Differentiate between VT and SVT

Advanced Tips for Diagnosing VT — The Brugada Criteria For difficult cases, the Brugada algorithm can be used to distinguish between VT and SVT with aberrancy. The algorithm is followed from top to bottom — if any of the criteria are satisfied then VT is diagnosed. 1. Absence of an RS complex in all precordial leads This is essentially the same as having positive or negative concordance. All precordial leads consist of either monophasic R or S waves → VT is diagnosed. If there are any RS complexes present in V1-6 → go to step 2. Precordial R waves only → VT Precordial S waves only → VT RS complexes present → go to step 2 2. RS interval > 100ms in one precordial lead If RS complexes are present in V1-6 then the RS interval is measured. This is the time from the onset of the R wave to the nadir of the S wave. If the RS interval is > 100 ms → VT. If the RS interval is < 100 ms → go to step 3 3. AV dissociation The ECG is scrutinised for hidden P waves; these are often superimposed on the QRS complexes and may be difficult to see. P waves are present at a different rate to the QRS complexes → AV dissociation is present and VT is diagnosed. No evidence of AV dissociation can be seen → go to step 4 4. Morphological Criteria for VT Leads V1-2 and V6 are assessed for characteristic features of VT. There are two sets of morphological criteria depending on the appearance of the QRS complex in V1: Dominant R wave in V1 → see criteria for RBBB-like morphology Dominant S wave in V1 → see criteria for LBBB-like morphology