Coronary flow velocity response to intracoronary adenosine characterizes coronary microvascular function in women with chest pain in the absence of obstructive CAD. Attenuated epicardial coronary dilation response to adenosine may be a surrogate marker of microvascular dysfunction in women with chest pain and no obstructive CAD.

Objectives To assess the prognostic value of global magnetic resonance (MR) myocardial perfusion imaging (MPI) in women with suspected myocardial ischemia and no obstructive (stenosis <50%) coronary artery disease (CAD). Background The prognostic value of global MR-MPI in women without obstructive CAD remains unknown. Methods Women (n=100, mean age 57±11 years, range 31–76), with symptoms of myocardial ischemia and with no obstructive CAD as assessed by coronary angiography, underwent MR-MPI and standard functional assessment. During follow-up (34±16 months), time to first adverse event (death, myocardial infarction or hospitalization for worsening anginal symptoms) was analyzed using global MPI and left ventricular ejection fraction (EF) data. Results Adverse events occurred in 23 (23%). By univariable Cox proportional hazards regression modeling, variables found to be predictive of adverse events were global MR-MPI average uptake slope (p<0.05), the ratio of MR-MPI peak signal amplitude to uptake slope (p<0.05), and ejection fraction (EF) (p<0.05). Two multivariable Cox models were formed, one using variables that are performance-site dependent: ratio of MR-MPI peak amplitude to uptake slope together with EF (Chi-squared 13, p<0.005), and a model using variables that are performance-site independent: MR-MPI slope and EF (Chi-squared 12, p<0.005). Each of the two multivariable models remained predictive of adverse events after adjustment for age, disease history and Framingham risk score. For each of the Cox models, patients were categorized as high-risk if they were in the upper quartile of the model and not high-risk otherwise. Kaplan-Meier analysis of time to event was performed for high-risk vs. not high-risk for site-dependent (log rank 15.2, p<0.001) and site-independent (log rank 13.0, p<001) models. Conclusions Among women with suspected myocardial ischemia and no obstructive CAD, MR-MPI determined global measurements of normalized uptake slope and peak signal uptake, together with global functional assessment of EF appear to predict prognosis.

Myocardial flow reserve (MFR) is not routinely assessed in myocardial perfusion imaging (MPI) studies but has been hypothesized to affect test accuracy when assessing disease severity by coronary vessel lumenography. Magnetic resonance imaging (MRI) is an emerging diagnostic technique that can both perform MPI and assess MFR. We studied women (n = 184) enrolled in the Women's Ischemia Syndrome Evaluation (WISE) study with symptoms suggesting ischemic heart disease. Tests performed were coronary angiography and MPI by both MR and gated radionuclide single photon emission computed tomography (gated-SPECT). The MFR index was calculated using the MR data acquired at baseline and under vasodilation (dipyridamole) conditions. The study was structured with a pilot and an implementation phase. During the pilot phase (n = 46) data were unmasked and an MFR threshold was defined to divide patients into those with an adequate (AMFRI) or inadequate (IMFRI) MFR index. During the implementation phase, the MFR index threshold was prospectively applied to patients (n = 138). In the implementation phase, MPI ischemia detection accuracy compared to severe (> or = 70%) coronary artery diameter narrowing by angiography was higher in the AMFRI vs. the IMFRI group for MRI (86% vs. 70%, p < 0.05) and gated-SPECT (89% vs. 67%, p < 0.01). The IMFRI group (n = 55, 30% of study population) had a higher resting rate-pressure product compared with the AMFRI group (10,599 +/- 2871 vs. 9378 +/- 2447 bpm mm Hg, p < 0.01), consistent with higher resting myocardial flow. When compared with each other, MRI and gated-SPECT MPI showed no difference in accuracy among MFR groups. Myocardial perfusion patterns in the IMFRI group may have resulted in atypical perfusion patterns, which either masked or mimicked epicardial coronary artery disease.

