The Empty Heart
Do you remember the last case I presented in the post titled "Tractor vs. Motorcycle"? The fellow who had a motorcycle accident with blunt chest trauma and traumatic tricuspid valve rupture?
An unusual additional finding in this patient was that his left ventricular function was also poor - something one wouldn't expect in a right heart pathology. Thanks for your many suggestions and comments to this case. In today’s post I want to give you my interpretation of this finding. Here is his short-axis view again to remind you of how poor the patient's left ventricular function was.
Parasternal short-axis view of our patient with tricuspid
Certainly there is an interaction between the left and the right ventricle. First: severe tricuspid regurgitation led to volume overload of the right ventricle and abnormal septal motion. This alone may cause left ventricular function to look poor. In addition, the fibers of the right ventricle also extend to the left, especially the septum. This might have been a contributing factor. However, I believe his left ventricular dysfunction was caused by something quite different.
Principles of hemodynamics
We need to look at the outflow velocities of the left and right ventricles:
Pulsed-wave Doppler across the RVOT.
The velocity is very low: a mere 0.3 m/s. Normally one would expect velocities in excess of 0.8-1 m/sec. The velocity time integral, which corresponds to stroke volume, is also extremely low (4.1 cm). Why is this so? Simply because most of the blood that is pumped out of the right ventricle is going the other way - back into the right atrium. What does this have to do with the left ventricle? The explanation can be found by studying flow across the LVOT.
Pulsed-wave Doppler across the left ventricular outflow tract.
The underfilled left ventricle
Flow across the LVOT is also extremely low (0.6m/s with a VTI of only 6cm). His stroke volume was just 35-40 ml. Obviously, if only a small quantity of blood leaves the right ventricle, only a small quantity of blood will reach the left side of the heart. The left ventricle is simply "underfilled". Remember: preload also affects left ventricular function. This is the main reason why left ventricular function is poor. Very little blood is available for pumping. No wonder the patient has symptoms.
To support our theory, here is the follow-up study after successful tricuspid valve repair had been performed:
Post operative study (four-chamber view).
What a difference to the preoperative study. He now has mild to moderate residual triscuspid regurgitation. After just 10 days, the size of the right ventricle returned to normal.
What about left ventricular function?
Has his left ventricular function changed? Compare this short-axis view with the one above:
Short-axis view of the left ventricle after surgery.
What a difference! Not only is the motion of the septum now normal, but his left ventricular function has also returned to normal. To prove that his initial problem was the “underfilled left ventricle,” here is the flow velocity tracing across the outflow tract for the left as well as the right ventricle.
PW Doppler across the RVOT.
PW Doppler across the LVOT.
Now, significant tricuspid regurgitation has disappeared and velocities have also returned to normal. Both, RVOT and LVOT are above 1 n/sec and VTI is in the range of 20 cm. The left ventricle now has enough blood to pump. Therefore, function is improved.
What does all this tell us? It is important to understand the hemodynamics of the heart. The heart can adapt and change its appearance according to hemodynamics - just the way a chameleon changes its color to merge with its surroundings.
On a final note: we were very glad to have been able to help our patient. He is doing fine and will reward himself for the all his suffering with a new motorcycle.
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yours Tommy & the 123sonography team