Assessment of liver fibrosis using fast strain-encoded MRI driven by inherent cardiac motion.

PURPOSE: An external driver-free MRI method for assessment of liver fibrosis offers a promising noninvasive tool for diagnosis and monitoring of liver disease. Lately, the heart's intrinsic motion and MR tagging have been utilized for the quantification of liver strain. However, MR tagging requires multiple breath-hold acquisitions and substantial postprocessing. In this study, we propose the use of a fast strain-encoded (FSENC) MRI method to measure the peak strain (Sp ) in the liver's left lobe, which is in close proximity and caudal to the heart. Additionally, we introduce a new method of measuring heart-induced shear wave velocity (SWV) inside the liver. METHODS: Phantom and in vivo experiments (11 healthy subjects and 11 patients with liver fibrosis) were conducted. Reproducibility experiments were performed in seven healthy subjects. RESULTS: Peak liver strain, Sp , decreased significantly in fibrotic liver compared with healthy liver (6.46% ± 2.27% vs 12.49% ± 1.76%; P < 0.05). Heart-induced SWV increased significantly in patients compared with healthy subjects (0.15 ± 0.04 m/s vs 0.63 ± 0.32 m/s; P < 0.05). Reproducibility analysis yielded no significant difference in Sp (P = 0.47) or SWV (P = 0.56). CONCLUSION: Accelerated external driver-free noninvasive assessment of left liver lobe strain and SWV is feasible using strain-encoded MRI. The two measures significantly separate healthy subjects from patients with fibrotic liver. Magn Reson Med 74:106-114, 2015. © 2014 Wiley Periodicals, Inc.

Regional and global biventricular function in pulmonary arterial hypertension: a cardiac MR imaging study.

PURPOSE: To determine whether chronic pulmonary arterial pressure (PAP) elevation affects regional biventricular function and whether regional myocardial function may be reduced in pulmonary arterial hypertension (PAH) patients with preserved global right ventricular (RV) function. MATERIALS AND METHODS: After informed consent, 35 PAH patients were evaluated with right heart catheterization and cardiac magnetic resonance (MR) imaging and compared with 13 healthy control subjects. Biventricular segmental, section, and mean ventricular peak systolic longitudinal strain (E(LL)), as well as left ventricular (LV) circumferential and RV tangential strains were compared between PAH patients and control subjects and correlated with global function and catheterization of the right heart indexes. Spearman ρ correlation with Bonferroni correction was used. Multiple linear regression analysis was performed to determine predictors for regional myocardial function. RESULTS: In the RV of PAH patients, longitudinal contractility was reduced at the basal, mid, and apical levels, and tangential contractility was reduced at the midventricular level. Mean RV E(LL) positively correlated with mean PAP (r = 0.62, P < .0014) and pulmonary vascular resistance index (PVRI) (r = 0.77, P < .0014). Mean PAP was a predictor of mean RV E(LL) (ß = .19, P = .005) in a multiple linear regression analysis. In the LV, reduced LV longitudinal and circumferential contractility were noted at the base. LV anteroseptal E(LL) positively correlated with increased mean PAP (r = 0.5, P = .03) and septal eccentricity index (r = 0.5, P = .01). In a subgroup of PAH patients with normal global RV function, significantly reduced RV longitudinal contractility was noted at basal and mid anterior septal insertions, as well as the mid anterior RV wall (P < .05 for all). CONCLUSION: In PAH patients, reduced biventricular regional function is associated with increased RV afterload (mean PAP and PVRI). Cardiac MR imaging helps identify regional RV dysfunction in PAH patients with normal global RV function. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12111599/-/DC1.

Left ventricular diastolic function in type 2 diabetes mellitus is associated with myocardial triglyceride content but not with impaired myocardial perfusion reserve.

