II, III and aVF), and is inverted in aVR, which faces the superior heart surface ( Figure 1.1). The P wave, therefore, is upright in those leads that are directed to the inferior surface of the heart (i.e. towards the feet) to the atrioventricular (AV) junction. ![]() Atrial activation therefore spreads from the sinus node in an inferior direction (i.e. The sinus node lies at the junction of the superior vena cava and right atrium. However, occasionally the P wave in some leads is not visible or is of low amplitude, and it may be necessary to inspect all leads of the ECG to establish that there is sinus rhythm (Figure 1.2). P waveĪtrial activity, the P wave, is usually apparent in most ECG leads ( Figure 1.1). Sinus node activity itself does not register on the electrocardiogram (ECG). The sinus node initiates the electrical impulse that activates atrial and then ventricular myocardium during each normal heartbeat. Normal sinus rhythm is characterised by a rate of 60–100 beats/min PR interval 0.12–0.21 s QRS duration ≤ 0.10 s QTc ≤ 0.44 s. The sinus node impulse is conducted relatively slowly via the AV node to reach the His–Purkinje system, which then conducts very rapidly to activate the ventricular myocardium. If the QRS complex is preceded by a P wave that is not positive in the inferior leads then the rhythm is other than sinus rhythm. Atrial activation travels inferiorly from the sinus node to the atrioventricular (AV) node, resulting in a positive P wave in the inferior ECG leads, II, III and aVF. Rich with example ECGs and designed for ease of access to information, Bennett's Cardiac Arrhythmias is the reference you can trust to help you master arrhythmia diagnosis and provide optimal treatment of any patient under your care. The 8th edition also features the latest guidelines on ECG screening of athletes and clear guidance for anaesthetists and surgeons dealing with patients with arrhythmias an/or implantable devices. Recently-approved anti-arrhythmia drugs.Long QT syndromes and other channelopathies. ![]()
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