversus interrelationship, type IV, displayed. Three types of visceral and atrial situs were found: solitus, or normal, in 50 cases (83%); inversus, an exact apparent mirror image of normal, in 2 cases (3%); and heterotaxy, the uncertain visceral and atrial situs associated with asplenia, in 8 cases (13%). The 60 cases were classified segmentally, according to the anatomy of the three cardiac segments: the great arteries, the ventricular sinuses, and the atria. The classic single ventricle with a rudimentary outlet chamber was found morphologically to be a large left ventricle with a right ventricular infundibulum, the sinus of the right ventricle being absent (type A). The myocardium of the right ventricular infundibulum, of the right ventricular sinus, and of the left ventricular sinus was identified by the distinctive gross morphologic characteristics of each. The planes of the atrial and ventricular septa, and the relationships between the great arteries at the semilunar valves, were measured as projections upon the horizontal plane, relative to the anteroposterior line. An approach to cardiac anatomy is presented which is segmental, morphologic and geometric. This approach has angiocardiographic, electrocardiographic and embryologic applications.

The syndrome of supravalvular aortic stenosis, peripheral pulmonary stenosis, mental retardation and similar facial appearance.

Abstract: A series of 10 patients with supravalvular aortic stenosis and a similar facial appearance with mental retardation is described The patients have identical dental malformations in addition, and 7 patients examined by right heart angiocardiography have multiple, bilateral peripheral pulmonary stenosis Peripheral pulmonary stenosis is also expected to be present in the remaining patients The clinical features and the findings obtained at cardiac catheterization, angiocardiography and operation are discussed Chromosome studies on 3 of these patients have been negative It is suggested that defective formation of the aortic septum is responsible for the coexistence of peripheral stenosis in both great vessels The malformation is characterized by hypoplasia of several organs The findings represent a new syndrome: supravalvular aortic stenosis, peripheral pulmonary stenosis, mental retardation, a certain facial appearance and complex dental malformations

Anatomic types of congenital dextrocardia: diagnostic and embryologic implications.

Abstract: The anatomic findings in 51 necropsied cases of congenital dextrocardia are presented. The diagnostic and embryologic implications of these findings are assessed. A new general anatomic classification is proposed which is equally applicable to right-sided and to left-sided hearts, either with two well-developed ventricles or with single (common) ventricle. The proposed classification, which is specifically designed to facilitate accurate diagnosis of the relative locations of the cardiac chambers by current investigative methods, is based upon two considerations: (1) the type of viscero-atrial situs present, and (2) the type of cardiac loop which coexists. The type of visceral situs, established radiologically, always is the same as the atrial situs. Thus, the visceral situs indicates the atrial locations with virtually complete accuracy. The type of relationship between the great arteries at the semilunar valves, determined angiocardiographically, indicates the type of cardiac loop present and, hence, the relative location of each ventricle. Thus, the great arteries identify the ventricles with great accuracy. Three types of relationship are considered, an appreciation of which greatly simplifies and clarifies one's understanding of congenital heart disease: (1) viscero-atrial; (2) bulboventricular (great arteries to ventricles); and (3) bulboventriculovisceral (types of cardiac loop relative to types of viscero-atrial situs). The malformation which recently has been regarded as “classic dextroversion” very probably is nonexistent. The incidence of the tetralogy of Fallot in dextrocardia has been greatly overestimated, probably because of confusion with transposition, pulmonary stenosis and ventricular septal defect. The mirror-imagery of inversion is considered to be a biologic illusion. Rudimentary spleen (polysplenia) appeared to be a forme fruste of asplenia. Posterior transposed aorta is described.

