Quantification of the spectrum of changes in regional myocardial function during acute ischemia in closed chest pigs: An ultrasonic strain rate and strain study

Defining the Transmurality of a Chronic Myocardial Infarction by Ultrasonic Strain-Rate Imaging

“…During a dobutamine challenge, the typical response pattern of the nontransmural infarct zone was similar to that previously described in our work for acute ischemia. 8 This "ischemic" response is characterized by a dose-dependent increase in postsystolic thickening that is associated with either a reduction or no change in ⑀ SYS . 8 In the present study, the "ischemic" response of the nontransmural infarct zone would suggest that myocardial perfusion to the midmyocardial and epicardial layers via the severely stenotic circumflex artery was inadequate and that any collaterals that had developed were insufficient to support the increased oxygen demand during the dobutamine challenge.…”

“…8 This "ischemic" response is characterized by a dose-dependent increase in postsystolic thickening that is associated with either a reduction or no change in ⑀ SYS . 8 In the present study, the "ischemic" response of the nontransmural infarct zone would suggest that myocardial perfusion to the midmyocardial and epicardial layers via the severely stenotic circumflex artery was inadequate and that any collaterals that had developed were insufficient to support the increased oxygen demand during the dobutamine challenge. This postulate was supported by histological studies of the epicardial layer of the nontransmural infarction, which showed the typical histological changes associated with chronic ischemia.…”

“…4,8,[17][18][19] Motion-based techniques, such as Doppler myocardial velocity measurement 17 or endocardial border detection by color kinesis, 18 are influenced by tethering effects and thus may not represent regional function. In contrast, ultrasonic strain-rate imaging provides several advantages for the quantification of rest or stress-induced ischemia: (1) it quantifies regional myocardial deformation at high temporal resolution; (2) it can quantify regional longitudinal deformation for all left and right ventricular segments; (3) changes in SR SYS have been shown to parallel changes in global contractility 20,21 and to be relatively heart rate independent 20 ; and (4) ⑀ SYS is related to global ejection performance as assessed by either stroke volume 22 or ejection fraction.…”

“…Color Doppler myocardial imaging data were analyzed with dedicated software (TVI, GE Ultrasound). 8 In summary, radial strain rate was estimated by measuring the spatial velocity gradient over a computation area of 3 to 5 mm (the area used being dependent on the wall thickness). A septal myocardial velocity profile was used to time end diastole (onset of isovolumic contraction) and end systole (aortic valve closure).…”

“…A septal myocardial velocity profile was used to time end diastole (onset of isovolumic contraction) and end systole (aortic valve closure). 8 Strain-rate profiles were averaged over 3 consecutive cardiac cycles and integrated over time to derive the natural strain profile using end diastole as the reference point (Speqle, K.U. Leuven, Belgium).…”