The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 60:1333-1338 (2005)
© 2005 The Gerontological Society of America
Long-Term Prediction of Mortality in Elderly Persons by Dobutamine Stress Echocardiography
Elena Biagini1,2,
Abdou Elhendy1,
Arend F. L. Schinkel1,
Vittoria Rizzello1,
Jeroen J. Bax3,
Fabiola B. Sozzi1,
Miklos D. Kertai1,
Ron T. van Domburg1,
Boudewijn J. Krenning1,
Angelo Branzi2,
Claudio Rapezzi2,
Maarten L. Simoons1 and
Don Poldermans1,
1 Department of Cardiology, Thoraxcenter, Erasmus MC, Rotterdam, The Netherlands.
2 Institute of Cardiology, S. Orsola Hospital, Bologna, Italy.
3 Department of Cardiology, Leiden University Medical Center, The Netherlands.
Address correspondence to Don Poldermans, MD, PhD, Department of Cardiology, Thoraxcenter, Room Ba 300, Erasmus MC, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. E-mail: d.poldermans{at}erasmusmc.nl
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Abstract
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Background. Dobutamine stress echocardiography (DSE) was shown to provide incremental prognostic information. However, its role in the prediction of mortality in elderly persons is not well defined. We assessed the value of DSE in the prediction of mortality and hard cardiac events during long-term follow-up in patients older than 65 years.
Methods. We studied 1434 patients >65 years old (mean age 72 ± 3 years) who underwent DSE for evaluation of coronary artery disease. Ischemia was defined as new or worsening wall motion abnormalities. Follow-up events were total mortality and hard cardiac events (cardiac mortality and nonfatal myocardial infarction). Multivariable Cox regression analysis was used to identify the independent predictors of follow-up events.
Results. Ischemia was detected in 675 patients (47%). Five hundred six patients (35%) had a normal study, and 253 (18%) had fixed wall motion abnormalities. During a mean follow-up of 6.5 years, 532 (37%) deaths occurred, of which 249 (17%) were due to cardiac causes. A nonfatal myocardial infarction occurred in 45 patients (3%). Independent predictors of all-cause mortality in a multivariate analysis model were age (hazard ratio [HR] 1.06; 95% confidence interval [CI], 1.05–1.08), male sex (HR 1.5; 95% CI, 1.2–1.8), hypertension (HR 1.2; 95% CI, 1.1–1.4), smoking (HR 1.3; 95% CI, 1.1–1.6), diabetes (HR 1.4; 95% CI, 1.1–1.8), rest wall motion abnormalities (HR 1.07; 95% CI, 1.06–1.09), and ischemia (HR 1.3; 95% CI, 1.1–1.6). Independent predictors of hard cardiac events were age (HR 1.07; 95% CI, 1.05–1.09), male sex (HR 1.3; 95% CI, 1.1–1.7), smoking (HR 1.3; 95% CI, 1.1–1.6), diabetes (HR 1.6; 95% CI, 1.2–2.2), rest wall motion abnormalities (HR 1.13; 95% CI, 1.12–1.16), and ischemia (HR 2.1; 95% CI, 1.5–2.8).
Conclusion. DSE provides independent prognostic information to predict all-cause mortality and hard cardiac events in elderly patients.
DEMOGRAPHIC studies have shown that elderly persons constitute a rapidly expanding segment of our population. Coronary artery disease (CAD) is a major cause of morbidity and mortality in elderly persons and becomes more prevalent with increasing age (1,2). Technical advances in myocardial revascularization procedures have recently contributed to a high success rate of coronary artery bypass grafting and percutaneous coronary intervention in elderly persons (3–6) with an improved clinical outcome (7). Exercise echocardiography has been demonstrated as a useful noninvasive tool for evaluation of CAD in elderly persons (8). However, exercise stress testing is not feasible in many elderly patients (9), mostly because of noncardiac factors, such as arthritis, obstructive lung disease, claudication, and poor physical conditioning. Dobutamine stress echocardiography (DSE) is a feasible alternative to exercise in these patients (10–12). Published studies of the prognostic value of DSE in elderly persons are limited by inclusion of a small number of patients, short-term follow-up, and the use of composite end points. Additionally, there are currently no data to suggest a role of DSE in the prediction of all-cause mortality in elderly persons. Accordingly, the aim of this study was to assess the long-term value of DSE for prediction of all-cause mortality and hard cardiac events in a large number of patients with known or suspected CAD who are >65 years old.
