Cardiac Imaging Modalities and Appropriate Use

Cardiac MRI: An Overview of Physical Principles With Highlights of Clinical Applications and Technological Advancements

The purpose of this review is to serve as a concise learning tool for clinicians interested in quickly learning more about cardiac magnetic resonance imaging (CMR) and its physical principles. There is heavy coverage of the basic physical fundamentals of CMR as well as updates on the history, clinical indications, cost-effectiveness, role of artificial intelligence in CMR, and examples of common late gadolinium enhancement (LGE) patterns. This literature review was performed by searching the PubMed database for the most up-to-date literature regarding these topics. Relevant, less up-to-date articles, covering the history and physics of CMR, were also obtained from the PubMed database. Clinical indications for CMR include adult congenital heart disease, cardiac ischemia, cardiomyopathies, and heart failure. CMR has a projected cost-benefit ratio of 0.58, leading to potential savings for patients. Despite its utility, CMR has some drawbacks including long image processing times, large space requirements for equipment, and patient discomfort during imaging. Artificial intelligence-based algorithms can address some of these drawbacks by decreasing image processing times and may have reliable diagnostic capabilities. CMR is quickly rising as a high-resolution, non-invasive cardiac imaging modality with an increasing number of clinical indications. Thanks to technological advancements, especially in artificial intelligence, the benefits of CMR often outweigh its drawbacks.

A Doppler-exclusive non-invasive computational diagnostic framework for personalized transcatheter aortic valve replacement

Given the associated risks with transcatheter aortic valve replacement (TAVR), it is crucial to determine how the implant will affect the valve dynamics and cardiac function, and if TAVR will improve or worsen the outcome of the patient. Effective treatment strategies, indeed, rely heavily on the complete understanding of the valve dynamics. We developed an innovative Doppler-exclusive non-invasive computational framework that can function as a diagnostic tool to assess valve dynamics in patients with aortic stenosis in both pre- and post-TAVR status. Clinical Doppler pressure was reduced by TAVR (52.2 ± 20.4 vs. 17.3 ± 13.8 [mmHg], p < 0.001), but it was not always accompanied by improvements in valve dynamics and left ventricle (LV) hemodynamics metrics. TAVR had no effect on LV workload in 4 patients, and LV workload post-TAVR significantly rose in 4 other patients. Despite the group level improvements in maximum LV pressure (166.4 ± 32.2 vs 131.4 ± 16.9 [mmHg], p < 0.05), only 5 of the 12 patients (41%) had a decrease in LV pressure. Moreover, TAVR did not always improve valve dynamics. TAVR did not necessarily result in a decrease (in 9 out of 12 patients investigated in this study) in major principal stress on the aortic valve leaflets which is one of the main contributors in valve degeneration and, consequently, failure of heart valves. Diastolic stresses increased significantly post-TAVR (34%, 109% and 81%, p < 0.001) for each left, right and non-coronary leaflets respectively. Moreover, we quantified the stiffness and material properties of aortic valve leaflets which correspond with the reduced calcified region average stiffness among leaflets (66%, 74% and 62%; p < 0.001; N = 12). Valve dynamics post-intervention should be quantified and monitored to ensure the improvement of patient conditions and prevent any further complications. Improper evaluation of biomechanical valve features pre-intervention as well as post-intervention may result in harmful effects post-TAVR in patients including paravalvular leaks, valve degeneration, failure of TAVR and heart failure.

