Ventricular Tachycardia
Ventricular tachycardia (VT) is generally a severe arrhythmia that often impairs heart function considerably and may be a precursor of ventricular fibrillation. We distinguish the impact of VT on haemodynamics and on prognosis.
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Ventricular Tachycardia
AtaGlance Ventricular tachycardia (VTI is generally a severe arrhythmia that often impairs heart function considerably and may be a precursor of ventricular fibrillation. We distinguish the impact ofVT on haemodynamics and on prognosis. The haemodynamic response to VT depends on the preexisting left (or rightl ventricular ejection fraction and the rate and duration of tachycardia. The worse the ventricular function and the faster the rate, the worse the ventricular filling and output are. A VT of long duration (minutes to hours or even daysl generally leads to a further haemodynamic deterioration. The prognosis ofVT is determined by the type and severity of the underlying cardiac disease.
ECG
1
Definition and Characteristics of Ventric ular Tachycardia
Ventricular tachycardia is defined as ~ three consecutive premature ventricular complexes with a QRS duration of > 0.12 sec (often ~ 0.14 sec) and a rate between 100 to 240/min (exceptionally up to 300/min), generally 140 to 220/min. The QRS complexes are not preceded by atrial deflections. The tachycardia may be sustained (duration > 30 sec; often lasting minutes to hours) or nonsustained (duration < 30 sec; often shorter (ECG 26.1)). The repolarization is always altered, with ST elevation or depression and T inversion in some leads.
2
Types of Ventricular Tachycardia
There are three types of VT that differ in morphology, clinical significance and often in etiology.
M. Gertsch, The ECG © Springer-Verlag Berlin Heidelberg 2004
2.1
Monomorphic vr
Monomorphic VT is the most frequent type. It may be sustained or nonsustained. Sustained monomorphic VT has a rate of 130-240/min and is initiated by a ventricular premature beat (VPB). The tachycardia is regular or minimally irregular. If VT terminates spontaneously, it is followed by a 'post-tachycardia' pause (ECGs 26.2a-b), except in atrial fibrillation. Monomorphic VT generally shows a left bundle-branch- or right bundle-branch block-like QRS pattern (atypical LBBB and RBBB respectively). ECGs 26.3a-b show two episodes of VT in the same patient with LBBB pattern, ECG 26.3C shows the ECG in this patient in sinus rhythm, with a pattern of RBBB + LAFB (left anterior fascicular block) and an extensive anterior myocardial infarction (MI). ECG 26.4a is an example of VT with RBBB-like pattern (and retrograde AV block 2°), EeG 26.4b shows the QRS configuration in sinus rhythm. A VT with a rate above 200/min is called 'ventricular flutter' by some authors. Others only use the term 'ventricular flutter' if the morphology ofVT has a sinus-like form, so that depolarization and repolarization can no longer be distinguished. Atrioventricular dissociation, one or more fusion beats, capture beats or aretrograde AV block 2° (rare) indicate a ventricular origin of the tachycardia in a very high percentage of cases. ECGs 26.4a, 26.5 and 26.6 demonstrate retrograde AV block 2°. Ventricular capture beats are intermittent supraventricular beats (mostly of sinusal origin) with a narrow (normal broad) QRS com
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