Remodeling of Carotid Arteries Detected with MR Imaging: Atherosclerosis Risk in Communities Carotid MRI Study

OBJECTIVES: To determine the extent of thickening of the carotid arterial walls that may be accommodated by outward remodeling.

METHODS: Institutional review board approval was obtained at each participating site, and informed consent was obtained from each participant. All study sites conducted this study in compliance with HIPAA requirements. A total of 2066 participants (age range, 60-85 years) from the Atherosclerosis Risk in Communities (ARIC) study were enrolled in the ARIC Carotid MRI Study. Maximum wall thickness and luminal area were measured with gadolinium-enhanced magnetic resonance (MR) imaging in both common carotid arteries (CCAs) and in one internal carotid artery (ICA) 2 mm above the flow divider. Complete data were available for 1064 ICAs and 3348 CCAs. The association of maximum wall thickness with lumen area was evaluated with linear regression, and adjustments were made for participant age, sex, race, height, and height squared.

RESULTS: In the ICA, lumen area was relatively constant across patients with a wall thickness of 1.38 mm or less. In patients with a wall thickness of more than 1.38 mm, however, lumen area decreased linearly as wall thickness increased. Wall area represented a median of 61.9% of the area circumscribed by the vessel at a maximum wall thickness of 1.50 mm +/- 0.05 (standard deviation) and 75.4% at a maximum wall thickness of 4.0 mm +/- 0.10. In the CCA, lumen area was preserved across wall thicknesses less than 2.06 mm, representing 99% of vessels.

CONCLUSIONS: Atherosclerotic thickening in the ICA appears to be accommodated for vessels with a maximum wall thickness of less than 1.5 mm. Beyond this threshold, greater thickness is associated with a smaller lumen. The CCA appears to accommodate a wall thickness of less than 2.0 mm. These estimates indicate that the carotid arteries are able to compensate for a greater degree of thickening than are the coronary arteries.

PMID: 20651061

Aortic Stiffness Independently Predicts Exercise Capacity in Hypertrophic Cardiomyopathy: A Multimodality Imaging Study

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Prognostic Significance of Myocardial Fibrosis Quantification by Histopathology and Magnetic Resonance Imaging in Patients With Severe Aortic Valve Disease

OBJECTIVES: Does myocardial fibrosis (MF) in patients with severe aortic valve (AV) disease, assessed by histopathology or contrast-enhanced magnetic resonance imaging (ce-MRI), predict outcomes following surgical AV replacement?

METHODS: Fifty-four patients (mean age 46.8 years, 78% male) with symptomatic severe aortic regurgitation (n = 26) or aortic stenosis (n = 28) were prospectively evaluated. All patients underwent preoperative quantitative assessment of MF by ce-MRI and had myocardial tissue samples obtained during surgery for histopathologic evaluation. Patients were grouped based on degree of MF and were compared to assess for differences in left ventricular (LV) functional improvement and survival postoperatively.

RESULTS: ce-MRI assessment of MF correlated well with histopathology (r = 0.69, p < 0.0001), and the degree of MF was higher in the study group than in normal controls. LV functional changes were evaluated in 25 patients who underwent follow-up MRI; LV mass was decreased and LV ejection fraction (EF) improved (EF 54 ± 10% pre-op vs. 59 ± 14% post-op, p = 0.02). LVEF improvement was inversely related to the degree of pre-op MF. Overall, those who died had more MF, and this increased burden of MF was associated with lower postoperative survival. Finally, on multivariate analysis, the amount of MF, along with advanced age, independently predicted all-cause mortality.

CONCLUSIONS: In patients with severe AV disease, the amount of MF assessed by histopathology or ce-MRI is associated with LV function improvement and mortality. 

PMID: 20633819

Meta-Analysis of the Diagnostic Performance of Stress Perfusion Cardiovascular Magnetic Resonance for Detection of Coronary Artery Disease

OBJECTIVES: Evaluation of the diagnostic accuracy of stress perfusion cardiovascular magnetic resonance for the diagnosis of significant obstructive coronary artery disease (CAD) through meta-analysis of the available data.

METHODS: Original articles in any language published before July 2009 were selected from available databases (MEDLINE, Cochrane Library and BioMedCentral) using the combined search terms of magnetic resonance, perfusion, and coronary angiography; with the exploded term coronary artery disease. Statistical analysis was only performed on studies that: (1) used a [greater than or equal to] 1.5 Tesla MR scanner; (2) employed invasive coronary angiography as the reference standard for diagnosing significant obstructive CAD, defined as a [greater than or equal to] 50% diameter stenosis; and (3) provided sufficient data to permit analysis.

RESULTS: From the 263 citations identified, 55 relevant original articles were selected. Only 35 fulfilled all of the inclusion criteria, and of these 26 presented data on patient-based analysis. The overall patient-based analysis demonstrated a sensitivity of 89% (95% CI: 88-91%), and a specificity of 80% (95% CI: 78-83%). Adenosine stress perfusion CMR had better sensitivity than with dipyridamole (90% (88-92%) versus 86% (80-90%), P = 0.022), and a tendency to a better specificity (81% (78-84%) versus 77% (71-82%), P = 0.065).

CONCLUSIONS: Stress perfusion CMR is highly sensitive for detection of CAD but its specificity remains moderate.

PMID: 20482819

Extent of Late Gadolinium Enhancement Detected by Cardiovascular Magnetic Resonance Correlates With the Inducibility of Ventricular Tachyarrhythmia in Hypertrophic Cardiomyopathy

OBJECTIVES: Myocardial fibrosis is frequently identified in patients with hypertrophic cardiomyopathy (HCM). The aim of this study was to investigate the role of myocardial fibrosis detected by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR) as a potential arrhythmogenic substrate in HCM. We hypothesized that the extent of LGE might be associated with the inducibility of ventricular tachyarrhythmias (VT) during programmed ventricular stimulation (PVS).

METHODS: We evaluated retrospectively LGE CMR of 76 consecutive HCM patients, of which 43 presented with one or more risk factors for sudden cardiac death (SCD) and were therefore clinically classified as high-risk patients. Of these 43 patients, 38 additionally underwent an electrophysiological testing (EP). CMR indices and the extent of LGE, given as the % of LV mass with LGE were correlated with the presence of risk factors for SCD and the results of EP.

RESULTS: High-risk patients had a significant higher prevalence of LGE than low-risk patients (29/43 [67%] versus 14/33 [47%]; p=0.03). Also the % of LV mass with LGE was significantly higher in high-risk patients than in low-risk patients (14% versus 3%, p=0.001, respectively). Of the 38 high- risk patients, 12 had inducible VT during EP. LV function, volumes and mass were comparable in patients with and without inducible VT. However, the % of LV mass with LGE was significantly higher in patients with inducible VT compared to those without (22% versus 10 %, p=0.03). The prevalence of LGE was, however, comparable between HCM patients with and those without inducible VT (10/12 [83%] versus 15/26 [58%]; p=0.12). In the univariate analysis the % of LV mass with LGE and the septal wall thickness were significantly associated with the high-risk group (p= 0.001 and 0.004, respectively). Multivariate analysis demonstrated that the extent of LGE was the only independent predictor of the risk group (p=0.03).

CONCLUSIONS: The extent of LGE in HCM patients correlated with risk factors of SCD and the likelihood of inducible VT. Furthermore, LGE extent was the only independent predictor of the risk group. This supports the hypothesis that the extent of fibrosis may serve as potential arrhythmogenic substrate for the occurrence of VT, especially in patients with clinical risk factors for SCD.

PMID: 20492668

Cost-Effective Diagnostic Cardiovascular Imaging: When Does it Provide Good Value for the Money?

OBJECTIVES: To summarize the results of all original cost-utility analyses (CUAs) in diagnostic cardiovascular imaging (CVI) and characterize those technologies by estimates of their cost-effectiveness.

METHODS: We systematically searched the literature for original CVI CUAs published between 2000 and 2008. Studies were classified according to several variables including anatomy of interest (e.g. cerebrovascular, aorta, peripheral) and imaging modality under study (e.g. angiography, ultrasound). The results of each study, expressed as cost of the intervention to number of quality-adjusted life years saved ratio (cost/QALY) were additionally classified as favorable or not using $20,000, $50,000, and $100,000 per QALY thresholds. The distribution of results was assessed with Chi Square or Fisher exact test, as indicated.

RESULTS: Sixty-nine percent of all cardiovascular imaging CUAs were published between 2000 and 2008. Thirty-two studies reporting 82 cost/QALY ratios were included in the final sample. The most common vascular areas studied were cerebrovascular (n = 9) and cardiac (n = 8). Sixty-six percent (21/32) of studies focused on sonography, followed by conventional angiography and CT (25%, n = 8, each). Twenty-nine (35.4%), 42 (51.2%), and 53 (64.6%) ratios were favorable at WTP $20,000/QALY, $50,000/QALY, and $100,000/QALY, respectively. Thirty (36.6%) ratios compared one imaging test versus medical or surgical interventions; 26 (31.7%) ratios compared imaging to a different imaging test and another 26 (31.7%) to no intervention. Imaging interventions were more likely (P < 0.01) to be favorable when compared to observation, medical treatment or non-intervention than when compared to a different imaging test at WTP $100,000/QALY.

CONCLUSIONS: The diagnostic cardiovascular imaging literature has growth substantially. The studies available have, in general, favorable cost-effectiveness profiles with major determinants relating to being compared against observation, medical or no intervention instead of other imaging tests.

PMID: 20446040

Composition of Carotid Atherosclerotic Plaque Is Associated With Cardiovascular Outcome: A Prognostic Study

OBJECTIVES: Identification of patients at risk for primary and secondary manifestations of atherosclerotic disease progression is based mainly on established risk factors. The atherosclerotic plaque composition is thought to be an important determinant of acute cardiovascular events, but no prospective studies have been performed. The objective of the present study was to investigate whether atherosclerotic plaque composition is associated with the occurrence of future vascular events.

METHODS: Atherosclerotic carotid lesions were collected from patients who underwent carotid endarterectomy and were subjected to histological examination. Patients underwent clinical follow-up yearly, up to 3 years after carotid endarterectomy. The primary outcome was defined as the composite of a vascular event (vascular death, nonfatal stroke, nonfatal myocardial infarction) and vascular intervention. The cumulative event rate at 1-, 2-, and 3-year follow-up was expressed by Kaplan–Meier estimates, and Cox proportional hazards regression analyses were performed to assess the independence of histological characteristics from general cardiovascular risk factors.

RESULTS: During a mean follow-up of 2.3 years, 196 of 818 patients (24%) reached the primary outcome. Patients whose excised carotid plaque revealed plaque hemorrhage or marked intraplaque vessel formation demonstrated an increased risk of primary outcome (risk difference=30.6% versus 17.2%; hazard ratio [HR] with [95% confidence interval]=1.7 [1.2 to 2.5]; and risk difference=30.0% versus 23.8%; HR=1.4 [1.1 to 1.9], respectively). Macrophage infiltration (HR=1.1 [0.8 to 1.5]), large lipid core (HR=1.1 [0.7 to 1.6]), calcifications (HR=1.1 [0.8 to 1.5]), collagen (HR=0.9 [0.7 to 1.3]), and smooth muscle cell infiltration (HR=1.3 [0.9 to 1.8]) were not associated with clinical outcome. Local plaque hemorrhage and increased intraplaque vessel formation were independently related to clinical outcome and were independent of clinical risk factors and medication use.

CONCLUSIONS: The local atherosclerotic plaque composition in patients undergoing carotid endarterectomy is an independent predictor of futurecardiovascular events.

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Microvascular Obstruction: Underlying Pathophysiology and Clinical Diagnosis

Successful restoration of epicardial coronary artery patency after prolonged occlusion might result in microvascular obstruction (MVO) and is observed both experimentally as well as clinically. In reperfused myocardium, myocytes appear edematous and swollen from osmotic overload. Endothelial cell changes usually accompany the alterations seen in myocytes but lag behind myocardial cell injury. Endothelial cells become voluminous, with large intraluminal endothelial protrusions into the vascular lumen, and together with swollen surrounding myocytes occlude capillaries. The infiltration and activation of neutrophils and platelets and the deposition of fibrin also play an important role in reperfusion-induced microvascular damage and obstruction. In addition to these ischemia-reperfusion-related events, coronary microembolization of atherosclerotic debris after percutaneous coronary intervention is responsible for a substantial part of clinically observed MVO. Microvascular flow after reperfusion is spatially and temporally complex. Regions of hyperemia, impaired vasodilatory flow reserve and very low flow coexist and these perfusion patterns vary over time as a result of reperfusion injury. The MVO first appears centrally in the infarct core extending toward the epicardium over time. Accurate detection of MVO is crucial, because it is independently associated with adverse ventricular remodeling and patient prognosis. Several techniques (coronary angiography, myocardial contrast echocardiography, cardiovascular magnetic resonance imaging, electrocardiography) measuring slightly different biological and functional parameters are used clinically and experimentally. Currently there is no consensus as to how and when MVO should be evaluated after acute myocardial infarction.

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Cardiac MRI in Pulmonary Artery Hypertension: Correlations Between Morphological and Functional Parameters and Invasive Measurements

OBJECTIVES: To compare cardiac MRI with right heart catheterisation in patients with pulmonary hypertension (PH) and to evaluate its ability to assess PH severity.

METHODS: Forty patients were included. MRI included cine and phase-contrast sequences, study of ventricular function, cardiac cavity areas and ratios, position of the interventricular septum (IVS) in systole and diastole, and flow measurements. We defined four groups according to the severity of PH and three groups according to IVS position: A, normal position; B, abnormal in diastole; C, abnormal in diastole and systole.

RESULTS: IVS position was correlated with pulmonary artery pressures and PVR (pulmonary vascular resistance). Median pulmonary artery pressures and resistance were significantly higher in patients with an abnormal septal position compared with those with a normal position. Correlations were good between the right ventricular ejection fraction and PVR, right ventricular end-systolic volume and PAP, percentage of right ventricular area change and PVR, and diastolic and systolic ventricular area ratio and PVR. These parameters were significantly associated with PH severity.

CONCLUSIONS: Cardiac MRI can help to assess the severity of PH.

PMID: 20094890

Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: Proposed Modification of the Task Force Criteria

OBJECTIVES: In 1994, an International Task Force proposed criteria for the clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) that facilitated recognition and interpretation of the frequently nonspecific clinical features of ARVC/D. This enabled confirmatory clinical diagnosis in index cases through exclusion of phenocopies and provided a standard on which clinical research and genetic studies could be based. Structural, histological, electrocardiographic, arrhythmic, and familial features of the disease were incorporated into the criteria, subdivided into major and minor categories according to the specificity of their association with ARVC/D. At that time, clinical experience with ARVC/D was dominated by symptomatic index cases and sudden cardiac death victims-the overt or severe end of the disease spectrum. Consequently, the 1994 criteria were highly specific but lacked sensitivity for early and familial disease.

METHODS:  Revision of the diagnostic criteria provides guidance on the role of emerging diagnostic modalities and advances in the genetics of ARVC/D.

RESULTS: The criteria have been modified to incorporate new knowledge and technology to improve diagnostic sensitivity, but with the important requisite of maintaining diagnostic specificity. The approach of classifying structural, histological, electrocardiographic, arrhythmic, and genetic features of the disease as major and minor criteria has been maintained. In this modification of the Task Force criteria, quantitative criteria are proposed and abnormalities are defined on the basis of comparison with normal subject data.

CONCLUSIONS: The present modifications of the Task Force Criteria represent a working framework to improve the diagnosis and management of this condition.

PMID: 20172912

Shorter Difference Between Myocardium and Blood Optimal Inversion Time Suggests Diffuse Fibrosis in Dilated Cardiomyopathy

PURPOSE: To find evidence of diffuse fibrosis in dilated cardiomyopathy (DCM) patients by comparing measurements on clinical late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) studies between DCM and healthy subjects.

METHODS: LGE-CMR and the Look-Locker images from 20 DCM patients and 17 healthy controls were analyzed. Blood signal-to-noise ratio (SNR), myocardium SNR, and blood-to-myocardium contrast-to-noise ratio (CNR) were measured on the LGE-CMR images. The optimal inversion time (TI) to null blood and myocardium was determined on the Look-Locker images. The postcontrast T(1) was estimated using a phantom study that correlated optimal TI and heart rate to T(1).

RESULTS: The blood SNR was lower, myocardium SNR was higher, and the blood-to-myocardium CNR was lower (6.6 +/- 0.7 vs. 10.3 +/- 0.9, P = 0.004) on DCM LGE-CMR images as compared to controls. The blood-myocardium optimal TI difference (DeltaTI) was lower (38 +/- 2 msec vs. 55 +/- 3 msec, P < 0.001) in DCM, and the estimated blood-myocardium T(1) difference (DeltaT(1)) (116 +/- 6 msec vs. 152 +/- 8 msec, P = 0.001) was also lower.

CONCLUSIONS: DCM patients have reduced blood-myocardium DeltaTI and DeltaT(1), and lower CNR as compared to controls, suggesting the presence of diffuse fibrosis. This may impact the interpretation of LGE data.

PMID: 19856417

Microvascular Obstruction Remains a Portent of Adverse Remodeling in Optimally-Treated Patients with Left Ventricular Systolic Dysfunction After Acute Myocardial Infarction

OBJECTIVES: Microvascular obstruction (MO) is associated with large acute myocardial infarction (AMI) and lower left ventricular (LV) ejection fraction, and predicts greater remodeling, but whether this effect is abolished by contemporary anti-remodeling therapies is subject to debate. We examined the influence of several infarct characteristics, including MO, on LV remodeling in an optimally-treated post-AMI cohort, using contrast-enhanced cardiac magnetic resonance (ceCMR).

METHODS: 100 patients (mean age 58.9±12 years, 77% male) underwent ceCMR at baseline (~4 days), 12 and 24 weeks. The effects on LV remodeling (i.e. change in LV end-systolic volume index [LVESVi]) of infarct site, transmurality, endocardial extent, and the presence of early and late MO were analyzed.

RESULTS: Mean baseline infarct volume index decreased from 34.0 (21.2) mL/m2 to 20.9 (12.9) mL/m2 at 24 weeks (p<0.001). Infarct site had no influence on remodeling, but greater baseline infarct transmurality (r=0.47, p<0.001) and endocardial extent (r=0.26, p<0.01) were associated with higher LVESVi. Early MO was seen in 69 (69%) of patients and persisted, as late MO, in 56 (56%). Patients with late MO underwent significantly greater remodeling than those without MO (LVESVi +4.1 [13.4] vs. -7.0 [12.7] mL/m2 respectively, p=0.001); those with early MO only displayed an intermediate LVESVi (-4.9 [13.0] mL/m2). Importantly, late MO was seen frequently despite optimal coronary blood flow having been restored at angiography.

