With the advent of coronary angiography a unique group of patients was identified with classic symptoms of angina, positive exercise tests, and normal epicardial coronary arteries. The majority of these patients demonstrate a reduced coronary flow reserve. With the development of intracoronary Doppler catheters, these patients with microvascular angina are becoming increasingly recognized. The identification of myocardial ischemia in these patients has potential importance for their management and long-term treatment but this requires adequate, preferably non-invasive, diagnostic tools for the routine clinical assessment. Novel magnetic resonance (MR) techniques for the quantification of myocardial blood flow and blood flow reserve, and MR 31P spectroscopy are proposed here to elucidate the effects of low flow reserve on transmural flow and myocardial metabolism in patients with microvascular angina. The MR methods for determination of myocardial blood flow are proposed here as an alternative to the """"""""gold standard"""""""" of quantitative PET imaging with the advantages of superior spatial and temporal resolution. It is hypothesized that the source of the flow limitation resides at the pre-arteriolar level, but the presence of myocardial ischemia is controversial. The MR first pass imaging technique combined with kinetic modeling for determination of absolute transmural blood flow and blood flow reserve offers unique advantages to elucidate the extent of the microvascular flow impairment and the presence and degree of ischemia, even if limited to the subendocardium.