Effects of a six month program of endurance exercise on the serum lipids of middle-aged men

Abstract: HE EFFECT of six months of physical conditioning upon a number of physiologic variables has been investigated in a group of previously sedentary middle-aged men.’ This study was performed to help lay the groundwork for a possible large-scale, long term investigation of whether or not regular exercise protects against the development of coronary heart disease. A major aim of the present study was to try to

Effect of pacemaker site on cardiac output and ventricular activation in dogs with complete heart block

Abstract: The sequence of ventricular activation was recorded in dogs with complete heart block while the heart was paced from each of 11 ventricular sites; cardiac output was determined while the heart was paced from each of 8 ventricular sites at rates of 90, 120 and 150 per minute. The following conclusions were reached: 1. 1. Each ventricular pacemaker site results in a specific pattern of ventricular activation. 2. 2. Differences of over 100 per cent in cardiac output were recorded when the heart was paced from different ventricular sites at the same pacemaker rate. 3. 3. The optimal pacemaker rate is dependent upon the ventricular site selected for the implantation of the pacemaker electrode and the condition of the cardiovascular system. 4. 4. The hemodynamic effectiveness of the left ventricular pacemaker sites is inversely related to the muscle mass activated by muscle conduction. 5. 5. The hemodynamic effectiveness of right ventricular pacemakers is dependent upon the pattern of left ventricular depolarization. 6. 6. The hemodynamically more effective left ventricular pacemaker sites resulted in higher cardiac outputs than any of the right ventricular sites tested. 7. 7. The changes in cardiac performance when the heart is paced from various pacemaker sites is best explained by varying degrees of asynchrony during ventricular contraction and/or the position of the atrioventricular valves early in ventricular systole. 8. 8. The clinical implications of this study have been considered.

Syndrome of congenital cardiac disease with asplenia: Distinction from other forms of congenital cyanotic cardiac disease

Abstract: The pathologic and clinical features in 17 patients with congenital cardiac disease in association with agenesis of the spleen have been presented. Pathologically, the cases fell into two groups as follows: those with two ventricles and a large ventricular septal defect (10 cases), and those with a common ventricle (7 cases). Conotruncal abnormalities were present in each case. These consisted of pulmonary stenosis or atresia (17 cases) and transposition of the great vessels (16 cases). Ventricular and infundibular inversion was common, occurring in 8 cases with two ventricles and 5 cases with common ventricle, respectively. “Endocardial cushion defects” were found in each of the 17 cases. Persistent common atrio-ventricular canal was present in 16, and an “ostium primum” atrial septal defect, in association with mitral atresia, was seen in the seventeenth case. Atrial septal defects were present in each case. In 13 instances, the only remnant of the atrial septum was a narrow strand of tissue between two large coexisting defects (the condition referred to herein as common atrium). The common occurrence of anomalies of the systemic and pulmonary veins was noted. Among the 17 cases, bilateral superior venae cavae with absent coronary sinus were found in 15 and anomalous pulmonary venous connections occurred in 12. Malposition of the viscera was represented by the finding of mirror-image dextrocardia in 1, dextroversion of the ventricles in 9 and abdominal heterotaxia in 13 cases. The finding of the cardiac apex and stomach on opposite sides was noted primarily in cases with common ventricle and may be helpful in the clinical diagnosis of this condition. There was a tendency toward bilateral symmetry of the organs characterized by the universal presence of bilateral three-lobed lungs, a large, transverse liver, absence of the spleen (the only unilateral organ in the body) and by the very frequent presence of common atrium, persistent common atrioventricular canal and bilateral superior venae cavae, and malrotation of the intestine. The patients presented, usually as young infants, with obvious cyanosis from birth. Electrocardiographically, the occurrence of left axis deviation and a counterclockwise QRS loop in the frontal plane suggesting the presence of an A-V commune defect, may help separate these patients with complicated cardiac malformations and asplenia from other patients with cyanotic congenital cardiac disease but with less complex malformations and without asplenia. In 5 cases of common ventricle and asplenia, the “A-V commune electrocardiogram” was absent, even though a complete form of persistent common atrioventricular canal was present in each. Routine thoracic and abdominal roentgenograms, as well as angiocardiographic studies, have proved to be the most effective means of establishing the clinical diagnosis of the asplenic syndrome. The angiocardiogram may identify many of the intracardiac and associated vascular anomalies found in this condition. The clinical features which are most useful in identifying cases of cyanotic congenital cardiac disease associated with asplenia include: (1) hematologic signs of asplenia; (2) electrocardiographic features of persistent common atrioventricular canal; and (3) radiologic evidence of hepatic symmetry, evidence of diminished pulmonary blood flow, and transposed great vessels.

