Fully automated pixel-wise quantitative CMR-myocardial perfusion with CMR-coronary angiography to detect hemodynamically significant coronary artery disease.

OBJECTIVES: We applied a fully automated pixel-wise post-processing framework to evaluate fully quantitative cardiovascular magnetic resonance myocardial perfusion imaging (CMR-MPI). In addition, we aimed to evaluate the additive value of coronary magnetic resonance angiography (CMRA) to the diagnostic performance of fully automated pixel-wise quantitative CMR-MPI for detecting hemodynamically significant coronary artery disease (CAD). METHODS: A total of 109 patients with suspected CAD were prospectively enrolled and underwent stress and rest CMR-MPI, CMRA, invasive coronary angiography (ICA), and fractional flow reserve (FFR). CMRA was acquired between stress and rest CMR-MPI acquisition, without any additional contrast agent. Finally, CMR-MPI quantification was analyzed by a fully automated pixel-wise post-processing framework. RESULTS: Of the 109 patients, 42 patients had hemodynamically significant CAD (FFR ≤ 0.80 or luminal stenosis ≥ 90% on ICA) and 67 patients had hemodynamically non-significant CAD (FFR ˃ 0.80 or luminal stenosis < 30% on ICA) were enrolled. On the per-territory analysis, patients with hemodynamically significant CAD had higher myocardial blood flow (MBF) at rest, lower MBF under stress, and lower myocardial perfusion reserve (MPR) than patients with hemodynamically non-significant CAD (p < 0.001). The area under the receiver operating characteristic curve of MPR (0.93) was significantly larger than those of stress and rest MBF, visual assessment of CMR-MPI, and CMRA (p < 0.05), but similar to that of the integration of CMR-MPI with CMRA (0.90). CONCLUSIONS: Fully automated pixel-wise quantitative CMR-MPI can accurately detect hemodynamically significant CAD, but the integration of CMRA obtained between stress and rest CMR-MPI acquisition did not provide significantly additive value. KEY POINTS: • Full quantification of stress and rest cardiovascular magnetic resonance myocardial perfusion imaging can be postprocessed fully automatically, generating pixel-wise myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) maps. • Fully quantitative MPR provided higher diagnostic performance for detecting hemodynamically significant coronary artery disease, compared with stress and rest MBF, qualitative assessment, and coronary magnetic resonance angiography (CMRA). • The integration of CMRA and MPR did not significantly improve the diagnostic performance of MPR alone.

The prognostic value of global myocardium strain by CMR-feature tracking in immune checkpoint inhibitor-associated myocarditis.

OBJECTIVES: Immune checkpoint inhibitor (ICI)-associated myocarditis is a potentially fatal complication. Sparse published researches evaluated the prognostic value of cardiovascular magnetic resonance feature tracking (CMR-FT) for ICI-associated myocarditis. METHODS: In the single-center retrospective study, 52 patients with ICI-associated myocarditis and CMR were included from August 2018 to July 2021. The ICI-associated myocarditis was diagnosed by using the clinical criteria of the European Society of Cardiology guidelines. Major adverse cardiovascular events (MACE) were comprised of cardiovascular death, cardiogenic shock, cardiac arrest, and complete heart block. RESULTS: During a median follow-up of 171 days, 14 (27%) patients developed MACE. For patients with MACE, the global circumferential strain (GCS), global radial strain (GRS), global longitudinal strain (GLS), and left ventricular ejection fraction (LVEF) were significantly worse and native T1 values and late gadolinium enhancement (LGE) extent were significantly increased, compared with patients without MACE (p < 0.05). The GLS remained the independent factor associated with a higher risk of MACE (hazard ratio (HR): 2.115; 95% confidence interval (CI): 1.379-3.246; p = 0.001) when adjusting for LVEF, LGE extent, age, sex, body mass index, steroid treatment, and prior cardiotoxic chemotherapy or radiation. After adjustment for LVEF, the GLS remained the independent risk factor associated with a higher rate of MACE among patients with a preserved LVEF (HR: 1.358; 95% CI: 1.007-1.830; p = 0.045). CONCLUSIONS: GLS could provide independent prognostic value over GCS, GRS, traditional CMR features, and clinical features in patients with ICI-associated myocarditis. KEY POINTS: • The global circumferential strain (GCS), global radial strain (GRS), and global longitudinal strain (GLS) by cardiovascular magnetic resonance feature tracking were significantly impaired in patients with an immune checkpoint inhibitor (ICI)-associated myocarditis. • GLS was still significantly impaired in patients with preserved left ventricular ejection fraction. • The worse GLS was an independent risk factor over GCS, GRS, traditional CMR features, and clinical features for predicting major adverse cardiovascular events in patients with ICI-associated myocarditis.

