Temporal changes of strain parameters in the progress of chronic ischemia: with comparison to transmural infarction

The aim of this study was to reveal the temporal and spatial changes of strain parameters during the progression of chronic coronary ischemia. Fourteen pigs received occluder implantation to create gradual ischemia (CI), while six pigs underwent a sham surgery (Control). Six pigs after myocardial infarction were also studied (MI). Strain analysis was performed using a speckle-tracking algorithm. Eleven of the 14 animals with occluder implantation had total occlusion of the left anterior descending artery with collaterals at 1 month (early occlusion group), whereas three pigs had occlusion at 3 months (late occlusion group). Both radial strain (RS) and circumferential strain (CS) of ischemic area deteriorated at 1 month in the early occlusion group and remained at the same level throughout the remaining 2 months of the experiment. In the late occlusion group, RS gradually declined, while CS took the same course as Control until the 2 month time point. Thereafter, both metrics reached the same level as the early occlusion group at the time of occlusion. Interestingly, RS in the remote area decreased moderately, whereas CS remained normal in CI pigs. The comparison between CI and MI revealed preserved CS at the ischemic area in CI pigs. Both RS and CS deteriorate by the time total coronary occlusion was established and remain at the same level thereafter. Altered RS in the remote area may be an indicator of remodeling in the non-ischemic area, whereas CS may be useful for distinguishing between transmural and non-transmural scar.