Localisation of the origin of a ventricular tachycardia

Areas of the left ventricle where VT's can originate from: The left ventricle is depicted as having been opened. Regions are defined as: AA = antero-apical; AB = antero-basal; AM = mid-anterior; SA = apical septum; SB = basal-septum; SM = mid-septum; IA = inferior apex; IB = inferior-basal; IM = mid-inferior. Posterior / lateral is located on the part between anterior and inferior. Adapted from Miller et al.Miller

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:

1. What is the bundle branch block (BBB) configuration?
2. What is the inferior lead QRS complex polarity?
3. What is the lead I QRS complex polarity?
4. What is the lead aVL QRS complex polarity?
5. What is the lead aVR QRS complex polarity?
6. Where is the R-wave transition point?

Using this approach and the algorithms below segal 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.

Localising the VT exit in LBBB VT with negative QRS complexes inferior. Adapted from Segal et al.segal

Localising the VT exit in LBBB VT with positive QRS complexes inferior. Adapted from Segal et al.segal

Localising the VT exit in RBBB VT with negative QRS complexes inferior. Adapted from Segal et al.segal

Localising the VT exit in RBBB VT with positive QRS complexes inferior. Adapted from Segal et al.segal

References

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1. segal pmid=17338765
2. Miller pmid=3349580

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