Unenhanced Whole-Heart Coronary MRA: Prospective Intraindividual Comparison of 1.5-T SSFP and 3-T Dixon Water-Fat Separation GRE Methods Using Coronary Angiography as Reference.

BACKGROUND. Coronary MRA is commonly performed at 1.5 T using SSFP acquisitions. Coronary MRA performed at 3 T using SSFP is limited due to impaired fat suppression and has been typically investigated using contrast-enhanced techniques. A Dixon fat-water separation gradient-recalled echo (GRE) method may enable high-quality unenhanced 3-T coronary MRA. OBJECTIVE. The purpose of this study was to compare 1.5-T SSFP and 3-T Dixon water-fat separation GRE methods for unenhanced whole-heart coronary MRA in patients with suspected coronary artery disease (CAD). METHODS. This prospective study included 44 patients (27 men and 17 women; mean age, 59 ± 8 [SD] years) with an intermediate to high risk of CAD who underwent both 1.5-T SSFP and 3-T Dixon GRE coronary MRA examinations before undergoing coronary angiography (CAG). Two radiologists independently assessed coronary arteries in terms of subjective image quality (on a scale of 1-5, with 5 denoting the highest image quality), number of visible segments, apparent contrast-to-noise ratio (CNR; vs myocardium), and presence of significant stenoses. Methods were compared using the mean of the readers' values for apparent CNR and using consensus interpretations for other measures. CAG served as the reference standard for detecting the presence of stenoses. RESULTS. Expressed as a kappa coefficient, interobserver agreement was 0.85 for image quality, 0.85 for segment visibility, and 0.83 for stenosis, and expressed as an intraclass correlation coefficient, interobserver agreement was 0.92 for apparent CNR. The mean overall image quality score was 4.0 ± 1.1 for 3-T Dixon GRE versus 3.0 ± 1.2 for 1.5-T SSFP. The percentage of visible segments for 3-T Dixon GRE versus 1.5-T SSFP was 96.7% versus 88.9% for all segments, 96.9% versus 90.1% for distal segments, and 93.1% versus 77.2% for branch segments. The mean overall apparent CNR was 93.2 ± 29.2 for 3-T Dixon GRE versus 80.8 ± 27.9 for 1.5-T SSFP. The 3-T Dixon GRE method, compared with the 1.5-T SSFP method, showed higher sensitivity and specificity in per-vessel analysis (87.9% vs 77.3% and 83.3% vs 60.6%, respectively), per-segment analysis (84.6% vs 74.8% and 90.9% vs 79.6%, respectively), and per-segment analysis of distal and branch segments (89.7% vs 75.9% and 89.7% vs 73.7%, respectively). CONCLUSION. For unenhanced coronary MRA, 3-T unenhanced Dixon GRE had better image quality and diagnostic performance than 1.5-T SSFP, particularly for distal and branch segments. CLINICAL IMPACT. The 3-T Dixon GRE technique may be preferred to the current clinical standard of the 1.5-T SSFP technique for unenhanced coronary MRA.

Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy: The Utility of Myocardial Strain Based on Cardiac MR Tissue Tracking.

