Comparison of Gated SPECT, Echocardiography and
Angiography Ejection Fractions
Mazen Omar, BS, Pavani Kolakalapudi, MD and Christopher Malozzi, DO
Division of Cardiology, University of South Alabama, Mobile, Alabama, United States, 36617
Abstract
Background: Gated stress studies with Thallium
previously suggested that SPECT overestimated the
ejection fraction (EF) obtained with other modalities,
limiting its use.
Discussion
EF
SPECT
TTE
Angio
64  12%
58  9%
53  6%
P < 0.01
Objective: To compare EF obtained from stress
gated SPECT (pharmacologic) using Technicium99m
with EF estimated by transthoracic echocardiography
(TTE) or cardiac catheterization (angio).
Methods: From a university-based outpatient stress
lab, 502 stress tests performed over 14 months were
reviewed; 126 gated pharmacologic stress tests were
analyzed. Contemporaneous TTEs were available in
114, and angios in 26 of the studies. The stress
nuclear protocols included a slow walk and the stress
agent was regadenoson in the majority of the studies.
Mean EF reported from the post-stress gated
SPECT, TTEs, and angios were tested with ANOVA.
The absolute variance in EF between each two
groups was averaged and compared using a 2-tailed
student t test to the other groups.
Results: The mean EF obtained from SPECT, TTE
and angio were 64 ± 12%, 58 ± 9% and 53 ± 6%
respectively (P < 0.01). The absolute variance in
SPECT-TTE and SPECT-angio were 9.2 ± 6.4% and
10.3 ± 7.7% respectively (P < 0.05 vs TTE angio);
TTE-angio absolute variance was 5.6 ± 4.8%.
msec
Absolute Variance in EF
SPECTTTE
9.2  6.4%
P = <0.05
SPECTAngio
10.3  7.7%
P = <0.05
TTEAngio
5.6  4.8%
Ejection fraction
obtained by stress
SPECT imaging may
overestimate the true
resting EF and cause
delay in therapy
Studies have conflicted with regards to reliability of
gated SPECT-derived left ventricular volumes and
ejection fractions. Although lack of correlation has
been suggested, overestimation of ejection fraction
has also been described. In this study we found a
tendency for SPECT to overestimate the ejection
fraction in post-stress gated studies compared with
echocardiography and cath. Although several
factors may have contributed to this observation, it
is possible that the SPECT EF is augmented by the
vasodilator effect of the stress pharmacologic
agent. Further studies are needed to better qualify
these findings. Meanwhile, given the importance of
accurate quantification of a resting ejection fraction,
especially as it relates evaluation of significant of
valvular abnormalities or device therapy in heart
failure, reliance on a SPECT derived ejection
fraction may cause undue delay in therapy.
References
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