diagnosis
Last reviewed 01/2018
It may be difficult to distinguish the following disorders:
- ventricular tachycardia
- SVT with aberrant ventricular conduction (fixed or rate related)
Distinguishing features include:
- in SVT, and not in VT, P waves are associated with specific QRS complexes, i.e. ventricular contraction is preceeded by atrial contraction
- in SVT-with-aberrant-conduction, the QRS complex shows left bundle branch or right bundle branch block, i.e. an M pattern in V6 or V1 respectively
- an SVT maintains the same QRS complex seen in sinus rhythm
- an SVT maintains the cardiac axis seen in sinus rhythm whereas VT often has left axis deviation
- fusion or capture beats on the ECG are characteristic of VT
- a broad complex tachycardia is likely to be ventricular in origin if the QRS duration is greater than 140 ms
Reference:
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(1) Hampton J. Interpreting the ECG. Medicine International (1993), 21, 318-24.