The effect of microvascular obstruction and intramyocardial hemorrhage on contractile recovery in reperfused myocardial infarction: insights from cardiovascular magnetic resonance

Abstract

BackgroundFollowing acute myocardial infarction (AMI), microvascular obstruction (MO) and intramyocardial hemorrhage (IMH) adversely affect left ventricular remodeling and prognosis independently of infarct size. Whether this is due to infarct zone remodeling, changes in remote myocardium or other factors is unknown. We investigated the role of MO and IMH in recovery of contractility in infarct and remote myocardium.MethodsThirty-nine patients underwent cardiovascular magnetic resonance (CMR) with T2-weighted and T2* imaging, late gadolinium enhancement (LGE) and myocardial tagging at 2, 7, 30 and 90 days following primary percutaneous coronary intervention for AMI. Circumferential strain in infarct and remote zones was stratified by presence of MO and IMH.ResultsOverall, infarct zone strain recovered with time (p < 0.001). In the presence of MO with IMH and without IMH, epicardial strain recovered (p = 0.03, p < 0.01 respectively), but mid-myocardial or endocardial strain did not (mid-myocardium: p = 0.05, p = 0.12; endocardium: p = 0.27, p = 0.05, respectively). By day 90, infarcts with MO had more attenuated strain in all myocardial layers compared to infarcts without MO (p < 0.01); those with IMH were attenuated further (p < 0.01). Remote myocardial strain was similar across groups at all time-points (p > 0.2). Infarct transmural extent did not correlate with strain (p > 0.05 at each time point). In multivariable logistic regression, MO and IMH were the only significant independent predictors of attenuated 90-day infarct zone strain (p = 0.004, p = 0.011, respectively).ConclusionsStrain improves within the infarct zone overall following reperfusion with or without MO or IMH. Mid-myocardial and endocardial infarct contractility is diminished in the presence of MO, and further in the presence of IMH. MO and IMH are greater independent predictors of infarct zone contractile recovery than infarct volume or transmural extent.

Cardiac MR assessment of microvascular obstruction

“…3,6 The presence of MVO on LGE sequences has a significant adverse prognostic impact and has been shown to correlate closely with adverse left ventricular remodelling. 5,7 Patients with MVO demonstrate greater left ventricular end-diastolic and endsystolic volumes at follow-up. 1,5,7 Patients with MVO on LGE typically demonstrate persistent global left ventricular dysfunction, with less improvement in left ventricular ejection fraction when compared with patients without MVO.…”

“…5,7 Patients with MVO demonstrate greater left ventricular end-diastolic and endsystolic volumes at follow-up. 1,5,7 Patients with MVO on LGE typically demonstrate persistent global left ventricular dysfunction, with less improvement in left ventricular ejection fraction when compared with patients without MVO. 1,4 In addition, patients with MVO on LGE are significantly more likely to experience future major adverse cardiovascular events, hospital admission and pre-mature cardiovascular-related death than patients do without MVO.…”

“…3 Myocardial haemorrhage can be seen within the infarct core, and although MVO and haemorrhage are closely linked, they remain distinct pathological entities. 3,5 At sites of MVO, red cell extravasation may be demonstrated in regions of endothelial damage at the myocardial capillary bed. 3 Animal studies have shown that MVO may occur in the absence of myocardial haemorrhage, but myocardial haemorrhage does not occur in the absence of MVO.…”

“…Accurate diagnosis of MVO is of great importance, as its presence has been shown to be an independent predictor of poor prognostic outcome following myocardial infarction, including adverse left ventricular remodelling, subsequent major adverse cardiovascular events and death. 1,[4][5][6] …”

Relationship of Myocardial Strain and Markers of Myocardial Injury to Predict Segmental Recovery After Acute ST-Segment–Elevation Myocardial Infarction

“…Circumferential strain (Ecc), 11 myocardial salvage (MSI), 17 LGE-derived microvascular obstruction (late MVO), 11,17,18 and intramyocardial hemorrhage (IMH) 18 have been assessed in a few small studies. There are no studies investigating whether they offer additive value to the predictive accuracy of LGE.…”