The dobutamine stress test as an alternative to exercise testing after acute myocardial infarction

Effects of dobutamine and arbutamine on regional myocardial function in a porcine model of myocardial ischemia

OBJECTIVES

The present study was performed to determine the mechanisms for catecholamine-induced wall motion abnormalities and to compare the diagnostic efficacy of two catecholamines: arbutamine and dobutamine.

BACKGROUND

Catecholamine stress echocardiography is used to induce regional wall motion abnormalities for the detection of coronary artery disease, but the mechanism by which these abnormalities occur is unknown.

METHODS

Ten pigs were instrumented with left circumflex coronary artery ameroid constrictors, sonomicrometers to measure transmural wall thickening in the left circumflex (ischemic) and left anterior descending (control) coronary artery beds and a pressure gauge to measure left ventricular pressure and its first derivative (dP/dt). Myocardial blood flow was measured by microspheres.

RESULTS

At 38 +/- 6 days (mean +/- SEM) after surgery, percent wall thickening was normal at rest in both beds but abnormal in the left circumflex coronary artery bed during atrial pacing. These findings were associated with reduced myocardial blood flow in the ischemic bed during atrial pacing. Dobutamine infusion increased percent wall thickening, with no differences between the two beds (p = 0.63). In contrast, arbutamine infusion increased percent wall thickening only in the nonischemic bed, with no effect on percent wall thickening in the ischemic bed (p = 0.03). Although the endocardial/epicardial blood flow ratio tended to be reduced in the left circumflex artery bed during catecholamine infusion (p = 0.07), both agents were similar in this effect. Despite differences in function between the beds, there was no difference in transmural myocardial blood flow between the two beds during catecholamine infusion. When examined at matched metabolic demands, arbutamine elicited greater differences in percent wall thickening than dobutamine between the two beds (p < 0.01).

CONCLUSIONS

Arbutamine was able to provoke regional differences in function in a manner superior to dobutamine. This occurred independently of altered transmural myocardial blood flow or differences in hemodynamic effects between the agents. Differences in their inotropic properties may be important in explaining their different effects on ischemic myocardium.

Dipyridamole is superior to dobutamine for thallium stress imaging: a randomised crossover study

OBJECTIVE

To assess the value of dobutamine over dipyridamole as a pharmacological stressing agent in myocardial perfusion imaging with thallium-201.

DESIGN

Stress and redistribution tomographic images were taken in a group of patients in a randomised crossover study of both agents. The scans were scored to give a value for the stress and redistribution images and a reversibility score (redistribution--stress). All patients had coronary angiography that was also scored. Differences between the two agents were compared by a paired t test.

PATIENTS

30 patients aged 51-70 years with chest pain thought to be caused by myocardial ischaemia. 11 had had previously myocardial infarction.

RESULTS

Dipyridamole caused adverse symptoms in six patients whereas dobutamine caused symptoms in 21 patients (chi 2 = 15.15, p < 0.0001). Dobutamine stress took considerably longer than dipyridamole (31 v 6 minutes) and cost more (17 pounds v 1.50 pounds). There were no significant differences between the agents in terms of total stress or redistribution scores, but regional analysis showed that dipyridamole showed significantly more defects during stress at the apex and lateral wall (p < 0.05), with no significant difference at redistribution. Dipyridamole stress also caused significantly more reversible defects at the apex (p < 0.05) and gave a better correlation than dobutamine with coronary score (dipyridamole r = 0.80, p < 0.001 v dobutamine r = 0.64, p < 0.001). In six patients who had continued to take beta blockers the results of dobutamine stress did not correlate with coronary score, r = 0.34 (NS), whereas dipyridamole studies were not affected.

CONCLUSION

Compared with dobutamine, dipyridamole was as effective in producing overall perfusion defects and more effective in provoking defects at the apex and lateral segment. The dipyridamole study correlated better with coronary score and was not affected by concurrent beta blocker treatment. It was also better tolerated by the patients, was less time consuming, and was much cheaper.

Predictive value of dobutamine echocardiography just before noncardiac vascular surgery

This study prospectively evaluated 75 consecutive patients (mean age 69 +/- 9 years) undergoing major vascular surgery to test the hypothesis that dobutamine stress echocardiography can be used to predict perioperative cardiac events. A positive test was defined as a new or worsening wall motion abnormality in at least 2 of 18 wall segments. Up to 40 micrograms/kg/min of dobutamine was administered. All readings were done by physicians unaware of the patients' symptoms and electrocardiographic response. In addition, physicians caring for the patients were unaware of the test result. End points of the study were unstable angina with documented electrocardiographic changes, nonfatal myocardial infarction or cardiac death. The perioperative ischemic event rate was 7% (5 of 75 patients). Three patients developed unstable angina and 2 sustained nonfatal myocardial infarctions. All of these patients had positive results on dobutamine stress echocardiography (sensitivity 100%). However, 22 patients who also had positive results on dobutamine stress echocardiography did not have perioperative events (specificity 69%). The corresponding positive predictive value was 19%. None of the 48 patients who had negative results on dobutamine stress echocardiography had events (negative predictive value 100%). In conclusion, dobutamine stress echocardiography can be used to predict perioperative events with great sensitivity, but its positive predictive value in this patient population in low, likely due to the low incidence of perioperative events in patients with known coronary artery disease and the imperfect specificity of dobutamine stress echocardiography in identifying significant coronary stenosis. Dobutamine stress echocardiography is most useful in this setting when negative, because it predicts safety from complications with confidence.

