Some observations on the mechanism of pressure related atrial fibrillation

In order to investigate the effect of atrial pressure on thepropensity of the atria to fibrillate and the mechanism of thisassociation, the right atrial pressure was changed acutely bytransfusion-bleeding in 12 anaesthetized open-chest dogs. Undervarious atrial pressures the conduction time was measured betweentwo pairs of hook electrodes positioned on the two atrial appendagesrespectively. The effective refractory period was measured bycontinuous pacing of the right atrium at a 250 ms cycle lengthat double threshold intensity and interpolating a progressivelyearlier stimulus after each eighth paced beat. The propensityof fibrillation was studied by rapid (450 min^–1) pacingof the atria at double threshold intensity for 10 s at differentatrial pressures. At a high (14 mmHg) atrial pressure the conductiontime (45.7 ± 14.2 ms) was significantly (P<0.01) longer,the effective refractory period (157.9 ± 15.2 ms) significantly(P<0.01) longer and the atrial fibrillation (11/19 or 57.9%)significantly (X² = 9.95, P<0.001) more common than at alow ( 10 mmHg) pressure (35.2 ± 11.6, 146.2 ±12.4, 3/24 or 12.5%, respectively). Analysis of variance showedthat the probability of atrial fibrillation was significantlyaffected by the atrial pressure but not by either the conductiontime or the effective refractory period The findings suggestthat an increase in right atrial pressure by acute volume overloadprolongs the inter-atrial conduction time and right atrial refractorinessand increases the propensity of the atria tofibrillate by rapidatrial stimulation. The effect of atrial pressure on fibrillationdoes not seem to be mediated by the prolonged atrial refractorinessor conduction time.     

Difficulty and discrimination capacity of examinations estimated on the basis of repeated student failure

This paper examines the difficulty and discrimination capacity of several subjects for problematic students, i.e., those failing repeatedly (re-examined four or more times) in at least one subject. Four hundred and six problematic students were analysed. The difficulty in passing thirty-one mandatory subjects was assessed in two ways:

• 1 on the basis of the attrition rate of the students due to pass the subject,
• 2 on the basis of the percentage of number of failures over the number of examinations.

The discrimination capacity of the same subjects was assessed on the basis of ‘false positive’ and ‘false negative’ results. The result of the evaluation of one subject was considered a false positive if it gave an excellent mark to a problematic student; it was considered a false negative if a student had to be reexamined four or more times before passing, although he had at least one excellent passing mark in one or more subjects. There were 157 excellent marks given to 114 problematic students. The two ways to assess difficulty ranked the thirty-one subjects in a very significantly-similar way. The subjects of the first, second and sixth years of study were considerably more difficult than the other years. A high proportion of false-negative results in a subject did not imply necessarily increased difficulty and vice versa. Thus, only two of the five subjects with the highest proportion of false-negative results belonged to the group of the five most difficult subjects. Also, three of the five subjects with the highest proportion of false-positive results belonged to the group of the five easiest subjects. Finally, only one of the five subjects with the lowest proportion of false (positive plus negative) results belonged to the group of the five most difficult subjects. Examination systems involving oral examinations either alone or in conjunction with written ones were more difficult for the problematic students than those involving purely written examinations, while their discrimination capacity was not significantly different. The discrimination capacity of the subjects involving practical examinations as part of their evaluation system was significantly better than that of those not involving practical examinations. It is concluded that a very permissive examination system presents the problem of repeatedly-failing students. A quasi-open admission system, as in Athens University, associated with a very permissive examination system, leads to a pattern of difficulty, the peaks of which appear, mainly, in the first and last year of studies.     

Carotid Sinus Hypersensitivity in Patients Undergoing Coronary Arteriography:

