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Magnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome

Chang, Henry
http://rave.ohiolink.edu/etdc/view?acc_num=osu1429802520

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Biomedical Engineering.
An acute coronary syndrome (ACS) is a life-threatening event in the heart which affects over one million Americans each year. Although not currently part of the standard of care for ACS, magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques may be able to improve outcomes in patients with ACS. The majority of ACS cases are classified, using electrocardiogram (ECG), as non-ST segment acute coronary syndrome (NSTE-ACS). Diagnosis, risk assessment, and selection of management strategy can be difficult in this syndrome. A novel large animal model was created for study of NSTE-ACS by combining a partial coronary artery stenosis with ventricular pacing. In this animal model, MRI images of the heart were acquired, as well as oxygen respiration rates in myocardial tissue, troponin levels, and histology samples. T2 MRI, a technique which identifies myocardial regions with altered chemistry, was found to be elevated in ischemic myocardium. These T2 changes corresponded to reduced myocardial tissue respiratory function. Reperfusion reversed both T2 elevation and tissue respiratory depression, indicating that the early myocardial changes causing acute T2 elevation are reversible. This important property of T2 was supported by ultrastructural findings indicating myocardial viability and by the lack of late gadolinium enhancement (LGE) positivity or high troponins, which are tests to identify the presence of necrosed myocardium. An elevated T2 value thus may be a highly informative marker of acute reversible myocardial injury in NSTE-ACS and may reflect cellular changes (including respiratory function) which are not detectable by other tests or modalities yet have important implications on clinical decisions for patient management. Reversibly injured myocardium (identified by elevated T2) represents a target for reperfusion strategies that can prevent the progression to myocyte death and restore normal myocardial functionality. After an ACS, all patients are highly recommended to participate in a cardiac rehabilitation / secondary prevention (CR/SP) program, which has been shown to improve outcome metrics in patients such as mortality, quality of life, exercise capacity, and glucose control. However, some cellular properties like mitochondrial function and intramuscular fat, while important to patient health, are difficult to measure and so are not included as part of CR/SP evaluation of patients. Optimized techniques to non-invasively measure in vivo mitochondrial function, using 31P MRS, and intramuscular fat, using 1H MRS, were tested for reproducibility in volunteers. Once a suitable protocol was validated, measurements in ACS patients at the beginning of their CR/SP program were taken. This protocol was found to be reliably performed in a timely manner in any post-ACS patient who does not have MRI contraindications. Changes in mitochondrial function and intramuscular fat due to CR/SP interventions (such as modifications to exercise and diet habits) can be quantified using this protocol and used to evaluate the effectiveness of the CR/SP program. CR/SP supervisors thus may be able to tailor specific programs and activities to optimize the benefits to mitochondrial function and intramuscular fat and improve patient outcomes.
Subha Raman, MD (Advisor)
Orlando Simonetti, PhD (Committee Member)
Elliott Crouser, MD (Committee Member)
Stephen Lee, PhD (Committee Member)
213 p.
Biomedical Engineering; Biomedical Research; Medical Imaging; Medicine
acute coronary syndrome; magnetic resonance imaging; magnetic resonance spectroscopy; animal model; phosphocreatine; t2 mapping

Recommended Citations

Citations

  • Chang, H. (2015). Magnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429802520

    APA Style (7th edition)

  • Chang, Henry. Magnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1429802520.

    MLA Style (8th edition)

  • Chang, Henry. "Magnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429802520

    Chicago Manual of Style (17th edition)

osu1429802520
322
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This open access ETD is published by The Ohio State University and OhioLINK.