In this chapter we will be primarily interested in the identification of catastrophic, gross valve failure or dysfunction that is severe enough to impact patient hemodynamics. This is the primary goal of the focused cardiac ultrasound (FoCUS) assessment and heavily relies on 2D ultrasound technology. A comprehensive evaluation of the valves involves color flow doppler (CFD), pulsed wave doppler (PWD) and continuous wave doppler (CWD) which are out of the scope of FoCUS but that we will briefly touch base. It is through these other techniques that we can have a better and more precise assessment of the different degrees of valve dysfunction.
Aortic Valve Anatomy and Function Recap
The aortic valve has 3 cusps: left coronary, right coronary and the non-coronary cusp. The valve opens and closes due to changes in pressure between the ventricle and the aorta. On systole, the intraventricular pressure rises above the aortic pressure causing the aortic valve to open and blood moves forward into the aorta. Once the pressure of the left ventricle is lower than that of the aorta, the aortic valve closes.
Aortic valve with normal function. 1, The clip above was taken from the aortic root in a living, beating pig heart. 2, still image of the aortic valve at maximal leaflet displacement. 3, still image of the aortic valve on diastole. Notice the very tight coaptation points which prevents flow from moving back into the ventricle. Clips modified from Valguru with permission.
As you can appreciate, the aortic valve cusps move in 3 dimensions as they open up towards the aortic root. This makes the evaluation under ultrasound challenging since we are only able to observe two dimensional sections. A comprehensive evaluation of the valve entails an analysis of the flows (with pulsed and continuous wave doppler) on multiple cardiac windows that go above and beyond the scope of the focused cardiac exam but will be mentioned in this section. Luckily for us our job is to determine extremes: Is the aortic valve stenotic or insufficient enough that I can detect it with ultrasound?
Aortic Valve Stenosis
Aortic stenosis is very common in the elderly population. When it is present, it complicates hemodynamic management of patients with septic shock.
On ultrasound we typically observe a hyperechoic and heavily calcified valve with significant reduction of movement. The diagrams display the movement of the valve on systole without and with stenosis as they would be seen on the parasternal long axis view.
Normal valve vs aortic valve stenosis schematic in systole. In 1 we observe normal displacement of the aortic valve cusps. In 2, we see heavily calcified cusps with severe severe flow restriction.
Parasternal Long Axis
We can appreciate the restriction of movement of the aortic valve when seen on the parasternal long axis.