D. Revel

Post-Conditioning Reduces Infarct Size and Edema in Patients With ST-Segment Elevation Myocardial Infarction

OBJECTIVESnThis study aimed to determine whether post-conditioning at the time of percutaneous coronary intervention could reduce reperfusion-induced myocardial edema in patients with acute ST-segment elevation myocardial infarction (STEMI).nnnBACKGROUNDnMyocardial edema is a reperfusion injury with potentially severe consequences. Post-conditioning is a cardioprotective therapy that reduces infarct size after reperfusion, but no previous studies have analyzed the impact of this strategy on reperfusion-induced myocardial edema in humans.nnnMETHODSnFifty patients with STEMI were randomly assigned to either a control or post-conditioned group. Cardiac magnetic resonance imaging was performed within 48 to 72 h after admission. Myocardial edema was measured by T2-weighted sequences, and infarct size was determined by late gadolinium enhancement sequences and creatine kinase release.nnnRESULTSnThe post-conditioned and control groups were similar with respect to ischemia time, the size of the area at risk, and the ejection fraction before percutaneous coronary intervention. As expected, post-conditioning was associated with smaller infarct size (13 ± 7 g/m(2) vs. 21 ± 14 g/m(2); p = 0.01) and creatine kinase peak serum level (median [interquartile range]: 1,695 [1,118 to 3,692] IU/l vs. 3,505 [2,307 to 4,929] IU/l; p = 0.003). At reperfusion, the extent of myocardial edema was significantly reduced in the post-conditioned group as compared with the control group (23 ± 16 g/m(2) vs. 34 ± 18 g/m(2); p = 0.03); the relative increase in T2W signal intensity was also significantly lower (p = 0.02). This protective effect was confirmed after adjustment for the size of the area at risk.nnnCONCLUSIONSnThis randomized study demonstrated that post-conditioning reduced infarct size and edema in patients with reperfused STEMI.

Prospective comparison of MR lung perfusion and lung scintigraphy

This study attempted to assess the accuracy and potential of lung magnetic resonance (MR) perfusion imaging compared with perfusion scintigraphy in the evaluation of patients with suspected lung perfusion defects. The technique, which uses an inversion recovery turbo‐FLASH sequence with ultra‐short TE (1.4 msec), was tested in 24 patients suspected clinically of having acute pulmonary embolism (n = 19) and in patients with severe pulmonary emphysema (n = 5). Perfusion lung scintigraphy was performed within 48 hours prior to the MRI examination in both groups of patients. The dynamic study was acquired in the coronal plane and consisted of 10 images of 6 slices (a total of 60 images per series). Gadopentetate dimeglumine (0.1 mmol/kg) was manually injected as a compact bolus during the acquisition of the first image. Three senior radiologists reviewed all unprocessed two‐dimensional coronal sections. They were blinded to clinical data and other imaging modalities. For the three observers, the average sensitivity and specificity of MR were 69% and 91%, respectively. The overall agreement between MR and scintigraphy appears to be good, with a good correlation between the two modalities (kappa = 0.63). However, the data showed variability depending on the location of the perfusion defect, with higher accuracy in the upper lobes. The agreement between MR perfusion and scintigraphy appears to be moderate in the left inferior lobe (kappa = 0.48). The data showed an overall good interobsever agreement (kappa = 0.66). MR perfusion of the lung is a promising technique in detecting lung perfusion defects. J. Magn. Reson. Imaging 1999;9:61–68

Automated myocardial edge detection from breath-hold cine-MR images: Evaluation of left ventricular volumes and mass☆

This paper describes an automated edge detection method for the delineation of the endo- and epicardial borders of the left ventricle from magnetic resonance (MR) images. The feasibility of this technique was demonstrated by processing temporal series of cardiac MR images obtained in 12 healthy subjects and acquired from the apex to the base of the heart in multiple anatomic short axis planes with a breath-hold cine-MR acquisition sequence. This procedure allows the entire heart to be imaged in less than 5 min. The automatic program correctly identified the edges in most cases. In poor contrasted images, a fast and user-friendly interactive procedure was used to correct the border delineation. The proposed method for the contour tracing requires a limited degree of control by the user and thus considerably reduces the tedious and long operator time inherent in the usual manual contour tracing tool. The left ventricular volumes were directly measured from these sets of contours by using the Simpson rule, allowing the end-diastolic volumes (EDV), the end-systolic volumes (ESV), the ejection fraction (EF) and the myocardial mass to be determined. The values measured in this study with the dedicated software were similar to the literature values (EDV = 78.3 ml/m2; ESV = 21.1 ml/m2; EF = 73%). Associated with the ultrafast breath-hold cine-MR imaging, the described edge detection method provides an efficient clinical tool for the direct assessment of cardiac function.