Comparative evaluation of bicycle and dobutamine stress echocardiography with perfusion scintigraphy and bicycle electrocardiogram for identification of coronary artery disease

In 66 patients with suspected coronary artery disease (CAD), exercise electrocardiography (ECG), exercise echocardiography, dobutamine stress echocardiography (dosage, 5 to 40 micrograms/kg/min), single-photon emission computed tomography (SPECT) using methoxy-isobutyl-isonitrile (MIBI) and coronary angiography were performed prospectively to compare methods for detecting CAD. CAD was defined as 70% luminal area stenosis in at least 1 coronary artery at coronary angiography. Significant CAD was present in 50 patients. Compared with exercise ECG, exercise echocardiography, dobutamine stress echocardiography and MIBI-SPECT had a significantly higher sensitivity (52% vs 80, 79 and 89%; p < 0.01, p < 0.01 and p < 0.001, respectively). There were no significant differences in sensitivity between exercise echocardiography, dobutamine stress echocardiography and MIBI-SPECT. Specificity of MIBI-SPECT was lowest (71%), whereas exercise ECG, exercise and dobutamine echocardiography had higher specificities (93, 87 and 81%, respectively). Significance, however, was not achieved. Differences in overall accuracy between exercise echocardiography (82%), dobutamine stress echocardiography (80%) and MIBI-SPECT (85%) were not significant. Comparison with accuracy of exercise ECG (62%) was significant (p < 0.05, p < 0.05 and p < 0.01, respectively). In 1-vessel disease, exercise ECG had a lower sensitivity (45%) than exercise and dobutamine echocardiography and MIBI-SPECT (79, 78 and 84%; p < 0.02, p < 0.02 and p < 0.01, respectively). Regarding the 24 patients with false-negative exercise ECG results, 67% had positive exercise echocardiography findings, 71% positive dobutamine echocardiography results and 84% positive technetium-99m MIBI-SPECT results.(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine stress magnetic resonance imaging for detection of coronary artery disease

OBJECTIVES

The clinical value of cine magnetic resonance imaging (MRI) during dobutamine stress for detection of coronary artery disease was evaluated in 45 patients with chest pain who were admitted for coronary arteriography.

BACKGROUND

Development of stress-induced wall motion asynergy is considered an early and reliable sign of myocardial ischemia preceding electrocardiographic (ECG) changes and angina. As physical exercise during MRI is difficult because of motion artifacts and space restriction, dobutamine infusion was used to induce cardiovascular stress.

METHODS

Cine MRI tomograms were obtained in six adjacent short-axis planes. After baseline acquisition, dobutamine was administered to a maximal dose of 20 micrograms/kg per min. Both at rest and during peak dobutamine stress, magnetic resonance images were displayed in a cinematographic loop to assess regional wall motion qualitatively. Results of dobutamine MRI were considered positive for coronary artery disease if any new or worsening wall motion abnormality developed. Immediately after MRI at peak dobutamine infusion, dobutamine electrocardiography was performed outside the magnetic environment. In addition, all patients performed symptom-limited exercise electrocardiography.

RESULTS

Significant coronary artery disease (> 50% diameter stenosis) was present in 37 patients. During peak dobutamine stress, wall motion asynergy developed or worsened in 30 patients, yielding an overall sensitivity for detection of coronary artery disease of 81% and a specificity of 100%. Corresponding data were 51% and 63% for dobutamine electrocardiography and 70% and 63% for exercise electrocardiography. The sensitivity of dobutamine MRI for the detection of coronary artery disease in patients with single-, double- and triple-vessel disease was 75% (15 of 20 patients), 80% (8 of 10) and 100% (7 of 7), respectively.

CONCLUSION

Dobutamine MRI is an accurate nonexercise-dependent method for the assessment of myocardial ischemia in patients with coronary artery disease.

Assessment of thallium scintigraphy and echocardiography during dobutamine infusion for the detection of coronary artery disease

Dobutamine infusion was performed in 16 patients following cardiac catheterization, and non-invasive assessment was performed with thallium SPECT and echocardiography. Dobutamine thallium scintigraphy was abnormal in 93% of patients with significant coronary artery disease. In addition, individual epicardial vessel involvement was identified by a corresponding perfusion defect with 88% sensitivity and 93% specificity. Dobutamine echocardiography revealed segmental wall motion abnormalities in 62% of patients with significant coronary disease. However, in six patients baseline segmental wall motion abnormalities on echocardiography improved during dobutamine infusion. Dobutamine thallium SPECT is a safe and useful test for the detection and localization of coronary artery disease. Dobutamine echocardiography is less useful in screening for coronary disease, but may detect areas of abnormally functioning myocardium having retained viability.

Dobutamine stress echocardiography: prevalence of a nonischemic response in a low-risk population

The problems of population referral bias in the calculation of specificity in diagnostic testing for coronary artery disease have been previously described. Previous studies investigating the sensitivity and specificity of dobutamine stress echocardiography (DSE) have been subject to pretest and posttest referral biases, largely as a result of the requirement for coronary arteriography. This study determines the normalcy rate for DSE by examining a population at statistically low risk for coronary artery disease. The probability of significant coronary artery disease was determined for 828 consecutive patients referred for DSE at the University of Michigan, and groups were identified with < 10% and < 5% probability of disease. Four of 72 patients (5.6%) with a normal baseline echocardiogram and a probability of coronary artery disease of < 10%, and three of 38 (7.9%) with a probability of < 5% were found to have an abnormal DSE, yielding normalcy rates of 94.4% and 92.1%, respectively. The area of abnormality involved the posterior circulation in three of four patients (75%). This study demonstrates that DSE has a normalcy rate of 92% to 94% and is an accurate test for excluding the presence of significant coronary artery disease.

