Ventricular tachycardias

What is Ventricular Tachycardia (VT) ?
They are a particular goup of tachyarrhythmias originating from the ventricles.


What And How To Recognize?
Ventricular Tachycardias can be classified into:
monomorphic ventricular tachycardia: on the ECG every beats have an identic morphology;
polymorphic ventricular tachycardia: on ECG the beats of tachycardia have multiple morphologies;
sustained ventricular tachycardia: when the tachycardia last more than 30 second; in this case it should be stopped immediately because it causes syncope or dizziness and is not tolerated by the patient;
non-sustained ventricular tachycardia: less than 30 beats;
Tolerated ventricular tachycardia : the patient complains only palpitations, but don’t loose consciousness;
Not tolerated ventricular tachycardia: the patient starts to complain palpitations, extreme weakness, and then quickly loses consciousness. In some cases loss of consciousness is immediate.
The patient’s ability to tolerate the tachycardia without fainting or without feeling shortness of breath (haemodynamic tolerance) depends on two factors: the heart rate during tachycardia and left ventricular function.

Why VT occur?
It may be caused by a re-entry circuit that allows to a single electrical impulse to continue indefinitely to reactivate ventricles. This circuit can be due to unknown causes (idiopathic) or known diseases such as myocardial infarction. 
More rarely VT origin from ventricular foci that generate their own electrical impulses accelerated. The idiopathic forms may arise from the right ventricle or the left ventricle and could be related to the intra-ventricular conduction system (Fascicular VT). 
A common cause of ventricular tachycardia is the presence of a previous heart attack. In this case the circuit is determined by the infarct scar and the tachycardia is almost invariably located in the left ventricle. In the right ventricle sometimes are present areas where the muscle is replaced by fat or fibrous tissue creating an arrhythmogenic substrate. This is the case of Arrhythmogenic Right Ventricular Dysplasia.
A particular form of VT is the “torsades de pointes”. This tachycardia is usually associated with an EKG anomaly called “long QT”. This anomaly may be congenital, but it’s often caused by frequent use medications.

How to treat?
The possible treatments include anti-arrhythmic drugs, catheter ablation and / or, when the risk is higher, implantation of the ICD.