Baseline/postnitrate tetrofosmin SPECT for myocardial viability assessment in patients with postischemic severe left ventricular dysfunction: new evidence from MRI.
The aim of this study was to compare (99m)Tc-tetrofosmin SPECT with contrast-enhanced MRI (ceMRI), a new direct sign of myocardial fibrosis.


METHODS
We studied 21 patients (age, 60 +/- 11 y; 19 male) with previous myocardial infarction and severe left ventricular dysfunction (ceMRI EF, 29% +/- 6%). All patients underwent resting and postnitrate (intravenous isosorbide dinitrate) (99m)Tc-tetrofosmin gated SPECT as well as ceMRI. Scintigraphic analysis was performed using quantitative perfusion SPECT (QPS), providing the percentage radiotracer uptake and defect severity in a 20-segment model. Hyperenhancement was defined by the increase of ceMRI signal intensity 20 min after intravenous injection of gadolinium-diethylenetriaminepentaacetic acid and its regional extension as the percentage of the total segment area.


RESULTS
In ceMRI dysfunctional segments, the correlation between the extent of hyperenhancement and both (99m)Tc-tetrofosmin uptake and defect severity was significantly better after nitrate administration rather than at rest (P < 0.0001). Using a ceMRI cutoff below 40%, 102 of 196 (52%) segments were viable, whereas 94 (48%) segments were not viable. According to receiver-operating characteristic curve analysis, diagnostic accuracies were higher for postnitrate (99m)Tc-tetrofosmin uptake as well as perfusion defect severity than using resting data (0.84 vs. 0.71, P < 0.001; 0.89 vs. 0.76, P < 0.001, respectively).


CONCLUSIONS
After nitrate administration, (99m)Tc-tetrofosmin uptake and perfusion defect severity were closely related to ceMRI, demonstrating, in vivo, the existence of an inverse correlation between the transmural distribution of fibrosis and tracer delivery to the myocardium.
Giorgetti
Assuero
A
Institute of Clinical Physiology, National Research Council, Pisa, Italy. asso@ifc.cnr.it
Pingitore
Alessandro
A
Favilli
Brunella
B
Kusch
Annette
A
Lombardi
Massimo
M
Marzullo
Paolo
P
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005080:Exercise Test; D005260:Female; D019786:Gadolinium DTPA; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000473:pathology; D009566:Nitrates; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology
D003287:Contrast Media; D009566:Nitrates; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin; D019786:Gadolinium DTPA