EFFECTS OF NITROGLYCERIN BY TC-99M SESTAMIBI TOMOSCINTIGRAPHY ON RESTING REGIONAL MYOCARDIAL HYPOPERFUSION IN STABLE PATIENTS WITH HEALED MYOCARDIAL-INFARCTION

Myocardial sestamibi uptake reflects regional now distribution and cel lular integrity; however, some segments showing reduced tracer uptake at rest may consist of viable, although hypoperfused, myocardium. It i s speculated that the administration of nitroglycerin (NTG) before the sestamibi injection would improve the tracer uptake in resting hypope rfused regions. Thirty-six stable patients with previous myocardial in farction (56 +/- 2 years; mean ejection fraction 42 +/- 2%), in whom p erfusion defects could be seen at resting sestamibi tomography, repeat ed the scintigraphic study 2 to 6 days later, receiving NTG (0.3 to 0. 6 mg sublingually) before the tracer injection. The size of the tracer uptake defect was quantified from circumferential profiles in 3 short -axis slices by integrating the area below the lower normal limit (mea n - 2 SD). After NTG, the mean perfusion defect significantly decrease d (from 6,324 +/- 619 to 5,365 +/- 516, p <0.01). The defect was reduc ed beyond the reproducibility limits in 20 patients (56%, group 1) and was unchanged or increased in 16 (44%, group 2). The resting sestamib i defect size was comparable between the 2 groups. The average percent reduction of the perfusion defect after NTG was 29 +/- 4% (range 7 to 74). The perfusion defects that improved after NTG were associated wi th a less severe a-dimensional echocardio-graphic regional wall motion score (2.1 +/- 0.1 vs 2.8 +/- 0.1 in segments showing fixed defect, p <0.001), a lower rate of patency (37% vs 83%, p <0.05), and a worse g rade of the sestamibi defect-related vessel flow according to the Thro mbolysis in Myocardial Infarction trial (1.2 +/- 0.3 vs 2.4 +/- 0.3, p <0.05). After NTG, changes in regional myocardial now distribution ma y occur in a sizable number of stable patients with healed myocardial infarction, as reflected by their improved sestamibi uptake in areas s howing resting perfusion defects in the absence of symptoms of myocard ial ischemia.