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

Tipping the scales of understanding: An engineering approach to design and implement whole-body cardiac electrophysiology experimental models

The study of cardiac electrophysiology is built on experimental models that span all scales, from ion channels to whole-body preparations. Novel discoveries made at each scale have contributed to our fundamental understanding of human cardiac electrophysiology, which informs clinicians as they detect, diagnose, and treat complex cardiac pathologies. This expert review describes an engineering approach to developing experimental models that is applicable across scales. The review also outlines how we applied the approach to create a set of multiscale whole-body experimental models of cardiac electrophysiology, models that are driving new insights into the response of the myocardium to acute ischemia. Specifically, we propose that researchers must address three critical requirements to develop an effective experimental model: 1) how the experimental model replicates and maintains human physiological conditions, 2) how the interventions possible with the experimental model capture human pathophysiology, and 3) what signals need to be measured, at which levels of resolution and fidelity, and what are the resulting requirements of the measurement system and the access to the organs of interest. We will discuss these requirements in the context of two examples of whole-body experimental models, a closed chest in situ model of cardiac ischemia and an isolated-heart, torso-tank preparation, both of which we have developed over decades and used to gather valuable insights from hundreds of experiments.

Let there be light! The meteoric rise of cardiac imaging

Imaging plays a central role in modern cardiovascular practice. It is a field characterised by exciting technological advances that have shaped our understanding of pathology and led to major improvements in patient diagnosis and care. The UK has played a key international role in the development of this subspecialty and is the current home to many of the leading global centres in multimodality cardiovascular imaging. In this short review, we will outline some of the key contributions of the British Cardiovascular Society and its members to this rapidly evolving field and look at how this relationship may continue to shape future cardiovascular practice.

Pharmacological and simulated exercise cardiac stress tests produce different ischemic signatures in high-resolution experimental mapping studies

OBJECTIVE

Test the hypothesis that exercise and pharmacological cardiac stressors create different electrical ischemic signatures.

INTRODUCTION

Current clinical stress tests for detecting ischemia lack sensitivity and specificity. One unexplored source of the poor detection is whether pharmacological stimulation and regulated exercise produce identical cardiac stress.

METHODS

We used a porcine model of acute myocardial ischemia in which animals were instrumented with transmural plunge-needle electrodes, an epicardial sock array, and torso arrays to simultaneously measure cardiac electrical signals within the heart wall, the epicardial surface, and the torso surface, respectively. Ischemic stress via simulated exercise and pharmacological stimulation were created with rapid electrical pacing and dobutamine infusion, respectively, and mimicked clinical stress tests of five 3-minute stages. Perfusion to the myocardium was regulated by a hydraulic occluder around the left anterior descending coronary artery. Ischemia was measured as deflections to the ST-segment on ECGs and electrograms.

RESULTS

Across eight experiments with 30 (14 simulated exercise and 16 dobutamine) ischemic interventions, the spatial correlations between exercise and pharmacological stress diverged at stage three or four during interventions (p<0.05). We found more detectable ST-segment changes on the epicardial surface during simulated exercise than with dobutamine (p<0.05). The intramyocardial ischemia formed during simulated exercise had larger ST40 potential gradient magnitudes (p<0.05).

CONCLUSION

We found significant differences on the epicardium between cardiac stress types using our experimental model, which became more pronounced at the end stages of each test. A possible mechanism for these differences was the larger ST40 potential gradient magnitudes within the myocardium during exercise. The presence of microvascular dysfunction during exercise and its absence during dobutamine stress may explain these differences.

Novel experimental model for studying the spatiotemporal electrical signature of acute myocardial ischemia: a translational platform

Myocardial ischemia is one of the most common cardiovascular pathologies and can indicate many severe and life threatening diseases. Despite these risks, current electrocardiographic detection techniques for ischemia are mediocre at best, with reported sensitivity and specificity ranging from 50%-70% and 70%-90%, respectively.

OBJECTIVE

To improve this performance, we set out to develop an experimental preparation to induce, detect, and analyze bioelectric sources of myocardial ischemia and determine how these sources reflect changes in body-surface potential measurements.

APPROACH

We designed the experimental preparation with three important characteristics: (1) enable comprehensive and simultaneous high-resolution electrical recordings within the myocardial wall, on the heart surface, and on the torso surface; (2) develop techniques to visualize these recorded electrical signals in time and space; and (3) accurately and controllably simulate ischemic stress within the heart by modulating the supply of blood, the demand for perfusion, or a combination of both.

MAIN RESULTS

To achieve these goals we designed comprehensive system that includes (1) custom electrode arrays (2) signal acquisition and multiplexing units, (3) a surgical technique to place electrical recording and myocardial ischemic control equipment, and (4) an image based modeling pipeline to acquire, process, and visualize the results. With this setup, we are uniquely able to capture simultaneously and continuously the electrical signatures of acute myocardial ischemia within the heart, on the heart surface, and on the body surface.

SIGNIFICANCE

This novel experimental preparation enables investigation of the complex and dynamic nature of acute myocardial ischemia that should lead to new, clinically translatable results.

Effect of dobutamine and hyperoxia on free radicals production in relation to the ultrastructural alterations in the endothelial of myocardial capillary in rats, Rattus norvigicus

Hyperoxia has been widely used as model for oxidative stress. Free radicals (FR), suproxide anion (*O(-)(2)) and nitric oxide anion (*NO(-)), are highly toxic and have detrimental effects on nitroso-redox balance in the myocyte. Myocardium is rich with beta-adrenergic receptors and endothelial is the site of NO production. The authors hypothesized that graded doses of dobutamine result in hyperkinetic state, which shifts the nitroso-redox balance toward the buildup of reactive species in dose-dependent excess. The purpose of the present study was to investigate free radicals production and coronary endothelial cell pathological changes following increasing length of breathing oxygen (100% O(2)) and progressive doses of dobutamine. Thirty-five adult male rats, matched with age and body weight, were randomly assigned to 7 groups. The first group served as control (C) and the 2nd, 3rd, and 4th groups were exposed to hyperoxia (100% O(2) breathing) for 24,48, and 72 h, whereas the 5th, 6th, and 7th groups were injected dobutamine 10,20, and 30 microg kg(-1), respectively. Following the treatment condition for each group, animals were sacrificed and heart tissues were divided randomly into two parts. The first part was processed for the ultrastructure, using transmission electron microscope (TEM), and the second was homogenized for FR determination. TEM examination showed that O2 breathing for 24 h resulted in hypertrophy and proliferation of endothelial cells lining the coronary capillary, which was lodged by lymphoid cells. Distended and irregular contour of endothelium, enlarged nucleus, protrusion membrane, as well as pinocytotic vesicles were also observed. Free radicals (FR) production at all levels of hyperoxia exposures and dobutamine injections were significantly (p < .05) higher than control group. In addition, dobutamine induced higher relative FR production, as compared with hyperoxia, implying more severe myocyte injury. Based on the results of the present study, it can be concluded that O2 breathing for 24 h or higher resulted in variety of pathological changes of the endothelium of coronary capillary that were induced by the buildup of oxidants by-products. Because dobutamine caused relative higher in FR production levels, as compared with hyperoxia levels, throughout this implied it aggravated the myocyte capillaries' endothelium more heavily, which could have resulted in more intense ultrastructural deteriorations.

Value of echocardiography in predicting future cardiac events after acute myocardial infarction

Short- and long-term survival after acute myocardial infarction mainly depends on three factors: the amount of myocardium that had become necrotic, the area of myocardium at further risk of becoming necrotic, and the patency of the infarct-related artery. Echocardiography is a low-cost, safe, bedside, repeatable tool, particularly useful for prognostic stratification after myocardial injury. Two-dimensional echocardiography analyzes left ventricular function, the most powerful predictor of survival immediately after acute myocardial infarction. Myocardial contrast echocardiography measures the infarct size and detects viable myocardium. Stress echocardiography stratifies patients with viable myocardium and/or multivessel coronary artery disease who need further diagnostic and therapeutic interventions. Transthoracic coronary Doppler ultrasonography assesses effective recanalization and coronary flow reserve of the left anterior descending coronary artery. Further technologic advances are needed to allow direct noninvasive measurement of flow by transthoracic Doppler ultrasonography in other coronary arteries.

