Embedded Files
Idiopathic VT is one of the most misdiagnosed rhythms as it typically occurs in young, relatively healthy patients. It is a reentrant tachycardia that originates in the RVOT or fascicles (RVOT VT and fascicular VT) and is usually precipitated by catecholamine surges (ie exercise, infection). It is called idiopathic as it is a monomorphic VT that occurs in the absence of structural heart disease (10% of all cases of VT). It occurs almost exclusively in structurally normal hearts, though RVOT VT also occurs in patients with arrhythmogenic right ventricular cardiomyopathy. RVOT VT accounts for 70% of cases of idiopathic VT. Although they are VT with a wide complex tachycardia, the QRS complexes do not tend to be quite as wide (usually 120ms) as VT from structural heart disease and have quicker initial velocities (ie shorter RS interval) than traditional VT.
RVOT VT has a LBBB-like morphology with an inferior axis as it originates in the RV outflow tract (superior and right-sided, so conduction towards inferior and left directions). It is sometimes resolved with adenosine.
Fascicular VT is the most common idiopathic VT of the left ventricle. It will have a RBBB-like morphology as it originates in one of the fascicles of the left ventricle (depolarization from left to right). There are multiple classifications of fascicular VT, depending on the specific fascicle that initiates the arrhythmia: posterior, anterior, and septal. Posterior fascicular VT accounts for the majority of cases of fascicular VT and produces a RBBB-like morphology with left axis deviation (appearance somewhat similar to left anterior fascicular block as it travels from posterior to anterior). Anterior fascicular VT produces a RBBB-like morphology with right axis deviation (appearance somewhat similar to left posterior fascicular block). Septal fascicular VT is very rare and may have a varied and atypical morphology, though usually is still RBBB-like. Fascicular VT is typically responsive to verapamil.
Source: LITFL
Posterior fascicular VT with a RBBB-like morphology and left axis deviation. The capture beat makes this much more easy to diagnose as VT as opposed to SVT with a bifascicular block (RBBB and LPFB).
Source: LITFL
Anterior fascicular VT with a RBBB-like morphology and right axis deviation. This would be very easy to misdiagnose as SVT with aberrancy, though there are subtle clues to this being VT (ie taller left rabbit ear, S>R in V6).
Page updated
Google Sites
Report abuse