Comparison of the arrhythmogenic effect of myocardial infarction in the cat and dog.

Myocardial infarction was produced in dogs and cats by occlusion of the left anterior descending coronary artery. Arrhythmia was present in dogs but not in cats 6 to 48 h after occlusion. The absence of arrhythmia in cats was not due to persistent myocardial depressant effects of anaesthesia administered during surgery. Studies in cats with surgically-induced heart block revealed multiple ventricular pacemakers but no change in average ventricular rate following coronary occlusion. These results suggest that sinus overdrive, although not elevated compared with the dog, is sufficient to suppress arrhythmia in the cat. Further, since small dogs developed significantly less arrhythmia than large dogs, heart size may be an additional factor in explaining the absence of arrhythmia in the cat.

Influence of site of stimulation on measurement of ventricular vulnerability in the normal and ischemic feline heart.

Site of stimulation is an important variable in the inducibility of ventricular tachycardia in both non-human animal infarction models and in humans; that is, proximity of the stimulating electrode to the site of reentry facilitates the induction of sustained arrhythmia. Whether site of stimulation is decisive in measurement of vulnerability to ventricular fibrillation (VF) during acute coronary occlusion has not been fully evaluated. We measured VF thresholds in 9 chloralose-anesthetized cats at 2 right ventricular and 3 left ventricular sites (2 endocardial, 3 intramural) before and after abrupt occlusion of the anterior descending coronary artery. VF thresholds were measured using a single stimulus of increasing intensity delivered during ventricular drive. Although VF thresholds were lower at endocardial sites, there were no significant differences in VF threshold among any of the sites tested at control. After occlusion, VF thresholds fell to a similar extent at all 5 sites tested. The percent reduction in VF threshold at any site was not influenced by the sequence of testing. VF may be precipitated from multiple sites and, unlike ventricular tachycardia, does not represent an isolated focus of arrhythmogenicity.

The action of reserpine, 6-hydroxydopamine, and bretylium on digitalis-induced cardiotoxicity.

This study determined whether the protective effect of reserpine against ouabain-induced ventricular arrhythmias in the cat is due to an action of the drug on the adrenergic nerve terminal. Reserpine (5 mg/kg i.p.) administered 24 h prior to ouabain (2 micrograms/kg per min i.v., until death) increased the dose of ouabain to produce premature ventricular contractions, ventricular tachycardia, and death from 77.3 +/- 5.2 to 105.0 +/- 6.0; 84.9 +/- 5.2 to 132.7 +/- 9.1; and 108.8 +/- 4.0 to 165.7 +/- 10.4 micrograms/kg, respectively (P less than 0.05). When 6-hydroxydopamine (6OHDA; 20 mg/kg i.v.) was given 3 days prior to the experiment, the protective effect of reserpine was not evident. When bretylium (20 mg/kg i.v., 2 h prior to ouabain) was administered to animals previously treated with reserpine, the dose of ouabain which produced premature ventricular contractions, ventricular tachycardia, and death was increased to 109.0 +/- 7.2; 146.1 +/- 12.6; and 165.8 +/- 7.6 micrograms/kg, respectively (P less than 0.05). However, the magnitude of this protective action was similar to that produced by reserpine alone. Lathers et al. (Fed. Proc. 40, 672, 1981) reported that bretylium alone provides protection of a similar order of magnitude as reserpine. Thus, the effects of reserpine and bretylium were not additive; this indicates that the two agents may be acting on the same locus or they may be acting at different sites with the action of one drug masking or blocking the action of the other. Since 6OHDA prevented the action of reserpine on ouabain-induced ventricular arrhythmia and since 6OHDA only produces degeneration of adrenergic nerve terminals, it is probable that the protective effect of both reserpine and bretylium is due to an action at the adrenergic nerve terminal. The heart rate and blood pressure were not involved in the antiarrhythmic effects of reserpine.

Preserving the best of the art of teaching.

