Ebook Clinical arrhythmology: Part 2
➤ Gửi thông báo lỗi ⚠️ Báo cáo tài liệu vi phạmNội dung chi tiết: Ebook Clinical arrhythmology: Part 2
Ebook Clinical arrhythmology: Part 2
CHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2ifferent types of ventricular tachycardia (VT). as well as ventricular fibrillation and ventricular Hutter (Chapter 1. Table 1.1).Premature ventricular complexesConcept•Premature ventricular complexes (PVC) are premature impulses (complexes) that originate in the ventricles. Therefore, they present Ebook Clinical arrhythmology: Part 2a different morphology from that of the baseline rhythm.•If the PVC are repetitive. they form pairs (two consecutive PVC) or VT runs (^3) (Figures 5.1Ebook Clinical arrhythmology: Part 2
B and 5.31. Conventionally, a VT is considered to be sustained when it lasts for more than 3()s. Infrequent short runs of non-sustained monomorphic VTCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2e have not included runs of VT when they occur very frequently (repeated monomorphic non-sustained VT) (Figure 5.41. as they present clinical, hemodynamic, and therapeutic features that are more similar to sustained VT than to isolated PVC (Figure 5.3) (see Other monomorphic ventricular tachycardias Ebook Clinical arrhythmology: Part 2). Torsades de Pointes-type VTs (Dessertene 1966) will not be included either. Although they occur in runs, they are considered polymorphic VT and havEbook Clinical arrhythmology: Part 2
e quite different prognostic and therapeutic implications compared to isolated pvc or the short runs of classical monomorphic VT (Figure 5.5).ƠDUC0Ì ACHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2ismsThe PVC may be caused by extrasystolic or para- _____systolic mechanisms (Figures 5.1 and 5.21:A1)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 5.1). Th Ebook Clinical arrhythmology: Part 2is is generally a reentrant mechanism (usually micro-reentry, but also branch-to-branch. or around a necrotic or fibrotic area) (sec Figure 3.6). TheyEbook Clinical arrhythmology: Part 2
may also be induced by post-potentials (triggered activity) (see Figure 3.5). or. in some exceptions. may be due to supernormal excitability and condCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2stimulus, which triggers the premature impulse. This may happen when the stimulus falls in the supernormal excitability zone (see Figure 3.1 5).2)Parasystoles arc much less frequent. They are impulses that are independent of the baseline rhythm. The electrophysiologic mechanism is an ectopic focus p Ebook Clinical arrhythmology: Part 2rotected from depolarization by the impulses of the baseline rhythm. In general, this is due to the presence of a unidirectional entrance block in theEbook Clinical arrhythmology: Part 2
parasystolic focus (see Figure 3.17).Table 5.1 Lown classification of premature ventricular complexes (PVC) (Lown and Wolf 19711. according to prognoCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2omorphic ventricular tachycardia Grade 5: R/T Phenomenon (PVC falls on the preceding T wave)181182Electrocardiographic Diagnosis of ArrhythmiasAextrasystoles. first bigeminal, then one run of non-sustained ventricular tachycardia (VT) (four complexes).Figure 5.2 An example of parasystole. Note the v Ebook Clinical arrhythmology: Part 2ariable coupling intervals. 760ms. etc., the interectopic intervals that arc multiples 2 380,2400.2400 X 3. etc. and the presence of a fusion complexEbook Clinical arrhythmology: Part 2
(I-1.On the other hand, there usually exists a certain degree of exit block in the parasystolic focus (generally 2x1. 3x 1. or Wenckebach-type). accouCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2 the occurrence of parasystolic VT (see Other monomorphic ventricular tachycardias). Parasystolic impulses can only activate the ventricular myocardium and originate a QRS complex if the myocardium is not in the absolute refractory period (ARP).Consequently, not all the impulses originating in the p Ebook Clinical arrhythmology: Part 2arasystolic focus may be detected in the electrocardiogram (ECG) tracing (Figure 5.2). The fact that the parasystolic focus is independent from the baEbook Clinical arrhythmology: Part 2
seline rhythm explains the two principal electrocardiographic characteristics of parasystole: (a) the coupling intervals are variable, and (b) the intCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2 could be responsible for some types ofhttps://khothuvien.cori!Active Ventricular Arrhythmias 183' Y JYFigure 5.3 Dificrcnl types of premature ventricular complexes (PVQ according to Ixjwn’s classification. A: Frequent PVC. B: Polymorphic PVC. C: A pair of PVC. D: Run of ventricular tachycardia (VT) Ebook Clinical arrhythmology: Part 2. E and F: Examples of R/T phenomenon with a pair and one run.Infrequent parasystole, which do not fulfill these criteria I modulated parasystole! (OrEbook Clinical arrhythmology: Part 2
ctoeta/. 1983). The easiest mechanism occurs when the discharge rate of the baseline rhythm is a multiple of the rate of parasystolic focus (for instaCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the di Ebook Clinical arrhythmology: Part 2al.Etiological and clinical presentationCHAPTER 5Active Ventricular Arrhythmias111 this chapter we will discuss premature ventricular complexes I p VC I both isolated and in runs, and the diGọi ngay
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