Convolutional Neural Networks to Study Contrast-Enhanced Magnetic Resonance Imaging-Based Skeletal Calf Muscle Perfusion in Peripheral Artery Disease.

Peripheral artery disease (PAD) is associated with impaired blood flow in the lower extremities and histopathologic changes of the skeletal calf muscles, resulting in abnormal microvascular perfusion. We studied the use of convolution neural networks (CNNs) to differentiate patients with PAD from matched controls using perfusion pattern features from contrast-enhanced magnetic resonance imaging (CE-MRI) of the skeletal calf muscles. We acquired CE-MRI based skeletal calf muscle perfusion in 56 patients (36 patients with PAD and 20 matched controls). Microvascular perfusion imaging was performed after reactive hyperemia at the midcalf level, with a temporal resolution of 409 ms. We analyzed perfusion scans up to 2 minutes indexed from the local precontrast arrival time frame. Skeletal calf muscles, including the anterior muscle, lateral muscle, deep posterior muscle group, and the soleus and gastrocnemius muscles, were segmented semiautomatically. Segmented muscles were represented as 3-dimensional Digital Imaging and Communications in Medicine stacks of CE-MRI perfusion scans for deep learning (DL) analysis. We tested several CNN models for the 3-dimensional CE-MRI perfusion stacks to classify patients with PAD from matched controls. A total of 2 of the best performing CNNs (resNet and divNet) were selected to develop the final classification model. A peak accuracy of 75% was obtained for resNet and divNet. Specificity was 80% and 94% for resNet and divNet, respectively. In conclusion, DL using CNNs and CE-MRI skeletal calf muscle perfusion can discriminate patients with PAD from matched controls. DL methods may be of interest for the study of PAD.

Experimental Multi-Parametric MRI Characterization of Iliocaval Venous Thrombosis Pathological Changes.

OBJECTIVE: Iliocaval thrombotic obstruction is a challenging condition, especially since thrombus age and corresponding pathological remodeling at presentation are unknown, which directly impacts management. Our aim was to assess the ability of Magnetic Resonance Imaging (MRI) in determining age thresholds of experimentally created inferior vena cava (IVC) thrombosis in pigs. METHODS: We used a previously described swine model of IVC thrombosis. Animals underwent MRI at baseline, immediately after thrombosis creation and after a follow-up period extending from 2 to 28 days. Thirteen animals were divided into 3 groups according to disease's chronicity: acute (AG, N1 = 5), subacute (SAG, N2 = 4) and chronic group (CG, N3 = 4) with a mean thrombosis age of respectively 6.4 ± 2.5, 15.7 ± 2.8 and 28 ± 5.7 days. A T1 weighted volumetric interpolated breath-hold examination sequence was used to anatomically delineate IVC thrombus as a region of interest. Three other MRI sequences were used to assess thrombus signal. RESULTS: Kruskal-Wallis showed a statistically significant difference in T1 relaxation times after contrast injection (P = .026) between the 3 groups of chronicity: AG (360.2 ± 102.5) was significantly different from CG (336.7 ± 55.2 ms; P = .003) and SAG (354.1 ± 89.7 ms) was significantly different from AG (P = .027). There was a statistically significant difference in native T2 relaxation times (P = .038) between the 3 groups: AG (160 ± 86.7 ms) was significantly different from SAG (142.3 ± 55.4 ms; P = .027) and SAG was significantly different from CG (178.4 ± 11.7 ms; P = .004). CONCLUSIONS: This study highlighted MRI characteristics in a swine model that may have the potential to significantly differentiate a subacute and a chronic stage from an acute stage of deep venous thrombosis in humans. Further clinical studies in humans are warranted.

Assessing Regurgitation Severity, Adverse Remodeling, and Fibrosis with CMR in Aortic Regurgitation.

PURPOSE OF REVIEW: Cardiac magnetic resonance (CMR) is emerging as a valuable imaging modality for the assessment of aortic regurgitation (AR). In this review, we discuss the assessment of AR severity, left ventricular (LV) remodeling, and tissue characterization by CMR while highlighting the latest studies and addressing future research needs. RECENT FINDINGS: Recent studies have further established CMR-based thresholds of AR severity and LV remodeling that are associated with adverse clinical outcomes, and lower than current guideline criteria. In addition, tissue profiling with late gadolinium enhancement (LGE) and extracellular volume (ECV) quantification can reliably assess adverse myocardial tissue remodeling which is also associated with adverse outcomes. The strengths and reproducibility of CMR in evaluating ventricular volumes, tissue characteristics, and regurgitation severity position it as an excellent modality in evaluating and following AR patients. Advanced CMR techniques for the detection of tissue remodeling have shown significant potential and merit further investigation.

