Assessment of no-reflow regions using cardiac MRI

Ultrashort VIBE-Dixon versus Cine and late gadolinium enhancement MRI sequences for cardiac thrombus detection

PURPOSE

To determine the diagnostic accuracy of volumetric interpolated breath-hold examination sequences with fat suppression in Dixon technique (VIBE-Dixon) for cardiac thrombus detection.

METHOD

From our clinical database, we retrospectively identified consecutive patients between 2014 and 2022 who had definite diagnosis or exclusion of cardiac thrombus confirmed by an independent adjudication committee, serving as the reference standard. All patients received 2D-Cine plus 2D-Late-Gadolinium-Enhancement (Cine + LGE) and VIBE-Dixon sequences. Two blinded readers assessed all images for the presence of cardiac thrombus. The diagnostic accuracy of Cine + LGE and VIBE-Dixon was determined and compared.

RESULTS

Among 141 MRI studies (116 male, mean age: 61 years) mean image examination time was 28.8 ± 3.1 s for VIBE-Dixon and 23.3 ± 2.5 min for Cine + LGE. Cardiac thrombus was present in 49 patients (prevalence: 35 %). For both readers sensitivity for thrombus detection was significantly higher in VIBE-Dixon compared with Cine + LGE (Reader 1: 96 % vs.73 %, Reader 2: 96 % vs. 78 %, p < 0.01 for both readers), whereas specificity did not differ significantly (Reader 1: 96 % vs. 98 %, Reader 2: 92 % vs. 93 %, p > 0.1). Overall diagnostic accuracy of VIBE-Dixon was higher than for Cine + LGE (95 % vs. 89 %, p = 0.02) and was non-inferior to the reference standard (Delta ≤ 5 % with probability > 95 %).

CONCLUSIONS

Biplanar VIBE-Dixon sequences, acquired within a few seconds, provided a very high diagnostic accuracy for cardiac thrombus detection. They could be used as stand-alone sequences to rapidly screen for cardiac thrombus in patients not amenable to lengthy acquisition times.

Growth Differentiation Factor 15 as a Predictor of the No-Reflow Phenomenon in Patients with ST-Segment Elevation Myocardial Infarction

Growth differentiation factor 15 (GDF-15) and the no-reflow phenomenon are predictors of mortality after ST-segment elevation myocardial infarction (STEMI). We aimed to assess the relation between GDF-15 concentration on admission and the no-reflow phenomenon. The study was conducted prospectively among 80 consecutive STEMI patients who underwent primary PCI. No-reflow was defined as a corrected TIMI frame count > 27 and myocardial blush grade < 3 after PCI. GDF-15 was measured on admission. We assessed long-term (1.3 years) total mortality and the risk factors of no-reflow. The mean age was 65 (SD 12) years. Mortality rates were 2.5% and 7.5% for in-hospital and long-term observations, respectively. No-reflow occurred in 24% of patients. A negative correlation between TIMI flow after PCI and GDF-15 concentration (R = −0.2540, p = 0.023) was found. Receiver operating characteristic (ROC) analysis revealed GDF-15 as a predictor of no-reflow (AUC-0.698, 95%CI-0.552−0.843, p < 0.05). The multivariate logistic regression analysis revealed that the risk factors for no-reflow occurrence were higher age, a concentration of GDF-15 > 1503 pg/mL, lower systolic blood pressure, and higher troponin I concentration on admission. A higher concentration of GDF-15 can be used as an additional marker of ischemia/reoxygenation injury, subsequent no-reflow phenomenon, and worse long-term outcomes in patients with STEMI.

Near-infrared spectroscopy to predict microvascular obstruction after primary percutaneous coronary intervention

BACKGROUND

Successful restoration of epicardial coronary artery patency by primary percutaneous coronary intervention (PPCI) for ST-elevation myocardial infarction (STEMI) does not always lead to adequate reperfusion at the microvascular level.

AIMS

This study sought to investigate the association between lipid-rich coronary plaque identified by near-infrared spectroscopy combined with intravascular ultrasound (NIRS-IVUS) and microvascular obstruction (MVO) detected by cardiac magnetic resonance imaging (MRI) after PPCI for STEMI.

