Click on image to view larger version.
FIGURE 6. Polar map of myocardial tracer uptake during adenosine vasodilation is shown in a patient with CAD. (A) Relative distribution of the radiotracer (as would be the case with SPECT studies) suggests single-vessel disease in the territory of left anterior descending (LAD) artery. (B) Quantitative assessment of regional myocardial blood flow reserve with 13N-ammonia PET. In a vascular territory without significant coronary artery stenosis, a normal myocardial blood flow reserve is approximately 3 mL/min/g. As such, quantitative myocardial blood flow assessment identifies abnormal flow reserve in all 3 vascular territories in this patient; 1.37 mL/min/g in LAD territory, 1.65 mL/min/g in left circumflex (LCX) territory, and 1.91 mL/min/g in right coronary artery (RCA) territory. The clinical implication for the presumed diagnosis of 1-vessel disease on evaluation of relative myocardial radiotracer uptake versus 3-vessel CAD on quantitative assessment of myocardial blood flow reserve is important and not inconsequential. Moreover, follow-up polar maps (C and D) acquired 1-y after medical therapy with pravastatin show significant improvement in myocardial flow reserve in all 3 vascular territories when compared with baseline values (A and B). The extent of the stress-induced defect decreased from 51% of LAD vascular territory to only 3%. Moreover, there is increase and normalization in myocardial blood flow reserve in LCX and RCA vascular territories, which could be detected only on quantitative measurements of myocardial blood flow (D) but not on evaluation of the relative radiotracer uptake (C). (Adapted from (65).)