Noninvasive Prediction of Pulmonary Capillary Wedge Pressure in Patients With Normal Left Ventricular Ejection Fraction: Comparison of Cardiac Magnetic Resonance With Comprehensive Echocardiography.

BACKGROUND: Cardiac magnetic resonance (CMR) was recently reported to predict mean pulmonary capillary wedge pressure (PCWP). However, there is a paucity of data on its accuracy for estimation of PCWP in patients with normal left ventricular (LV) ejection fraction (EF). We sought to examine its accuracy against the invasive gold standard and to compare it with the accuracy of comprehensive echocardiography. METHODS: Stable patients with EF of ≥50% who underwent right heart catheterization, CMR, and echocardiographic imaging within 1 week were included. Pulmonary capillary wedge pressure was estimated by CMR using a previously validated equation where PCWP is estimated based on the left atrial maximum volume and LV mass. Echocardiographic estimation of PCWP was based on 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging guidelines, taking into account the presence of myocardial disease. RESULTS: The mean age of the 79 patients was 55 ± 15 years, and 58.2% were female. There were 33 patients with PCWP >15 mm Hg by right heart catheterization. Cardiac magnetic resonance prediction of PCWP had an area under the curve (AUC) = 0.72. In comparison, echocardiographic prediction of PCWP showed a higher accuracy (AUC = 0.87 vs AUC = 0.72; P = .008). CONCLUSIONS: In patients with normal LV EF, CMR estimation of mean PCWP based on LV mass and left atrial volume has modest accuracy for detecting patients with mean PCWP >15 mm Hg. Comprehensive echocardiography predicts elevated PCWP with higher accuracy in comparison with CMR.

A machine learning-based approach to identify peripheral artery disease using texture features from contrast-enhanced magnetic resonance imaging.

Diagnosing and assessing the risk of peripheral artery disease (PAD) has long been a focal point for medical practitioners. The impaired blood circulation in PAD patients results in altered microvascular perfusion patterns in the calf muscles which is the primary location of intermittent claudication pain. Consequently, we hypothesized that changes in perfusion and increase in connective tissue could lead to alterations in the appearance or texture patterns of the skeletal calf muscles, as visualized with non-invasive imaging techniques. We designed an automatic pipeline for textural feature extraction from contrast-enhanced magnetic resonance imaging (CE-MRI) scans and used the texture features to train machine learning models to detect the heterogeneity in the muscle pattern among PAD patients and matched controls. CE-MRIs from 36 PAD patients and 20 matched controls were used for preparing training and testing data at a 7:3 ratio with cross-validation (CV) techniques. We employed feature arrangement and selection methods to optimize the number of features. The proposed method achieved a peak accuracy of 94.11% and a mean testing accuracy of 84.85% in a 2-class classification approach (controls vs. PAD). A three-class classification approach was performed to identify a high-risk PAD sub-group which yielded an average test accuracy of 83.23% (matched controls vs. PAD without diabetes vs. PAD with diabetes). Similarly, we obtained 78.60% average accuracy among matched controls, PAD treadmill exercise completers, and PAD exercise treadmill non-completers. Machine learning and imaging-based texture features may be of interest in the study of lower extremity ischemia.

Stress Perfusion Cardiac Magnetic Resonance vs SPECT Imaging for Detection of Coronary Artery Disease.

