Alexander Gotschy

Multicenter Evaluation of Dynamic Three-Dimensional Magnetic Resonance Myocardial Perfusion Imaging for the Detection of Coronary Artery Disease Defined by Fractional Flow Reserve

Background—First-pass myocardial perfusion cardiovascular magnetic resonance (CMR) imaging yields high diagnostic accuracy for the detection of coronary artery disease (CAD). However, standard 2D multislice CMR perfusion techniques provide only limited cardiac coverage, and hence considerable assumptions are required to assess myocardial ischemic burden. The aim of this prospective study was to assess the diagnostic performance of 3D myocardial perfusion CMR to detect functionally relevant CAD with fractional flow reserve (FFR) as a reference standard in a multicenter setting. Methods and Results—A total of 155 patients with suspected CAD listed for coronary angiography with FFR were prospectively enrolled from 5 European centers. 3D perfusion CMR was acquired on 3T MR systems from a single vendor under adenosine stress and at rest. All CMR perfusion analyses were performed in a central laboratory and blinded to all clinical data. One hundred fifty patients were successfully examined (mean age 62.9±10 years, 45 female). The prevalence of CAD defined by FFR (<0.8) was 56.7% (85 of 150 patients). The sensitivity and specificity of 3D perfusion CMR were 84.7% and 90.8% relative to the FFR reference. Comparison to quantitative coronary angiography (≥50%) yielded a prevalence of 65.3%, sensitivity and specificity of 76.5% and 94.2%, respectively. Conclusions—In this multicenter study, 3D myocardial perfusion CMR proved highly diagnostic for the detection of significant CAD as defined by FFR.

Local Arterial Stiffening Assessed by MRI Precedes Atherosclerotic Plaque Formation

Background—Atherosclerosis is known to impair vascular function and cause vascular stiffening. The aim of this study was to evaluate the potential predictive role of vascular stiffening in the early detection of atherosclerosis. Therefore, we investigated the time course of early functional and morphological alterations of the vessel wall in a murine atherosclerosis model. Because initial lesions are distributed inhomogeneously in early-stage atherosclerosis, MR microscopy was performed to measure vascular elasticity locally, specifically the local pulse wave velocity and the arterial wall thickness. Methods and Results—Local pulse wave velocity and the mean arterial wall thickness were determined in the ascending and the abdominal aortae of ApoE−/− and wild-type mice. In vivo MRI revealed that baseline pulse wave velocity and morphology were similar in 6-week-old ApoE−/− and WT mice, whereas at the age of 18 weeks, local pulse wave velocity was significantly elevated in ApoE−/− mice. Significantly increased vessel wall thickness was not found in ApoE−/− mice until the age of 30 weeks. Histological analysis of the aortae of ApoE−/− and WT mice showed that increased pulse wave velocity coincided with the fragmentation of the elastic laminae in the arterial wall, which is hypothesized to induce early vascular stiffening and may be promoted by macrophage-mediated matrix degradation. Conclusions—We newly report that the assessment of local pulse wave velocity via MRI provides early information about the local progression of atherosclerosis before macroscopic alterations of the vessel wall occur.

Cardiovascular magnetic resonance for the assessment of coronary artery disease

Over the past decade, cardiovascular magnetic resonance (CMR) has become an established non-invasive imaging modality in cardiology. It provides clinicians and researchers with an unparalleled versatility of diagnostic parameters such as cardiac morphology, function, myocardial texture and vascular flow. One of the most relevant applications of CMR is the assessment of patients with suspected or known coronary artery disease (CAD). In large clinical trials, CMR has proven its robustness, diagnostic performance and prognostic value in CAD. In patients with known or suspected chronic CAD, detection of ischaemia and myocardial viability for guiding therapeutic decisions is a major strength of CMR. Patients with ischaemic congestive heart failure (CHF) may benefit from CMR for planning of device implantation or monitoring intracavital thrombi. Finally, the use of CMR in the emergency department for the assessment of patients with acute chest pain is an emerging field, in which CMRs capability to characterize myocardial tissue regarding e.g. necrosis, edema or microvascular obstruction (MVO) may prove clinically useful. The CMR technology is safe, free of ionizing radiation and proved higher diagnostic accuracy and superior cost efficiency compared with other standard diagnostic modalities.

