Idiopathic Ventricular Tachycardia (IVT)

Related Subjects: | Classical Ventricular Tachycardia | Idiopathic Ventricular Tachycardia | Right Ventricular Outflow Tract Tachycardia | Idiopathic Fascicular Left Ventricular Tachycardia | Left Ventricular Outflow Tract Tachycardia | Ventricular Fibrillation | Resuscitation - Adult Tachycardia Algorithm | Resuscitation - Advanced Life Support | Automatic Implantable Cardioverter Defibrillator (AICD)

Idiopathic ventricular tachycardia in patients with an anatomically normal heart is a distinct entity whose management and prognosis differs from ventricular tachycardia associated with structural heart disease. Classic VT is still by far the most common cause of wide complex regular tachycardia. Assume Classical VT and all the risks associat until a Cardiologist has proven otherwise.

About

• Tacharrhythmias originating below the AV node and bundle of His
• Differ in etiology, prognosis, and treatment compared to classic VT

Aetiology

• Either automatic or reentrant in mechanism

Idiopathic VT Compared with Classic VT

• Classical VT seen in older pts with IHD and structurally abnormal hearts
• Classical VT QRS duration of 140-200 msec or greater
• Idiopathic VT: Idiopathic/fascicular VTs have QRS duration 140 ms or less.
• Idiopathic VT: May respond to Adensoine/Verapamil which must not be used in classic VT.
• Idiopathic VTs can be better understood. There are 3-4 subtypes.

Subtypes: See links above

• Right Ventricular Outflow Tract VT (RVOT VT): LBBB pattern with inferior frontal plane axis. Usually responsive to adenosine
• Fascicular Left Ventricular Tachycardia : Reentrant arrhythmia. Posterior Fascicle VT (most common by far) and Anterior Fascicle VT. PFVT RBBB + LAD. AFVT: RBBB with RAD. PFVT sensitive to verapamil.
• Left Ventricular Outflow Tract (LVOT VT) Tachycardia has RBBB
• Bundle Branch Reentrant Tachycardia (BBRVT): more often associated with underlying structural heart disease. RBBB and LBBB

Clinical

• Seen in younger, healthier patients compared with classical VT
• Severe haemodynamic compromise unusual

Investigations

• FBC, U&E, Mg, Ca, K all normal
• ECG: Normal QT. QRS tends to be narrower than classical VT.
• Echocardiogram: Normal
• CXR : normal

Classical VT is by far the most common cause of wide complex regular tachycardia, and there is no perfectly reliable way to distinguish classic VT with all its dangers from idiopathic VT or SVT with aberrancy on the surface 12-lead ECG.

Summary

Management: Treat as Classical VT unless a Cardiologist says otherwise

• ABC. If unstable have a low threshold to electrical cardioversion first and take specialist advice. Some of these respond to drugs such as Verapamil or Adenosine. Verapamil should only ever be given to a broad complex tachycardia thought to be an IVT after senior consultant/attending cardiology specialist advice and known good LV function (get echo if unsure). A normal quality echocardiogram is always reassuring and should be considered a priority.
• These arrhythmias are well tolerated usually. Needs specialist care. Only treat as IVT if there is a clear specialist diagnosis. Always be ready to DC convert.

References

• Idiopathic Ventricular Tachycardias for the EM Physician