METHODS

We investigated 120 patients with STEMI undergoing PPCI. NIRS-IVUS was used to measure the maximum lipid core burden index in 4 mm (maxLCBI4 mm) in the infarct-related lesions before PPCI. Delayed contrast-enhanced cardiac MRI was performed to evaluate MVO one week after PPCI.

RESULTS

MVO was identified in 40 (33%) patients. MaxLCBI4 mm in the infarct-related lesion was significantly larger in the MVO group compared with the no-MVO group (median [interquartile range]: 745 [522-853] vs 515 [349-698], p<0.001). A multivariable logistic regression model showed that maxLCBI4 mm was an independent predictor of MVO (odds ratio: 24.7 [95% confidence interval: 2.5-248.0], p=0.006). Receiver operating characteristic curve analysis demonstrated that maxLCBI4 mm >600 was the optimal cut-off value to predict MVO (Youden index=0.44 and area under the curve=0.71) with a sensitivity of 75% and a specificity of 69%.

CONCLUSIONS

Lipid content measured by NIRS in the infarct-related lesions was associated with the occurrence of MVO after PPCI in STEMI.

Epicardial Surface Area of Infarction: A Stable Surrogate of Microvascular Obstruction in Acute Myocardial Infarction

BACKGROUND

Microvascular obstruction (MO) is a pathophysiologic complication of acute myocardial infarction that portends poor prognosis; however, it is transient and disappears with infarct healing. Much remains unknown regarding its pathophysiology and whether there are predictors of MO that could function as stable surrogates. We tested for clinical and cardiovascular magnetic resonance predictors of MO to gain insight into its pathophysiology and to find a stable surrogate.

METHODS

Three hundred two consecutive patients from 2 centers underwent cardiovascular magnetic resonance within 2 weeks of first acute myocardial infarction. Three measures of infarct morphology: infarct size, transmurality, and a new index-the epicardial surface area (EpiSA) of full-thickness infarction-were quantified on delayed-enhancement cardiovascular magnetic resonance.

RESULTS

Considering all clinical characteristics, only measures of infarct morphology were independent predictors of MO. EpiSA was the strongest predictor of MO and provided incremental predictive value beyond that of infarct size and transmurality (P<0.0001). In patients with 3-month follow-up cardiovascular magnetic resonance (n=81), EpiSA extent remained stable while MO disappeared, and EpiSA was a predictor of adverse ventricular remodeling. After 20 months of follow-up, 11 died and 1 had heart transplantation. Patients with an EpiSA larger than the median value (≥6%) had worse outcome than those with less than the median value (adverse events: 6.4% versus 1.9%, P=0.045).

CONCLUSIONS

The EpiSA of infarction is a novel index of infarct morphology which accurately predicts MO during the first 2 weeks of MI, but unlike MO, does not disappear with infarct healing. This index has potential as a stable surrogate of the presence of acute MO and may be useful as a predictor of adverse remodeling and outcome which is less dependent on the time window of patient assessment.

State of the Art: No-Reflow Phenomenon

Primary percutaneous coronary intervention is the preferred reperfusion strategy for the management of acute ST-segment elevation myocardial infarction. No reflow is characterized by the inadequate myocardial perfusion of a given segment without angiographic evidence of persistent mechanical obstruction of epicardial vessels. Both pharmacologic and device-based strategies have been tested to resolve coronary no reflow. This article provides an updated overview of the no-reflow phenomenon, discussing clinical evidence and ongoing investigations of existing and novel therapeutic strategies to counteract it.

The impact of lesion complexity on no-reflow phenomenon and predictors of reversibility in patients treated with primary percutaneous intervention

OBJECTIVES

Complex coronary lesions are more prone to complications; however, the relationship between complex coronary lesions and no-reflow phenomenon in patients undergoing primary percutaneous intervention (pPCI) is still not clarified. Previous studies reported the association of total coronary artery complexity with no-reflow; however, impact of culprit lesion complexity on no-reflow is not known. In this study, we aimed to investigate the impact of culprit lesion complexity on no-reflow phenomenon. Furthermore, we aimed to investigate the factors that are related to reversibility of no-reflow.

