VIABILITY AFTER MYOCARDIAL-INFARCTION - CAN IT BE ASSESSED WITHIN 5 MINUTES BY LOW-DOSE DYNAMIC IODINE-123-IODOPHENYLPENTADECANOIC ACID IMAGING WITH A MULTICRYSTAL GAMMA-CAMERA

Although positron emission tomography (PET) assesses myocardial viabil ity (V) accurately, a rapid, inexpensive substitute is needed. Therefo re, the authors developed a low-dose (1 mCi) Iodine-123-Iodophenylpent adecanoic Acid (IPPA) myocardial viability scan requiring analysis of only the first three minutes of data acquired at rest with a standard multicrystal gamma camera. Twenty-one patients > 2 weeks after myocard ial infarction (MI) (24 MIs, 10 anterior, 14 inferoposterior, 21 akine tic or dyskinetic) had cardiac catheterization and resting IPPA imagin g. V was determined by either transmural myocardial biopsy during coro nary bypass surgery (12 patients, 14 MIs) or reinjection tomographic t hallium scan (9 patients, 10 MIs), and 50% of Evils were viable. The I PPA variables analyzed were: time to initial left ventricular (LV) upt ake in the region of interest (ROI), the ratio of three-minute uptake in the ROI to three-minute LV uptake, three-minute clearing (counts/pi xel) in the ROI (decrease in IPPA after initial uptake), and three-min ute accumulation (increase in IPPA after initial uptake) in the ROI. R ules for detecting V were generated and applied to 10 healthy voluntee rs to determine normalcy. While three-minute uptake in nonviable MIs w as only 67% of volunteers (P < 0.0001) and 75% of viable MIs, uptake a lone identified only 50% of viable MIs and 75% of nonviable MIs. IPPA clearing, however, was greater than or equal to 13.5 counts/pixel in 1 0/12 (83%) of viable MIs, and IPPA accumulation greater than or equal to 6.75 counts/pixel identified one more viable MI, for a sensitivity for V of 11/12 (92%), with a specificity of 11/12 (92%), and a 100% no rmalcy rate. The authors conclude low-dose IPPA (five-minute acquisiti on with analysis of the first three minutes of data) has potential for providing rapid, inexpensive V data after MI. Since newer multicrysta l cameras are mobile, IPPA scans can be done in emergency rooms or cor onary care units, generating information that might be useful in decis ions regarding thrombolysis, angioplasty, or bypass surgery.