BACKGROUND: Myocardial strain for assessment of hypertrophic cardiomyopathy (HCM) is of importance and may play a role in identifying obstruction in HCM patients. PURPOSE: To evaluate the utility of myocardial strain for detecting left ventricular (LV) outflow tract (LVOT) obstruction in HCM patients based on magnetic resonance tissue tracking. STUDY TYPE: Retrospective. POPULATION: In all, 44 adult HCM patients with LVOT obstruction and 108 adult HCM patients without LVOT obstruction. FIELD STRENGTH/SEQUENCE: 1.5 T; Steady-state free-precession cine sequence; phase-sensitive inversion-prepared segmented gradient echo sequence for late gadolinium enhancement (LGE) imaging. ASSESSMENT: Strain parameters including the local and global levels of LV myocardium and the subtraction (Sub) of myocardial strain variables between interventricular septal segments (IVSS) and noninterventricular septal segments (NIVSS) were measured for differentiating HCM with obstruction from nonobstruction. Average and maximum LV wall thickness (Average and Maximum LVWT) were also analyzed. STATISTICAL TESTS: Univariate and multivariate logistic regression analysis, area under the receiver operating characteristic (ROC) curve (AUC), intraclass correlation coefficient. RESULTS: In multivariate analysis, Average LVWT, Maximum LVWT, and the subtraction of radial peak strain (Sub Radial PS) between NIVSS and IVSS were independently associated with LVOT obstruction. The AUCs were 0.731, 0.840, and 0.890 for Average LVWT, Maximum LVWT, and Sub Radial PS, respectively. Sub Radial PS (cutoff value: 8.1%) demonstrated the highest sensitivity of 75.0% and a high specificity of 87.9% for identifying LVOT; Maximum LVWT (cutoff value: 22.9 mm) showed good sensitivity (72.7%) and specificity (83.3%). Combining Maximum LVWT >22.9 mm and Sub Radial PS > 8.1% achieved a better diagnostic performance (specificity 95.4%, sensitivity 70.5%). DATA CONCLUSION: Combining Maximum LVWT >22.9 mm and Sub Radial PS >8.1% holds promise for objectively evaluating LVOT obstruction in HCM patients with very high specificity and acceptable sensitivity. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 2.

Three-Dimensional Free-Breathing Whole-Heart Coronary Magnetic Resonance Angiography at 1.5 T: Gadobutrol-Enhanced Gradient-Echo Acquisition Sequence Versus Non-Contrast-Enhanced Steady-State Free Precession Sequence.

OBJECTIVES: The objective of this study was to compare gadobutrol-enhanced gradient-echo sequence (GRE) acquisition with T2-prepared non-contrast-enhanced steady-state free precession (SSFP) in coronary magnetic resonance angiography at 1.5 T. METHODS: Twenty-one subjects successfully completed GRE and SSFP acquisition. Signal-to-noise ratio (SNR), contrast-to-noise ratio, image quality, sharpness, visibility, length, and lumen diameter of vessels were analyzed by 2 experienced radiologists. RESULTS: The SNR at whole left circumflex artery, left main artery, and proximal left descending artery (LAD) was significantly higher in SSFP acquisition (P < 0.05). The SNR of distal LAD was slightly higher in GRE acquisition (P < 0.05). The contrast-to-noise ratio at distal LAD, proximal and distal RCA were significantly higher with GRE acquisition (P < 0.05). CONCLUSIONS: Double-dose gadobutrol-enhanced GRE and unenhanced SSFP coronary magnetic resonance angiography at 1.5 T have their own characteristics, and the combined use of the 2 methods may be taken into consideration.

3.0 T unenhanced Dixon water-fat separation whole-heart coronary magnetic resonance angiography: compressed-sensing sensitivity encoding imaging versus conventional 2D sensitivity encoding imaging.

This study was aimed to investigate 3.0 T unenhanced Dixon water-fat whole-heart CMRA (coronary magnetic resonance angiography) using compressed-sensing sensitivity encoding (CS-SENSE) and conventional sensitivity encoding (SENSE) in vitro and in vivo. The key parameters of CS-SENSE and conventional 1D/2D SENSE were compared in vitro phantom study. In vivo study, fifty patients with suspected coronary artery disease (CAD) completed unenhanced Dixon water-fat whole-heart CMRA at 3.0 T using both CS-SENSE and conventional 2D SENSE methods. We compared mean acquisition time, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and the diagnostic accuracy between two techniques. In vitro study, CS-SENSE achieved better effectiveness between higher SNR/CNR and shorter scan times using the appropriate acceleration factor compared with conventional 2D SENSE. In vivo study, CS-SENSE CMRA had better performance than 2D SENSE in terms of the mean acquisition time, SNR and CNR (7.4 ± 3.2 min vs. 8.3 ± 3.4 min, P = 0.001; SNR: 115.5 ± 35.4 vs. 103.3 ± 32.2; CNR: 101.1 ± 33.2 vs. 90.6 ± 30.1, P < 0.001 for both). The diagnostic accuracy between CS-SENSE and 2D SENSE had no significant difference on a patient-based analysis (sensitivity: 97.3% vs. 91.9%; specificity: 76.9% vs. 61.5%; accuracy: 92.0% vs. 84.0%; P > 0.05 for each). Unenhanced CS-SENSE Dixon water-fat separation whole-heart CMRA at 3.0 T can improve the SNR and CNR, shorten the acquisition time while providing equally satisfactory image quality and diagnostic accuracy compared with 2D SENSE CMRA.

