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QRS - Ventricular depolarization
QRS - Ventricular depolarization
If the QRS is narrow
The signal came from up top
If the QRS is wide (> 2-3 small boxes)
The signal came from below
Or aberrancy (something below messed with the signal)
Aberrant Conduction (diverging from the normal)
Picture the signal from SA node makes it to AV node
But damage to the heart limits the fast acting conduction system (bundle branches, Purkinje fibers)
Instead, depolarization slowly occurs from one myocyte to another
This slower depolarization β wider QRS
Premature ventricular contraction (PVC)
Premature ventricular contraction (PVC)
An ectopic focus depolarizes early that conducts to the rest of the ventricle β premature contraction
Can be from normal or from damage, medications, hypoxia (to name a few)
Some say a triplet is a short run of V-tach
V-tach
V-tach
This is V-tach (a sustained monomorphic V-tach)
This PT gets lidocaine or amiodarone if stable
Not stable: π¨βπ (Synchronized if alive)
Accelerated Idioventricular rhythm
Accelerated Idioventricular rhythm
Regular at rate of 50-110 with > 3 ventricular beats (wide QRS)
Ectopic ventricular foci takes over rate
Usually benign, but if hypotensive you would give atropine
Hopefully kicks up SA enough to get some AV conduction
Polymorphic V-tach (Torsades de pointes)
Polymorphic V-tach (Torsades de pointes)
When the QT is prolonged (hypomag, hypoK, meds) β β risk of R on T
Depolarization during the relative refractory period can bring on Torsades
TX with MgSO4
Ventricular Hypertrophy
Ventricular Hypertrophy
Remember the way V1 & V6 "look" at the heart
The positive wave of depolarization is heading toward the LV
V6 has a more positive inflection
V1 more negative deflection
Normal V1 & V6 QRS
When the vector (yellow arrow) changes β EKG changes
Left ventricular hypertrophy β more negative in V1, more positive in V6
More of the vector is going away from V1 and toward V6
Right ventricular hypertrophy β more positive in V1, less positive in V6
Less of the vector is going toward V6
Causes of hypertrophy
Causes of hypertrophy
LVH: HTN, aortic stenosis β β afterload; regurgitation β β volume to pump out
RVH: Chronic lung DZ (COPD), pulmonary HTN, pulmonary stenosis β RV pumping against resistance
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