Why do we need magnetic resonance imaging in cardiology?

Regional myocardial function after intracoronary bone marrow cell injection in reperfused anterior wall infarction - a cardiovascular magnetic resonance tagging study

BACKGROUND

Trials have brought diverse results of bone marrow stem cell treatment in necrotic myocardium. This substudy from the Autologous Stem Cell Transplantation in Acute Myocardial Infarction trial (ASTAMI) explored global and regional myocardial function after intracoronary injection of autologous mononuclear bone marrow cells (mBMC) in acute anterior wall myocardial infarction treated with percutaneous coronary intervention.

METHODS

Cardiovascular magnetic resonance (CMR) tagging was performed 2-3 weeks and 6 months after revascularization in 15 patients treated with intracoronary stem cell injection (mBMC group) and in 13 controls without sham injection. Global and regional left ventricular (LV) strain and LV twist were correlated to cine CMR and late gadolinium enhancement (LGE).

RESULTS

In the control group myocardial function as measured by strain improved for the global LV (6 months: -13.1 ± 2.4 versus 2-3 weeks: -11.9 ± 3.4%, p = 0.014) and for the infarct zone (-11.8 ± 3.0 versus -9.3 ± 4.1%, p = 0.001), and significantly more than in the mBMC group (inter-group p = 0.027 for global strain, respectively p = 0.009 for infarct zone strain). LV infarct mass decreased (35.7 ± 20.4 versus 45.7 ± 29.5 g, p = 0.024), also significantly more pronounced than the mBMC group (inter-group p = 0.034). LV twist was initially low and remained unchanged irrespective of therapy.

CONCLUSIONS

LGE and strain findings quite similarly demonstrate subtle differences between the mBMC and control groups. Intracoronary injection of autologous mBMC did not strengthen regional or global myocardial function in this substudy.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00199823.

Noninvasive separation of large, medium, and small myocardial infarcts in survivors of reperfused ST-elevation myocardial infarction: a comprehensive tissue Doppler and speckle-tracking echocardiography study

BACKGROUND

The objective of the study was to evaluate the ability of established and new parameters of global systolic left ventricle function to estimate myocardial infarct size. Increasing infarct extent is associated with impaired prognosis in chronic ischemic heart disease. Systolic myocardial deformation is a complex 3D process that is mainly influenced by the amount and transmural distribution of viable myocardium. Speckle-tracking echocardiography (2D-STE) enables deformation assessment along the 3 main cardiac axes independent of insonation angle.

METHODS AND RESULTS

Global longitudinal, circumferential, and radial strain and left ventricle twist by 2D-STE, global longitudinal strain rate and strain by tissue Doppler imaging, and left ventricle ejection fraction and wall motion score index were assessed in 40 patients 8.5+/-5.4 months after a first myocardial infarct and compared with global myocardial infarct mass assessed by contrast-enhanced MRI. Longitudinal and circumferential strain by 2D-STE and longitudinal strain and strain rate by tissue Doppler imaging significantly separated medium-sized infarcts from small or large infarcts at the global level (P<0.05). All deformation indices correlated significantly with global infarct mass (P<0.01). Circumferential and longitudinal strains by 2D-STE demonstrated the best ability to identify medium-sized global myocardial infarcts.

CONCLUSIONS

Circumferential and longitudinal strains by 2D-STE correlate with myocardial infarct mass and significantly differentiate among large, medium, and small myocardial infarcts.

Left ventricle longitudinal deformation assessment by mitral annulus displacement or global longitudinal strain in chronic ischemic heart disease: are they interchangeable?

BACKGROUND

Increasing infarct mass is associated with impaired prognosis in chronic ischemic heart disease. Global strain by echocardiographic assessment relates closely to infarct mass assessed by delayed enhancement magnetic resonance imaging but requires deformation analysis in a 16-segment model of the left ventricular. Mitral annular (MA) displacement reflects longitudinal left ventricular deformation and could provide similar information.

METHODS

Global longitudinal strain and MA displacement by Doppler tissue imaging were assessed in 61 patients 9 months after first myocardial infarctions and compared with global myocardial infarct mass assessed using contrast-enhanced magnetic resonance imaging.

RESULTS

Both indices significantly separated medium-sized infarcts from small or large infarcts (P < .05) and correlated significantly with global infarct mass (P < .01 for both). There was a good correlation between global strain and MA displacement (r = 0.65, P < .01). The sensitivities and specificities to identify myocardial infarcts differed only slightly among the indices, but global longitudinal strain tended to be the best.

CONCLUSIONS

Longitudinal deformation by global strain or MA displacement correlated well with myocardial infarct mass and could discriminate between different extents of myocardial infarctions. Global longitudinal strain tended to be better, especially for the identification of the smallest infarcts.

Global longitudinal strain measured by two-dimensional speckle tracking echocardiography is closely related to myocardial infarct size in chronic ischaemic heart disease

2D-STE (two-dimensional speckle tracking echocardiography) is a novel echocardiographic modality that enables angle-independent assessment of myocardial deformation indices. In the present study, we tested whether peak systolic ϵ∥ (longitudinal strain) values measured by 2D-STE could identify areas of MI (myocardial infarction) as determined by CE MRI (contrast-enhanced magnetic resonance imaging). Conventional echocardiographic apical long-axis recordings were performed in 38 patients, 9 months after a first MI. Peak systolic ϵ∥ measured by 2D-STE in 16 left ventricle segments was compared with segmental infarct mass and transmurality assessed by CE MRI. Segmental values were averaged to global and territorial values for assessment of global function and myocardial function in the coronary distribution areas. CE MRI identified transmural infarction in 27 patients, and a mean infarct size of 36±25 g. Peak systolic ϵ∥ correlated with the infarct mass at the global level (r=0.84, P<0.001). A strain value of −15% identified infarction with 83% sensitivity and 93% specificity at the global level and 76% and 95% at the territorial level, and a strain value of −13% identified transmural infarction with 80% sensitivity and 83% specificity at the segmental level. Global infarct mass correlates with the wall motion score index (r=0.70, P<0.001), and left ventricular ejection fraction measured by MRI or echocardiography (r=−0.71 and −0.58, both P<0.001). In chronic infarction, peak systolic ϵ∥ measured by 2D-STE correlates with the infarct mass assessed by CE MRI at a global level, and separates infarcted from non-infarcted tissue. Global strain is an excellent predictor of myocardial infarct size in chronic ischaemic heart disease.