Changes in myocardial density during postinfarction healing: effect on estimation of in vivo left ventricular mass by echocardiographic imaging

Abstract

To determine whether changes in density (rho) of infarct and noninfarct zones during healing and remodeling after myocardial infarction influence estimates of left ventricular mass and detection of temporal changes by imaging, we measured weights (g) and volumes (mL) of infarct, noninfarct, and mixed tissue in hearts removed 1 to 42 days after anterior infarction in three groups of dogs: nonreperfused infarction treated with placebo or captopril, or infarcts reperfused after 2 h. In vivo mass was calculated from in vivo diastolic myocardial volumes (echocardiograms) and an assumed density of 1.05 g/mL or actual values derived from tissue weights and volumes. Over the 42 days, actual density deviated more from the assumed value of 1.05 in infarct than noninfarct zones, and the overall density was higher for reperfused than nonreperfused ventricles (1.09 vs. 1.06 g/mL, p < 0.01). Correction for density improved the correlation between absolute in vivo and postmortem mass slightly but not the detection of relative changes in mass in control, captopril, or reperfusion groups. These findings suggest that (i) densities of infarct and noninfarct zones differ and change during healing, especially after reperfusion, and (ii) correction for density provides more accurate estimates of volume-derived mass in reperfused hearts.

Myocardial Scars More Frequent Than Expected

“…However, the infarct size was probably larger in the acute stage, because it decreases during healing (23,38,39). Furthermore, the fact that the UMI group differed from the group without MI scars in the above 3 parameters suggests a worse prognosis in this group and puts forward the importance of detecting these previously unrecognized MIs.…”

Necropsy Validation of a Novel Method for Left Ventricular Mass Quantification in Porcine Transthoracic and Transdiaphragmal Echocardiography

“…Formaldehyde or the aqueous solution of formaldehyde, also known as formalin, have often been applied as preservation methodology. This approach is reported to reduce LVM and volume without significant impact on myocardial density ( 30 – 32 ), whereas some studies report increased LVM after preservation ( 33 ). To overcome this potential limitation, several studies report adjustment of shrinkage by adding 5% to autopsy/necropsy LVM ( 23 ) or adjustment of increase by reducing autopsy/necropsy LVM by 2–3% ( 33 ).…”

“…Edema may be present in the ischemic region of the LV but also to some degree in adjacent and remote areas ( 34 ). During myocardial infarction, the density of the myocardium increases during initial edema and remains slightly higher after transition to fibrotic tissue compared to healthy myocardium ( 32 ). The pigs in our study were part of a protocol where myocardial infarction was induced by balloon occlusion of the LAD, which may have affected the density of the myocardium.…”