Norbert Wilke

Utility of Cardiac Magnetic Resonance Imaging in the Diagnosis of Hypertrophic Cardiomyopathy

Background—Two-dimensional echocardiography is currently the standard test for the clinical diagnosis of hypertrophic cardiomyopathy (HCM). The present study was undertaken to determine whether cardiac MRI (CMR) affords greater accuracy than echocardiography in establishing the diagnosis and assessing the magnitude of left ventricular (LV) hypertrophy in HCM. Methods and Results—Forty-eight patients (age 34±16 years) suspected of having HCM (or with a confirmed diagnosis) were imaged by both echocardiography and CMR to assess LV wall thickness in 8 anatomic segments (total n=384 segments) and compared in a blinded fashion. Maximum LV thickness was similar by echocardiography (21.7±9.1 mm) and CMR (22.5±9.6 mm; P=0.21). However, in 3 (6%) of the 48 patients, echocardiography did not demonstrate LV hypertrophy, and CMR identified otherwise undetected areas of wall thickening in the anterolateral LV free wall (17 to 20 mm), which resulted in a new diagnosis of HCM. In the overall study group, compared with CMR, echocardiography also underestimated the magnitude of hypertrophy in the basal anterolateral free wall (by 20±6%; P=0.001), as well as the presence of extreme LV wall thickness (≥30 mm) in 10% of patients (P<0.05). Conclusions—CMR is capable of identifying regions of LV hypertrophy not readily recognized by echocardiography and was solely responsible for diagnosis of the HCM phenotype in an important minority of patients. CMR enhances the assessment of LV hypertrophy, particularly in the anterolateral LV free wall, and represents a powerful supplemental imaging test with distinct diagnostic advantages for selected HCM patients.

Safety of Magnetic Resonance Imaging in Patients With Cardiovascular Devices An American Heart Association Scientific Statement From the Committee on Diagnostic and Interventional Cardiac Catheterization, Council on Clinical Cardiology, and the Council on Cardiovascular Radiology and Intervention: Endorsed by the American College of Cardiology Foundation, the North American Society for Cardiac Imaging, and the Society for Cardiovascular Magnetic Resonance

Advances in magnetic resonance (MR) imaging over the past 2 decades have led to MR becoming an increasingly attractive imaging modality. With the growing number of patients treated with permanent implanted or temporary cardiovascular devices, it is becoming ever more important to clarify safety issues in regard to the performance of MR examinations in patients with these devices. Extensive, although not complete, ex vivo, animal, and clinical data are available from which to generate recommendations regarding the safe performance of MR examination in patients with cardiovascular devices, as well as to ascertain caveats and contraindications regarding MR examination for such patients. Safe MR imaging involves a careful initial patient screening, accurate determination of the permanent implanted or temporary cardiovascular device and its properties, a thoughtful analysis of the risks and benefits of performing the examination at that time, and, when indicated, appropriate physician management and supervision. This scientific statement is intended to summarize and clarify issues regarding the safety of MR imaging in patients with cardiovascular devices.

MR-IMPACT II: Magnetic Resonance Imaging for Myocardial Perfusion Assessment in Coronary artery disease Trial: perfusion-cardiac magnetic resonance vs. single-photon emission computed tomography for the detection of coronary artery disease: a comparative multicentre, multivendor trial

AIMSnPerfusion-cardiac magnetic resonance (CMR) has emerged as a potential alternative to single-photon emission computed tomography (SPECT) to assess myocardial ischaemia non-invasively. The goal was to compare the diagnostic performance of perfusion-CMR and SPECT for the detection of coronary artery disease (CAD) using conventional X-ray coronary angiography (CXA) as the reference standard.nnnMETHODS AND RESULTSnIn this multivendor trial, 533 patients, eligible for CXA or SPECT, were enrolled in 33 centres (USA and Europe) with 515 patients receiving MR contrast medium. Single-photon emission computed tomography and CXA were performed within 4 weeks before or after CMR in all patients. The prevalence of CAD in the sample was 49%. Drop-out rates for CMR and SPECT were 5.6 and 3.7%, respectively (P = 0.21). The primary endpoint was non-inferiority of CMR vs. SPECT for both sensitivity and specificity for the detection of CAD. Readers were blinded vs. clinical data, CXA, and imaging results. As a secondary endpoint, the safety profile of the CMR examination was evaluated. For CMR and SPECT, the sensitivity scores were 0.67 and 0.59, respectively, with the lower confidence level for the difference of +0.02, indicating superiority of CMR over SPECT. The specificity scores for CMR and SPECT were 0.61 and 0.72, respectively (lower confidence level for the difference: -0.17), indicating inferiority of CMR vs. SPECT. No severe adverse events occurred in the 515 patients.nnnCONCLUSIONnIn this large multicentre, multivendor study, the sensitivity of perfusion-CMR to detect CAD was superior to SPECT, while its specificity was inferior to SPECT. Cardiac magnetic resonance is a safe alternative to SPECT to detect perfusion deficits in CAD.