BACKGROUND: GadaCAD2 was 1 of 2 international, multicenter, prospective, Phase 3 clinical trials that led to U.S. Food and Drug Administration approval of gadobutrol to assess myocardial perfusion and late gadolinium enhancement (LGE) in adults with known or suspected coronary artery disease (CAD). OBJECTIVES: A prespecified secondary objective was to determine if stress perfusion cardiovascular magnetic resonance (CMR) was noninferior to single-photon emission computed tomography (SPECT) for detecting significant CAD and for excluding significant CAD. METHODS: Participants with known or suspected CAD underwent a research rest and stress perfusion CMR that was compared with a gated SPECT performed using standard clinical protocols. For CMR, adenosine or regadenoson served as vasodilators. The total dose of gadobutrol was 0.1 mmol/kg body weight. The standard of reference was a 70% stenosis defined by quantitative coronary angiography (QCA). A negative coronary computed tomography angiography could exclude CAD. Analysis was per patient. CMR, SPECT, and QCA were evaluated by independent central core lab readers blinded to clinical information. RESULTS: Participants were predominantly male (61.4% male; mean age 58.9 ± 10.2 years) and were recruited from the United States (75.0%), Australia (14.7%), Singapore (5.7%), and Canada (4.6%). The prevalence of significant CAD was 24.5% (n = 72 of 294). Stress perfusion CMR was statistically superior to gated SPECT for specificity (P = 0.002), area under the receiver operating characteristic curve (P < 0.001), accuracy (P = 0.003), positive predictive value (P < 0.001), and negative predictive value (P = 0.041). The sensitivity of CMR for a 70% QCA stenosis was noninferior and nonsuperior to gated SPECT. CONCLUSIONS: Vasodilator stress perfusion CMR, as performed with gadobutrol 0.1 mmol/kg body weight, had superior diagnostic accuracy for diagnosis and exclusion of significant CAD vs gated SPECT.

Identifying Mitral Valve Prolapse at Risk for Arrhythmias and Fibrosis From Electrocardiograms Using Deep Learning.

BACKGROUND: Mitral valve prolapse (MVP) is a common valvulopathy, with a subset developing sudden cardiac death or cardiac arrest. Complex ventricular ectopy (ComVE) is a marker of arrhythmic risk associated with myocardial fibrosis and increased mortality in MVP. OBJECTIVES: The authors sought to evaluate whether electrocardiogram (ECG)-based machine learning can identify MVP at risk for ComVE, death and/or myocardial fibrosis on cardiac magnetic resonance (CMR) imaging. METHODS: A deep convolutional neural network (CNN) was trained to detect ComVE using 6,916 12-lead ECGs from 569 MVP patients from the University of California-San Francisco between 2012 and 2020. A separate CNN was trained to detect late gadolinium enhancement (LGE) using 1,369 ECGs from 87 MVP patients with contrast CMR. RESULTS: The prevalence of ComVE was 28% (160/569). The area under the receiver operating characteristic curve (AUC) of the CNN to detect ComVE was 0.80 (95% CI: 0.77-0.83) and remained high after excluding patients with moderate-severe mitral regurgitation [0.80 (95% CI: 0.77-0.83)] or bileaflet MVP [0.81 (95% CI: 0.76-0.85)]. AUC to detect all-cause mortality was 0.82 (95% CI: 0.77-0.87). ECG segments relevant to ComVE prediction were related to ventricular depolarization/repolarization (early-mid ST-segment and QRS from V1, V3, and III). LGE in the papillary muscles or basal inferolateral wall was present in 24% patients with available CMR; AUC for detection of LGE was 0.75 (95% CI: 0.68-0.82). CONCLUSIONS: CNN-analyzed 12-lead ECGs can detect MVP at risk for ventricular arrhythmias, death and/or fibrosis and can identify novel ECG correlates of arrhythmic risk. ECG-based CNNs may help select those MVP patients requiring closer follow-up and/or a CMR.

Diastology with Cardiac MRI: A Practical Guide.

Diastolic filling of the ventricle is a complex interplay of volume and pressure, contingent on active energy-dependent myocardial relaxation and myocardial stiffness. Abnormal diastolic function is the hallmark of the clinical entity of heart failure with preserved ejection fraction (HFpEF), which is now the dominant type of heart failure and is associated with significant morbidity and mortality. Although echocardiography is the current first-line imaging modality used in evaluation of diastolic function, cardiac MRI (CMR) is emerging as an important technique. The principal role of CMR is to categorize the cause of diastolic dysfunction (DD) and distinguish other entities that manifest similarly to HFpEF, particularly infiltrative and pericardial disorders. CMR also provides prognostic information and risk stratification based on late gadolinium enhancement and parametric mapping techniques. Advances in hardware, sequences, and postprocessing software now enable CMR to diagnose and grade DD accurately, a role traditionally assigned to echocardiography. Two-dimensional or four-dimensional velocity-encoded phase-contrast sequences can measure flow and velocities at the mitral inflow, mitral annulus, and pulmonary veins to provide diastolic functional metrics analogous to those at echocardiography. The commonly used cine steady-state free-precession sequence can provide clues to DD including left ventricular mass, left ventricular filling curves, and left atrial size and function. MR strain imaging provides information on myocardial mechanics that further aids in diagnosis and prognosis of diastolic function. Research sequences such as MR elastography and MR spectroscopy can help evaluate myocardial stiffness and metabolism, respectively, providing additional insights on diastolic function. The authors review the physiology of diastolic function, mechanics of diastolic heart failure, and CMR techniques in the evaluation of diastolic function. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Imaging for implementation of heart failure guidelines.