PURPOSE: To study myocardial perfusion reserve and myocellular metabolic alterations indicated by triglyceride content as possible causes of diastolic dysfunction in patients with type 2 diabetes mellitus, preserved systolic function, and without clinically evident coronary artery disease. MATERIALS AND METHODS: Patients with type 2 diabetes mellitus (n = 42) underwent cardiac magnetic resonance (CMR) for quantification of 1) myocardial contractility by strain-encoded MR (SENC); 2) myocardial triglyceride content by proton magnetic resonance spectroscopy ((1) H-MRS); and 3) myocardial perfusion reserve during pharmacologic hyperemia. Age-matched healthy volunteers (n = 16) also underwent CMR to acquire normal values for myocardial strain and perfusion reserve. RESULTS: Stress CMR procedures were successfully performed in all subjects, and no regional inducible perfusion defects were observed in type 2 diabetes mellitus patients. Diastolic strain rate and myocardial perfusion reserve were significantly impaired in patients with type 2 diabetes mellitus compared to control subjects (P < 0.001 for both). Interestingly, impaired diastolic function in type 2 diabetes mellitus was not associated with impaired myocardial perfusion reserve (r = 0.12, P = NS). Conversely a significant association was observed between diastolic dysfunction and myocardial triglyceride content (r = -0.71, P < 0.001), which proved to be independent of age, gender, diabetes duration, blood pressure, and fasting blood glucose. CONCLUSION: Myocardial steatosis may represent an early marker of diabetic heart disease, triggering subclinical myocardial dysfunction irrespective of myocardial perfusion reserve.

Strain-encoded breast MRI in phantom and ex vivo specimens with histological validation: preliminary results.

PURPOSE: To evaluate the feasibility of using strain-encoded (SENC) breast magnetic resonance images (MRI) for breast cancer detection by examining the compression and relaxation response properties in phantoms and ex vivo breast samples. METHODS: A tissue phantom was constructed to mimic different sizes of breast masses and tissue stiffness. In addition, five human ex vivo whole breast specimens with and without masses were studied. MR data was acquired on a 3T scanner consisting of T(1)-weighted, fat suppressed spin echo T(2)-weighted, and SENC breast images. Mechanical tissue characteristics (strain) of the phantoms and breast tissue samples were measured using SENC imaging in both compression and relaxation modes. The breast tissue specimens were sectioned and stained in the same plane as the MRI for histological evaluation. RESULTS: For the phantom, SENC images showed soft masses with quantitative strain values between 35% and 50%, while harder masses had strain values between 0% and 20%. Combined compression (CMP) and relaxation (REX) breast SENC images separately categorized all masses into three different groups. For breast SENC, the signal intensities between ex vivo breast mass and breast glandular tissue were significantly different (-7.6 ± 2.6 verses -20.6 ± 5.4 for SENC-CMP, and 4.2 ± 1.5 verses 22.6 ± 5 for SENC-REX, p < 0.05). CONCLUSIONS: We have demonstrated that SENC breast MRI can be used to obtain mechanical tissue properties and give quantitative estimates of strain in tumors. This feasibility study provides the basis for future clinical studies.

Real-time single-heartbeat fast strain-encoded imaging of right ventricular regional function: normal versus chronic pulmonary hypertension.

Patients with pulmonary hypertension and suspected right ventricular (RV) dysfunction often have dyspnea at rest, making reliable assessment of RV function using traditional breath-holding methods difficult to perform. Using single-heartbeat fast strain encoding (Fast-SENC) imaging, peak systolic RV circumferential and longitudinal strains were measured in 11 healthy volunteers and 11 pulmonary hypertension patients. Fast-SENC RV longitudinal strain and circumferential strain measurements were compared to conventional SENC and MR tagging, respectively. Fast-SENC circumferential and longitudinal RV shortening correlated closely with SENC measurements (r = 0.86, r = 0.90, P < 0.001 for all). Circumferential strain, by conventional tagging, showed moderate correlation with Fast-SENC in pulmonary hypertension patients only (r = 0.5, P = 0.003). A nonuniform pattern of RV circumferential shortening was depicted in both groups. Peak systolic circumferential strain was significantly reduced at the basal RV in pulmonary hypertension patients (-18.06 +/- 3.3 versus -21.9 +/- 1.9, P < 0.01) compared to normal individuals, while peak systolic longitudinal strain was significantly reduced at all levels (P < 0.01 for all). Fast-SENC is a feasible and reliable technique for rapid quantification of RV regional function in a single-heartbeat acquisition. Information derived from Fast-SENC allows characterization of RV regional function in normal individuals and in pulmonary hypertension patients.

