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Open Access Publications from the University of California

Scholarly Works (51 results)

  • Article
Cardiovascular Medicine (2021)
Myocardial strain imaging using 2D-speckle-tracking echocardiography (STE) is a relatively new method for analyzing myocardial function. Myocardial strain measures the shortening of myocytes in three directions: longitudinally, circumferentially, and radially. While ejection fraction (EF) is a common measure of heart health, strain measurements are more sensitive to changes in ventricular function and thus can be used to detect subclinical cardiac abnormalities that may not be seen by EF measurements. Strain values for various chambers have implications for identifying and treating many different cardiomyopathies. Speckle-tracking echocardiography and tissue Doppler imaging (TDI) are the two primary methods for measuring strain using echocardiography. STE is more clinically relevant than TDI due to its ability to distinguish passive tethering from active contractility and its independence of ultrasound beam angle. Reliability of strain measurements from STE is not universally agreed upon due to vendor differences in strain analysis algorithms. LV GLS tends to consistently have the greatest reliability and thus the most significant clinical application. LV GCS and GRS, LA GLS, RA GLS, and RV GLS have more mixed results and have not been implemented as widely as LV GLS.
    Cover page: Reliability of 2D-Speckle-Tracking for Myocardial Strain Measurements
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2021)
    Classification of heart failure is based on the left ventricular ejection fraction (EF): preserved EF, midrange EF, and reduced EF. There remains an unmet need for further heart failure phenotyping of ventricular structure-function relationships. Because of high spatiotemporal resolution, cardiac magnetic resonance (CMR) remains the reference modality for quantification of ventricular contractile function. The authors aim to highlight novel frameworks, including theranostic use of ferumoxytol, to enable more efficient evaluation of ventricular function in heart failure patients who are also frequently anemic, and to discuss emerging quantitative CMR approaches for evaluation of ventricular structure-function relationships in heart failure.
      Cover page: Cardiac Magnetic Resonance Quantification of Structure-Function Relationships in Heart Failure.
      • Thesis
      • Peer Reviewed
      UCLA Electronic Theses and Dissertations (2022)

      Cardiovascular disease remains the global leading cause of death. Noninvasive imaging techniques to detect and quantify myocardial ischemia continue to have wide-ranging impact in clinical cardiovascular care. This body of research aims to develop several novel noninvasive quantitative cardiac magnetic resonance imaging (MRI) techniques for the detection of ischemic heart disease. We designed, manufactured, and percutaneously deployed 3D printed implants in the left anterior descending (LAD) artery of 13 swine to investigate the feasibility and efficacy of the implants to cause hypoperfusion and ischemia on MRI. This novel animal model offers a success rate comparable to that of highly invasive methods, allowing for more rapid and cost-effective translational imaging studies. In a cohort of these swine models, we found that ferumoxytol improves the diagnostic performance of T1 reactivity as a measure of myocardial ischemia. Next, we aimed to use FE-MRI to capture a hemodynamic response to myocardial hypoperfusion at rest. We derived and tested a two-compartment water exchange model for quantification of fractional myocardial blood volume (fMBV) before developing an integrated image registration and compartmental modelling platform. We demonstrated the feasibility of a two-compartment model for estimation of fMBV using steady-state MOLLI T1 mapping over multiple ferumoxytol doses. Our technical developments to our image processing pipeline advance the current state of pixelwise fMBV mapping toward a more integrated in-line approach. We ultimately found that this fMBV mapping approach can be used to distinguish between ischemic and remote myocardium in a broader study in 19 ischemic swine models. Finally, our investigation of the in-vitro and in-vivo MRI properties of three comparable iron-based contrast agents contributes may help to expand the adoption of this unique class of contrast agents. In addition to our contributions to the development of two novel imaging biomarkers of heart disease, this body of research enables a broad range of new research in quantitative cardiovascular MRI.

        Cover page: Optimization and Validation of Ferumoxytol-Enhanced Myocardial T1 Reactivity and Myocardial Blood Volume Mapping for Detection of Myocardial Ischemia
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2016)

        There has been considerable improvement in cancer survival rates, primarily through improved preventive strategies and novel anticancer drugs. Cancer is now becoming a chronic illness and as such both short and long-term cardiotoxic effects of cancer therapy are becoming more apparent. This has led to the emergence of a new multidisciplinary specialty known as cardio-oncology, with the purpose of identifying patients who are at a higher risk for developing cardiotoxicity so that appropriate surveillance, treatment and follow-up strategies may be instituted early. The mechanisms of cardiotoxicity caused by commonly used anticancer agents are reviewed, along with the latest advances in diagnostic and preventative strategies, with the overall objective of allowing cancer patients to continue both lifesaving and palliative treatments for their malignancy.