Use of pharmaceuticals in noninvasive cardiovascular diagnosis

A number of pharmaceuticals are employed as diagnostic agents for cardiovascular diseases. Four groups of agents are reviewed here: 1) vasoactive substances employed as adjuncts to physical maneuvers in diagnosis of structural heart disease; 2) vasodilators used to produce heterogeneity of coronary flow; 3) sympathomimetic agents simulating the effects of exercise on the heart for the purpose of detection of coronary artery stenosis; and 4) ultrasonic contrast agents used to enhance myocardial imaging for the assessment of segmental wall motion. In the first group are amyl nitrate, a vasodilator, and methoxamine and phenylephrine, both vasopressors. The vasodilators of the second group are dipyridamole and adenosine. When combined with scintigraphic perfusion imaging or with echocardiographic assessment of segmental wall motion, these agents can detect single- or multiple-vessel coronary artery disease with sensitivity and specificity comparable to submaximal exercise. They are especially useful for preoperative risk assessment before noncardiac surgery. The sympathomimetic agents of the third group, dobutamine and arbutamine, increase myocardial contractility and heart rate, and dilate the peripheral vasculature. As with the vasodilators, when combined with nuclear or echocardiographic techniques they are equivalent to exercise in detection of coronary disease. They are especially useful in patients with bronchospastic disease and for assessment of myocardial viability. Agents from groups 2 and 3 have acceptable side-effect and safety profiles. The last group reviewed includes echocardiographic contrast agents that, in this investigative setting, are employed to enhance detection of segmental wall motion when used with agents from groups 2 and 3.

Transesophageal dobutamine stress echocardiography with tissue Doppler imaging for detection and assessment of coronary artery disease

BACKGROUND

Transesophageal dobutamine stress echocardiography (T-DSE) has been shown to be a sensitive and specific technique for the detection of myocardial ischemia. A major limitation of echocardiographic study interpretation, however, is the subjective visual analysis of endocardial motion and wall thickening, which is only semiquantitative.

METHODS

To analyze whether T-DSE with the use or tissue Doppler imaging (TDI) during graded dobutamine infusion may be useful to detect and quantify stress-induced myocardial ischemia by changes in myocardial velocities, 70 patients undergoing coronary arteriography were studied with T-DSE and TDI. Midesophageal and transgastric short- and long-axis images were obtained at each level of dobutamine infusion. T-DSE was successful in 67 patients (96%). Baseline resting pulsed and color peak systolic (S) and early diastolic (E) velocities of the anterior, septal, lateral, and inferior walls were examined.

RESULTS

Pulsed and color TDI correlated well at rest and after stress. Fifteen patients had a normal response to dobutamine, and 52 patients had inducible ischemia by two-dimensional criteria. In the normal group, there was a significant dose-dependent increase in S and E velocities. Compared with those in the normal group, patients with coronary artery disease (CAD) had lower resting S and E velocities and blunted S wave increase or E wave decrease during DSE.

CONCLUSIONS

T-DSE with TDI is a feasible and accurate test for the quantitative assessment of patients with CAD who have impaired augmentation of systolic and diastolic myocardial velocities during dobutamine infusion.

Stress echocardiography in the diagnosis of coronary artery disease

Stress echocardiography (SE) is currently a widely accepted method for the diagnostic and prognostic assessment of coronary artery disease. This article reviews new concepts in SE, such as new stress techniques, new methods of endocardial border detection, strain, tissue Doppler velocities, and others. Although some of these techniques are in their infancy, we believe that they will become widely accepted.

Diagnostic criteria for detection of postinfarction ischemia by quantitative analysis of stepwise dobutamine radionuclide ventriculography

BACKGROUND

Application of the traditional diagnostic criteria validated for exercise testing may be inappropriate when dobutamine infusion is associated with radionuclide ventriculography (RNV). The objective of this study was to establish appropriate diagnostic criteria for evaluation of dobutamine stress testing with RNV for the detection of early postinfarction ischemia.

METHODS

RNV was performed at baseline and during dobutamine infusion in 10 control subjects and in 30 patients who were studied within 1 week after uncomplicated myocardial infarction. Several quantitative parameters including left ventricular ejection fraction (EF), regional EF, and absolute change in global and regional EF were tested. In addition, regional wall-motion changes were scored by visual analysis. The limit of normal response for each quantitative parameter was defined as the 95th percentile of the distribution observed in control subjects. On the basis of predischarge clinical evaluation and exercise stress testing, patients were grouped as having evidence of residual ischemia (group 1, 15 patients) or no evidence of ischemia (group 2, 15 patients). Sensitivity, specificity, and accuracy in the detection of postinfarction ischemia were calculated for each parameter, and empiric receiver-operating characteristic curves were generated.

RESULTS

The limits of the normal response to dobutamine infusion in the control subjects were found to be a 7.5% and a 12.5% increase in global EF at low and high dose, respectively. Median baseline EF was significantly lower in patients than in control subjects (Mann-Whitney U test: P < .001). There were no differences in resting EF between group 1 and group 2 patients. However, median high-dose EF and increase in EF were significantly lower in group 1 as compared with group 2 patients (56% vs 72% and 5% vs 17%, respectively; Mann-Whitney U test: P < .0001 for both). A biphasic (up-and-down) response with initial increase at low dose followed by decrease or no change in EF at high dose was observed in 66% of group 1 patients and only in 13% of group 2 subjects. The best criterion for detection of postinfarction ischemia was a change of <12.5% in global EF at high-dose dobutamine infusion, with 80% predictive accuracy. The traditional criterion, a change of <5 % or a decrease in EF, yielded an accuracy of only 63%. The association of a change of <12.5% with a biphasic response increased accuracy to 87%, with a sensitivity of 93% and a specificity of 80%. Quantitative regional wall motion analysis showed greater diagnostic accuracy than visual wall motion scoring (83% vs 70%).

CONCLUSIONS

Application of appropriate criteria and stepwise quantitative analysis of RNV during dobutamine infusion may increase accuracy in the detection of early postinfarction ischemia.

Pharmacologic stress echocardiography. Dobutamine and arbutamine stress testing

Pharmacologic stress testing is an important noninvasive method for evaluating patients with known or suspected coronary artery disease who are unable to adequately exercise. Pharmacologic stress echocardiography using dobutamine has been developed over the last 10 to 15 years as an alternative to vasodilator stress testing using nuclear perfusion imaging. As experience has grown, digital subtraction echocardiogram has been shown to be a safe, convenient, and reliable method for stress testing in a variety of patient populations. Digital subtraction echocardiogram has comparable sensitivity, specificity, and accuracy when compared to other stress testing methods which employ cardiac imaging and is superior to the exercise echocardiogram. It has certain advantages over nuclear perfusion imaging in terms of cost and convenience. The recent addition of arbutamine echocardiography (which has been shown to be comparable to digital subtraction echocardiogram) provides another alternative method for pharmacologic stress testing. Continued improvement in echocardiographic image quality and the development of new technologies such as tissue harmonic imaging and contrast echocardiography will hopefully improve the echocardiographic evaluation of wall motion therefore increasing the diagnostic accuracy of echocardiographic stress testing.

Transesophageal echocardiography with stress for the evaluation of patients with coronary artery disease

Echocardiography permits a comprehensive assessment of resting regional and global left ventricular function, the presence and extent of inducible myocardial ischemia, and the identification of myocardial viability. Accordingly, stress echocardiography has become a valuable tool for the evaluation of patient with known or suspected coronary artery disease. In some patients however, a suboptimal transthoracic echocardiogram may limit the performance of interpretation of the test. Transesophageal echocardiography in combination with stress has been recently used for the evaluation of patients with coronary artery disease. This technique is semi-invasive, more time-consuming, and requires a greater degree of expertise on the part of the personnel assisting with the test. In general, complications and side-effects are self-limited and rarely affect the diagnostic accuracy of the test. Based on its ability to provide high quality images, transesophageal stress echocardiography should be considered in patients who have suboptimal transthoracic ultrasound window for the quantitative assessment of myocardial wall-thickening in clinical investigations of ischemic heart disease.

