Ventricular tachycardia | Broad complex SVT | |
---|---|---|
* In some ventricular tachycardias that originate from the conduction pathways the morphology of the QRS complexes may resemble that of typical bundle branch block | ||
History and clinical findings | Elderly patient Heart disease (myocardial infarction, cardiac insufficiency) | Young patient Structurally a healthy heart |
QRS duration and axis | Usually > 160 ms Abnormal frontal plane axis (over -45°) The QRS direction in all the precordial leads is consistent (concordance). | Usually 120-140 ms Normal frontal plane axis or slight left axis deviation No QRS concordance |
QRS shape | Changes according to the arrhythmia mechanism (differs from typical bundle branch block*) Fusion beats (intermediate between a normal beat and a VT beat). Capture beats, resembling normal QRS complexes, among the VT | Typical RBBB or LBBB |
Other ECG features | VA dissociation is diagnostic for VT, but is missing in about half the cases. |