Sinus Tachycardia

Management of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia and Vasovagal Syncope

Syncope and palpitations are two common clinical presentations, and both pose difficulties in the approach to their management. They are both symptoms of a number of syndromes, and an efficient approach with targeted therapy is challenging. Cardiac arrhythmia specialists, who lack a compact and accessible guide to management, see many patients with these symptoms in consultation.

Biology of the Sinus Node and its Disease

The sinoatrial or sinus node (SAN) is the heart’s natural pacemaker. Located in the superior right atrium, it automatically produces cyclical electrical activity to initiate each heartbeat in normal sinus rhythm. SAN dysfunction (SND) in humans, also known as ‘sick sinus syndrome’, can manifest as pathological bradycardia and asystolic pauses. As a result, SND can lead to symptoms of reduced cerebral perfusion such as dizziness and syncope. However, early SND may be latent and individuals may remain asymptomatic.

HCN4, Sinus Bradycardia and Atrial Fibrillation

HCN4 (hyperpolarisation-activated, cyclic nucleotide gated 4) channels, the pore-forming α–subunits of ‘funny’ channels originally described in pacemaker cells of the sinoatrial node (SAN),1 are responsible for the early phase of diastolic depolarisation in these cells and are key determinants of pacemaker generation and control of heart rate.2–5 HCN4 channels are selectively expressed in the SAN and in the conduction system, and their expression correlates tightly with the presence of spontaneous activity in adult tissue and during development; the degree of correlati

Cardiac Arrhythmias in the Pregnant Woman and the Foetus

Neither supraventricular nor ventricular tachyarrhythmias are uncommon during pregnancy.1,2 When they are diagnosed, patients, relatives and physicians are frequently worried about ectopic beats and sustained arrhythmias.3,4 One should question whether arrhythmias should be treated in the same way as they would be outside pregnancy because all commonly used antiarrhythmic drugs cross the placenta.5 The pharmacokinetics of drugs are altered in pregnancy and blood levels need to be checked to ensure maximum efficacy and avoid toxicity.