Vasodilator stress agents for myocardial perfusion imaging
Received Jan
Vasodilator stress agents for myocardial perfusion imaging
Rayan Saab 0 2
Fadi G. Hage 0
FASNC 0
0 Reprint requests: Rayan Saab, MD, Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham , Lyons Harrison Research Building 306, 1720 2nd Ave S, Birmingham, AL 35294-0007
1 Section of Cardiology, Birmingham Veterans Affairs Medical Center , Birmingham, AL
2 Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham , Birmingham, AL
-
In this issue of the Journal, Yao et al report on the
prognostic value of adenosine triphosphate (ATP)
myocardial perfusion imaging (MPI) with
Technetium99 sestamibi (Tc-99m) in a population aged 70 years
and older.1 The ability to exercise in this population is
expected to be rather limited. A total of 415 patients with
suspected coronary artery disease (CAD) were identified
and retrospectively enrolled in the study. The primary
composite end point was major adverse cardiac events
(MACE) and included death from a cardiac etiology,
nonfatal myocardial infarction (MI), and late coronary
revascularization ([60 days). Sixteen patients met
exclusion criteria as they underwent early coronary
revascularization B60 days after MPI. Reversible and/or
fixed perfusion defects were considered abnormal and
patients were followed over a mean of 3.45 ± 1.71 years.
MACE occurred in 37 patients, including 9 cardiac
deaths, and was significantly lower in patients with
normal MPI, even after adjusting for other variables such
as age [80 years, male gender, chest pain or dyspnea,
hypertension, hyperlipidemia, diabetes mellitus, chronic
kidney disease, atrial fibrillation, and abnormal ATP
stress ECG. Each of the individual outcomes included in
MACE was also significantly lower in patients with
normal MPI. In addition, although patients aged
C80 years had higher MACE rates than those aged
7079 years when the summed stress score (SSS) was [8,
the two groups had similar MACE rates when the SSS
was B8. These results confirm the prognostic value of
ATP-MPI in an elderly population with suspected CAD.
The proportion of pharmacologic stress tests
performed in the United States has steadily increased over
the past several decades. Exercise stress testing is
favored over vasodilator stress, since it is more
physiological and since it assesses the functional capacity
which provides important prognostic information.2
However, when patients are not able to achieve a
specified gender and age-adjusted target heart rate and
exercise capacity, the test loses some of its diagnostic
and prognostic value. Further, a significant proportion of
the population in developed countries is unable to
exercise. This is likely the primary driver of the 23%
drop in the rates of exercise stress tests in 2006-2009 as
compared to 1991-1995.3 In these instances, and in other
special circumstances, such as the presence of left
bundle branch block or ventricular paced rhythm,
pharmacologic stress agents are used for myocardial
perfusion imaging. Pharmacologic stress agents
currently in use fall under two categories: the inotropes/
chronotropes that trigger a stress response by increasing
myocardial oxygen demand, and the vasodilator agents
that primarily trigger coronary vasodilation.4 The former
include dobutamine, arbutamine, and higenamine, a
b-receptor agonist derived from a traditional Chinese
medicine which is currently undergoing clinical trials in
China. The latter, which will be the focus of our
discussion, include dipyridamole, adenosine, adenosine
triphosphate (ATP) and regadenoson (Table 1). Of the
vasodilator agents mentioned, ATP, the pharmacologic
stress agent used in the study by Yao et al,1 is not
approved for use in the United States but is being used in
other parts of the world including Japan and China.
The currently used vasodilator stress agents all
mediate their effects, either directly or indirectly,
s
e tc ?
id fe ? ?
S f ? ?
e ?
?
?
?
a 5
H -4
0
3
t
u
o
b
A
H C
C
r
cae inng to tsa ,n fro ftre
tr ing in lte ino iso eun sa ino
ifrado jitceno ftraebe n itsenum iifsnuno fraeuo ftrsae jitrceen iiftnnuo ittcnoo itenum jitrceen
igno in itseun iifsuno ltsae2 i,fsnuo itcnno itenum itrcado itseun ifsnuo ltsae2 itrcado
m m fo t in to 2 ra m in ta ra
i
7 A 3
T
kg uno inu
g e m
c v
m tra r5
60 in fo
1
e
t
a
ien shp
s o
o h
en ir
p
d t
e
c
n
a
r
a
e
l
c
l
a
n
e
R
s
e
t
u
n
i
8
0
1
3
3
m
r s
te lu
f
a bo
s
d n
cno soo
se en
d
0 a
2 g
-0 re
1
n
o
s
o
n
e
d
a
g
e
R
l
o 1
c
e
o r t
ts t e u
n o v in
e r o
1
e
t
u
n
i
p 1 lsy -1m lsy tse -1m lsy tse
rd - u s
a kg no te kg uno inu
d g e u g e m
n m rav in c v
a m m tra r6
t 6 t
S .5 in 4 40 in fo
0 1
e
l
o
e
am isn
id o
r n
y e
ip d
D A
through activation of adenosine receptors. Adenosine is
an endogenous extracellular signaling molecule that
plays an important regulatory role in the human body. It
also constitutes the nucleoside base of both ATP and
cyclic adenosine monophosph (...truncated)