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Cardiac Arrythmias
Published in Charles Theisler, Adjuvant Medical Care, 2023
Oral magnesium has also been used for many years in patients with symptomatic extrasystoles. Studies show that the incidence of extrasystoles, as well as patients’ symptoms, were reduced during oral magnesium ther apy.1 In one study, giving magnesium orally (300 mg/day for at least six weeks) or intravenously was helpful for treating arrythmias.4,5
Basic medicine: physiology
Published in Roy Palmer, Diana Wetherill, Medicine for Lawyers, 2020
Like all muscle, the myocardium or cardiac muscle is an excitable tissue, influenced by electrical impulses but with an inherent contractility. Its most excitable part is called the sino-atrial node, which acts as the natural pacemaker of the heart; its rate of electrical discharge governs the heart rate. If its conducting system is damaged, the heart beats at a much slower rate than normal (about 40 beats per minute as opposed to 60–80), which is inadequate to support normal activity. This condition of heart block may be controlled by inserting an artificial pacemaker. The electrical activity of the heart can be studied by means of an electrocardiogram (ECG) The ECG pattern is disorganized by the death of muscle after a myocardial infarct (heart attack), which is precipitated by thrombosis of the coronary arteries, i.e. the heart’s own blood supply. One consequence of a heart attack can be the development of a cardiac arrhythmia, i.e. loss of the normal regular rhythm as judged by feeling the pulse and looking at the ECG. Extra beats or extrasystoles, when the pulse seems to skip a beat, may be relatively harmless. Atrial fibrillation (the loss of a concerted atrial contraction) can be more troublesome, while ventricular fibrillation is fatal unless the heart is shocked back into a normal rhythm by means of a defibrillator.
The Place of Primary Cardiac Stress Damage in the Pathogenesis of Arrhythmias, Ischemic Disease, and Sudden Cardiac Death
Published in Felix Z. Meerson, Alexander V. Galkin, Adaptive Protection of The Heart: Protecting Against Stress and Ischemic Damage, 2019
Felix Z. Meerson, Alexander V. Galkin
At the next stage of our work,49 54 pilots of the highest class aged 35 to 53 were compared in a standard test with veloergometric load (VEL) and in solving professional tasks in a flight simulator (takeoff, landing, failures, etc.). Arrhythmias turned out to occur only in 5 pilots under VEL, but in 34, i.e., more than 60%, in the simulator. In all cases extrasystoles in the simulator proved only occasional and mostly appeared during “breakdown in flight” and “flight continued after breakdown”. Despite the small number of extrasystoles during flight simulation, further studies with the use of ECG monitoring showed these results to be really significant. Figure 6 displays the results of monitoring a group of pilots who either had (seven individuals) or did not have (four individuals) extrasystoles during flight simulation. It can be seen that in persons who had rhythmic disturbances in simulation the number of atrial extrasystoles is several times greater than in those who had none. Ventricular extrasystoles were completely absent from the latter group, but observable throughout the day in the former.
Paroxysmal 2/1 atrioventricular block: do not pace! Why and what is the mechanism?
Published in Acta Cardiologica, 2023
Nader Wansa, Steven Vercauteren, Luc De Roy
During the stress test, the extrasystoles disappeared, followed by a stable sinus rhythm without AV conduction disturbances. An electrophysiological (EP) study showed an AH Interval of 98 ms and an HV interval of 55 ms. There was no retrograde conduction during right ventricular pacing. At times, junctional ectopic beats appeared, sometimes in bigeminy with a clear His deflection preceding each QRS, without retrograde conduction and dissociated from the spontaneous, non-reset sinus P wave. We could record two abrupt episodes of 2/1 atrioventricular block occurring concomitantly with the disappearance of the bigeminy (Figure 2). At the endocardial level (Figure 3), a low voltage His deflection without conduction to the ventricles, occurred before but dissociated from every not conducted sinus P wave. These His potentials reflected the persistence of the ectopic bigeminal firing. We were able to assume the approximate location of these extrasystoles from the recordings of a multipolar catheter positioned at the His bundle level (Figure 3). Ajmaline and flecainide completely suppressed the junctional ectopic beats, with the restoration of normal AV conduction and specifically the absence of HV interval prolongation.
Cardiac auscultation predicts mortality in elderly patients admitted for COVID-19
Published in Hospital Practice, 2022
Noel Roig-Marín, Pablo Roig-Rico
After conducting cardiac auscultation, electrocardiograms were performed and they confirmed the presence of an arrhythmia. Different types of arrhythmias were recorded, such as those with multifocal atrial rhythm/wandering atrial pacemaker (Figure 1a). Another type of arrhythmia was one in which extrasystoles were present, as in the following figure in which premature ventricular contractions are observed (Figure 1B). Another type of arrhythmia registered was atrial fibrillation (Figure 1C), but this type of arrhythmia was largely associated with cardiac pathology already registered in the past. Therefore, atrial fibrillation was a less relevant finding, since most arrhythmias were not ex novo. Consequently, it was essential to include the variable of the presence of known cardiac arrhythmias in the multivariate analysis of the logistic regression. The ex novo arrhythmia that presented a higher mortality rate was multifocal atrial rhythm. Isolated ectopic beats had a more benign course and prognosis compared to multifocal atrial rhythm. No significant difference in mortality rate was detected between patients with known atrial fibrillation and the finding of ex novo atrial fibrillation; probably because the study is composed of a small population group.
4-Week toxicity study of biosimilar natalizumab in comparison to Tysabri® by repeated intravenous infusion to cynomolgus monkeys
Published in Drug and Chemical Toxicology, 2022
Tomasz Grabowski, Jost Leuschner, Shayne Gad
The visual assessment of the ECG did not reveal any test or reference item-related abnormalities of the electrical complexes or any test or reference item-related changes of the heart rate in the male and female monkeys treated with PB006 or Tysabri® at dose levels of 3 or 30 mg/kg b.w. every other day during the four-week treatment period. Pathological arrhythmia in the form of ventricular extrasystoles (9 times) was noted in one female animal treated with 3 mg PB006/kg b.w. every other day 5 min. p.a. on test day 1. Supraventricular extrasystoles were observed (2:1) in one male animal treated with 3 mg PB006/kg b.w. every other day predose and 5 min. p.a. on test days 1 and 30. These findings are regarded to be of spontaneous nature. The peripheral arterial systolic and diastolic blood pressure as well as the resulting mean blood pressure were within the normal physiological limits in the animals treated with PB006 or Tysabri® at dose levels of 3 or 30 mg/kg b.w. every other day during the four-week treatment period.