Why is absent RS complex in precardial leads is very sacred to diagnose VT ?
Posted Sep 17 2009 10:21pm
The most popular criteria to differentiate VT from SVT aberrancy is formulated by Brugada in 1991.
The greatness of that criteria is that a single question asked is able to confirm VT in vast majority of cases.
Is RS complex absent all of the pericardial leads ?If the answer is yes it is VT 100%
How is that, we have been struggling for so long , a single question is able to solve the issue quite easily ?
This is because , the term “Absent RS complex ” actually means
Presence of one of the following three typical complexes Of VT.
Two of them actually imply , q waves throughout V 1-V6 .This means a badly damaged ventricle and with little electrical activity coming towards the chest wall .This situation almost always occur in VT.*
The third complex is Monophasic R .
A monophasic , wide QRS complex again indicate VT as monophasic aberrancy is very rare as the supraventricular impulse invariably conducts with RSr’ ( The right bundle refractory period sees to that at least a small r’ is inscribed however fast the SVT is ! )
So if there is no RS complex it must be VT !
What is the most important difficulty faced in applying this first
step of Brugada criteria ?
It is funny to note , in medicine criterias often work perfectly in text books only !
Is there a RS complex seems to be a very easy question ? There lies the catch ! .Eventhough this criteria may be 100% specific , differentiating RS from QS complex even by an experienced cardiologist may be difficult in a significant number of VT tracings.This realistically , reduces supposedly 100% specificity of this criteria !
In fact we expect Brugada to develop an another limb to his now famous algorithm
Is there absence RS complex in precardial leads ? Yes / No / May be , not sure!