Author + information
- Charles S. Chung, PhD∗ ( and )
- Luis Afonso, MD
- ↵∗Department of Physiology, Wayne State University, 5374 Gordon H Scott Hall, 540 East Canfield Street, Detroit, Michigan 48201
We read with considerable interest the state-of-the-art paper, “Cardiac Imaging to Evaluate Left Ventricular Diastolic Function,” by Flachskampf et al. (1). The authors provide comprehensive coverage of the methods used to image and analyze diastolic function.
For 2 reasons, heart rate merits further discussion. 1) There is significant translational interest in diastolic function. It is sometimes underappreciated that, in the mouse and rat models, one cannot separate early diastolic and late atrial filling without significantly reducing the heart rate. 2) In humans, it is not possible to separate early diastolic and late atrial filling modestly at fast heart rates (≥100 beats/min).
Figure 1A shows the importance of heart rate. Systolic duration was reduced only modestly, and E-wave peak velocity and timing were essentially unchanged as the heart rate increased. Atrial filling merges (fusion) with the E-wave until it was impossible to differentiate. The atrial contribution to filling is nearly preserved, simply adding to the E-wave (2).
Importantly, one cannot accurately quantify diastolic function without knowing what happens when the E-wave and A-wave are separated. The same principles apply to diastolic function in a mouse (3).
Figure 1B schematically shows an important caution: one might mistake the merged E-wave and A-wave as a restrictive filling E-wave and attribute other velocity features in the Doppler signal as the A-wave. This overestimates E-wave velocities and underestimates the deceleration time. Unfortunately, the example of restrictive filling in the review of Flachskampf et al. (1) (Figure 4 in their article) may be influenced by this issue. The systolic duration would be quite short (<200 ms) if the bright spot after the E-wave is truly the A-wave. If we assume that the QRS timing is accurately aligned with end-diastole, a more reasonable systolic duration (300 ms) is revealed between the fused E-wave and A-wave. This is consistent with the QRS timing to e′ duration on the tissue Doppler image (TDI). But what is that bright Doppler velocity, if it is not the A-wave? The velocity is coincident with the S-wave of the TDI and is likely the result of the velocity of the blood and mitral valve toward the apex (4).
The authors appropriately note that analysis should be performed after the heart rate decreases if fusion occurs (1), and this point must be emphasized. Clinically, the E wave and e′ velocities do not change much after the termination of exercise, so unmerged velocities should be obtained during the early recovery period (5).
The example presented in Figure 1 can help guide analysis of diastolic function and identify fusion of the E-wave and A-wave. Sonographers should be aware of the impact of a high heart rate, be able to identify it visually and quantitatively, and attempt to temporarily reduce it (an unfortunately difficult challenge in a rodent!). We urge investigators and clinicians to carefully consider heart rate in their evaluation of diastolic function.
Please note: Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation