Elsevier

Journal of Nuclear Cardiology

Volume 11, Issue 6, November–December 2004, Pages 664-672
Journal of Nuclear Cardiology

Original articles
Comparison between Tc-99m N-NOET and Tl-201 in the assessment of patients with known or suspected coronary artery disease

https://doi.org/10.1016/j.nuclcard.2004.05.010Get rights and content

Background

Technetium 99m N-ethoxy-N-ethyl dithiocarbamate (N-NOET) is a new radionuclide tracer for cardiac single photon emission computed tomography (SPECT) imaging. It combines the advantageous properties of a Tc-99m agent with the redistribution characteristics of thallium 201. We directly compared the two agents in patients with known or suspected coronary artery disease.

Methods and results

Fifty patients underwent treadmill exercise Tc-99m N-NOET and Tl-201 SPECT studies. Images were acquired at stress, redistribution, and reinjection. Segmental analysis was carried out, and direct comparisons were made with corresponding segments. A stress score index was calculated and compared with the degree of lung uptake for each patient. From the 50 patients, 2657 of 2664 exercise, redistribution, and reinjection segments (99%) were interpreted. There was excellent agreement between the two modalities (weighted κ = 0.83). Of the patients, 24 demonstrated reversible ischemia by Tl-201 SPECT reinjection imaging, of which Tc-99m N-NOET stress-redistribution imaging correctly identified 14 (58%); this improved significantly to 20 patients (83%) (P = .03) when a reinjection protocol was used. A higher stress score index was seen in those patients with significant lung uptake (lung-heart ratio ≥0.6) after Tc-99m N-NOET stress imaging (1.6 vs 1.3, P = .03).

Conclusion

SPECT imaging with Tc-99m N-NOET is comparable to Tl-201 for the diagnosis of coronary artery disease. Significant lung uptake with stress Tc-99m N-NOET may also indicate the severity of disease.

Section snippets

Patient selection

Patients with known or suspected CAD scheduled for coronary angiography were prospectively studied as part of a European multicenter study. Myocardial infarction in the preceding 8 weeks, percutaneous coronary intervention in the preceding 3 months, or coronary artery bypass surgery in the preceding 6 months were exclusion criteria. In addition, pregnant or lactating women, as well as any patient with standard contraindications to exercise testing (unstable angina, severe aortic stenosis,

Results

Of the 58 patients who participated in the United Kingdom arm of the study, 50 underwent both Tl-201 and Tc-99m N-NOET exercise-redistribution and reinjection studies. Baseline characteristics are shown in Table 1. The majority of patients (84%) were taking aspirin at baseline, together with 58% taking β-blockers and 26% taking rate-limiting calcium antagonists. This reflected the high prevalence of CAD in our study population. Of the patients, 48 (96%) underwent Tl-201 SPECT imaging followed

Discussion

Tc-99m N-NOET is a new neutral, lipophilic, technetium-based complex that demonstrates high myocardial uptake in animal models.13 In canine models myocardial regional distribution with Tc-99m N-NOET has correlated well with regional blood flow (when assessed with microspheres) over a large range of coronary flows.9 Unlike other technetium-based agents, it does not plateau at higher coronary flows and hence behaves much more like Tl-201. Other characteristics such as a high first-pass extraction

Acknowledgment

We thank CIS-Bio International (Schering, Gif-sur-Yvette, France) for providing the Tc-99m N-NOET used in this study as well as for their ongoing help and support.

The authors have indicated they have no financial conflicts of interest.

References (21)

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