[Show abstract][Hide abstract] ABSTRACT: Background:
Noninvasive echocardiographic differentiation between old and fresh left ventricular thrombi after myocardial infarction would be of clinical importance to estimate the risk for embolization and the necessity of anticoagulation.
Methods and results:
Fifty-two patients, aged 41 to 87 years, with a thrombus after myocardial infarction were included in this 2-part study: In substudy-I, 20 patients, 10 each with a definite diagnosis of fresh or old thrombus, were included. In the subsequent prospective substudy-II, 32 consecutive patients with an incident thrombus after myocardial infarction but unknown thrombus age were started on phenprocoumon and followed for 6 months. Data on medical history, standard echocardiography, strain-rate (SR) imaging and magnetic resonance tomography were analyzed. In substudy-I, analysis of thrombus deformation revealed the most rapid change in SR during the isovolumetric relaxation period when cavity pressure decreases rapidly. Fresh (range: 5-27 days) and old thrombi (4-26 months) could be discriminated without overlap by peak SR during the isovolumetric relaxation period, using a cutoff value of 1 s(-1). Applying this threshold value in substudy-II, 17 thrombi were echocardiographically classified as fresh (=SR ≥1 s(-1)) and 15 as old. After 6 months in the fresh thrombus group, 16 of 17 thrombi had disappeared (94%), and in 1 patient the thrombus size was diminished by >50% (now presenting an old thrombus SR pattern). In contrast, 14 of the 15 old thrombi remained unchanged in size and deformation (1 thrombus disappeared).
Fresh and old intracavitary thrombi can be reliably differentiated by deformation imaging. In fresh thrombi, anticoagulation with phenprocoumon results in thrombus resolution in most patients.
[Show abstract][Hide abstract] ABSTRACT: Pronounced trabeculation is presented in both left ventricular non-compaction (LVNC) and dilated cardiomyopathy (DCM), which sometimes makes the differentiation difficult. We hypothesized that echocardiographic deformation analysis would help to differentiate these two cardiomyopathies.
We investigated 15 patients with LVNC (9 males; 42 ± 9 years), 15 age- and gender-matched DCM patients, and 15 healthy controls. The echocardiographic diagnosis of LVNC was confirmed by magnetic resonance imaging. In all subjects standard echocardiography and tissue Doppler imaging (TDI) to study regional LV deformation were carried out. No statistical difference was observed in standard echocardiographic parameters between LVNC and DCM patients. Compared with controls, both patient groups showed significantly reduced annular displacements (septal: controls 14 ± 2 mm vs. DCM 6 ± 3 mm vs. LVNC 7 ± 3 mm) and reduced strain values of the LV segments. A characteristic deformation pattern with significantly higher values in the LV base compared with the apex was observed in patients with LVNC by deformation measurements with TDI. This gradient was found particularly in the lateral and inferior wall but spared the anteroseptal wall; non-compaction was not found in basal segments throughout the ventricle and also spared the anteroseptal midventricular wall. In DCM the strain and strain rate values were homogeneously reduced in all LV segments.
A special regional deformation pattern (preserved deformation in basal segments of LVNC) seems to be of major diagnostic help for the definite differential diagnosis of LVNC and DCM.
No preview · Article · Jan 2012 · European Journal of Heart Failure
[Show abstract][Hide abstract] ABSTRACT: To analyze the remodeling processes of the infarct territory in the time course of infarct healing.
Serial late enhancement (LE) studies were performed in 30 patients following reperfused myocardial infarction (MI) in the first and second week post-MI and after 3 months. To characterize infarct remodeling over time, the following variables were derived and analyzed in a blinded fashion: Infarct size (IS, in mm(3)), maximum infarct thickness (IT(max), mm), mean infarct thickness (IT(mean), mm) and the variability of infarct thickness (VIT=IT(max)/IT(mean)). Further, a new parameter for the assessment of infarct remodeling, the infarct extent (IE, mm(2)) was computed. IE quantifies IS in two dimensions along the heart's circumferential and longitudinal directions. IS was divided by the IE to obtain IT(mean).
Overall infarct thickness was highly variable. Infarct shrinkage due to infarct thinning and IE reduction was found in the first months of healing. IS, IT(mean) and IT(max) significantly decreased during follow-up. There was a less consistent change of the IE: IE decreased in 75% of all infarcts from the first week up to 3 months post-MI, whereas 25% of infarcts expanded. Infarct thinning was found in almost all patients (92%), hence occurring in patients with infarct expansion and in patients without infarct expansion.