Turbulent Kinetic Energy Assessed by Multipoint 4-Dimensional Flow Magnetic Resonance Imaging Provides Additional Information Relative to Echocardiography for the Determination of Aortic Stenosis Severity

Background— Turbulent kinetic energy (TKE), assessed by 4-dimensional (4D) flow magnetic resonance imaging, is a measure of energy loss in disturbed flow as it occurs, for instance, in aortic stenosis (AS). This work investigates the additional information provided by quantifying TKE for the assessment of AS severity in comparison to clinical echocardiographic measures. Methods and Results— Fifty-one patients with AS (67±15 years, 20 female) and 10 healthy age-matched controls (69±5 years, 5 female) were prospectively enrolled to undergo multipoint 4D flow magnetic resonance imaging. Patients were split into 2 groups (severe and mild/moderate AS) according to their echocardiographic mean pressure gradient. TKE values were integrated over the aortic arch to obtain peak TKE. Integrating over systole yielded total TKEsys and by normalizing for stroke volume, normalized TKEsys was obtained. Mean pressure gradient and TKE correlated only weakly (R2=0.26 for peak TKE and R2=0.32 for normalized TKEsys) in the entire study population including control subjects, while no significant correlation was observed in the AS patient group. In the patient population with dilated ascending aorta, both peak TKE and total TKEsys were significantly elevated (P<0.01), whereas mean pressure gradient was significantly lower (P<0.05). Patients with bicuspid aortic valves also showed significantly increased TKE metrics (P<0.01), although no significant difference was found for mean pressure gradient. Conclusions— Elevated TKE levels imply higher energy losses associated with bicuspid aortic valves and dilated ascending aortic geometries that are not assessable by current echocardiographic measures. These findings indicate that TKE may provide complementary information to echocardiography, helping to distinguish within the heterogeneous population of patients with moderate to severe AS.

Local versus global aortic pulse wave velocity in early atherosclerosis: An animal study in ApoE-/--mice using ultrahigh field MRI

Increased aortic stiffness is known to be associated with atherosclerosis and has a predictive value for cardiovascular events. This study aims to investigate the local distribution of early arterial stiffening due to initial atherosclerotic lesions. Therefore, global and local pulse wave velocity (PWV) were measured in ApoE-/- and wild type (WT) mice using ultrahigh field MRI. For quantification of global aortic stiffness, a new multi-point transit-time (TT) method was implemented and validated to determine the global PWV in the murine aorta. Local aortic stiffness was measured by assessing the local PWV in the upper abdominal aorta, using the flow/area (QA) method. Significant differences between age matched ApoE-/- and WT mice were determined for global and local PWV measurements (global PWV: ApoE-/-: 2.7±0.2m/s vs WT: 2.1±0.2m/s, P<0.03; local PWV: ApoE-/-: 2.9±0.2m/s vs WT: 2.2±0.2m/s, P<0.03). Within the WT mouse group, the global PWV correlated well with the local PWV in the upper abdominal aorta (R2 = 0.75, P<0.01), implying a widely uniform arterial elasticity. In ApoE-/- animals, however, no significant correlation between individual local and global PWV was present (R2 = 0.07, P = 0.53), implying a heterogeneous distribution of vascular stiffening in early atherosclerosis. The assessment of global PWV using the new multi-point TT measurement technique was validated against a pressure wire measurement in a vessel phantom and showed excellent agreement. The experimental results demonstrate that vascular stiffening caused by early atherosclerosis is unequally distributed over the length of large vessels. This finding implies that assessing heterogeneity of arterial stiffness by multiple local measurements of PWV might be more sensitive than global PWV to identify early atherosclerotic lesions.

First fusion and combined evaluation of 3D-CMR perfusion with 3D-MR coronary angiography

Introduction Myocardial perfusion and the status of the coronary arteries are the two major parameters for the characterization of coronary artery disease (CAD) and for guiding therapeutical interventions. It has been shown that hybrid imaging strategies to acquire both parameters such as SPECT with CT-angiography provide an added value for clinical decision making in the treatment of CAD[1]. Thus the 2014 ESC Guidelines for the first time recommend hybrid imaging for planning myocardial revascularization[2]. However, SPECT and CT expose the patient to ionizing radiation and, in large prospective trials, SPECT showed inferior sensitivity to detect CAD when compared with CMR-perfusion[3]. Therefore, the aim of this study was to investigate the feasibility and potential added value of MR-based hybrid imaging by the combined assessment and fusion of 3D-MR coronary angiography (MRCA) with a 3D-CMR perfusion sequence.

Quantitative comparison of 2D and 3D late gadolinium enhancement MR imaging in patients with Fabry disease and hypertrophic cardiomyopathy.

BACKGROUND This study aims to determine whether the quantification of myocardial fibrosis in patients with Fabry disease (FD) and hypertrophic cardiomyopathy (HCM) using a late gadolinium enhancement (LGE) singlebreath-hold three-dimensional (3D) inversion recovery magnetic resonance (MR) imaging sequence is comparable with a clinically established two-dimensional (2D) multi-breath-hold sequence. METHODS In this retrospective, IRB-approved study, 40 consecutive patients (18 male; mean age 50±17years) with Fabry disease (n=18) and HCM (n=22) underwent MR imaging at 1.5T. Spatial resolution was the same for 3D and 2D images (field-of-view, 350×350mm(2); in-plane-resolution, 1.2×1.2mm(2); section-thickness, 8mm). Datasets were analyzed for subjective image quality; myocardial and fibrotic mass, and total fibrotic tissue percentage were quantified. RESULTS There was no significant difference in subjective image quality between 3D and 2D acquisitions (P=0.1 and P=0.3) for either disease. In patients with Fabry disease there were no significant differences between 3D and 2D acquisitions for myocardial mass (P=0.55), fibrous tissue mass (P=0.89), and total fibrous percentage (P=0.67), with good agreement between acquisitions according to Bland-Altman analyses. In patients with HCM there were also no significant differences between acquisitions for myocardial mass (P=0.48), fibrous tissue mass (P=0.56), and total fibrous percentage (P=0.67), with good agreement according to Bland-Altman analyses. Acquisition time was significantly shorter for 3D (25±5s) as compared to the 2D sequence (349±62s, P<0.001). CONCLUSIONS In patients with Fabry disease and HCM, 3D LGE imaging provides equivalent diagnostic information in regard to quantification of myocardial fibrosis as compared with a standard 2D sequence, but at superior acquisition speed.