          Cover page: Concepts in cardio-oncology: definitions, mechanisms, diagnosis and treatment strategies of cancer therapy-induced cardiotoxicity.
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2017)

          Purpose

          To develop and validate a cardiac-respiratory self-gating strategy for the recently proposed multiphase steady-state imaging with contrast enhancement (MUSIC) technique.

          Methods

          The proposed SG strategy uses the ROtating Cartesian K-space (ROCK) sampling, which allows for retrospective k-space binning based on motion surrogates derived from k-space center line. The k-space bins are reconstructed using a compressed sensing algorithm. Ten pediatric patients underwent cardiac MRI for clinical reasons. The original MUSIC and 2D-CINE images were acquired as a part of the clinical protocol, followed by the ROCK-MUSIC acquisition, all under steady-state intravascular distribution of ferumoxytol. Subjective scores and image sharpness were used to compare the images of ROCK-MUSIC and original MUSIC.

          Results

          All scans were completed successfully without complications. The ROCK-MUSIC acquisition took 5 ± 1 min, compared to 8 ± 2 min for the original MUSIC. Image scores of ROCK-MUSIC were significantly better than original MUSIC at the ventricular outflow tracts (3.9 ± 0.3 vs. 3.3 ± 0.6, P < 0.05). There was a strong trend toward superior image scores for ROCK-MUSIC in the other anatomic locations.

          Conclusion

          ROCK-MUSIC provided images of equal or superior image quality compared to original MUSIC, and this was achievable with 40% savings in scan time and without the need for physiologic signal. Magn Reson Med 78:472-483, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
            Cover page: Self‐gated 4D multiphase, steady‐state imaging with contrast enhancement (MUSIC) using rotating cartesian K‐space (ROCK): Validation in children with congenital heart disease
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2017)

            Purpose

            To compare the accuracy and precision of four different T1 estimation algorithms for modified Look-Locker inversion recovery (MOLLI).

            Methods

            Four T1 estimation algorithms, including the original fit, inversion group (IG) fit, instantaneous signal loss simulation (InSiL), and Bloch equation simulation with slice profile correction (BLESSPC) were studied. T1 estimation accuracy, precision, reproducibility, and sensitivity to heart rate (HR), flip angle (FA), and acquisition scheme (AcS) variations were compared in simulation, phantom, and volunteer studies.

            Results

            T1 estimation accuracy of IG (-2.4% ± 3.9%) and original fit (-3.2% ± 1.4%) were worse than BLESSPC (0.2% ± 1.5%) and InSiL (-0.7% ± 2.1%). The original fit had the best precision for T1 from 409-1884 ms for the same FA (0.67% ± 0.16% versus 0.90% ± 0.23% using IG, 0.78% ± 0.11% using InSiL, 0.77% ± 0.12% using BLESSPC). BLESSPC generated the most consistent in vivo T1 values over different FAs and AcS, and the T1 estimation reproducibility was similar (P > 0.3) among the four methods when FA = 35°. When using FA = 50°, the reproducibility was significantly improved only when using BLESSPC (1.6% ± 0.9 versus 2.6% ± 1.9%, P < 0.05).