Carotid Sinus Hypersensitivity and Atherosclerosis. Introduction: The purpose of the present investigation was to study the precise relationship between carotid sinus hypersensitivity (CSH) and both the severity of carotid atherosclerosis and the extent of coronary artery disease in patients who were referred for evaluation for suspected ischemic heart disease.
Methods and Results: Duplex echocardiography and coronary angiography were used to assess carotid and coronary artery atherosclerosis in 130 consecutive patients. Carotid sinus stimulation was performed before coronary arteriography with simultaneous recordings of the ECG and aortic pressure. Coronary artery disease was present in 103 patients (79%). Thirty patients (23.08%) had one-vessel disease (1-VD), 31 (23.85%) had 2-VD, 29 (22.31%) had 3-VD, and 13 patients (10%) had left main coronary artery disease. Carotid artery atherosclerosis was present in 100 patients (76.92%) and carotid disease (diameter stenosis ≥ 50%) was present in 24 patients (18.46%). CSH was found in 33 patients (25%). The incidence of CSH was 9% in patients with carotid stenosis 1%-15%, 17% in patients with stenosis 16%-49%, 85% in patients with stenosis 50%-79%, and 100% in patients with stenosis ≥ 80%. The incidence of CSH was 11%, 17%, 23%, 34%, and 62% in patients with no VD, 1-VD, 2-VD, 3-VD, and left main coronary artery disease, respectively. Stepwise multiple logistic regression analysis revealed that carotid disease and left main coronary artery disease were the most significant determinants of CSH (P < 0.001 and P = 0.013, respectively).
Conclusion: The incidence of CSH increased in proportion to the severity of carotid and coronary atherosclerosis. These data provide evidence that CSH is closely related to severe carotid atherosclerosis or left main coronary artery disease in patients being evaluated for suspected ischemic heart disease.     

Attitudinal educational objectives at therapeutic consultation: measures of performance, educational approach and evaluation

The study aims at measuring doctors' performance while giving therapeutic instructions and testing the effectiveness of an educational technique for affective objectives. For this purpose doctors' performance was analysed into nine components. Twenty-five trainees in internal medicine were observed and rated regarding the nine components, while instructing 40 patients with a chronic disease. Both doctors and patients were then questioned regarding the verbal components of the doctors' performance and the answers were compared to assess the degree of concordance. One to 3 months later the patients were interviewed to assess whether they complied with the instructions or not. Eighteen months later a 4-hour seminar on affective objectives was held, involving listening and small-group discussion on tape-recorded doctor-patient consultations. After completion of the seminar, 25 doctors instructed 39 patients and were assessed as above. The findings suggest that the doctors' performance regarding the nine components did not predict patient compliance. However, sufficient doctor-patient concordance regarding the verbal components of the behaviour significantly predicted patient compliance. Following the seminar, significant improvement was noted in doctors' performance, in doctor-patient communication and in patient compliance. It is concluded that observing the doctors' behaviour independently of the patient does not predict patients' compliance; the analysis of the total doctors' behaviour into components is valid in predicting patient compliance if it is used in order to assess doctor-patient communication; and a programme based on audiotape-assisted education is both simple and effective in improving the trainees' behaviour and communication skills.     

Admission process and final qualification of medical students

Several ways of admission are compared as to their effect on the final drop-out rate under an unlimited system of examinations within the Medical School.
Out of 8260 students admitted during 10 years via several admission systems, 5927 graduated within 16 years from enrolment. A larger drop-out rate (as well as a longer delay in graduating) was observed with students admitted without entrance examinations. An important number of students entering after examinations (45%) were also late in graduating. Among the admission systems used the findings point to the fact that a closed system provides the school with a majority of competent students but excludes a number of students who proved capable of graduating when enrolled in the same school. The findings also point to the need of improvement of the admission process in the closed system or the need for strict first- or second-year evaluation of students in the open system.     

Atrial Pressure and Experimental Atrial Fibrillation

SIDERIS, D.A., et al .: Atrial Pressure and Experimental Atrial Fibrillation . A possible profibrillatory effect on the atria of an elevated atrial pressure and the site of atrial stimulation was examined. In 15 anesthetized dogs, right or left atrial or biatrial pacing was applied at a high rate (300–600/min) for 5 seconds at double threshold intensity under a wide range of atrial pressures achieved by venous or arterial transfusion or bleeding. Induction of atrial fibrillation in 236 of 1,971 pacing runs was associated with a significantly higher (P < 0.001) atrial pressure (21.6 ± 12.2 mmHg, mean ± SD) than maintenance of sinus rhythm (16.8 ± 11.1 mmHg in 1,735 of 1,971 pacing runs). Stimulation of the right atrium resulted in atrial fibrillation more frequently than left atrial or biatrial stimulation, with biatrial stimulation less frequent than right or left atrial stimulation. The induction of atrial fibrillation was related to the atrial pressure and to the site of stimulation but not to the pacing rate or the prepacing heart rate. The prepacing heart rate, associated with failure to induce sustained atrial fibrillation, was higher than that associated with atrial fibrillation in 12 of 15 experiments (significantly in 6) and not significantly lower in 3 of 15. Atrial fibrillation lasting 1 minute or more was more frequently associated with simultaneous stimulation of both atria than of either atrium alone. Thus, an elevated atrial pressure may facilitate the induction of atrial fibrillation. The site of stimulation also plays an important role for both the induction and maintenance of atrial fibrillation in this model.