First-pass Perfusion Cardiac Magnetic Resonance Research Articles

Stress CMR T1-mapping technique for assessment of coronary microvascular dysfunction in a rabbit model of type II diabetes mellitus: Validation against histopathologic changes.

Coronary microvascular dysfunction (CMD) is an early character of type 2 diabetes mellitus (T2DM), and is indicative of adverse events. The present study aimed to validate the performance of the stress T1 mapping technique on cardiac magnetic resonance (CMR) for identifying CMD from a histopathologic perspective and to establish the time course of CMD-related parameters in a rabbit model of T2DM. New Zealand white rabbits (n = 30) were randomly divided into a control (n = 8), T2DM 5-week (n = 6), T2DM 10-week (n = 9), and T2DM 15-week (n = 7) groups. The CMR protocol included rest and adenosine triphosphate (ATP) stress T1-mapping imaging using the 5b(20b)3b-modified look-locker inversion-recovery (MOLLI) schema to quantify stress T1 response (stress ΔT1), and first-pass perfusion CMR to quantify myocardial perfusion reserve index (MPRI). After the CMR imaging, myocardial tissue was subjected to hematoxylin-eosin staining to evaluate pathological changes, Masson trichrome staining to measure collagen volume fraction (CVF), and CD31 staining to measure microvascular density (MVD). The associations between CMR parameters and pathological findings were determined using Pearson correlation analysis. The stress ΔT1 values were 6.21 ± 0.59%, 4.88 ± 0.49%, 3.80 ± 0.40%, and 3.06 ± 0.54% in the control, T2DM 5-week, 10-week, and 15-week groups, respectively (p < 0.001) and were progressively weakened with longer duration of T2DM. Furthermore, a significant correlation was demonstrated between the stress ΔT1 vs. CVF and MVD (r = -0.562 and 0.886, respectively; p < 0.001). The stress T1 response correlated well with the histopathologic measures in T2DM rabbits, indicating that it may serve as a sensitive CMD-related indicator in early T2DM.

Efficient convolution-based pairwise elastic image registration on three multimodal similarity metrics

This paper proposes a complete convolutional formulation for 2D multimodal pairwise image registration problems based on free-form deformations. We have reformulated in terms of discrete 1D convolutions the evaluation of spatial transformations, the regularization term, and their gradients for three different multimodal registration metrics, namely, normalized cross correlation, mutual information, and normalized mutual information. A sufficient condition on the metric gradient is provided for further extension to other metrics. The proposed approach has been tested, as a proof of concept, on contrast-enhanced first-pass perfusion cardiac magnetic resonance images. Execution times have been compared with the corresponding execution times of the classical tensor product formulation, both on CPU and GPU. The speed-up achieved by using convolutions instead of tensor products depends on the image size and the number of control points considered, the larger those magnitudes, the greater the execution time reduction. Furthermore, the speed-up will be more significant when gradient operations constitute the major bottleneck in the optimization process.

First-pass perfusion cardiovascular magnetic resonance parameters as surrogate markers for left ventricular diastolic dysfunction: a validation against cardiac catheterization

