Henk Everaars

Strain analysis is superior to wall thickening in discriminating between infarcted myocardium with and without microvascular obstruction

ObjectivesThe aim of the present study was to evaluate the diagnostic performances of strain and wall thickening analysis in discriminating among three types of myocardium after acute myocardial infarction: non-infarcted myocardium, infarcted myocardium without microvascular obstruction (MVO) and infarcted myocardium with MVO.MethodsSeventy-one patients with a successfully treated ST-segment elevation myocardial infarction underwent cardiovascular magnetic resonance imaging at 2-6 days after reperfusion. The imaging protocol included conventional cine imaging, myocardial tissue tagging and late gadolinium enhancement. Regional circumferential and radial strain and associated strain rates were analyzed in a 16-segment model as were the absolute and relative wall thickening.ResultsHyperenhancement was detected in 418 (38%) of 1096 segments and was accompanied by MVO in 145 (35%) of hyperenhanced segments. Wall thickening, circumferential and radial strain were all significantly diminished in segments with hyperenhancement and decreased even further if MVO was also present (all p < 0.001). Peak circumferential strain (CS) surpassed all other strain and wall thickening parameters in its ability to discriminate between hyperenhanced and non-enhanced myocardium (all p < 0.05). Furthermore, CS was superior to both absolute and relative wall thickening in differentiating infarcted segments with MVO from infarcted segments without MVO (p = 0.02 and p = 0.001, respectively).ConclusionsStrain analysis is superior to wall thickening in differentiating between non-infarcted myocardium, infarcted myocardium without MVO and infarcted myocardium with MVO. Peak circumferential strain is the most accurate marker of regional function.Key Points• CMR can quantify regional myocardial function by analysis of wall thickening on cine images and strain analysis of tissue tagged images.• Strain analysis is superior to wall thickening in differentiating between different degrees of myocardial injury after acute myocardial infarction.• Peak circumferential strain is the most accurate marker of regional function.

Diagnostic value of longitudinal flow gradient for the presence of haemodynamically significant coronary artery disease

Aims The longitudinal myocardial blood flow (MBF) gradient derived from positron emission tomography (PET) has been proposed as an emerging non-invasive index of haemodynamically significant coronary artery disease (CAD). This study aimed to investigate the diagnostic value of longitudinal MBF gradient for the presence of haemodynamically significant CAD. Methods and results A total of 204 patients (603 vessels) with suspected CAD underwent [15O]H2O PET followed by invasive coronary angiography with fractional flow reserve (FFR) of all major coronary arteries. Longitudinal base-to-apex MBF gradients were assessed by two methods, using MBF in apical and mid (Method 1) or in apical and basal (Method 2) myocardial segments to calculate the gradient. The hyperaemic longitudinal MBF gradient was only weakly correlated with FFR (Method 1: r = 0.12, P = 0.02; Method 2: r = 0.22, P < 0.001). The hyperaemic longitudinal MBF gradient (by both methods), had lower diagnostic value when compared with hyperaemic MBF for the presence of haemodynamically significant CAD, defined as an FFR ≤ 0.80. No significant correlations between longitudinal MBF gradients and FFR were noted in proximal lesions, whereas longitudinal MBF gradients and FFR were significantly correlated in non-proximal lesions (r = 0.57, P < 0.001). Conclusion PET measured longitudinal flow parameters had lower diagnostic value when compared with hyperaemic MBF for the presence of haemodynamically significant CAD. Since lesion location was found to affect the correlation of PET measured longitudinal flow parameters and FFR, presence of a longitudinal flow gradient may be partly caused by normalization to a relatively normal perfused areas.

The influence of microvascular injury on T1- and T2*-relaxation times after acute myocardial infarction

Background Pre-contrast T1-mapping and Late Gadolinium Enhancement (LGE) imaging offer a detailed characterization of the infarcted myocardium and its severity after acute myocardial infarction (AMI). However, the influence of T2*-effects in infarcts with microvascular injury (MVI) on local T1-mapping values has not yet been elucidated. We evaluate the effect of T2*-decay on T1relaxation times in the infarcted myocardium in patients after AMI. Methods Forty-three patients after AMI, treated with successful primary percutaneous coronary intervention, underwent CMR at 4 (3-5) days, for cine imaging, pre-contrast T1mapping and T2*-mapping, and LGE. MVI was defined as a contrast-devoid area in the core of the infarcted, hyperenhanced myocardium on the LGE images. T1and T2*-mapping was performed in short-axis orientation at the level of the infarcted area. T1- and T2*relaxation time values were determined in a region of interest (ROI) in [1] the core of the infarcted myocardium within the hyperenhanced region incorporating any area with MVI when present, [2] the border zone within the hyperenhanced myocardium but outside any areas of MVI, and [3] remote myocardium without hyperenhancement. Left ventricular volumes and ejection fraction (LVEF) were derived from the cine images and infarct size was determined on the LGE images. Normal distribution of relaxation times was achieved by log-transformation. Results Twenty of the 43 patients (47%) had MVI. Infarct cores with MVI had significantly lower T1-values (MVI 1062 [974-1107]ms, vs. no MVI 1128 [1051-1185]ms, p = 0.02) and lower T2*-values (MVI 20.3 [18.2-23.3]ms vs. no MVI 30.9 [26.0-38.9]ms, p < 0.001) than infarct cores without MVI. Border zone T2*-values did not differ between patients with and without MVI; however, border zone T1-values were significantly longer in patients with MVI than in patients without MVI (MVI 1140 [1096-1174]ms, vs. no MVI 1050 [1007-1089]ms, p = 0.009). As would be expected, remote T1-values did not differ between patients with and without MVI (MVI 1000 [965-1011]ms vs. no MVI 977 [929-993]ms, p = 0.13). A significant correlation was found between T2*values and LVEF (r = 0.60, p < 0.001), and between T2*-values and infarct size (r = -0.60, p < 0.001). For T1-values, however, these relations did not exist. Conclusions Patients with reperfused AMI have shorter T1- and T2*relaxation times in the infarct core when MVI is present. In the adjacent border zone, T1-relaxation times are longer in patients with MVI. This has important implications for the interpretation of pre-contrast T1-mapping values shortly after AMI.