The classification of heart failure with implications for pharmacological therapeutic interventions rests on defining ejection fraction (EF) which is an imaging parameter. Imaging can provide diagnostic clues as to aetiology of heart failure; it can also guide and help assess response to treatment. Echocardiography, CMR, cardiac computed tomography, positron emission tomography, and Tc 99 m pyrophosphate scanning provide information about the aetiology of heart failure. Further, echocardiography plays the primary role in the evaluation of LV diastolic function and the estimation of left ventricular (LV) filling pressures both at rest and with exercise during diastolic stress testing. Heart failure guidelines recognize four stages (A, B, C, and D) for heart failure. Cardiac imaging along with risk factors and clinical status is needed for identifying these stages. There are joint societal echocardiographic guidelines by American Society of Echocardiography (ASE) of Echocardiography and European Association of Cardiovascular Imaging that are applicable to the imaging of heart failure patients. There are also separate guidelines for the evaluation of patients being considered for LV assist device implantation and for multimodality imaging of patients with heart failure and preserved EF. Cardiac catheterization is needed in patients whose haemodynamic status is uncertain after clinical and echocardiographic evaluation and to evaluate for coronary artery disease. Myocardial biopsy can identify the presence of myocarditis or specific infiltrative diseases when the findings by non-invasive imaging are not conclusive.

Sex differences in myocardial remodeling and extracellular volume in aortic regurgitation.

Whether sex differences exist in the cardiac remodeling related to aortic regurgitation (AR) is unclear. Cardiac magnetic resonance (CMR) is the current non-invasive reference standard for cardiac remodeling assessment and can evaluate tissue characteristics. This prospective cohort included patients with AR undergoing CMR between 2011 and 2020. We excluded patients with confounding causes of remodeling. We quantified left ventricular (LV) volume, mass, AR severity, replacement fibrosis by late Gadolinium enhancement (LGE), and extracellular expansion by extracellular volume fraction (ECV). We studied 280 patients (109 women), median age 59.5 (47.2, 68.6) years (P for age = 0.25 between sexes). Women had smaller absolute LV volume and mass than men across the spectrum of regurgitation volume (RVol) (P ≤ 0.01). In patients with ≥ moderate AR and with adjustment for body surface area, indexed LV end-diastolic volume and mass were not significantly different between sexes (all P > 0.5) but men had larger indexed LV end systolic volume and lower LV ejection fraction (P ≥ 0.01). Women were more likely to have NYHA class II or greater symptoms than men but underwent surgery at a similar rate. Prevalence and extent of LGE was not significantly different between sexes or across RVol. Increasing RVol was independently associated with increasing ECV in women, but not in men (adjusted P for interaction = 0.03). In conclusion, women had lower LV volumes and mass than men across AR severity  but their ECV increased with higher regurgitant volume, while ECV did not change in men. Indexing to body surface area did not fully correct for the cardiac remodeling differences between men and women. Women were more likely to have symptoms but underwent surgery at a similar rate to men. Further research is needed to determine if differences in ECV would translate to differences in the course of AR and outcomes.

Acute and Long-Term Scar Characterization of Venous Ethanol Ablation in the Left Ventricular Summit.