The non-invasive assessment of left ventricular (LV) diastolic dysfunction remains a challenge. The role of first-pass perfusion cardiac magnetic resonance (CMR) parameters in quantitative hemodynamic analyses has been reported. We therefore aimed to validate the diagnostic ability and accuracy of such parameters against cardiac catheterization for LV diastolic dysfunction in patients with left heart disease (LHD). We retrospectively enrolled 77 LHD patients who underwent CMR imaging and cardiac catheterization. LV diastolic dysfunction was defined as pulmonary capillary wedge pressure (PCWP) or LV end-diastolic pressure (LVEDP) > 12 mmHg on catheterization. On first-pass perfusion CMR imaging, pulmonary transit time (PTT) was measured as the time for blood to pass from the left ventricle to the right ventricle (RV) through the pulmonary vasculature. Pulmonary transit beat (PTB) was the number of cardiac cycles within the interval, and pulmonary blood volume indexed to body surface area (PBVi) was the product of PTB and RV stroke volume index (RVSVi). Of the 77 LHD patients, 53 (68.83%) were found to have LV diastolic dysfunction, and showed significantly higher PTTc, PTB, and PBVi (p < 0.05) compared with those without. In multivariate analyses, only PTTc and PTB were identified as independent predictors of LV diastolic dysfunction (p < 0.05). With an optimal cutoff of 11.9 s, PTTc yielded the best diagnostic performance for LV diastolic dysfunction (area under the curve = 0.83, p < 0.001). PTTc may represent a non-invasive quantitative surrogate marker for the detection and assessment of diastolic dysfunction in LHD patients. • PTTc yielded the best diagnostic accuracy for diastolic dysfunction, with an optimal cutoff of 11.9 s, and a specificity of 100%. • PTTc and PTB were found to be independent predictors of LV diastolic dysfunction across different multivariate models with high reproducibility. • PTTc is a promising non-invasive surrogate marker for the detection and assessment of diastolic dysfunction in LHD patients.

Adenosine stress native T1 mapping demonstrates impaired myocardial perfusion reserve in non-ischemic dilated cardiomyopathy

Abstract Background Impaired myocardial perfusion reserve has been demonstrated in non-ischemic dilated cardiomyopathy (NIDCM) by positron emission tomography (PET) and adenosine-stress first-pass perfusion cardiac magnetic resonance (CMR) imaging. Adenosine stress native T1 mapping is a novel CMR technique able to assess myocardial perfusion without the use of contrast agents. The aim of the present study was to determine the clinical utility of this novel CMR technique in NIDCM. Methods A total of 20 consecutive patients (mean age 61±12 years, 80% males) with diagnosis of NIDCM who consented to be enrolled in the UHSM CMR registry were included in the present study. CMR at 3T including 1. cine imaging for the assessment of LV volumes, mass and global longitudinal strain (GLS) by tissue-tracking imaging; 2. rest and stress (adenosine 140 mcg/kg/min) MOLLI T1 mapping of mid-ventricular slice for the assessment of rest and stress T1 values and T1 reactivity (ΔT1%); 3. first-pass perfusion imaging for the assessment of myocardial perfusion reserve index (MPRI) and 4. late gadolinium enhancement (LGE) imaging for the assessment of myocardial replacement fibrosis, was performed. Twenty control patients without history of known coronary artery disease and evidence of reversible ischemia or previous myocardial infarct on CMR imaging were included for comparison purposes. Results NIDCM patients had significantly higher native T1 value (1263±47 ms vs. 1234±38 ms, p=0.031), significantly lower ΔT1% (3.2±1.5% vs. 5.7±1.7%, p&amp;lt;0.001, Figure A), significantly lower MPRI (1.32±0.18 vs. 1.67±0.13, p&amp;lt;0.001) and significantly impaired GLS (−10±4% vs. −16±2%, p&amp;lt;0.001) as compared to controls. A significant strong relation between ΔT1% and MPRI (β=0.76, p&amp;lt;0.001, Figure B) and significant moderate relation between ΔT1% and GLS (β=−0.54, p&amp;lt;0.001) were observed. Conclusion T1 reactivity, myocardial perfusion reserve and GLS are significantly reduced in NIDCM patients compared to controls. Adenosine stress T1 mapping holds promise for detection of impaired myocardial perfusion reserve in NIDCM without the requirement for contrast agents. Funding Acknowledgement Type of funding source: None

Mechanisms of Myocardial Ischemia in Hypertrophic Cardiomyopathy: Insights From Wave Intensity Analysis and Magnetic Resonance