A comparison of dobutamine and maximal exercise as stress for thallium scintigraphy

In the assessment and evaluation of patients with suspected coronary artery disease there is a need for pharmacological stress combined with thallium scintigraphy. Thallium images were obtained following stress both with dobutamine infusion (5-20 micrograms kg-1 min-1) and with symptom-limited bicycle ergometry in 20 patients (age 39-70 years) with chest pain who had been admitted for coronary angiography. Percentage thallium uptake was calculated using a region of interest technique. Detailed comparison was performed of the presence, size and distribution of left ventricular thallium perfusion defects; the percentage thallium uptake in ventricles, lung and liver; and the haemodynamic response to stress. Each stress produced a similar number of abnormal segments in each of three views (total EX 166/300; DOB 167/295), but exercise produced larger defects in the anterior view (P < 0.025). Thallium uptake in left and right ventricles and relative uptake to lungs were similar, but dobutamine produced higher relative liver uptake [EX 1.55 (0.67); DOB 2.97 (1.23) P < 0.0001]. Fourteen patients were able to tolerate dobutamine 20 micrograms kg-1 min-1. The ratio of peak stress to rest double product was smaller with dobutamine in both patients with (DOB 1.3; EX 2.0; P < 0.0047) and patients without beta-blockade (DOB 1.5; EX 2.4; P < 0.008). Dobutamine produced fewer conventional stress endpoints of chest pain and ST depression. In conclusion, dobutamine produces a well-tolerated incremental pharmacological stress with thallium images similar to maximal exercise, and provides a useful alternative stress in patients unable to perform adequate dynamic exercise.

Dobutamine stress echocardiography predicts surgical outcome in patients with an aortic aneurysm and peripheral vascular disease

OBJECTIVES

This study was conducted to assess the utility of dobutamine stress echocardiography for determining the presence of significant coronary artery disease and for predicting surgical outcome and long-term prognosis in patients scheduled to undergo peripheral vascular or aortic aneurysm surgery.

BACKGROUND

Assessment of coronary artery disease in patients scheduled to undergo peripheral vascular surgery can avoid perioperative complications.

METHODS

Dobutamine stress echocardiography was performed in 98 consecutive patients scheduled to undergo aortic or peripheral vascular surgery. Intravenous dobutamine was infused in a graded fashion, with two-dimensional digital echocardiographic monitoring of ventricular function and segmental wall motion. Group 1 (n = 70) consisted of patients who exhibited a normal response to dobutamine infusion (negative dobutamine study); group 2 (n = 23) comprised those patients with an abnormal response to dobutamine, characterized by the development of new or worsening wall motion abnormalities at rest, indicating the presence of myocardial ischemia (positive dobutamine study). Five patients with an inconclusive dobutamine study (because of inadequate heart rate) were excluded from analysis.

RESULTS

No major adverse effects occurred with testing in any patient. Sixty-eight of 70 patients with a negative study had peripheral vascular or aortic surgery performed without perioperative cardiac events (2 patients refused surgery). Nineteen of 23 patients with a positive study underwent coronary angiography and all had > 50% lumen narrowing in one or more major coronary artery distributions; 13 underwent coronary artery bypass grafting or angioplasty before peripheral vascular or aortic surgery and all had an uneventful perioperative period. Four of the 10 patients from group 2 who did not undergo coronary revascularization had a perioperative cardiac event (myocardial infarction in 2, an ischemic episode requiring urgent coronary bypass grafting in 1 and congestive heart failure in 1).

CONCLUSIONS

Positive and negative dobutamine study results are significant predictors of the presence or absence of perioperative events (20% vs. 0%, p = 0.003). A positive test warrants coronary angiography and further medical or surgical intervention, or both, but a negative test indicates a low likelihood of perioperative cardiac complications of aortic or peripheral vascular surgery. During the long-term follow-up period in this study (group 1 mean, 24 months; group 2 mean, 15 months), two patients (3%) from group 1 and three (15%) from group 2 developed cardiac complications (p = 0.038). Thus, dobutamine stress echocardiography is safe and can predict surgical outcome in patients undergoing aortic aneurysm repair or surgery for occlusive disease of the peripheral arteries. In addition, a negative test result is a strong predictor of decreased perioperative and long-term cardiac morbidity and mortality.

Ischemia-induced regional wall motion abnormality is improved after coronary angioplasty: demonstration by dobutamine stress echocardiography

OBJECTIVES

The purpose of this study was to examine whether dobutamine stress echocardiography can detect reversal of ischemia-induced left ventricular regional wall motion abnormality immediately after percutaneous transluminal coronary angioplasty.

BACKGROUND

Although angioplasty is routinely performed as a means of coronary revascularization, at present there is a question whether this results in an immediate improvement in ischemia-induced left ventricular regional function.

METHODS

Thirty-five patients underwent dobutamine stress echocardiography 24 h before and 24 to 48 h after angiographically successful coronary angioplasty. Only patients with normal wall motion at rest were included. Dobutamine infusion was begun at 5 micrograms/kg per min and increased at 5-min intervals (10, 20, 30, 40 micrograms/kg per min). Echocardiographic images were stored into cine loops and analyzed off line with simultaneous comparison of images acquired at baseline, 5 micrograms/kg per min, peak infusion and recovery. Echocardiographic images were interpreted independently, without knowledge of other data, by two experienced cardiologists using the 16-myocardial segment model.

RESULTS

Before angioplasty, dobutamine stress echocardiography induced wall motion abnormalities in 31 patients (88%). Wall motion score at peak dobutamine infusion improved in 28 (90%) of the 31 patients after angioplasty. Wall motion score at peak dobutamine infusion for the group improved from 20 +/- 3 before angioplasty to 17 +/- 2 after angioplasty (p < 0.001). There was no change in the rate-pressure product achieved for the group before and after angioplasty (20,038 +/- 6,415 beats/min x mm Hg before versus 20,775 +/- 5,435 after angioplasty, p = NS). Before angioplasty, dobutamine stress echocardiography induced angina in 13 patients (37%), whereas angina occurred only once after angioplasty. Electrocardiographic changes diagnostic of ischemia occurred seven times, all before angioplasty.

CONCLUSIONS

We conclude that dobutamine stress echocardiography is an excellent method to demonstrate an immediate improvement in stress-induced regional left ventricular dysfunction in the distribution of the vessel undergoing successful angioplasty.

Prognostic value of dobutamine echocardiography in patients with high pretest likelihood of coronary artery disease

To examine the value of transient regional asynergy on dobutamine stress echocardiography as a noninvasive predictor of future cardiac events, 51 symptomatic patients (aged 54 +/- 9 years) with suspected coronary artery disease (CAD) were studied using an incremental regimen of 5, 10, 15 and 20 micrograms/kg/min. Pretest likelihood of CAD was (mean +/- standard error of the percentage) 79.7 +/- 5.6% before and 83.4 +/- 5.2% after exercise electrocardiography using probability analysis based on age, sex and symptoms. Two-dimensional images were analyzed with reference to an 11-segment model and gave good interrater agreement. During 24 +/- 4 months (range 19 to 32) of follow-up, 23 patients had events (1 myocardial infarction, 9 unstable angina, 10 coronary bypass surgery, 3 coronary angioplasty) and 28 were event free. Age, proportion with baseline asynergy and both pretest echocardiographic ejection fraction and its response to dobutamine were similar in these 2 groups (all p = not significant). Transient asynergy was seen in 17 of 23 patients (74%) with and 8 of 28 patients (29%) without events (p < 0.01); 5 of 6 patients (83%) with involvement of 3 segments had events. Myocardial infarction or unstable angina occurred in 8 of 25 (32%) with a positive and 2 of 26 (8%) with a negative stress echocardiogram (p < 0.05). Both exercise duration (389 +/- 195 vs 517 +/- 237 seconds, p < 0.05) and time to diagnostic ST-segment shift (291 +/- 192 vs 447 +/- 212 seconds, p = 0.05) were shorter in those with inducible asynergy.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of exercise electrocardiography and dobutamine echocardiography

It is uncertain whether dobutamine echocardiography is a better test than exercise electrocardiography for the detection of coronary disease in patients who can exercise. We compared the hemodynamics, sensitivity, and specificity of these tests in 24 patients, 16 with coronary disease and 8 controls. The tests were performed within six weeks of one another and were interpreted without knowledge of other clinical data. The exercise electrocardiogram was considered abnormal if the patient developed one mm of ST-segment depression, while the dobutamine test (up to 40 micrograms/kg/min) was considered abnormal if the patient developed ST-segment depression or a left ventricular wall motion abnormality. Exercise testing resulted in a higher heart rate (145 +/- 29 vs. 110 +/- 24, p less than 0.001) and blood pressure (176 +/- 31 vs. 148 +/- 24, p less than 0.001). Dobutamine testing was 25% more sensitive than exercise testing (94 vs. 69%, 95% confidence interval for difference is 0 to 50%, p = 0.09), while exercise testing was 38% more specific (88 vs. 50%, 95% confidence interval for difference is -3 to 79%, p = 0.14). We conclude that exercise results in a higher heart rate and blood pressure than dobutamine infusion. Differences in sensitivity and specificity are inconclusive, but indicate that the sensitivity of exercise testing is, at best, equivalent to dobutamine testing, while any increase in specificity with dobutamine testing, compared with exercise testing, would not be clinically significant.

New developments in pharmacologic stress imaging

The clinical usefulness of cardiac imaging modalities that rely upon the detection of perfusion defects and wall motion disturbances requires conditions that provoke a heterogeneity of coronary flow and a myocardial oxygen imbalance, respectively. Traditionally, this has been achieved by exercise stress testing. Many patients cannot perform dynamic exercise sufficiently for various reasons. Pharmacologic stress has been proven to be an attractive alternative for physical exercise. Currently, several stressing agents are used in conjunction with thallium-201 scintigraphy, 2-D echocardiography and, recently, MRI. The most employed agents include vasodilators, such as dipyridamole and adenosine, and catecholamines, such as dobutamine (Table VI). The predominant rationale of thallium-201 perfusion scintigraphy is based on the creation of a flow maldistribution between territories supplied by normal arteries and those supplied by stenotic arteries that does not necessarily require ischemia. Dipyridamole and adenosine, as rather selective coronary vasodilators, are well suited to provoke such a condition and may be classified as the ideal markers of myocardial perfusion. 2-D echocardiography and MRI have the potential to provide noninvasively derived information of cardiac dynamics and regional myocardial function. To assess the functional significance of coronary artery disease, detection of wall motion abnormalities and alterations in ejection fraction require the presence of myocardial ischemia. Dobutamine, as a widely applied inotropic agent in the management of severely depressed left ventricular contractile function, seems to be an appropriate pharmacologic stressor when heart failure is absent. By increasing contractility, heart rate, and systolic arterial pressure, it is capable of inducing an imbalance between myocardial oxygen demand and supply, leading to ischemia in patients with coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced sensitivity for detection of coronary artery disease by addition of atropine to dobutamine stress echocardiography

Patients undergoing dobutamine stress echocardiography often take beta antagonists which limit heart rate response and sensitivity in the test for detection of coronary artery disease. The aim of this study was to assess the effect of the addition of atropine to dobutamine stress echocardiography on clinical, electrocardiographic and echocardiographic outcomes. Dobutamine stress echocardiography was performed starting at and increasing every 3 minutes with 10 micrograms/kg/min to a maximum of 40 micrograms/kg/min (stage 4), which was continued for 6 minutes. In patients not achieving 85% predicted maximal exercise heart rate and in whom the test was not judged positive on echocardiographic or electrocardiographic criteria, atropine (0.25 mg intravenously, repeated up to a maximum of 1 mg if necessary) was added and dobutamine continued for up to a further 5 minutes, or until an adequate heart rate was achieved or the test was stopped because of chest pain or electrocardiographic changes. Of 80 consecutive patients undergoing dobutamine stress echocardiography within 2 weeks of coronary angiography, 49 required atropine (group A) and 31 required only dobutamine (group B). After dobutamine alone, heart rate (mean +/- SD) was higher in group B than in group A: 129 +/- 20 vs 90 +/- 18 beats/min, p less than 0.0001; but after the addition of atropine, heart rate in group A increased to 120 +/- 20 beats/min. Overall sensitivity for the detection of coronary disease was 70%, 95% confidence interval (CI) 55 to 83%; after the addition of atropine, sensitivity for group A was 65%, 95% CI 45 to 81%; in group B, sensitivity was 81%, 95% CI 54 to 96%.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance imaging during dobutamine stress in coronary artery disease

