Background
The reported incidence of atrial fibrillation (AF) occurring during dobutamine stress echocardiography (DSE) ranges from 0.5% to 4%. The aim of this study was to characterize the incidence, risk factors, and outcomes of AF precipitated during DSE.
Methods
The clinical and echocardiographic data of consecutive patients over a 50-month period who were in sinus rhythm and underwent DSE were retrospectively reviewed.
Results
A total of 11,806 consecutive patients underwent DSE and met all inclusion criteria. AF developed during DSE in 122 patients (1%), 71 of whom had histories of AF. The duration of AF was <1 hour in 74 patients (61%) and <24 hours in 117 patients (96%). Of the 47 patients who were still in AF when dismissed from the echocardiography laboratory, 21 had outpatient follow-up within 24 hours, eight were already inpatients, and 18 were triaged to the emergency department or hospital. Spontaneous cardioversion occurred in 114 patients (93%). There were no reported complications. The clinical characteristic most strongly associated with the development of AF during DSE was a history of AF (odds ratio, 18.4 if no history of congestive heart failure; P < .001). The presence or extent of stress-induced myocardial ischemia was not predictive of the development of AF.
Conclusions
AF is an infrequent complication of DSE. Most patients return to sinus rhythm spontaneously within 1 hour. Patients with persistent AF can be safely dismissed from the echocardiography laboratory to have outpatient follow-up within 24 hours unless they have suboptimal heart rate control, hypotension, significant symptoms, or markedly abnormal findings on DSE.
Stress echocardiography is commonly used for the detection of ischemia and risk stratification in patients with suspected or known coronary artery disease. The pharmacologic stress agent dobutamine is often used when patients have functional limitations that preclude exercise stress testing. Dobutamine hydrochloride is a synthetic catecholamine that stimulates cardiac β receptors. Although widely used and generally well tolerated, dobutamine has been associated with the development of adverse effects, including anxiety, nausea, headache, dyspnea, chest pain, palpitations, changes in blood pressure, and supraventricular and ventricular arrhythmias. The reported incidence of atrial fibrillation (AF) occurring during dobutamine stress echocardiography (DSE) ranges from 0.5% to 4% in the literature. We sought to characterize the incidence, risk factors, and outcomes of AF precipitated during DSE.
Methods
Study Population
For all patients who undergo DSE at the Mayo Clinic (Rochester, MN), clinical and echocardiographic data are prospectively collected at the time of DSE and entered into a stress echocardiography database. For the current study, we reviewed this database and retrieved the records of all patients who underwent DSE from November 1, 2003, through December 31, 2007. Patients who had paced rhythm, had significant valvular heart disease, or were in AF or atrial flutter before beginning DSE were excluded. Patients who did not authorize the use of their records for research purposes also were excluded. If a patient had more than one dobutamine stress echocardiographic examination during this period, only the initial study was included. Patients who developed AF during DSE were compared with those who did not. The clinical courses of all patients who developed AF during DSE were reviewed. This study was approved by the Mayo Clinic Institutional Review Board.
DSE
Dobutamine was infused in incremental doses, in 3-min stages, to a peak dose of 40 μg/kg/min if needed. Thereafter, if the target heart rate had not been achieved (≥85% of age-predicted maximal heart rate), atropine was administered intravenously in 0.25-mg increments to a total dose of 2 mg as the dobutamine infusion was continued. Continuous electrocardiographic monitoring was performed, and 12-lead electrocardiograms were recorded at the end of each stage. Blood pressure was measured at baseline and at the end of each stage. Standard, predetermined end points for test termination were used, as previously described. Echocardiographic images obtained at baseline, low-dose dobutamine (10 μg/kg/min), prepeak, and peak stress were reviewed and interpreted in a digitized quad-screen format in standard views. The results of DSE were interpreted in a standard manner, with the overall change in left ventricular (LV) end-systolic size assessed visually, comparing the side-by-side rest and peak stress digitized images in four standard views. An abnormal LV end-systolic volume response was defined as no change or an increase in LV end-systolic volume with dobutamine. A normal result on DSE was defined as normal LV regional and global systolic function at rest and no dobutamine-induced regional wall motion abnormalities. An abnormal result on DSE was defined by the presence of rest and/or dobutamine-induced regional wall motion abnormalities. Results of DSE were positive for ischemia if new or worsening regional wall motion abnormalities developed with dobutamine. Any adverse effects, including atrial arrhythmias, were managed initially by the supervising registered nurse and the attending echocardiologist.
Definitions
Patients in whom either AF or atrial flutter developed during dobutamine infusion or in the recovery period comprised the AF group. Patients who were transferred to the emergency department or hospital for any reason were included in the analysis. Cardioversion with antiarrhythmic drugs was defined as cardioversion associated with the use of a new antiarrhythmic drug or a higher dose of the patient’s established antiarrhythmic drug regimen.
Statistical Analysis
Statistical analysis was performed using SAS version 9.1 (SAS Institute, Inc., Cary, NC). Continuous variables are summarized as mean ± SD and categorical variables as numbers and percentages. Baseline characteristics between patients with and without AF during DSE were analyzed by Pearson’s χ 2 analysis for categorical variables and two-sample t tests for continuous variables. Logistic regression analysis was used to determine the independent predictors of AF. The final multivariate model was selected in a stepwise manner using characteristics with univariate P values < .20 as candidate variables. P values < .05 were considered statistically significant.