Infarct thinning and-to a lesser extent-IE reduction, contribute to infarct shrinkage in the time course of infarct healing. Infarct thinning may occur without infarct expansion.
No preview · Article · Jun 2011 · MAGMA Magnetic Resonance Materials in Physics Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: Although (23)Na MRI has been shown to delineate acute myocardial infarction (MI), the time course of in vivo (23)Na MRI during infarct healing remains unknown. In this study (23)Na MRI was combined with contrast-enhanced (CE) (1)H MRI to noninvasively characterize infarct healing in vivo. Serial in vivo 3D (23)Na MRI and (1)H MRI were performed for up to 9 weeks postinfarction in 10 dogs. Radioactive microspheres were used to measure myocardial perfusion, and Hematoxylin-Eosin (H&E) and Masson's trichrome (MT) staining were used to assess interstitial cell infiltrate and collagen content. In vivo (23)Na MRI accurately delineated infarct size up to day 5 postinfarction in comparison with (1)H MRI (8.9% +/- 8.1% vs. 8.6% +/- 7.9% on day 1 postinfarction, P = NS; and 6.3% +/- 6.2% vs. 6.2% +/- 6.2% on days 4/5 postinfarction, P = NS). The in vivo (23)Na MRI signal intensity, expressed as the signal intensity ratio of infarcted tissue vs. noninfarcted tissue (MI/R) peaked on day 1 of infarction (2.04 +/- 0.23) but decreased significantly to 1.27 at 9 weeks postinfarction (P < 0.05) due to granulation tissue infiltrate and collagen deposition. To confirm the MI/R decrease during scar formation ex vivo, we performed (23)Na MRI in 12 rats on day 3 post-MI (N = 5) and after 6 weeks (N = 7). H&E and Picrosirius Red staining confirmed granulation tissue infiltrate on day 3 and scar formation after 6 weeks. MI/R decreased significantly from 1.91 +/- 0.45 on day 3 post-MI to 1.3 +/- 0.09 after 6 weeks. Thus, in vivo (23)Na MRI accurately delineates infarct size up to day 5 postinfarction. In vivo (23)Na MRI signal intensity decreases during infarct healing as a result of the underlying infarct healing process.
No preview · Article · Apr 2005 · Magnetic Resonance in Medicine
[Show abstract][Hide abstract] ABSTRACT: PURPOSE
Areas of microvascular obstruction (MO) after reperfused acute myocardial infarction can be imaged by both first pass perfusion and late enhancement (LE) imaging. However, it is unclear whether both techniques have the same sensitivity for the detection of MO. Purpose of the study was to correlate first pass with LE at different time points after contrast injection concerning the presence and extent of MO.
METHOD AND MATERIALS
18 patients (16 male, 2 female, age 23-68y) were examined at 1.5 T within 7 days after acute reperfused MI (8 anterior wall / 10 inferior wall). First pass perfusion imaging was performed on three short axis slices (basal, midventricular, apical) using 0.025 mmol/kg Gd-BOPTA (multislice SSFP-sequence: TR/TE/TI 2.6/1.1/110 ms). Immediately after first pass imaging, additional 0.075 mmol/kg Gd-BOPTA were administered to reach a dose of 0.1 mmol/kg Gd-BOPTA. LE imaging of the midventricular slice was performed with a single shot inversion recovery-TurboFlash sequence (TR/TE 2.4/1.1) with various TI (TI scout) at 3, 6, 9, 12, and 15 min after contrast injection.
14/18 patients showed a perfusion deficit during first pass representing MO. 5 out of these 14 patients presented with MO during first-pass only, no patient showed MO only at LE images. The detectibility of MO decreased during the time course after contrast injection. At LE imaging, MO was visible in 1/14 patient only up to 3 min, in 1/14 patient up to 6 min, in 2/14 patients up to 9 min, and in 5/14 patients up to 15 min after injection. In this last group, the visible size of MO decreased in 3 patients over time, only 2 patients presented with an identical size of MO in first pass perfusion and LE imaging.
Compared with first pass perfusion, late enhancement imaging fails to detect or underestimates the extent of microvascular obstruction in patients with acute reperfused MI.
