Dimitris A. Sideris

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.

Susceptibility of the right and left canine atria to fibrillation in hyperglycemia and hypoglycemia

The objective of this study was to investigate the changes in the refractory period and in the susceptibility to fibrillation of canine atria associated with different levels of glycemia, and the differences in these parameters between the two atria. In 20 anesthetized, open-chest dogs weighing 24 kg, the effective refractory period was measured by atrial pacing with a run of 8 stimuli (S1-S1 350 ms) followed by a progressively earlier S2 until no stimulation of the atrial tissue occurred. The susceptibility to fibrillation was assessed by applying DC at 2, 3, and 4 V for 3 seconds, 7 times each, on the atrial appendage. If fibrillation occurred and persisted for 3 minutes, a transthoracic synchronized shock was delivered (200 J). The refractory period and the susceptibility to fibrillation were assessed under normoglycemia first, and then under hypo and hyperglycemia, in the right and left atrium successively, in random order. The incidence of induced atrial fibrillation in the right atrium was: hypoglycemia 31.96% (132 of 413 attempts); normoglycemia 24.11% (81 of 336; p < 0.05); and hyperglycemia 20.23% (85 of 420). Results for the left atrium were hypoglycemia 52.06% (215 of 413); normoglycemia 40.18% (135 of 336; p < 0.005); and hyperglycemia 32.86% (138 of 420; p < 0.05). Sustained atrial fibrillation (> 3 minutes) occurred significantly more often under hypo rather than hyperglycemia and stimulated the left rather than the right atrium. The refractory period was shortest under hypoglycemia in the left atrium and longest under normo or hyperglycemia in the right atrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Group Psychosocial Intervention on Coronary Risk Factors

The purpose of this study was to investigate whether a psychosocial intervention approach aimed at resolving psychological conflicts could reduce the severity of risk factors for post-acute myocardial infarction patients. Twenty-three patients with a recent myocardial infarction participated in a group psychosocial intervention program which lasted 1 year. Twenty other patients with recent myocardial infarction served as controls. Patients form both groups had regular clinical and laboratory follow-up as well as medication. Mean values for seven risk factors of coronary heart disease (smoking, S; body weight, W; serum cholesterol, C; triglycerides, T; systolic and diastolic blood pressure, SBP, DBP; serum uric acid, U) were compared between the two groups in the 1st, 3rd, 6th and 12th months of the follow-up. The maximal mean improvements of the study versus the control group were as follows: W: -2.82 vs. -1.05 kg; C: -56.04 vs. -6.25 mg/dl; T: -20.61 vs. -2.4 mg/dl; U: -0.57 vs. -0.9 mg/dl; S at 1 year -55.5 vs. -10%. It is concluded that group psychosocial intervention with post-acute myocardial infarction patients considerably reduces some coronary-disease risk factors.

A self-learning approach to history-taking.

Summary. The present study examines the effectiveness of self‐learning in interviewing skills training. Self‐learning was carried out by self‐evaluation of ones interviews by the use of an audiotape. Fifteen doctors specializing in internal medicine listened to their interviews and evaluated themselves against the suggested performance included in a rating scale. This procedure was repeated twice and composed the educational programme. Three main aspects of history‐taking were involved: (1) eliciting patient information; (2) interviewing technique and (3) attitudes toward the patient. Comparison of performance at the first and third interview revealed significant improvement in all three aspects. Doctor‐patient communication and written history performance were involved indirectly in the study but no significant improvement was revealed. The educational approach appeared simple and effective to the doctors. It is suggested that a brief programme of self‐learning with feedback from audiotapes is both convenient and effective, improving essential aspects of history‐taking performance.

Autonomic Nervous System Responses to Personal Stressful Events in Patients with Acute Myocardial Infarction

Background: Life events specific for each individual may influence the onset of acute myocardial infarction (AMI), and we wondered whether recall of such events elicits autonomic nervous system responses in patients. Methods: Thirty-one subjects with AMI, which occurred about 1 month previously (study group), and 22 healthy subjects were interviewed. Whenever the presence of a stressful event was found within the last 2 months before AMI onset, a key phrase of the event was isolated. Each subject was faced with 20 written key sentences (including his/her own sentence if detected) at random order, for 40 s each. At the same time the heart rate (HR) and the galvanic skin response (GSR) were continuously recorded. Pearson r correlations, χ2 and t tests were employed for comparisons between study and control group as well as within each group. Results: A recent exacerbating event was detected in 30/31 AMI patients and in 0/22 healthy subjects. For the 30 AMI patients the values of HR following the sentence of the suspected event, specific for each patient, were statistically significantly higher than the mean values of HR following the remaining 19 ‘neutral’ statements. The same significant difference appeared with regard to GSR values. The mean values of the AMI patients for the 19 neutral statements did not differ significantly from those of the healthy subjects for the 20 neutral statements, either for HR or GSR. Conclusions: Findings suggest that recall of personal stressful events elicited autonomic nervous system responses in AMI patients and, therefore, events with personal significance are related to coronary disease onset.

Effect of Acute Ventricular Pressure Changes on QRS Duration

The effect of acute changes in ventricular pressure is examined on the QRS duration to clarify the mechanism of ventricular pressure-related arrhythmogenesis. Ventricular pressure was changed acutely by arterial transfusion-bleeding into an open-air ventricular pressure reservoir that was either off or on a metaraminol intravenous drip. While maintaining ventricular pressure at several levels, the QRS duration was measured at 200 mm/s paper speed. The QRS duration correlated significantly with the left ventricular pressure in all 14 dogs examined. An average change in ventricular by 100 mmHg was associated with a change of about 18% in the QRS duration. An acute ventricular pressure elevation impairs the ventricular conduction, which may contribute to ventricular pressure-related arrhythmogenicity.

Anatomical origin of pressure-related ventricular ectopic rhythms

In order to determine the origin of pressure-related ectopic rhythms, the main arteries were clamped in 11 anesthetized dogs, or the arteries or veins were transfused, while on or off metaraminol. The epicardial right atrial electrogram, the intracavity electrograms and the pressure of the two ventricles were recorded. Sinus rhythm was associated with 64/64 (100%) of the control periods off metaraminol, but only 19/50 (38%) of the clamping of the main arteries (P << 0.0005). In 14/27 aortic clampings ectopic beats appeared from the left ventricle and in 13/27 from the right one. In 4/23 clampings of the pulmonary artery ectopic beats appeared from the left ventricle and in 15/23 from the right one (P < 0.05). Sinus rhythm was associated with significantly lower left ventricular systolic pressure than any ventricular arrhythmia. The left ventricular systolic pressure associated with ectopic rhythms from the left ventricle was significantly (P < 0.005) higher than that associated with those from the right ventricle. The right ventricular systolic pressure during sinus rhythm was significantly (P < 0.005) lower than that during ectopic rhythm from any ventricle. It is concluded that a rise in the pressure of one ventricle tends to cause ventricular ectopic rhythms originating predominantly, but not exclusively, from this ventricle. The origin of ventricular ectopic rhythms from the right ventricle does not preclude that the arrhythmia may respond favorably to lowering of the systemic pressure.

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:

The Journal’s Appreciation

Fax + 41 61 306 12 34 E-Mail karger@karger.ch www.karger.com