CONCLUSIONS: Late MO on pre-discharge ceCMR remains an ominous predictor of adverse LV remodeling despite powerful anti-remodeling therapy, and may be useful in the risk-stratification of survivors of AMI.

PMID: 20348438

Bicuspid Aortic Valve: Four-Dimensional MR Evaluation of Ascending Aortic Systolic Flow Patterns

OBJECTIVES: To use time-resolved three-dimensional phase-contrast magnetic resonance (MR) imaging, also called four-dimensional flow MR imaging, to evaluate systolic blood flow patterns in the ascending aorta that may predispose patients with a bicuspid aortic valve (BAV) to aneurysm.

METHODS: The HIPAA-compliant protocol received institutional review board approval, and informed consent was obtained. Four-dimensional flow MR imaging was used to assess blood flow in the thoracic aorta of 53 individuals: 20 patients with a BAV, 25 patient with a tricuspid aortic valve (TAV), and eight healthy volunteers. The Fisher exact test was used to evaluate the significance of flow patterns differences.

RESULTS: Nested helical flow was seen at peak systole in the ascending aorta of 15 of 20 patients with a BAV but in none of the healthy volunteers or patients with a TAV. This flow pattern was seen both in patients with a BAV with a dilated ascending aorta (n=6) and in those with a normal ascending aorta (n=9), was seen in the absence of aortic stenosis (n=5), and was associated with eccentric systolic flow jets in all cases. Fusion of right and left leaflets gave rise to right-handed helical flow and right-anterior flow jets (n=11), whereas right and noncoronary fusion gave rise to left-handed helical flow with left –posterior flow jets (n=4).

CONCLUSIONS: Four-dimensional flow MR imaging showed abnormal helical systolic flow in the ascending aorta of patients with a BAV, including those without aneurysm or aortic stenosis. Identification and characterization of eccentric flow jets in these patients may help identify those at risk for development of ascending aortic aneurysm.

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Review of Journal of Cardiovascular Magnetic Resonance 2009

There were 56 articles published in the Journal of Cardiovascular Magnetic Resonance in 2009. The editors were impressed with the high quality of the submissions, of which our acceptance rate was about 40%. In accordance with open-access publishing, the articles go on-line as they are accepted with no collating of the articles into sections or special thematic issues. We have therefore chosen to briefly summarise the papers in this article for quick reference for our readers in broad areas of interest, which we feel will be useful to practitioners of cardiovascular magnetic resonance (CMR). In some cases where it is considered useful, the articles are also put into the wider context with a short narrative and recent CMR references. It has been a privilege to serve as the Editor of the JCMR this past year. I hope that you find the open-access system increases wider reading and citation of your papers, and that you will continue to send your quality manuscripts to JCMR for publication.

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Image Fusion of Coronary CT Angiography and Cardiac Perfusion MRI: A Pilot Study

OBJECTIVES: To develop a tool for the image fusion of computed tomography coronary angiography (CTCA) and cardiac magnetic resonance imaging (CMR).

METHODS: Surface representations and volume-rendered images from fused CTCA/CMR data of five patients with significant coronary artery disease (CAD) on CTCA and perfusion deficits on CMR were generated using a newly developed software prototype. The spatial relationship of significant coronary artery stenosis at CTCA and myocardial defects at CMR was evaluated.

RESULTS: Registration of CTCA and CMR images was possible in all patients. The comprehensive three-dimensional visualisation of fused CTCA and CMR data accurately demonstrated the relationship between coronary artery stenoses and myocardial defects in all patients.

CONCLUSIONS: The introduced tool enables image fusion of CTCA and CMR data sets and allows for correct superposition of the coronary arteries derived from CTCA onto the corresponding myocardial segments derived from CMR. The method facilitates the comprehensive assessment of the functionally relevant CAD by the exact allocation of culprit coronary stenoses to corresponding myocardial defects at a low radiation dose.

PMID: 20204639