Dobutamine Stress Test to Evaluate Different Sizes of Prosthetic Aortic Valves

Dobutamine stress testing and Doppler echocardiography were used to assess hemodynamics in 27 patients aged 16 to 54 years with various sizes and types of aortic valve prosthesis. All patients underwent a symptom-limited treadmill exercise test within two days of the dobutamine test. There was no significant difference in ejection fractions and transvalvular gradients at rest and during dobutamine stress between St. Jude Medical, Medtronic-Hall, and Carbomedics valves. Exercise duration did not differ significantly among the different types of valve. When patients were classified by their underlying lesion, those with aortic stenosis and those with aortic insufficiency had similar ejection fractions and transvalvular gradients at rest and during dobutamine stress. The mean and peak transvalvular gradients at rest and during dobutamine stress were significantly different in patients with different valve sizes but the extent of the increase in gradients during stress was not significant. Linear regression analysis revealed that both peak and mean gradients during dobutamine stress could be predicted by the resting gradients. There was a negative correlation between valve size and gradients at rest and during stress, while there was a significant correlation between exercise duration and valve size. Dobutamine stress echocardiography was useful for studying hemodynamics in patients with aortic valve prostheses and the findings show that valvular size was the main determinant of exercise capacity.

Comparison of coronary hemodynamics during infusions of dobutamine and adenosine in patients with angina pectoris

Pharmacologic stress tests are used to evaluate the significance of coronary arterial stenosis, and adenosine and dobutamine are often used for this purpose. The aim of this study was to examine coronary hemodynamics in 16 patients with stable exertional angina who had organic stenosis (> 90%) in the left anterior descending coronary arteries and in 13 control subjects at baseline and during separate intravenous infusions of dobutamine (20 micrograms/kg per min [corrected]) and adenosine (140 micrograms/kg per min [corrected]). Measurements of great cardiac vein blood flow and lactate and oxygen contents in the blood from the aortic root and great cardiac vein were analyzed in patients with ischemic signs of myocardial ischemia (ST-segment depression in the precordial ECG leads and/or myocardial lactate production) during the infusions (in 11 patients during adenosine infusion and in 12 patients during dobutamine infusion) and in control subjects. Myocardial oxygen consumption during adenosine infusion did not change compared with the baseline in both groups, whereas it increased during dobutamine infusion in both groups (p < 0.01 compared with the baseline in each case). However, great cardiac vein blood flow was significantly increased compared with the baseline during both infusions in both groups (p < 0.01 compared with baseline in each case), and the oxygen contents of great cardiac vein blood, which contains effluent from the ischemic region, showed no decrease but increased significantly during both infusions in the patients in comparison with control subjects. Although the global oxygen supply was excessive, myocardial ischemia occurred during dobutamine and adenosine infusions in the patients. As myocardial oxygen consumption remained unchanged during adenosine infusion, regional myocardial flow reduction, possibly as a result of flow maldistribution, may contribute, at least partly, to adenosine-induced myocardial ischemia. An increase in myocardial oxygen consumption may be the principal cause of myocardial ischemia during dobutamine infusion, but an inappropriate flow increase in normal myocardium may occur during dobutamine-induced ischemia.

Do beta-blockers affect the diagnostic sensitivity of dobutamine stress thallium-201 single photon emission computed tomographic imaging?

BACKGROUND

The effects of beta-blockers on dobutamine stress 201Tl tomographic imaging are not known. This study was undertaken to examine whether beta-blockers affect the sensitivity of dobutamine stress 201Tl imaging.

METHODS AND RESULTS

One hundred ten patients without previous myocardial infarction underwent dobutamine stress 201Tl single photon emission computed tomography (SPECT) and coronary arteriography, both studies within a 1-week period. Dobutamine was infused at rates of 5, 10, 20, 30, and 40 microg/kg/min in 3-minute stages. Atropine (as much as 1 mg) was injected intravenously when the patient's heart rate was <100 beats/min. Patients in group 1 (n = 72) were receiving beta-blockers and patients in group 2 (n = 38) were not. The SPECT images in group 1 showed perfusion abnormalities in 62%, 87%, and 94% of patients with one-, two-, and three-vessel coronary artery disease (> or = 50% diameter stenosis), respectively, compared with 75%, 71% and 100% in group 2 (p not significant). The overall sensitivities were 82% (37 of 45) in group 1 and 80% (16 of 20) in group 2 (p not significant). The specificities were 81% (22 of 27) in group 1 and 83% (15 of 18) in group 2 (p not significant). The overall accuracies were the same for both groups (82%). Atropine was added more often in group 1 than in group 2 (37/72 vs 5/38, p < 0.001).

CONCLUSIONS

Our results suggest that beta-blockers do not affect the sensitivity, specificity, and accuracy of dobutamine stress 201Tl SPECT imaging for detecting coronary artery disease if atropine is given when the chronotropic response is inadequate. In patients receiving beta-blockers, however, the addition of atropine to dobutamine stress is more frequently required.

Diagnostic and prognostic value of dipyridamole and dobutamine stress echocardiography in patients with Q-wave acute myocardial infarction

The aim of this study was to compare dipyridamole and dobutamine stress echocardiography, performed early in patients with acute myocardial infarction (AMI) to evaluate residual ischemia, viability, and prognosis. Fifty patients (mean age 55 +/- 9 years, 47 men, 3 women) with AMI, all treated with thrombolytic therapy, underwent standard dipyridamole and dobutamine tests, within the fifth day of the event. Wall motion score index and the 16 segments model were used to evaluate contractility. Forty-seven patients underwent coronary angiography within the tenth day of the event. The mean follow-up was 24 +/- 12 months. No side effects occurred during both tests. Both dipyridamole and dobutamine tests were positive for ischemia, in 32 and 33 of 47 patients, respectively (sensitivity 73% and 75%; specificity 67% and 67%); these tests induced an improvement of contractility in 23 and 38 of 139 abnormal segments at baseline, respectively (sensitivity 52% and 86%; specificity 100% and 100%). Cardiac events occurred in 26 of 50 patients, 22 with a positive dipyridamole test and 21 with positive dobutamine test. Thus, both tests were feasible, safe, and useful to evaluate residual ischemia, viability, and prognosis. No significant differences were found in sensitivity and specificity between tests.

Acute elevation of coronary venous pressure does not affect left ventricular contractility in the normal and stressed swine heart: implications for the Fontan operation

OBJECTIVE

After the Fontan operation the right atrium and, thus, the coronary sinus are connected to the pulmonary arterial system, which causes the coronary venous pressure to increase. We investigated the acute effects of elevation of coronary venous pressure on baseline hemodynamics, coronary venous flow, and left ventricular contractility.

METHODS

In acutely instrumented pigs, during complete right heart bypass and during constant cardiac output, pressure in the right atrium, right ventricle, and coronary sinus was altered by a height-adjustable reservoir. At various levels of coronary venous pressure (up to 4 kPa or up to 30 mm Hg), flow from the reservoir was measured and left ventricular hemodynamics and contractility were measured from catheter-derived left ventricular pressure and (conductance) volume data. Contractility of the left ventricle was assessed by the end-systolic pressure-volume relationship derived during an unloading intervention by adjusting the bypass pump speed.

RESULTS

Left ventricular end-diastolic pressure increased slightly (about 5%) with each kilopascal increase in coronary venous pressure, most likely related to diastolic ventricular interaction. No other changes in hemodynamic parameters occurred. Neither coronary venous flow nor left ventricular contractility was influenced by changes in coronary venous pressure. Imposing myocardial stress with dobutamine, 10 microg/kg per minute, did not change these findings.

CONCLUSION

Increasing coronary venous pressure to 4 kPa in the intact circulation with intact autoregulation does not affect coronary flow or left ventricular contractility. We found no experimental evidence for the usefulness of diversion of the coronary sinus to the left atrium during Fontan-type operations

Comparison of dobutamine ECG stress test with predischarge exercise test after acute myocardial infarction

Exercise testing after acute myocardial infarction is commonly used, but in recent years alternative methods have been proposed. Standard exercise testing was compared with dobutamine electrocardiographic (ECG) stress testing in 100 patients after an acute initial myocardial infarction. Dobutamine ECG stress testing was performed in a standard manner at 5 +/- 1 days after the infarction and exercise testing was performed a mean of 10 +/- 2 days following the event. Agreement between both tests was observed in 91 cases (91%), P < .001, Fisher test kappa value, 0.79). The dobutamine test predicted the result of the exercise test with a sensitivity of 100% (95% confidence interval, 87-100) and a specificity of 88% (95% confidence interval 77-93) for a positive predictive value of 75% (95% confidence interval, 62-97) and a negative predictive value of 100% (95% confidence interval, 91-100). Dobutamine ECG stress testing is concluded to be an objective and reliable procedure, which accurately predicts the results of standard exercise testing. It is inexpensive, easy to perform, and although not yet confirmed, could be particularly useful in patients who cannot perform exercise.