Background-Acute brain embolization (ABE) in left-sided infective endocarditis has significant implications for clinical decision making. The true incidence of ABE, including subclinical brain embolization, is unknown. Methods and Results-We prospectively studied 56 patients with definite left-sided infective endocarditis. Patients were examined by a study neurologist, and those without contraindication had magnetic resonance imaging of the brain.Patients without clinical evidence of acute stroke but with magnetic resonance imaging evidence of ABE were considered to have subclinical brain embolization. Clinical stroke was present in 14 of 56 patients (25%). Among 40 patients undergoing magnetic resonance imaging, the incidence rates of subclinical brain embolization and any ABE were 48% and 80%, respectively. ABE was present in 18 of 19 patients (95%) with Staphylococcus aureus infection. At 3 months, mortality was similar among patients with clinical stroke and subclinical brain embolization (62% versus 53%; PϭNS) and was higher among patients with any ABE than among those without ABE (56% versus 12%; Pϭ0.046). Valvular surgery was performed in 25 patients (45%), including 16 with ABE, at a median of 4 days. No patient suffered a postoperative neurological complication. Surgery was independently associated with a lower risk of mortality at 3 months (odds ratio, 0.1; 95% confidence interval, 0.03 to 0.6; Pϭ0.008). Conclusions-Magnetic resonance imaging detected subclinical brain embolization in a substantial number of patients with left-sided infective endocarditis, suggesting that the incidence of ABE may be significantly higher than reports based on clinical and computed tomography findings have indicated. Brain magnetic resonance imaging may play a role in the complex decision about surgical intervention in infective endocarditis. (Circulation. 2009;120:585-591.)

I nvasive coronary angiography is the standard clinical means for depicting the coronary arteries and is the "gold standard" for diagnosing coronary artery disease (CAD). Since its implementation over 30 years ago, more than 2 million coronary angiograms have been made yearly in North America. Coronary angiography requires high-level technical expertise and technology, which makes it relatively expensive and limits it to a select population. Angiography also has its limitations, since only the lumen is displayed ("luminology") and the information it provides about the coronary plaque is not extensive. However, new tomographic methods for cardiovascular imaging such as intravascular ultrasonography (IVUS), coronary CT angiography and MRI can assess the atherosclerotic plaques responsible for early, "silent" CAD. In this article, we review the current and potential future clinical applications of these 3 tools for the visual detection of atherosclerotic CAD. Intravascular ultrasonographyIVUS has become a powerful complementary tool to measure and characterize coronary vessels and atherosclerotic plaques. An invasive procedure, IVUS produces images with a small ultrasound transducer mounted on a catheter similar to the standard catheters employed in coronary angioplasty. The catheter is advanced over the wire inside the coronary artery until it reaches a position distal to the segment to be studied. A series of tomographic images of the coronary artery are obtained as the catheter is slowly pulled back. Each IVUS image displays a 360°cross-sectional view of the layers of the coronary artery (intima, media and adventitia) as well as the lumen (Fig. 1A,B). Modern devices can perform 3-dimensional reconstructions online that provide information about the length, volume and reference landmarks of a plaque.Standard radiographic coronary angiography provides a single-plane "shadow" of the vascular lumen; its ability to accurately and reproducibly measure the degree of stenosis and to characterize plaque morphology is limited.1-3 Extensive experience in our and other centres has shown that IVUS is a safe, accurate and reproducible alternative method for assessing the severity and morphology of lesions.4,5 The types of plaques detectable by IVUS are summarized in Box 1. Clinical useThe best-studied clinical application of IVUS is in the placement of stents into coronary vessels (Fig. 1C,D, Fig. 2, Fig. 3). Stenting has revolutionized the treatment of atherosclerotic CAD. Restenosis inside the stent, which occurs in 5%-20% of cases (depending on the complexity of the lesion and underlying risk factors), nevertheless remains a major shortcoming. IVUS has played an important role in the understanding of stent failures.In-stent restenosis is typically caused by neointimal hyperplasia: new fibrotic tissue that grows inside the stent and obstructs the lumen. Serial IVUS studies performed in cases of bare-metal stent failure have shown that underexpansion of the stent is an important cause of early failure.6 If the stent is poorl...

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