A multi-vendor, multi-center study on reproducibility and comparability of fast strain-encoded cardiovascular magnetic resonance imaging.

Myocardial strain is a convenient parameter to quantify left ventricular (LV) function. Fast strain-encoding (fSENC) enables the acquisition of cardiovascular magnetic resonance images for strain-measurement within a few heartbeats during free-breathing. It is necessary to analyze inter-vendor agreement of techniques to determine strain, such as fSENC, in order to compare existing studies and plan multi-center studies. Therefore, the aim of this study was to investigate inter-vendor agreement and test-retest reproducibility of fSENC for three major MRI-vendors. fSENC-images were acquired three times in the same group of 15 healthy volunteers using 3 Tesla scanners from three different vendors: at the German Heart Institute Berlin, the Charité University Medicine Berlin-Campus Buch and the Theresien-Hospital Mannheim. Volunteers were scanned using the same imaging protocol composed of two fSENC-acquisitions, a 15-min break and another two fSENC-acquisitions. LV global longitudinal and circumferential strain (GLS, GCS) were analyzed by a trained observer (Myostrain 5.0, Myocardial Solutions) and for nine volunteers repeatedly by another observer. Inter-vendor agreement was determined using Bland-Altman analysis. Test-retest reproducibility and intra- and inter-observer reproducibility were analyzed using intraclass correlation coefficient (ICC) and coefficients of variation (CoV). Inter-vendor agreement between all three sites was good for GLS and GCS, with biases of 0.01-1.88%. Test-retest reproducibility of scans before and after the break was high, shown by ICC- and CoV values of 0.63-0.97 and 3-9% for GLS and 0.69-0.82 and 4-7% for GCS, respectively. Intra- and inter-observer reproducibility were excellent for both parameters (ICC of 0.77-0.99, CoV of 2-5%). This trial demonstrates good inter-vendor agreement and test-retest reproducibility of GLS and GCS measurements, acquired at three different scanners from three different vendors using fSENC. The results indicate that it is necessary to account for a possible bias (< 2%) when comparing strain measurements of different scanners. Technical differences between scanners, which impact inter-vendor agreement, should be further analyzed and minimized.DRKS Registration Number: 00013253.Universal Trial Number (UTN): U1111-1207-5874.

Clinical assessment of left ventricular rotation and strain: a novel approach for quantification of function in infarcted myocardium and its border zones.

Left ventricular (LV) circumferential strain and rotation have been introduced as clinical markers of myocardial function. This study investigates how regional LV apical rotation and strain can be used in combination to assess function in the infarcted ventricle. In healthy subjects (n = 15) and patients with myocardial infarction (n = 23), LV apical segmental rotation and strain were measured from apical short-axis recordings by speckle tracking echocardiography (STE) and MRI tagging. Infarct extent was determined by late gadolinium enhancement MRI. To investigate mechanisms of changes in strain and rotation, we used a mathematical finite element simulation model of the LV. Mean apical rotation and strain by STE were lower in patients than in healthy subjects (9.0 +/- 4.9 vs. 12.9 +/- 3.5 degrees and -13.9 +/- 10.7 vs. -23.8 +/- 2.3%, respectively, P < 0.05). In patients, regional strain was reduced in proportion to segmental infarct extent (r = 0.80, P < 0.0001). Regional rotation, however, was similar in the center of the infarct and in remote viable myocardium. Minimum and maximum rotations were found at the infarct borders: minimum rotation at the border zone opposite to the direction of apical rotation, and maximum rotation at the border zone in the direction of rotation. The simulation model reproduced the clinical findings and indicated that the dissociation between rotation and strain was caused by mechanical interactions between infarcted and viable myocardium. Systolic strain reflects regional myocardial function and infarct extent, whereas systolic rotation defines infarct borders in the LV apical region. Regional rotation, however, has limited ability to quantify regional myocardial dysfunction.