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METHODS
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Patients
The study population was composed of 1606 consecutive patients >65 years old who were referred for DSE for the evaluation of suspected or known CAD at the Thoraxcenter, Rotterdam between January 1988 and January 2003 and who were unable to perform an adequate exercise test. Follow-up was successful in 1590 patients (99%). A total of 156 patients (10%) underwent early coronary revascularization in the first 60 days after the DSE. These patients were excluded from the analysis, because referral to myocardial revascularization in the first 60 days after stress testing tends to be based on the results of the test (13). Therefore, 1434 patients represented the final population. The protocol was approved by the Hospital Ethics Committee. All patients gave informed consent before the test. A structured interview and review of records were conducted prior to the stress test to obtain clinical history and to determine cardiac risk factors.
Dobutamine Stress Protocol
Low-high dose DSE (up to 40 µg/kg/min plus 2 mg of atropine, if necessary) was performed according to a standard protocol as previously reported (12). Test end points were achievement of target heart rate (85% of maximum age- and sex-predicted heart rate), maximal dose of dobutamine and atropine, extensive new wall motion abnormalities, >2 mV downsloping ST-segment depression measured 80 ms after the J point compared with baseline, hypertension (blood pressure > 240/120 mmHg), a decrease in systolic blood pressure of >40 mmHg compared with blood pressure at rest, significant arrhythmias, or any intolerable adverse effect considered to be the result of dobutamine or atropine. An intravenous ß-blocker (1–5 mg of metoprolol) was available to reverse the adverse effects of dobutamine or atropine if these did not reverse spontaneously.
Echocardiographic Imaging and Interpretation
Two-dimensional echocardiographic images were acquired at rest, during dobutamine stress, and during recovery. The echocardiograms were recorded in a quad-screen format. Two experienced observers, unaware of the clinical data, scored the echocardiograms using a standard 16-segment model. In case of disagreement, a consensus decision was achieved by a third observer. Regional wall motion and systolic wall thickening were scored on a 5-point scale (1 = normal, 2 = mild hypokinesia, 3 = severe hypokinesia, 4 = akinesia, 5 = dyskinesia). Ischemia was defined as new or worsened wall motion abnormalities during stress indicated by an increase of wall motion score 
1 grade in more than one segment. A biphasic response in an akinetic or severely hypokinetic segment was considered to be an ischemic response. Ischemia was not considered to be present when akinetic segments at rest became dyskinetic during stress. For each patient, a wall motion score index (WMSI) was calculated by dividing the sum of scores of visualized segments by the total number of these segments.
Follow-Up
Follow-up data collection was performed by contacting the patients and general practitioners and reviewing hospital records. The date of the last review or consultation was used to calculate follow-up time. Follow-up events noted were all causes of mortality and hard cardiac events (nonfatal myocardial infarction and cardiac death). Revascularization procedures were also noted. Cardiac death was defined as death caused by acute myocardial infarction, significant cardiac arrhythmias, or refractory congestive heart failure. Sudden death occurring without another explanation was considered to be cardiac death. Nonfatal myocardial infarction was defined by the standard criteria of chest pain, cardiac enzymes, and electrocardiographic changes.
Statistical Analysis
Continuous data were expressed as mean value ± standard deviation. The Student t test was used to analyze continuous data. Differences between proportions were compared using the chi-square test. Univariate and multivariate Cox proportional hazard regression models (BMDP Statistical Software Inc., Los Angeles, CA) were used to identify independent predictors of end points of interest (14). Variables were selected in a stepwise forward selection manner with entry and retention set at a significance level of.05. The risk of a variable was expressed as a hazard ratio (HR) with a corresponding 95% confidence interval (CI). The incremental value of DSE over the clinical variables in the prediction of events was determined according to two models. In model I, the variable entered was the presence of new wall motion abnormalities during peak stress; in model II, the number of segments with new wall motion abnormalities at peak of DSE (extent of ischemia) was entered as a continuous variable. The probability of survival was calculated using the Kaplan–Meier method, and survival curves were compared using the log-rank test. A p value <.05 was considered statistically significant.
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RESULTS
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Patient Characteristics and Hemodynamic Response
The mean age was 73 ± 5 years, 965 patients (67%) were men, and 440 patients (31%) were >75 years old (mean 79 ± 3.2 years). Clinical characteristics are presented in Table 1.
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Table 1. Clinical Characteristics in Patients With and Without Hard Cardiac Events (Cardiac Death or Nonfatal Myocardial Infarction).