Obesity and cardiac performance

Abstract: In association with consistent increases in stroke volume and a high incidence of systemic and/or pulmonary arterial hypertension, the cardiac work of very obese patients at rest was considerably greater than that predicted for normotensive subjects at ideal body weight. Although this change was effected chiefly by increased left ventricular work, and the latter was roughly correlated with the amount of excess body weight, variable increases in right ventricular work resulted in a lack of correlation between total cardiac work and the amount of excess weight. Though pulmonary hypertension secondary to an increase in left ventricular filling pressure usually occurred in the very obese patients of this series under conditions of moderate exercise, the increment in cardiac output per unit increment in oxygen consumption with exercise was within normal limits. Because of the need to move excess body weight, at any given level of activity the cardiac workload was considerably greater for the obese subjects than for individuals at ideal body weight. Cardiac enlargement and increased heart weight were found quite regularly in very obese subjects, increasing in rough proportion to the amount of excess body weight. The increased heart weight was due to muscular hypertrophy involving the left ventricle or both the left and right ventricles. Neither fatty infiltration of the myocardium nor isolated right ventricular hypertrophy was observed. Cardiac failure occurred in 8 per cent of the extremely obese patients in this series, involving a high cardiac output and left ventricular or biventricular insufficiency. It has been proposed that myocardial hypertrophy and failure derive from the increased cardiac workload present at rest and during exercise. Heart failure due to obesity generally responded well to bed rest, digitalis, diuretics, dietary sodium restriction and measures usually effective in managing heart failure due to other causes. Effective long term therapy necessarily involved weight reduction.

Experience with "cardioversion" of atrial fibrillation and flutter.

Abstract: Synchronized direct current countershock, “cardioversion,” was used in 70 patients on 94 occasions for reversion of atrial fibrillation or flutter. The method and anesthetic technics are described. A modification of the size and location of the electrode has decreased the incidence of minor discomfort resulting from the procedure and lowered the amount of energy necessary for successful cardioversion. In 90 of 94 episodes, or in 66 of 70 patients, the arrhythmia was restored to sinus rhythm. With a follow-up period of from 1 to 9 months, 52 of 66 patients (79%) remained in sinus rhythm. Fourteen patients (21%) reverted to atrial fibrillation despite multiple cardioversions and maximally tolerated quinidine therapy. Certain factors appear to decrease the chances of maintaining sinus rhythm: duration of fibrillation, type of valvular lesion, functional classification and previous quinidine failure. The advantages anticipated with the restoration of sinus rhythm are discussed. The emergency indication and contraindications are outlined. A broad policy of selection of patients for cardioversion is suggested. The reasons for this approach are the high degree of acute success (94%), the low incidence of complications (5%) and success in maintaining sinus rhythm (79%) for a short follow-up Period.

Endocardial cushion defects. specific diagnosis by angiocardiography.

Abstract: 1. 1. The anatomy and embryology of endocardial cushion defects are reviewed. 2. 2. Angiocardiographic deformities of the left ventricular outflow region and of the mitral valve are described which we believe to be characteristic and diagnostic of endocardial cushion defects. This method appears to be the most accurate single diagnostic technic available for the identification of these lesions. 3. 3. This study is based on a review of 16 cases of cushion defects and over 200 left ventricular angiocardiograms in a wide variety of congenital cardiac disorders.