[Show abstract][Hide abstract] ABSTRACT: Experimental studies demonstrated persistently increased 23Na content in nonviable myocardium post-myocardial infarction (MI). We hypothesized that nonviable myocardium in humans would show elevated 23Na content at all stages of infarct development, and therefore could be imaged with 23Na MRI. Ten patients were examined on days 4, 14, and 90 after infarction, and five of these patients participated in a 12-month follow-up. Double angulated short-axis cardiac 23Na images were obtained with the use of a 23Na surface coil and an ECG-triggered, 3D gradient-echo sequence. 1H T2-weighted imaging (N = 9) was performed on days 4, 14, and 90. Wall motion was assessed by cine MRI, and the infarct size was determined by late enhancement on day 90. The 23Na signal intensity (SI) of infarcted myocardium was expressed as the percentage increase over 23Na SI of noninfarcted myocardium. All of the patients showed an area of elevated SI on 23Na and 1H T2-weighted images that correlated with wall motion abnormalities and late enhancement. 23Na SI was highest on day 4. It then decreased until day 90, but remained elevated (39% +/- 18%, 31% +/- 17%, 28% +/- 13% on days 4, 14, and 90, respectively, P = 0.001). No further decrease was found 1 year after infarction (25% +/- 7%, P = 0.89 vs. day 90). 1H T2-weighted SI decreased between days 4 and 14, but on day 90 only six of nine patients had a residual elevated SI. Thus, 23Na SI is elevated in nonviable infarction at all time points following MI, and 23Na MRI may become a suitable technique for imaging nonviable myocardium in humans.
No preview · Article · Sep 2004 · Magnetic Resonance in Medicine
[Show abstract][Hide abstract] ABSTRACT: We sought to identify advantages of contrast-enhanced magnetic resonance imaging (MRI) in studying postinfarction ventricular remodeling.
Although sequential measurements of ventricular volumes, internal dimensions, and total ventricular mass have provided important insights into postinfarction left ventricular remodeling, it has not been possible to define serial, directionally opposite changes in resorption of infarcted tissue and hypertrophy of viable myocardium and effects of these changes on commonly used indices of remodeling.
Using gadolinium-enhanced MRI, the time course and geometry of changes in infarcted and noninfarcted regions were assessed serially in dogs subjected to coronary occlusion for 45 min, 90 min, or permanently.
Infarct mass decreased progressively between three days and four to eight weeks following coronary occlusion; terminal values averaged 24 +/- 3% of those at three days. Radial infarct thickness also decreased progressively, whereas changes in circumferential and longitudinal extent of infarction were variable. The ability to define the circumferential endocardial and epicardial extents of infarction allowed radial thinning without epicardial expansion to be distinguished from true infarct expansion. The mass of noninfarcted myocardium increased by 15 +/- 2% following 90-min or permanent occlusion. However, the time course of growth of noninfarcted myocardium differed systematically from that of infarct resorption. Measurements of total ventricular mass frequently failed to reflect concurrent changes in infarcted and noninfarcted regions. Reperfusion accelerated infarct resorption. Histologic reductions in nucleus-to-cytoplasm ratios corresponded with increases in noninfarcted ventricular mass.
Concurrent directionally opposite changes in infarcted and noninfarcted myocardium can be defined serially, noninvasively, and with high spatial resolution and full ventricular coverage following myocardial infarction.
Full-text · Article · Jul 2004 · Journal of the American College of Cardiology
[Show abstract][Hide abstract] ABSTRACT: Reperfusion strategies salvage myocardium at risk in acute myocardial infarction (MI). This clinical study was performed to determine whether areas without evidence of delayed MRI contrast enhancement in MI correspond to viability by means of percent systolic wall thickening (%SWT) and enddiastolic wall thickness (EDWT) in chronic infarction.
Twenty MRI studies were performed in ten patients within 6 days of MI and 3 months post-MI. On a segmental basis the percentage of viable myocardium as defined by contrast-enhanced MRI (no delayed MRI contrast enhancement) in acute MI was measured and was compared with %SWT and EDWT in chronic MI.
Of the 1718 segments in acute infarction in which the percentage of viable myocardium was measured 1333 were found to be completely viable by means of contrast-enhanced MRI (no delayed MRI contrast enhancement). All of these segments revealed %SWT on day 90 post-MI, and 97% of segments were viable by means of an EDWT of more than 5.5 mm. In 85 segments the proportion of viable myocardium was 50-99% (mean 56+/-8%), with 92% segments found to be viable by means of %SWT and 92% by EDWT, and of 156 segments with viable myocardium between 1-49% (36+/-8%) 79% were found to be viable by means of %SWT and 82% by EDWT. Corresponding proportions of 144 segments with transmural delayed MRI contrast enhancement in acute MI were 45% and 17%.
