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(Circulation. 1997;96:2932-2937.)
© 1997 American Heart Association, Inc.

Articles

Superiority of Nitrate-Enhanced ²⁰¹Tl Over Conventional Redistribution ²⁰¹Tl Imaging for Prognostic Evaluation After Myocardial Infarction and Thrombolysis

Sumit Basu, MBBS; Roxy Senior, MBBS, MD; Usha Raval; ; Avijit Lahiri, MBBS, MSc

From the Department of Cardiac Research, Northwick Park Hospital, and Institute for Medical Research, Harrow, Middlesex.

Correspondence to Dr A. Lahiri, MBBS, MSc, MRCP, FACC, FESC, Department of Cardiology, Northwick Park Hospital, Institute of Medical Research, Watford Rd, Harrow, Middlesex HA1 3 UJ, UK.

Background ²⁰¹Tl imaging has been widely used for postinfarction risk stratification. However, thrombolytic therapy and aspirin have significantly changed outcome, and there are few nuclear imaging studies that assess prognosis in such patients. Furthermore, newer techniques of ²⁰¹Tl imaging, such as reinjection and nitrate-enhanced rest ²⁰¹Tl imaging, have been shown to improve the detection of viable but jeopardized myocardium.

Methods and Results We studied 100 consecutive patients, who remained event free 6 weeks after myocardial infarction and thrombolysis. Patients underwent conventional exercise and 4-hour redistribution imaging, followed on a separate day by nitrate-enhanced rest ²⁰¹Tl study. Planar images were reported semiquantitatively by two experienced observers blinded to clinical data. Redistribution and rest injection images were classified as demonstrating reversible ischemia if they showed improvement in uptake by at least two grades in at least two segments in comparison with the initial exercise scintigram. Patients were followed up for 8 to 32 months (mean, 21 months); during this period, 37 patients had first cardiac events. Reversible ischemia was present in 29 patients on redistribution, of whom 14 (48%) had events; of 71 without reversible defects, 23 (32%) had events (hazard ratio, 1.5; 95% CI, 0.8 to 3.0; P=NS). Nitrate-enhanced rest ²⁰¹Tl imaging detected reversible defects in 68 patients, of whom 33 (49%) had events, whereas of 32 without reversible defects, only 4 (13%) had subsequent cardiac events (hazard ratio, 8.1; 95% CI, 2.7 to 23.8; P<.001).

Conclusions Thus, after myocardial infarction and thrombolysis, even "stable" patients have a high (68%) incidence of viable but jeopardized myocardium, causing a high event rate. Those identified to be at high risk by perfusion imaging may benefit from early intervention.

Key Words: myocardial infarction • radioisotopes • prognosis

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