Magnetic resonance coronary angiography.

Despite the availability of numerous noninvasive tests to identify those with inducible myocardial ischemia, 20% of conventional contrast angiograms demonstrate no significant coronary artery stenoses. Magnetic resonance (MR) imaging is ideally suited for evaluation of the heart, and has already been shown to be highly accurate for the depiction and assessment of cardiac chamber size, ventricular function, and valvular insufficiency. Using conventional spin-echo and gradient-echo techniques, investigators have previously been able to characterize coronary artery bypass grafts as "patent" or "occluded," but visualization of large segments of the native coronary vessels was unsuccessful due to artifacts related to cardiac and respiratory motion. Recently, several new "fast imaging" breath-hold techniques, including k-space segmentation and spiral imaging, have shown great promise for both visualizing the native coronary arteries, assessing vessel patency, and quantifying coronary blood flow. Echo planar MR coronary angiography also appears to be feasible. Further software and hardware improvements are needed, but MR may soon prove to be the premier cardiac imaging technique by providing a comprehensive cardiac evaluation for those with suspected coronary artery disease, including information previously unobtainable by any other noninvasive test.