Superparamagnetic iron oxide particles and positive enhancement for myocardial perfusion studies assessed by subsecond T1-weighted MRI

Superparamagnetic iron oxide particles (SPIOs) are usually referred to as T2 MR contrast agents, reducing signal intensity (SI) on T2-weighted MR images (negative enhancement). This study reports the original use of SPIOs as T1-enhancing contrast agents, primarily assessed in vitro, and then applied to an in vivo investigation of a myocardial perfusion defect. Using a strongly T1-weighted subsecond MR sequence with SPIOs intravenous (IV) bolus injection, MR imaging of myocardial vascularization after reperfusion was performed, on a dog model of coronary occlusion followed by reperfusion. Immediately after the intravenous bolus injection of 20 mumol/kg of SPIOs, a positive signal intensity enhancement was observed respectively, in the right and left ventricular cavity and in the nonischemic left myocardium. Moreover, compared to normal myocardium, the remaining ischemic myocardial region (anterior wall of the left ventricle) appeared as a lower and delayed SI enhancing area (cold spot). Mean peak SIE in the nonischemic myocardium (posterior wall) was significantly higher than in the ischemic myocardium (anterior wall) (110 +/- 23% vs. 74 +/- 22%, Mann-Whitney test alpha < 1%, n1 = 6, n2-n1 = 0, U > 2). In conclusion, the T1 effect of SPIOs at low dose, during their first intravascular distribution, suggests their potential use as positive markers to investigate the regional myocardial blood flow and some perfusion defects such as the no-reflow phenomenon.

Increased levels of endothelial microparticles CD144 (VE-Cadherin) positives in type 2 diabetic patients with coronary noncalcified plaques evaluated by multidetector computed tomography (MDCT)

OBJECTIVEnThe combination of both morphological and cellular markers of subclinical atherosclerosis, in addition to conventional risk factors, may help to improve cardiovascular prevention in type 2 diabetic patients. The aim of our cross-sectional study was to evidence a putative increase in endothelial (EMP) or platelet (PMP) microparticles, in type 2 diabetic patients with coronary noncalcified plaques detected by multidetector CT (MDCT).nnnMETHODS AND RESULTSnMicroparticles and coronary MDCT were assessed in 56 type 2 diabetic patients with different cardiovascular risk levels. Both EMP (r=0.35, p=0.022) and PMP (rho=0.34, p=0.022) were correlated with hsCRP. EMP were elevated in patients with acute coronary syndromes (p=0.034). EMP count was significantly higher in the presence of noncalcified diseased segments (p=0.01). By contrast, there was no association between hsCRP and noncalcified atheroma. This increase in EMP in noncalcified diseased segment carriers remained borderline significant after adjustment for coronary heart disease and hsCRP. Conversely, there was no association of PMP count with noncalcified diseased segments and no difference in PMP count between patients with and without acute coronary syndrome. No significant association between either EMP and PMP counts and mixed or calcified diseased segments was observed.nnnCONCLUSIONSnWe report for the first time an association between plasma EMP-CD144+ and coronary noncalcified plaques assessed by MDCT in a population of type 2 diabetic patients. EMP might be used as a surrogate marker of unstable plaques, and might help to improve cardiovascular prediction in diabetic patients with intermediate risk.

Contrast agents and cardiac MR imaging of myocardial ischemia: from bench to bedside

This review paper presents, in the first part, the different classes of contrast media that are already used or are in development for cardiac magnetic resonance imaging. A classification of the different types of contrast media is proposed based on the distribution of the compounds in the body, their type of relaxivity and their potential affinity to particular molecules. In the second part, the different uses of the extracellular type of T1-enhancing contrast agent for myocardial imaging is covered from the detection of stable coronary artery disease to the detection and characterization of chronic infarction. A particular emphasis is placed on the clinical use of gadolinium-chelates, which are the universally used type of MRI contrast agent in the clinical routine. Both approaches, first-pass magnetic resonance imaging (FP-MRI) as well as delayed-enhanced magnetic resonance imaging (DE-MRI), are covered in the different situations of acute and chronic myocardial infarction.

Mapping myocardial perfusion with an intravascular MR contrast agent: robustness of deconvolution methods at various blood flows.

Evaluation of quantitative parameters such as regional myocardial blood flow (rMBF), blood volume (rMBV), and mean transit time (rMTT) by MRI is gaining acceptance for clinical applications, but still lacks robust postprocessing methods for map generation. Moreover, robustness should be preserved over the full range of myocardial flows and volumes. Using experimental data from an isolated pig heart preparation, synthetic MR kinetics were generated and four deconvolution approaches were evaluated. These methods were then applied to the first‐pass T1 images of the isolated pig heart using an intravascular contrast agent and rMBF, rMBV and rMTT maps were generated. In both synthetic and experimental data, the fit between calculated and original data reached equally good results with the four techniques. rMBV was the only parameter estimated correctly in numerical experiments. Moreover, using the algebraic method ARMA, abnormal regions were well delineated on rMBV maps. At high flows, rMBF was underestimated at the experimental noise level. Finally, rMTT maps appeared noisy and highly unreliable, especially at high flows. In conclusion, over the myocardial flow range, i.e., 0–400 ml/min/100g, rMBF identification was biased in presence of noise, whereas rMBV was correctly identified. Thus, rMBV mapping could be a fast and robust way to detect abnormal myocardial regions. Magn Reson Med 48:166–179, 2002.

