Complex Arrhythmias Due to Reversible Causes

Mechanical circulatory support in ventricular arrhythmias

In atrial and ventricular tachyarrhythmias, reduced time for ventricular filling and loss of atrial contribution lead to a significant reduction in cardiac output, resulting in cardiogenic shock. This may also occur during catheter ablation in 11% of overall procedures and is associated with increased mortality. Managing cardiogenic shock and (supra) ventricular arrhythmias is particularly challenging. Inotropic support may exacerbate tachyarrhythmias or accelerate heart rate; antiarrhythmic drugs often come with negative inotropic effects, and electrical reconversions may risk worsening circulatory failure or even cardiac arrest. The drop in native cardiac output during an arrhythmic storm can be partly covered by the insertion of percutaneous mechanical circulatory support (MCS) devices guaranteeing end-organ perfusion. This provides physicians a time window of stability to investigate the underlying cause of arrhythmia and allow proper therapeutic interventions (e.g., percutaneous coronary intervention and catheter ablation). Temporary MCS can be used in the case of overt hemodynamic decompensation or as a “preemptive strategy” to avoid circulatory instability during interventional cardiology procedures in high-risk patients. Despite the increasing use of MCS in cardiogenic shock and during catheter ablation procedures, the recommendation level is still low, considering the lack of large observational studies and randomized clinical trials. Therefore, the evidence on the timing and the kinds of MCS devices has also scarcely been investigated. In the current review, we discuss the available evidence in the literature and gaps in knowledge on the use of MCS devices in the setting of ventricular arrhythmias and arrhythmic storms, including a specific focus on pathophysiology and related therapies.

Nonutility of Diagnostic Testing in Ambulatory Patients With Supraventricular Tachycardia

BACKGROUND

Supraventricular tachycardia (SVT) is the most common arrhythmia in the pediatric population. Patients often present to the emergency department and undergo extensive diagnostic assessment. The objective of this study is to determine the frequency of diagnostic studies obtained in such patients and to assess clinical significance of these results.

METHODS

A retrospective study was performed from 2011 to 2018 in a single-center ED, including patients 21 years of age or younger presenting with SVT without shock.

RESULTS

A total of 40 patients with 92 encounters were included for analysis. The mean age was 8.58 (±5.51) years; 55% female. A total of 67.4% underwent serologic laboratory evaluation, of which 8 (12.9%) had any abnormality. Only one was deemed clinically significant to warrant intervention. Nearly 30% of patients underwent chest radiography, with no clinically significant findings.

CONCLUSIONS

Patients undergoing ED management of uncomplicated SVT are likely to undergo laboratory investigation and unlikely to have abnormal studies impacting their care. Given the associated risk of false-positive studies, the discomfort to the patient and parent, and cost of these studies, routine laboratory or radiographic investigation in this population may be unwarranted.

Acute ST-segment elevation myocardial infarction: to be or not to be?

Calcium has a significant effect on cells in the myocardium, affecting conduction, intracellular signaling and contraction of muscle fibers. In fact, calcium levels could affect myocardial action potential and affect heart conduction. Hypocalcemia manifest on ECG with arrythmias or QT prolongation, in some extraordinary cases, it could present with variations in the ST segment, which requires the study of differential diagnoses of cardiac origin, such as acute myocardial infarction with ST elevation (STEMI) or pericarditis. We expose a case of a 28-year-old male patient who arrived at the emergency department with chest pain and was misdiagnosed with STEMI, after a complex process finally it was a severe hypocalcemia mimicking acute myocardial infarction.

Emerging physiological and pathological roles of MeCP2 in non-neurological systems

Numerous neurological and non-neurological disorders are associated with dysfunction of epigenetic modulators, and methyl CpG binding protein 2 (MeCP2) is one of such proteins. Initially identified as a transcriptional repressor, MeCP2 specifically binds to methylated DNA, and mutations of MeCP2 have been shown to cause Rett syndrome (RTT), a severe neurological disorder. Recently, accumulating evidence suggests that ubiquitously expressed MeCP2 also plays a central role in non-neurological disorders including cardiac dysfunction, liver injury, respiratory disorders, urological dysfunction, adipose tissue metabolism disorders, movement abnormality and inflammatory responses in a DNA methylation dependent or independent manner. Despite significant progresses in our understanding of MeCP2 over the last few decades, there is still a considerable knowledge gap to translate the in vitro and in vivo experimental findings into therapeutic interventions. In this review, we provide a synopsis of the role of MeCP2 in the pathophysiology of non-neurological disorders, MeCP2-based research directions and therapeutic strategies for non-neurological disorders are also discussed.

Mechanisms of Chronic Metabolic Stress in Arrhythmias

Cardiac arrhythmias are responsible for many cardiovascular disease-related deaths worldwide. While arrhythmia pathogenesis is complex, there is increasing evidence for metabolic causes. Obesity, diabetes, and chronically consuming high-fat foods significantly increase the likelihood of developing arrhythmias. Although these correlations are well established, mechanistic explanations connecting a high-fat diet (HFD) to arrhythmogenesis are incomplete, although oxidative stress appears to be critical. This review investigates the metabolic changes that occur in obesity and after HFD. Potential therapies to prevent or treat arrhythmias are discussed, including antioxidants.