The effect of nitroglycerin on myocardial blood flow in various segments characterized by rest-redistribution thallium SPECT.

The use of nitrates is reported to be effective in viability detection in scintigraphic perfusion imaging. The purpose of the study was to evaluate the effect of nitroglycerin (NTG) on myocardial blood flow (MBF) and coronary vascular resistance (CVR) in various segments characterized by rest-redistribution (201)Tl SPECT. METHODS: Twenty-three patients with coronary artery disease underwent rest-redistribution (201)Tl SPECT and (15)O-labeled water PET at rest and after NTG spray (0.3 mg). In addition, 11 healthy volunteers were also studied using PET. RESULTS: NTG did not change global MBF in the volunteers or in the patients. In segments with normal (201)Tl uptake and in those with a severe irreversible (201)Tl defect, NTG significantly reduced MBF without changing CVR. NTG reduced CVR in segments with a reversible (201)Tl defect (141 +/- 50 to 114 +/- 29 mm Hg/mL/min/g], P = 0.004) and in those with a mild-to-moderate irreversible (201)Tl defect (165 +/- 64 to 149 +/- 60 mm Hg/mL/min/g], P = 0.003), while maintaining MBF. CONCLUSION: NTG preferentially reduces CVR in the viable myocardium with ischemia. After NTG, tracer uptake in the ischemic myocardium will be relatively increased compared with that in the nonviable and nonischemic myocardium, leading to improvements in viability detection.