Comparison between dobutamine echocardiography and thallium-201 scintigraphy in detecting residual stenosis, ischemia, and necrosis in patients with prior myocardial infarction

BACKGROUND

Following the first attempts to detect myocardial ischemia with two-dimensional echocardiography stress testing, pharmacologic stress using dobutamine infusion has become an alternative to echocardiography exercise testing for evaluation of coronary artery disease. It has been shown that stress echocardiography has a diagnostic accuracy similar to that of an exercise thallium test. Other studies, however, indicated that radionuclide myocardial perfusion imaging was more sensitive than exercise or pharmacologic stress echocardiography for detection of ischemia or jeopardized myocardium.

HYPOTHESIS

The aim of the present study was to determine the ability of dobutamine stress echocardiography in comparison with thallium-201 scintigraphy to identify multivessel disease and the presence of myocardial scar and ischemia in 60 consecutive patients who suffered a first myocardial infarction (MI).

METHODS

Patients were evaluated by coronary angiography and ventriculography, thallium-201 (201TI) tomographic scintigraphy, and dobutamine echocardiography within 3 months of a first MI. Forty-seven had Q-wave MI and 13 had non-Q-wave MI. Eleven patients were excluded from final analysis-7 because of failure to achieve target heart rate in spite of the use of atropine, and 4 because of high blood pressure following the infusion of dobutamine.

RESULTS

Dobutamine echocardiography showed an overall sensitivity of 43% for detection of coronary artery lesions of 50-74% diameter stenosis and 201TI scintigraphy showed a sensitivity of 71%. For detection of lesions of > or = 75% diameter stenosis, dobutamine echocardiography showed a sensitivity of 52% and 201TI a sensitivity of 70%. Overall agreement between wall motion and myocardial perfusion for detection of necrosis and/or ischemia in the infarct area was 40.4% with a kappa coefficient of 0.09 (p = 0.13). For detection of ischemic myocardium outside the infarct zone, overall agreement was 78.6% with a kappa coefficient of 0.49 (p < 0.0001).

CONCLUSION

Dobutamine echocardiography results showed a lower sensitivity than myocardial perfusion images in predicting multivessel coronary artery disease, and there was poor agreement between both methods in identifying necrosis or ischemia.

Prognostic value of dobutamine-atropine stress echocardiography early after acute myocardial infarction. Echo Dobutamine International Cooperative (EDIC) Study

OBJECTIVES

The aim of this multicenter, multinational, prospective, observational study was to assess the relative value of myocardial viability and induced ischemia early after uncomplicated myocardial infarction.

BACKGROUND

Dobutamine-atropine stress echocardiography allows evaluation of rest function (at baseline), myocardial viability (at low dose) and residual ischemia (peak dose, up to 40 micrograms with atropine up to 1 mg) in one test.

METHODS

Dobutamine-atropine stress echocardiography was performed 12 +/- 5 days (mean +/- SD) after a first uncomplicated acute myocardial infarction in 778 patients (677 men; mean age 58 +/- 10 years) with technically satisfactory rest echocardiographic study results. Patients were followed-up for 9 +/- 7 months.

RESULTS

Dobutamine-atropine stress echocardiographic findings were positive for myocardial ischemia in 436 of patients (56%) and negative in 342 (44%). During follow-up, there were 14 cardiac-related deaths (1.8% of the total cohort), 24 (2.9%) nonfatal myocardial infarctions and 63 (8%) hospital readmissions for unstable angina. One hundred seventy-four patients (22%) underwent coronary revascularization (bypass surgery or coronary angioplasty). Spontaneous events occurred in 61 of 436 patients with positive and 40 of 342 patients with negative findings on dobutamine-atropine stress echocardiography (14% vs. 12%, p = 0.3). When only spontaneously occurring events were considered, the most important predictor was myocardial viability (chi-square 9.7). Using the Cox proportional hazards model, only the presence of myocardial viability (hazard ratio [HR] 2.0, p < 0.002) and age (HR 1.03, p < 0.001) were predictive of spontaneously occurring events. When only hard cardiac events were considered, age was the strongest predictor (chi-square 3.6, p = 0.056), followed by wall motion score index (WMSI) at peak dose (chi-square 3.3, p = 0.06) and remote ischemia (chi-square 2.25, p = 0.1). When cardiac death was considered, WMSI at peak dose was the best predictor (HR 9.2, p < 0.0001).

CONCLUSIONS

During dobutamine stress, echocardiographic recognition of myocardial viability is more prognostically important than echocardiographic recognition of myocardial ischemia for predicting unstable angina, whereas WMSI at peak stress was the best predictor of cardiac-related death. Different events can be recognized with different efficiency by various stress echocardiographic variables.

Effects of beta-blockade and atropine on ischemic responses in left ventricular regions subtending coronary stenosis during dobutamine stress echocardiography

OBJECTIVES

This study was designed to examine the effects of a beta-adrenergic blocking agent on the ischemic response to dobutamine stress and to determine the degree to which these effects can be abolished by the addition of atropine.

BACKGROUND

Whether beta-blockade affects the sensitivity of dobutamine stress echocardiography for the diagnosis of coronary artery disease has been controversial.

METHODS

In nine pigs, a left anterior descending coronary artery stenosis was created to reduce flow reserve (maximal/rest flow) to 1.1 to 1.9 without baseline regional wall motion abnormalities. This corresponded to a 50% to 90% diameter stenosis. Wall thickening was measured using epicardial echocardiography. Regional lactate production and coronary venous pH were monitored from an adjacent cardiac vein. A standard protocol of dobutamine stress echocardiography was first performed. After normalization of the ischemic abnormalities elicited with this infusion, esmolol was infused at 50 micrograms/kg body weight per min and the dobutamine test was repeated, with 1.0 mg of atropine added at the maximal dobutamine dose.

RESULTS

Without esmolol, dobutamine stress induced myocardial ischemia with a reduction in regional wall thickening and lactate production in all nine pigs. Multiple regression analysis revealed that coronary flow per heartbeat (p < 0.01) and lactate production (p < 0.05) independently correlated with regional wall thickening during dobutamine stress. The beta-blocker significantly reduced heart rate and regional oxygen consumption and altered the relation between coronary flow per heartbeat and regional wall thickening (p < 0.05) during dobutamine stress. Esmolol prevented dobutamine-induced ischemia (lactate production and wall motion abnormalities) in seven of nine pigs. The addition of atropine induced lactate production and a reduction in wall thickening in five of seven pigs in which ischemia had been prevented by beta-blockade. However, lactate production was higher and regional venous pH was lower with the baseline dobutamine infusion than with that performed after esmolol with atropine added at the maximal dobutamine dose (p < 0.05).

CONCLUSIONS

A correlation between regional wall thickening and coronary flow per heartbeat was demonstrated during baseline dobutamine stress. Beta-blockade shifted this relation so that dobutamine stress-induced myocardial ischemia was attenuated. The mechanisms by which beta-blockade prevents dobutamine-induced ischemia appeared to be mainly through decreases in heart rate and rate of rise in left ventricular pressure, improvement of regional coronary flow per heartbeat and attenuation of regional ischemic lactate production. Adding atropine in conventional doses enhanced the ability of dobutamine stress to induce myocardial ischemia but did not completely abolish the effects of beta-blockade on either the severity of dobutamine-induced wall thickening abnormalities or regional metabolic disturbances.

Cardiac performance in conscious healthy dogs during dobutamine infusion

The aim of this study was to determine the cardiac performance of conscious healthy dogs during stimulation with dobutamine. Eight healthy unsedated beagle dogs were used. Cardiac output was measured by the thermodilution technique and blood pressures by extravascular pressure transducers. Dobutamine challenge at a dosage ranging from 27.5 to 50 micrograms kg-1 min-1 induced a significant rise in cardiac power index (CPI), cardiac index (CI), stroke index (SI) and heart rate (HR) and a significant decrease in pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR). The highest CPI was 2.05 times greater than its basal resting value. The CI was primarily responsible for this increase in CPI. The SI and HR contributed approximately 55 per cent and 45 per cent respectively of the maximal increase in CI.