Cine magnetic resonance imaging (MRI) provides a tomographic method of assessing regional ventricular function in any desired plane. It has not been possible to obtain adequate images during dynamic exercise, and this has limited its value in patients with coronary artery disease (CAD). Therefore, an infusion of dobutamine was used to study 25 patients with exertional chest pain and abnormal exercise electrocardiograms. Areas of abnormal wall motion were compared with areas of abnormal myocardial perfusion imaged by dobutamine thallium emission tomography and with coronary arteriography. Twenty-two patients had significant CAD. Twenty-one (96%) of these patients had reversible myocardial ischemia shown by dobutamine thallium tomography, and 20 (91%) had reversible wall motion abnormalities shown by dobutamine MRI. Comparison of abnormal segments of perfusion and wall motion showed 96% agreement at rest, 90% agreement during stress, and 91% agreement for the assessment of functional reversibility. The normalized magnetic resonance signal intensity of the ischemic segments showed a small but significant reduction when compared with that of normal segments (-67 units [9.2%]; p less than 0.05). Dobutamine infusion was well-tolerated, despite causing chest discomfort in 24 patients (96%). Nine patients (36%) developed a minor dysrhythmia that was usually ventricular premature complexes, but this did not limit infusion, and other side effects were mild. The short plasma half-life of dobutamine makes it ideal as a stress agent for imaging techniques (such as MRI), and these results suggest that it is more effective in the provocation of wall motion abnormalities than is dipyridamole in patients with CAD.

Dobutamine stress echocardiography

Two-dimensional echocardiography is a versatile, accurate, and readily available method for the assessment of cardiac anatomy and function, and extensive experience has been gained in the analysis of left ventricular wall motion. Using modern imaging techniques, regional as well as global wall motion analysis can be performed. Echocardiography can be used in conjunction with a protocol for either exercise or pharmacologic cardiovascular stress in order to identify the distribution and severity of coronary artery disease, with the induction of a regional wall motion abnormality being a sign of myocardial ischemia. The use of dobutamine infusion to accomplish stress echocardiography is a safe, accurate, and practical method for the diagnosis of coronary artery disease in patients unable to exercise. In addition to the evaluation of inducible ischemia, preliminary work is being performed with dobutamine stress echocardiography for the assessment of risk and patient prognosis following acute myocardial infarction and as an indication of tissue viability for myocardium that remains dysfunctional at rest following thrombolytic therapy.

Accuracy of dobutamine stress echocardiography in detecting coronary artery disease

The diagnostic accuracy of dobutamine stress echocardiography (DSE) (incremental infused doses of 5, 10, 20 and 30 micrograms/kg/min) was evaluated in 141 patients who underwent coronary arteriography within 2 weeks of DSE. All patients were being evaluated for known or suspected coronary artery disease (CAD). DSE was interpreted blindly as normal or showing evidence of CAD, depending on the presence of resting or inducible wall motion abnormalities. Coronary arteriograms were reviewed in a blinded, quantitative fashion. DSE had a sensitivity of 96% for detecting patients with CAD, and a specificity of 66%. For the 53 patients with normal resting wall motion, sensitivity was 87% and specificity 91%. The protocol was well-tolerated by all patients. In comparison with wall motion analysis, 12-lead electrocardiograms during dobutamine infusion revealed ischemic changes in only 17% of patients with CAD. It is concluded that DSE is a clinically useful and accurate means for detecting CAD, its specificity is hindered in patients with resting wall motion abnormalities, and it can safely be used in patients with known cardiac disease.

Dobutamine stress echocardiography for detection and assessment of coronary artery disease

Stress echocardiography with dobutamine infusion for detection of coronary artery disease is a potential alternative to exercise stress testing with some theoretic advantages. Fifty patients who were not receiving cardioactive medication were prospectively studied with two-dimensional echocardiography and 12-lead electrocardiography (ECG) during incremental dobutamine infusion (5, 10, 15 and 20 micrograms/kg body weight per min, each dose for 8 min). Images were analyzed by using an 11-segment left ventricular model. All patients underwent correlative exercise ECG and coronary angiography, which revealed normal coronary arteries in 14 and significant disease (greater than or equal to 70% diameter stenosis) in 36. Peak rate-pressure product during dobutamine infusion was 18,845 +/- 4,156 versus 23,740 +/- 6,158 mm Hg/min on exercise (p less than 0.01). Interobserver concordance for wall motion analysis was good (kappa coefficient = 0.77). The use of baseline (n = 14) or reversible (n = 24) regional asynergy to define an abnormal dobutamine echocardiogram resulted in a sensitivity for detecting coronary artery disease of 78% and a specificity of 93%. Corresponding data for the dobutamine ECG were 47% and 71% and for the exercise ECG were 72% and 71%, respectively. The development of new mitral regurgitation on Doppler color flow imaging (n = 4) improved sensitivity to 81% without loss of specificity. Inducible asynergy or new mitral regurgitation was observed in 6 (50%) of 12 patients with single-, 6 (60%) of 10 with double- and 12 (86%) of 14 with triple-vessel disease. The site of transient asynergy provided additional localizing information. Exercise duration and time to diagnostic ST segment shift were shorter in patients with coronary artery disease with versus those without echocardiographic evidence of ischemia (both p less than 0.05). Side effects during dobutamine infusion were mild and short-lived. Dobutamine stress echocardiography is well tolerated, is useful for detection and assessment of coronary artery disease and is applicable to patients unable to exercise.

