LVIDDN calculator
Enter LVIDd and body weight to get the normalised diameter, add LA and Ao for the ratio, then copy the summary.
For educational purposes only. This is not veterinary advice and does not replace clinical judgment. Check every result against the source guideline.
Left ventricular internal diameter in diastole, M-mode from the right parasternal short axis.
Right parasternal short-axis view, early diastole. Any unit, the same as the aorta. Do not use long-axis measurements: their cutoff is different.
Enter LVIDd and body weight to see LVIDDN.
The calculator runs in your browser, and the numbers you enter are never sent anywhere.
The formula
LVIDDN = LVIDd (cm) / body weight (kg) ^ 0.294
The 2019 ACVIM consensus prints this equation, and the EPIC trial used it to select dogs with cardiomegaly. The 1.7 figure is a staging criterion, not a healthy reference interval.
Common questions
- How do you calculate LVIDDN?
- Divide the left ventricular internal diameter in diastole, in cm, by body weight in kg raised to the power 0.294. A dog with an LVIDd of 3.5 cm weighing 10 kg has an LVIDDN of about 1.78.
- What LVIDDN suggests left ventricular enlargement?
- The EPIC trial and the 2019 ACVIM consensus use an LVIDDN of 1.7 or more as the enlargement criterion for stage B2 mitral valve disease, together with an LA:Ao of 1.6 or more and a murmur of grade 3/6 or louder.
- How should LVIDd be measured?
- EPIC used M-mode guided by the right parasternal short-axis view and averaged at least three cardiac cycles. Enter the result in cm. An LVIDd typed in mm gives an LVIDDN ten times too large. The calculator refuses LVIDd above 12 and flags results above 3.5, but a small number typed in mm can still slip through, so check the unit.
- Does the LA:Ao need a unit?
- No. It is a ratio, so any unit works as long as the atrium and aorta use the same one. The 1.6 cutoff applies to the right parasternal short-axis view in early diastole, as in the ACVIM consensus. A long-axis LA:Ao uses a different cutoff, 2.6 in Malcolm and colleagues' study, so do not enter long-axis measurements here.
Also useful: the vertebral heart score calculator.
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