Preinfarction syndrome—Management and follow-up

Abstract: The clinical and electrocardiographic characteristics of the preinfarction or intermediate coronary syndrome, which form a distinct and clinically recognizable pattern in many cases, are summarized in order to facilitate recognition of this important entity in practice. The high incidence (40.6%) of acute myocardial infarction within three months of onset of the intermediate coronary syndrome is stressed to encourage attempts at prophylaxis. Previous attempts of other workers in this direction are briefly reviewed. The protective role of anticoagulant therapy against cardiac infarction in 360 cases of the preinfarction syndrome is investigated. The results of such therapy in 190 patients are compared with those of conservative therapy in 156 patients. Acute myocardial infarction developed within three months in 36.3 per cent of the treated cases and 48.7 per cent of the controls. The mortality of infarcted cases was 26.1 per cent for the treated as against 48.1 per cent for the untreated cases with infarctions. While 18 deaths were reported in the treated group (190 patients) 37 died in the control group (156 patients). The localization or site of myocardial ischemia in the preinfarction phase as well as that of myocardial infarction in the later stages (whenever possible) was delineated in our cases. A relative preponderance of anterior over posterior wall involvement was obvious in each case. A clear-cut and predictable relationship could not be established between the site of the initial ischemia on the one hand and that of the subsequent myocardial infarct on the other. Although the present series is rather small for accurate appraisal of the prophylactic potentialities of anticoagulants, the general impression afforded by the data favors a routine adoption of anticoagulant therapy as a safeguard against myocardial infarction in such cases. In view of our results, the prompt and adequate administration of anticoagulants appears desirable as a routine prophylactic measure against myocardial infarction in cases of the preinfarction syndrome.

Physical activity and cardiovascular health.

Abstract: 1. 1. A review of investigations on the relation of physical activity to cardiovascular health and disease has been undertaken, with a brief discussion of some mechanisms that might play a part. 2. 2. There is a suggestion that recent activity is more important than activity earlier in life; even a light or moderate amount of physical activity may have significance. Encouraging as this is, most studies are of occupational activity and might not have direct applicability to physical activity undertaken as preventive therapy. 3. 3. We believe that the evidence that increased physical activity might be beneficial is sufficient to justify further extensive studies. More information is needed concerning the mechanisms of the possible benefits. 4. 4. The proof of the preventive therapeutic value of activity programs must come from observations of significant numbers of the population at risk. We favor an experimental design with active intervention and randomization of subjects. There is much virtue in a study of men with high indexes of risk relative to coronary heart disease. 5. 5. There is a pressing need to enlist and train more personnel to undertake the numerous pilot studies that are needed and the larger, more definitive studies that should follow. 6. 6. Increased communication and joint planning among physicians, physical educators, physiologists and biometricians are needed.

Clinical observations using the electrocardiocorder-avsep continuous electrodiographic system. tentative standards and typical patterns.

Abstract: We have described characteristic patterns observed using the Electrocardiocorder-AVSEP system for recording continuous electrocardiograms on both active and inactive subjects. We have extended previously well recognized observations made in conventional electrocardiography to the effect that the S-T segment in the normal varies somewhat from time to time, and T wave varies much more. We have shown examples in normal subjects of unusually flat ST-T segments with unusual variation in contour. We have also developed some appreciation of how often and how much the total AVSEP pattern can change during dynamic situations, especially the magnitude of normal T wave changes. The appearance of common arrhythmias as seen in this system, as well as some of the artifacts associated with it, has also been demonstrated. Examples of how this system develops patterns which differ in some respects from those seen in conventional electrocardiograms have been described and illustrated, especially those differences which arise from the nature of this new electrocardiographic recording and presentation system. (Examples are the features we have termed for convenience the pre-T notch and the post-T dip.) The reliability of the Electrocardiocorder-AVSEP system as originated at the Holter Foundation Laboratory has been demonstrated under a wide variety of circumstances during an extended series of trials. We emphasize the need for familiarity with the idiosyncrasies of this system and its patterns before drawing clinical conclusions from the observations. This partial review of our experiences with the Electrocardiocorder-AVSEP system as used in 230 subjects establishes these new devices as practical tools for observing electrocardiographic phenomena continuously during a wide range of dynamic situations.

Open heart surgery in jehovah's witnesses.

Abstract: Open heart surgery using cardiopulmonary bypass has not been used for Jehovah's Witnesses because of their religious convictions and a church law forbidding blood transfusion. Development of bypass technics which utilize only blood substitutes for priming have made such procedures acceptable to these patients. More than 450 patients have been operated upon by using 5% dextrose in water prime, disposable oxygenators and normothermia. Seven Jehovah's Witnesses were operated upon without administration of blood before, during or after operation with one death from postoperative hemorrhage. The 6 surviving patients had a satisfactory recovery. The hemoglobin concentration and hematocrit one week after operation revealed no change in 1 patient, approximately 25 per cent fall in 4, and severe anemia in 1 after aortic valvulotomy.