Kinetic characterization of CMD-A2-Gd-DOTA as an intravascular contrast agent for myocardial perfusion measurement with MRI

Recent developments in magnetic resonance imaging (MRI) using specific contrast media allow the assessment of myocardial perfusion. The purpose of this study was to characterize the intravascular properties of a new macromolecular contrast agent, CMD‐A2‐Gd‐DOTA, to evaluate myocardial perfusion. Two groups of isolated pig hearts perfused at various controlled flows were used. To demonstrate the intravascular properties of CMD‐A2‐Gd‐DOTA, the agent was simultaneously injected with 99mTc‐labeled red blood cells in five hearts (group 1). Tracer kinetics of both compounds were assessed by coronary sinus effluent sampling, radioactivity counting and concentration determination in samples for first‐pass time curves measurements. Five other hearts (group 2) were studied using a two‐slice turboFLASH sequence on a 1.5‐T whole‐body MRI in order to evaluate first‐pass CMD‐A2‐Gd‐DOTA signal intensity (SI) versus time curves. In group 1, for the studied flows ranging from 0.8 to 3.1 ml/min−1 • g−1, CMD‐A2‐Gd‐DOTA showed first‐pass concentration curves typical of an intravascular contrast agent. In group 2, MRI parameters, i.e., upslope and mean transit time of SI time curves correlated strongly with myocardial perfusion. Within the physiologic range of flows, CMD‐A2‐Gd‐DOTA was able to demonstrate tracer kinetics for in vivo assessment of myocardial perfusion using MRI. Magn Reson Med 43:403–409, 2000.

Magnetic resonance perfusion imaging in ischemic heart disease.

This review explores the present status of contrast media available for myocardial perfusion studies, the magnetic resonance (MR) sequences adapted to multi‐slice first‐pass acquisitions, and the issue of myocardial perfusion quantification. To date, only low molecular weight paramagnetic gadolinium chelates have been used in clinical protocols for myocardial perfusion. With the availability of fast MR acquisition techniques to follow the first‐pass distribution of the contrast agent in the myocardium, the bolus tracking technique represents the more widely used protocol in MR perfusion studies. On T1‐weighted imaging, the ischemic zone appears with a delayed and lower signal enhancement compared with normally perfused myocardium. Visual analysis of the image series can be greatly improved by image post‐processing to obtain relative myocardial perfusion maps. With an intravascular tracer, myocardial kinetics are in theory easier to analyze in terms of perfusion. In experimental studies, different intravascular or blood pool MR contrast agents have been tested to measure quantitative perfusion parameters. If a simple flow‐limited kinetic model is developed with MR contrast agents, one important clinical application will be the evaluation of the functional consequence of coronary stenoses, ie, non‐invasive evaluation of the coronary reserve. J. Magn. Reson. Imaging 1999;10:423–433.

Presence and Extent of Cardiac Magnetic Resonance Microvascular Obstruction in Reperfused Non-ST-Elevated Myocardial Infarction and Correlation with Infarct Size and Myocardial Enzyme Release

Objective: Microvascular obstruction (MO) is a factor of adverse outcome in patients with ST-elevated myocardial infarction (STEMI). We assessed the presence and extent of MO and its relationship with infarct size and left ventricular (LV) functional parameters after acute non-ST-elevated myocardial infarction (NSTEMI). Methods: Twenty-five patients with first acute NSTEMI underwent a cine and first-pass perfusion cardiac magnetic resonance (CMR) study, with late gadolinium enhancement imaging 72 h after myocardial infarction. Results: MO was detected in 32% of patients, and its extent comprised 0.5–3.1% of the total LV mass (mean 1.9 ± 1.2%). Patients with MO had a significantly larger infarct size than patients without (14.1 ± 5.9 vs. 5.3 ± 4.1% LV mass; p < 0.001). There was no significant difference between both groups for the LV functional parameters and LV ejection fraction (58.5 ± 6.8 vs. 62.6 ± 9.6%; p = 0.29). Patients with MO showed a higher troponin I release (570 ± 364 vs. 148 ± 103 IU; p = 0.003) and a higher creatine kinase release (29,887 ± 18,263 vs. 10,287 ± 5,283 IU; p = 0.007). Conclusions: In patients with acute NSTEMI, MO has a frequency similar to that observed in patients with STEMI and also correlates with the infarct extent. The prognostic significance on clinical outcome remains to be shown in this specific population.