Dobutamine stress echocardiography: correlation with coronary lesion severity as determined by quantitative angiography

This study was performed 1) to determine the ability of dobutamine stress echocardiography to detect stenoses in individual coronary arteries by utilizing a new model of coronary artery distribution; 2) to evaluate its ability to detect coronary artery stenosis with a minimal lumen diameter less than 1 mm; and 3) to correlate the heart rate at which a positive test result occurs with the severity of coronary artery disease. Eighty-five patients were identified who underwent both dobutamine stress echocardiography and quantitative coronary angiography. During incremental infusion of dobutamine, two-dimensional echocardiograms were obtained at rest, during low and peak stress and after stress. Echocardiograms were interpreted with use of a modified 16-segment model with an anteroinferior overlap scheme. The overall sensitivity of the technique for the detection of significant coronary artery disease (diameter stenosis greater than or equal to 50%) was 95%; specificity was 82% and accuracy 92%. The sensitivity for detection of individual coronary artery lesions did not differ significantly (p greater than 0.05) in the three major coronary artery distributions (79% left anterior descending, 70% left circumflex, 77% right coronary artery). Among 35 stenoses with a minimal lumen diameter less than 1 mm, the test result was positive in 30 (86%). Test results were correctly positive for 88%, 82% and 86% of stenoses in the left anterior descending, left circumflex and right coronary artery distributions, respectively. Multivessel disease was present in 11 of 16 patients with normal wall motion at rest who developed a wall motion abnormality at a heart rate less than 125 beats/min. The incidence of multivessel disease was statistically higher in patients with positive findings on a dobutamine stress echocardiogram at a heart rate less than or equal to 125/min. In conclusion, dobutamine stress echocardiography has high sensitivity and specificity for the detection and localization of coronary artery disease. Detection of stenosis in individual coronary arteries is improved in those lesions with a minimal lumen diameter less than 1 mm. Patients with a positive test result at a heart rate less than or equal to 125 beats/min have a high likelihood of multivessel coronary artery disease.

A comparison of dobutamine infusion and exercise during radionuclide ventriculography in the evaluation of coronary arterial disease

Twenty-six patients with "chest pain" syndrome were subjected to radionuclide ventriculography during exercise and dobutamine infusion. All 10 patients with normal coronaries were identified correctly by normal ventriculographic responses to both tests. Of 16 patients with significant coronary arterial disease, dobutamine stress identified 15 patients correctly, whereas only 12 of these had an abnormal exercise response. Three patients with one-vessel disease with a normal exercise response had an abnormal dobutamine stress response. Dobutamine radionuclide stress testing is an acceptable alternative to exercise testing in patients who cannot exercise and its incremental diagnostic yield in patients with one-vessel disease requires further evaluation.

Transesophageal dipyridamole echocardiography for diagnosis of coronary artery disease

The value of transthoracic dipyridamole echocardiography has been extensively documented. However, in some patients, because of a poor acoustic window, the rest transthoracic examination is not always feasible and the transesophageal approach is more convenient. Therefore, transesophageal echocardiography with high dose dipyridamole (up to 0.84 mg/kg body weight over 10 min) was performed in 32 patients in whom the transthoracic dipyridamole test either was not feasible (n = 29) or yielded ambiguous results (n = 3). The transesophageal echocardiographic test results were considered abnormal when new dipyridamole-induced regional wall motion abnormalities were observed. All 32 patients underwent coronary angiography; significant coronary artery disease was defined as greater than or equal to 70% lumen diameter narrowing in at least one major vessel. All patients also performed a bicycle exercise test 1 day before transesophageal dipyridamole echocardiography. Transesophageal stress studies were completed in all patients, with a maximal imaging time (in tests with a negative result) of 20 min. No side effects or intolerance to drug or transducer was observed. The left ventricle was always visualized in the four-chamber and transgastric short-axis views. High quality two-dimensional echocardiographic images were obtained in all patients both at rest and at peak dipyridamole infusion and were digitally analyzed in a quad-screen format. Coronary angiography showed coronary artery obstruction in 24 patients: 6 had single-, 9 double- and 9 triple-vessel disease. The transesophageal dipyridamole test showed a specificity of 100% and an overall sensitivity of 92%. The sensitivity of this test for single-, double- and triple-vessel disease was 67%, 100% and 100%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamine stress echocardiography

Two-dimensional echocardiographic monitoring during catecholamine infusion has shown promise as a safe and accurate method for detection of coronary artery disease. The clinical application of catecholamine stress echocardiography has been facilitated by the development of digital image processing techniques. The sensitivity of this method of stress testing has been improved by drug infusion protocols that are designed to maximize myocardial stress. Recent investigations have demonstrated the value of dobutamine stress echocardiography for detection of multivessel disease following myocardial infarction and for assessment of cardiac risk before noncardiac surgery. Evaluation of changes in wall motion and thickening that occur during low dose dobutamine infusion may enable detection of viable myocardium after thrombolytic treatment of acute myocardial infarction. Compared to alternative noninvasive diagnostic methods, catecholamine stress echocardiography permits continuous acquisition of high-quality information on regional and global systolic function. This and other advantages have prompted the search for broader applications of this technique.