BACKGROUND: Venous ethanol ablation (VEA) can be effective for ventricular arrhythmias from the left ventricular summit (LVS); however, there are concerns about excessive ablation by VEA. OBJECTIVES: The purpose of this study was to delineate and quantify the location, extent, and evolution of ablated tissue after VEA as an intramural ablation technique in the LVS. METHODS: VEA was performed in 59 patients with LVS ventricular arrhythmias. Targeted intramural veins were selected by electrograms from a 2F octapolar catheter or by guide-wire unipolar signals. Median ethanol delivered was 4 mL (IQR: 4-7 mL). Ablated areas were estimated intraprocedurally as increased echogenicity on intracardiac echocardiography (ICE) and incorporated into 3-dimensional maps. In 44 patients, late gadolinium enhancement cardiac magnetic resonance (CMR) imaged VEA scar and its evolution. RESULTS: ICE-demonstrated increased intramural echogenicity (median volume of 2 mL; IQR: 1.7-4.3) at the targeted region of the 3-dimensional maps. Post-ethanol CMR showed intramural scar of 2.5 mL (IQR: 2.1-3.5 mL). Early (within 48 hours after VEA) CMR showed microvascular obstruction (MVO) in 30 of 31 patients. Follow-up CMR after a median of 51 (IQR: 41-170) days showed evolution of MVO to scar. ICE echogenicity and CMR scar volumes correlated with each other and with ethanol volume. Ventricular function and interventricular septum remained intact. CONCLUSIONS: VEA leads to intramural ablation that can be tracked intraprocedurally by ICE and creates regions of MVO that are chronically replaced by myocardial scar. VEA scar volume does not compromise septal integrity or ventricular function.

Role of Multimodality Imaging in Transcatheter Structural Interventions.

Cardiac imaging is the backbone for safe and optimal transcatheter structural interventions. Transthoracic echocardiogram is the initial modality to assess valvular disorders, while transesophageal echocardiogram is best to delineate the mechanism of valvular regurgitation, preprocedural assessment for transcatheter edge-to-edge repair, and for intraprocedural guidance. Cardiac computed tomography is the modality of choice for assessing calcifications, maneuvering multiplaner reconstruction of different cardiac structures, preprocedural planning for various transcatheter valve replacement, and assessing for hypoattenuated leaflet thickening and reduced leaflet motion. Cardiac magnetic resonance imaging is best known for most accurate volumetric assessment of valvular regurgitation and chamber size quantification. Cardiac positron emission tomography is the only modality that could assess active infection through using fluorine 18 fluorodeoxyglucose radiotracer.

Relation of Left Ventricular Diastolic Function to Global Fibrosis Burden: Implications for Heart Failure Risk Stratification.

BACKGROUND: Left ventricular (LV) diastolic function is primarily assessed by means of echocardiography, which has limited utility in detecting fibrosis. Cardiac magnetic resonance (CMR) readily detects and quantifies fibrosis. OBJECTIVES: In this study, the authors sought to determine the association of LV diastolic function by echocardiography with CMR-determined global fibrosis burden and the incremental value of fibrosis with diastolic function grade in prediction of total mortality and heart failure hospitalizations. METHODS: A total of 549 patients underwent comprehensive echocardiography and CMR within 30 days. Echocardiography was used to assess LV diastolic function, and CMR was used to determine LV volumes, mass, ejection fraction, replacement fibrosis, and percentage extracellular volume fraction (ECV). RESULTS: Normal diastolic function was present in 142 patients; the rest had diastolic dysfunction grades I to III, except for 18 (3.3%) with indeterminate results. The event rate was higher in patients with diastolic dysfunction compared with patients with normal diastolic function (33.4% vs 15.5; P < 0.001). The model including LV diastolic function grades II and III predicted composite outcome (C-statistic: 0.71; 95% CI: 0.67-0.76), which increased by adding global fibrosis burden (C-statistic: 0.74, 95% CI: 0.70-0.78; P = 0.02). For heart failure hospitalizations, the competing risk model with LV diastolic function grades II and III was good (C-statistic: 0.78; 95% CI: 0.74-0.83) and increased significantly with the addition of global fibrosis burden (C-statistic: 0.80; 95% CI: 0.76-0.85; P = 0.03). CONCLUSIONS: Higher grades of diastolic dysfunction are seen in patients with replacement fibrosis and increased ECV. Fibrosis burden as determined with the use of CMR provides incremental prognostic information to echocardiographic evaluation of LV diastolic function.

Influence of Cardiac Remodeling on Clinical Outcomes in Patients With Aortic Regurgitation.

