Variation in quantitative myocardial perfusion due to arterial input selection.

OBJECTIVES This study compared the clinical implications of quantifying myocardial perfusion among different potential arterial input sites: the high (HAo) and basal (BAo) ascending aorta, descending aorta (DA), left atrium (LA), and left ventricular (LV) cavity. BACKGROUND Absolute myocardial perfusion and its hyperemic reserve imaged by positron emission tomography (PET) can serve as noninvasive functional measures of physiologic severity. Quantitative myocardial perfusion by PET depends on the time-concentration of vascular activity, called arterial input (AI). However, arterial activity imaged by PET can vary among sites due to partial volume effects from anatomic size, cardiac or respiratory motion out of fixed regions of interest, and spillover from neighboring vascular structures. METHODS Patients underwent cardiac rubidium-82 PET imaging with flow quantification using various anatomic AI. After excluding sites with overt spillover or misregistration, we selected the customized, highest AI among the BAo, HAo, DA, and LA. Average whole heart flows and percent of LV with substantial definite ischemia were compared among sites. RESULTS Of 288 cases, LA was selected in roughly half, with HAo in another quarter to one-third. Compared with using the customized AI, rest and stress absolute flow were higher by 5% to 10% for HAo, 14% for BAo, 19% to 23% for DA, and 46% to 49% for LV due to artifactually low AI values. The ratio of coronary flow reserve to its customized value was less affected, although its 95% confidence interval increased among AI locations: 7% for LA, 16% for HAo, 20% for BAo, 28% for DA, and 31% for LV. CONCLUSIONS The best customized site for AI activity varies for each patient among potential anatomic locations. Selection of the customized arterial site for each individual improved quantification of myocardial perfusion and coronary flow reserve with less variability compared with utilizing a single, pre-selected, fixed anatomic site.