Pressure-flow studies in man during atrial fibrillation.

In 13 patients who had atrial fibrillation the ascending aortic pressure-flow relationships were measured by the pressure gradient technique. Both the pressure and flow curves were similar in contour to ones previously obtained by this method. From these recordings, relationships between the phases of systole, the ventricular filling time, and various derived parameters of pressure and flow such as the pulse pressure, stroke volume, peak flow, stroke work, and peak power were evaluated. For stroke volumes greater than 15 cm(3) there was little change in the duration of systole in an individual patient. In each patient both the preejection period and the duration of ejection showed a good correlation with stroke volume, peak flow, stroke work, and peak power. When data from all patients were examined, the relationship between stroke volume and duration of ejection was found to be curvilinear and had an overall correlation of r=0.91. There was marked variation from patient to patient in duration of both the preejection period and systole. Similar correlations between the phases of systole were noted with peak flow, peak power, and stroke work. A positive but mediocre correlation was found between the previous RR interval (an index of ventricular filling time) and the subsequent stroke volume. The correlation, in six patients, between two previous RR intervals and stroke volume was considerably better. The relationship between the pulse pressure and stroke volume was reasonably close except in one patient; however, the group correlation was poor due to differences between individuals.

Hemodynamic findings in 123 patients with acute myocardial infarction on admission.

Hemodynamic and clinical evaluations of 123 patients with acute myocardial infarction were performed during the first hour of admission to the hospital. In the 123 patients, the right atrial pressure was less than 10 mm Hg in 49 patients, the right atrial oxygen saturation was less than 70% in 97 patients, the arteriovenous oxygen difference was greater than 5.0 vol% in 78 patients. The arterial Po2 was less than 90 mm Hg in 101 of 107 patients who could be evaluated while breathing room air. The cardiac index was depressed below 3.0 L/min/m2 in 65 of 98 patients. The hemodynamic findings generally correlated with the clinical status of the patient; however, within each clinical class of patients there was a wide spectrum of values for each measurement evaluated. There was also considerable overlap of the values found within each clinical classification. It is concluded that hemodynamic evaluation of patients with acute myocardial infarction presents a profile of the patient which is frequently different from the profile that clinical evaluation presents. An objective hemodynamic classification of patients with acute myocardial infarction may provide a more useful index for the evaluation of the patient's prognosis and for the assessment of preventative therapy.

Localization of septal pacing sites in the dog heart by epicardial mapping.

To examine whether different septal pacing sites could be distinguished by their epicardial activation patterns, six to eight stimulating electrodes were placed throughout the septum in seven open chest dogs. Unipolar electrograms were obtained from 52 epicardial electrodes during pacing from each stimulating electrode and isochronous epicardial maps were constructed. The location of each stimulating electrode was found by dissection, and its distance from the overlying epicardium was measured. To allow comparison among epicardial maps, the septum was conceptually subdivided into nine regions to which stimulating electrodes were assigned. Epicardial activation patterns from the same region were similar and these patterns allowed the region containing a stimulating electrode to be identified in many cases. Three other variables were found to have additional localizing value. There were: 1) the time from the stimulus to epicardial breakthrough, 2) the duration of epicardial activation, and 3) the area of epicardium activated in the first 5 ms after epicardial breakthrough. For those stimulating electrodes that could not be localized by their epicardial activation patterns, the distance of the stimulating electrode beneath the epicardium was well fit from these three variables by multiple regression (correlation coefficient [r] = 0.97). Thus, using all the previous factors, localization of septal pacing sites was possible in the noninfarcted dog heart by epicardial mapping.

Effect of daily charge feedback on inpatient charges and physician knowledge and behavior.

Concurrent charge feedback has gained widespread acceptance as a method of minimizing hospitals' losses under the Medicare prospective payment system despite the fact that its effect on patient outcomes, physician behavior, or charges has not been studied in depth. In a controlled trial on two medical wards in an academic medical center, the effect of daily charge feedback on charges was studied. Sixty-eight house staff and 16 teaching attending physicians participated during a 35-week period, taking care of 1057 eligible patients. No significant differences in charges were seen when all patients were included. Since 45% of patients had planned protocol admissions (diagnostic workups or protocol treatment) on which the house staff had little change to impact, a subgroup analysis was performed, excluding these patients. In the remaining patients, a highly significant reduction in mean total charges (17%), length of stay (18%), room charges (18%), and diagnostic testing (20%) was found. In-hospital mortality and preventable readmission within 30 days were similar on the two wards. It was concluded that charge feedback alone is effective in a teaching hospital for decreasing charges.