BackgroundAngina is common in hypertrophic cardiomyopathy (HCM) and is associated with abnormal myocardial perfusion. Wave intensity analysis improves the understanding of the mechanics of myocardial ischemia. ObjectivesWave intensity analysis was used to describe the mechanisms underlying perfusion abnormalities in patients with HCM. MethodsSimultaneous pressure and flow were measured in the proximal left anterior descending artery in 33 patients with HCM and 20 control patients at rest and during hyperemia, allowing calculation of wave intensity. Patients also underwent quantitative first-pass perfusion cardiac magnetic resonance to measure myocardial perfusion reserve. ResultsPatients with HCM had a lower coronary flow reserve than control subjects (1.9 ± 0.8 vs. 2.7 ± 0.9; p = 0.01). Coronary hemodynamics in HCM were characterized by a very large backward compression wave during systole (38 ± 11% vs. 21 ± 6%; p < 0.001) and a proportionately smaller backward expansion wave (27% ± 8% vs. 33 ± 6%; p = 0.006) compared with control subjects. Patients with severe left ventricular outflow tract obstruction had a bisferiens pressure waveform resulting in an additional proximally originating deceleration wave during systole. The proportion of waves acting to accelerate coronary flow increased with hyperemia, and the magnitude of change was proportional to the myocardial perfusion reserve (rho = 0.53; p < 0.01). ConclusionsCoronary flow in patients with HCM is deranged. Distally, compressive deformation of intramyocardial blood vessels during systole results in an abnormally large backward compression wave, whereas proximally, severe left ventricular outflow tract obstruction is associated with an additional deceleration wave. Perfusion abnormalities in HCM are not simply a consequence of supply/demand mismatch or remodeling of the intramyocardial blood vessels; they represent a dynamic interaction with the mechanics of myocardial ischemia that may be amenable to treatment.

4 A comprehensive assessment of the effect of recanalisation of chronic total occlusion

Background Successful recanalisation of chronic total occlusion (CTO) is associated with improved mortality but a strong correlation with burden of ischaemia and symptoms is lacking. Myocardial perfusion reserve (MPR) by first-pass perfusion cardiac magnetic resonance imaging (CMR) is an accurate non-invasive measure of myocardial ischaemia. We evaluated the effect of percutaneous coronary intervention (PCI) on MPR, left ventricular ejection fraction (LVEF), angina, quality of life and six-minute walking distance (6MWD). Methods and Results To date, 40 patients have undergone contrast-enhanced first-pass perfusion CMR, modified angina questionnaire, quality of life Short-Form 36 (SF-36) assessment and six-minute walk test before and 6 months after successful PCI. MPR was analysed by measuring the relative upslope of the signal intensity curves at stress and rest calculated for a 16 segment AHA model. MPR increased by 0.59 (95% CI, 0.32 to 0.87), p Conclusions Successful recanalisation of CTO by PCI leads to a reduction in ischaemia measured by MPR, as well as an improvement in LVEF (particularly in impaired ventricles), frequency of angina, overall quality of life and 6MWD at 6 months.

Effects of tracer arrival time on the accuracy of high-resolution (voxel-wise) myocardial perfusion maps from contrast-enhanced first-pass perfusion magnetic resonance.

First-pass perfusion cardiac magnetic resonance(CMR) allows the quantitative assessment of myocardial blood flow(MBF). However, flow estimates are sensitive to the delay between the arterial and myocardial tissue tracer arrival time (tOnset) and the accurate estimation of MBF relies on the precise identification of tOnset . The aim of this study is to assess the sensitivity of the quantification process to tOnset at voxel level. Perfusion data were obtained from series of simulated data, a hardware perfusion phantom, and patients. Fermi deconvolution has been used for analysis. A novel algorithm, based on sequential deconvolution,which minimizes the error between myocardial curves and fitted curves obtained after deconvolution, has been used to identify the optimal tOnset for each region. Voxel-wise analysis showed to be more sensitive to tOnset compared to segmental analysis. The automated detection of the tOnset allowed a net improvement of the accuracy of MBF quantification and in patients the identification of perfusion abnormalities in territories that were missed when a constant user-selected tOnset was used. Our results indicate that high-resolution MBF quantification should be performed with optimized tOnset values at voxel level.

The regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy patients with or without left ventricular outflow tract obstruction: Assessment with first-pass perfusion imaging using 3.0-T cardiac magnetic resonance

PurposeTo assess regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction using 3.0-T cardiac magnetic resonance (CMR) first-pass perfusion imaging. Materials and methodsForty-two HCM patients, including 25 HCM patients with left ventricular outflow tract obstruction (HOCM), 17 HCM patients without left ventricular outflow tract obstruction (NOHCM), and 14 healthy subjects underwent CMR. The left ventricular (LV) function, left ventricular end-diastolic wall thickness (EDTH), and diameter of left ventricular outflow tract (LVOT) were measured and calculated. Based on the signal–time curve of the first-pass myocardium perfusion imaging, perfusion parameters including upslope, time to peak, and peak intensity, were assessed and compared by using one-way analysis of variance and independent t tests. ResultsOn the first-pass perfusion imaging, lower upslope and peak intensity and longer time to peak were found in HCM patients compared with normal subjects (all p<0.05). In contrast to the NOHCM group, the average time to peak of the HOCM group was increased (13.30±4.82s vs 16.28±4.90s, p<0.05), but first-pass perfusion upslope was reduced (4.96±2.55 vs 2.58±0.77, p<0.05). According to the bull's-eye model, the HOCM group's average thickness of basal segments was thicker than the NOHCM group, especially the anteroseptal, inferolateral, and anterior wall values, with a corresponding lower first-pass perfusion upslope than the NOHCM group (all p<0.05). A significant correlation was observed between first-pass perfusion upslope and LV EDTH (r=−0.551, p<0.001) and LVOT diameter (r=0.472, p<0.001). ConclusionsThe regional myocardial microvascular dysfunction differences in hypertrophic cardiomyopathy (HCM) patients with or without left ventricular outflow tract obstruction can be detected with first-pass perfusion CMR imaging.

Perfusion dephasing discriminated between coronary microvascular disease and multivessels coronary artery disease

Background Non-invasive imaging methods cannot reliably differentiate reliably between coronary microvascular dysfunction (CMD) and multi-vessel coronary artery disease (including left main coronary artery disease; CAD) as both these conditions may result in diffuse myocardial ischemia, which on visual and quantitative analysis can have a similar appearance. Consequently, patients are subjected to invasive angiography, and coronary microvascular dysfunction is diagnosed after demonstrating normal coronary arteries in patients with myocardial ischemia. We hypothesized that the spatial and temporal distribution of the first-pass perfusion of the left ventricular myocardium is fundamentally different between these conditions. The aim of this study was to evaluate the spatial and temporal distribution of perfusion (perfusion dephasing analysis) to differentiate CMD and multivessel CAD. Methods This study included a total of 52 patients. All subjects underwent adenosine-stress first-pass perfusion CMR. Patients with a visually positive perfusion cardiac magnetic resonance (CMR) and functional multivessel disease (fractional flow reserve (FFR) ≤0.8 in at least 2 vessels; n = 25) or a visually positive perfusion CMR and angiographically smooth coronary arteries (CMD Group; n = 27) were included. The datasets were analysed visually, quantified with Fermi deconvolution and assessed for perfusion dephasing (coefficient of variation of the time to peak of the myocardial signal intensity curve). Results Visual and quantitative analysis allowed a reliable diagnosis of significant CAD, but could not distinguish patients with multivessel CAD from patients with CMD as the total extent and severity of ischemia was similar between the two groups. In patients with CAD, perfusion analysis showed significant dephasing proportional to the extent and severity of the epicardial stenoses (average perfusion dephasing in the multivessel CAD group 17% ± 8%). In contrast, in patients with CMD there was very little perfusion dephasing (7% ± 2%;p 10.1% (p < 0.001; area under the ROC curve = 0.96). Conclusions In conclusion, perfusion-dephasing analysis, a novel method to measure temporal differences of myocardial perfusion, is highly accurate in distinguishing patients with functionally significant multivessel CAD from patients with CMD. Funding

Groupwise Elastic Registration by a New Sparsity-Promoting Metric: Application to the Alignment of Cardiac Magnetic Resonance Perfusion Images

