In this article, we will discuss the Definition and Clinical Features of Ventricular Tachycardia. So, let’s get started.
It is a wide QRS (>0.12 sec) tachycardia consisting of 3 or more consecutive ventricular premature beats at a rate of >100 bpm. The sudden onset of a wide QRS tachycardia usually rings an alarm bell if the patient is symptomatic. If left untreated, VT may degenerate into fatal ventricular flutter. VT may be sustained (persists for >30 seconds) or nonsustained (does not persist beyond 30 seconds). The sustained VT requires termination because of hemodynamic consequences. Repeated episodes (>2 in 24 hours) of VT require external cardioversion/defibrillation or DC shock therapy.
Sustained VT occurs in association with a cardiac disease; while nonsustained VT can occur in the absence of heart disease. Sustained VT is almost always symptomatic; while nonsustained VT (3 VPCs in a row or VT lasting for <30 seconds) does not produce symptoms (asymptomatic). Sustained monomorphic VT is commonly encountered in patients with chronic or old myocardial infarction. A fixed anatomical lesion producing ischemia is responsible for recurrent sustained monomorphic VT.
The symptomatic patients of sustained VT present with palpitations, dizziness, syncope or even cardiac arrest. The presence of cannon waves, changing intensity of first heart sound with rapid ventricular rate suggest AV dissociation and favour the diagnosis of VT. A history of previous infarction and first episode of tachycardia after infarction is highly suggestive of VT; while long history of tachycardia with frequent attacks, absence of organic heart disease and presence of pre-excitation suggest PSVT with aberrant conduction.