METHODS

We prospectively included 424 patients treated with pPCI. Patients' baseline characteristics and clinical variables were recorded. Reversibility of no-reflow was decided according to final angiography or ST resolution during the first hour following pPCI. There were 90 patients with a diagnosis of no-reflow constituted group 1 and patients without no-reflow constituted group 2. Complexity of coronary artery disease was assessed with SYNTAX score and culprit lesion complexity was assessed with both American College of Cardiology/Society of Cardiovascular Angiography and Interventions lesion classification and SYNTAX score.

RESULTS

Complexity of culprit lesion was significantly higher in group 1 patients (type C lesion 76.6 vs. 27.8%; P < 0.001 and SYNTAX score 8.7 ± 3.0 vs. 6.2 ± 2.6; P < 0.001, respectively, group 1 vs. 2). Multivariate analyses revealed that lesion complexity is independently associated with no-reflow. Among 90 patients of group 1, 43 patients were classified as reversible no-reflow. Logistic regression analysis revealed that only ischaemia duration is independently associated with reversibility of no-reflow.

CONCLUSION

Our study demonstrated that culprit lesion complexity is independently associated with no-reflow phenomenon and short ischaemic duration is significantly associated with reversibility of no-reflow.

VEGF-A plasma levels are associated with microvascular obstruction in patients with ST-segment elevation myocardial infarction

BACKGROUND

Microvascular obstruction (MVO) is associated with poor outcome after ST-segment elevation myocardial infarction (STEMI). Vascular endothelial growth factor-A (VEGF-A) is a vascular permeability inducer playing a key role in MVO pathogenesis. We aimed to assess whether VEGF-A levels are associated with MVO, when evaluated by magnetic resonance imaging (MRI) in STEMI patients.

METHODS

The multicenter prospective PREGICA study included a CMR substudy with all consecutive patients with a first STEMI who had undergone cardiac MRI at baseline and at 6-month follow-up. Patients with initial TIMI flow >1 were excluded. VEGF-A levels were measured in blood samples drawn at inclusion.

RESULTS

Between 2010 and 2017, 147 patients (mean age 57 ± 10 years; 84% males) were included. MVO was present in 65 (44%) patients. After multivariate analysis, higher troponin peak (OR 1.005; 95% CI 1.001-1.008; p = 0.007) and VEGF-A levels (OR 1.003; 95% CI 1.001-1.005; p = 0.015) were independently associated with MVO. When considering only patients with successful percutaneous coronary intervention (final TIMI flow 3, n = 130), higher troponin peak (p = 0.004) and VEGF-A levels (p = 0.03) remained independently predictive of MVO. Moreover, MVO was associated with adverse left ventricular (LV) remodeling and VEGF-A levels were significantly and inversely correlated with LV ejection fraction (EF) at 6-month follow-up.

CONCLUSION

Our results show that VEGF-A levels were independently associated with MVO during STEMI and correlated with mid-term LVEF alteration. VEGF-A could therefore be considered as a biomarker of MVO in STEMI patients and be used to stratify patient prognosis.

The Relation Between No-Reflow Phenomenon and Complete Blood Count Parameters

The no-reflow (NR) phenomenon represents an acute reduction in coronary blood flow without coronary vessel obstruction, coronary vessel dissection, spasm, or thrombosis. No reflow is an important complication among patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). The complete blood count (CBC) is one of the most frequently ordered laboratory tests in clinical practice. Various studies have evaluated the performance of CBC parameters to predict disease severity and mortality risk. Automated cell counters are routinely available in many clinical laboratories and can be used to determine red blood cell distrubiton width (RDW), platetecrit, platelet count, and and some ratios like the neutrophil-lymphocyte ratio and RDW-platelet ratio. These hematological markers have been reported to be independent predictors of impaired angiographic reperfusion and long-term mortality among patients with STEMI undergoing pPCI. In this context, we reviewed the role of admission CBC parameters for the prediction of NR in patients with STEMI undergoing pPCI.