            Conclusion

            BLESSPC has superior accuracy and is the least sensitive to FA, HR, and AcS variations. T1 estimation using BLESSPC and FA = 50° is superior to conventional MOLLI with FA = 35° in accuracy and precision. Further clinical studies in varying pathological conditions are warranted to confirm our findings. Magn Reson Med 78:1746-1756, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
              Cover page: Accuracy, precision, and reproducibility of myocardial T1 mapping: A comparison of four T1 estimation algorithms for modified look‐locker inversion recovery (MOLLI)
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2015)
              Cancer and cardiovascular disease (CVD) are two major causes of mortality in older adults. With improved survival and outcomes from cancer and CVD, the role of the geriatrician is evolving. Geriatricians provide key skills to facilitate patient-centered and value-based care in the growing older population of cancer patients (and survivors). Cancer treatment in older adults is particularly injurious with respect to complications stemming from cancer therapy and as well as to CVD related to cancer therapy in the context of physiologic aging. To best meet their natural potential as caregiving leaders, geriatricians must hone skills and insights pertaining to oncologic and cardiovascular care, insights that can inform and enhance key management expertise. In this paper, we will review common chemotherapy and radiation-induced cardiovascular complications, screening recommendations, and advance the concept of a geriatric, cardiology, and oncology collaboration. We assert that geriatricians are well suited to a leadership role in the care of older cardio-oncology patients and in the education of primary care physicians and subspecialists on geriatric principles.
                Cover page: The Crossroads of Geriatric Cardiology and Cardio-Oncology
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2022)
                Cardiac magnetic resonance imaging and angiography have a crucial role in the diagnostic evaluation and follow up of pediatric and adult patients with congenital heart disease. Although much of the information required of advanced imaging studies can be provided by standard gadolinium-enhanced magnetic resonance imaging, the limitations of precise bolus timing, long scan duration, complex imaging protocols, and the need to image small structures limit more widespread use of this modality. Recent experience with off-label diagnostic use of ferumoxytol has helped to mitigate some of these barriers. Approved by the U.S. FDA for intravenous treatment of anemia, ferumoxytol is an ultrasmall superparamagnetic iron oxide nanoparticle that has a long blood pool residence time and high relaxivity. Once metabolized by macrophages, the iron core is incorporated into the reticuloendothelial system. In this work, we aim to summarize the evolution of ferumoxytol-enhanced cardiovascular magnetic resonance imaging and angiography and highlight its many applications for congenital heart disease.
                  Cover page: Ferumoxytol-Enhanced Cardiac Magnetic Resonance Angiography and 4D Flow: Safety and Utility in Pediatric and Adult Congenital Heart DiseaseCreative Commons 'BY' version 4.0 license
                  • Article
                  • Peer Reviewed
                  UCLA Previously Published Works (2020)

                  Background

                  Cardiovascular electronic consultation is a new service line in consultative medicine and enables care without in-person office visits. We aimed to evaluate accessibility and time saved as measures of efficiency, determine the safety of cardiology electronic consultations, and assess satisfaction by responding cardiologists.

                  Methods

                  Using a mixed-methods approach and a modified time-driven, activity-based, costing framework, we retrospectively analysed cardiology electronic consultations. A random subset of 500 electronic consultations referred between 2013-2017 were reviewed. Accessibility was determined based upon increased number of patients served without the need for an in-person clinic visit. To assess safety, medical records were reviewed for emergency room visits or hospital admission at six months from the initial electronic consultation date. Responding cardiologist satisfaction was assessed by voluntary completion of an online survey.

                  Results

                  The majority of electronic consultations were related to medication advice, clearance for surgery, evaluation of images, or guidance after abnormal testing. Recommendations included echo (10.8%), stress testing (5.0%), other imaging (4.0%) and other subspecialist referrals (3.8%). Electronic consultations were completed within 0.7±0.5 days of the request, with a time to completion of 5-30 min. Over a six-month follow-up, 13.9% of patients had an in-person visit and 2.2% of patients were hospitalised, but none were directly related to the electronic consultation question. Satisfaction by responding cardiologists was modest.

                  Conclusion

                  In conclusion, within a single-payer system, cardiology electronic consultations represent a convenient and safe alternative for providing consultative cardiovascular care, but further optimization is necessary to minimise electronic consultation fatigue experienced by cardiologists.
                    Cover page: Cardiology electronic consultations: Efficient and safe, but consultant satisfaction is equivocal.
                    • Article
                    • Peer Reviewed
                    UCLA Previously Published Works (2020)
                    Diagnostic imaging technology in vascular disease has long focused on large vessels and the pathologic processes that impact them. With improved diagnostic techniques, investigators are now able to uncover many underlying mechanisms and prognostic factors for microvascular disease. In the heart and brain, these pathologic entities include coronary microvascular disease and cerebral small vessel disease, both of which have significant impact on patients, causing angina, myocardial infarction, heart failure, stroke, and dementia. In the current paper, we will discuss parallels in pathophysiology, classification, and diagnostic modalities, with a focus on the role of magnetic resonance imaging in microvascular disease of the heart and brain. Novel approaches for streamlined imaging of the cardiac and central nervous systems including the use of intravascular contrast agents such as ferumoxytol are presented, and unmet research gaps in diagnostics are summarized.
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