E. Grey Dimond

Contribution of atrial systole to the cardiac function at a fixed and at a variable ventricular rate

Abstract 1. 1. The contribution of atrial systole to cardiovascular dynamics was described in 21 patients with complete heart block at a fixed and at a variable ventricular rate. 2. 2. It was demonstrated that a properly timed atrial systole significantly improves cardiac function in patients with complete heart block. The optimal P-R interval was found to occur between 1 and 300 msec. For this range there were 13, 14, 6, 12, 14 and 33 per cent increases in ejection time, mechanical systole, isometric contraction time, systemic pressure, peak derivative of brachial artery pressure and tensiontime index, respectively, as compared with figures obtained when atrial systole occurred during ventricular systole. 3. 3. It was also found that the contribution of atrial systole to cardiac function occurs in all ranges of ventricular rates studied (20 to 125 beats/min.). However, the maximal beneficial effect of atrial systole was found to occur for the ventricular rate in the range of 51 to 80 beats/min. 4. 4. Very short or very long P-R intervals resulted in minor changes in the measured parameters, and the figures obtained closely approach the ones determined when atrial systole occurred during ventricular systole. 5. 5. It is, therefore, concluded that atrial systole significantly improves cardiac function in man under the conditions of our study.

Cardiovascular Dynamics in Complete Heart Block at Various Heart Rates Effect of Exercise at a Fixed Heart Rate

Thirteen patients with complete atrioventricular block resulting from coronary disease were studied. In seven the diagnosis of coronary disease was established by the presence of typical history and electrocardiographic and enzymatic findings compatible with an acute infarction. Of the remaining six cases, three had a typical history of angina pectoris. In three cases there was no history of myocardial infarction or angina pectoris, and the diagnosis of coronary disease was suspected by the appearance of heart block above age 60 in the absence of any other possible etiologic factor that might be responsible for the establishment of the block. Exercise studies were performed in eight cases. Right heart catheterization was performed under local anesthesia prior to implantation of a permanent cardiac pacemaker. A no.-6 bipolar electrode catheter * 1 was introduced into the antecubital vein and advanced to the apex of the right ventricle. Another no.-7 Lehman catheter was introduced into the cephalic vein and advanced to the right atrium and right ventricle. Cardiac output was determined by the indicator-dilution technic with indocyanine t (Cardio-

Effect of Heart Rate, Exercise, and Nitroglycerin on the Cardiac Dynamics in Complete Heart Block

THE PRESENCE of complete heart block offers a good opportunity to study cardiovascular functions, since one of the major variables of cardiac activity, i.e., heart rate, is maintained constant.113 In addition, if a cardiac pacemaker is implanted in a heart for treatment of complete heart block,14-20 total control of the cardiac rate is achieved, thereby providing an excellent opportunity for studying cardiovascular hemodvnamics under a variety of fixed rates. The present study was unidertaken (1) to attempt to establish the most appropriate heart rate for permanent pacing; (2) to ascertain the hemodynamic consequences of complete heart block at a fixed slow heart rate, and the effect of increasing heart rate; (3) to determine the effects of exercise and nitroglycerin on the cardiac dynamics at various fixed heart rates. A patient with complete heart block resulting from coronary artery disease was studied.

Clinical experience with the use of computers for calculation of cardiac output

Abstract 1. 1. One hundred and seventeen cardiac output determinations were obtained in 12 patients with normal and abnormal cardiovascular systems. The dye curves were calculated by the hand method of Hamilton and with the use of a dye-dilution analog computer. 2. 2. There was a good agreement between the two methods with an average of the percentage difference of 8 per cent and with a standard deviation of 4.2 per cent. In curves with prolonged clearance time and low peak concentration, the average difference was 25.2 per cent with a standard deviation of 11.0 per cent. 3. 3. Changes in the cardiac output provoked by exercise, change in heart rate and by administration of drugs were adequately detected by the computer technic. 4. 4. It was found that the cardiac output computer is a time-saving, reliable and reproducible instrument in the calculation of the cardiac output. 5. 5. The computer should not be used in cases with low peak concentration, prolonged clearance time and in cases with any form of intracardiac shunt.

