There is dissociation between atrial and ventricular activity. The rapid rate and A-V dissociation may lead to reduced cardiac filling and low cardiac output, hypotension, and cardiac arrest.
Many toxic substances cause ventricular tachycardia.
Individuals with underling ischaemic heart disease are special risk. The clinical features of ventricular tachycardia vary across a wide spectrum according to the cardiac output and end-organ perfusion. The features of cardiorespiratory arrest may be observed, or the patient may be in shock with hypotension, diaphoresis, confusion or syncope. Occasionally, especially in young otherwise healthy individuals, the patient may be virtually asymptomatic. In the case of atypical VT, patients may present with abrupt onset of episodic dizziness, weakness, or syncope.