MRI Evaluation Of Acute Cardiovascular Disease

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The major aim of the National Heart, Lung and Blood Institute (NHLBI)/Suburban Hospital Cardiovascular MRI Research Project is to develop new approaches in assessing patients with cardiovascular disease with MRI technology. 1) Detection of acute coronary syndrome with MRI. Earlier this year, we published that a rest MRI scan had higher sensitivity and specificity for diagnosing non-ST elevation acute coronary syndrome than cardiac risk factors, ECG, and troponin. The sensitivity and specificity for detecting acute coronary syndrome was 84% and 85% by MRI, 80% and 61% by an abnormal ECG, 16% and 95% for ST depression or T-wave inversion, 40% and 97% for peak troponin-I, and 48% and 85% for a TIMI risk score >3. The MRI was more sensitive than strict ECG criteria for ischemia (p<0.001), peak troponin-I (p<0.001), and the TIMI Risk Score (p=0.004). The MRI was more specific than an abnormal ECG (p<0.001). Multivariate logistic regression analysis showed an abnormal MRI was the strongest predictor of acute coronary syndrome and added statistically significant diagnostic value over clinical parameters (p<0.001). We concluded that the resting MRI scan exhibited diagnostic operating characteristics suitable for triage of patients with chest pain in the emergency department. We have extended this work in a second protocol that used adenosine stress MRI to evaluate 141 consecutive patients with troponin-negative acute coronary syndrome. The overall sensitivity and specificity for detecting ischemic heart disease were both greater than 90%. An abnormal adenosine stress MRI had significant 1 year prognostic value. We have determined that gadolinium delayed enhancement cardiovascular magnetic resonance corrrelates with clinical measures of myocardial infarction. This study imaged patients with acute myocardial infarction an average of 2 days post-MI. The transmural extent of delayed enhancement predicted the recovery of regional myocardial function. We have started a project that aims to characterize recently ischemic myocardium and demonstrated that we can image the ischemic area at risk after myocardial perfusion has been restored. This can be described as a form of "ischemic memory imaging." 2) Characterizing myocardial viability with MRI. We also developed a phase sensitive reconstruction method which improves the quality of heart attack images and minimizes the influence of user selected parameters on the apparent size of the heart attack. Our histopathological validation of the phase sensitive reconstruction method and a validation study showing that a computer algorithm can accurately measure infarct size on in vivo and ex vivo images is now in press. We have also extended this work to characterize IL-2 myocarditis and community acquired myocarditis. We have extended our validations of the phase sensitive inverson recovery methods for imaging myocardial infarction with another study: Artifact suppression in imaging of myocardial infarction using B1-weighted phased-array combined phase-sensitive inversion recovery. 3) First pass myocardial perfusion imaging. We have extended our first pass perfusion methods to provide quantitative analysis methods. We have shown that the MRI can measure myocardial perfusion as accurately as microsphere injections (a gold standard method only usable in animal models). We are in the process of translating these methods to analyze human dipyridamole stress tests and have corroborated the basic findings from the Christian manuscript apply to humans. 4) MRI characterization of atherosclerotic plaque. We have extended our prior observations that gadolinium nearly doubles the ability to discriminate different portions of the atherosclerotic plaque. We have studied the kinetics with which contrast enters the fibrous cap and lipid core of carotid atheroma]. 5) We have reduced image artifacts on DENSE images, a method for imaging myocardial strain. This year, we demonstrated that parallel image processing can accelerate the rate of acquiring phase contrast methodologies.