A new information system for medical practice.

A data bank containing our clinical experience with more than 3,000 patients with suspected and documented ischemic heart disease is being used to expand our ability to care for patients. This report describes how the experience is documented, stored, and retrieved so that it can be used in patient management. Data acquisition is integrated with patient care by means of forms that are part of the patient record. Follow-up information is obtained at six months, one year, and yearly thereafter. All data are stored in a computer information system that allows the doctor to recall the experience of patients like his new patient. Prognostic information is available on each new patient both on-line and in the form of a printed laboratory report. The data bank represents an initial chapter of a computer textbook of medicine.

Cholesterol metabolism in non-obese women--Failure of physical conditioning to alter levels of high density lipoprotein cholesterol.

The effects of a 6-week program of vigorous exercise were studied in 14 non-obese females aged 22--26. Preceding and following a regimen consisting of 30--45 min of jogging 5 days per week, treadmill performance, body weight, total plasma cholesterol, and plasma high density lipoprotein (HDL) cholesterol were assessed. Aerobic performance improved markedly after training as demonstrated by a reduced heart rate at each submaximal treadmill workload, and by an increase in maximal attainable workload. In the absence of a significant change in body weight, total cholesterol fell significantly after training (171 +/- 6 vs 161 +/- 5 mg/dl, P less than 0.05) whereas HDL cholesterol was not significantly altered (63 +/- 5 vs 58 +/- 3 mg/dl). The ratio of total cholesterol to HDL cholesterol fell insignificantly (2.92 +/- 0.19 vs 2.86 +/- 0.14). Our findings differ from prior reports of elevations of high density lipoprotein levels following physical conditioning in men. We suggest that hormonal or other factors leading to higher baseline levels of HDL in women counteract the expected alterations in lipoprotein metabolism induced by physical training.

Clinical relevance of exercise-induced S-T segment elevation.

Patients with exercise-induced S-T elevation or S-T depression were evaluated with demographic, treadmill and angiographic data. When 541 patients with S-T depression were compared with 109 patients with S-T elevation, a greater proportion of the former had chest pain (71 versus 58 percent) and a normal-sized ventricle (86 versus 61 percent) with normal wall motion (54 versus 30 percent). A greater proportion of patients with S-T elevation had had a previous myocardial infarction (61 versus 33 percent). Among patients without prior infarction (360 with S-T depression and 42 with S-T elevation), these differences disappeared. In this group of 42 patients with S-T elevation, 83 percent had a normal-sized ventricle, 64 percent had normal contractility and none had a ventricular aneurysm; the severity of coronary disease and ventricular dysfunction did not differ from the severity in patients with S-T depression. Thus, in patients without prior myocardial infarction, the cause of the development of S-T elevation or S-T depression during exercise does not appear to be related to the severity of the coronary lesions, ventricular function or wall abnormalities at rest. In patients with prior myocardial infarction, exercise-induced S-T elevation appears to be a marker of depressed left ventricular function.

Chronotropic effect of acetylstrophanthidin infusion into the canine sinus nodal artery.

Studies were performed to determine the chronotropic effect of acetylstrophanthidin during constant infusion through cannulation of the sinus nodal artery. Ten mongrel dogs weighing 13.5 to 18 kg were studied under sodium thiamylal anesthesia. Epicardial atrial and ventricular electrograms were recorded. The sinus nodal artery was cannulated and infused for 20 minutes at a rate of 2 cc/min with a solution containing acetylstrophanthidin, 0.5 microng/cc. Mean results for the group of 10 animals were determined. There was a gradual acceleration of the atrial rate of 45 beats/min after 6 to 8 minutes of infusion. The peak atrial rate of 175 beats/min was achieved by 10 to 12 minutes. This tachycardia persisted for 2 to 4 minutes without atrioventricular block or premature beats. By 12 to 14 minutes, there was a gradual slowing of atrial rate followed by bradycardia, sinus pauses and atrial arrest. Sinus nodal arterial infusion of acetylstrophanthidin produces an initial positive chronotropic effect and, if maintained, a depression of atrial rate and, terminally, atrial arrest. The gradual time course of development and decline of the tachycardia suggests that the "paroxysmal" atrial tachycardia caused by digitalis excess is the result of enhanced pacemaker automatically rather than reentry, and thus is not truly paroxysmal.

Exercise responses before and after physical conditioning in patients with severely depressed left ventricular function.

