Author + information
- Maurizio Galderisi, MD⁎ ()
- ↵⁎Department of Clinical and Experimental Medicine, Block 1, Federico II University of Naples, Via S. Pansini 5, 80131 Naples, Italy
The present letter concerns the State-of-the-Art Paper by Marwick (1) published in the April 4, 2006, issue of the Journal. The clinical impact of this report is valuable because the potentiality of Doppler echocardiographically-derived strain rate imaging (SRI) is often emhpasized, whereas the technical limitations are not always shown. The illustrations, derived from a reference group for this methodology, clearly demonstrate sources of pitfalls and misinterpretations due to either wrong recording or measure of SRI.
In our experience, at least 2 of these technical limitations may be overtaken or blunted by arrangements performed during imaging recording and/or off-line measures. First, the noisy signal of SRI (especially of strain rate) can be drastically reduced by very high frame rates of color tissue Doppler recording. Modern machines are certainly able to provide frame rates ≥100 frames/s. However, the highest frame rates are obtained with the narrowest scan of a given, isolated wall. By this modality, frame rates >250 frames/s (even >300 frames/s in the last-generation equipment) can be achieved, with consequent optimization of both strain and strain-rate measure. The obvious price to pay for this operation is the loss of visualization of the overall ventricle and the consequent need to separately assess the various left ventricular (LV) walls. In the absence of regional wall motion abnormalities and/or focal cardiac pathologies, the wall with the best imaging quality (e.g., posterior septum or inferior wall) may be chosen as a reference region of interest. The consequent quantitative information may be extrapolated to the overall myocardium, both at rest and during pharmacological response to dobutamine, to assess the functional state and the inotropic reserve, respectively.
In addition, the possible inappropriate timing of the different phases of the cardiac cycle may be overtaken. The application of SRI implies per se a correct identification of systolic and diastolic time intervals. This aspect is crucial for the assessment of myocardial dyssynchrony, when a postsystolic motion, occurring during a prolonged relaxation time, might be confused with the normal systolic contraction. This may be avoided by marking end-diastole and end-systole on previously recorded pulsed Doppler imaging of mitral inflow and LV output flow, respectively. In the last-generation machines, by using this method, markers of mitral valve opening and closure as well as markers of aortic valve opening and closure are automatically superimposed to SRI (2). Alternatively, systolic and diastolic time intervals can be identified by the method proposed by Voigt et al. (3): LV end-systole (i.e., the aortic valve closure) is derived by color tissue Doppler superimposed to M-mode, as the end-systolic thin blue line, which, caused by a brief backward motion of the mitral valve secondary to aortic valve closure, is visualized within the otherwise red-colored mitral anterior leaflet. This method is, however, complex and difficult to apply in the clinical setting.
Nowadays, SRI remains a tool useful for research purposes more than for clinical application. Nevertheless, some information about refinements and arrangements during recording and reading of the examination may lead to a more appropriate use of this tool.
- American College of Cardiology Foundation