Reduced myocardial perfusion reserve and transmural perfusion gradient in heart transplant arteriopathy assessed by magnetic resonance imaging.

OBJECTIVESnThe goal of this study was to detect transplant arteriopathy (Tx-CHD) by a reduced myocardial perfusion reserve (MPR) and resting endomyocardial/epimyocardial perfusion ratio (Endo/Epi ratio).nnnBACKGROUNDnTransplant arteriopathy often lacks clinical symptoms and is the reason for frequent surveillance angiography in heart transplant (Tx) recipients. Magnetic resonance perfusion imaging (MRPI) allows noninvasive assessment of transmural and selective endomyocardial and epimyocardial perfusion.nnnMETHODSnFifteen healthy volunteers (controls) and three groups (A, B, C) of Tx recipients were included. In controls and patients, MPR (hyperemic/resting perfusion) and Endo/Epi ratio were determined with MRPI after injection of gadolinium-diethylenetriamine pentaacetic acid at rest and during hyperemia (intravenous adenosine). Group A (n = 10) had no left ventricular (LV) hypertrophy and/or prior rejection, while patients in group B (n = 10) had at least one of these characteristics. Patients in group A and B had a normal coronary angiogram and a coronary flow reserve (CFR) of > or =2.5 (CFR = hyperemic/resting blood flow). Group C (n = 7) had Tx-CHD diagnosed by angiography and a reduced CFR (<2.5).nnnRESULTSnIn group C, MPR (1.7 +/- 0.5) and Endo/Epi ratio (1.1 +/- 0.2) were significantly reduced compared with controls (4.2 +/- 0.7 and 1.6 +/- 0.3; both p < 0.0001), group A (3.6 +/- 0.7 and 1.6 +/- 0.2; both p < 0.0001) and B (2.7 +/- 0.9, p < 0.01 and 1.4 +/- 0.1, p < 0.04). Transplant arteriopathy can be excluded by an MPR of >2.3 with sensitivity and specificity of 100% and 85%. If LV hypertrophy and prior rejection are excluded, Tx-CHD can be excluded by an Endo/Epi ratio of >1.3 with 100% and 80%.nnnCONCLUSIONSnMagnetic resonance perfusion imaging detects Tx-CHD by a decreased MPR. After exclusion of LV hypertrophy and prior rejection, resting Endo/Epi ratio alone might be sufficient to indicate Tx-CHD.

Magnetic Resonance Image-Guided Transcatheter Closure of Atrial Septal Defects

Background—Recent developments in cardiac MRI have extended the potential spectrum of diagnostic and interventional applications. The purpose of this study was to test the ability of MRI to perform transcatheter closures of secundum type atrial septal defects (ASD) and to assess ASD size and changes in right cardiac chamber volumes in the same investigation. Methods and Results—In 7 domestic swine (body weight, 38±13 kg), an ASD (Qp:Qs=1.7±0.2) was created percutaneously by balloon dilation of the fossa ovalis. The ASD was imaged and sized by both conventional radiography and MRI. High-resolution MRI of the ASD diameters correlated well with postmortem examination (r =0.97). Under real-time MR fluoroscopy, the introducer sheath was tracked toward the left atrium with the use of novel miniature MR guide wires. The defect was then closed with an Amplatzer Septal Occluder. In all animals, it was possible to track and interactively control the position of the guide wire within the vessels and the heart, including the successful deployment of the Amplatzer Septal Occluder. Right atrial and ventricular volumes were calculated before and after the intervention by using cine-MRI. Both volumes were found to be significantly reduced after ASD closure (P <0.005). Conclusions—These in vivo studies demonstrate that catheter tracking and ASD device closure can be performed under real-time MRI guidance with the use of intravascular antenna guide wires. High-resolution imaging allows accurate determination of ASD size before the intervention, and immediate treatment effects such as changes in right cardiac volumes can also be measured.

Safety of magnetic resonance imaging in patients with cardiovascular devices: An American heart association scientific statement from the committee on diagnostic and interventional cardiac catheterization, council on clinical cardiology, and the council on cardiovascular radiology and intervention

Advances in magnetic resonance (MR) imaging over the past 2 decades have led to MR becoming an increasingly attractive imaging modality. With the growing number of patients treated with permanent implanted or temporary cardiovascular devices, it is becoming ever more important to clarify safety issues in regard to the performance of MR examinations in patients with these devices. Extensive, although not complete, ex vivo, animal, and clinical data are available from which to generate recommendations regarding the safe performance of MR examination in patients with cardiovascular devices, as well as to ascertain caveats and contraindications regarding MR examination for such patients. Safe MR imaging involves a careful initial patient screening, accurate determination of the permanent implanted or temporary cardiovascular device and its properties, a thoughtful analysis of the risks and benefits of performing the examination at that time, and, when indicated, appropriate physician management and supervision. This scientific statement is intended to summarize and clarify issues regarding the safety of MR imaging in patients with cardiovascular devices.

Superior diagnostic performance of perfusion-cardiovascular magnetic resonance versus SPECT to detect coronary artery disease: The secondary endpoints of the multicenter multivendor MR-IMPACT II (Magnetic Resonance Imaging for Myocardial Perfusion Assessment in Coronary Artery Disease Trial)

BackgroundPerfusion-cardiovascular magnetic resonance (CMR) is generally accepted as an alternative to SPECT to assess myocardial ischemia non-invasively. However its performance vs gated-SPECT and in sub-populations is not fully established. The goal was to compare in a multicenter setting the diagnostic performance of perfusion-CMR and gated-SPECT for the detection of CAD in various populations using conventional x-ray coronary angiography (CXA) as the standard of reference.MethodsIn 33 centers (in US and Europe) 533 patients, eligible for CXA or SPECT, were enrolled in this multivendor trial. SPECT and CXA were performed within 4u2009weeks before or after CMR in all patients. Prevalence of CAD in the sample was 49% and 515 patients received MR contrast medium. Drop-out rates for CMR and SPECT were 5.6% and 3.7%, respectively (ns). The study was powered for the primary endpoint of non-inferiority of CMR vs SPECT for both, sensitivity and specificity for the detection of CAD (using a single-threshold reading), the results for the primary endpoint were reported elsewhere. In this article secondary endpoints are presented, i.e. the diagnostic performance of CMR versus SPECT in subpopulations such as multi-vessel disease (MVD), in men, in women, and in patients without prior myocardial infarction (MI). For diagnostic performance assessment the area under the receiver-operator-characteristics-curve (AUC) was calculated. Readers were blinded versus clinical data, CXA, and imaging results.ResultsThe diagnostic performance (= area under ROCu2009=u2009AUC) of CMR was superior to SPECT (pu2009=u20090.0004, nu2009=u2009425) and to gated-SPECT (pu2009=u20090.018, nu2009=u2009253). CMR performed better than SPECT in MVD (pu2009=u20090.003 vs all SPECT, pu2009=u20090.04 vs gated-SPECT), in men (pu2009=u20090.004, nu2009=u2009313) and in women (pu2009=u20090.03, nu2009=u2009112) as well as in the non-infarct patients (pu2009=u20090.005, nu2009=u2009186 in 1–3 vessel disease and pu2009=u20090.015, nu2009=u2009140 in MVD).ConclusionIn this large multicenter, multivendor study the diagnostic performance of perfusion-CMR to detect CAD was superior to perfusion SPECT in the entire population and in sub-groups. Perfusion-CMR can be recommended as an alternative for SPECT imaging.Trial registrationClinicalTrials.gov, Identifier: NCT00977093

Quantitative Magnetic Resonance First-Pass Perfusion Analysis: Inter- and Intraobserver Agreement

