An accurate assessment of diastolic function can be both diagnostic and prognostic. Diastolic dysfunction often precedes systolic dysfunction or even clinical signs of heart disease, and the degree of diastolic dysfunction present can inform prognosis and treatment in not only heart failure patients but diseases as diverse as hypertrophic cardiomyopathy (HCM), aortic stenosis and primary mitral regurgitation.
To perform an assessment of diastolic function with ultrasound, your machine requires:
- Pulsed Wave (PW) Doppler
- Tissue Doppler Imaging (TDI) – although, with manual adjustment of the wall filters and PRF/scale, you can create your own TDI setting
Ideally, this would be performed with a phased array probe.
From the 4 chamber view, place your PW Doppler sample gate at the tips of the mitral valve to obtain a mitral inflow trace:
In young and healthy humans, dogs and cats, the E wave – the early filling component, created by left ventricular suction – will be taller than the A wave. The second wave, the A wave, is a result of atrial contraction, and should be smaller. As humans and dogs age, the A wave becomes more prominent, as relaxation of the left ventricle is impaired and a greater portion of diastolic filling is dependent upon atrial contraction. Age-related changes have not been seen in cats, although hypertrophic cardiomyopathy (HCM) is prevalent in felines and is always associated with diastolic dysfunction.
It is important to obtain supporting measures. The E wave deceleration time is also useful – in the first stages of diastolic dysfunction, relaxation of the left ventricle will be delayed, causing a longer deceleration time. In advanced diastolic dysfunction, charactertised by a restrictive filling pattern, the deceleration time will be very short because the E wave is in fact a result of extremely high left atrial pressures – not of suction from the left ventricle.
Looking at the overall clinical picture will guide you, and naturally make you suspicious of a ‘normal’ inflow pattern if it doesn’t fit with the symptoms, age, or 2D imaging. A dilated left atrium and/or concentric left ventricular hypertrophy, for example, will always be associated with some degree of diastolic dysfunction.
A comprehensive assessment of diastolic function is difficult in patients with atrial fibrillation (no A wave), or very fast heart rates (E and A waves begin to merge. In stressed felines or tachycardic humans, there is often no clear separation between the E and A waves at all).
Tissue Doppler Imaging (TDI)
Tissue Doppler Imaging (TDI) looks at the excursion of the myocardium, as opposed to the velocity of blood flow. Again, in young and healthy humans and animals, E’ (“E prime”) will be taller than A’ (“A prime”).
As the left ventricle stiffens, E’ velocities reduce. The E/E’ ratio is key in confirming a ‘pseudonormal’ or grade II diastolic filling pattern, because the E/A ratio and deceleration time will be normal (although, as mentioned above, they will likely not fit with the clinical picture or even the 2D imaging, immediately raising your suspicions), but the lower E’ velocities will highlight the fact that left atrial pressures are in fact elevated.
The E/E’ ratio is also elevated in more severe stages of diastolic dysfunction – restrictive filling, as discussed above.
In the video below, David Dawson from Imperial College London talks you through how to obtain the perfect mitral inflow, septal TDI and lateral wall TDI using the Siui Apogee 2300. If you would like a demonstration or training session on how this machine can help you, or simply how to get more from your existing machine, please get in touch today.