The no-reflow phenomenon: State of the art

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy for acute ST-segment elevation myocardial infarction (STEMI), with nearly 95% of occluded coronary vessels being reopened in this setting. Despite re-establishing epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue, a failure at the microvascular level known as no-reflow (NR). NR has been reported to occur in up to 60% of STEMI patients with optimal coronary vessel reperfusion. When it does occur, it significantly attenuates the beneficial effect of reperfusion therapy, leading to poor outcomes. The pathophysiology of NR is complex and incompletely understood. Many phenomena are known to contribute to NR, including leukocyte infiltration, vasoconstriction, activation of inflammatory pathways and cellular oedema. Vascular damage and haemorrhage may also play important roles in the establishment of NR. In this review, we describe the pathophysiological mechanisms of NR and the tools available for diagnosing it. We also describe the microvasculature and the endothelial mechanisms involved in NR, which may provide relevant therapeutic targets for reducing NR and improving the prognosis for patients.

Performance of CMR Methods for Differentiating Acute From Chronic MI

OBJECTIVES

The purpose of this study was to assess the performance of cardiac magnetic resonance (CMR) methods for discriminating acute from chronic myocardial infarction (MI).

BACKGROUND

Although T2-weighted CMR is thought to be accurate in differentiating acute from chronic MI, few studies have reported on diagnostic accuracy, and these generally compared extremes in infarct age (e.g., <1 week old vs. more than 6 months old) and did not evaluate other CMR methods that could be informative.

METHODS

A total of 221 CMR studies were performed at various time points after ST-segment elevation myocardial infarction in 117 consecutive patients without a history of MI or revascularization enrolled prospectively at 2 centers. Imaging markers of acute MI (<1 month) were T2 hyperintensity on double inversion recovery turbo spin echo (DIR-TSE) images, microvascular obstruction (MO) on delayed-enhancement CMR, and focally increased end-diastolic wall thickness (EDWT) on cine-CMR.

RESULTS

The prevalence of T2-DIR-TSE hyperintensity decreased with infarct age but remained substantial up to 6 months post-MI. In contrast, the prevalence of both MO and increased EDWT dropped sharply after 1 month. T2-DIR-TSE sensitivity, specificity, and accuracy for identifying acute MI were 88%, 66%, and 77% compared with 73%, 97%, and 85%, respectively, for the combination of MO or increased EDWT. On multivariable analysis, persistence of T2-hyperintensity in intermediate-age infarcts (1 to 6 months old) was predicted by larger infarct size, diabetes, and better T2-DIR-TSE image quality score. For infarct size ≥ 10% of the left ventricle, a simple algorithm incorporating all CMR components allowed classification of infarct age into 3 categories (<1 month old, 1 to 6 months old, and ≥ 6 months old) with 80% (95% confidence interval: 73% to 87%) accuracy.

CONCLUSIONS

T2-DIR-TSE hyperintensity is specific for infarcts <6 months old, whereas MO and increased EDWT are specific for infarcts <1 month old. Incorporating multiple CMR markers of acute MI and their varied longevity leads to a more precise assessment of infarct age.

The REFLO-STEMI trial comparing intracoronary adenosine, sodium nitroprusside and standard therapy for the attenuation of infarct size and microvascular obstruction during primary percutaneous coronary intervention: study protocol for a randomised controlled trial

BACKGROUND

Microvascular obstruction (MVO) secondary to ischaemic-reperfusion injury is an important but underappreciated determinant of short- and longer-term outcome following percutaneous coronary intervention (PCI) treatment of ST-elevation myocardial infarction (STEMI). Several small studies have demonstrated a reduction in the degree of MVO utilising a variety of vasoactive agents, with adenosine and sodium nitroprusside (SNP) being most evaluated. However, the evidence base remains weak as the trials have had variable endpoints, differing drug doses and delivery. As such, the results regarding benefit are conflicting.