Teachers often develop unique methods to help students learn, but these techniques may be lost when they retire from the profession. In the 15 years that they have conducted the Effective Teaching Workshop: Improving Your Skills, the authors of this paper have observed presentations of many innovative teaching methods. The article describes five methods recently presented at the annual workshop: the use of a flipchart with slides; the use of Polarmotion overhead transparencies; an asthma simulation; a breast-mass simulation; and teamwork and game-playing. The authors present these techniques in the hope of reaching a broader audience, and to stimulate other teachers to submit descriptions of innovative teaching methods for possible publication in the Ideas for Medical Education column.

The role of the generalist physician initiative in the merger of Hahnemann University and Medical College of Pennsylvania.

Unique in the history of academic medicine in the 20th century was the 1993 merger of two medical schools, Hahnemann University and The Medical College of Pennsylvania, to create Allegheny University of the Health Sciences, the largest private medical school in the United States. During the early, most critical phase of the merger process, the two faculties were brought together to plan and submit an application for The Robert Wood Johnson Foundation's Generalist Physician Initiative (GPI). This action had a profound and lasting impact on the merger of the two schools and the educational enterprise that subsequently evolved. The GPI grant was awarded to the merged school in the midst of this complex merger rife with major changes, all with their attendant fears and frustrations. During and just after the merger, at a time when faculty and staff were somewhat uncertain about the direction of the university, the GPI provided a focus with a clear set of goals and objectives. Despite the unprecedented changes occurring in the organization and personal and professional concerns, faculties from the two institutions were able to join in pursuing the generalist initiative and its associated curriculum reform. This single, pervasive effort was a significant factor in forming a unified faculty of a united school of medicine. This sense of unity was put to the test when, in July 1998 the university, along with its affiliated hospital system, filed for bankruptcy. The goals of this extraordinary action were to sell the hospitals to another organization, thereby removing from the university the burden of supporting hospital-based clinical programs and allowing the university to emerge as a freestanding academic institution focusing on its core mission of education and the principles embodied in the GPI.

Redesigning the surgery clerkship at MCP Hahnemann School of Medicine to address the educational needs of generalists.

This article describes how the surgery clerkship at MCP Hahnemann School of Medicine was redesigned to provide all students a well-rounded general professional education and to address the specific educational needs of generalists. During the 12-week clerkship, students spend eight weeks on two different general surgery rotations, which include significant experiences in outpatient settings. The evaluation and management of common general surgical problems, as well as the holistic approach to patient care, are emphasized. A nurse educator, recruited through funding obtained from The Robert Wood Johnson Foundation's Generalist Physician Initiative, provides formal instruction in holistic care and teaches bedside procedures. Two weeks are devoted to focused surgical subspecialty experiences addressing common conditions and are conducted primarily in outpatient settings. The remaining two weeks include an integrated musculoskeletal disease rotation, including orthopaedic surgery, rheumatology, physiatry, and radiology. Didactic teaching includes criteria for referral of patients from generalists to specialists. The new clerkship model has been well received by the students. Review of student logs for the first six months indicates the breadth of surgical experience has been maintained and appropriate balance achieved between simple and complex surgical cases. Further evaluation of the model will continue through longitudinal follow-up.

A statewide system to track medical students' careers: the Pennsylvania model.

In 1994 the Commonwealth of Pennsylvania announced a statewide Generalist Physician Initiative (GPI) modeled after The Robert Wood Johnson Foundation's GPI. Three-year grants totaling more than $9 million were awarded to seven of Pennsylvania's medical schools, including two that had already received GPI grants from the foundation. Stimulated by these initiatives, the state's six allopathic and two osteopathic medical schools decided to work together to develop a collaborative longitudinal tracking system to follow the careers of all their students from matriculation into their professional careers. This statewide data system, which includes information for more than 18,000 students and graduates beginning with the entering class of 1982, can be used to evaluate the impact of the Pennsylvania GPI, and it also yielded a local longitudinal tracking system for each medical school. This paper outlines the concept of the system, its technical implementation, and the corresponding implications for other medical schools considering the development of similar outcomes assessment systems.

Effect of age on the cardiotoxic action of digitalis.