The ability of patients with severely impaired left ventricle function to perform short-term exercise and to participate in a cardiac rehabilitation program and attain physical training effects was evaluated. Treadmill exercise tests were performed before and after physical conditioning in 10 patients with a prior myocardial infarction and a left ventricular ejection fraction at rest of less than 27 percent (range 13 to 26) determined by radionuclide angiography. All patients participated in a supervised exercise program with a follow-up period of 4 to 37 (mean 12.7) months. Baseline exercise capacity showed marked variability, ranging from 4.5 to 9.4 (mean 7.0 +/- 1.9) METS, and improved to 5.5 to 14 (mean 8.5 +/- 2.9) METS after conditioning (p = 0.05). The oxygen pulse (maximal oxygen uptake/maximal heart rate) before and after conditioning was used to assess a training effect and increased significantly from 12.8 +/- 2.0 to 15.7 +/- 3.2 ml/beta (p less than 0.01). There was no exercise-related morbidity or mortality, although two patients died during the study period. It is concluded that selected patients with severely imparied left ventricular function can safely participate in a conditioning program and achieve cardiovascular training effects.

Atrial fibrillation in the preexcitation syndrome.

One hundred patients with proved accessory pathways of the Kent bundle type were studied with multiple intracardiac catheters. During the procedure 16 had atrial fibrillation. Two patterns of induction of atrial fibrillation were noted. In most patients an earlier than expected atrial deflection appeared in one of the atrial recordings and was followed by atrial flutter (cycle length less than 220 msec) or atrial fibrillation either immediately or after a brief period of acceleration of atrial rate. In a few patients, intraatrial conduction delay, manifested as 2:1 block or Wenckebach block from the right to the left atrium or vice versa, occurred before the onset of atrial fibrillation. The incidence of atrial fibrillation was not statistically related to any associated cardiac abnormalities. A significantly large incidence of ventricular fibrillation was recorded in patients who had documented atrial fibrillation either before admission or during the catheter study.

Career choices of 135 cardiology trainees at Duke University Medical Center from 1970 to 1984.

Alarm has been expressed at recently presented evidence showing that diminishing numbers of physicians are entering academic careers. The experience of the cardiology training program at a university medical center between 1970 and 1984 was reviewed to determine the career paths chosen by its trainees. During the study period, 135 physicians received training. Between 1970 and 1978 the percentage of trainees making academic medicine their initial career choice fluctuated considerably. Beginning in 1978, the percentage entering academic medicine steadily increased; in the most recent class, 8 of 9 trainees accepted academic faculty positions. Among 72 former trainees who joined an academic faculty after finishing training, approximately 7% per year left academic medicine for clinical practice. The median length of an academic career was 10 years. Individual institutions may be able to reverse the national trend of trainees making clinical practice their initial career choice. However, physicians who leave academic medicine for clinical practice may continue to deplete faculty ranks.

Sinus nodal function in the intact dog heart evaluated by premature atrial stimulation and atrial pacing.

Sinus nodal function was analyzed in 25 dogs by premature stimulation of the right atrium. The return (AT-AR) and post-return (AR-A) cycles were plotted as a function of the premature cycle, and four zones were identified. Zone I (compensatory zone) was observed during the last 4.8 percent (mean value) of the sinus cycle (A-A). Zone II was observed during 43.6 to 95.2 percent (mean value) of the sinus cycle. During the latter part of zone II, AT-AR was nearly constant and AR-A remained nearly equal to A-A during the last 29 percent (mean value) of the cycle. Earlier in zone II three distinct patterns of return cycle responses were observed whereas post-return cycles either remained nearly equal to A-A or showed progressive lengthening. Zone III (interpolation) was observed in 10 animals during 39.5 to 46.2 percent (mean value) of the sinus cycle. AR-A was nearly equal to A-A in zone III. Interpolation was incomplete late and complete early in the zone. Zone IV (echo zone) was seen in another 10 animals during 40.9 to 45.3 percent (mean value) of the sinus cycle and in this zone AR-A was greater than A-A. No significant difference in these zones was seen among the animals anesthetized with pentobarbital or alpha-chloralose, or given 6-OH-dopamine. The AR-A was important in the analysis of these zones and appears to be essential to the interpretation of data derived from premature atrial stimulation. Responses to premature atrial stimulation through a catheter electrode positioned against the sinus nodal region compared favorably with responses to direct epicardial stimulation. After periods of continuous right atrial pacing a vairety of patterns of sinus nodal depression were observed at different rates and durations of stimulation. The frequent occurrence of a short sinus escape cycle followed by the maximal pause observed during rapid pacing rates suggests sinus nodal entrance block. This may be an important factor to consider in determining an optimal pacing rate for assessing sinus nodal function.