METHODS

The REperfusion Facilitated by LOcal adjunctive therapy in STEMI (REFLO-STEMI) trial is a multicentre, prospective, randomised, controlled, open label, study with blinded endpoint analysis: Patients presenting within 6 h of onset of STEMI and undergoing planned primary PCI (P-PCI) with TIMI 0/1 flow in the infarct-related artery (IRA) and no significant bystander coronary artery disease on angiography, are randomised into one of three groups: PCI with adjunctive pharmacotherapy (intracoronary adenosine or SNP) or control (standard PCI). All receive Bivalirudin anticoagulation and thrombus aspiration. The primary outcome is infarct size (IS) (determined as a percentage of total left ventricular mass) measured by cardiac magnetic resonance imaging (CMRI) undertaken at 48 to 72 h post P-PCI. Secondary outcome measures include MVO (hypoenhancement within infarct core) on CMRI, angiographic markers of microvascular perfusion and MACE during 1-month follow-up. The study aims to recruit 240 patients (powered at 80% to detect a 5% absolute reduction in IS).

DISCUSSION

The REFLO-STEMI study has been designed to address the weaknesses of previous trials, which have collectively failed to demonstrate whether adjunctive pharmacotherapy with adenosine and/or SNP can reduce measures of myocardial injury (infarct size and MVO) and improve clinical outcome, despite good basic evidence that they have the potential to attenuate this process. The REFLO-STEMI study will be the most scientifically robust trial to date evaluating whether adjunctive therapy (intracoronary adenosine or SNP following thrombus aspiration) reduces CMRI measured IS and MVO in patients undergoing P-PCI within 6 h of onset of STEMI.

TRIAL REGISTRATION

Trial registered 20th November 2012: ClinicalTrials.gov Identifier NCT01747174.

Acute myocardial infarction: early CT aspects of myocardial microcirculation obstruction after percutaneous coronary intervention

OBJECTIVE

To evaluate the capabilities of delayed enhanced multidetector CT (DE-MDCT), performed immediately after percutaneous coronary intervention (PCI), in predicting myocardial microvascular obstruction (MVO) formation assessed by delayed enhanced MRI (DE-MRI).

METHODS

Thirty-two patients presenting with a primary acute myocardial infarction, successfully recanalised by PCI, underwent a DE-MDCT immediately after PCI and a DE-MRI within 1 week. The left ventricle was split into 64 subsegments, rated as "healthy", "infarcted" or "MVO" on DE-MRI. Their mean density was measured on DE-MDCT and calculated relative to the patient's mean healthy myocardium density. Hypoenhanced DE-MDCT subsegments, termed "CT early MVO", were also recorded. Sensitivity and specificity of DE-MDCT for MRI-assessed "MVO" subsegments detection was calculated for mean CT relative density (threshold determined from a ROC analysis), "CT early MVO" and both.

RESULTS

Mean CT relative density was higher in MRI-assessed "MVO" than in "infarcted" and "healthy" subsegments (1.82 ± 0.46, 1.43 ± 0.36 and 1.0 ± 0.13 respectively; P < 0.001) leading to a sensitivity and specificity of 94.3 % and 89.2 % for a cutoff of 1.36. Sensitivity and specificity were respectively 16.9 % and 99.8 % for "CT early MVO" and 95.3 % and 89.3 % when considering the two patterns.

CONCLUSION

DE-MDCT, performed immediately after PCI, allows for an accurate prediction of MVO formation.

KEY POINTS

• Myocardial microvascular obstruction (MVO) is an important prognostic sequel following myocardial infarction. • MVO can be accurately predicted by multidector CT (MDCT). • Both hypo- and hyperenhanced myocardial areas can be analysed by MDCT. • MDCT may become a useful prognostic tool for acute MI outcome.