BACKGROUND: Quantitative cardiac magnetic resonance (CMR) outcome studies in aortic regurgitation (AR) are few. It is unclear if volume measurements are beneficial over diameters. OBJECTIVES: This study sought to evaluate the association of CMR quantitative thresholds and outcomes in AR patients. METHODS: In a multicenter study, asymptomatic patients with moderate or severe AR on CMR with preserved left ventricular ejection fraction (LVEF) were evaluated. Primary outcome was development of symptoms or decrease in LVEF to <50%, development of guideline indications for surgery based on LV dimensions, or death under medical management. Secondary outcome was the same as the primary outcome, excluding surgery for remodeling indications. We excluded patients who underwent surgery within 30 days of CMR. Receiver-operating characteristic analyses for the association with outcomes were performed. RESULTS: We studied 458 patients (median age: 60 years; IQR: 46-70 years). During a median follow-up of 2.4 years (IQR: 0.9-5.3 years), 133 events occurred. Optimal thresholds were regurgitant volume of 47 mL and regurgitant fraction of 43%, indexed LV end-systolic (iLVES) volume of 43 mL/m2, indexed LV end-diastolic volume of 109 mL/m2, and iLVES diameter of 2 cm/m2. In multivariable regression analysis, iLVES volume of ≥43 mL/m2 (HR: 2.53; 95% CI: 1.75-3.66; P < 0.001) and indexed LV end-diastolic volume of ≥109 mL/m2 were independently associated with the outcomes and provided additional discrimination improvement over iLVES diameter, whereas iLVES diameter was independently associated with the primary outcome but not the secondary outcome. CONCLUSIONS: In asymptomatic AR patients with preserved LVEF, CMR findings can be used to guide management. CMR-based LVES volume assessment performed favorably compared to LV diameters.

Differences in Myocardial Remodeling and Tissue Characteristics in Chronic Isolated Aortic and Mitral Regurgitation.

BACKGROUND: The left ventricular hemodynamic load differs between aortic regurgitation (AR) and primary mitral regurgitation (MR). We used cardiac magnetic resonance to compare left ventricular remodeling patterns, systemic forward stroke volume, and tissue characteristics between patients with isolated AR and isolated MR. METHODS: We assessed remodeling parameters across the spectrum of regurgitant volume. Left ventricular volumes and mass were compared against normal values for age and sex. We calculated forward stroke volume (planimetered left ventricular stroke volume-regurgitant volume) and derived a cardiac magnetic resonance-based systemic cardiac index. We assessed symptom status according to remodeling patterns. We also evaluated the prevalence of myocardial scarring using late gadolinium enhancement imaging, and the extent of interstitial expansion via extracellular volume fraction. RESULTS: We studied 664 patients (240 AR, 424 primary MR), median age of 60.7 (49.5-69.9) years. AR led to more pronounced increases in ventricular volume and mass compared with MR across the spectrum of regurgitant volume (P<0.001). In ≥moderate regurgitation, AR patients had a higher prevalence of eccentric hypertrophy (58.3% versus 17.5% in MR; P<0.001), whereas MR patients had normal geometry (56.7%) followed by myocardial thinning with low mass/volume ratio (18.4%). The patterns of eccentric hypertrophy and myocardial thinning were more common in symptomatic AR and MR patients (P<0.001). Systemic cardiac index remained unchanged across the spectrum of AR, whereas it progressively declined with increasing MR volume. Patients with MR had a higher prevalence of myocardial scarring and higher extracellular volume with increasing regurgitant volume (P value for trend <0.001), whereas they were unchanged across the spectrum of AR (P=0.24 and 0.42, respectively). CONCLUSIONS: Cardiac magnetic resonance identified significant heterogeneity in remodeling patterns and tissue characteristics at matched degrees of AR and MR. Further research is needed to examine if these differences impact reverse remodeling and clinical outcomes after intervention.

Dynamic Imaging of Aortic Pathologies: Review of Clinical Applications and Imaging Protocols.

The past decade has seen significant advances in dynamic imaging of the aorta. Today's vascular surgeons have the opportunity to choose from a wide array of imaging modalities to evaluate different aortic pathologies. While vascular ultrasound and aortography are considered to be the bread and butter imaging modalities, newer dynamic imaging techniques provide time-resolved information in various aortic pathologies. However, despite growing evidence of their advantages in the literature, they have not been routinely adopted. In order to understand the role of these emerging modalities, one must understand their principles, advantages, and limitations in the context of various clinical scenarios. In this review, we provide an overview of dynamic imaging techniques for aortic pathologies and describe various dynamic computed tomography and magnetic resonance imaging protocols, clinical applications, and potential future directions.

Sex-Specific Stress Perfusion Cardiac Magnetic Resonance Imaging in Suspected Ischemic Heart Disease: Insights From SPINS Retrospective Registry.