Inherent fat cancellation in complementary spatial modulation of magnetization.

An efficient fat suppression method is presented for MR tagging with complementary spatial modulation of magnetization (CSPAMM). In this method, the complementary modulation is applied to the water content of the tissues, while in-phase modulation is applied to the fat content. Therefore, during image reconstruction, the subtraction of the acquired images increases the tagging contrast of the water while cancels the tagging lines of the fat. Compared with the existing fat suppression techniques, the proposed method allows imaging with higher temporal resolution and shorter echo-time without increasing the scan time. The feasibility of applying the method on 1.5 Tesla (T) and 3.0T scanners has been tested using MR phantom and human volunteers.

Myocardial tissue tagging with cardiovascular magnetic resonance.

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional function that provides a detailed and comprehensive examination of intra-myocardial motion and deformation. Given the current advances in gradient technology, image reconstruction techniques, and data analysis algorithms, CMR myocardial tagging has become the reference modality for evaluating multidimensional strain evolution in the human heart. This review presents an in depth discussion on the current clinical applications of CMR myocardial tagging and the increasingly important role of this technique for assessing subclinical myocardial dysfunction in the setting of a wide variety of myocardial disease processes.

A combined harmonic phase and strain-encoded pulse sequence for measuring three-dimensional strain.

Measurement of myocardial strain provides direct information about heart function that can be correlated with disease. We present an MRI pulse sequence that acquires in just six heartbeats both harmonic phase (HARP) and strain-encoded (SENC) images and provides dense measurements of radial, circumferential and longitudinal strains within a single short-axis slice. Normal volunteer data confirm the feasibility of this pulse sequence, and acquired data demonstrate the strain measurement reliability.

Three-dimensional mapping of optimal left ventricular pacing site for cardiac resynchronization.

BACKGROUND: The efficacy of cardiac resynchronization therapy (CRT) depends on placement of the left ventricular lead within the late-activated territory. The geographic extent and 3-dimensional distribution of left ventricular (LV) locations yielding optimal CRT remain unknown. METHODS AND RESULTS: Normal or tachypacing-induced failing canine hearts made dyssynchronous by right ventricular free wall pacing or chronic left bundle-branch ablation were acutely instrumented with a nonconstraining epicardial elastic sock containing 128 electrodes interfaced with a computer-controlled stimulation/recording system. Biventricular CRT was performed using a fixed right ventricular site and randomly selected LV sites covering the entire free wall. For each LV site, global cardiac function (conductance catheter) and mechanical synchrony (magnetic resonance imaging tagging) were determined to yield 3-dimensional maps reflecting CRT impact. Optimal CRT was achieved from LV lateral wall sites, slightly more anterior than posterior and more apical than basal. LV sites yielding > or = 70% of the maximal dP/dtmax increase covered approximately 43% of the LV free wall. This distribution and size were similar in both normal and failing hearts. The region was similar for various systolic and diastolic parameters and correlated with 3-dimensional maps based on mechanical synchrony from magnetic resonance imaging strain analysis. CONCLUSIONS: In hearts with delayed lateral contraction, optimized CRT is achieved over a fairly broad area of LV lateral wall in both nonfailing and failing hearts, with modest anterior or posterior deviation still capable of providing effective CRT. Sites selected to achieve the most mechanical synchrony are generally similar to those that most improve global function, confirming a key assumption underlying the use of wall motion analysis to optimize CRT.

Strain-encoding cardiovascular magnetic resonance for assessment of right-ventricular regional function.

BACKGROUND: Tissue tagging by cardiovascular magnetic resonance (CMR) is a comprehensive method for the assessment of cardiac regional function. However, imaging the right ventricle (RV) using this technique is problematic due to the thin wall of the RV relative to tag spacing which limits assessment of regional function using conventional in-plane tagging. HYPOTHESIS: We hypothesize that the use of through-plane tags in the strain-encoding (SENC) CMR technique would result in reproducible measurements of the RV regional function due to the high image quality and spatial resolution possible with SENC. AIM: To test the intra- and inter-observer variabilities of RV peak systolic strain measurements with SENC CMR for assessment of RV regional function (systolic strain) in healthy volunteers. METHODS: Healthy volunteers (n = 21) were imaged using SENC. A four-chamber view was acquired in a single breath-hold. Circumferential strain was measured during systole at six equidistant points along the RV free wall. Peak contraction is defined as the maximum value of circumferential strain averaged from the six points, and regional function is defined as the strain value at each point at the time of peak contraction. RESULTS: Mean values for peak circumferential strain (+/- standard deviation) of the basal, mid, and apical regions of the RV free wall were -20.4 +/- 2.9%, -18.8 +/- 3.9%, and -16.5 +/- 5.7%, Altman plots showed good intra- and inter-observer agreements with mean difference of 0.11% and 0.32% and limits of agreement of -4.038 to 4.174 and -4.903 to 5.836, respectively. CONCLUSION: SENC CMR allows for rapid quantification of RV regional function with low intra- and inter-observer variabilities, which could permit accurate quantification of regional strain in patients with RV dysfunction.

Real-time monitoring of cardiac regional function using fastHARP MRI and region-of-interest reconstruction.

Cardiovascular stress test imaging assists in the diagnosis and monitoring of cardiovascular disease. The procedure can be carried out in a magnetic resonance (MR) scanner using pharmacological agents that mimic the effects of natural exercise. In order to provide real time indication of ischemia, thereby assisting in diagnosis and helping to assure patient safety, it is desirable to have real time monitoring of the myocardial regional function. This paper presents an algorithm for the real time myocardium region-of-interest reconstruction and myocardial strain computation using data acquired from a real time pulse sequence that has been previously reported. The chirp Fourier transform is used for efficient computation, enabling a real-time continuous strain map at a rate of 25 frames/s. Coupled with a real time data path from the scanner to a laptop computer, this algorithm enables real time continuous monitoring of cardiac strain and is targeted for use in the early detection and quantification of ischemia during MR stress tests.

Spectrally-Presaturated Modulation (SPM): An efficient fat suppression technique for STEAM-based cardiac imaging sequences.

Stimulated-echo acquisition mode (STEAM) is a key pulse sequences in MRI in general, and in cardiac imaging in particular. Fat suppression is an important feature in cardiac imaging to improve visualization and eliminate off-resonance and chemical-shift artifacts. Nevertheless, fat suppression comes at the expense of reduced temporal resolution and signal-to-noise ratio (SNR). The purpose of this study is to develop an efficient fat suppression method (Spectrally-Presaturated Modulation) for STEAM-based sequences to enable imaging with high temporal-resolution, high SNR, and no increase in scan time. The developed method is based on saturating the fat magnetization prior to applying STEAM modulation; therefore, only the water-content of the tissues is modulated by the sequence, resulting in fat-suppressed images without the need to run the fat suppression module during image acquisition. The potential significance of the proposed method is presented in two STEAM-based cardiac MRI applications: complementary spatial-modulation of magnetization (CSPAMM), and black-blood cine imaging. Phantom and in vivo experiments are conducted to evaluate the developed technique and compare it to the commonly implemented chemical-shift selective (CHESS) and water-excitation using spectral-spatial selective pulses (SSSP) fat suppression techniques. The results from the phantom and in vivo experiments show superior performance of the proposed method compared to the CHESS and SSSP techniques in terms of temporal resolution and SNR. In conclusion, the developed fat suppression technique results in enhanced image quality of STEAM-based images, especially in cardiac applications, where high temporal-resolution is imperative for accurate measurement of functional parameters and improved performance of image analysis algorithms.

