Samuel M. Fox

Effects of Dopamine in Man

Dopamine, the biochemical precursor of norepinephrine, was infused intravenously into 11 normal subjects and 2 patients. Results of hemodynamic studies in 6 normal subjects indicated that dopamine increased cardiac output and stroke volume in all subjects. Arterial pressure also increased in all subjects with a predominant systolic pressure increment. Calculated vascular resistance decreased in 5 subjects and did not change in the other subject. Changes in heart rate were of small magnitude and were inconstant in direction. Left atrial pressure did not change in 2 patients at a time when substantial increments in cardiac output were produced by dopamine. Comparison of the doses of dopamine and norepinephrine calculated to produce equivalent increments in systolic pressure indicated that dopamine was 1/25 to 1/56 as potent as norepinephrine in this respect. Infusions of dopamine produced relatively small but consistent increments in blood glucose levels. It is concluded that the pharmacological actions of dopamine in man are different from those of epinephrine and norepinephrine. Because of its distinctive properties, dopamine may be useful in the treatment of patients with inadequate cardiac output.

The exercise electrocardiogram: Differences in interpretation: Report of a technical group on exercise electrocardiography

Abstract Exercise electrocardiography is a valuable clinical tool with which quantitative evaluations and comparisons are now being attempted in many fields of cardiovascular investigation. Among a series of studies by a technical group on exercise electrocardiography, an assessment was made of observer variation in the clinical interpretation of ST-T responses during and after exercise. Interobserver variation among 14 cardiologists was great; individually assigned frequencies of abnormal responses after exercise in a mixed sample of records ranged from 5 to 58 per cent. Disagreement was greater for the diagnosis made during than for that made after exercise. Introbserver variation was also so great that use of the same observer for all exercise electrocardiographic readings would not necessarily provide acceptable reliability. The chief factors in disagreement were the lack of defined criteria for interpretation, in particular uncertainty about the significance of J-point ST-T depression, and technical quality of the records. Observer agreement was substantially increased when records were coded by unambiguous criteria or when simple measurements were made of the ST-T response after exercise.

Mahaim and James fibers as a basis for a unique variety of ventricular preexcitation

This report concerns pathologic findings in a 54 year old woman with intermittent preexcitation who died of carcinoma of the breast. Electrocardiograms revealed predominantly normal sinus rhythm with a normal P-R interval and narrow QRS complex. Episodes of sinus rhythm, short P-R interval and QRS widening (with delta wave) were also recorded. During preexcitation QS complexes were noted in leads II, III, aVF, V1 and V4 to V6. Delta waves were negative in leads II, III, aVF and V1 isoelectric in leads V4 to V6 and positive only in leads I, aVL, V2 and V3. This case thus defies classification into any known variety of preexcitation. Complete serial sections, cut through the entire conduction system and both atrioventricular (A-V) rims, totaled 18,600 sections. These revealed no bundle of Kent. Instead, Mahaim fibers histologically identified as His bundle tissue gave off from the A-V bundle to both the right and the left sides of the septum associated with the normal fibers of James. This case reveals that (1) fibers of James can bypass the A-V node, (2) fibers of Mahaim can conduct, and (3) there are types of preexcitation in addition to types A and B.

The technique of estimating the instantaneous aortic blood velocity in man from the pressure gradient.

mhe time relationships between pres1 sure and blood velocity in the asdending aorta can be used to define the mechanical function of the heart. To the extent that the mechanical function is altered early in disease, evaluation of these pressure-velocity relationships has important clinical as well as biophysical implications. It is possible to estimate both the aortic pressure and the instantaneous blood velocity by the use of a catheter method.’ This method requires accurate measurement of the instantaneous lateral pressures at two relatively close points along the axis of the aorta. The difference between these pressures is an approximate measure of the instantaneous pressure gradient from which the blood velocity may be computed by means of simple analog computer methods. The computation of the aortic blood velocity from the spatial pressure gradient requires extremely accurate measurement of the pressure and meticulous attention to a number of experimental details. A number of problems are raised by these requirements in the application of this technique to studies in human subjects. It is the purpose of this report to present certain approaches to many of these problems and to make available the details necessary to apply this method successfully in the clinical physiology laboratory. Examples are also given which illustrate the pressure-velocity relationships as measured in patients with nonvalvular myocardial disease and after the administration of certain pharmacologic agents. The discussion of the application of the computed pressure gradient technique may be divided into five general areas: catheter, gauges, electrical circuits and amplifiers, calibration, and evaluation of the total system response. Catheter. The catheter, as diagrammatically illustrated in Fig. 1, is of a special double-lumen design,? with two lateral pressure taps at the end of each lumen. The entry to each lumen is separated by a distance of 5 cm. The No. 69; French catheter will pass through a short beveled modification of a No. 12 gauge Robb needle. The stopcocks connecting the catheter to the gauges must be made to fine tolerance.1

Mumps of the Heart: Clinical and Pathologic Features

The clinical and pathologic findings of a patient who died from diffuse myocardial disease 8 months after an attack of mumps is presented. His illness was complicated by myocarditis, meningoencephalitis, pancreatitis, and orchitis. A study of past reports discloses that electrocardiographic evidence of myocardial involvement in mumps is common, that clinical evidence of myocardial involvement is unusual, and that death from myocardial involvement is extremely rare.

Task force II: Determination of occupational working capacity in patients with ischemic heart disease

The physical, metabolic and cardiovascular demands of occupations in industrialized countries have substantially declined during the past century. Many jobs that once required substantial physical effort are now performed by machines, robots or computers. This decrease in job-related energy demand is especially apparent in occupations performed by people over age 40, who, given some seniority, rarely perform physical tasks exceeding a peak energy expenditure of 5 kcaVmin or 3.5 METS, where 1 MET = energy expenditure sitting at rest (I). Nonetheless, the physical stress of employment is still the greatest challenge to the cardiovascular system of many patients with ischemic heart disease. For many sedentary jobs posing limited psychological or environmental demands, the adequacy of the patient’s physical working capacity can be assessed by a medical history, physical examination and symptom-limited exercise testing. However, as the physical demands of the job tasks increase to include exercise of widely varying intensities and types, or substantial psychological or environmental stress, assessment of physical working capacity becomes more complex. In patients with ischemic heart disease, the focus of occupational work evaluation is to determine whether or not the increase in cardiac demands produced by physical, psychological and environmental stressors will exceed the threshold for a “safe working capacity.” The challenge to the physician is to obtain an accurate, valid and reliable determination of this capacity.

Evaluation of the pressure time derivative method for estimating peak blood flow

Abstract The peak flow estimated by the pressure time derivative method was compared to the peak flow estimated by a Kolin electromagnetic flowmeter (EMF) in the descending thoracic aorta of 10 dogs. Under the conditions of this experiment, correlation of peak flow measured by the EMF with that obtained by the pressure time derivative method was good. This method should prove useful in the estimation of changes in peak blood flow. At present, the pressure time derivative method is not self-calibrating, so that indirect calibrating methods, such as an indicator-dilution technique, must be used to obtain quantitative results.

Mobile Coronary Services

I NTEREST has been increasing in the development of mobile coronary services (MCSs ).1-3 The stimulus for such concern is the coming realization that the striking mortality and morbidity secondary to coronary artery disease might be reduced if patients could come under medical care earlier in the course of the acute illness. It is estimated that in the United States 250,000 persons die annually of this cause outside of hospitals, which is more than half of the 400,000 deaths attributed to acute coronary heart disease. Furthermore, Pell and d7Alonzo4 have drawn attention to a diurnal variation in the mortality from coronary artery disease, with the least mortality occurring at a time and place where help was easily accessible. The initial course of events of a coronary episode is diagrammed in figure 1, from the onset of symptoms to the initiation of adequate care. The time between any two points is quite variable, and it is presently unknown which segment of the time line needs the most effort in shortening. MCSs are proposed to shorten the portion between T2 and T3 by delivering the proper equipment and personnel to the patient as soon as possible after the call for aid is initiated. Assuming that the successful application of this principle results in a significantly shortened T2