This paper proposes a methodology for the joint alignment of a sequence of images based on a groupwise registration procedure by using a new family of metrics that exploit the expected sparseness of the temporal intensity curves corresponding to the aligned points. Therefore, this methodology is able to tackle the alignment of temporal sequences of images in which the represented phenomenon varies in time. Specifically, we have applied it to the correction of motion in contrast-enhanced first-pass perfusion cardiac magnetic resonance images. The time sequence is elastically registered as a whole by using the aforementioned family of multi-image metrics and jointly optimizing the parameters of the transformations involved. The proposed metrics are able to cope with dynamic changes in the intensity content of corresponding points in the sequence guided by the assumption that these changes allow for a sparse representation in a properly selected frame. Results have shown the statistically significant improvement in the performance of the proposed metric with respect to previous groupwise registration metrics for the problem at hand, which is especially relevant to correct for elastic deformations.

Systemic endothelin receptor blockade in ST-segment elevation acute coronary syndrome protects the microvasculature: a randomised pilot study

ST-elevation acute coronary syndrome (STE-ACS) is characterised by compromised blood flow at the epicardial and microvascular levels. Endothelin-1 (ET-1) is a mediator of microvascular dysfunction and adverse cardiac remodelling. We hypothesised that administration of an endothelin type A (ETA) receptor antagonist (BQ-123; Clinalfa, Läufelfingen, Switzerland) may protect microvascular function. In this proof-of-concept, randomised, double-blind, placebo-controlled trial, patients with posterior-wall STE-ACS (n=57) were randomly assigned to receive intravenous BQ-123 at 400 nmol/minute or placebo over 60 minutes, starting at the onset of primary percutaneous coronary intervention (PCI). Time to myocardial contrast wash-in of the infarcted segment assessed by first-pass perfusion cardiac magnetic resonance imaging was the primary efficacy endpoint. Secondary endpoints included enzymatic infarct size and left ventricular ejection fraction (LVEF). In patients randomised to BQ-123 we observed shorter microvessel perfusion delays six days after PCI (1.8 sec [0.7-3.4] versus 3.3 sec [2.3-5.4] in placebo-treated patients, p=0.005). The treatment group demonstrated smaller enzymatic infarct sizes (p=0.014). All patients were alive at six months, with an LVEF of 63% (58-69) in patients randomised to BQ-123 and 59% (51-66) in placebo-treated patients (p=0.047). Administration of an ETA receptor blocker during primary PCI in patients with STE-ACS is safe and may improve tissue-level perfusion and LVEF.

Presence and Extent of Cardiac Magnetic Resonance Microvascular Obstruction in Reperfused Non-ST-Elevated Myocardial Infarction and Correlation with Infarct Size and Myocardial Enzyme Release

Objective: Microvascular obstruction (MO) is a factor of adverse outcome in patients with ST-elevated myocardial infarction (STEMI). We assessed the presence and extent of MO and its relationship with infarct size and left ventricular (LV) functional parameters after acute non-ST-elevated myocardial infarction (NSTEMI). Methods: Twenty-five patients with first acute NSTEMI underwent a cine and first-pass perfusion cardiac magnetic resonance (CMR) study, with late gadolinium enhancement imaging 72 h after myocardial infarction. Results: MO was detected in 32% of patients, and its extent comprised 0.5–3.1% of the total LV mass (mean 1.9 ± 1.2%). Patients with MO had a significantly larger infarct size than patients without (14.1 ± 5.9 vs. 5.3 ± 4.1% LV mass; p < 0.001). There was no significant difference between both groups for the LV functional parameters and LV ejection fraction (58.5 ± 6.8 vs. 62.6 ± 9.6%; p = 0.29). Patients with MO showed a higher troponin I release (570 ± 364 vs. 148 ± 103 IU; p = 0.003) and a higher creatine kinase release (29,887 ± 18,263 vs. 10,287 ± 5,283 IU; p = 0.007). Conclusions: In patients with acute NSTEMI, MO has a frequency similar to that observed in patients with STEMI and also correlates with the infarct extent. The prognostic significance on clinical outcome remains to be shown in this specific population.