Comparison of CT-derived Plaque Characteristic Index With CMR Perfusion for Ischemia Diagnosis in Stable CAD.

BACKGROUND: Coronary computed tomography angiography (CCTA) and cardiac magnetic resonance (CMR) have been used to diagnose lesion-specific ischemia in patients with coronary artery disease. The aim of this study was to investigate the diagnostic performance of CCTA-derived plaque characteristic index compared with myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) derived from CMR perfusion in the assessment of lesion-specific ischemia. METHODS: Between October 2020 and March 2022, consecutive patients with suspected or known coronary artery disease, who were clinically referred for invasive coronary angiography were prospectively enrolled. All participants sequentially underwent CCTA and CMR and invasive fractional flow reserve within 2 weeks. The diagnostic performance of CCTA-derived plaque characteristics, CMR perfusion-derived stress MBF, and MPR were compared. Lesions with fractional flow reserve ≤0.80 were considered to be hemodynamically significant stenosis. RESULTS: Nighty-two patients with 141 vessels were included in this study. Plaque length, minimum luminal area, plaque area, percent area stenosis, total atheroma volume, vessel volume, lipid-rich volume, spotty calcium, napkin-ring signs, stress MBF, and MPR in flow-limiting stenosis group were significantly different from nonflow-limiting group. The overall accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of lesion-specific ischemia diagnosis were 61.0%, 55.3%, 63.1%, 35.6%, and 79.3% for stress MBF, and 89.4%, 89.5%, 89.3%, 75.6%, 95.8% for MPR; meanwhile, 82.3%, 79.0%, 84.5%, 65.2%, and 91.6% for CCTA-derived plaque characteristic index. CONCLUSIONS: In our prospective study, CCTA-derived plaque characteristics and MPR derived from CMR performed well in diagnosing lesion-specific myocardial ischemia and were significantly better than stress MBF in stable coronary artery disease.

Applying quantitative CMR parameters for detecting myocardial lesion in immune checkpoint inhibitors-associated myocarditis.

PURPOSE: Sparse researches evaluated the quantitative cardiovascular magnetic resonance (CMR) parameters for immune checkpoint inhibitors (ICI)-associated myocarditis. We aimed to apply quantitative CMR mappings and late gadolinium enhancement (LGE) extent for detecting ICI-associated myocarditis. METHOD: The retrospective study included patients with ICI-associated myocarditis and CMR examination from August 2018 to August 2021 in our hospital. ICI-associated myocarditis was clinically diagnosed based on the clinical criteria by European Society of Cardiology guidelines. The multiparametric CMR images including T2 mapping and black blood T2-weighted images were used to evaluate myocardial edema. The myocardial edema ratio (ER) ≥ 2.0 was applied for determining myocardial edema on T2-weighted images. RESULTS: 56 patients with ICI-associated myocarditis were included. The global T2 value and native T1 value of patients with ICI-associated myocarditis were significantly higher than the reference ranges in our hospital (p < 0.05). The rate of elevated global T2 value (92%) was significantly higher than those of abnormal native T1 value (73%), ER (52%) and LGE presence (68%) in patients with ICI-associated myocarditis (p < 0.05). The LGE extent and left ventricular ejection fraction of patients with ICI-associated myocarditis were 10.38 ± 9.64% and 56.42 ± 8.54%, respectively. LGE extent inversely correlated with left ventricular ejection fraction (r = -0.38, p = 0.004) but positively correlated with native T1 value (r = 0.28, p < 0.04) and extracellular volume (r = 0.50, p = 0.001). CONCLUSIONS: T2 mapping could detect higher rate of patients with ICI-associated myocarditis than native T1 mapping, ER and LGE presence. LGE extent inversely correlated with left ventricular ejection fraction but positively correlated with native T1 value and extracellular volume in patients with ICI-associated myocarditis.

