Evidence of residual viable tissue within the infarct area has been reported after myocardial infarction, implying a potential for functional recovery and prognostic benefit after revascularization. The hallmark of echo viability is the presence of stress-induced contractile reserve.
Although 2- dimensional (2D) dobutamine stress echocardiography (DSE), based on detection of contractile reserve has been used as a widely available and relatively low-cost approach for the prediction of functional recovery after myocardial infarction, it is subjective and relies on semi-quantitative evaluation of endocardial excursion and wall thickening. Furthermore, the assessment of contractility in segment adjacent to infarct-related areas may be problematic. This is because endocardial excursion of a segment due to active contraction may be difficult to distinguish from passive tethering motion from adjacent segments.
Newer techniques that measure myocardial deformation, such as tissue Doppler imaging (TDI Sm), may more reliably quantify this response and help improve the inter-observer variability diagnostic accuracy of DSE.
Tissue Doppler Imaging with DSE allow measurements that are independent of the passive tethering effects from segment that complicate the visual wall motion assessment of DSE and concomitant tissue Doppler velocity approaches to viability assessment.
While tissue Doppler imaging parameters have been the focus of research efforts in identifying viable myocardium, there is no common consensus on the best parameters. Therefore, this study sought to assess feasibility and accuracy of TDI (Sm) parameter during DSE for the prediction of functional recovery in patients undergoing revascularization.
The aim of the study to assess the use of tissue Doppler imaging during dobutamine stress echocardiography as a method for evaluation of myocardial viability and subsequent recovery after revascularization.
The present study was conducted on sixty patients with IHD and hibernating viable myocardium proved by DSE who were referred to Benha university hospital, Cardiology department for evaluation of viability prior to the revascularization, then they were followed up after 1 month to detect the functional myocardial recovery.
Every patient was subjected to the followings: careful history taking, full clinical examination, resting standard 12 leads surface ECG, full 2D, M-mode, Doppler echocardiography study in standard views, Dobutamine stress echocardiography (DSE) and tissue Doppler imaging (TDI Sm). All studied parameters including the heamodynamic data and echocardiographic variables (LVEF, WMSI and TD Sm) were assessed twice, at rest and during dobutamine stress. Patients underwent revascularization after assessment by DSE.
Global functional recovery was identified if the LVEF had improved by > 5% on the follow up 2D echocardiography. However, segmental recovery means that number of segments with resting dysfunction that were adequately revascularized, their regional function had improved on follow up study.
1 month later after doing elective PCI, all patients were followed up using conventional echocardiography and all variables (LVEF, WMSI and TD Sm) were assessed again at rest.
In the follow up study, patients were classified according to their global functional recovery into:
-Group I: Included 18 patients (30%) with no functional recovery.
-Group II: Included 42 patients (70%) with functional recovery.
The 42 patients with global functional recovery showed improved values for all studied parameters (EF, WMSI & TD Sm), while the 18 patients with no global functional recovery showed no similar improvement in those parameters.
As a comparison between the two groups, they showed significant improvement of the studied parameters as regard different stages of the test (rest, stress and follow up), while at the follow up stage, there were no significant difference between the two groups as regards the LVEF and the WMSI but there was significant difference as regard TD (Sm) parameter between patients of both groups detected during dobutamine stress and at follow up study with the better values were observed in the recovered group (group II) and that confirm the accuracy of TDI in prediction of functional recovery during the dobutamine stress which was the aim of this study.
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