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
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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.