An ultrasound-exclusive non-invasive computational diagnostic framework for personalized cardiology of aortic valve stenosis

Aortic stenosis (AS) is an acute and chronic cardiovascular disease and If left untreated, 50% of these patients will die within two years of developing symptoms. AS is characterized as the stiffening of the aortic valve leaflets which restricts their motion and prevents the proper opening under transvalvular pressure. Assessments of the valve dynamics, if available, would provide valuable information about the patient's state of cardiac deterioration as well as heart recovery and can have incredible impacts on patient care, planning interventions and making critical clinical decisions with life-threatening risks. Despite remarkable advancements in medical imaging, there are no clinical tools available to quantify valve dynamics invasively or noninvasively. In this study, we developed a highly innovative ultrasound-based non-invasive computational framework that can function as a diagnostic tool to assess valve dynamics (e.g. transient 3-D distribution of stress and displacement, 3-D deformed shape of leaflets, geometric orifice area and angular positions of leaflets) for patients with AS at no risk to the patients. Such a diagnostic tool considers the local valve dynamics and the global circulatory system to provide a platform for testing the intervention scenarios and evaluating their effects. We used clinical data of 12 patients with AS not only to validate the proposed framework but also to demonstrate its diagnostic abilities by providing novel analyses and interpretations of clinical data in both pre and post intervention states. We used transthoracic echocardiogram (TTE) data for the developments and transesophageal echocardiography (TEE) data for validation.

The value of cardiac CT in the diagnosis of unroofed coronary sinus syndrome

BACKGROUND

Unroofed coronary sinus syndrome (UCSS) is a rare cardiovascular malformation with nonspecific clinical manifestations that easily causes misdiagnosis and missed diagnosis. The aim of this study is to present the different features of UCSS by various CCT (cardiac CT) postprocessing techniques and evaluate the diagnostic advantages of CCT.

METHODS

9 UCSS patients who were diagnosed by imaging and undergone both CCT and transthoracic echocardiography (TTE) were included in this study, and their CCT images were reviewed. The UCSS images were classified by multiplanar reformations, maximum intensity projection, volume rendering and cinematic rendering. The size of CS roof defect was also measured.

RESULTS

Only 4 of 9 CCT confirmed UCSS patients were detected by TTE (4/9, 44.4%), the sensitivity of TTE was lower compared to CCT by Fisher's exact test (P < 0.05). UCSS was classified according to the Kirklin and Barratt Boyes's method, including 1 case was classified as type I, 4 cases as type II, 1 case as type III, 2 cases as type IV, 1 case as type V (variant type), and TTE was undiagnosed in all type III-V patients. Additionally, CCT showed 12 extra malformations in these patients, only 5 of them were found by TTE (5/12, 41.7%), and TTE missed all extracardiac malformations. The mean size of CS roof defect was 3.04 ± 1.57 cm.

CONCLUSIONS

CCT with various postprocessing technologies has excellent value in diagnosing and differentiating subtypes of UCSS, measuring size of coronary sinus defect, describing accompanying cardiovascular abnormalities.

A case report of right atrial epithelioid hemangioendothelioma with multiple pulmonary metastases

Cardiac epithelioid hemangioendothelioma (EHE) is a very rare tumour of endothelial origin with the lung and liver as the most easily metastatic organs. We describe herein a patient with hemoptysis, severe anaemia, and diffuse pulmonary nodules with halo signs that represented metastasis of cardiac EHE; these radiologic manifestations are relatively uncommon. During the initial workup for the patient's pulmonary nodules, echocardiography missed the cardiac mass. However, positron emission tomography-computed tomography revealed increased fluorodeoxyglucose intake in the right atrial wall, and cardiac magnetic resonance imaging (MRI) revealed an irregular nodule with normal T1-weighted signal intensity and hyperintense T2-weighted signal intensity. Enhanced abdominal computed tomography (CT) revealed micronodular liver metastases. Video-assisted thoracic surgery was performed to make a definitive diagnosis. Immunohistochemistry staining proved the diagnosis of EHE with positive results for cluster of differentiation (CD) 34, CD31, erythroblast transformation-specific-related gene and Ki-67. The patient started chemotherapy with docetaxel (75 mg/m² ) and gemcitabine (900 mg/m² ), but this failed to control his disease and he died from an opportunistic infection related to his immunocompromised status 5 months later. For the work out process of bilateral diffuse pulmonary nodules suspicious for cardiac origin, especially with atrial deviation, echocardiography alone is not sufficient to exclude atrial origin. Cardiac CT or MRI might be a better choice.