Secretome of apoptotic peripheral blood cells (APOSEC) attenuates microvascular obstruction in a porcine closed chest reperfused acute myocardial infarction model: role of platelet aggregation and vasodilation

Although epicardial blood flow can be restored by an early intervention in most cases, a lack of adequate reperfusion at the microvascular level is often a limiting prognostic factor of acute myocardial infarction (AMI). Our group has recently found that paracrine factors secreted from apoptotic peripheral blood mononuclear cells (APOSEC) attenuate the extent of myocardial injury. The aim of this study was to determine the influence of APOSEC on microvascular obstruction (MVO) in a porcine AMI model. A single dose of APOSEC was intravenously injected in a closed chest reperfused infarction model. MVO was determined by magnetic resonance imaging and cardiac catheterization. Role of platelet function and vasodilation were monitored by means of ELISA, flow cytometry, aggregometry, western blot and myographic experiments in vitro and in vivo. Treatment of AMI with APOSEC resulted in a significant reduction of MVO. Platelet activation markers were reduced in plasma samples obtained during AMI, suggesting an anti-aggregatory capacity of APOSEC. This finding was confirmed by in vitro tests showing that activation and aggregation of both porcine and human platelets were significantly impaired by co-incubation with APOSEC, paralleled by vasodilator-stimulated phosphoprotein (VASP)-mediated inhibition of platelets. In addition, APOSEC evidenced a significant vasodilatory capacity on coronary arteries via p-eNOS and iNOS activation. Our data give first evidence that APOSEC reduces the extent of MVO during AMI, and suggest that modulation of platelet activation and vasodilation in the initial phase after myocardial infarction contributes to the improved long-term outcome in APOSEC treated animals.

Predicting the no-reflow phenomenon following successful percutaneous coronary intervention

In the setting of acute myocardial infarction, early and adequate reopening of an infarct-related artery is not necessarily followed by a complete restoration of myocardial perfusion. This condition is usually defined as ‘no-reflow’. The pathophysiology of no-reflow is multifactorial since extravascular compression, microvascular vasoconstriction, embolization during percutaneous coronary intervention, and platelet and neutrophil aggregates are involved. In the clinical arena, angiographic findings and easily available clinical parameters can predict the risk of no-reflow. More recently, several studies have demonstrated that biomarkers, especially those related to the pathogenetic components of no-reflow, could also have a prognostic role in the prediction and in the full understanding of the multiple mechanisms of this phenomenon. Thus, in this article, we investigate the role of several biomarkers on admission in predicting the occurrence of no-reflow following successful percutaneous coronary intervention.

Cardiac injuries in blunt chest trauma

Blunt chest traumas are a clinical challenge, both for diagnosis and treatment. The use of cardiovascular magnetic resonance can play a major role in this setting. We present two cases: a 12-year-old boy and 45-year-old man. Late gadolinium enhancement imaging enabled visualization of myocardial damage resulting from the trauma.

Myocardial no-reflow in humans

In a variable proportion of patients presenting with ST-segment elevation myocardial infarction, ranging from 5% to 50%, primary percutaneous coronary intervention achieves epicardial coronary artery reperfusion but not myocardial reperfusion, a condition known as no-reflow. Of note, no-reflow is associated with a worse prognosis at follow-up. The phenomenon has a multifactorial pathogenesis including: distal embolization, ischemia-reperfusion injury, and individual predisposition of coronary microcirculation to injury. Moreover, it is spontaneously reversible in some patients, thus suggesting that it might be amenable to treatment also when we fail to prevent it. Several recent studies have shown that biomarkers and other easily available clinical parameters can predict the risk of no-reflow and can help in the assessment of the multiple mechanisms of the phenomenon. Several therapeutic strategies have been tested for the prevention and treatment of no-reflow. In particular, thrombus aspiration before stent implantation prevents distal embolization and has been recently shown to improve myocardial perfusion and clinical outcome as compared with the standard procedure. However, it is conceivable that the relevance of each pathogenetic component of no-reflow is different in different patients, thus explaining the occurrence of no-reflow despite the use of mechanical thrombus aspiration. Thus, in this review article, for the first time, we propose a personalized management of no-reflow on the basis of the assessment of the prevailing mechanisms of no-reflow operating in each patient.

