The Relationship between Regional Integrated Backscatter Levels and Regional Strain in Normal, Acutely Ischemic, and Reperfused Myocardium
Integrated backscatter (IB) and its cyclic variation (CV) are echocardiographic parameters often used for myocardial tissue characterization. Prior work has suggested that IB is directly related to regional scatterer density while its CV could be induced by local myocardial strain. The purpose of this study was to further test this hypothesis by simultaneously recording cyclic changes in IB and myocardial strain in normal, acutely ischemic and reperfused myocardium.
In ten closed-chest pigs, acute myocardial ischemia was induced by inflating a PTCA balloon in the left circumflex coronary artery. Radiofrequency (RF) M-mode data of the ischemic region of the posterior wall were acquired before, during and immediately after the balloon occlusion. IB and regional radial strain were estimated from the same RF data sets. End-systole was defined on a simulataneously recorded left ventricular pressure trace. The negative radial strain (NRS) was plotted on top of the IB curve.
At baseline, both the NRS and IB pattern paralleled and showed to be minimum at end-systole. During acute ischemia, marked post-systolic thickening was observed which resulted in a post-systolic peak in both the NRS and IB traces: the overall minimum in both curves was phase shifted, i.e. time-delayed. Moreover, the mean IB level increased acutely. Finally, at reperfusion, both the NRS and IB patterns returned to baseline with a minimum at end-systole. However, NRS showed some remaining characteristics of acute ischemic myocardium in contrast to the IB pattern that merely showed a hyperemic but normal response.
IB and NRS thus paralleled over the whole cardiac cycle in normal and acutely ischemic myocardium. At reperfusion the IB curve normalized immediately while the NRS showed some remaining ischemic characteristics. These observations are in concordance with the hypothesis that changes in integrated backscatter are induced by regional three-dimensional strain.
KeywordsCyclic Variation Radial Strain Acute Ischemia Reperfused Myocardium Acute Myocardial Ischemia
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- 2.B. Bijnens, J. D’hooge, M. Schrooten, S. Pislaru, C. Pislaru, B. De Man, J. Nuyts, P. Suetens, F. Van de Werf, G.R. Sutherland, and M.C. Herregods. Are changes in myocardial integrated backscatter restricted to the ischemic zone in acute induced ischemia ? an in-vivo animal study comparing localized with widespread ischemia. J. Am. Soc. Echo., 13(4): 306–315, 2000.Google Scholar
- 3.J. D’hooge, B. Bijnens, F. Jamal, C. Pislaru, J. Thoen, P. Suetens, F. Van de Werf, C. Angermann, F. Rademakers, M.C. Herregods, and G.R. Sutherland. High frame rate myocardial integrated backscatter. does this change our understanding of this acoustic parameter? Eur. J. Echocard., 1(1): 32–41, 2000.CrossRefGoogle Scholar
- 4.J.G. Miller, J.E. Perez, S.A. Wickline, S.L. Baldwin, B. Barzilai, V. Davila-Roman, R.J. Fedewa, A.E. Finch-Johnston, C.S. Hall, S.M. Handley, F.D. Hockett, M.R. Holland, A. Kovacs, G.M. Lanza, S.H. Lewis, J.N. Marsh, J. Mobley, D.E. Sosnovik, R.L. Trousil, K.D. Wallace, and K.R. Waters. Backscatter imaging and myocardial tissue characterization. Proceedings IEEE Ultrasonics Symposium, pages 1373–1383, 1998.Google Scholar
- 6.M.R. Milunski, G.A. Mohr, K.A. Wear, B.E. Sobel, J.G. Miller, and S.A. Wickline. Early identification with ultrasonic integrated backscatter of viable but stunned myocardium in dogs. JACC, 14(2): 462–471, 1989.Google Scholar
- 7.J. D’hooge, F. Jamal, B. Bijnens, J. Thoen, F. Van de Werf, P. Suetens, and G.R. Sutherland. The relationship between regional integrated backscatter levels and regional strain. Proceedings IEEE Ultrasonics Symposium, pages 1325–1328, 1999.Google Scholar
- 8.J. D’hooge, J. Schlegel, P. Claus, B. Bijnens, J. Thoen, F. Van de Werf, G.R. Sutherland, and P. Suetens. Evaluation of transmural myocardial deformation and reflectivity characteristics. Proceedings IEEE Ultrasonics Symposium, pages 1185–1188, 2001.Google Scholar
- [9.]S. Langeland, J. D’hooge, H. Torp, B. Bijnens, and P. Suetens. A simulation study on the performance of different estimators for two-dimensional velocity estimation. Proceedings IEEE Ultrasonics Symposium, page In press, 2002.Google Scholar
- 11.B. Bijnens, J. D’hooge, G.R. Sutherland, M.C. Herregods, J. Nuyts, P. Suetens, and F. Van de Werf. Robustness of integrated backscatter for myocardial tissue characterization. Ultrasound in Medicine & Biology, pages 95–103, 1999.Google Scholar
- 12.P. Theroux, J. Ross, D. Franklin, W.S. Kemper, and S. Sasyama. Regional myocardial function in the conscious dog during acute coronary occlusion and responses to morphine, propranolol, nitroglycerin and lidocain. Circulation, 53(2): 302–314, 1976.Google Scholar
- 13.F. Jamal, M. Szilard, T. Kukulski, X.S. Liu, J. D’hooge, B. Bijnens, F. Rademakers, L. Hatle, I. De Scheerder, and G.R. Sutherland. Changes in systolic and postsystolic wall thickening during acute coronary occlusion and reperfusion in closed-chest pigs: implications for the assessment of regional myocardial function. J. Am. Soc. Echo., 14(7): 691–697, 2001.CrossRefGoogle Scholar
- 14.O. Turschner, J. D’hooge, C. Dommke, P. Claus, E. Verbeken, I. De Scheerder, B. Bijnens, and G.R. Sutherland. The sequential changes in systolic and postsystolic thickening which occur during acute infarction, infarct reperfusion and the expression of reperfusion injury. European Heart Journal, page (Submitted), 2003.Google Scholar