BACKGROUND: Cardiovascular disease (CVD) remains the leading cause of mortality in women, but current noninvasive cardiac imaging techniques have sex-specific limitations. OBJECTIVES: In this study, the authors sought to investigate the effect of sex on the prognostic utility and downstream invasive revascularization and costs of stress perfusion cardiac magnetic resonance (CMR) for suspected CVD. METHODS: Sex-specific prognostic performance was evaluated in a 2,349-patient multicenter SPINS (Stress CMR Perfusion Imaging in the United States [SPINS] Study) Registry. The primary outcome measure was a composite of cardiovascular death and nonfatal myocardial infarction; secondary outcomes were hospitalization for unstable angina or heart failure, and late unplanned coronary artery bypass grafting. RESULTS: SPINS included 1,104 women (47% of cohort); women had higher prevalence of chest pain (62% vs 50%; P < 0.0001) but lower use of medical therapies. At the 5.4-year median follow-up, women with normal stress CMR had a low annualized rate of primary composite outcome similar to men (0.54%/y vs 0.75%/y, respectively; P = NS). In contrast, women with abnormal CMR were at higher risk for both primary (3.74%/y vs 0.54%/y; P < 0.0001) and secondary (9.8%/y vs 1.6%/y; P < 0.0001) outcomes compared with women with normal CMR. Abnormal stress CMR was an independent predictor for the primary (HR: 2.64 [95% CI: 1.20-5.90]; P = 0.02) and secondary (HR: 2.09 [95% CI: 1.43-3.08]; P < 0.0001) outcome measures. There was no effect modification for sex. Women had lower rates of invasive coronary angiography (3.6% vs 7.3%; P = 0.0001) and downstream costs ($114 vs $171; P = 0.001) at 90 days following CMR. There was no effect of sex on diagnostic image quality. CONCLUSIONS: Stress CMR demonstrated excellent prognostic performance with lower rates of invasive coronary angiography referral in women. Stress CMR should be considered as a first-line noninvasive imaging tool for the evaluation of women. (Stress CMR Perfusion Imaging in the United States [SPINS] Study [SPINS]; NCT03192891).

Myocardial Injury on CMR in Patients With COVID-19 and Suspected Cardiac Involvement.

BACKGROUND: Myocardial injury in patients with COVID-19 and suspected cardiac involvement is not well understood. OBJECTIVES: The purpose of this study was to characterize myocardial injury in a multicenter cohort of patients with COVID-19 and suspected cardiac involvement referred for cardiac magnetic resonance (CMR). METHODS: This retrospective study consisted of 1,047 patients from 18 international sites with polymerase chain reaction-confirmed COVID-19 infection who underwent CMR. Myocardial injury was characterized as acute myocarditis, nonacute/nonischemic, acute ischemic, and nonacute/ischemic patterns on CMR. RESULTS: In this cohort, 20.9% of patients had nonischemic injury patterns (acute myocarditis: 7.9%; nonacute/nonischemic: 13.0%), and 6.7% of patients had ischemic injury patterns (acute ischemic: 1.9%; nonacute/ischemic: 4.8%). In a univariate analysis, variables associated with acute myocarditis patterns included chest discomfort (OR: 2.00; 95% CI: 1.17-3.40, P = 0.01), abnormal electrocardiogram (ECG) (OR: 1.90; 95% CI: 1.12-3.23; P = 0.02), natriuretic peptide elevation (OR: 2.99; 95% CI: 1.60-5.58; P = 0.0006), and troponin elevation (OR: 4.21; 95% CI: 2.41-7.36; P < 0.0001). Variables associated with acute ischemic patterns included chest discomfort (OR: 3.14; 95% CI: 1.04-9.49; P = 0.04), abnormal ECG (OR: 4.06; 95% CI: 1.10-14.92; P = 0.04), known coronary disease (OR: 33.30; 95% CI: 4.04-274.53; P = 0.001), hospitalization (OR: 4.98; 95% CI: 1.55-16.05; P = 0.007), natriuretic peptide elevation (OR: 4.19; 95% CI: 1.30-13.51; P = 0.02), and troponin elevation (OR: 25.27; 95% CI: 5.55-115.03; P < 0.0001). In a multivariate analysis, troponin elevation was strongly associated with acute myocarditis patterns (OR: 4.98; 95% CI: 1.76-14.05; P = 0.003). CONCLUSIONS: In this multicenter study of patients with COVID-19 with clinical suspicion for cardiac involvement referred for CMR, nonischemic and ischemic patterns were frequent when cardiac symptoms, ECG abnormalities, and cardiac biomarker elevations were present.