The carotid tracing and apexcardiogram in subaortic stenosis and idiopathic myocardial hypertrophy

I N a PREVIOUS paper’ we reported abnormalities of the indirect carotid tracing in patients with aortic valvular stenosis, and we confirmed some of the findings previously described in the literature.2-12 The described findings, consistently present in all patients with this valvular lesion, consisted of prolonged total ejection time and upstroke time, carotid shudder, low anacrotic notch and an inconspicuous dicrotic notch. At that time we also indicated that 2 of our cases with subaortic stenosis presented distinct characteristics in the carotid tracing which were quite different from those in the cases with the valvular type of aortic obstruction. The purpose of this present report is to analyze in more detail the abnormalities of the carotid tracings in patients with subaortic stenosis and in cases of idiopathic myocardial hypertrophy.

Precordial Vibrations Clinical Clues from Palpation

The low-frequency precordial vibrations originating at the point of the apex beat, and especially those in the subaudible range, seem to offer considerable clinical usefulness. In this paper I have briefly outlined some of the physiologic, pathologic, and pharmacologic evidence to support this impression. The instrumentation we have used is crude and undoubtedly we have been misled on occasion by artifacts. However, there is sufficient validity in the technic, reproducibility of result, and correlation with intracardiac events to warrant intensive study.

Rapidly repeated determinations of the cardiac output with the indicator-dilution technic

T HE indicator-dilution technic has been extensively used in the study of the circulation under a variety of conditions.1-10 Although it has been in use for a relatively long time, only a few have attempted to employ it in man for rapidly repeated determinations of cardiac output.“-I4 In these previous reports the time intervals between injections were kept above 5 minutes. Determination of cardiac output by the Fick principle does not allow sequential observations at short time intervals. However, moment-to-moment changes may occur, as, for example, in response to short periods of exercise, during administration of short-acting cardiac drugs or during various states such as experimental shock and acute hypervolemia. In these instances rapidly repeated serial determinations of cardiac output in man or in intact experimental animals are highly desirable. The present study was undertaken (a) to verify the random, systematic variability of rapidly repeated determinations of the cardiac output in man by the dye-dilution technic, and (b) to determine its possible usefulness in studying circulatory changes over a short period of time during a variety of conditions.

Apex cardiogram in the diagnosis of congenital heart disease

Abstract 1. 1. Our experience with the use of the apex cardiogram in the diagnosis of congenital heart disease is reviewed. 2. 2. Correlation of the apex cardiogram with intracardiac pressures in several congenital heart diseases showed that the apex cardiogram reflects with accuracy the hemodynamic status of the cardiovascular system. 3. 3. In general, patients with left to right shunt due to atrial septal defect and ventricular septal defect showed an abnormal right ventricular apex cardiogram characterized by an exaggeration of the rapid filling wave and by changes in the systolic wave. 4. 4. Conditions associated with pressure loading such as pulmonary stenosis or pulmonary hypertension are associated with a large a wave with a sustained systolic wave. 5. 5. Cases of subaortic stenosis showed abnormalities in the apex cardiogram which permitted separation from those of valvular stenosis. 6. 6. It was also shown that the degree of pulmonary hypertension in patients with left to right shunt is reflected in the apex cardiogram, thus providing a useful guide as to the hemodynamic state of a given congenital lesion.

Prevention of cholesterol-induced hypercholesterolemia and atherosclerosis in rabbits by an active peroxidase subunit from hepatocatalase

Summary Hepatocatalase peroxidase (HCP), an active peroxidase-oxidase subunit isolated from beef liver catalase, prevented cholesterol-induced hypercholesterolemia and atherosclerosis in rabbits with no apparent toxicity or undesirable side-effects. No allergic or immunological reactions were observed throughout a 15-week period of daily treatment with parenteral HCP.

Newer concepts of digitalis

Abstract Recent experiments, both elaborate and simple, performed in normal subjects and in cardiac patients with normal sized hearts emphasize the primary myocardial action of digitalis in increasing contractile tension, some effect being noted even after small doses. The drug is an important part of management of patients undergoing intracardiac surgery and in treatment of selected patients with heart block following pacemaker control of their ventricular rate. Digoxin and digitoxin are metabolized and excreted differently. Digoxin is more completely absorbed from the gastrointestinal tract than previously thought and the route of administration makes little difference on blood levels after one to two hours. There are some new notions on drug therapy for digitalis overuse.