The times they are a-changin': Two-dimensional aortic valve measurements differ throughout diastole

Diastolic aortic valve measurements are used to obtain weight-independent cardiac ratiometric indices. However, whether clinically important variations in valve measurements occur during diastole remains undetermined.

One hundred sixty-three dogs and 40 cats; a mixture of healthy animals and patients with heart disease.

Aortic valve diameter and area were measured at three time-points: early diastole {AoMAX}, during the P-wave {AoP} and at end-diastole {AoMIN}. Measurement beat-to-beat variability was determined. Difference plots were generated for each measurement pair. Aortic measurements were compared by repeated measures analysis of variance.

In dogs, normalised aortic diameters showed a fixed bias of approximately 14% for AoMAX-AoMIN, 6% for AoMAX-AoP and 8% for AoP-AoMIN. In cats, the aortic diameter and area biases were all less than 2.5% and less than 7% respectively. AoMAX was the largest measurement in 78% patients and AoMIN was the smallest measurement in 73% patients. In dogs, AoMAX > AoP > AoMIN (p < 0.0001). Median within-patient measurement variability was 5% for linear dimensions and 8% for area measurements in dogs and 4.5% for linear and 10.4% for area in cats.

Aortic measurements in dogs differ significantly throughout diastole, with Ao(A)MAX > Ao(A)P > Ao(A)MIN. These differences could clinically impact cardiac ratiometric indices. The difference in cats is less than the within-patient measurement variability and unlikely to be of clinical significance.

Operators should adopt a single diastolic time-point for measurement of the aorta to ensure consistency in measuring and reporting in echocardiography.