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. To date, we have focused on four specific aims. 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 was 96% and 95% respectively. An abnormal adenosine stress MRI had significant 1 year prognostic value. 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. This year we completed histopathological validation of the phase sensitive reconstruction method. This validation study further shows that a computer algorithm can accurately measure in vivo and ex vivo images of infarct size. 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. 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.