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Dobutamine stress test data are presented in Table 2. Heart rate increased significantly from rest to peak stress. The mean maximal dobutamine dose was 35 ± 8 µg/kg/min. Atropine was used in 361 patients (25%). Side effects were nonsustained ventricular tachycardia (<10 complexes) in 59 patients (4%), atrial fibrillation in 28 patients (2%), severe hypotension (decrease in systolic blood pressure >40 mmHg compared to baseline) in 10 patients (0.7%), and ventricular fibrillation in 2 patients (0.1%). Defibrillation was successful and no echocardiograph or cardiac enzymatic changes suggesting myocardial infarction were observed in these two patients. The test was terminated because of the following: reaching the target heart rate in 1278 patients (89%), reaching maximal dose of dobutamine and atropine in 45 patients (3%), or noting ST-segment changes (in 38 patients, 3%), minor symptoms (in 30 patients, 2%), abnormal blood pressure (in 15 patients, 1%), arrhythmias (in 14 patients, 1%), and angina (in 14 patients, 1%).
Echocardiographic Data
Five hundred six patients (35%) had a normal study, 253 patients (18%) had fixed wall motion abnormality, and 675 patients (47%) had ischemia (new or worsening wall motion abnormalities). Among patients with ischemia, 586 (41%) had resting wall motion abnormalities as well. Among patients with resting wall motion abnormalities, resting WMSI was lower in patients who had no inducible ischemia during DSE as compared to patients who had ischemia (1.39 ± 0.38 vs 1.96 ± 0.62, p <.0001).
Outcome
During a mean follow-up of 6.5 years (range 6 months–15 years), there were 532 (37%) deaths, of which 249 (17%) were attributed to cardiac causes. Forty-five (3%) patients had nonfatal myocardial infarction and 334 (23%) underwent late revascularization. Clinical, hemodynamic, and echocardiographic data of patients with and without hard cardiac events are listed in Tables 1 and 2. Patients with cardiac events had a higher incidence of ST-segment depression, a higher WMSI at rest, and a higher incidence and extent of ischemia as compared to patients without events.
Predictive Value of Clinical Data and Test Results
Univariate and multivariate predictors of cardiac death or nonfatal myocardial infarction and all causes of mortality are shown in Tables 3 and 4. Among clinical variables, age, male sex, smoking, and diabetes were multivariate independent predictors of cardiac death or nonfatal myocardial infarction and of all-cause mortality. A history of hypertension was a predictor of all causes of mortality. The presence of rest wall motion abnormalities provided independent prognostic information for hard cardiac events and all-cause mortality. Moreover, the presence and the extent of ischemia during DSE provided incremental information for both end points (Models I and II). Kaplan–Meier survival curves for the end point of cardiac death or nonfatal myocardial infarction in patients with normal, fixed wall motion abnormalities and ischemia are presented in Figure 1. The combination of rest and inducible wall motion abnormalities identified the group with the highest risk of hard cardiac events (p <.0001). At 5 years of follow-up, the annual hard cardiac events rate was 1.8% in patients with a normal test, 2.1% in patients with fixed wall motion abnormalities, 4.3% in patients with ischemia, and 8% in patients with both resting and inducible wall motion abnormalities.
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Figure 1. Kaplan–Meier survival curves (end point of cardiac death and nonfatal myocardial infarction) based on results of dobutamine stress echocardiography
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Among patients with a normal DSE, the annual hard cardiac event rate was 1.3% in patients 
75 years old and 2.8% in patients >75 years old (p =.1). Figure 2 illustrates the incremental contribution of resting wall motion abnormalities and ischemia during DSE to clinical data in predicting hard cardiac events and total mortality. Both resting and dobutamine-induced wall motion abnormalities were incremental to clinical data in the prediction of each end point. The major increment in prognostic information was made by resting left ventricular function.
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Figure 2. Incremental prognostic value of ischemia over clinical data and resting left ventricular function for prediction of hard cardiac events (A) and all-cause mortality (B). DSE = dobutamine stress echocardiography
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DISCUSSION
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This study assessed the incremental value of DSE in the prediction of long-term mortality and hard cardiac events in 1434 elderly patients with known or suspected CAD. During a mean follow-up of 6.5 years, 532 patients (37%) died; of these, 249 patients (17%) died because of cardiac causes. The annual hard cardiac event rate was 1.8% in patients with normal DSE and 5.7% in patents with abnormal DSE. Patients with both resting and dobutamine-induced wall motion abnormalities were at highest risk of cardiac events with an annual rate of 8%. Predictors of cardiac death or nonfatal myocardial infarction and all causes of mortality were age, male sex, smoking, diabetes, and rest wall motion abnormalities. The presence and the extent of ischemia during DSE provided incremental information in a multivariate analysis over clinical and resting echocardiographic data for the prediction of both hard cardiac events and all-cause mortality. Patients with fixed wall motion abnormalities showed a marginally higher event rate than did patients with a normal DSE. This could be explained by the fact that the most of these patients had less severe resting left ventricular dysfunction as compared to patients who had both resting and inducible wall motion abnormalities.
