Future for Infarct Size Quantification

Evidence is mounting, he adds, that screening for patients with larger infract sizes enables identification of patients with a worse prognosis who benefit from more aggressive therapy and more frequent follow-up visits. "Nowadays many more options exist for STEMI patients deemed at high risk of adverse events, including prescription of ACE inhibitors and insertion of devices like CRT cardiac resynchronisation or ICDs", says Badano.

Speckle tracking echocardiography (STE) is a comparatively new non-invasive echocardiography technique well suited to quantifying infarct size. It works by tracking the movement of natural acoustic markers or "speckles" which are present on standard grey ultrasound tissue images. With the use of wall motion tracking software, speckle movement (and therefore myocardial tissue movement) can be visualised during the cardiac cycle. Speckle-tracking can be used to evaluate myocardial strain, which describes the myocardial deformation throughout the cardiac cycle. Reductions in measurement of strain, have been found to show direct relationships to the size of the infarct.

In the study, which presents the first data on use of 3D speckle-tracking in measuring infarct size, Doctor Denisa Muraru and colleagues estimated infarct size and necrosis transmurality in patients with recent STEMI, who had undergone successful treatment with primary PCI. One of the advantages of 3D speckle-tracking over 2D, say the authors, is that it allows the assessment of longitudinal (apex-to-base shortening), circumferential (shortening in the circumferential direction); radial strain (myocardialwall thickeningtowards LV cavity center) and area strain (a deformation parameter combining longitudinal and circumferential strain) at the same time. In the study, 49 patients with recent STEMI, successfully reperfused with primary PCI were assessed by 3D speckle-tracking, and the obtained LV strain parameters were compared with peak troponin I levels, as an estimate of the extent of myocardial cell injury. In a multivariable analysis, results showed that only circumferential strain emerged as a significant independent predictor of infarct size. Furthermore, in the subgroup of 27 patients who underwent additional assessment with delayed-enhancement MRI within 24 hours from the echocardiographic study, circumferential strain again showed the closest correlation with infarct size and the best predictive power to identify LV segments with transmural necrosis among all strain components.

"Our preliminary study demonstrates that 3D circumferential strain could be used as an accurate and reproducible marker for infarct size estimation by ultrasound in STEMI patients," says Muraru. Long term follow-up, she adds, will be needed to verify if 3D strain parameters improve the predictive prognostic value of conventional parameters after STEMI.

COMPAMED.de; Source: European Society of Cardiology