In acute reperfused MI viable myocardium as delineated by contrast-enhanced MRI is correlated with clinical parameters of viability. Delayed MRI contrast enhancement resolves nontransmural MI and may become a valuable clinical tool when planning revascularization procedures.
No preview · Article · Dec 2003 · MAGMA Magnetic Resonance Materials in Physics Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: To design a segmented inversion-recovery turbo fast low-angle shot (turboFLASH) magnetic resonance (MR) imaging pulse sequence for the visualization of myocardial infarction, compare this technique with other MR imaging approaches in a canine model of ischemic injury, and evaluate its utility in patients with coronary artery disease.
Six dogs and 18 patients were examined. In dogs, infarction was produced and images were acquired by using 10 different pulse sequences. In patients, the segmented turboFLASH technique was used to acquire contrast material-enhanced images 19 days +/- 7 (SD) after myocardial infarction.
Myocardial regions of increased signal intensity were observed in all animals and patients at imaging. With the postcontrast segmented turboFLASH sequence, the signal intensity of the infarcted myocardium was 1,080% +/- 214 higher than that of the normal myocardium in dogs-nearly twice that of the next best sequence tested and approximately 10-fold greater than that in previous reports. All 18 patients with myocardial infarction demonstrated high signal intensity at imaging. On average, the signal intensity of the high-signal-intensity regions in patients was 485% +/- 43 higher than that of the normal myocardium.
The segmented inversion-recovery turboFLASH sequence produced the greatest differences in regional myocardial signal intensity in animals. Application of this technique in patients with infarction substantially improved differentiation between injured and normal regions.
[Show abstract][Hide abstract] ABSTRACT: Loss of membrane permeability caused by ischemia leads to cellular sodium accumulation and myocardial edema. This phenomenon has important implications to left ventricular structure and function in the first hours after myocardial infarction. We hypothesized that during this period of time, after prolonged coronary occlusion and complete reflow, the rate of myocardial sodium accumulation is governed by microvascular integrity. We used 3-dimensional (23)Na MRI to monitor myocardial sodium content changes over time in an in vivo closed-chest canine model (n=13) of myocardial infarction and reperfusion. Infarcts with microvascular obstruction (MO) defined by both radioactive microspheres and contrast-enhanced (1)H MRI showed a slower rate of sodium accumulation as well as lower blood flow at 20 minutes and 6 hours after reperfusion. Conversely, the absence of MO was associated with faster rates of sodium accumulation and greater blood flow restoration. In addition, infarct size by (23)Na MRI correlated best with infarct size by triphenyltetrazolium chloride and contrast-enhanced (1)H MRI at 9 hours after reperfusion. We conclude that in reperfused myocardial infarction, sodium accumulation is dependent on microvascular integrity and is slower in regions of MO compared with those with patent microvasculature. Finally, (23)Na MRI can be a useful tool for monitoring in vivo myocardial sodium content in acute myocardial infarction.
No preview · Article · Nov 2000 · Circulation Research
[Show abstract][Hide abstract] ABSTRACT: Myocardial salvage after acute myocardial infarction is defined clinically by early restoration of flow and long-term improvement in contractile function. We hypothesized that contrast-enhanced magnetic resonance imaging (MRI), performed early after myocardial infarction, indexes myocardial salvage. We studied the relationship between the transmural extent of hyperenhancement by contrast-enhanced MRI, restoration of flow, and recovery of function.
The left anterior descending coronary artery was occluded in dogs (n=15) for either 45 minutes, 90 minutes, or permanently. Cine and contrast-enhanced MRI were performed 3 days after the procedure; cine MRI was also done 10 and 28 days after the procedure. The transmural extent of hyperenhancement and wall thickening were determined using a 60-segment model. The mean transmural extent of hyperenhancement for the 45-minute occlusion group was 22% of the 90-minute group and 18% of the permanent occlusion group (P:<0.05 for both). The transmural extent of hyperenhancement on day 3 was related to future improvement in both wall thickening score and absolute wall thickening at 10 and 28 days (P:<0.0001 for each). For example, of the 415 segments on day 3 that were dysfunctional and had <25% transmural hyperenhancement, 362 (87%) improved by day 28. Conversely, no segments (0 of 9) with 100% hyperenhancement improved. The transmural extent of hyperenhancement on day 3 was a better predictor of improvement in contractile function than occlusion time (P:<0.0001).
A reduction in the transmural extent of hyperenhancement by contrast-enhanced MRI early after myocardial infarction is associated with an early restoration of flow and future improvement in contractile function.
