We retrospectively studied 311 patients with known or suspected coronary artery disease, referred to our department for a myocardial ischemia assessment between 2006 and 2012. 203 underwent exercise stress echocardiography (160 males, mean age 59.2+/−8.6 years) and 108 had dobutamine stress echocardiography (48 males, mean age 62.9+/−11.3 years). Clinical characteristics including a history of diabetes, hypertension, hypercholesterolemia, cigarette smoking, ischemic disease related medications, prior myocardial infarction, prior percutaneous coronary angioplasty and prior coronary artery bypass grafting were recorded for all patients.
Exercise stress echo was conducted using a semi-supine bicycle ergometer with 25 W incremental loading every 2 minutes. At the end of each stage, the heart rate, the blood pressure and a 12-lead ECG were recorded. Echocardiographic images were acquired with the patient on the bicycle at rest, at peak exercise and at recovery period.
Pharmacological stress echo was performed using dobutamine. Dobutamine was administered intravenously with an infusion pump, beginning at a dose of 5 to 10 μg/kg per minute and increased by 10 μg/kg every 3 minutes up to a maximum of 40 μg/kg per minute. Atropine was added at doses of 0.25 mg each minute to a maximum of 2 mg when starting the dobutamine dose of 20 μg/kg/min if heart rate was <100 beats/min. The blood pressure, the heart rate and clinical symptoms were monitored; a 12-lead electrocardiogram was obtained at baseline, at the start of the dobutamine infusion and at the end of each 3-min interval. Echocardiographic images were acquired at rest, at small doses, at peak dose and at recovery period.
Images in standard views were acquired and displayed side by side in a quad-screen format. All images were recorded on videotape and digitized in continuous-loop format. The left ventricle was divided into 17 segments according to the recommendations of the American Society of Echocardiography . A 4-point score was assigned to each segment as follows: 1 = normal, 2 = hypokinesia, 3 = akinesia, and 4 = dyskinesia. A wall motion score index was derived by dividing the sum of individual segment scores by the number of interpretable segments. A normal stress response is defined by a uniform increase in wall motion and systolic wall thickening, with a reduction in end-systolic cavity area. Ischemic response was defined as the development of new or the worsening of pre-existing wall motion abnormalities in 2 contiguous segments. The “biphasic” response (low-dose improvement followed by high-dose deterioration) was also regarded as criterion for ischemia , whereas rest akinesia becoming dyskinesia was not. Images analysis was made by the same experimented operator (N.D).
Stress echo was stopped when 85% of age-predicted target heart rate was reached, if the patient developed severe chest pain, ST segment elevation > 0.1 mV at 80 ms from the J point, new segmental wall motion abnormalities or significant adverse effects.
Adverse events definitions
Major rhythmic events are defined as a life threatens rhythmic complications (cardiac asystole, advanced atrioventricular block, ventricular fibrillation or ventricular sustained tachycardia) or complications that require hospital admission (supraventricular tachycardia).
Minor rhythmic events are defined as the development of uniform or multiform premature ventricular beats, ventricular bigeminy or couplets and nonsustained ventricular tachycardia.
Severe hypotension was defined by an arterial pressure drop ≥ 40 mmHg with symptoms.
Minor side effects were defined as the development of headache, nausea and muscular pain.
Continuous variables are expressed as means ± standard deviations and categorical variables are expressed as percentages. To compare between the dobutamine echocardiography group and the exercise echocardiography group, the continuous variables were analyzed using Student’s t-test and the categorical variables were analyzed using the Chi-square test. A p < 0.05 was considered statistically significant.
The statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 18.0 (SPSS Inc., Chicago, IL, USA).