Stress-induced ST segment shift in leads V3R and V4R after acute myocardial infarction

A total of 107 patients with acute myocardial infarction underwent a dobutamine stress test and received increasing doses of the drug (5, 10, 15, 20, and up to 40 micrograms/kg/min). Coronary angiography was performed within the first month. The 12 conventional ECG leads plus the right chest leads V3R and V4R were recorded under basal conditions and after each dose of dobutamine. In 51 patients (group A) there was an ST shift greater than or equal to 0.5 mm in the right chest leads, with two different patterns: rightward (V2 less than V1 less than V3R V less than V4R) (n = 26) and leftward (V2 less than V1 less than V3R greater than V4R) (n = 25). In 56 patients (group B) no ST shift in the right chest leads was induced. An ST segment elevation greater than or equal to 0.5 mm in V4R was 43% sensitive and 86% specific for the detection of proximal right coronary artery disease. Four subgroups were established in group A: A1R, rightward ST elevation (n = 23); A1L, leftward ST elevation (n = 12); A2R, rightward ST depression (n = 3); and A2L, leftward ST depression (n = 13). Group A1R had predominantly inferior infarcts and right coronary artery stenoses, group A1L had predominantly anterior infarcts and left anterior descending coronary stenoses, and group A2L had posteroinferior infarcts and right or left circumflex stenoses, all of them with low sensitivity (less than 50%) and high specificity (greater than 87%) for a such diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypotension during dobutamine stress echocardiography: initial description and clinical relevance

Hypotension during exercise treadmill testing is correlated with the presence of coronary artery disease, its severity, and prognosis. The importance of hypotension during dobutamine stress testing has not been previously reported to our knowledge. We reviewed 43 cases of hypotension occurring in 42 patients out of a total of 116 consecutive stress dobutamine echocardiographic procedures performed in a total of 112 patients. Of the 42 patients with hypotension, 20 underwent cardiac catheterization. Regional wall motion abnormalities induced by dobutamine infusion were found in 13 of these patients, all of whom had significant (greater than or equal to 70% diameter reduction) coronary artery disease. The remaining seven patients without regional wall motion abnormalities did not have significant coronary artery disease at catheterization. Of the remaining 22 patients with dobutamine-induced hypotension, 20 had no induced regional wall motion abnormalities, were not catheterized, and were followed clinically. None of these patients had a cardiac event during a mean follow-up period of 11.5 months. We conclude that hypotension during dobutamine stress echocardiography in the absence of regional wall motion abnormalities does not indicate significant coronary artery disease or portend an adverse prognosis.

Stress echocardiographic techniques. An overview

The choice of upright or supine exercise, pharmacological agents, or atrial pacing for the induction of ischemia depends on the goals and the imaging modality. Dynamic stress echocardiography has improved diagnostic accuracy over and above the stress electrocardiogram. Indications include patients with atypical symptoms, prior nondiagnostic stress electrocardiograms, or baseline electrocardiographic abnormalities. Pharmacological agents coupled with echocardiography do well in the high-risk preoperative patient (e.g., abdominal aneurysmectomy) or in those unable to walk due to orthopedic, neurological, or peripheral vascular disease. When there is uncertainty as to the physiological significance of anatomical (angiographic) stenosis, dynamic stress echocardiography in the ambulatory patient or atrial pacing (or beta-agonist pharmacological stressors) in the catheterization laboratory are useful. The accuracy of stress echocardiography for detection of ischemia in the follow-up of interventional procedures or for postmyocardial infarction risk stratification is superior to standard stress electrocardiography alone.

Dobutamine thallium myocardial perfusion tomography

Dobutamine has favorable properties for the pharmacologic manipulation of myocardial oxygen demand in the provocation of ischemia during the investigation of coronary artery disease. The value of dobutamine infusion for thallium myocardial perfusion tomography was assessed in 50 patients with exertional chest pain undergoing coronary arteriography. Dobutamine was infused in 5-min stages at incremental rates from 5 to 20 micrograms/kg per min or until limited by symptoms. The myocardium was divided into nine segments for analysis of perfusion. Thirty-nine of 40 patients with coronary artery disease had a reversible perfusion defect demonstrated by dobutamine thallium tomography (sensitivity 97%) and 8 of 10 patients with normal coronary arteries had normal myocardial perfusion (specificity 80%). These values were significantly better than the sensitivity and specificity of exercise electrocardiography (78% and 44%, respectively; p less than 0.01). There was a significant relation between the mean number of segments with abnormal perfusion and the number of diseased coronary vessels (0.6, 2.6, 4.4 and 6 segments in zero-, one-, two- and three-vessel disease, respectively; p less than 0.001). There was also a significant relation between the maximal tolerated dose of dobutamine and the treadmill exercise time (r = 0.56, p less than 0.001), but a wide range of exercise times was achieved in the 15- and 20-micrograms/kg per min groups, principally because of exercise limitation by noncardiac symptoms. Dobutamine infusion was well tolerated in all patients, including six with asthma. There were no significant arrhythmias or limiting symptoms other than chest pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in plasma potassium during the dobutamine stress test

We performed serial determinations of levels of potassium in 198 patients with suspected or proven coronary arterial disease who underwent a dobutamine stress test, so as to investigate if the depression in the ST segment induced by the test may be due to hypokalemia. The test consisted of an intravenous infusion of dobutamine, starting with a dose of 5 micrograms/kg/min for 5 minutes and continuing with 10, 15, 20 and up to 40 micrograms/kg/min every 5 minutes (mean peak dose = 20 micrograms/kg/min). Serial 12-lead electrocardiograms were taken to detect changes in the ST segment. The double product changed with dobutamine from 8844 +/- 6000 to 15201 +/- 3030. The peak dose of dobutamine induced a small but significant decrease in levels of serum potassium, with a further decrease 10 minutes later. In the 198 patients, the plasma potassium changes from 4.22 +/- 4.8 to 3.86 +/- 0.35 mmol/l (P less than 0.00001). The maximum decrease in potassium (0.56 +/- 0.49) occurred in the patients who received the highest dose of dobutamine (30 to 40 micrograms/kg/min). Only 17 patients reached levels lower than 3.5 mmol/l, and 4 of them achieved levels lower than 3.1 mmol/l. No correlation was found between depression of the ST segment equal to or greater than 1 mm on the electrocardiogram and the level of potassium after the test. No correlation was found between ventricular arrhythmias and levels of potassium. High doses of dobutamine, therefore, produce a small but significant decrease in potassium.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic reserve in normal myocardium assessed by positron emission tomography with C-11 palmitate