Magnetic resonance first-pass (MRFP) imaging awaits longitudinal clinical trials for quantification of myocardial perfusion. The purpose of this study was to assess inter- and intraobserver agreement of this method. Seventeen MRFP studies (14 rest and 3 under adenosine-induced hyperemia) from 14 patients were acquired. Two observers visually graded study quality. Each study was subdivided into eight regions. Both observers analyzed all 17 studies (8 x 17 = 136 regions) for interobserver agreement. Each observer then analyzed 10 of the 17 studies a second time (2 x 8 x 10 = 160 regions) for intraobserver agreement. Signal intensity curves were obtained with Argus software (Siemens, Iselin, NJ). The maximum amplitude of the impulse response function (Rmax) and the change of signal intensity (deltaSImax) of the contrast bolus were determined. Intraclass correlation coefficient was used to determine intra- and interobserver agreement. The quality was good or excellent in 14 studies. Intraobserver agreement of Rmax and deltaSImax were good (0.85 and 0.80, n = 160). Interobserver agreement of Rmax was fair (0.55, n = 136) but improved after exclusion of poor-quality studies (0.88, n = 112). Interobserver agreement of deltaSImax was good (0.73) and improved less than Rmax with study quality (0.83). Interobserver agreement for Rmax in individual myocardial regions before and after exclusion of studies with poor quality changed most markedly in lateral and posterior regions (0.69 and 0.65 vs. 0.97 and 0.94), where signal-to-noise ratios were reduced compared with anteroseptal regions (p < 0.01). Analysis of MRFP images provides good intraobserver agreement. Interobserver agreement of the quantitative perfusion analysis is good under the premise of good image quality.

ASSESSING MYOCARDIAL PERFUSION IN CORONARY ARTERY DISEASE WITH MAGNETIC RESONANCE FIRST-PASS IMAGING

MRFP perfusion imaging can now be used clinically on most MR scanner systems (1.0 to 1.5 T). The current experimental data demonstrate that MRFP imaging allows the quantitative assessment of myocardial blood flow changes and accurate measurements of collateral flow, including changes in the collateral dependent zones. Certain protocols, however, as outlined here have to be followed to obtain all the possible diagnostic information. Based on the current data on MRFP imaging, it is realistic to anticipate that MRFP imaging in combination with cine or tagging MR imaging will provide clinicians with better methods to distinguish stunned and hibernating, from nonviable myocardium and obtain better outcome data. Dedicated MR scanners are now being designed to meet the needs for MR imaging of patients with coronary artery disease. These scanners, small in size and with better patient access, make placement near the coronary care unit or catheterization laboratory feasible. This is a major step toward enhancing the utility of this new technique by providing the necessary infrastructure for scanning large numbers of patients. The main obstacle to wider use of these new diagnostic tools to assess perfusion is the lack of a large clinical database because there have not yet been major multicenter trials. With the development of novel intravascular contrast agents, however, larger trials are planned that should provide the clinical data mandatory for full integration of MRFP imaging into clinical practice. In particular, the development of dedicated and user-friendly perfusion analysis software will create the means to evaluate MR perfusion data accurately in large patient populations. These studies need to be conducted in a collaborative fashion by cardiologists, heart surgeons, and radiologists to be fully accepted by health care providers in an increasingly cost-averse and competitive health care environment.

Assessment of ischemic heart disease using magnetic resonance first-pass perfusion imaging.