Transesophageal dobutamine-atropine stress echocardiography: diagnostic accuracy for coronary stenosis detection and localization

Transesophageal echocardiography with dobutamine-atropine stress (TE-DASE) is a recently described technique for evaluation of coronary artery disease (CAD). We undertook this study prospectively to determine the feasibility, reliability and safety of this procedure in patients with known CAD and to evaluate its diagnostic accuracy for coronary stenoses of varying severity. Thirty-seven patients who underwent coronary arteriography (CART) and TE-DASE within a 3-month interval without intervening ischemic events or revascularisation were included in the study CART and stress echograms were independently evaluated by different observers. Stenosis was measured with calipers and a > or = 50% lumen diameter stenosis was considered significant. A reduction or lack of endocardial motion and/or wall thickening on progressive incremental stress was considered an abnormal response. TE-DASE could be successfully completed in 33/37 (90%) patients. Using a modified 16-segment model of the left ventricle (LV), 15.2 +/- 0.8 segments/patient and 501/528 (95%) segments overall could be optimally evaluated. Inter-observer concordance for an abnormal response was 94%. Predictive accuracies for one-vessel disease (1-VD), two-vessel disease (2-VD) and three-vessel disease (3-VD) were 88, 58 and 23% respectively. Overall sensitivity for detection of a significant (> or = 50%) stenosis was 72% (32% for moderate (50-69%), 90% for severe (> or = 70%) stenosis) and specificity was 96%. Diagnostic accuracy for localisation of significant stenosis was 95% for the left anterior descending artery (LAD), 86% for the left circumflex artery (LCX) and 88% for the right coronary artery (RCA). There were no major complications. We conclude that TE-DASE is a safe, reliable and easily-performed procedure and provides excellent visualisation of myocardial segments. Diagnostic accuracy for detection of severe stenosis and its localisation is excellent.

Effects of dobutamine on left ventricular diastolic performance are attenuated in patients with systemic hypertension

We measured Doppler echocardiographic diastolic parameter during infusion of low-dose dobutamine in 14 untreated hypertensive subjects and in 14 normal controls. Low-dose dobutamine accelerated left ventricular relaxation in normal controls but not in hypertensive subjects.

Impact of Beta Blockers on Dobutamine-Atropine Stress Echocardiography

Dobutamine increases oxygen demand in the myocardium and is used in conjunction with echocardiography to detect coronary artery disease. Beta blockers (BB) are partial antagonists of dobutamine and, therefore, offset dobutamine effects. Still, the impact of BB therapy on dobutamine stress echocardiography is not clear. One hundred forty-one dobutamine-atropine echocardiographic studies have retrospectively been analyzed: 27 patients were on BB (19%; group I); and 114 off BB (81%; group II). Coronary angiography was performed in a similar percentage of patients (97% and 85%, respectively; P = NS). No differences in clinical and angiographic profile were found between the groups. Sensitivity (83% vs 71%; P = NS) and specificity (100% vs 95%; P = NS) for coronary artery disease were similar in both groups. Atropine was infused more frequently to patients from group I (67% vs 46%; P = 0.04). Limiting side effects and prolonged ischemia presented with the same frequency in both groups. When the dobutamine test was positive, severe extent of ischemia appeared more often in patients from group I than in patients from group II (66% vs 33%; P = 0.03). The majority of patients from group I (55%) with severe extent of ischemia and only 12% from group II received atropine (P = 0.02). No differences were found in dobutamine time and extent of ischemia in patients from group I who had a positive response to dobutamine. On the contrary, patients from group II with one vessel disease had a dobutamine time longer (10.5 +/- 3.8 vs 7.8 +/- 3.7 min; P < 0.05) and extent of ischemia smaller (1.8 +/- 0.4 vs 2.6 +/- 0.5 segments; P < 0.05) than patients from group II with multivessel disease. We conclude that: 1) sensitivity of dobutamine-atropine echocardiography for diagnosis of coronary artery disease remains even if patients are on BB; 2) patients with significant coronary artery disease who are taking BB often develop severe myocardial ischemia during dobutamine-atropine stress echocardiography; and 3) BB therapy precludes stratification of a positive echocardiographic response. These conclusions should be confirmed in a prospective study to be considered as definitive. (ECHOCARDIOGRAPHY, Volume 13, July 1996)

Dobutamine stress echocardiography for detection of coronary artery stenosis in children with Kawasaki disease

OBJECTIVES

This study was designed to assess the feasibility and diagnostic accuracy of dobutamine stress echocardiography for detection of coronary artery stenosis in children with Kawasaki disease.

BACKGROUND

Dobutamine stress echocardiography is valuable as an alternative test for detection of coronary artery disease in adult patients; however, its usefulness for children has been demonstrated only in limited cases.

METHODS

Dobutamine stress echocardiography (up to 30 microgram/kg body weight per min) was performed in 50 patients at the convalescent stage of Kawasaki disease, including 26 patients with coronary sequelae documented by previous coronary angiography (sequelae group, 3 to 15 years old) and 24 patients with normal coronary arteries documented by echocardiography (normal group, 7 to 16 years old), who underwent quantitative coronary angiography on a separate day. Left ventricular regional wall motion divided into 16 segments was assessed in relation to the extent of coronary artery disease. A positive test response was defined as a new or worsened wall motion abnormalities.

RESULTS

Significant coronary artery disease (> or = 50% diameter stenosis of major vessels) was present in 21 patients in the sequelae group. There was no significant difference in the maximal dose of dobutamine between the sequelae and normal groups ([mean +/- SD] 22.4 +/- 5.1 vs. 24.2 +/- 2.5 microgram/kg per min). Heart rate and systolic blood pressure were significantly increased (p < 0.01) at maximal dose of dobutamine compared with values at rest in both groups; consequently, the rate-pressure product exceeded 20,000 in 20 (40%) of the 50 patients during dobutamine infusion. Ten patients had self-limiting side effects; however, there were no serious complications from stress-induced ischemia. New wall motion abnormalities corresponding to the extent of coronary artery disease were detected in 19 of 21 patients in the sequelae group, whereas no wall motion abnormalities were detected in the normal group. Thus, the sensitivity and specificity of dobutamine stress echocardiography for the detection of coronary artery disease were 90% and 100%, respectively.

CONCLUSIONS

We conclude that dobutamine stress echocardiography is a safe and accurate diagnostic method for detection of coronary artery stenosis in Kawasaki disease. Moreover, this is a possible alternative method for patients unable to exercise adequately, even if they are small children.

Dobutamine stress echocardiography: a new, noninvasive method for detecting ischemic heart disease

Pharmacologic induction of exercise with dobutamine hydrochloride, coupled with the technology of echocardiography, is an alternate method for evaluating ischemic heart disease. Dobutamine stress echocardiography involves obtaining echocardiographic images before, during, and after a titrated dobutamine infusion is administered. The study is positive if global or regional ventricular wall motion abnormalities develop. With our changing health care environment, this cost-effective, noninvasive diagnostic procedure is becoming a standard for determining the presence of coronary artery disease in those individuals who are unable or unwilling to undergo exercise stress testing.

Dobutamine-induced transmural myocardial ischemia in a patient with mild coronary lesions

A 70-year-old man was admitted for evaluation of retrosternal pain at rest. During infusion of dobutamine (25 micrograms/kg/min) the patient developed angina, ST-segment elevation in the inferior leads, and echocardiographic hypokinesia in the inferior-basal myocardial wall. Coronary angiography revealed insignificant (20-30%) stenosis of the right coronary artery and a normal remaining tree. This case suggests that dobutamine may induce transmural myocardial ischemia in patients with mild coronary lesions, probably by producing occlusive coronary spasm on a substrate of arterial endothelial dysfunction.

Stress imaging. Current clinical options for the diagnosis, localization, and evaluation of coronary artery disease

As technology advances, new methods evolve. In this article, the methods of stress testing and related imaging in coronary disease are addressed, and dynamic and pharmacologic stress, direct and indirect methods, are defined and evaluated. The stress imaging methods related to the modalities of scintigraphy and ultrasound are reviewed and their advantages and disadvantages assessed in view of scientific and economic factors.

Incremental doses of dobutamine induce a biphasic response in dysfunctional left ventricular regions subtending coronary stenoses

BACKGROUND

Dobutamine stress echocardiography has been proposed as a diagnostic tool to identify viable myocardium. How regional wall thickening responds to dobutamine in the ischemic or short-term hibernating myocardium has not been adequately defined. We hypothesized that regional wall thickening would improve initially and subsequently deteriorate with incremental doses of dobutamine in viable myocardial regions supplied by a stenotic coronary artery. This study was undertaken to determine whether this biphasic pattern of regional function characterizes the response of ischemic or hibernating myocardium to dobutamine and to explore the factors and mechanisms that determine this response.