Ventricular aneurysm with ventricular tachycardia. Report of a case with epicardial mapping and successful resection.

A case of ventricular aneurysm with refractory ventricular tachycardia is presented. Epicardial mapping was used to localize the site of earliest epicardial activity to the margin of the aneurysm, and subsequent resection of this area abolished the rhythm disturbance.

Surgical treatment of tachyarrhythmias in patients with both an Ebstein anomaly and a Kent bundle.

The report relates experience with six patients with Kent bundles, five of whom had the Wolff-Parkinson-White syndrome, operated upon for tachyarrhythmias caused by the presence of the pathway. It was successfully divided in four patients, its antegrade conduction capacity interrupted in one, and a failure occurred in the sixth patient. In the three patients who had a Kent bundle with a short effective refractory period for antegrade conduction, the life-endangering potential of the Kent pathway was corrected. To emphasize the complexities of the tachyarrhythmias in Ebstein's anomaly, two patients have mild but controllable postoperative supraventricular tachyarrhythmias (SVT) due to a Mahaim pathway. The surgical problems encountered in these patients are reviewed.

The surgical treatment of Wolff-Parkinson-White Syndrome: evolution of improved methods for identification and interruption of the Kent Bundle.

Fifty patients have been operated upon for the tachyarrhythmias associated with Kent bundles. The indications for operation were supraventricular tachycardia (SVT) in 23 and life-threatening tachyarrhythmia in 27. Among the unusual variants noted were multiple Kent bundles that conducted only retrograde in 3. Forty-nine patients underwent attempted interruption of the bundle of Kent followed by His bundle division in 6. One had elective division of the bundle of His. The surgical problems occurred in 13 patients with posterior septal Kent bundles. A new approach is outlined for this group. Division of the Kent bundle was successful in 31 patients, but 2 deaths occurred from cardiomyopathy. Seven patients had successful control of SVT by His bundle interruption. One patient with postoperative retrograde conduction has the SVT controlled with drugs. Eight have postoperative delta waves, but their SVT is controlled with drugs. There were 3 failures.

Educating tomorrow's doctors: the thing that really matters is that we care.

The unique purpose of medical schools is to select and educate competent, caring physicians capable of meeting society's expectations for health care. The author discusses this purpose first in the context of liberal education, which provides a broad perspective essential in the education of doctors and other professionals. Such an education can be achieved partly by how medical students are selected and by effectively uniting it with professional learning. The most important goal of liberal education is to promote intellectual wholeness as a lifelong pursuit of physicians. Second, the author reviews medical curricula, which have been slowly evolving away from a focus on providing instruction and toward one of producing learning. This new approach is a more rational one, and can be seen in some schools' reductions of lectures and increases in team teaching and problem-based learning, and earlier exposure of students to patients, especially in ambulatory care settings. An important role of medical educators is to provide enough free time for students to learn, and to pay attention to the "informal curriculum," where the unwritten ethical codes of medicine are revealed. The author then turns to issues of professionalism, especially that elusive part that goes beyond expertise. He emphasizes that the training of tomorrow's doctors is ultimately a public goal, and that medical schools must help restore public trust in doctors by selecting and nurturing professionals who see medicine in a broad social context. He reiterates that a liberally educated doctor is most likely to have such an outlook, and concludes by urging medical educators to remember that there is no substitute for a doctor's competence, caring, and professionalism expressed in the context of a liberally educated mind. And that the most important thing that educators can do as they bend to their task is to care.

Institutional change: embracing the initiative to train more generalists.

Dartmouth Medical School was one of 16 U.S. medical schools that received a Generalist Physician Initiative (GPI) grant from The Robert Wood Johnson Foundation in 1994. This article describes institutional change at the school, noting that while the context in which the GPI was launched was receptive, the grant enabled Dartmouth to accelerate institutional changes already under way. Perhaps even more important is that Dartmouth used an approach to change that worked, and although the specific actions may not generalize to other schools, the authors hope the principles will. Key among these principles were capitalizing on a sense of urgency for change, creating and empowering a guiding coalition, developing and communicating the vision, generating short-term wins, consolidating gains, and anchoring new approaches to the existing institutional culture. Changes at Dartmouth are described in the areas of admission and recruitment, undergraduate and graduate medical education, and supporting community practice. The authors also describe shortcomings in developing the program, such as maintaining the guiding coalition in the face of the changing health care system and clinical pressures, developing a vision and strategy in areas managed by the state, and engagement of a broad-based group.