Does subclinical hypothyroidism affect cardiac pump performance? Evidence from a magnetic resonance imaging study.

OBJECTIVES: We sought to assess the effects of subclinical hypothyroidism (SHT) on the cardiac volumes and function. BACKGROUND: The cardiovascular system is one of the principal targets of thyroid hormones. Subclinical hypothyroidism is a common disorder that may represent "early" thyroid failure. METHODS: Thyroid profile was evaluated in 30 females with SHT and 20 matched control subjects. Left ventricular end-diastolic volume (EDV) and end-systolic volume (ESV), stroke volume (SV), cardiac index (CI), and systemic vascular resistance (SVR) were calculated by cardiac magnetic resonance (CMR). Regional greatest systolic lengthening (E1) and greatest systolic shortening (E2) were calculated by tagging CMR. RESULTS: EDV was lower in SHT than in controls (64.3 +/- 8.7 ml/m(2) vs. 81.4 +/- 11.3 ml/m(2), p < 0.001), as well as SV [corrected] (38.9 +/- 7.5 ml/m(2) vs. 52.5 +/- 6.1 ml/m(2), p < 0.001) and CI (2.6 +/- 0.5 l/[min.m(2)] vs. 3.7 +/- 0.4 l/[min.m(2)], p < 0.001). SVR [corrected] was higher in SHT (12.5 +/- 2.5 mm Hg.min/[l.m(2)] vs. 8.6 +/- 1.1 mm Hg.min/[l.m(2)], p = 0.003). The E1 was higher in controls than in SHT at the basal (p = 0.007), equatorial (p = 0.05), and apical (p = 0.008) levels, as well as E2 at the equatorial (p = 0.001) and apical (p = 0.001) levels. All parameters normalized after replacement therapy. A negative correlation between TSH and EDV (p < 0.001), SV (p < 0.001), CI (p < 0.001), and E1 at the apical level (p < 0.001) and a positive correlation between TSH and SVR (p < 0.001) and E2 at the apical level (p < 0.001) were found. CONCLUSIONS: Subclinical hypothyroidism significantly decreased cardiac preload, whereas it increased afterload with a consequent reduction in SV and cardiac output. Replacement therapy fully normalized the hemodynamic alterations.

Effect of long-term cocaine use on regional left ventricular function as determined by magnetic resonance imaging.

This study examined left ventricular (LV) regional midwall circumferential strain by cardiac tagged magnetic resonance imaging in 32 long-term cocaine users and 14 nonusers. Most of the LV segmentations in the cocaine users had less average circumferential strain in the systolic and diastolic phases. The average diastolic strain in 5 ventricular segmentations was significantly less in the cocaine users (p<0.05). In conclusion, long-term cocaine use may be associated with regional LV dysfunction, especially diastolic dysfunction.

Artifact-free black-blood cine cardiac imaging in a single breath-hold.

Fast imaging using the STimulated Echo Acquisition Mode (STEAM) sequence can produce cine images of the heart with black-blood contrast. Nevertheless, correction of deformation-related artifacts is required in order to maintain myocardial signal throughout the cardiac cycle. Recent work by our group has eliminated this artifact by combining two STEAM sequences acquired with two different demodulation gradients. Unfortunately, these two STEAM sequences were acquired on two separate breath-holds; thus, scan time doubled. In this work, we present a technique to reduce the total scan time by one half, without sacrificing image quality. The technique is based on interleaving two demodulations within one acquisition in order to obtain quality cine images of the heart in a single breath-hold. The technique was tested on animal models and human subjects, and the impact of interleaved acquisition on image quality was studied using quantitative and qualitative measures.

An integrated system for real-time detection of stiff masses with a single compression.

An integrated system is proposed for real-time imaging of tissue deformation in response to externally applied mechanical compression. The purpose of the system is to noninvasively detect tissue lesions based on their stiffness. The method includes applying external compression to the examined subject and acquiring magnetic resonance strain-encoded images using a real-time pulse sequence. In the proposed system, only a single compression is necessary to obtain a two-dimensional map of tissue deformation in a slice, eliminating the need for a complicated compressing device. The system was built and validated using phantom experiments.

