Methods
All patients were evaluated by a cardiologist. Each patient received a
complete medical history and physical examination. A 12-lead resting
electrocardiogram, chest x-ray, comprehensive metabolic panel, fasting
lipid panel, urinalysis, complete blood count, and a serum thyroid
stimulating hormone were performed on or obtained from all patients.
Electrolyte abnormalities, if present, were corrected prior to
electrocardiography and stress testing.
At the time of this study, DSE was the preferred stress testing modality
by our bariatric surgeons. DSE was performed in accordance with American
Society of Echocardiography recommendations.9,10Following acquisition of baseline images, dobutamine was administered by
IV infusion beginning with a dose of 5 mcg/kg/min. The dose was
increased at 3-minute
Alpert
intervals in a graded fashion from 5 to 10 to 20 to 40 mcg/kg/min. Blood
pressure, heart rate, and 12 lead electrocardiograms were recorded and
echocardiographic images were obtained at baseline and during the third
minute of dobutamine infusion for each dose. There was continuous
electrocardiographic rhythm monitoring. The test was terminated after
data acquisition at the dose of dobutamine that produced a heart rate ≥
85% of the predicted (target) heart rate or following infusion of the
40 mcg/kg/min dose. If ≥ 85% of target heart rate was not achieved with
infusion of the peak dose of dobutamine, atropine sulfate was
administered by bolus IV injection during the final stage starting with
a dose of 0.5 mg followed by subsequent doses of 0.5 mg every 5 minutes
until ≥ 85% of target heart rate was achieved or until the patient
received a total dose of 2.0 mg.
Due to an extended pause in the commercial availability of the IV
contrast-enhancing agent Optison, our medical system relied solely on
non-contrast images with DSE during the period of unavailability of
Optison. During this period 62 consecutive eligible patients with class
III obesity were entered into the study and underwent DSE without
intravenous contrast injection. Subsequently, when the use of
intravenous contrast agents was deemed safe for use during DSE, 66
consecutive eligible patients underwent DSE with intravenous contrast
injection. With the subsequent availability of Definity (Perfluten Lipid
Micrspheres, Lantheus Medical Imaging, North Billerca, MA), intravenous
contrast injection resumed. Intravenous contrast injection consisted of
bolus IV infusion of Definity. The dose was 10 microL/kg, agitated and
injected over 30-60 seconds and followed by a 10 mL normal saline flush.
In patients who received Definity, bolus infusion occurred just prior to
acquisition of baseline echocardiographic images. As previously noted,
patients enrolled in this prospective study were not randomized. No
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attempt was made to match patients who received IV contrast with those
who did not receive IV contrast.
Transthoracic 2-dimensional echocardiographic images were obtained using
a General Electric Vivid E9 echocardiograph with a GE M5S-DM 1.5-4.5 MHz
transducer probe with second harmonic capability. Images were arranged
in a quad screen format. LV regional wall motion was assessed in
accordance with American Society of Echocardiography
guidelines.9,10 Sixteen LV segments visualized in 4
planes were evaluated for evidence of myocardial ischemia as follows:
Parasternal or apical long axis (mid-anteroseptal, basal anteroseptal,
basal posterior, mid-inferolateral), parasternal short axis
(mid-anterior, mid-anteroseptal, mid septal, mid- inferior,
mid-inferolateral, mid-lateral), apical 4-chamber (apical septal,
mid-septal, basal septal, basal lateral, mid-lateral, apical lateral),
and-apical 2-chamber (apical anterior, mid-anterior, basal anterior,
apical inferior, mid-inferior, basal inferior).9,11Myocardial ischemia was diagnosed when normal LV regional wall motion
segments at baseline transformed into dobutamine-induced hypokinesis,
akinesis, or dyskinesis, or if there was dobutamine-induced global LV
cavity dilatation and reduction of LV systolic function and failure of
LV myocardial segment(s) to thicken during dobutamine
stress.9-11 Individual regional LV segments were
assessed at baseline and at peak stress. Individual LV segments were
classified as “well-visualized and interpretable” or
“poorly-visualized and not interpretable”.9-11Well-visualized LV segments were those in which the endocardial border
was well-defined and interpretable for echocardiographic signs of
myocardial ischemia. LV segments that were poorly-visualized included
those in which the subendocardial border in part was poorly-defined or
non-visualized
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and not interpretable for echocardiographic signs of myocardial
ischemia. The numbers of LV segments that were well-visualized and
interpretable for echocardiographic signs of myocardial ischemia in the
group that received intravenous contrast and in the group that did not
receive intravenous contrast were recorded and reported.
This study was not designed to assess long-term CV outcomes.
Nevertheless, we cataloged CV outcomes during DSE (regional LV wall
motion abnormalities, hypertension, hypotension, arrhythmias) and 6
months after bariatric surgery (all-cause and CV deaths, angina
pectoris, myocardial infarction, stroke).
All procedures involving human participants in this study were in
accordance with the ethical standards of the 1964 Helsinki declaration
and its later amendments and comparable ethical standards. Informed
written consent was obtained from all patients participating in this
study. This study was approved by the University of Missouri-Columbia
School of Medicine Institutional Review Board.