Comparison of technetium 99m-tetrofosmin and thallium-201 single photon emission computed tomographic imaging for the assessment of viable myocardium in patients with left ventricular dysfunction.

BACKGROUND

Tetrofosmin is a new technetium 99m-labeled myocardial perfusion agent that has demonstrated favorable imaging characteristics in recent clinical trials. However, it is not certain whether 99mTc-tetrofosmin compared with thallium 201 would underestimate myocardial viability in regions with left ventricular dysfunction.

METHODS

To this end 15 patients (mean age 52+/-7 years) with coronary artery disease and left ventricular dysfunction (ejection fraction 35%+/-8%) documented on angiography underwent both quantitative rest-redistribution 201Tl and rest 99mTc-tetrofosmin single photon emission computed tomography imaging. RESULTS; Of 240 total segments on rest-redistribution 201Tl protocol 139 (58%) segments had irreversible 201Tl defects. Of these segments 79 (57%) had only mild to moderate reduction of 201Tl uptake (51% to 85% of normal uptake), whereas the remaining 60 (43%) had severely reduced tracer uptake (< or = 50% of normal uptake). On 99mTc-tetrofosmin protocol 180 (75%) segments had abnormal 99mTc-tetrofosmin uptake; of these segments 120 (67%) had mild to moderate reduction of 99mTc-tetrofosmin uptake, whereas 60 (33%) had severely reduced activity. Among hypokinetic regions concordance between 201Tl and 99mTc-tetrofosmin regarding myocardial viability with a cutoff point of 50% of peak activity was obtained in 28 (90%) of 31 segments (K' = 0.80), leaving only 3 of 31 regions discordant (p = NS). Similarly, among akinetic or dyskinetic regions concordance between the two tracers regarding myocardial viability was achieved in 54 (93%) regions (K' = 0.75), leaving only 4 of the 58 regions discordant (p = NS).

CONCLUSIONS

These data show that when the severity of uptake was considered within abnormal segments, a similar amount of 201Tl viable regions were observed by 99mTc-tetrofosmin. Thus these two agents may provide comparable information about myocardial viability when quantitative analysis of defect severity is performed.