Coronary no-reflow phenomenon: from the experimental laboratory to the cardiac catheterization laboratory

Coronary no-reflow occurs commonly during acute percutaneous coronary intervention, particularly in patients with acute myocardial infarction and those with degenerated vein grafts. It is associated with a guarded prognosis, and thus needs to be recognized and treated promptly. The pathophysiology originates during the ischemic phase and is characterized by localized and diffuse capillary swelling and arteriolar endothelial dysfunction. In addition, leukocytes become activated and are attracted to the lumen of the capillaries, exhibit diapedesis and may contribute to cellular and intracellular edema and clogging of vessels. At the moment of perfusion, the sudden rush of leukocytes and distal atheroemboli further contributes to impaired tissue perfusion. Shortening the door-to-balloon time, use of glycoprotein IIb/IIIa platelet receptor inhibitors and distal protection devices are predicted to limit the development of no-reflow during percutaneous interventions. Distal intracoronary injection of verapamil, nicardipine, adenosine, and nitroprusside may improve coronary flow in the majority of patients. Hemodynamic support of the patient may be needed in some cases until coronary flow improves.

Ultrasonic imaging of molecular targets

Today nuclear medicine is the only modality that is clinically successful in molecular imaging. However, other modalities compete with its excellent sensitivity in imaging molecular targets. In the last 10 years ultrasound imaging has shown the potential to provide sufficiently high sensitivity for the molecular imaging of vascular targets. These advances are based on the joint development of microbubble contrast media and the methods to image them with high sensitivity. Ultrasound-contrast-enhanced imaging strategies make use of the specific physical properties of microbubbles such as resonance, nonlinear oscillation, and collapse. The size of microbubbles limits their use to the vascular space. Thus, the main applications of ultrasound for molecular imaging are inflammation, thrombi, and angiogenesis, for which successful contrast enhancement has been achieved in animal models. Main molecular targets used to date include selectins, alpha(v)beta(3) or alpha(5)beta(1) integrins, glycoprotein (GP) IIb/IIIa, intracellular adhesion molecule ICAM-1, and vascular endothelial growth factor receptor VEGFR2. Results from animal studies indicate that ultrasound could play a major role in vascular molecular imaging for diagnosis and treatment monitoring. Additional effects of insonified microbubbles (e.g., opening of the blood-brain barrier or increased transfection efficiency in gene therapy) are attributed to the transient opening of cell membranes known as "sonoporation" and demonstrate further potential for integrated diagnosis and therapy.

Imaging of the heart with computed tomography

Imaging of the heart with computed tomography (CT) was already introduced in the 1980Is and has meanwhile entered clinical routine as a consequence of the rapid evolution of CT technology during the last decade. In this review article, we give an overview on the technology and clinical performance of different CT-scanner generations used for cardiac imaging, such as Electron Beam CT (EBCT), single-slice CT und multi-detector row CT (MDCT) with 4, 16 and 64 simultaneously acquired slices. We identify the limitations of current CT-scanners, indicate potential of improvement and discuss alternative system concepts such as CT with area detectors and dual source CT (DSCT).

Cardiovascular diseases as target for imaging

Recent pathophysiological findings have lead to new concepts to identify patients at risk for cardiovascular disease using systemic serum markers or new imaging methodology. New probe technology and progress in imaging techniques have set the base for development of molecular imaging concepts in the cardiovascular systems. The aim of these new imaging techniques is the detection of active biological processes in cardiovascular systems combining specific probes with contrast agents for MRI, SPECT or PET. There are promising strategies mostly in preclinical tests, which will prove clinical applicability in the near future.

Structural and functional imaging by MRI

Magnetic resonance imaging is one of the most exciting techniques for noninvasive molecular imaging of the cardiovascular system. The article will describe challenges, solutions and results of magnetic resonance plaque imaging ex-vivo, in the experimental animal and in patients.

Imaging of stem cells using MRI

The administration of exogenous stem cells offers promise to regenerate many damaged organs. However, failures of these cellular therapies could be related to many issues, such as the type of stem cell, the dose of cellular therapeutic, dosing regime, and mode of delivery. The recent ability to directly label stem cells with magnetic resonance (MR) contrast agents provides a simple, straight-forward manner to monitor accurate cell delivery and track stem cells non-invasively in a serial manner. Provided here is an overview of the currently available MR-labeling methods, including direct non-specific labeling with contrast agents, indirect specific labeling with contrast agents, labeling with MRI reporter genes, and fluorine hot spot labeling. Several of these approaches have now been applied successfully in preclinical animal models of cardiovascular disease. Once properly implemented, future clinical trials may benefit greatly from imaging stem cells with MRI.