Role of collateral flow in infarct border zone extent and contractile function in patients with chronic coronary total occlusion.

PURPOSE: There is a paucity of data regarding the border zone parameters in patients with chronic coronary total occlusion (CTO). We investigated the border zone extent and contractile function and their associations with collateral flow. METHODS: CTO patients (n = 47) and sex- and age-matched volunteers (n = 15) were prospectively enrolled and underwent cardiac MRI examinations to acquire cine and late-gadolinium enhancement (LGE) images. Myocardial peak strain (PS) and the time to PS were determined at the segmental level and global level. Infarct, border zone, adjacent, and remote regions were defined according to the transmural extent of infarction (TEI) by LGE at each segment. Angiographic collateral flow was evaluated using the Rentrop grading system. RESULTS: CTO patients with well-developed collateral flow had a higher TEI in border zone regions compared to patients with poorly developed collateral flow (p = 0.02). Conversely, CTO patients with poorly developed collaterals showed a higher TEI in infarct regions (p < 0.01). Enhanced border function, characterized by greater PS and earlier time to PS, was noted in well-developed collaterals (all p < 0.05). In the multivariate linear analyses, the level of collateral flow was an independent predictor of the border zone extent (ß = 0.40, p = 0.02) and contractile function (radial: ß = -0.42, p = 0.02; circumferential: ß = 0.39, p = 0.02; and longitudinal: ß = 0.47, p < 0.01). CONCLUSIONS: In CTO patients, the presence of well-developed collateral flow was closely linked to a greater extent of LGE and contractile function in border zone regions. Our findings shed light on the cardiac MRI-based pathophysiological underpinning in border zone regions, which could offer complementary and prognostic information in clinical practice.

Applying Nitroglycerin at Coronary MR Angiography at 1.5 T: Diagnostic Performance of Coronary Vasodilation in Patients with Coronary Artery Disease.

PURPOSE: To evaluate the influence of applying nitroglycerin (NTG) on detecting significant coronary artery disease (CAD) and NTG-induced coronary vasodilation using coronary MR angiography in patients suspected of having CAD. MATERIALS AND METHODS: In this prospective study conducted from November 2017 to September 2018, 70 consecutive participants suspected of having CAD were recruited. Of those, 57 patients successfully underwent pre- and post-NTG coronary MR angiography, both of which were performed during the end-systolic phase of the cardiac cycle. Significant coronary stenosis was defined at x-ray coronary angiography as stenosis of 50% or more. Participants were divided into a significant CAD group (significant stenosis) and nonsignificant CAD group (no significant stenosis) based on x-ray coronary angiography. Paired and unpaired Student t, generalized linear mixed model, and McNemar tests were used. RESULTS: The diagnostic performance of coronary MR angiography was significantly improved after NTG (P < .001). Per-patient for coronary MR angiography, from before to after NTG, respectively, the sensitivity was 97.6% (95% confidence interval [CI]: 85.6%, 99.9%) to 97.6% (95% CI: 85.6%, 99.9%), specificity was 25.0% (95% CI: 8.3%, 52.5%) to 62.5% (95% CI: 35.9%, 83.7%), positive predictive value was 76.9% (95% CI: 62.8%, 87.0%) to 87.0% (95% CI: 73.0%, 94.6%), negative predictive value was 80.0% (95% CI: 29.9%, 98.9%) to 90.9% (95% CI: 57.1%, 99.5%), and accuracy was 77.2% (95% CI: 66.3%, 88.1%) to 87.7% (95% CI: 79.2%, 96.3%). The NTG-induced coronary vasodilation was significantly lower in the significant CAD group compared with the nonsignificant CAD group. CONCLUSION: Administration of NTG significantly improved the diagnostic performance of coronary MR angiography for detecting significant CAD; however, NTG-induced coronary vasodilation was impaired in patients with significant CAD.© RSNA, 2020See also commentary by François in this issue.