METHODS AND RESULTS

Twenty-six pigs in four groups were studied: a control group (n = 5) to assess the response of myocardium perfused by nonstenotic coronary artery to incremental doses of dobutamine, and three experimental groups with a left anterior descending coronary artery stenosis producing acute myocardial ischemia (n = 7), short-term myocardial hibernation for 90 minutes (n = 7), and short-term hibernation for 24 hours (n = 7) to determine the functional and metabolic response to dobutamine under these conditions. Regional coronary flow was reduced to 40% to 60% of baseline, with significant reductions of regional wall thickening as measured by two-dimensional echocardiography and sonomicrometers. An incremental dobutamine infusion from 2.5 to 25 micrograms.kg-1.min-1 increased wall thickening and coronary flow without lactate production in the control group. In the other three groups, during the incremental dobutamine infusion, regional wall thickening improved initially, from 11.4 +/- 7.5% to 19.8 +/- 11.4%, P < .01, at dobutamine doses of 2.5 to 10 (4.5 +/- 2.2) micrograms.min-1.kg-1 but deteriorated subsequently to 5.0 +/- 5.8% at the maximal dose of dobutamine of 12.6 +/- 4.1 micrograms.min-1.kg-1. The initial improvement of regional wall thickening was associated with a small increase in regional coronary flow (from 0.53 +/- 0.18 to 0.68 +/- 0.25 mL.min-1.g-1 myocardium, P < .05) and with regional lactate production. High doses of dobutamine did not further increase regional coronary flow but markedly increased lactate production and induced regional myocardial acidosis (pH 7.26 +/- 0.07). The biphasic pattern of response to dobutamine was observed in each of the three experimental groups. Both peak improvement and peak deterioration occurred earlier and at lower dobutamine dose levels in the group with acute ischemia compared with the group with short-term hibernation for 24 hours (P < .05).

CONCLUSIONS

A biphasic response of wall thickening to incremental dobutamine with initial improvement and subsequent deterioration is characteristic of ischemic or short-term hibernating myocardium. The initial low-dose dobutamine infusion improved wall thickening in the ischemic or hibernating myocardial region to a modest level. This initial modest improvement was transient and at the expense of metabolic deterioration of myocardial ischemia, so that at higher doses during prolonged dobutamine infusion, wall thickening deteriorated, lactate accumulated, and myocardial acidosis developed.

A comparison of the efficacy of dopexamine and dobutamine for increasing oxygen delivery in high-risk surgical patients

Peri-operative increase of oxygen delivery has been shown to reduce mortality in high-risk surgical patients. This study compares the effectiveness of dopexamine and dobutamine when used to increase cardiac output as part of a regimen to increase oxygen delivery. Sixteen surgical patients were randomly allocated to receive either dopexamine or dobutamine, which was increased to a stable dose defined as either oxygen delivery index > 600 ml/min/m2, or tachycardia > 20% above baseline, other dysrhythmias or angina. At this "stable" dose there were significant increases in cardiac index (2.4 +/- 0.2 vs 3.7 +/- 0.3 l/min/m2) and oxygen delivery (380 +/- 73 vs 579 +/- 40 ml/min/m2) in the dopexamine group (P < 0.05); but not the dobutamine group. Five out of eight patients receiving dopexamine and three out of eight receiving dobutamine reached target oxygen delivery. Three dobutamine patients, but no dopexamine patients, had angina or dysrhythmias. In preoperative high-risk surgical patients, dopexamine can allow greater increases in oxygen delivery than dobutamine, due to cardiac effects that limit the dobutamine infusion rate.

Assessment of magnetic resonance velocity mapping of global ventricular function during dobutamine infusion in coronary artery disease

BACKGROUND

Magnetic resonance imaging (MRI) is a versatile technique for examination of the cardiovascular system but only recently has assessment of myocardial ischaemia in coronary artery disease (CAD) become possible, for example by demonstrating abnormalities of regional ventricular contraction during stress. Global ventricular function during stress was assessed by MRI of aortic flow, which has not been previously attempted.

DESIGN

Variables measured by MRI reflecting the effect of ischaemia on global ventricular function during dobutamine stress were correlated with thallium-201 myocardial perfusion tomography.

PATIENTS

10 normal controls and 25 patients with CAD.

SETTING

Tertiary cardiac referral centre.

METHODS

Novel MRI sequences and analysis systems were used to measure the following variables during staged dobutamine infusion to 20 micrograms/kg/min: stroke volume, cardiac output, cardiac power output, peak flow, peak flow acceleration, aortic back flow, and flow wave velocity. Heart rate, blood pressure, double product, and maximum tolerated dobutamine dose were also measured. Multiple regression analysis was used to compare changes during stress with 201TI tomography.

RESULTS

All parameters except for stroke volume and diastolic blood pressure increased in the controls. In the patients with CAD a significant relation was shown between the extent of reversible ischaemia and the change in peak flow acceleration (P < 0.00001), peak flow (P = 0.002), cardiac power output (P = 0.036), maximum dobutamine dose (P = 0.039), and systolic blood pressure (P = 0.04). Peak flow acceleration accounted for 58.4% of the variation in reversible ischaemia, and after allowing for this, only cardiac power output remained independently predictive adding a further 4.2% to the model (adjusted r2 = 0.626). A decrease in peak flow acceleration with an increase in dobutamine infusion indicated moderate or severe ischaemia (chi 2 = 10.2, P = 0.017).

CONCLUSION

MRI may be used to assess variables of aortic flow during stress, which includes acceleration with high temporal resolution. Peak flow acceleration was the most sensitive indicator of the effect of ischaemia on global ventricular function.

Dobutamine stress echocardiography for the identification of multivessel coronary artery disease after uncomplicated myocardial infarction: the importance of test end-point

Our aim was to verify whether the sensitivity of pharmachological stress echocardiography for multivessel disease after acute myocardial infarction may be improved by a more aggressive protocol, i.e. not considering the appearance of the first wall motion abnormality as the absolute end-point if it occurs in the infarcted area without clinical or instrumental markers of extensive ischemia or left ventricular dysfunction. One-hundred twenty-one consecutive patients (age 32-71 years) prospectively underwent dobutamine-atropine stress echo (dobutamine infusion up to 40 micrograms/kg/min with additional atropine 1 mg) 11.8 +/- 4.8 days after uncomplicated myocardial infarction and coronary angiography within 6 weeks. Criteria for stopping the test were: significant ST depression or elevation, typical chest pain, major arrhythmias and left ventricular dysfunction. The test was considered as positive if a deterioration of basal wall motion pattern was observed: it was defined homozonally positive (the deterioration occurred in the myocardial area fed by the culprit vessel) or heterozonally positive (the deterioration occurred in a different vascular area). A coronary stenosis > 70% of vessel lumen was defined as critical. Thirty-four patients showed a negative test result. Among the 87 patients with positive test, 65 had no further wall motion deterioration from the first-induced wall motion abnormality (WMA) to peak test (Group A), whereas nine patients showed further homozonal (Group B) and 13 further heterozonal (Group C) asynergies. Sensitivity, specificity and accuracy of dobutamine stress echocardiography for multivessel disease were, respectively, 63%, 96% and 82% using the first-induced wall motion abnormality as test end-point, whilst they were 84% (P < 0.01), 93% and 89% according to the aggressive approach previously described. Dobutamine stress time of patients with multivessel disease was higher in Groups B and C (13.1 +/- 3.6 min) than in Group A (9.8 +/- 3.7 min, P < 0.01) and, finally, the mean obstruction of non-culprit vessel was higher in Group A (62.2%) than in Group C (47.4%, P < 0.05). No major complications were found. We conclude that the sensitivity of dobutamine stress echocardiography for multivessel disease following recent myocardial infarction is critically dependent on the test end-point. It may be improved by a more aggressive approach capable to identify less severe heterozonal coronary lesions.

Dobutamine stress echocardiography in orthotopic heart transplant recipients. VACOMED Research Group

OBJECTIVES

This study sought to determine whether dobutamine stress echocardiography could accurately identify coronary artery disease after heart transplantation.

BACKGROUND

After heart transplantation, coronary artery disease is related to either diffuse concentric intimal thickening or focal stenosis and may be underdiagnosed by coronary angiography.

