Under normal conditions, the left ventricle is larger than the right ventricle, because it carries more of a workload (thanks to afterload) than the right ventricle. If you go to the gym everyday and curl a 35 pound weight with your left arm and a 10 pound weight with your right arm, your left arm is obviously going to be larger than the right. In LVH, your left arm is curling a 55 pound weight.
Left Ventricular Hypertrophy (LVH) can have numerous causes. Any illness, injury or disease that causes the left ventricle to work harder than normal will eventually lead to an enlarged left ventricle over a lengthened period of time.
The most common cause is hypertension, as this leads to increased afterload (the pressure which the ventricle must pump against). Fortunately, hypertension is treatable/manageable in most cases (hypertension essential, hypertension secondary). Some other causes are aortic stenosis, cardiomyopathy, aortic regurgitation, mitral regurgitation, and coarctation of the aorta.
Why do we care to identify LVH? Similar to Bundle Branch Blocks (another blog idea...) LVH is an imitator. It can hide or mimic ST elevation, ST depression, hyperacute T waves or inverted T waves.
LVH can be identified on a 12 lead EKG (not on a 4 lead). To do this, we need to follow 3 simple steps:
Step 1:
◦Look in leads V1 and V2
◦Pick the deepest negative QRS deflection
◦Count small boxes of negative deflection in that lead
◦Remember that number
In this picture, it's difficult to tell where the QRS in V2 stops because it runs overtop of the QRS in V3, however, I'd estimate there to be about 55mm of negative deflection.
Step 2:
◦Look in V5 and V6
◦Pick the tallest positive deflection
◦Count small boxes of positive deflection
◦Remember that number
Back to the picture, the tallest positive deflection is in V5, with about 15mm of deflection.
Step 3:
◦Add the two numbers together
◦Suspect LVH if the sum equals 35 or more
In our example, the sum of these two numbers equals 70mm, which is significantly higher than 35mm. Therefore, it's safe to say that this patient has LVH (significant LVH).
Want to learn more about EKG interpretation? Check out our Paramedic Cardiology Study Guide or our EKG/ACLS Study Guide!