Can we enhance the detection of ischemia and better identify high risk coronary artery disease by imaging of myocardial metabolism?

Excerpt

For more than 30 years, the main noninvasive nuclear approach to detecting coronary artery disease (CAD) has been with stress and rest (or redistribution for thallium-201) myocardial perfusion imaging. This technology has served us well since CAD was detected with a higher sensitivity and specificity than achieved with exercise ECG stress testing alone. It also permitted stratification of risk for prognosis with the demonstration that patients with normal perfusion at peak stress had a <1% annual rate of death or infarction and patients with abnormal scans had event rates in proportion to the extent and severity of ischemia and scar. Nevertheless, there are significant limitations to the accurate detection of the extent of anatomic CAD and percent of the left ventricle at risk for ischemia employing stress perfusion imaging where just relative differences in blood flow at peak stress are evaluated. The quantitation of absolute flow in mL/minute/gram or coronary flow reserve by positron emission tomographic (PET) techniques can be accomplished using dynamic PET where tissue and blood time activity curves corrected for physical decay, partial volume effect and activity spillover from the blood pool to the myocardium are undertaken.1 Determining absolute blood flow or the difference between regional myocardial activity measured at rest and peak vasodilator stress by PET using either Rb-82, oxygen-15 water or N-13 ammonia can better identify extent of CAD in patients compared to the conventional methodology of assessing relative differences in regional counts where 3-vessel disease and left main CAD are underestimated. …