Fulfilling the social contract between medical schools and the public.

To gain a better understanding of the effects of medical schools related to transformations in medical practice, science, and public expectations, the Association of American Medical Colleges (AAMC) established the Advisory Panel on the Mission and Organization of Medical Schools (APMOMS) in 1994. Recognizing the privileges academic medicine enjoys as well as the power of and the strain on its special relationship with the American public, APMOMS formed the Working Group on Fulfilling the Social Contract. That group focused on the question: What are the roles and responsibilities involved in the social contract between medical schools and various interested communities and constituencies? This article reports the working group's findings. The group describes the historical and philosophical reasons supporting the concept of a social contract and asserts that medical schools have individual and collective social contracts with various subsets of the public, referred to as "stakeholders." Obligations derive implicitly from the generous public funding and other benefits medical school receive. Schools' primary obligation is to improve the nation's health. This obligation is carried out most directly by educating the next generation of physicians and biomedical scientists in a manner that instills appropriate professional attitudes, values, and skills. Group members identified 27 core stakeholders (e.g., government, patients, local residents, etc.) and outlined the expectations those stakeholders have of medical schools and the expectations medical schools have of those stakeholders. The group conducted a survey to test how leaders at medical schools responded to the notion of a social contract, to gather data on school leaders' perceptions of what groups they considered their schools' most important stakeholders, and to determine how likely it was that the schools' and the stakeholders expectations of each other were being met. Responses from 69 deans suggested that the survey provoked thinking about the broad issue of the social contract and stakeholders. Leaders on the same campuses disagreed about what groups were the most important stakeholders. Similarly, the responses revealed a lack of national consensus about the most important stakeholders, although certain groups were consistently included in the responses. The group concludes that medical school leaders should examine their assumptions and perspectives about their institutions' stakeholders and consider the interests of the stakeholders in activities such as strategic planning, policymaking, and program development.

Tapping the power of information: an orientation for academic medical centers.

In September 1994 the Association of American Medical Colleges' (AAMC's) Advisory Panel on the Mission and Organization of Medical Schools (APMOMS) established a working group to address both the long-term and the immediate implications of the expanding capacity of and need for information technology (IT) within academic medical centers (i.e., medical schools and teaching hospitals). Over a two-year period, group members assessed the utilization of IT through surveys of current practices and interactions with acknowledge leaders in the field. They also had discussions with deans and other institutional leaders. The group developed the consensus that proper use of currently available IT is crucial to virtually every aspect of academic medicine's clinical, educational, and research missions. Moreover, current IT technology will be further enhanced by the powerful new applications that are nearing deployment. All group members agreed that IT must become a core competency of academic and medical centers (AMCs), the profession, and individual physicians and scientists to ensure the survival of AMCs in the current highly competitive environments. The authors outline their arguments for the development of strong information systems within AMCs and present basic characteristics of systems that show promise for successful implementation. The y review some of the major institutional obstacles that have hindered the planing and implementation of IT. They conclude with a list of practical institution strategies for success in planning and implementing IT systems, and suggestions for how the AAMC can help members achieve success in these activities.

Sustaining the development of primary care in academic medicine. Working Group on Sustaining the Development of Academic Primary Care. Association of American Medical Colleges.

This article is the report of the Working Group on Sustaining the Development of Academic Primary Care, one of the six subgroups of the Advisory Panel on the Mission and Organization of Medical Schools (APMOMS) sponsored by the Association of American Medical Colleges (AAMC). To begin, the group draws a distinction between primary care and generalism. Primary care is a core domain of health care and, in the context of emerging integrated systems, will increasingly be a multidisciplinary shared function. Non-subspecialized physicians, or "generalists," are a key element in the provision of primary care, but do not act alone. Core competencies for primary care are central to the education of all physicians. Therefore, irrespective of workforce goals for generalist physicians, primary care should have a strong, central position in the medical school so that graduates can receive a sound general medical education and can be prepared for any specialty and for lifelong learning in an evolving health care system. For primary care to achieve that position, medical schools must integrate primary care into their missions, strategic plans, operation, organization, academic administrative structures, curriculum development, faculty development (both school- and community-based), resource development, alliances with appropriate clinical services networks, financial policy, and evaluation and educational monitoring systems. The group briefly describes the elements of those changes and also proposes ways that the AAMC and medical school leaders could promote the central role of primary care in medical schools.