Left ventricular functional assessment in mice: feasibility of high spatial and temporal resolution ECG-gated blood pool SPECT.
OBJECTIVE
To prospectively determine feasibility of evaluating murine left ventricular (LV) function with electrocardiographically (ECG)-gated blood pool single photon emission computed tomography (SPECT).


METHODS
All animal studies had institutional animal care and use committee approval. SPECT was performed with conventional time-binned acquisition (eight frames per ECG cycle) in normal mice (normal group A, n = 6) and mice with myocardial infarction (MI) (n = 8). To determine feasibility of high temporal resolution and rapid data acquisition, another group of normal mice (normal group B, n = 4) underwent imaging with conventional (eight-frame) time-binned and list-mode (LM) acquisitions. LM acquisitions were reconstructed with eight and 16 frames per ECG cycle and 10 minutes of data (short LM). SPECT images were assessed visually, and LV-to-lung background activity ratios were calculated. LV end-systolic and end-diastolic volumes were defined with a phase analysis and threshold method. LV ejection fraction (LVEF) was calculated from LV volumes and count-based methods (n = 18 mice). Fractional shortening (FS) at echocardiography defined MI dysfunction (mild MI: FS > or = 50%; severe MI: FS < 50%). Group means were compared for significant differences with analysis of variance.


RESULTS
ECG-gated blood pool SPECT demonstrated normal, concentric LV contraction in all normal mice (n = 10). LV-to-lung background ratio was more than 10:1 (range, 10.3-29.4; n = 18). Focal wall motion abnormalities were detected at SPECT both visually and with phase analysis in all mice with severe MI (n = 5). Mice with severe MI had significantly lower LVEF than normal group A mice (32% +/- 14 [standard deviation] vs 64% +/- 8%; P < .001). All mice with mild MI (n = 3) had normal contraction and LVEF. In paired acquisitions in normal group B mice, all reconstructions (n = 16) showed normal LV contraction. LVEF was not significantly different (P = .88) between time-binned (71% +/- 12), eight-frame LM (71% +/- 12), 16-frame LM (77% +/- 10), and short LM (73% +/- 14) reconstructions.


CONCLUSIONS
Murine LV functional assessment is feasible with high spatial and temporal resolution ECG-gated blood pool SPECT. LV dysfunction can be quantified and focal wall motion abnormalities detected in the MI model of heart failure.
Chin
Bennett B
BB
Department of Radiology, Duke University School of Medicine, Durham, NC 27710, USA. chin0004@mc.duke.edu
Metzler
Scott D
SD
Lemaire
Anthony
A
Curcio
Antonio
A
Vemulapalli
Sreekanth
S
Greer
Kim L
KL
Petry
Neil A
NA
Turkington
Timothy G
TG
Coleman
R Edward
RE
Rockman
Howard
H
Jaszczak
Ronald J
RJ
D000818:Animals; D004562:Electrocardiography / Q000379:methods*; D005240:Feasibility Studies; D015637:Gated Blood-Pool Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000150:complications / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology