Response to Letter by Weidemann et al Regarding Article, “Global Diastolic Strain Rate for the Assessment of Left Ventricular Relaxation and Filling Pressure”
We thank Weidemann et al for their interest in our study.1 We hereby address their comments. They mistakenly state that we “had some difficulties in patients with wall motion abnormalities”. We are surprised at this comment, as we clearly show that the ratio of E to strain rate in the isovolumetric relaxation period (SRIVR) was significantly related to mean wedge pressure in patients with regional dysfunction (r=0.83, P<0.01) and performed better than the E/Ea ratio (r=0.63, P<0.01).1 The ratio of E/SRIVR accurately identified patients with regional dysfunction and mean pulmonary capillary wedge pressure >15 mm Hg with a sensitivity of 93% and a specificity of 80%. In comparison, the E/Ea ratio had a sensitivity of 68% and a specificity of 60% (for both P<0.05 versus E/SRIVR).1 The concept behind this demonstrated that the clinical utility of left ventricular global strain rate for assessment of left ventricular relaxation is that the whole myocardium is considered as the region of interest and not a single segment or a group of basal segments. Although segmental postsystolic shortening can be present in a number of cardiac diseases, the letter confuses local with global deformation measurements and does not address global SRIVR nor its clinical application, which is highlighted in our study. The significant correlation between global SRIVR and tau seen in animal (r=0.83, P<0.001) and human (r=0.74, P<0.001) studies supports the premise of using global SRIVR as a reliable index of left ventricular relaxation.
Weidemann et al also question the measurement of strain rate with 2-dimensional speckle tracking in comparison with tissue Doppler imaging. Although 2-dimensional speckle tracking may underestimate the peak strain rate, this underestimation is true for all subjects, regardless of cardiac function. Therefore, the principle proved in our study still holds, but one may need different cutoff values when a technique other than speckle tracking is used. The temporal resolution of 10 to 12 ms achieved with 80 to 100 frames/s using 2-dimensional speckle tracking may be compared with color Doppler versus pulsed-wave Doppler to measure myocardial velocities, where color Doppler reflects the mean velocity as opposed to peak velocity by pulsed-wave Doppler. In addition, although a frame rate of 80 to 100 frames per second is lower than the frame rate with tissue Doppler on using a narrow sector, this frame rate (80 to 100 frames per second) provides a temporal resolution of 10 to 12 ms. This resolution is short enough to detect events during the IVR. Finally, in contrast to the theoretical concerns posed in the letter, published studies have shown that functional abnormalities can be reliably detected by cardiac magnetic resonance imaging2 with a frame rate of only 30 to 40 frames per second.
Wang J, Khoury DS, Thohan V, Torre-Amione G, Nagueh SF. Global diastolic strain rate for the assessment of left ventricular relaxation and filling pressures. Circulation. 2007; 115: 1376–1383.
Rosen BD, Gerber BL, Edvardsen T, Castillo E, Amado LC, Nasir K, Kraitchman DL, Osman NF, Bluemke DA, Lima JA Late systolic onset of regional LV relaxation demonstrated in three-dimensional space by MRI tissue tagging. Am J Physiol Heart Circ Physiol. 2004; 287: H1740–H1746.