METHODS

We enrolled 41 patients, a mean (+/- SD) of 40 +/- 20 months after heart transplantation, at the time of their routine control coronary angiogram. Three patients were excluded because of poor echogenicity on the angiogram and one because of ventricular premature beats. Standard echocardiographic views were acquired at baseline and at incremental dobutamine infusion levels (from 5 to a maximal dose of 40 micrograms/kg body weight per min at 3-min intervals). Regional wall motion score was calculated from a 16-segment model, and each segment was graded from 1 (normal) to 4 (dyskinesia). Coronary angiography was performed 24 h after dobutamine stress echocardiography, and angiograms were analyzed in blinded manner.

RESULTS

Twenty-three (62%) of 37 patients had normal coronary angiographic findings. Dobutamine stress echocardiography showed abnormalities in only 2 of 23 patients. Fourteen patients (38%) had abnormal angiographic findings, seven of whom had stenoses > 50%. Dobutamine stress echocardiography correctly identified the corresponding hypoperfused segments in these seven patients. More of interest were the other seven patients, of whom three had angiographic nonsignificant stenoses (< 50%), and four had minor diffuse coronary irregularities. Dobutamine stress echocardiography showed hypokinesia in five of these seven patients despite nonsignificant lesions at coronary angiography. The respective overall sensitivity and specificity of dobutamine stress echocardiography were 86% and 91%. At follow-up, 2 of the 37 patients had an acute myocardial infarction. Both had abnormal findings on dobutamine stress echocardiography: One had normal coronary angiographic results, and one had significant coronary lesions.

CONCLUSIONS

Dobutamine stress echocardiography is a useful technique for the diagnosis of coronary artery disease after heart transplantation. These preliminary results indicate that dobutamine stress echocardiography may have a predictive value for further ischemic events in heart transplant recipients.

Transesophageal dobutamine stress echocardiography in the evaluation of coronary artery disease

OBJECTIVES

The goal of this study was to determine the feasibility, safety, sensitivity and specificity of transesophageal dobutamine stress echocardiography for the detection of coronary artery disease.

BACKGROUND

Dobutamine stress echocardiography has been shown to be an extremely sensitive and specific noninvasive technique for the detection of myocardial ischemia. However, inadequate transthoracic images preclude the use of dobutamine stress echocardiography in a small but significant group of patients. Transesophageal echocardiography provides better resolution than that obtained with routine transthoracic imaging.

METHODS

Patients scheduled for routine cardiac catheterization underwent transesophageal dobutamine stress echocardiography. All patients underwent coronary arteriography within 48 h of the study, and lesion severity was determined by quantitative coronary angiography. Significant coronary obstruction was defined as stenosis > 50%.

RESULTS

Fifty-one male patients were enrolled in the study; six were excluded for technical reasons. There were no adverse outcomes or complications. Of 27 patients with significant coronary artery disease, 22 had positive study results (sensitivity 82%). Of 13 patients without significant obstructive coronary disease, 1 had a false positive study result (specificity 93%). In patients with a minimal lumen diameter < 1.25 mm, sensitivity was > 80%, and in patients with a minimal lumen diameter > 1.5 mm, sensitivity was < 70%, suggesting that lesions with a minimal lumen diameter < 1.25 mm are more likely to be physiologically significant.

CONCLUSIONS

Transesophageal dobutamine stress echocardiography is a feasible, safe and accurate technique for the detection of myocardial ischemia. There are inherent limitations to this technique in that transesophageal echocardiography must be performed. Transesophageal dobutamine stress echocardiography may allow extension of dobutamine stress testing to patients with inadequate transthoracic echocardiographic imaging and may provide an opportunity for further research applications.

Relation between thallium uptake and contractile response to dobutamine. Implications regarding myocardial viability in patients with chronic coronary artery disease and left ventricular dysfunction

BACKGROUND

Both thallium scintigraphy and dobutamine echocardiography have been used to assess myocardial viability. However, thallium uptake and the inotropic response to dobutamine are expressions of different cellular phenomena. The present study was undertaken to investigate the relation between the two methods in patients with chronic coronary artery disease and left ventricular dysfunction to derive insights into the mechanisms related to myocyte viability.

METHODS AND RESULTS

Thirty patients (28 men and 2 women; age, 59 +/- 10 years) with chronic coronary artery disease and impaired left ventricular systolic function at rest (mean ejection fraction, 32 +/- 9%) were included in the study. Patients underwent transesophageal echocardiography during incremental doses of dobutamine from 2.5 to a maximum of 40 micrograms.kg-1.min-1 and single photon emission computed tomographic thallium scintigraphy using a stress-redistribution-reinjection protocol. The left ventricle was divided into 16 segments for analysis of echocardiographic and thallium images. Segmental myocardial contractile function was graded as normal, hypokinesis, akinesis, or dyskinesis at each incremental dose of dobutamine. Thallium uptake in each myocardial segment was graded on a 5-point scale from 0 (absent) to 2 (normal) for each of the stress, redistribution, and reinjection images. A segment was considered viable if the assigned thallium score was 1 or higher (normal uptake or only mild to moderate defect) in any of the stress, redistribution, or reinjection images. Among 472 myocardial segments available for analysis, 311 had resting wall motion abnormalities, of which 56% (173/311) showed contractile improvement with dobutamine (usually first observed at < or = 10 micrograms.kg-1.min-1) and 84% (262/311) were considered viable by thallium scintigraphy (P < .0001). Of the 262 segments considered viable by thallium, 167 (64%) had a contractile improvement with dobutamine; in contrast, only 6 of the 49 segments (12%) considered nonviable by thallium had a positive dobutamine response (P < .0001). Furthermore, a positive inotropic response to dobutamine was significantly related to the magnitude of thallium uptake: the proportion of segments with a positive dobutamine response rose with increasing magnitude of thallium uptake (P < .001). The disagreement between the two tests was related primarily to segments considered viable by thallium that did not show contractile improvement with dobutamine.

CONCLUSIONS

These findings demonstrate the existence of a relation between thallium uptake and the inotropic response to dobutamine in patients with chronic coronary artery disease and left ventricular dysfunction. However, the proportion of segments showing a positive response to dobutamine is significantly lower than those with thallium uptake, suggesting that the cellular mechanisms responsible for a positive inotropic response to adrenergic stimulation require a higher degree of myocyte functional integrity than those responsible for thallium uptake.

Coronary flow reserve assessment by dobutamine transesophageal Doppler echocardiography

OBJECTIVES

This study attempted to determine the sensitivity and specificity of coronary flow reserve derived using transesophageal echocardiography for left anterior descending coronary artery stenosis.

BACKGROUND

Transesophageal echocardiography can be used to measure coronary flow velocity and may provide a less invasive means of assessing coronary flow reserve.

METHODS

Seventy-eight adult patients were studied by pulsed Doppler transesophageal echocardiography of the proximal left anterior descending coronary artery during a control period and peak (i.e., 40 micrograms/kg body weight per min) dobutamine infusion. Coronary flow reserve index was calculated as the ratio of maximal diastolic coronary velocity at peak dobutamine infusion to the control level and was considered abnormal if < 1.81. Two-dimensional transesophageal left ventricular views were obtained for analysis of wall motion.

RESULTS

Coronary angiography showed > or = 70% (group A, n = 18), 0% to < 70% (group B, n = 21) and no (group C, n = 39) left anterior descending coronary artery diameter stenosis. An abnormal coronary flow reserve index did not differ from a new regional wall motion abnormality in sensitivity for left anterior descending coronary stenosis in group A (15 [83%] of 18 vs. 15 [83%] of 18, p = NS) but was significantly more sensitive in group B (12 [57%] of 21 vs. 2 [10%] of 21, p < 0.025). The specificity for no left anterior descending coronary stenosis in group C between a normal coronary flow reserve index and no new regional wall motion abnormality did not differ (87% vs. 97%, p = NS).

CONCLUSION

Doppler coronary flow reserve and two-dimensional dobutamine transesophageal echocardiography are equally sensitive for the detection of left anterior descending coronary stenosis > or = 70% and equally specific. However, Doppler coronary flow reserve, compared with two-dimensional dobutamine transesophageal echocardiography, is more sensitive for intermediate left anterior descending coronary stenosis and may play a significant adjunctive role to cardiac catheterization and other noninvasive techniques for assessing coronary artery disease.

