Images in cardiovascular medicine. Magnetic resonance imaging of a posttraumatic myocardial infarction and ventricular septal defect with a closure device in place.
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Adolescent↗
Biomedical subjects
Charles B Higgins
Publications and source records attributed to Charles B Higgins.
Guidelines for training in Cardiovascular Magnetic Resonance (CMR).
These "Guidelines for Training in Cardiovascular Magnetic Resonance" were developed by the Clinical Practice Committee of the Society for Cardiovascular Magnetic Resonance (SCMR) and approved by the SCMR Board of Trustees.
Cardiology↗
Discrimination of myocardial acute and chronic (scar) infarctions on delayed contrast enhanced magnetic resonance imaging with intravascular magnetic resonance contrast media.
OBJECTIVES: The purpose of this study was to examine the potential of intravascular gadolinium (Gd)-chelates in discriminating acute from chronic myocardial infarctions (MIs). BACKGROUND: A potential limitation of delayed contrast enhanced magnetic resonance imaging with standard extracellular Gd-chelates is its inability to distinguish acute from chronic MIs. METHODS: Eight pigs with MIs were studied at 3 days and 8 weeks. Inversion recovery gradient echo (IR-GRE), T(1)-turbo spin echo (TSE), and T(2)-TSE images were acquired before and after administration of intravascular and extracellular Gd-chelates. Triphenyltetrazolium chloride (TTC) was used to delineate infarctions at postmortem. Masson's trichrome and Biotinylated Bandeiria simplicifolia Isolectin B4 stains were used to characterize scarred myocardium. Analysis of variance was used to compare signal intensity (SI) ratios and determine differences in infarct extent. RESULTS: The intravascular agent produced differential enhancement of acute infarctions at 3 days (SI ratio 5.8 +/- 1.3) but not at 8 weeks (1.6 +/- 0.4, p < 0.01). The extracellular agent provided differential enhancement of both acute (SI ratio 7.7 +/- 1.4) and chronic (7.5 +/- 0.9) infarctions. The extents of enhanced regions in acute infarctions were not different after intravascular (16.0 +/- 1.3%) or extracellular (17.1 +/- 1.7%) agents; at 8 weeks the extent of extracellular enhanced and TTC regions were smaller (13.2 +/- 1.4% and 12.0 +/- 1.5%, respectively). Masson's trichrome stain demonstrated dense scar tissue, signaling the complete healing of infarction. The vascular stain showed that scar tissue contained fewer microvessels oriented in a haphazard array. CONCLUSIONS: The combination of intravascular and extracellular Gd-chelates discriminates acute from chronic infarctions on delayed images. This double contrast agent approach can be used to determine the age and extent of infarctions.
Animals↗
MR guidance of targeted injections into border and core of scarred myocardium in pigs.
PURPOSE: To use (a) dysprosium-based contrast agent (sprodiamide) to confirm the site of myocardial injection and (b) T1-enhancing magnetic resonance (MR) contrast media to mark the myocardial target and T2*-enhancing contrast media to demonstrate injection sites in the margins or core of infarction on delayed contrast-enhanced images. MATERIALS AND METHODS: Approval of the institutional committee on animal research was obtained. A phantom and six pigs subjected to chronic infarction (8 weeks) underwent MR-guided experiments. At inversion-recovery gradient-echo imaging, gadoterate meglumine (0.1 mmol/kg) was intravenously administered to delineate scar tissue. A catheter fitted with multiple receiver coils was used to visualize catheter navigation and injection sites. A steady-state free precession (balanced fast field-echo) sequence was used for MR fluoroscopy. A high-resolution multiphase balanced gradient-echo cine MR sequence was used after intramyocardial deposition of sprodiamide. The border and core of scarred myocardium were characterized histopathologically. The 95% confidence interval (CI) was used to demonstrate the range, extent of hyperenhanced and hypoenhanced regions after contrast media administration. RESULTS: In the phantom and in vivo, the actively guided catheter produced a high signal intensity at the terminal portion of the shaft and tip. Scarred myocardium was recognized as a bright region on gadoterate meglumine-enhanced images. Intramyocardial injection of sprodiamide caused local and persistent signal intensity loss, and the extent was volume dependent on balanced fast field-echo and T2-weighted turbo spin-echo images. At 5 minutes after administration of 0.2, 0.4, and 0.6 mL of sprodiamide, the 95% CIs of the extents of the hypoenhanced regions were 0.08%, 0.23%; 0.27%, 0.51%; and 0.46%, 0.70%, respectively, of left ventricular (LV) surface area (P < .05, paired t test). Failure of intramyocardial injection was confirmed by a brief signal loss of LV chamber blood. CONCLUSION: Sprodiamide allows visualization of injection sites within enhanced infarction. A catheter with integrated receiver coils aided in effective catheter guidance and precise intramyocardial injection.
