Ultrasound Case #10 – The Pointy Outflow
The patient is a 64 year old female with a PMH of DM1, ESRD on HD, Aflutter on Eliquis who presented with altered mental status. Per husband, patient this morning was confused and “slumped over” on her right side. She is normally forgetful at baseline, but was fully conversant and acting normally the prior night. No complaints the prior few days.
On exam, she was hypoxic in the 80s and placed on 6L NC with improvement. She was disoriented, not conversing. No new focal neurological changes. You perform bedside ultrasound and obtain images below.
You perform a POCUS, what do you see?
What do you see in these images and what is your next step in management?
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The first image is a parasternal long that shows hyperdynamic ejection fraction, seen again in the second image showing a parasternal short axis. It also shows concentric wall thickness that was noted on prior ECHO. The 3rd and 4th image shows a dagger like velocity, suggesting dynamic LVOT obstruction. The 5th image then shows a color flow doppler with blood filling the entire outflow tract at the level of the aortic vavle. This finding specifically supports the thought the patient likely has sub valvular aortic outflow tract obstruction. Given the concentric thickening of the ventricular tissues, it is likely that the patient shows a dynamic obstructive pattern similar to HOCM.
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After seeing the concentric wall thickening in the first and second image. We measured LVOT VTI, left ventricle outflow tract velocity time integral, which is used as a surrogate for cardiac output. It is measured in the apical 5 chamber view, by using pulse wave doppler. While measuring LVOT VTI we noticed aliasing at the baseline. This happens when the velocity that is being measured is too high, so the peaks are carried over to the bottom of the window. Due to this, we switched to continuous wave doppler, where we note the peak velocity is greater than 2.
When looking closer at the tracings, we noticed concern for LVOT obstruction. In dynamic LVOT obstruction, the tracing shows slowly consistent velocity until there is a sudden rapid increase in velocity with a peak at late systole, creating a dagger like shape of the velocity curve, see below. The velocity suddenly increases once the ventricular size reaches a point where the septal wall enters the LVOT. This is commonly seen in pathologies such as HOCM. In contrast to a fixed obstruction that would start during early systole and continue throughout the ejection period, showing a peak in early-mid systole giving an envelope shape.
Note that in the color flow video, with each contraction there is color flow filling the entire aortic outflow tract and the narrowing is before the valve. There is also color aliasing of the yellow and teals.
When patients in shock remain tachycardia and hypotensive despite adequate fluid resuscitation dynamic LVOT obstruction should be on your list of things to look for. Once identified, if you confirm adequate fluid resuscitation either with ultrasound or more invasive devices, then slowing down the heart is likely the next best step. A lower heart rate will allow more time for ventricular filling, therefore increasing pre-load and afterload. This will keep increase the chamber size of the ventricle in late systole and reduce or resolve the dynamic obstruction. Esmolol is a beta 1-blocker and is a good choice in these scenarios. Esmolol has a fast on and fast off time so if you are wrong and the patient’s condition worsens after administration of esmolol, it is easy to reverse course.
Works Cited:
-Admin. 1.8.1.1 Pulsed Wave Doppler (PW-Doppler). 123 Sonography. https://www.123sonography.com/content/1811-pulsed-wave-doppler-pw-doppler. Published February 28, 2019. Accessed May 30, 2021.
-Echo-Guided Esmolol Administration in Septic Patient. https://www.coreultrasound.com/terren_esmolol/. Accessed May 30, 2021.
-Hong JH, Schaff HV, Nishimura RA. Fixed versus dynamic subaortic stenosis: Hemodynamics and resulting differences in Doppler echocardiography and aortic pressure contour. The Journal of Thoracic and Cardiovascular Surgery. 2015;151(3):883-884. doi:10.1016/j.jtcvs.2015.10.082