• Idiopathic ventricular tachycardia (VT) is monomorphic VT that is not associated with structural heart disease.
• Idiopathic VT can be classified into 5 main types based on the locations in the heart it originates from:
Outflow tract VT: most common idiopathic VT, from either right or left ventricular outflow tract (RVOT or LVOT)
Fascicular VT: from either left anterior fascicle, posterior fascicle, or septal fascicle
Annular VT: from either mitral or tricuspid annulus
Intracavitary VT: from either papillary muscle or moderator band
Epicardial VT: from crux
• General rule for localizing idiopathic VT based on ECG features:
QRS morphology: RBBB ~ LV; LBBB ~ RV, septum, or aortic cusps
Axis: inferior axis ~ base, anterior, lateral; superior axis ~ posterior
Precordial transition: late ~ RV, early ~ LV, septum
R/S ratio in V6: > 1 ~ base (outflow tract, annulus); < 1 ~ mid-ventricle (papillary muscle, fascicle)
• Outflow tract VT arises from delayed afterdepolarizations (DADs) in right or left ventricular outflow tract (RVOT or LVOT).
• Anatomically,
RVOT includes pulmonary artery exit
LVOT includes aortic root, aortic cusps, aorto-mitral continuity (AMC)
• In general on ECG, there are:
Positive R waves in II, III, aVF
Deep S waves in aVR, aVL
Inferior axis
LBBB or RBBB morphology (in RVOT or LVOT, respectively)
• More common in women, age range 30-50s.
• LBBB
• Inferior axis
• Late precordial transition (unless anteroseptal origin)
• RBBB (LBBB if involving septum or aortic cusps)
• Inferior axis
• Early precordial transition
• Fascicular VT (also referred to as "idiopathic left VT", "Belhassen tachycardia", or verapamil-sensitive VT") is caused by reentry circuit involving either left posterior (most common), left anterior, or left septal fascicle.
• Since VT is conducted down the Purkinje system, QRS's are relatively narrow (< 140 ms) with RS interval < 80 ms (normally needs to be > 100 ms to meet Brugada criteria for VT). For this reason, fascicular VT can be difficult to distinguish from SVT with aberrancy
• More common in men, age range 20-40s.
• RBBB
• Left superior axis
• RBBB
• Right inferior axis
• LBBB with narrow QRS
• Normal or right axis
• Annular VT arises from either mitral or tricuspid annulus.
• ECG shows typical VT features but with broad R in V1 and rightward or inferior axis (around 90 degree).
• More common in men, age range 50-70s.
• RBBB (or monophasic R's) with positive concordance in V2-6
• Pseudo-delta wave (~ WPW)
• Early precordial transition
• Inferior axis if anterolateral origin
• Superior axis if posteromedial origin
• LBBB
• Early precordial transition, inferior axis if septal origin
• Late precordial transition if free-wall origin
• Intracavitary VT arises from either papillary muscle or moderator band.
• More common in men, age range 40-70s.
• RBBB if from LV, LBBB if from RV
• QRS > 150 ms
• Right inferior axis, early precordial transition (< V1) if anterolateral origin
• Left superior axis if posteromedial origin
• LBBB
• Narrower QRS
• Left superior axis
• Late precordial transition
• Discordant inferior leads (+II/-III)
• Epicardial VT originates from:
Crux: at the junction of atrioventricular groove & posterior interventricular groove, also junction of middle cardiac vein (MCV) & coronary sinus (CS), near the origin of PDA
LV summit: at the junction of anterior interventricular vein (AIV) & great cardiac vein (GCV), also bounded by LAD & LCx
• Epicardial VT takes longer to reach to subendocardium, where Purkinje network is located, and propagates from LV free (lateral) wall or posterior wall to medial or superior wall, respectively. As a result, on ECG:
QRS > 200 ms
R wave peak time (RWPT) > 85 ms
MDI (RWPT/QRS) > 0.54
Pseudo-delta wave > 34 ms
RS > 121 ms
QS pattern in I or aVF
• LBBB
• Left superior axis
• Early precordial transition
• LBBB
• Inferior axis
• Early precordial transition