[Show abstract][Hide abstract] ABSTRACT: Distinguishing between viable and non-viable myocardium is an important clinical issue. Several magnetic resonance (MR) techniques to address this issue have been proposed. Spectroscopy of phosphorus-31 and hydrogen-1 from creatine as well as imaging of sodium-23 and potassium-39 reflect information related to cellular metabolism. The spatial and temporal resolutions of these techniques are limited, however, by the small magnitude of the MR signal. Proton imaging techniques include examination of pathologic alterations in MR relaxation times (T1 and T2), wall thickness and thickening, cine MRI combined with low-dose dobutamine, first-pass contrast enhancement patterns, and delayed contrast enhancement patterns. Of the proton imaging approaches, cine MRI combined with low-dose dobutamine is supported by the largest body of clinical evidence supporting the hypothesis that the technique yields useful information regarding myocardial viability. Recent data suggest that delayed contrast enhancement examines the transmural extent of viable myocardium irrespective of contractile function and that this technique should also be considered in a clinical setting.
[Show abstract][Hide abstract] ABSTRACT: Distinguishing between viable and non-viable myocardium is an important clinical issue. Several magnetic resonance (MR) techniques to address this issue have been proposed. Spectroscopy of phosphorus-31 and hydrogen-1 from creatine as well as imaging of sodium-23 and potassium-39 reflect information related to cellular metabolism. The spatial and temporal resolutions of these techniques are limited, however, by the small magnitude of the MR signal. Proton imaging techniques include examination of pathologic alterations in MR relaxation times (T-1 and T-2), wall thickness and thickening, cine MRI combined with low-dose dobutamine, first-pass contrast enhancement patterns, and delayed contrast enhancement patterns. Of the proton imaging approaches, cine MRI combined with low-dose dobutamine is supported by the largest body of clinical evidence supporting the hypothesis that the technique yields useful information regarding myocardial viability. Recent data suggest that delayed contrast enhancement examines the transmural extent of viable myocardium irrespective of contractile function and that this technique should also be considered in a clinical setting.
[Show abstract][Hide abstract] ABSTRACT: Tagged magnetic resonance imaging (MRI) can assess myocardial function by tracking the motion of the myocardium during the various phases of the cardiac cycle. In contrast to experimental methods, such as implantation of radiopaque markers or sonomicrometry, tagged MRI is noninvasive, carries no risk of radiation exposure, and can be used in the context of clinical routine. For the physician, using tagged MRI to its fullest potential requires an understanding of the technique and the derived parameters of myocardial systolic function. This work describes the tagged MRI technique and explains the quantification of systolic function with respect to the underlying theory of the mechanics of a continuous medium. The advantages of tagged MRI in coronary artery disease are emphasized, and currently available data on tagged MRI in coronary artery disease are reviewed.
Preview · Article · Feb 2000 · Journal of Cardiovascular Magnetic Resonance
[Show abstract][Hide abstract] ABSTRACT: Brief myocardial ischemia of less than 20 min duration, followed by reperfusion, is known to cause transient contractile dysfunction, often termed myocardial stunning. Tagged magnetic resonance imaging offers a noninvasive method that can be used to quantify this regional mechanical dysfunction in stunned myocardium. To this end, a closed-chest canine model of myocardial stunning was created by short-term (approximately 20-min) coronary occlusion, via inflation of an angioplasty balloon placed fluoroscopically in the left anterior descending (LAD) coronary, followed by reperfusion. Changes in myocardial strain before occlusion, during occlusion, and at 15 and 30 min after reperfusion were determined using repeated-measures analysis of variance. After instrumentation but before coronary occlusion, global reductions in myocardial strain were observed relative to animals that did not undergo coronary catheterization procedures. Declines of 46% and 49% in regional myocardial blood flow in the LAD and left circumflex bed, respectively, from preinstrumentation levels occurred due to coronary angiography and placement of a deflated angioplasty balloon in the LAD for 1 hr. During LAD occlusion, maximum myocardial shortening was significantly reduced in the anterior and anteroseptal regions of the left ventricular apex (i.e., ischemic region) but returned to baseline values by 30 min after reperfusion. No augmentation of myocardial function was observed in the nonischemic regions during occlusion or reperfusion. Thus, this noninvasive technique to evaluate myocardial ischemia demonstrated a graded response in myocardial function to ischemia and persistent regional dysfunction or "myocardial stunning" after short-term coronary occlusion.
Preview · Article · Feb 2000 · Journal of Cardiovascular Magnetic Resonance