Sphygmomanometer cuff size and the accuracy of indirect measurement of blood pressure

Abstract: While it is well known that too narrow a sphygmomanometer cuff may give erroneously high indirect blood pressure readings, particularly in subjects with thick arms, it has not been generally appreciated that a cuff supplied with a rubber bag which is too short to encircle the upper arm may cause a similar error. Auscultatory pressure readings obtained with two cuffs, one with a bag 12 by 23 cm. and the other with that of 14 by 40 cm., were compared with direct intraarterial pressure recording in 53 subjects. The large bag gave systolic values 3.0 ± 1.16 mm . Hg too low, and diastolic (phase v) values 1.4 ± 1.26 mm . Hg too high. With the small bag the error depended on the site of wrapping; as applied on the biceps it gave a better agreement with the systolic (0.5 ± 1.71 mm . Hg too high), but a poorer one with the diastolic pressure (7.6 ± 2.0 mm . Hg too high). As applied on the triceps, the small bag gave systolic values 5.5 ± 1.91 mm . Hg too high; the diastolic values were also 4.6 ± 2.36 mm . Hg on the high side. With the large bag the random error was significantly smaller than with the smaller bag in either position, both for systolic and diastolic pressure. The disappearance of the sounds (phase v) was closer than muffling (phase iv) to the intraarterial diastolic pressure. In this series, the arm circumference as such had no effect on the error of the indirect blood pressure measurement. However, the thickness of the triceps skinfold was negatively correlated with the error of the systolic measurement when a small cuff was used, and with that of the diastolic phase IV measurement with both cuffs. With the large cuff and the phase V criterion, the thickness of the subcutaneous fat introduced no systematic error.

Refinements in method of evaluation and physical conditioning before and after myocardial infarction

Abstract: A 54 year old white man with hypertension, obesity and an elevated serum cholesterol level volunteered for a physical training program. During the sixth week he became ill, and a repeated work-capacity test revealed physiologic evidences of myocardial insufficiency. The pre-exercise serum glutamic oxaloacetic transaminase level was elevated. A routine electrocardiogram four hours later revealed evidence of an acute inferoseptal myocardial infarction. The course of the disease was uneventful and uncomplicated. Two months after infarction the patient resumed a physical activity program which provided for a slow increase in metabolic demands compatible with his capacity. Repeated work-capacity tests 20 and 23 weeks after infarction showed that he responded to training in exactly the same manner as has been observed in normal, healthy individuals. At that time he was normotensive, with a normal serum cholesterol concentration and near-normal body weight. The capacity for adequate cardiorespiratory adjustments to high metabolic demands was rated as “good.” This study illustrates how performance tests can be used in evaluating the work capacity and progress of a cardiac patient.

Biological significance of cardiac hypertrophy.

Abstract: Conditions that increase the force of contraction of the wall of a cardiac chamber on a short term basis are accompanied by an increase in the oxidative metabolism of the myocardium per unit mass of tissue per beat. When this is maintained over long periods, hypertrophy of muscle fibers develops. It serves to increase the contractile force of the wall by virtue of a thicker wall and restores the myocardial metabolism per unit mass of tissue per heart beat. This condition prevails in the early stages of pathologic hypertrophy which is not associated with failure and may be considered a “useful” response from the standpoint of myocardial energetics. As hypertrophy progresses slowly, discrepancy seems to arise between the mass of muscle tissue and the coronary supply, resulting in some degree of nutritional insufficiency. Destruction and fibrosis of some fibers ensue. The remaining fibers hypertrophy further. Metabolic abnormalities due to coronary insufficiency and other poorly understood disturbances ultimately lead to failure of the myocardium. From this standpoint, hypertrophy is a deleterious process since, in the long run, the hypertrophied myocardium is prone to fail sooner than otherwise.

