![]() ![]() ![]() Readers who are interested in deeper studies are referred to Zipes et al (Clinical Arrhythmology, Elsevier, 2015). The mechanisms underlying cardiac arrhythmias are being unraveled at an increasing pace. Arrhythmology is a very exciting area with intense research activity. This is partly due to the rise of cardiac imaging and invasive electrophysiological methods which enable detailed in vivo studies of arrhythmias. However, this chapter will not elaborate on research in arrhythmology the discussions will be strictly clinical in order to provide the reader with robust knowledge of common arrhythmias. For example, sinus bradycardia (a slow rhythm directed by the sinoatrial node) is a common finding in athletes and during sleep in these scenarios, it should not be considered abnormal. On the other hand, sinus bradycardia developing during physical exercise is considered abnormal, because heart rate must increase during exercise. The latter criterion is important because rhythms that are physiologically justified should not be considered abnormal. The sinoatrial (SA) node is the heart’s pacemaker under normal circumstances and the rhythm is referred to as sinus rhythm.Īn arrhythmia is defined as an abnormal heart rhythm or heart rate, which is not physiologically justified. The similarity of the waveforms indicates that the origin of the impulse is the same. ![]() Definition of heart rhythmĪ rhythm is defined as three consecutive heartbeats displaying identical waveforms on the ECG. The recommendations presented throughout this section are in line with guidelines and recommendations issued by the European Society for Cardiology (ESC), the American Heart Association (AHA), and the American College of Cardiology (ACC). Because the management of arrhythmias, particularly tachyarrhythmias, is often considered difficult, a special section is devoted to the diagnosis and management of arrhythmias. This classification is not flawless but it facilitates differential diagnostics and management of arrhythmias. Ventricular tachyarrhythmias (tachycardia): arrhythmias in which the impulses emanate from the ventricles.Supraventricular tachyarrhythmias (tachycardia): arrhythmias in which the impulses emanate from the atria.Bradyarrhythmias ( bradycardia): arrhythmias that are typically due to dysfunctional automaticity in pacemaker cells or blocking of impulses somewhere along the conduction system.It is appropriate to subdivide cardiac arrhythmias into the following groups: This chapter starts with a discussion on arrhythmogenesis (mechanisms of arrhythmias) and thereafter each arrhythmia is discussed separately. Although a detailed understanding of the mechanisms underlying cardiac arrhythmias is not necessary for all clinicians, it is wise to invest time in grasping the concepts as it will facilitate the understanding of subsequent articles and chapters. The initial discussion will focus on the mechanisms of cardiac arrhythmias. The aim of this chapter is to present the most common arrhythmias in clinical practice. Some drugs should not be used if the patient has a prolonged QT inverval and therefore this will usually be looked at when interpreting an ECG.Mechanisms of cardiac arrhythmias: from automaticity to re-entry In recent years we have become more aware of the importance of the QT interval, the distance between two parts of the electrical wave. These are a sign of atrial fibrillation, a common cause of heartbeat irregularities. In contrast, for a routine ECG arranged by a GP who has noticed an irregular heartbeat, they may be particularly looking for an irregularity and absent P waves. The points of interest may vary depending on the reason for an ECG - for example, a doctor reviewing an ECG done in the emergency department for acute chest pain will be looking for signs of a heart attack. These include the rate (how fast the heart is beating), the rhythm (whether the heartbeat is regular or irregular), the cardiac axis (direction of electrical spread within the heart), and an analysis of the different parts of the electrical wave. When reviewing an ECG, the healthcare professional will look at several different aspects. ![]()
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