Results
Patient Selection and Incidence of AF
For the 50-month study period, records of 14,510 dobutamine stress echocardiographic examinations were found; 578 were initially excluded because the studies were canceled or patients did not provide research consent. Other studies were excluded because they constituted repeat examinations ( n = 1,014), the patients had paced rhythm or baseline AF or atrial flutter ( n = 760), or the patients had significant valvular heart disease, defined as at least moderate mitral or aortic stenosis or at least moderately severe mitral or aortic regurgitation. Of the 352 patients with significant valvular disease who were excluded from this analysis, none developed AF during DSE. Of the remaining 11,806 patients, AF developed during DSE in 122 (1%). The characteristics of the study population, grouped according to whether or not AF developed, are shown in Tables 1 and 2 .
| Group | |||
|---|---|---|---|
| No AF | AF | ||
| Characteristic | ( n = 11,684) | ( n = 122) | P |
| Age (y) | 67.2 ± 12.5 | 74.0 ± 10.6 | <.001 |
| BMI (kg/m 2 ) | 29.7 ± 6.8 | 29.1 ± 5.9 | .29 |
| Men | 6,015 (51%) | 69 (57%) | .26 |
| Hypertension | 8,289 (72%) | 92 (76%) | .32 |
| Diabetes mellitus | 3,322 (29%) | 27 (22%) | .12 |
| Hyperlipidemia | 7,245 (63%) | 78 (64%) | .72 |
| Smoking history | 6,320 (55%) | 63 (53%) | .53 |
| Family history of CAD | 3,935 (34%) | 37 (31%) | .40 |
| Chest pain | 3,402 (30%) | 35 (29%) | .88 |
| Dyspnea | 4,212 (37%) | 54 (45%) | .07 |
| Prior MI | 1,638 (14%) | 14 (12%) | .40 |
| Prior CABG | 1,332 (12%) | 16 (13%) | .55 |
| Prior PCI | 1,490 (13%) | 17 (14%) | .72 |
| History of CHF | 1,148 (10%) | 18 (15%) | .07 |
| History of AF | 843 (7%) | 71 (58%) | <.001 |
| β-blocker | 5,326 (46%) | 60 (50%) | .46 |
| CCB | 2,424 (21%) | 38 (31%) | .005 |
| Digoxin | 314 (3%) | 9 (7%) | .002 |
| Abnormal baseline ECG results | 6,837 (59%) | 83 (69%) | .04 |
| LBBB | 383 (3%) | 4 (3%) | .99 |
| RBBB | 698 (6%) | 13 (11%) | .03 |
| Group | |||
|---|---|---|---|
| No AF | AF | ||
| Characteristic | ( n = 11,684) | ( n = 122) | P |
| Ejection fraction (%) | |||
| Baseline | 60 ± 9 | 60 ± 7 | .55 |
| Peak stress | 70 ± 11 | 70 ± 10 | .99 |
| Wall motion score index | |||
| Baseline | 1.14 ± 0.31 | 1.12 ± 0.24 | .59 |
| Peak stress | 1.18 ± 0.35 | 1.18 ± 0.30 | .99 |
| Resting heart rate (beats/min) | 69 ± 13 | 65 ± 10 | <.001 |
| Peak heart rate (beats/min) | 131 ± 15 | 140 ± 20 | <.001 |
| Peak dobutamine dose (μg/kg/min) | 35.2 ± 7.6 | 33.8 ± 7.0 | .03 |
| Atropine administered | 7,118 (61%) | 76 (62%) | .76 |
| Results of DSE | |||
| Normal | 7,737 (66%) | 74 (61%) | .19 |
| Positive for ischemia | 2,825 (24%) | 38 (31%) | .07 |
| Five or more ischemic segments | 825 (7%) | 12 (10%) | .24 |
| Abnormal LVESV response | 586 (5%) | 7 (6%) | .75 |
Factors Associated with the Development of AF during DSE
Several patient characteristics were univariately associated with the development of AF. These included older age, history of AF, abnormal baseline electrocardiographic findings, right bundle branch block, lower resting heart rate, and higher peak heart rate during stress ( Tables 1 and 2 ). Variables that were not predictive of AF included prior coronary revascularization, history of myocardial infarction, the use of atropine during DSE, and the stress echocardiographic findings. Neither the presence nor the extent of stress-induced myocardial ischemia was predictive of the development of AF.
The multivariate model identified an interaction between a history of AF and congestive heart failure (CHF). Patients with histories of AF without prior CHF were at the greatest risk for AF developing during DSE (odds ratio, 18.4; 95% confidence interval, 12.2–27.7 vs patients without histories of either AF or CHF; P < .001; Table 3 ). Patients with histories of both CHF and AF were also at increased risk for AF (odds ratio, 8.0; 95% confidence interval, 4.11–15.5; P < .001). Those with histories of CHF in the absence of a history of AF, however, did not have an increased risk for AF (odds ratio, 1.28; 95% confidence interval, 0.54–3.03; P = .58). Of the 446 patients with baseline LV ejection fractions < 40%, only one developed AF during DSE (0.2%).
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