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The localisation of the origin (or exit site) of a ventricular tachycardia can be helpful in understanding the cause of the VT and is very helpful when planning an ablation procedure to treat a ventricular tachycardia. | The localisation of the origin (or exit site) of a ventricular tachycardia can be helpful in understanding the cause of the VT and is very helpful when planning an ablation procedure to treat a ventricular tachycardia. | ||
The steps to finding the exit site are: | |||
# What is the bundle branch block (BBB) configuration? | |||
# What is the inferior lead QRS complex polarity? | |||
# What is the lead I QRS complex polarity? | |||
# What is the lead aVL QRS complex polarity? | |||
# What is the lead aVR QRS complex polarity? | |||
# Where is the R-wave transition point? | |||
Using this approach and the algorithms below <cite>segal</cite> the exit site can be estimated with reasonable accuracy (PPV around 70%). In these algorhythms, bundle branch block was defined as “left” or “right” based on QRS morphology in lead V1; right bundle branch block (RBBB) pattern was defined by a mono-, bi-, or triphasic R wave or qR in V1; LBBB pattern was defined by a QS, rS, or qrS in V1. | Using this approach and the algorithms below <cite>segal</cite> the exit site can be estimated with reasonable accuracy (PPV around 70%). In these algorhythms, bundle branch block was defined as “left” or “right” based on QRS morphology in lead V1; right bundle branch block (RBBB) pattern was defined by a mono-, bi-, or triphasic R wave or qR in V1; LBBB pattern was defined by a QS, rS, or qrS in V1. | ||
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[[File:LBBB_VT_i.svg|thumb|left|300px|Localising the VT exit in LBBB VT with negative QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | [[File:LBBB_VT_i.svg|thumb|left|300px|Localising the VT exit in LBBB VT with negative QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | ||
[[File:LBBB_VT_p.svg|thumb|none|300px|Localising the VT exit in LBBB VT with positive QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | [[File:LBBB_VT_p.svg|thumb|none|300px|Localising the VT exit in LBBB VT with positive QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | ||
[[File:RBBB_VT.svg|thumb|300px|left|Localising the VT exit in RBBB VT with | [[File:RBBB_VT.svg|thumb|300px|left|Localising the VT exit in RBBB VT with negative QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | ||
[[File:RBBB_VT2.svg|thumb|300px|none|Localising the VT exit in RBBB VT with | [[File:RBBB_VT2.svg|thumb|300px|none|Localising the VT exit in RBBB VT with positive QRS complexes inferior. Adapted from Segal et al.<cite>segal</cite>]] | ||
==References== | ==References== | ||
<biblio> | <biblio> |