Nitroglycerin-augmented ²⁰¹Tl reinjection enhances detection of reversible myocardial hypoperfusion: A randomized, double-blind, parallel, placebo-controlled trial

Background: Recent observations suggest that administration of nitrates before ²⁰¹Tl reinjection enhances the detection of reversible myocardial hypoperfusion. Methods and Results: Ninety-six patients who underwent exercise-redistribution ²⁰¹Tl single photon emission computed tomography (SPECT) and had persistent defects at 4-hour redistribution imaging were prospectively randomized into a double-blind protocol in which they received a reinjection of ²⁰¹Tl (1.0 mCi) 5 minutes after either placebo or 0.8 mg sublingual nitroglycerin administration, followed by repeat SPECT imaging. Of the 69 patients who had coronary angiography, all except one had significant coronary stenoses. The overall extent of perfusion defect and the reversible component assessed by polar maps of the stress-redistribution images were similar in patients who received nitroglycerin or placebo. Among the 66 patients with persistent defects in the redistribution images, 58% of those receiving nitroglycerin showed improved reversibility after reinjection, compared with 33% of patients receiving placebo (P<.05). Among 68 patients with significant coronary stenoses, those who received nitroglycerin and had coronary collateral circulation were more likely to exhibit improved reversibility after reinjection than the remaining patients (50% versus 21%, P<.05). Moreover, the ratio of reversible to total defect in the vascular territories supplied by collaterals was ≤0.50 after reinjection in 80% of patients who received nitroglycerin (n=20) compared with 40% of the patients who received placebo (n=15) (P<.05). Conclusions: Nitrate-augmented ²⁰¹Tl reinjection significantly, albeit modestly, improves detection of defect reversibility, especially in patients with coronary collateral circulation.