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Abstract
Dobutamine-atropine stress echocardiography (DASE) is
well established in clinical practice, as it is considered to be one
of the main methods of imaging to determine the presence of
myocardial ischemia.
Currently, the use of the 3 min. protocol has become the
most popular, beginning at 5 mcg/kg/min infusion of
dobutamine and reaching a maximum dose of 40 mcg/kg/ min,
with the addition of atropine from the final stage on. Even
though atropine has been used more often at the end of the
stress test to increase heart rate and accuracy, this agent is
usually administered during or soon after the maximum dose of
dobutamine, with the patients receiving prolonged amine
infusions which may increase side effects. Besides, the test time
is often extended.
Considering that a significant number of patients (32%)
do not reach a dobutamine stress echocardiographic end point
with the standard protocol (Weissman et al.,1997), and the
increasing use of Beta blockers as anti-ischemic or antihypertensive
medication in the last decade, the following
question should be considered: Are the protocols employed in
stress echocardiography still in agreement with current medical
practice ?
Summary & Conclusion
188
If the range of the ideal heart rate, which is of extreme
importance to the accuracy of the method, is compromised, then
the need for a more homogenous protocol which
counterbalances the employed therapeutic effect becomes
relevant so as to avoid damage to the diagnostic and prognostic
information of the test.
The aim of this study was to assess the sensitivity,
validity & safety of atropine when initiated early during
dobutamine stress echocardiography in relation to its later
usage.
Forty consecutive patients were examined by dobutamine
stress echocardiography. The patients were randomly divided
into two protocols of study
Group (A):- 20 consecutive patients were subjected to
the early administration of atropine at a dose of 20 mcg/kg/min
of dobutamine, and;
Group (B):- 20 consecutive patients were subjected to
the late or standard administration of atropine at a dose of 40
mcg/kg/min of dobutamine, this in case heart rate obtained was
below 85% of maximum rate expected for age (220 – age) and
there wasn’t any criteria for interruption of the test occurred
(such as: new abnormality in wall motion or a worsening of an
existing one, heart rate = or > 85% of maximum rate expected
for age, important increase of systolic or diastolic blood
pressure (SBP > 220 mmHg and/or DBP > 110 mmHg),
Summary & Conclusion
189
relevant cardiac arrhythmia (supraventricular arrhythmia with
high response and/or malignant ventricular arrhythmia), intense
angina (specially if associated with worsening of regional
function), pronounced hypotension (decrease of SBP > 20
mmHg) followed by symptomatology, and conclusion of
protocol.
All the patients were subjected to the following:-
1) 1-History taking.
2) 2-General & local clinical examination.
3) 3-Stress echocardiogram.
4) -Echocardiographic evaluation.
5) 5-Coronary angiography.
Summary & Conclusion
190
Echocardiographic evaluation:-
The left ventricle was divided into 16 segments.Each
segment was described as: normal, hypokinetic, akinetic or
dyskinetic. A normal dobutamine stress echocardiogram was
defined as having normal wall motion at rest with an increase of
its systolic thickening during stress (hyperkinesia). The
presence of ischemia (positive test) is defined as the
development of a new abnormality in wall-motion or a
worsening of an existing one during stress (hypokinesia,
akinesia or dyskinesia).
Stress echocardiogram:-
The patients were submitted to the two-dimensional
echocardiograms for full analysis of cardiac performance. The
images obtained will be of the long axis, short axis, apical four
and two chambers which correspond to the viewing of the
myocardial segments supplied by the main coronary arteries.
Dobutamine was diluted and was administered through
an infusion pump initially at a dose of 5 mcg/kg/min and
increased to 10, 20, 30 mcg/kg/min every 3 minutes up to
maximum dose of 40 mcg/kg/min (according to each group).
The atropine sulfate was initiated at a dose of 0,25 up to 0,50
mg and increased in intervals of 1 to 2 minutes respectively,
until a maximum dose of 2 mg. This agent was administered
intravenously in the last minute of the stage, whereas the
dobutamine infusion remained continuous. During the exam, a
Summary & Conclusion
191
continuous check up of heart rate and blood pressure was being
done.
At the peak of test, after achieving the end points, the
dobutamine and atropine infusions were interrupted and
monitoring were continued during 5 to 10 minutes of the
recovery phase (eventually, for a longer period if necessary),
until heart rate was lower than 100 bpm and other clinical and
hemodynamic parameters were normal.
When comparing the results of both groups, the following was
found:
The sensitivity for detection of individual coronary artery
lesions in group A was 94.4, 89.5 & 88.9 % for LAD, RCA and
LCX consecutively.
While the sensitivity for detection of individual coronary
artery lesions in group B was 71.4, 94.1 & 83.3 % for LAD,
RCA and LCX consecutively.
The overall sensitivity in both groups was 91, 83.7 % %
for group A & group B consecutively.
Positive predictive values (PPV) of individual coronary
artery lesions in group A was 94.4, 94.4 & 94.1 % for LAD,
RCA and LCX consecutively.
Summary & Conclusion
192
Positive predictive values (PPV) of individual coronary
artery lesions in group B was 90.9, 94.1 & 100 % for LAD,
RCA and LCX consecutively.
The overall PPV in both groups was 94.3, 94.7 % for
group A & group B consecutively.
The accuracy of detection of individual coronary artery
lesions in group A was 90, 85 & 85 % for LAD, RCA and
LCX consecutively.
The accuracy of detection of individual coronary artery
lesions in group B was 75, 90 & 90 % for LAD, RCA and
LCX consecutively.
The overall accuracy in both groups was 86.7, 85 % for
group A & group B consecutively.
The mean test time in Group A (15.55 ± 3.52) & Group
B (23.55 ± 3.86) .The double product was higher in Group A.
In group (A), the most commonly occurred complication
was chest pain (85%), while in group (B) the most commonly
occurred complication was also chest pain (100%).
Few patients developed non-cardiac adverse effects in the
form of nausea, vomiting, headache and tremors (10% in group
A, 15% in group B).No one had a serious complication as
death, myocardial infarction, ventricular tachycardia or
ventricular fibrillation.
Summary & Conclusion
193
So based on our findings, we may conclude that:
The early intervention with atropine allowed for a more
balanced test regarding chronotropism and inotropism,
optimizing time and maximizing the double product, besides
being responsible for the reduction of the total dobutamine dose
without increasing side effects.
In our study, the early administration of atropine at 20
mcg of dobutamine seemed the most adequate since it presented
a higher double product and fewer complications. Overall, the
early administration of atropine is indicated to all patients
submitted to the test, including those patients receiving Beta
blockers.
Overall, the early administration of atropine is indicated
to all patients submitted to the test, including those patients
receiving Beta blockers.