Ventricular Tachycardia – Classification

Ventricular Tachycardia – Classification

Ventricular tachycardia is a common arrhythmia. The manifestations include mild symptoms of palpitation to sudden death. In next few blog posts, we will try to understand the basics of ventricular tachycardia/fibrillation and we will discuss management of these arrhythmias.


Ventricular arrhythmias are defined as arrhythmias that originate below the bifurcation of His bundle, in the specialized conduction system, the ventricular muscle, or in combination of both tissues.


Ventricular Tachycardia ECG

(Image created by Karthik Sheka, M.D. [CC BY-SA 2.5 (], via Wikimedia Commons)

There are different classifications of ventricular arrhythmias, according to their duration, morphology of QRS complexes, and clinical characteristics.

Classification According to Duration

(1) Premature ventricular complexes (PVC): isolated complexes originating from the His-Purkinje system or ventricular myocardium.
(2) VT: 3 or more consecutive QRS complexes at a rate greater than 100 beats per minute.
(3) Nonsustained VT: VT that terminates spontaneously within 30 seconds.
(4) Sustained VT: continuous VT lasting for ≥30 seconds or that requires an intervention for termination (such as cardioversion).

Classification According to Morphology of QRS Complexes

(1) Monomorphic VT: VT that has a similar QRS configuration from beat to beat. Some variability in QRS morphology at initiation is not uncommon.
(2) Multiple monomorphic VT: more than one morphologically distinct monomorphic VT, occurring as different episodes or induced at different times.
(3) Polymorphic VT: VT that has a continuously changing QRS configuration indicating a changing ventricular activation sequence.
(4) Pleomorphic VT: VT that has more than one morphologically distinct QRS complex occurring during the same episode of VT, but the QRS is not continuously changing.
(5) Ventricular flutter: rapid VT that has a sinusoidal QRS configuration that prevents identification of the QRS morphology.
(6) VF: ventricular tachyarrhythmia that has a totally chaotic

Classification According to Clinical Characteristics

(1) Clinical VT: VT that has occurred spontaneously based on analysis of 12-lead ECG QRS morphology and rate.
(2) Hemodynamically unstable VT: VT that causes hemodynamic compromise requiring prompt termination.
(3) Incessant VT: continuous sustained VT that recurs immediately despite repeated spontaneous or therapeutic termination.
(4) Repetitive monomorphic VT: continuously repeating episodes of self-terminating nonsustained VT.
(5) VT storm: 3 or more separate episodes of sustained VT within 24 hours, each requiring termination by an intervention.
(6) Unmappable VT: VT that does not allow interrogation of multiple sites to define the activation sequence or perform entrainment mapping. It may be due to hemodynamic
intolerance that necessitates immediate VT termination, spontaneous, or pacing-induced transition to other morphologies of VT, or repeated termination during mapping.

In the next post, we will discuss clinical features and ECG features.


Arrhythmia or Disorders of Heart Rhythm

Arrhythmias or disorders of heart rhythm are a group of diseases characterized by abnormality of heart beat. Our heart is expected to beat in a certain way. In an adult individual the heart normally beats 60 t0 100 times per minute, in a regular manner (that means a nearly constant interval between two beats ). There are some normal variations, like in children the heart beat is faster, in some healthy persons and trained athelets the heart beat can be slower, during sleep the heart beat is normally slower.

Definition of Arrhythmia:

Arrhythmia is defined as any deviation from this normal pattern of heart beat.

What are the types of Arrhythmia?

Heart rhythm disorders are basically of two types. When the Heart rate is abnormally high it is called TACHYCARDIA. When the heart rate is abnormally slow it is called BRADYCARDIA. There can be irregular heart beats even if the heart rate is between 60-100, those cases are also Arrhythmic.

What is the relation of arrhythmias to other heart diseases?

Arrhythmias can be divided into two types based on heart diseases

  1. Arrhythmias occurring in persons having no underlying structural heart disease are called- IDIOPATHIC ARRHYTHIMAS
  2. Arrhythmia also arise in persons who have underlying structural heart diseases.

What are the symptoms of Arrhythmia?

Arrhythmias due to slow heart rate (Bradycardia) commonly cause

  1. Lethargy
  2. Fatigue
  3. Palpitation
  4. Light headedness
  5. Syncope (Transient loss of consciousness followed by full recovery)
  6. Sudden death

Arrhythmias due to fast heart rate (Tachycardia) commonly produce symptoms of

  1. Palpitation
  2. Faintness and light headedness
  3. Syncope (Transient loss of consciousness followed by full recovery)
  4. Sudden death
  5. Reduced pumping capacity of heart and related symptoms
  6. Some arrhythmias like atrial fibrillation can produce abnormal clotting of blood inside heart which can migrate to brain to cause stroke and paralysis.

How serious are Arrhythmias?

Some arrhythmias are benign and non life threatening, but they cause troublesome symptoms of palpitation and skipped beats.

Some arrhythmias are life threatening and can cause even sudden death. It all depends on the origin and type of arrhythmias and any other underlying heart disease.

How to diagnose arrhythmia?

Arrhythmias are commonly diagnosed by

  • ECG
  • Holter monitoring
  • Sometimes long term monitoring like – event recorders, loop recorders etc.
  • In some case Cardiac Electrophysiological study is required to diagnose a rhythm disorder.

What are the treatments available?

  1. Some transient arrhythmias terminate on their own and don’t need any specific therapy
  2. Underlying cause needs to be treated like- drugs, electrolyte disturbances, etc
  3. Medicines are usually the first line treatment
  4. Catheter Ablation: It is a procedure done in cardiac cathlab where an arrhythmia is ablated commonly by application of radiofrequency energy inside the heart. It is a safe procedure with prospect for complete cure of the arrhythmia.