Positron emission tomography (PET) with C-11 palmitate has been used in estimating the myocardial utilization of free fatty acid. To assess the metabolic reserve in normal subjects, a PET study was performed at control and during dobutamine infusion at 2 hour intervals in 5 normal subjects. Following monoexponential curve fitting of the time activity curve of the myocardium, the clearance half time (min) and residual fraction (%) were calculated as indices of beta-oxidation of free fatty acid. A significant increase in the heart rate and systolic blood pressure were observed during dobutamine infusion (65 +/- 5 vs 100 +/- 29 bpm, p less than 0.05 and 119 +/- 12 vs 144 +/- 16 mmHg, p less than 0.01, respectively). The clearance half time and the residual fraction were significantly decreased (23.4 +/- 2.6 vs 15.8 +/- 2.3 min and 67.0 +/- 2.5 vs 58.6 +/- 4.0%, P less than 0.05, each). When the left ventricular myocardium was divided into 4 segments, these indices were similar at control and uniformly decreased without regional differences during dobutamine infusion. These data suggest that beta-oxidation of free fatty acid may be uniformly increased in the left ventricular myocardium in relation to the increase in cardiac work in normal subjects. PET with C-11 palmitate at control and during dobutamine infusion is considered to be promising in assessing metabolic reserve in the myocardium.

Dobutamine digital echocardiography for detecting coronary artery disease

To assess the value of dobutamine echocardiography for detecting coronary artery disease (CAD), 70 men (mean age 62 +/- 8 years) presenting for coronary angiography were prospectively studied. Dobutamine (2.5 to 40 micrograms/kg/min) was infused in 3-minute stages. Digital echocardiograms were recorded on-line at baseline, during low- and high-dose dobutamine infusion, and at recovery. An echocardiogram positive for CAD was defined as one showing a new wall motion abnormality induced by dobutamine. Compared with coronary angiography, the overall sensitivity of dobutamine echocardiography for detecting CAD was 86%, specificity 95% and accuracy 89%. The sensitivity for detecting 3-vessel CAD was 100%, 89% for 2-vessel and 69% for 1-vessel CAD. The accuracy of predicting multivessel disease by 2 methods was 71% and 84%, respectively. Heart rate at the echocardiographic ischemic threshold was lower in patients with 3- and 2-vessel CAD versus 1-vessel CAD (89 +/- 17, 95 +/- 18 and 118 +/- 18 beats/min, respectively, p less than 0.01); rate-pressure product was also lower in patients with 3- and 2-vessel CAD versus 1-vessel CAD (12.7 +/- 3.6, 13.7 +/- 2.8 and 18.9 +/- 44 x 10(3) beats/min x mm Hg, respectively, p less than 0.01). Heart rate was the most important physiologic determinant of ischemia induced by dobutamine. There were no major complications during the study. Thus, dobutamine digital echocardiography is an excellent test for identifying CAD and should be beneficial in patients unable to exercise.

Echocardiographic detection of coronary artery disease during dobutamine infusion

BACKGROUND

Two-dimensional echocardiography performed during dobutamine infusion has been proposed as a potentially useful method for detecting coronary artery disease. However, the safety and diagnostic value of dobutamine stress echocardiography has not been established.

METHODS AND RESULTS

In this study, echocardiograms were recorded during step-wise infusion of dobutamine to a maximum dose of 30 micrograms/kg/min in 103 patients who also underwent quantitative coronary angiography. The echocardiograms were digitally stored and displayed in a format that allowed simultaneous analysis of rest and stress images. Development of a new abnormality in regional function was used as an early end point for the dobutamine infusion. No patient had a symptomatic arrhythmia or complications from stress-induced ischemia. Significant coronary artery disease (greater than or equal to 50% diameter stenosis) was present in 35 of 55 patients who had normal echocardiograms at rest. The sensitivity and specificity of dobutamine-induced wall motion abnormalities for coronary artery disease was 89% (31 of 35) and 85% (17 of 20), respectively. The sensitivity was 81% (17 of 21) in those with one-vessel disease and 100% (14 of 14) in those with multivessel or left main disease. Forty-one of 48 patients with abnormal echocardiograms at baseline had localized rest wall motion abnormalities. Fifteen had coronary artery disease confined to regions that had abnormal rest wall motion, and 26 had disease remote from these regions. Thirteen of 15 patients (87%) without remote disease did not develop remote stress-induced abnormalities, and 21 of 26 (81%) who had remote disease developed corresponding abnormalities.

CONCLUSIONS

Echocardiography combined with dobutamine infusion is a safe and accurate method for detecting coronary artery disease and for predicting the extent of disease in those who have localized rest wall motion abnormalities.

Evaluation of coronary artery disease in the patient unable to exercise: alternatives to exercise stress testing

Exercise stress testing is a well-established method for the diagnostic, prognostic, and functional assessment of patients with known or suspected CAD. A variety of alternative tests have been described in patients unable to perform leg exercise. Atrial pacing and dipyridamole imaging have been evaluated most extensively, and results compare favorably with those of exercise testing for diagnosing the presence of CAD. Both tests may be used to assess prognosis after myocardial infarction, and dipyridamole imaging may be useful in patients undergoing preoperative evaluation. The use of the cold pressor test and isometric handgrip exercise have also been described. However, the value of both tests is limited by a relatively low sensitivity for detecting the presence of CAD. Other testing modalities--arm ergometry, intravenous infusion of beta-adrenergic agonists, and transthoracic pacing--show promise but require further assessment to confirm their value.