Methods: Cardiovascular magnetic resonance (MR) perfusion imaging has matured to a point where it can be routinely applied to assess patients with coronary artery disease and ischemic cardiomyopathy. The method has been compared to invasive, catheter-based as well as other noninvasive imaging modalities (echocardiography, single-photon emission computed tomography [SPECT], and positron emission tomography [PET]) for the evaluation of patients with coronary artery disease. Besides qualitative evaluation of MR perfusion images, an absolute quantification of global, regional and transmural myocardial perfusion is possible. A relative or absolute myocardial perfusion reserve has been determined noninvasively with MR perfusion imaging, and can provide good agreement with the invasive assessment. Based on the perfusion reserve, the severity of an epicardial coronary stenosis can be evaluated in patients with known or suspected coronary artery disease. Besides the absence of radiation exposure, MR perfusion imaging offers good temporal and excellent spatial resolution. In particular, the spatial resolution increases the sensitivity and specificity for the detection of coronary artery disease. New parameters such as the “endo-/epimyocardial resting perfusion ratio”, may under some circumstances sufficiently enhance the sensitivity for detecting an abnormal perfusion, and thus avoid potentially harmful and expensive stress testing in patients with suspected ischemic heart disease. New revascularization modalities such as therapeutic angiogenesis need to be matched by sensitive imaging tools to prove their benefits. Thus, the optimization of therapeutic angiogenesis may profit from the diagnostic advantages provided by MR perfusion imaging. Furthermore, MR might yield new insights into the pathophysiology of cardiac diseases such as “syndrome X”, or might help in the repetitive assessment of heart transplant recipients, possibly obviating the need for further invasive testing.nConclusion: The breadth of cardiac MRI allows the combined noninvasive assessment of myocardial perfusion, function, as well as myocardial viability. The combination gives MRI a unique and strong position in the field of noninvasive diagnostic cardiology.Methodik: Die beschleunigte Bildakquisition der Magnetresonanztomographie (MRT) ermöglicht die Darstellung der Durchblutung des schlagenden menschlichen Herzens. Ein routinemäßiger Einsatz bei der Diagnostik von Patienten mit Verdacht auf oder gesicherter myokardialer Durchblutungsstörung ist vorstellbar. Vergleiche mit klinisch etablierten invasiven Verfahren, wie der Koronarangiographie, und nichtinvasiven nuklearmedizinischen Verfahren, wie der Single-Photon-Emissionscomputertomographie (SPECT), Positronenemissionstomographie (PET) oder Echokardiographie, zeigten bereits das Einsatzgebiet und den Stellenwert der Herz-MRT bei der Diagnostik von Patienten mit koronarer Herzerkrankung. Neben der rein qualitativen Beurteilung der Bilder ist auch eine quantitative Beurteilung sowohl der transmuralen als auch getrennt der endo- und epimyokardialen Durchblutung mit der Methode möglich. Die Bestimmung der relativen oder absoluten myokardialen Perfusionsreserve wurde mit der MR-First-Pass-Technik durchgeführt. Dabei zeigte sich eine gute Übereinstimmung mit der invasiv bestimmten koronaren Flussreserve. Basierend auf diesen quantitativen Werten lassen sich auch mit nichtinvasiven Methoden Aussagen über den Schweregrad epikardialer Koronarstenosen oder anderer Ursachen für eine Perfusionsminderung treffen. Dadurch kann möglicherweise die Häufigkeit wiederholter invasiver Untersuchungen,beispielsweise von Transplantationspatienten, reduziert werden. Neben der fehlenden Strahlenbelastung gewährleistet die MRT eine gute zeitliche und exzellente örtliche Bildauflösung. Es konnte gezeigt werden, dass vor allem die gute Bildauflösung unter selektiver Beurteilung der endomyokardialen Schicht die Sensitivität und Spezifität zur Erkennung der koronaren Herzerkrankung steigert. Die hohe Ortsauflösung ermöglichte es auch, neue Parameter bei der Herzperfusionsmessung zu bestimmen. Das endo-/epimyokardiale Perfusionsverhältnis, gemessen unter Ruhebedingungen, erlaubt es möglicherweise, auf einen Teil der sonst aufwendigen und mit etwaigen Komplikationen vergesellschafteten Stressuntersuchungen zu verzichten. Des Weiteren gewährt der Einsatz eines endomyokardialen Perfusionsindex neue Einblicke in die Pathophysiologie des kardialen Syndrom X. Zudem ist die MR-First-Pass-Perfusionsbildgebung, mit der eine nichtinvasive, strahlenfreie und sensitive Beurteilung der myokardialen Durchblutung gelingt, geeignet, die Wertigkeit neuer Therapieansätze zur Verbesserung der myokardialen Durchblutung (z.B. therapeutische Angiogenese) zu überprüfen.nSchlussfolgerung: Zusätzlich zur Untersuchung der Herzperfusion können Funktion und Vitalität mit der Herz-MRT beurteilt werden. Die Kombination aller Untersuchungen gibt der Methode ein breites Einsatzgebiet in der nichtinvasiven kardiologischen Diagnostik.