Clinical experiences of a surgeon in the use of heparin.

Abstract: Intermittent intravenous injections of heparin for the treatment of acute deep venous thrombosis were used for the first time at the Department of Surgery, General Hospital, Mariestad, Sweden This form of therapy, combined with free movements of the affected limb and early ambulation, was started in October 1940 and has been used continuously since In a period of 18 years, 1940 to 1958, 937 cases were treated A dose of 150 mg (15,000 units) was injected intravenously as soon as thrombosis had been diagnosed Additional similar doses were given at four-hour intervals, except that no injections were given during the night On the subsequent days, three or four doses of the same size were given After three to four days the temperature generally had returned to normal and edema and tenderness had disappeared Injections of heparin were then decreased to two, and the patient was allowed out of bed Treatment was discontinued on the next day, and on the following day the patient could usually be discharged from the hospital In specified cases a slightly modified procedure was employed When massive pulmonary embolism was the predominant feature, a more concentrated heparinization was made during the first 24 hours No determinations of the coagulation time were made in the course of routine treatment They were regarded as superfluous, and their omission did not result in any overdosage of heparin In 95 per cent of the cases the course of recovery was entirely normal Edema and tenderness subsided in a few days, and the temperature and pulse returned to normal after a further day or two The mean duration of recumbency was 44 days Prior to any form of treatment, symptoms of pulmonary embolism were present in 59 of the 937 cases Many of these patients were in poor condition, and 10 had had repeated attacks With the exception of two, who died from a complicating bronchopneumonia, all patients recovered after heparin therapy The normal course of recovery was interrupted in one way or the other in 47 (5%) of the 937 cases Seven deaths occurred, including those mentioned above Recurrence of the thrombotic process, making further heparinization necessary, was observed in 24 Instances (26%) A slight hemorrhagic tendency was recorded 14 times (15%) The complication was harmless In none of the cases was it found necessary to administer antidotes The conclusion is drawn that hemorrhage is an uncommon complication, occurring only once or twice in a hundred patients, of a mild nature If heparin therapy is to be successful, two points are Considered to be of the utmost importance One is the necessity of establishing a very early diagnosis of the condition, if possible, at a time when the process is still confined to the lower part of the leg Suitable measures to obtain this end are discussed in detail The other point is the necessity to make the patient ambulant before heparinization is discontinued Many failures with heparin treatment can be ascribed to neglect of this procedure

Evaluation of "coronary vasodilators" by coronary arteriography.

Abstract: The primary purpose of a coronary vasodilator is to increase the caliber of the coronary vascular bed. Selective coronary arteriography currently is the most direct and effective means of evaluating changes in the size of the coronary arteries in the intact organism. Utilizing this method of examination, it is apparent that glyceryl trinitrate and erythrityl tetranitrate have coronary vasodilating actions even in those patients with overt and serious coronary atherosclerosis. The demonstration of this action, however, does not imply that coronary blood flow is consequently improved.

A distinctive electrocardiogram in muscular subaortic stenosis due to ventricular septal hypertrophy.

Abstract: Unusual electrocardiographic findings in 6 cases of muscular subaortic stenosis, i.e., abnormal Q waves in the left precordial leads and in limb leads I, II, III, aVL and aVF and tall R waves in the right precordial leads and lead aVR, have been described. In the absence of any cause for, or evidence of, myocardial infarction or right ventricular hypertrophy and in the presence of surgically or postmortem-proved enlargement of the ventricular septum, these abnormalities have been attributed to ventricular septal hypertrophy. Serial electrocardiograms in 3 cases revealed a regression of the signs of septal hypertrophy and the progressive development of the signs of hypertrophy of the free wall of the left ventricle, which eventually dominated the electrocardiogram, even though at autopsy the septal hypertrophy exceeded the free wall hypertrophy. This hypertrophy of the free wall of the left ventricle was believed to have occurred principally as the result of the obstruction to left ventricular outflow caused by the enlarged septum. An electrocardiogram suggesting ventricular septal hypertrophy may be helpful in the diagnosis of muscular subaortic stenosis.

