tailieunhanh - Ebook Clinical arrhythmology: Part 2

(BQ) Part 2 book "Clinical arrhythmology" presents the following contents: Diagnosis, prognosis and treatment of arrhythmias; the ECG and risk of arrhythmias and sudden death in different heart diseases and situations. | CHAPTER 5 Active Ventricular Arrhythmias In this chapter we will discuss premature ventricular complexes PVC both isolated and in runs and the different types of ventricular tachycardia VT as well as ventricular fibrillation and ventricular flutter Chapter 1 Table . Premature ventricular complexes Concept Premature ventricular complexes PVC are premature impulses complexes that originate in the ventricles. Therefore they present a different morphology from that of the baseline rhythm. If the PVC are repetitive they form pairs two consecutive PVC or VT runs 3 Figures and . Conventionally a VT is considered to be sustained when it lasts for more than 30 s. Infrequent short runs of non-sustained monomorphic VT are included in this section. They correspond to Type 4B in Lown s classification Lown and Wolf 19 71 Figure and Table . In this section we have not included runs of VT when they occur very frequently repeated monomorphic non-sustained VT Figure as they present clinical hemodynamic and therapeutic features that are more similar to sustained VT than to isolated PVC Figure see Other monomorphic ventricular tachycardias . Torsades de Pointes-type VTs Dessertene 1966 will not be included either. Although they occur in runs they are considered polymorphic VT and have quite different prognostic and therapeutic implications compared to isolated PVC or the short runs of classical monomorphic VT Figure . ClinicalArrhythmology First Edition. Antoni Bayés de Luna. 2011 John Wiley Sons Ltd. Published 2011 by John Wiley Sons Ltd. ISBN 978-0-470-65636-5 Mechanisms The PVC may be caused by extrasystolic or para- systolic mechanisms Figures and I A 1 Extrasystoles which are much more frequent are induced by a mechanism related to the preceding QRS complex. For this reason they feature a fixed or nearly fixed coupling interval Figure . This is generally a reentrant mechanism usually micro-reentry but also branch-to-branch or .