Detection of left ventricular thrombus by delayed-enhancement cardiovascular magnetic resonance prevalence and markers in patients with systolic dysfunction

OBJECTIVES

This study sought to assess the prevalence and markers of left ventricular (LV) thrombus among patients with systolic dysfunction.

BACKGROUND

Prior studies have yielded discordant findings regarding prevalence and markers of LV thrombus. Delayed-enhancement cardiovascular magnetic resonance (DE-CMR) identifies thrombus on the basis of tissue characteristics rather than just anatomical appearance and is potentially highly accurate.

METHODS

Prevalence of thrombus by DE-CMR was determined in 784 consecutive patients with systolic dysfunction (left ventricular ejection fraction [LVEF] <50%) imaged between July 2002 and July 2004. Patients were recruited from 2 separate institutions: a tertiary-care referral center and an outpatient clinic. Comparison to cine-cardiovascular magnetic resonance (CMR) was performed. Follow-up was undertaken for thrombus verification via pathology evaluation or documented embolic event within 6 months after CMR. Clinical and imaging parameters were assessed to determine risk factors for thrombus.

RESULTS

Among this at-risk population (age 60 +/- 14 years; LVEF 32 +/- 11%), DE-CMR detected thrombus in 7% (55 patients) and cine-CMR in 4.7% (37 patients, p < 0.005). Follow-up was consistent with DE-CMR as a better reference standard than cine-CMR, including 100% detection among 5 patients with thrombus verified by pathology (cine-CMR, 40% detection), and logistic regression analysis testing the contributions of DE-CMR and cine-CMR simultaneously, which showed that only the presence of thrombus by DE-CMR was associated with follow-up end points (p < 0.005). Cine-CMR generally missed small intracavitary and small or large mural thrombus. In addition to traditional indices such as low LVEF and ischemic cardiomyopathy, multivariable analysis showed that increased myocardial scarring, an additional parameter available from DE-CMR, was an independent risk factor for thrombus.

CONCLUSIONS

In a broad cross section of patients with systolic dysfunction, thrombus prevalence was 7% by DE-CMR and included small intracavitary and small or large mural thrombus missed by cine-CMR. Prevalence increased with worse LVEF, ischemic etiology, and increased myocardial scarring.

No-reflow phenomenon in cardiac MRI: diagnosis and clinical implications

OBJECTIVE

The purposes of this study were to depict the first-pass, delayed contrast enhancement and regional myocardial wall motion abnormalities of no-reflow phenomenon MRI and to review the major mechanisms and significance of this phenomenon in the clinical setting.

CONCLUSION

Contrast-enhanced MRI is a useful noninvasive technique for determining the presence of microvascular obstruction. No-reflow phenomenon has important prognostic implications, and knowledge of the physiologic mechanism is important to understanding the distribution patterns of enhancement in correlation with the underlying pathologic process.

[Contribution of cardiac MRI in the etiologic diagnosis of chest pain syndrome with a normal angiographic aspect of the coronary arteries]

The etiologic diagnosis of chest pain with elevation of specific cardiac enzymes, repolarization abnormalities and a normal angiographic aspect of the coronary arteries is difficult. In this situation, the role of cardiac MRI is growing, frequently allowing to precise the etiology of the chest pain. We present a literature review concerning the semiology of the cardiac MRI in the three main involved etiologies: myocarditis, takotsubo syndrome, and myocardial ischemia with a normal angiographic aspect of the coronary arteries.

Utility of cardiac MRI in guiding revascularization therapy in unprotected left main stenosis: a case report

Decision to select unprotected left main (ULM) stenting versus coronary artery bypass grafting surgery (CABG) depends on a multiplicity of factors, one of the most critical of which is myocardial viability. Delayed enhancement cardiac magnetic resonance (CMR) imaging has emerged as a useful means of comprehensively evaluating viable myocardium in postmyocardial infarct patients who require further revascularization. We present a patient with ULM stenosis in whom CMR imaging assisted in the decision to perform percutaneous coronary intervention over CABG.