Prognostic value of the cold pressor test and the basal blood pressure. based on an eighteen-year follow-up study.

Abstract: The cold pressor test has been evaluated in a prospective study of young normal individuals followed-up over an 18-year period. The blood pressure response to cold stress did not have a significant relationship to the incidence of hypertension, the subsequent blood pressure, or the increment of blood pressure rise over the 18-year period. An important relation was found, however, between the basal blood pressures recorded and the test and blood pressures recorded later. These data are discussed and interpreted as showing the relative importance of the basal state of the vascular system as opposed to the nervous control which causes transient rises in blood pressure.

The t wave and ventricular repolarization.

Abstract: A detailed analysis of the genesis of the T wave comparable to that provided for a QRS complex cannot be obtained by means of direct recording of ventricular repolarization. This is mainly because of the low voltage, the slow time-course and the absence of a uniform conduction during repolarization. Determination of the excitability cycle provides an indirect measurement of local repolarization. An analysis of the recovery of excitability at several intramural and epicardial electrodes demonstrates that the T wave of the canine heart, as recorded from the epicardial surface, is determined in a larger degree by local differences in the progress of repolarization than by the intramural sequence of recovery. The preliminary results of a new experimental method, providing immediate and synchronous activation of the ventricles in an intact dog, demonstrate an over-all direction of repolarization from the apex to the base of the heart; they support Wilson's theory of the ventricular gradient.

Cardiovascular findings in patients with sickle cell anemia.

Abstract: T HIS study was undertaken to reveal the following aspects in patients with sickle cell anemia with or without clinical manifestation of heart disease: (1) the incidence of electrocardiographic abnormalities; (2) radiological evaluation of the chest for cardiomegaly and pulmonary vascular markings ; (3) auscultatory and phonocardiographic findings; and (4) autopsies from reports of 9 patients and the cause of death in 7 patients without autopsy.

Sustained, paired electrical stimuli: slowing of the ventricular rate and augmentation of contractile force.

Abstract: When the ventricle is electrically stimulated immediately after the termination of the absolute refractory period, a propagated depolarization occurs which does not result in a clearly defined secondary rise in intraventricular pressure. In 19 dogs, two fundamental consequences of such paired electrical stimuli were studied. Since the second depolarization is followed by a second refractory period, the time during which the ventricle is unresponsive to other electrical stimuli is effectively doubled. Rapid ventricular rates could thus be slowed by paired stimuli, regardless of the mechanism of tachycardia. In each of 16 dogs, spontaneously occurring sinus tachycardia was suppressed by paired electrical stimulation. In 8 animals, ventricular tachycardia was induced by digitalis intoxication and in 6 by means of exogenous stimulation with a separate electrical pacemaker; paired stimuli slowed the ventricular rate in every animal by an average of 57 beats per min. Striking augmentation of the ventricle's contractile response was found to be a second consequence of paired stimulation. This phenomenon was demonstrated in 8 dogs in which right ventricular contractile force was measured with a strain gauge arch. Paired electrical stimuli increased ventricular contractile force to an average of 275 per cent of the levels observed with single impulses delivered at the same rate. Preliminary studies in man indicate that slowing and augmentation of contractile force also occur when the human heart is stimulated in a similar manner. Appropriately timed, paired electrical stimuli to the ventricles result in profound alterations in both the electrical and contractile properties of the mammalian heart. It is possible that this technic will be applicable and beneficial in certain patients, when a slower heart rate and/or augmented myocardial contractile force is desirable.

Effect of alterations in ventricular rate on cardiac output in complete heart block.

Abstract: Evidence is presented, both from a review of the literature and from original observations in this laboratory during cardiac catheterization in man, to demonstrate that the cardiac output in the majority of patients with complete heart block can be increased with increments in ventricular rate. These data, especially when considered in conjunction with the demonstrated importance of synchronous as opposed to asynchronous atrioventricular contraction, strongly suggest that synchronous P-wave pacemakers, such as the one developed by our group, are physiologically and clinically superior to idioventricular pacemakers of either the fixed or variable rate types.