Arrhythmogenic Left Ventricular Cardiomyopathy Suspected by Cardiac Magnetic Resonance Imaging, Confirmed by Identification of a Novel Plakophilin-2 Variant

A 26-year-old man was referred for family screening and cardiologic workup by the Institute of Legal Medicine. His mother recently succumbed to sudden cardiac death at work at 49 years of age. Her macroscopic and microscopic autopsy revealed arrhythmogenic right ventricular (RV) cardiomyopathy/dysplasia (ARVC/D) with diffuse left ventricular (LV) involvement (Figure 1). The 26-year-old patient, who has never engaged in competitive sports, reported a history of syncope without injury while playing leisure soccer 7 years ago. Since then, he has rarely felt palpitations. There was no history of infection within the last 12 months before the cardiologic workup. Clinical findings were normal. A 12-lead-surface ECG demonstrated notched early repolarization in the inferior leads and QRS fragmentation in aVL but no ECG criteria according to the 2010 ARVC/D Task Force (Figure 2). Signal-averaged ECG was unremarkable, and 24-hour Holter ECG revealed >1000 premature ventricular contractions with 3 different morphologies. Laboratory parameters were within the normal range, particularly for C-reactive protein, brain natriuretic peptide, and troponin T. Transthoracic 2- and 3-dimensional echocardiography (transthoracic echocardiography), RV angiography, and 3-D electroanatomical endocardial RV voltage mapping were unremarkable. Cardiac …

Analysis of spatiotemporal fidelity in quantitative 3D first-pass perfusion cardiovascular magnetic resonance

BackgroundWhole-heart first-pass perfusion cardiovascular magnetic resonance (CMR) relies on highly accelerated image acquisition. The influence of undersampling on myocardial blood flow (MBF) quantification has not been systematically investigated yet. In the present work, the effect of spatiotemporal scan acceleration on image reconstruction accuracy and MBF error was studied using a numerical phantom and validated in-vivo.MethodsUp to 10-fold scan acceleration using k-t PCA and k-t SPARSE-SENSE was simulated using the MRXCAT CMR numerical phantom framework. Image reconstruction results were compared to ground truth data in the k-f domain by means of modulation transfer function (MTF) analysis. In the x-t domain, errors pertaining to specific features of signal intensity-time curves and MBF values derived using Fermi model deconvolution were analysed. In-vivo first-pass CMR data were acquired in ten healthy volunteers using a dual-sequence approach assessing the arterial input function (AIF) and myocardial enhancement. 10x accelerated 3D k-t PCA and k-t SPARSE-SENSE were compared and related to non-accelerated 2D reference images.ResultsMTF analysis revealed good recovery of data upon k-t PCA reconstruction at 10x undersampling with some attenuation of higher temporal frequencies. For 10x k-t SPARSE-SENSE the MTF was found to decrease to zero at high spatial frequencies for all temporal frequencies indicating a loss in spatial resolution. Signal intensity-time curve errors were most prominent in AIFs from 10x k-t PCA, thereby emphasizing the need for separate AIF acquisition using a dual-sequence approach. These findings were confirmed by MBF estimation based on AIFs from fully sampled and undersampled simulations. Average in-vivo MBF estimates were in good agreement between both accelerated and the fully sampled methods. Intra-volunteer MBF variation for fully sampled 2D scans was lower compared to 10x k-t PCA and k-t SPARSE-SENSE data.ConclusionQuantification of highly undersampled 3D first-pass perfusion CMR yields accurate MBF estimates provided the AIF is obtained using fully sampled or moderately undersampled scans as part of a dual-sequence approach. However, relative to fully sampled 2D perfusion imaging, intra-volunteer variation is increased using 3D approaches prompting for further developments.

The third ventricle — A case of a giant post infarct pseudoaneurysm

a Clinic of Cardiology, University Heart Center, University Hospital Zurich, Zurich, Switzerland b Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland c Cardiology, ZurcherHohenklinik Wald, Switzerland d Division of Cardiovascular Surgery, University Hospital Zurich, Zurich, Switzerland e Division of Internal Medicine, University Hospital Zurich, Zurich, Switzerland f Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland