Objective

The purpose of this paper is to accelerate cardiac diffusion tensor imaging (CDTI) by integrating low-rankness and compressed sensing.

Methods

Diffusion-weighted images exhibit both transform sparsity and low-rankness. These properties can jointly be exploited to accelerate CDTI, especially when a phase map is applied to correct for the phase inconsistency across diffusion directions, thereby enhancing low-rankness. The proposed method is evaluated both ex vivo and in vivo, and is compared to methods using either a low-rank or sparsity constraint alone.

Results

Compared to using a low-rank or sparsity constraint alone, the proposed method preserves more accurate helix angle features, the transmural continuum across the myocardium wall, and mean diffusivity at higher acceleration, while yielding significantly lower bias and higher intraclass correlation coefficient.

Conclusion

Low-rankness and compressed sensing together facilitate acceleration for both ex vivo and in vivo CDTI, improving reconstruction accuracy compared to employing either constraint alone.

Significance

Compared to previous methods for accelerating CDTI, the proposed method has the potential to reach higher acceleration while preserving myofiber architecture features, which may allow more spatial coverage, higher spatial resolution, and shorter temporal footprint in the future.

Objectives

The aim of this work is the development of coronary atherosclerosis T₁-weighted characterization with integrated anatomical reference (CATCH) technique and the validation by comparison with high-risk plaque features (HRPF) observed on intracoronary optical coherence tomography (OCT) and invasive coronary angiography.

Background

T₁-weighted cardiac magnetic resonance with or without contrast media has been used for characterizing coronary atherosclerosis showing promising prognostic value. Several limitations include: 1) coverage is limited to proximal coronary segments; 2) spatial resolution is low and often anisotropic; and 3) a separate magnetic resonance angiography acquisition is needed to localize lesions.

Methods

CATCH acquired dark-blood T₁-weighted images and bright-blood anatomical reference images in an interleaved fashion. Retrospective motion correction with 100% respiratory gating efficiency was achieved. Reference control subjects (n = 13) completed both pre- and post-contrast scans. Stable angina patients (n = 30) completed pre-contrast scans, among whom 26 eligible patients also completed post-contrast scans. After cardiac magnetic resonance, eligible patients (n = 22) underwent invasive coronary angiography and OCT for the interrogation of coronary atherosclerosis. OCT images were assessed and scored for HRPF (lipid-richness, macrophages, cholesterol crystals, and microvessels) by 2 experienced analysts blinded to magnetic resonance results.

Results

Per-subject analysis showed none of the 13 reference control subjects had coronary hyperintensive plaques (CHIP) in either pre-contrast or post-contrast CATCH. Five patients had CHIP on pre-contrast CATCH and 5 patients had CHIP on post-contrast CATCH. Patients with CHIP had greater lipid abnormality than those without. Per-segment analysis showed elevated pre- and post-contrast plaque to myocardium signal ratio in the lesions with HRPF versus those without. Positive correlation was observed between plaque to myocardium signal ratio and OCT HRPF scoring. CHIP on pre-contrast CATCH were associated with significantly higher stenosis level than non-CHIP on invasive coronary angiography.

Conclusions

CATCH provided accelerated whole heart coronary plaque characterization with simultaneously acquired anatomical reference. CHIP detected by CATCH showed positive association with high-risk plaque features on invasive imaging studies.

Purpose

To investigate the feasibility of blood pressure difference measurement, ΔP, across the coronary artery using phase contrast (PC)-MRI for potential noninvasive assessment of the functional significance of coronary artery stenosis.

Methods

Three-directional velocities in the coronary arteries acquired using 2D-PC-MRI were used with the Navier-Stokes equations to derive ΔP. Repeat phantom studies were performed to assess the reproducibility of flow velocity and ΔP. ΔP derived using PC-MRI (ΔP_MR ) and that obtained using pressure transducer (ΔP_PT ) were compared. Reproducibility of coronary flow velocity was assessed in healthy controls (n = 11). Patients with suspected coronary artery disease (n = 6) were studied to evaluate the feasibility of ΔP_MR measurement across a coronary stenosis.

Results

Phantom: Good overall reproducibility of flow velocity and ΔP measurements and excellent correlation (ΔP_MR vs ΔP_PT ) was observed: intraclass correlation (ICC) of 0.95(V_z ), 0.72(V_x ), 0.73(V_y ), and 0.87(ΔP_MR ) and R²  = 0.94, respectively. Human: Good reproducibility of coronary flow velocity was observed: ICC of 0.94/0.95(V_z ), 0.76/0.74(V_x ), and 0.80/0.77(V_y ) at cardiac phase 1/2. Significant (p = 0.025) increase in ΔP_MR was observed in patients (6.40 ± 4.43 mmHg) versus controls (0.70 ± 0.57 mmHg).

Conclusion

ΔP_MR in the coronary arteries is feasible. Upon further validation using the invasive measure, ΔP_MR has the potential for noninvasive assessment of coronary artery stenosis. Magn Reson Med 77:529-537, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Objectives

This study evaluated the association between atherosclerotic plaque characteristics (APCs) by coronary computed tomographic angiography (CTA), and lesion ischemia by fractional flow reserve (FFR).

Background

FFR is the gold standard for determining lesion ischemia. Although APCs by CTA-including aggregate plaque volume % (%APV), positive remodeling (PR), low attenuation plaque (LAP), and spotty calcification (SC)-are associated with future coronary syndromes, their relationship to lesion ischemia is unclear.

Methods

252 patients (17 centers, 5 countries; mean age 63 years; 71% males) underwent coronary CTA, with FFR performed for 407 coronary lesions. Coronary CTA was interpreted for <50% and ≥50% stenosis, with the latter considered obstructive. APCs by coronary CTA were defined as: 1) PR, lesion diameter/reference diameter >1.10; 2) LAP, any voxel <30 Hounsfield units; and 3) SC, nodular calcified plaque <3 mm. Odds ratios (OR) and net reclassification improvement of APCs for lesion ischemia, defined by FFR ≤0.8, were analyzed.

Results

By FFR, ischemia was present in 151 lesions (37%). %APV was associated with a 50% increased risk of ischemia per 5% additional APV. PR, LAP, and SC were associated with ischemia, with a 3 to 5 times higher prevalence than in nonischemic lesions. In multivariable analyses, a stepwise increased risk of ischemia was observed for 1 (OR: 4.0, p < 0.001) and ≥2 (OR: 12.1, p < 0.001) APCs. These findings were APC dependent, with PR (OR: 5.3, p < 0.001) and LAP (OR: 2.1, p = 0.038) associated with ischemia, but not SC. When examined by stenosis severity, PR remained a predictor of ischemia for all lesions, whereas %APV and LAP were associated with ischemia for only ≥50%, but not for <50%, stenosis.

Conclusions

%APV and APCs by coronary CTA improve identification of coronary lesions that cause ischemia. PR is associated with all ischemia-causing lesions, whereas %APV and LAP are only associated with ischemia-causing lesions ≥50%. (Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography; NCT01233518).

Coronary ¹⁸F-sodium fluoride (¹⁸F-NaF) PET identifies ruptured plaques in patients with recent myocardial infarction and localizes to atherosclerotic lesions with active calcification. Most studies to date have performed the PET acquisition 1 h after injection. Although qualitative and semiquantitative analysis is feasible with 1-h images, residual blood-pool activity often makes it difficult to discriminate plaques with ¹⁸F-NaF uptake from noise. We aimed to assess whether delayed PET performed 3 h after injection improves image quality and uptake measurements. Methods: Twenty patients (67 ± 7 y old, 55% male) with stable coronary artery disease underwent coronary CT angiography (CTA) and PET/CT both 1 h and 3 h after the injection of 266.2 ± 13.3 MBq of ¹⁸F-NaF. We compared the visual pattern of coronary uptake, maximal background (blood pool) activity, noise, SUV_max, corrected SUV_max (cSUV_max), and target-to-background (TBR) ratio in lesions defined by CTA on 1-h versus 3-h ¹⁸F-NaF PET. Results: On 1-h PET, 26 CTA lesions with ¹⁸F-NaF PET uptake were identified in 12 (60%) patients. On 3-h PET, we detected ¹⁸F-NaF PET uptake in 7 lesions that were not identified on 1-h PET. The median cSUV_max and TBRs of these lesions were 0.48 (interquartile range [IQR], 0.44-0.51) and 1.45 (IQR, 1.39-1.52), respectively, compared with -0.01 (IQR, -0.03-0.001) and 0.95 (IQR, 0.90-0.98), respectively, on 1-h PET (both P < 0.001). Across the entire cohort, 3-h PET SUV_max was similar to 1-h PET measurements (1.63 [IQR, 1.37-1.98] vs. 1.55 [IQR, 1.43-1.89], P = 0.30), and the background activity was lower (0.71 [IQR, 0.65-0.81] vs. 1.24 [IQR, 1.05-1.31], P < 0.001). On 3-h PET, TBR, cSUV_max, and noise were significantly higher (respectively: 2.30 [IQR, 1.70-2.68] vs. 1.28 [IQR, 0.98-1.56], P < 0.001; 0.38 [IQR, 0.27-0.70] vs. 0.90 [IQR, 0.64-1.17], P < 0.001; and 0.10 [IQR, 0.09-0.12] vs. 0.07 [IQR, 0.06-0.09], P = 0.02). Median cSUV_max and TBR increased by 92% (range, 33%-225%) and 80% (range, 20%-177%), respectively. Conclusion: Blood-pool activity decreases on delayed imaging, facilitating the assessment of ¹⁸F-NaF uptake in coronary plaques. Median TBR increases by 80%, leading to the detection of more plaques with significant uptake than are detected using the standard 1-h protocol. A greater than 1-h delay may improve the detection of ¹⁸F-NaF uptake in coronary artery plaques.

Background

The natural history of coronary artery disease (CAD) in patients with low-to-intermediate risk is not well characterized. Although earlier invasive serial studies have documented the progression of atherosclerotic burden, most were focused on high-risk patients only. The PARADIGM registry is a large, prospective, multinational dynamic observational registry of patients undergoing serial coronary computed tomographic angiography (CCTA). The primary aim of PARADIGM is to characterize the natural history of CAD in relation to clinical and laboratory data.

Design

The PARADIGM registry (ClinicalTrials.govNCT02803411) comprises ≥2,000 consecutive patients across 9 cluster sites in 7 countries. PARADIGM sites were chosen on the basis of adequate CCTA volume, site CCTA proficiency, local demographic characteristics, and medical facilities to ensure a broad-based sample of patients. Patients referred for clinically indicated CCTA will be followed up and enrolled if they had a second CCTA scan. Patients will also be followed up beyond serial CCTA performance to identify adverse CAD events that include cardiac and noncardiac death, myocardial infarction, unstable angina, target vessel revascularization, and CAD-related hospitalization.

Summary

The results derived from the PARADIGM registry are anticipated to add incremental insight into the changes in CCTA findings in accordance with the progression or regression of CAD that confer prognostic value beyond demographic and clinical characteristics.

Objective

Data describing the prevalence, characteristics and management of coronary chronic total occlusions (CTOs) in patients undergoing coronary CT angiography (CCTA) have not been reported. The purpose of this study was to determine the prevalence, characteristics and treatment strategies of CTO identified by CCTA.

Methods

We identified 23 745 patients who underwent CCTA for suspected coronary artery disease (CAD) from the prospective international CCTA registry. Baseline clinical data were collected, and allocation to early coronary revascularisation performed within 90 days of CCTA was determined. Multivariable hierarchical mixed-effects logistic regression reporting OR with 95% CI was performed.

Results

The prevalence of CTO was 1.4% (342/23 745) in all patients and 6.2% in patients with obstructive CAD (≥50% stenosis). The presence of CTO was independently associated with male sex (OR 3.12, 95% CI 2.39 to 4.08, p<0.001), smoking (OR 2.02, 95% CI 1.55 to 2.64, p<0.001), diabetes (OR 1.60, 95% CI 1.22 to 2.11, p=0.001), typical angina (OR 1.51, 95% CI 1.12 to 2.06, p=0.008), hypertension (OR 1.47, 95% CI 1.14 to 1.88, p=0.003), family history of CAD (OR 1.30, 95% CI 1.01 to 1.67, p=0.04) and age (OR 1.06, 95% CI 1.05 to 1.07, p<0.001). Most patients with CTO (61%) were treated medically, while 39% underwent coronary revascularisation. In patients with severe CAD (≥70% stenosis), CTO independently predicted revascularisation by coronary artery bypass grafting (OR 3.41, 95% CI 2.06 to 5.66, p<0.001), but not by percutaneous coronary intervention (p=0.83).

Conclusions

CTOs are not uncommon in a contemporary CCTA population, and are associated with age, gender, angina status and CAD risk factors. Most individuals with CTO undergoing CCTA are managed medically with higher rates of surgical revascularisation in patients with versus without CTO.

Trial registration number

ClinicalTrials.gov identifier NCT01443637.

Objective

We sought to examine the risk of mortality associated with nonobstructive coronary artery disease (CAD) and to determine the impact of baseline statin and aspirin use on mortality.