The cardiotoxic effect of ouabain was explored in rabbits at different ages. The dose of ouabain necessary to produce ventricular tachycardia and death in 1-to 4-week-old rabbits was significantly greater than that required in older animals. In the 1 to 3-week-old animals, ventricular fibrillation occurred only once whereas in animals older than 3 weeks, fibrillation occurred in 23 of 31 animals. A similar pattern of sensitivity to ouabain was observed in bilaterally vagotomized animals. Neither the initial heart rate nor the potassium content of the ventricles in the different age groups appeared to have any influence on the change in the cardiotoxic dose of ouabain. Heart weight increased during the interval when the occurrence of fibrillation increased but it may not fully explain the alteration in the mode of death since fibrillation occurred in some of the younger animals with bilateral vagotomy before the heart weight increased. The catecholamine content of ventricles from 4-to 12-week-old rabbits was significantly greater than that in 1- or 3-week-old rabbits. The age-dependent decrease in the dose of ouabain necessary to produce ventricular tachycardia, ventricular fibrillation and death appeared to be associated with an increase oof ventricular norepinephrine content, although other factors may also play an important part in this response.

Changes in vagal activity and response to muscarinic receptor agonists with age.

The response to vagal nerve and muscarinic receptor stimulation was evaluated in young (90 day), adult (365 day) and old (730 day) male F-344 rats anesthetized with urethane. Bilateral vagotomy produced a significant increase in heart rate in the young and adult animals (p < 0.05), while no change in heart rate occurred in the old animals. Stimulation of the right vagus nerve produced a frequency dependent decrease in response to right vagus nerve stimulation with age (p < 0.05; analysis of variance), i.e., old animals had a smaller decrease in heart rate over the same frequency range of nerve stimulation than either the young or adult animals. The effect of age on the response of the muscarinic receptor was examined using cumulative doses of methacholine administered by bolus injection. Methacholine produced a dose dependent decrease in heart rate and blood pressure. The heart rate response to methacholine was diminished in the older animals (p < 0.05; analysis of variance). Similar results were obtained after atropine although the doses of methacholine employed were much greater. In contrast, although methacholine decreased blood pressure in all animals at each age there was no change in the hypotensive response to methacholine with age. These data indicate that there is a diminution in vagal control of heart rate with age as well as the response of the vagus nerve to stimulation. Furthermore, the response of the muscarinic receptor in the heart declines with age while that in the peripheral vasculature does not.

A study skills workshop as an integral part of orientation to medical school: the establishment of self-directed learning.

The MCP Program, a prematriculation academic support service workshop for all incoming students, combines techniques of learning style identification, study skills, time management and stress control. This has resulted in higher class performance, the formation of collegial relationships and an early emergence of professional behaviors and leadership.

Modulation of arachidonic acid metabolites and vulnerability to ventricular fibrillation during myocardial ischemia in the cat.

To determine the relative importance of arachidonic acid pathway products on vulnerability to ventricular fibrillation (VF), we examined the effects of synthesis inhibitors and a receptor blocker acting in the cyclooxygenase (C) and lipoxygenase (L) pathways on VF thresholds in a feline model of coronary occlusion. Thresholds for the induction of VF wer measured before and after a 5-minute coronary occlusion in drug-treated animals and control subjects. Animals were treated with BW755c, a dual L and C inhibitor, CGS-8515, and L inhibitor, FPL-55712, a leukotriene receptor blocker, or sulfinpyrazone, a C inhibitor. BW755c, CGS-8515, and FPL-55712 all prevented an otherwise significant fall in VF threshold during coronary occlusion (p less than 0.01) independent of an effect on effective refractory period, heart rate, or blood pressure. In contrast, sulfinpyrazone, the only compound devoid of an effect on the L pathway, did not protect against an occlusion-related fall in VF threshold. BW755c and CGS-8515 inhibited the synthesis of L and C metabolites coincident with their protection against VF (p less than 0.01). We conclude that agents that antagonize the effects of L products protect against enhanced ventricular vulnerability during acute ischemia, whereas C inhibition alone may not afford this protection.