Myocardial Perfusion Reserve and Strain-Encoded CMR for Evaluation of Cardiac Allograft Microvasculopathy.

OBJECTIVES: This study sought to evaluate myocardial perfusion reserve index (MPRI) and diastolic strain rate, both assessed by cardiac magnetic resonance (CMR) as a noninvasive tool for the detection of microvasculopathy. BACKGROUND: Long-term survival of cardiac allograft recipients is limited primarily by cancer and cardiac allograft vasculopathy (CAV). Besides epicardial CAV, diagnosed by coronary angiography, stenotic microvasculopathy was found to be an additional independent risk factor for survival after heart transplantation. METHODS: Sixty-three consecutive heart transplant recipients who underwent CMR, coronary angiography, and myocardial biopsy were enrolled. Stenotic vasculopathy in microvessels was considered in myocardial biopsies by immunohistochemistry and CAV was graded during coronary angiography according to International Society of Heart and Lung Transplantation criteria. In addition, by CMR microvasculopathy was assessed by myocardial perfusion reserve during pharmacologic hyperemia with adenosine and strain-encoded magnetic resonance using a modified spatial modulation of magnetization tagging pulse sequence in all patients. RESULTS: Decreasing MPRI and diastolic strain rates were observed in patients with decreasing microvessel luminal radius to wall thickness ratio and decreasing capillary density (r = 0.45 and r = 0.61 for MPRI and r = 0.50 and r = 0.38 for diastolic strain rate, respectively; p < 0.005 for all). Using multivariable analysis, both MPRI and diastolic strain rate were robust predictors of stenotic microvasculopathy, independent of age, organ age, and CAV by International Society of Heart and Lung Transplantation criteria (hazard ratio: 0.07, p = 0.006 for MPRI; hazard ratio: 0.91, p = 0.002 for diastolic strain rate). Patients without stenotic microvasculopathy in the presence of no or mild CAV (n = 36) exhibited significantly higher median survival free of events, compared with patients with stenotic microvasculopathy in the presence of no or mild CAV (n = 18; p = 0.04 by log rank). CONCLUSIONS: CMR represents a valuable noninvasive diagnostic tool, which may be used for the early detection of transplant microvasculopathy before the manifestation of CAV during surveillance coronary angiographic procedures.

Quantitative ischemia detection during cardiac magnetic resonance stress testing by use of FastHARP.

BACKGROUND: Because ECG alterations caused by ischemia cannot be reliably detected in the high-field MRI environment, detection of wall motion abnormalities is often used to ensure patient safety during stress testing. However, an experienced observer is needed to detect these abnormalities. In this study, we investigate the use of fast harmonic phase (FastHARP) MRI for the quantitative, operator-independent detection of the onset of ischemia during acute coronary occlusion. METHODS AND RESULTS: Eight mongrel dogs underwent an acute 2-minute closed-chest coronary artery occlusion while continuous FastHARP images were acquired. Full regional wall strain was determined every other heartbeat in a single short-axis imaging slice. After 5 minutes of reperfusion, a second 2-minute ischemic episode was induced during the acquisition of conventional cine wall-motion images. The time at which ECG alterations were observed during the first ischemic period was recorded. The time from occlusion to the detection of ischemia, based on a consensus of 2 blinded observers, was determined for MRI. No significant ischemia was present in 2 animals. In the remaining animals, the onset of ischemia was detected significantly earlier by FastHARP than by cine MRI (9.5+/-5 versus 33+/-14 seconds, P<0.01). HARP ischemia detection preceded ECG changes, on average, by 54 seconds. CONCLUSIONS: The rapid acquisition and detection of induced ischemia with FastHARP MRI shows promise as a nonsubjective method to diagnose significant coronary lesions during MR stress testing.