Animals↗
Meeting highlights of the 9th annual scientific sessions of the society for cardiovascular magnetic resonance: Miami, Florida, January 20-22, 2006.
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Cardiovascular Diseases↗
Phase contrast MR imaging to measure changes in collateral blood flow after stenting of recurrent aortic coarctation: initial experience.
PURPOSE: To assess the feasibility of using phase contrast magnetic resonance (PC-MR) imaging to measure the change in collateral blood flow early after stenting of aortic coarctation. MATERIALS AND METHODS: A total of 10 consecutive patients with coarctation of the aorta underwent MR imaging, X-ray angiography, and stent placement. PC-MR at two sites in the descending aorta was performed before and early after stenting in order to estimate collateral inflow to the descending thoracic aorta. The collateral flow and collateral flow percentage before and after stent placement were compared. RESULTS: Before stenting, the mean proximal aortic flow = 43.9 +/- 14.6 mL/second; mean distal flow = 54.2 +/- 10 mL/second; collateral flow = 10.2 +/- 6.8 mL/second; and collateral flow percentage = 30.1 +/- 27.9%. After stenting, the mean proximal aortic flow = 62.1 +/- 17.9 mL/second; mean distal flow = 60 +/- 19 mL/second; collateral flow = -1.9 +/- 3.7 mL/second; and collateral flow percentage = -3.3 +/- 6.8%. CONCLUSION: PC-MR can be used to measure changes in collateral circulation after stent treatment of coarctation of the aorta.
Adolescent↗
Delivery and assessment of endovascular stents to repair aortic coarctation using MR and X-ray imaging.
PURPOSE: To investigate the utility of MR and X-ray imaging for characterizing aortic coarctation and flow, and guiding the endovascular catheter to place a stent to repair the coarctation. MATERIALS AND METHODS: The descending aorta in eight dogs was looped with elastic band and tightened distal to the subclavian artery. Balanced fast field echo (bFFE) and velocity-encoded cine (VEC) MRI sequences were used for device tracking and measuring aortic flow. A T1-weighted fast-field echo sequence (T1-FFE) was used to visualize the coarctation and roadmap the aorta. Nitinol stents were guided by a nitinol guidewire and placed under MR guidance. RESULTS: Aortic coarctation was visible on MR and X-ray imaging. The procedure success rate was 88%. VEC MRI measured the changes in aortic flow (baseline = 1.3 +/- 0.2, coarctation = 0.2 +/- 0.02, and stent placement = 0.8 +/- 0.1 liters/minute). A significant reduction in iliac blood pressure was measured after coarctation, but it was reversed by stent placement. The stent lumen was visible on X-ray fluoroscopy, but not on MRI. CONCLUSION: Stent deployment to repair aortic coarctation is feasible under MR guidance. The combined use of MR and X-ray imaging is effective for anatomic and functional evaluation of aortic coarctation dilation, which may be crucial for optimal therapy.
Alloys↗
MR evaluation of cardiovascular physiology in congenital heart disease: flow and function.
Cardiovascular magnetic resonance (CMR) has become the method of choice in the evaluation of a number of questions in congenital heart disease. In addition to morphology, modern CMR techniques allow the visualization of function and flow in a temporally resolved manner. Among the pathologies where these methods play a major role are shunts, septal defects, aortic coarctation, anomalies of the pulmonary arteries, and valvular regurgitation. This paper explains the basics of functional and flow encoded CMR and discusses their application in the assessment of several types of congenital heart disease.
Heart↗
Scarred myocardium imposes additional burden on remote viable myocardium despite a reduction in the extent of area with late contrast MR enhancement.
Magnetic resonance imaging (MRI) can simultaneously detect and quantify myocardial dysfunction and shrinkage in contrast-enhanced areas postinfarction. This ability permits the investigation of our hypothesis that transformation of infracted myocardium to scarred tissue imposes additional burdens on peri-infarcted and remote myocardium. Pigs (n = 8) were subjected to reperfused infarction. Gd-DOTA-enhanced inversion recovery gradient echo sequence (IR-GRE) imaging was performed 3 days and 8 weeks postinfarction. Global and regional left ventricular (LV) function was evaluated by cine MRI. Triphenyltetrazolium chloride (TTC) stain was used to delineate infarction while hematoxylin and eosin (H & E) and Masson's trichrome stains were used to characterize remodeled myocardium. Late contrast-enhanced MRIs showed a decrease in the extent of enhanced areas from 17 +/- 2% at 3 days to13 +/- 1% LV mass at 8 weeks. TTC infarction size was 12 +/- 1% LV mass. Cine MRIs showed expansion in dysfunctional area due to unfavorable remodeling, ischemia, or strain. Ejection fraction was reduced in association with increased end-diastolic and end-systolic volumes. Scarred myocardium contained collagen fibers and remodeled thick-walled vessels embedded in collagen. Sequential MRI showed greater LV dysfunction despite the shrinkage in extent of enhanced areas 2 months postinfarction. The integration of late enhancement and cine MRI incorporates anatomical and functional evaluation of remodeled hearts.
Analysis of Variance↗
Meeting highlights of the 8th Annual Scientific Sessions of the Society For Cardiovascular Magnetic Resonance, January 21 to 23, 2005.
Parallel tracks for clinical scientists, basic scientists, and pediatric imagers was the novel approach taken for the highly successful 8th Annual Scientific Sessions of the Society for Cardiovascular Magnetic Resonance, held in San Francisco, California, January 21 to 23, 2005. Attendees were immersed in information on the latest scientific advances in cardiovascular magnetic resonance (CMR) from mice to man and technological advances from systems with field strengths from 0.5 T to 11.7 T. State-of-the-art applications were reviewed, spanning a wide range from molecular imaging to predicting outcome with CMR in large patient populations.
Adult↗
Combined pulmonary stenosis and insufficiency preserves myocardial contractility in the developing heart of growing swine at midterm follow-up.
This study was conducted to determine the effects of chronic combined pulmonary stenosis and pulmonary insufficiency (PSPI) on right (RV) and left ventricular (LV) function in young, growing swine. Six pigs with combined PSPI were studied, and data were compared with previously published data of animals with isolated pulmonary insufficiency and controls. Indexes of systolic function (stroke volume, ejection fraction, and cardiac functional reserve), myocardial contractility (slope of the end-systolic pressure-volume and change in pressure over time-end-diastolic volume relationship), and diastolic compliance were assessed within 2 days of intervention and 3 mo later. Magnetic resonance imaging was used to quantify pulmonary insufficiency and ventricular volumes. The conductance catheter was used to obtain indexes of the cardiac functional reserve, diastolic compliance, and myocardial contractility from pressure-volume relations acquired at rest and under dobutamine infusion. In the PSPI group, the pulmonary regurgitant fraction was 34.3 +/- 5.8%, the pressure gradient across the site of pulmonary stenosis was 20.9 +/- 20 mmHg, and the average RV peak systolic pressure was 70% systemic at 12 wk follow-up. Biventricular resting cardiac outputs and cardiac functional reserves were significantly limited (P < 0.05), LV diastolic compliance significantly decreased (P < 0.05), but RV myocardial contractility significantly enhanced (P < 0.05) compared with control animals at 3-mo follow-up. In the young, developing heart, chronic combined PSPI impairs biventricular systolic pump function and diastolic compliance but preserves RV myocardial contractility.
Aging↗
Balloon sizing and transcatheter closure of acute atrial septal defects guided by magnetic resonance fluoroscopy: assessment and validation in a large animal model.
PURPOSE: To quantitatively assess atrial septal defects (ASDs) with small shunts using MRI followed by transcatheter closure monitored by MR fluoroscopy. MATERIALS AND METHODS: Acute ASDs were created in 14 pigs under x-ray fluoroscopy. Six animals were studied in order to select MR-compatible delivery systems and imaging strategies. ASDs in eight animals were examined with balloon sizing under MR fluoroscopy, flow measurements, and contrast media injections, after which transcatheter closure was performed under MR fluoroscopy. The delivery system was assembled from commercially available materials. RESULTS: The ratio of pulmonary to systemic flow (Qp/Qs) was reduced from 1.23 +/- 0.15 before ASD closure to 1.07 +/- 0.11 after ASD closure (P < 0.001). In two out of eight animals Qp/Qs was close to 1.0 before closure despite the presence of defects >15 mm. The ASDs were measurable with MR balloon sizing in all of the animals. Balloon sizing was identical with MR (16.9 +/- 2.3 mm) and x-ray fluoroscopy (17.1 +/- 1.3 mm). The in-house-assembled delivery system allowed successful placement of closure devices under MR guidance. CONCLUSION: Assessment and closure of small shunts with MR fluoroscopy is feasible. A barrier to the rapid implementation of transcatheter closure in patients is uncertainty about the MR safety of guidewires and device delivery systems.
Acute Disease↗
Myocardial blood flow in patients with dilated cardiomyopathy: quantitative assessment with velocity-encoded cine magnetic resonance imaging of the coronary sinus.
PURPOSE: To quantify global myocardial perfusion using magnetic resonance imaging (MRI) in patients with heart failure due to idiopathic dilated cardiomyopathy (IDC) and to compare myocardial perfusion and microvascular reactivity with healthy subjects. MATERIALS AND METHODS: A total of 19 subjects (healthy volunteers (N = 12) and IDC patients (N = 7)) were studied using cine MRI to measure left ventricular (LV) mass and a velocity-encoded cine MRI technique to measure coronary sinus flow at rest and after dipyridamole-induced hyperemia. Absolute values of total myocardial blood flow (MBF) were calculated from coronary sinus flow and LV mass. RESULTS: At baseline, MBF was not significantly different in patients with IDC (0.48 +/- 0.07 mL/minute/g) and healthy subjects (0.55 +/- 0.19 mL/minute/g, P= 0.41). After dipyridamole administration, MBF in IDC patients increased to a level significantly less than that in normal volunteers (1.05 +/- 0.35 mL/minute/g vs. 1.99 +/- 1.05 mL/minute/g, P < 0.05). Consequently, MBF reserve was impaired in patients with IDC (2.19 +/- 0.77) compared to that in healthy subjects (3.51 +/- 1.29, P < 0.05). A moderate correlation was found between MBF reserve and LV ejection fraction (r = 0.48, P < 0.05). CONCLUSION: MBF reserve is reduced in patients with IDC, indicating that coronary microcirculatory flow is impaired. This integrated MRI approach allows quantitative measurement of global MBF in humans and may have the potential to study the effects of pharmacological interventions on myocardial perfusion.
Adult↗
Endovascular interventional MRI.
MR guidance has been used recently to navigate endovascular catheters and deliver stents in large (aorta and pulmonary) and small (coronary, renal, and femoral) arteries, place ASD closure devices, deliver pulmonary valve stents, guide cardiac RF ablations, and perform intramyocardial injections. However, MR visualization of a stent lumen is still a problem and requires more attention. Because of technical limitations and safety concerns associated with the prototype devices used, limited numbers of clinical studies have been performed. Considerable development is necessary to overcome the challenges and take advantage of the benefits that MR has to offer for endovascular interventions. In this article we review the current state of the art and address the topic partly by referring to our own experiments and presenting our recent illustrations.
Cardiac Catheterization↗
Long-term oral treatment with nicorandil prevents the progression of left ventricular hypertrophy and preserves viability.
Left ventricular (LV) hypertrophy and myocardial infarction play important roles in the progressive LV dysfunction. We hypothesized that the potassium-channel opener and nitrate-like vasodilator nicorandil prevents the development of LV hypertrophy and preserves myocardial viability. Twenty-four rats were subjected to aortic stenosis for 8 weeks to produce LV hypertrophy and assigned to non-treated and nicorandil-treated (3 mg/kg/d) groups. A third group (n = 12) without stenosis or treatment served as control. All 36 animals were subjected to reperfused infarction by 25-minute occlusion of the left coronary artery followed by 3 hours of reperfusion. Spin-echo magnetic resonance (MR) images were acquired to measure infarction size, LV mass, volumes, ejection fraction, and wall thickness. A necrosis-specific contrast agent, Gadophrin-3, was used to delineate necrotic myocardium. Aortic and LV pressures were measured invasively. At postmortem, LV mass and infarction size were determined and compared with MR findings. Nicorandil prevented the development of LV hypertrophy. Infarction size of nicorandil-treated animals was similar to control animals. Non-treated animals with aortic banding had higher LV mass (P < 0.001), lower ejection fraction (P = 0.006), and larger infarction size (P < 0.001) than treated and control animals. MR and postmortem data showed close agreement. Nicorandil therapy prevented the development of cardiac hypertrophy and protected myocardium against ischemia.
Administration, Oral↗
Gadomer-enhanced MR imaging in the detection of microvascular obstruction: alleviation with nicorandil therapy.
PURPOSE: To evaluate Gadomer-enhanced magnetic resonance (MR) imaging in the quantification of small microvascular obstruction regions and determine if nicroandil alleviates the formation of microvascular obstruction. MATERIALS AND METHODS: Approval of the institutional committee on animal research was obtained, and this study complied with guidelines for care and use of animals. Rats underwent coronary artery occlusion and reperfusion. After 24 hours, Gadomer-enhanced T1-weighted spin-echo MR imaging was used to define microvascular obstruction in animals in control and nicorandil groups. Sequential MR images obtained at two midventricular levels were acquired to measure microvascular obstruction and ischemically injured regions and monitor diffusive and/or convective transport of Gadomer in microvascular obstruction regions. Two investigators working in consensus and using threshold signal intensity measured differentially enhanced regions. Left-ventricular (LV) end-systolic and end-diastolic MR images obtained at the same two midventricular levels were used to measure regional wall thickening and systolic reduction in LV relative volumes. Agreement and correlation between MR imaging and postmortem data were determined with Bland-Altman and linear regression analyses. Animals were sacrificed 3 minutes after intravenous injection of blue dye. RESULTS: On Gadomer-enhanced MR images, two differentially enhanced regions were observed in ischemically injured myocardium, namely, the hypoenhanced region and the surrounding hyperenhanced region. Hypoenhanced regions at MR imaging and unstained regions at blue dye administration were identical 3 minutes after administration (17% +/- 1 and 17% +/- 2; P = .6; r = 0.98). In the control group, Gadomer provided a prolonged imaging window (eg, 6 minutes) for accurately quantifying small microvascular obstruction regions. Microvascular obstruction was observed in all animals in the control group and 27% of animals in the nicorandil group. Microvascular obstruction regions were smaller in the nicorandil group (eg, 3% +/- 1) than in the control group (eg, 17% +/- 2) (P < .001). Hyper- and hypoenhanced regions were also smaller (eg, 20% +/- 2) in rats in the nicorandil group than in those in the control group (37% +/- 4, P < .001). Improvement in LV function in the nicorandil group is likely related to alleviation and reduction in infarct size. CONCLUSION: Gadomer-enhanced MR imaging can be used to quantify small microvascular obstruction regions 24 hours after reperfusion. Intravenous therapy with nicorandil reduces formation of microvascular obstruction regions.
Animals↗
Imaging findings in Takayasu's arteritis.
OBJECTIVE: The objective of our study was to evaluate the clinical usefulness of cross-sectional imaging for establishing the diagnosis of Takayasu's arteritis (TA), an inflammatory vascular disorder that produces arterial stenoses and aneurysms primarily involving the thoracoabdominal aorta and its branches and the pulmonary arteries. CONCLUSION: CT and MRI findings of TA include vascular wall thickening and enhancement early in the disease, and arterial stenoses, occlusions, and aneurysms later in the disease. Cross-sectional imaging is useful for establishing the diagnosis of TA and for showing response to nonsurgical therapy or for planning a surgical intervention.
Adult↗
Magnetic resonance imaging-guided transcatheter implantation of a prosthetic valve in aortic valve position: Feasibility study in swine.
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Aortic Valve↗