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Abnormal Cardiac Rhythm
Published in Amar Bhide, Asma Khalil, Aris T Papageorghiou, Susana Pereira, Shanthi Sairam, Basky Thilaganathan, Problem-Based Obstetric Ultrasound, 2019
Amar Bhide, Asma Khalil, Aris T Papageorghiou, Susana Pereira, Shanthi Sairam, Basky Thilaganathan
Ectopic beats are the most common form of fetal arrhythmia and usually present in the third trimester. Ectopic beats are caused by an extra beat arising prematurely and outside the natural pacemaker. They are of no clinical relevance, are not a sign of fetal distress, and do not need any form of treatment. The irregular rhythm due to ectopic beats tends to spontaneously resolve near term and does not need specific post-natal follow-up. In the rare case of bigeminy or very frequent ectopic beats, there is a risk of the fetus developing a persistent tachyarrhythmia, and therefore weekly monitoring of the fetal heart rate is recommended.
In Vivo and In Vitro Cardiac Preparations Used in Antiarrhythmic Assays
Published in John H. McNeill, Measurement of Cardiovascular Function, 2019
Other classification criteria used for arrhythmias are not universally agreed upon. The Lambeth conventions attempted to standardize the study of arrhythmias induced by ischemia, infarction, and reperfusion.11 The definitions, which can also be applied to electrically and chemically induced arrhythmias, state that the EKG should be used as the sole means for classifying and quantifying arrhythmias. Figure 1 shows characteristic EKGs for a number of arrhythmias commonly observed. Extra beats of non-sinus node origin are known as extra-systoles (or more accurately as extradepolarizations). They are premature in the sense that they occur before an expected sinus beat. Bigeminy is a premature beat coupled to every sinus heart beat. Two or three consecutive premature beats are salvos, whereas four or more consecutive premature beats constitute an episode of tachycardia. The classification of ventricular tachycardia (VT) by rate or hemodynamic consequences is only useful in special circumstances and is likely to be species dependent.
The stimulus
Published in Alan Weiss, The Electroconvulsive Therapy Workbook, 2018
A major concern with the stimulus dose titration method has been that it may expose the patient to unnecessary cardiac risks with repeated subcon- vulsive stimulation initiating a sustained para-sympathetic response. The early ECT literature contained reports of adverse cardiovascular events including bradycardia, bigeminy, nodal arrhythmias and a drop in blood pressure (McCall, Reid and Ford, 1994), with other reports of sudden cardiac standstill, hypertension and tachycardia (Partridge, Weinger and Hauger, 1991; Wells, Zelcer and Treadrae, 1988; Wulfson, Askanazi and Finck, 1984). These reports lead to recommendations that "subshocks" should be avoided, particularly in clinically compromised patients (Abrams, 2002).
Focus on cardiac rhythm disorders
Published in Acta Cardiologica, 2023
Patrizio Lancellotti, Caroline Piette
Myocardial ischaemia is a common cause of arrhythmia, and the potential mechanism of ischaemic arrhythmia is quite complex and diverse. At present, in animal experiments, arrhythmia models can be constructed through a variety of methods, which are associated with high scientific research costs, high technical difficulty, complicated operation, low survival rate of the experimental animals, and poor reproducibility. Guo et al. showed in a rat model that the combination of subcutaneous and intraperitoneal injections of isoproterenol is more likely to induce arrhythmia than a single injection route [9]. Differential diagnosis of broad QRS tachycardia with left (L) BBB morphology is broad. The analysis of its response to adenosine can allow to make a correct diagnosis. The acceleration of tachycardia with disappearance of LBBB can indicate the presence of an accessory pathway (AP) on the ipsilateral side. However, this is not a phenomenon one would expect as a response to adenosine, which would most likely terminate such tachycardia [10]. Frequent junctional beats occurring in bigeminy are extremely rare. In very unusual situations, these ectopies may be responsible for a retrograde, but also an anterograde block, leading to a pseudo paroxysmal atrioventricular bloc [11, 12].
The potassium channel blocker, dalfampridine diminishes ouabain-induced arrhythmia in isolated rat atria
Published in Archives of Physiology and Biochemistry, 2019
Nahid Ghebleh Zadeh, Gholamhassan Vaezi, Azam Bakhtiarian, Zahra Mousavi, Abdolhossein Shiravi, Vahid Nikoui
Figure 4 demonstrates a general comparison in chronotropic and inotropic features between control and treatment groups. In control group, ouabain-induced arrhythmia was obvious and asystole occurred after arrhythmia (a). The intensity of arrhythmia in dalfampridine-treated group was reduced and in some cases, no asystole happened until several hours (b). Atrial beatings and contractile force before incubation of ouabain were similar in both groups (c,d). The shape of arrhythmia in control group was typical bigeminy (twin spikes with strong force, repeatedly), which is the common manifestation of ouabain-induced arrhythmia (e). In dalfampridine-treated group (f), random bigeminy between normal spikes was seen, and it occurred much later than control group. Time of onset of asystole in dalfampridine-treated group (h) was later than control group (g).
Thyroid dysfunction following radiofrequency ablation for benign thyroid nodules: more likely to occur within one-week and in high-risk population
Published in International Journal of Hyperthermia, 2021
Nana Wang, Bowen Zheng, Tao Wu, Lei Tan, Yufan Lian, Yanping Ma, Rui Guo, Shicheng Xu, Longyi Zeng, Wen Xu, Jie Ren
Different from a few studies on the short-term thyroid dysfunction (1.27–3.70% of thyrotoxicosis and 7.41% of hypothyroidism at 1 day) [28,29], we reported a significantly higher incidence (36.00%) of thyroid dysfunction within 1 week after RFA, and all cases were thyrotoxicosis. There are some possible explanations. First, the definitions of thyroid dysfunction were not completely the same. In our study, we defined overt thyrotoxicosis as FT3/FT4 increase plus TSH decrease, and overt hypothyroidism as FT4 decrease plus TSH increase. Second, we emphasized the complete ablation of BTNs, so the ablation volume ratio (which is proved to be related to thyroid dysfunction in our study) may be larger than that in previous studies. Third, the coagulative necrosis caused by RFA may lead to a continuous release of thyroid hormone. As a result, the incidence of thyroid dysfunction at 1 day may be lower than that within 1 week. This finding emphasized the ‘within 1 week’ as a critical time point to detect thyroid dysfunction, especially thyrotoxicosis which can aggravate the cardiovascular-related symptoms. Thus, we suggest highly that this time point should be added in the follow-up plan after RFA, especially in patients with a history of cardiovascular diseases so that a preventive therapy can be implemented in time. In our study, one patient with a solid BTN (the maximum diameter was 52.80 mm) received RFA. Her preoperative electrocardiograph showed frequent multifocal ventricular premature beats (bigeminy). Within 1 week after RFA, she developed subclinical thyrotoxicosis and presented with significant palpitations. This patient was transferred to the cardiologist and took medication for 1 month to control the symptom.