Approach and results

Coronary computed tomographic angiography permits direct visualization of nonobstructive CAD. To date, the prognostic implications of nonobstructive CAD and the potential benefit of directing therapy based on nonobstructive CAD have not been carefully examined. A total of 27 125 consecutive patients who underwent computed tomographic angiography (12 enrolling centers and 6 countries) were prospectively entered into the COronary CT Angiography EvaluatioN For Clinical Outcomes: An InteRnational Multicenter (CONFIRM) registry. Patients, without history of previous CAD or obstructive CAD, for whom baseline statin and aspirin use was available were analyzed. Each coronary segment was classified as normal or nonobstructive CAD (1%-49% stenosis). Patients were followed up for a median of 27.2 months for all-cause mortality. The study comprised 10 418 patients (5712 normal and 4706 with nonobstructive CAD). In multivariable analyses, patients with nonobstructive CAD had a 6% (95% confidence interval, 1%-12%) higher risk of mortality for each additional segment with nonobstructive plaque (P=0.021). Baseline statin use was associated with a reduced risk of mortality (hazard ratio, 0.44; 95% confidence interval, 0.28-0.68; P=0.0003), a benefit that was present for individuals with nonobstructive CAD (hazard ratio, 0.32; 95% confidence interval, 0.19-0.55; P<0.001) but not for those without plaque (hazard ratio, 0.66; 95% confidence interval, 0.30-1.43; P=0.287). When stratified by National Cholesterol Education Program/Adult Treatment Program III, no mortality benefit was observed in individuals without plaque. Aspirin use was not associated with mortality benefit, irrespective of the status of plaque.

Conclusions

The presence and extent of nonobstructive CAD predicted mortality. Baseline statin therapy was associated with a significant reduction in mortality for individuals with nonobstructive CAD but not for individuals without CAD.

Clinical trial registration

URL: http://clinicaltrials.gov/. Unique identifier NCT01443637.

Aims

This study explored the coronary plaque volume change (PVC) according to the change of percent body mass index (BMI) and categorical BMI group using serial coronary computed tomography angiography (CCTA).

Methods and results

A total of 1568 subjects who underwent serial CCTA with available BMI at baseline (CCTA1) and follow-up (CCTA2) were included. Median inter-scan period was 3.3 (interquartile range: 2.6-4.6) years. Quantitative assessment of coronary plaque was performed at both scans. All participants were categorized into three BMI (kg/m2) groups: normal: <25.0; overweight: 25.0-29.9; and obesity: ≥30.0. During follow-up, there were no significant differences in annualized PVC according to the 5% change of BMI in all BMI groups. Among 1424 (90.8%) subjects in the same BMI group at CCTA1 and CCTA2, a significant difference in annualized (PVC) was observed among the three groups. In 144 (9.2%) subjects with the change in their BMI group at CCTA2 compared their results at CCTA1, annualized PVC was not different compared with subjects in the same BMI group during follow-up. The percent change of BMI was not significantly related to the annualized PVC after adjusting confounding factors. Male gender [odds ratio (OR): 1.38; 95% confidence interval (CI): 1.05-1.81; P = 0.022], baseline plaque volume (OR: 1.07; 95% CI: 1.05-1.09; P < 0.001), and baseline overweight or obesity (OR: 1.35; 95% CI: 1.04-1.77; P = 0.027) were independently associated with coronary plaque progression.

Conclusion

Over the near term, longitudinal small changes in BMI were not associated with changes in coronary plaque volume although baseline BMI was.

Clinical trial registration

ClinicalTrials.gov NCT02803411.

Background

Diagnosis of coronary artery disease and management strategies have relied solely on the presence of diameter stenosis ≥50%. We assessed whether direct quantification of plaque burden (PB) and plaque characteristics assessed by coronary computed tomography angiography could provide additional value in terms of predicting rapid plaque progression.

Methods and results

From a 13-center, 7-country prospective observational registry, 1345 patients (60.4±9.4 years old; 57.1% male) who underwent repeated coronary computed tomography angiography >2 years apart were enrolled. For conventional angiographic analysis, the presence of stenosis ≥50%, number of vessel involved, segment involvement score, and the presence of high-risk plaque feature were determined. For quantitative analyses, PB and annual change in PB (△PB/y) in the entire coronary tree were assessed. Clinical outcomes (cardiac death, nonfatal myocardial infarction, and coronary revascularization) were recorded. Rapid progressors, defined as a patient with ≥median value of △PB/y (0.33%/y), were older, more frequently male, and had more clinical risk factors than nonrapid progressors (all P<0.05). After risk adjustment, addition of baseline PB improved prediction of rapid progression to each angiographic assessment of coronary artery disease, and the presence of high-risk plaque further improved the predictive performance (all P<0.001). For prediction of adverse outcomes, adding both baseline PB and △PB/y showed best predictive performance (C statistics, 0.763; P<0.001).

Conclusions

Direct quantification of atherosclerotic PB in addition to conventional angiographic assessment of coronary artery disease might be beneficial for improving risk stratification of coronary artery disease.

Clinical trial registration

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02803411.