Comparison to Previous Studies
To our knowledge, this is the longest-term follow-up study in elderly patients undergoing stress imaging for evaluation of CAD. Additionally, this is the first study to document an incremental value for stress imaging in predicting all-cause mortality in elderly patients.
Feasibility and safety of the dobutamine–atropine stress test have been previously reported in elderly patients (15–18). However, prognostic studies are scarce. Anthopoulos and colleagues (19) studied 120 patients 70 years old admitted for chest pain who underwent adenosine and dobutamine stress echocardiography and coronary angiography. During a follow-up of 17 ± 7 months, there were nine cardiac deaths and four nonfatal myocardial infarctions. Predictors of cardiac events were any abnormality on stress echocardiography, cessation of stress test, and disease of two or more coronary vessels. Camerieri and colleagues (20) evaluated 190 patients 65 years old by dipyridamole echocardiography early after an acute uncomplicated myocardial infarction. During a follow-up of 14 ± 10 months, there were 62 events including 14 cardiac deaths, 7 nonfatal myocardial infarctions, 21 cases of heart failure, and 20 revascularization procedures. Patients with a positive dipyridamole echocardiography test experienced significantly higher myocardial infarction or death (7%) compared with patients with a negative test (4%). Poldermans and colleagues (21) performed a DSE test in 179 elderly patients (mean age 75 years) referred for chest pain or preoperative risk assessment for major vascular surgery. Ischemia during the test was the only independent predictor of perioperative and cardiac events during short-term follow-up of 16 ± 6 months. Marwick and colleagues (22) studied 3156 patients (mean age 63 ± 12 years) referred for DSE for a mean follow-up of 3.8 ± 1.9 years. DSE provided independent information, incremental to clinical variables, for prediction of total and cardiac mortality. The annual hard cardiac events rate was around 2% in patients with a normal DSE and 6.3% in patients with an abnormal DSE. Age >65 years was associated with an incremental risk of mortality in patients with heart failure but a normal DSE. In particular, patients 65–75 years old had a yearly cardiac mortality of 4%, increasing to 6% yearly in patients over 75 years old.
Arruda and colleagues (8) studied 2632 patients >65 years old who underwent exercise echocardiography. During a follow-up of 2.9 ± 1.7 years, cardiac events included cardiac death in 68 patients (2%) and nonfatal myocardial infarction in 80 patients (3%). The annual hard cardiac events rate was 2.4% in patients with normal and 5.6% of patients with abnormal exercise echocardiography. Exercise echocardiographic variables provided incremental information to clinical, rest echocardiography, and exercise electrocardiogram in predicting cardiac events. In our study, the cardiac death rate was higher than that in the exercise study. This may be related to several factors such as a longer and nearly complete (99.5%) follow-up in our study. In general, patients who are able to exercise are considered a lower risk population than are patients who are unable to perform the exercise stress test. Nevertheless, the event rate was relatively lower for patients with normal DSE in our study as compared to patients with normal exercise echocardiography. In our study, 89% of elderly patients could achieve the target heart rate; this may have contributed to a better sensitivity for detecting myocardial ischemia in our study.
Limitations of the Study
The population of this study was recruited over 15 years. During the entire follow-up period, there has been substantial clinical progress in the treatment of CAD that may possibly affect the interpretation of the significance of our results. Nevertheless, survival curves for patients with normal and abnormal DSE continued to diverge during the entire follow-up, indicating that the prognostic value of DSE was maintained during follow-up. Exclusion of patients with early revascularization may have reduced the predictive power of an abnormal DSE. This is, however, an inherent limitation of most prognostic studies that used similar approaches (13).
Clinical Implications and Conclusions
DSE provides independent prognostic information for the prediction of all-cause mortality and hard cardiac events in elderly persons. Dobutamine-induced wall motion abnormalities are independently associated with adverse outcomes, particularly in patients with resting left ventricular dysfunction. Patients with a normal DSE have a low cardiac event rate and can be exempted from further noninvasive testing if they have a stable clinical course during the 5 years following DSE.
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Footnotes
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Decision Editor: John E. Morley, MB, BCh
Received June 29, 2004
Accepted September 17, 2004
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Abstract
Methods