Pharmacologically induced myocardial ischemia: a comparison of dobutamine and dipyridamole

The purpose of our study was to compare the ability of dobutamine and dipyridamole infusion to induce myocardial ischemia. In a population of 16 anesthetized open-chest swine, a coronary artery stenosis sufficient to abolish the hyperemic response to a 15-second total occlusion was created. Heart rate, systolic blood pressure, and dP/dt were recorded. Myocardial segment shortening was determined by sonomicrometry in all animals. In a subset of seven animals regional myocardial blood flow was measured by injection of radiolabeled microspheres. Dipyridamole was infused according to a high-dose protocol. After a washout period and reestablishment of a baseline state, dobutamine was infused incrementally. There was no significant difference between the baseline states. Dipyridamole did not affect heart rate but did significantly decrease blood pressure and rate-pressure product. Myocardial segment shortening decreased in the ischemic zone by 0.07 +/- 0.08 (p = 0.004). Dobutamine infusion significantly increased heart rate, blood pressure, and rate-pressure product. Myocardial segment shortening in the ischemic zone decreased by 0.17 +/- 0.09 (p < 0.001). Dobutamine decreased blood flow in the ischemic zone relative to baseline. Both dobutamine and dipyridamole infusion resulted in myocardial ischemia. The magnitude of the ischemic response is greater for dobutamine than for dipyridamole.

Transesophageal dobutamine stress echocardiography for evaluation of patients with coronary artery disease

OBJECTIVES

The present study was undertaken to determine the safety, feasibility and diagnostic accuracy of transesophageal dobutamine stress echocardiography for the evaluation of patients with known or suspected coronary artery disease.

BACKGROUND

Dobutamine stress echocardiography has proved to be a valuable method for detecting and prognosticating ischemic heart disease. In addition, it may provide accurate information about myocardial viability in patients with systolic dysfunction. However, in some patients the technique may be limited by poor myocardial imaging with the conventional transthoracic approach.

METHODS

Seventy-six patients (62 men, 14 women; mean age +/- SD 60 +/- 10 years) who underwent coronary angiography were included in the study. Transesophageal stress echocardiograms were performed after withdrawal of antianginal medications for > or = 48 h. Dobutamine was infused at a starting dose of 2.5 micrograms/kg body weight per min and was increased by 5-micrograms/kg per min increments every 5 min to a maximum of 40 micrograms/kg per min. Two-dimensional views were acquired at each stage and digitized for subsequent analysis. The left ventricle was divided into 16 segments, and each segment was assigned to a major coronary artery with the use of a model of regional distribution of coronary perfusion.

RESULTS

Sixty-two of the 76 patients had angiographic evidence of coronary artery disease. New or worsening regional wall motion abnormalities developed during dobutamine infusion in 55 of these 62 patients and in none of the 14 patients with normal coronary arteries (sensitivity 89%, specificity 100%, overall accuracy 91%). Regional wall motion abnormalities in the distribution of more than one major coronary artery were seen in 3 of the 25 patients with single-vessel coronary artery disease and in 30 of the 37 patients with multivessel disease (p < 0.0001). The test was successfully completed in 73 (96%) of the 76 patients; it was discontinued in the remaining 3 patients because of intolerance to the probe. No major complications occurred in any patient. Minor complications developed in seven patients but did not affect the diagnostic accuracy of the test.

CONCLUSIONS

Transesophageal dobutamine stress echocardiography is a safe, feasible and accurate method for assessing coronary artery disease. Its use should be considered in patients who have a suboptimal ultrasound window, and it provides an excellent tool for clinical investigations based on ultrasound imaging of the myocardium.

Safety and tolerability of dobutamine-atropine stress echocardiography: a prospective, multicentre study. Echo Dobutamine International Cooperative Study Group

Diagnostic tests that are hazardous or infeasible, or both, may become accepted before inadequacies are recognised; only multicentre trials can provide the necessary information for an unrestricted acceptance of any new diagnostic procedure. We prospectively studied the results obtained in 24 experienced echocardiography laboratories. 2949 tests were done in 2799 patients. In 341 tests (12% of the overall population, 21% of the negative tests) the test could not be completed because of complex ventricular tachyarrhythmias (134, 38% of all submaximal studies); nausea and/or headache (71, 20%); hypotension and/or bradycardia (62, 17%); supraventricular tachyarrhythmias (44, 12%); hypertension (24, 7%); and others (20, 6%). Dangerous events (life-threatening complications or side-effects requiring specific treatment and lasting more than 3 hours, or new hospital admission) occurred in 14 cases (1 every 210 tests)--9 cardiac (3 ventricular tachycardias; 2 ventricular fibrillations; 2 myocardial infarctions; 1 prolonged antidote-resistant myocardial ischaemia; 1 severe, persistent hypotension) and 5 extracardiac (atropine poisoning with hallucinations lasting several hours in the absence of either myocardial ischaemia or hypotension). Life-threatening and/or longlasting complications may occur during dobutamine/atropine stress echocardiography. The test is generally well tolerated, although may be interrupted by minor, self-limiting, usually symptomless side-effects.

A consideration of current clinical options for stress imaging in the diagnosis and evaluation of coronary artery disease

The evolution of technology and our health care system, tinctured by advocacy groups for specific imaging modalities, has produced controversy, relating to the optimal stress imaging method for coronary disease evaluation. Stress perfusion scintigraphy and stress echocardiography advocates seem to make claims that each nullify the other. This extensive, in-depth review of the subject presents facts as well as opinion and experience in an effort to assess the full portrait of the issue for consideration by advocates as well as those many yet undecided. The issue is an evolving one, affected strongly by the reader's own experience. The presentation is not meant to be the final word. Rather, it seeks to present a basis for understanding and progress in both fields.

Dobutamine-atropine stress echocardiography and clinical data for predicting late cardiac events in patients with suspected coronary artery disease

PURPOSE

To compare the relative value of clinical variables with dobutamine-atropine stress echocardiography to predict cardiac events during long-term follow-up. Dobutamine stress echocardiography is increasingly used for the detection of coronary artery disease, but little is known of its prognostic value.

PATIENTS AND METHODS

A total of 430 patients (310 men; mean age 61 years, range 22 to 90) were enrolled in the study. Patients were referred for chest pain complaints and were unable to perform an adequate exercise stress test. All patients underwent dobutamine-atropine stress test (incremental dobutamine infusion: 10 to 40 micrograms/kg/minute, continued with atropine 0.25 to 1 mg intravenously if necessary to achieve 85% of the age predicted maximal heart rate, without symptoms or signs of ischemia) and clinical cardiac evaluation. Follow-up was 17 +/- 5 months, with a minimum of 6 months; 3 patients were lost to follow-up. Cardiac events were defined as cardiac death, nonfatal myocardial infarction, and coronary revascularization.

RESULTS

Seventy-nine cardiac events occurred in 76 patients: cardiac death (n = 11), nonfatal myocardial infarction (n = 18), and coronary revascularization (n = 50). By multivariate regression analysis, the prognostic value of the stress test in addition to common clinical variables was assessed. (1) Cardiac death was predicted by age greater than 70 years (odds ratio 5.6, 1.5 to 20) or new wall motion abnormalities in a study that is normal at rest (odds ratio 4.1, 1.1 to 15). (2) Death or myocardial infarction was predicted by a history of myocardial infarction (odds ratio 4.8, 1.8 to 13) or age greater than 70 years (odds ratio 2.3, 1.1 to 5.4), and the stress test outcome provided no additional information. (3) If all events were combined, only stress test results were prognostic: new wall motion abnormalities in a study that is normal at rest (odds ratio 3.1, 1.9 to 5.1), wall motion abnormalities at rest (wall motion score at rest > or = 1.12) (odds ratio 2.5, 1.4 to 4.0), or any new wall motion abnormalities during stress (odds ratio 2.0, 1.4 to 3.8). The positive predictive value of any new wall motion abnormality during stress for all late cardiac events was 25% (95% confidence interval [CI] 19 to 31) with a negative predictive value of 87% (95% CI 83 to 91).

CONCLUSION

In a large cohort of unselected patients with chest pain syndromes, new wall motion abnormalities induced by dobutamine provide additional information for late cardiac events, independent of clinical variables.

Dobutamine two-dimensional transesophageal echocardiographic stress testing for detection of coronary artery disease

Atrial pacing and dipyridamole transesophageal echocardiography have been shown to be sensitive and specific tests for the detection of coronary artery disease. However, the sensitivity and specificity of dobutamine transesophageal echocardiography have not been reported. The purpose of this study was to determine the feasibility, sensitivity, and specificity of dobutamine transesophageal echocardiography for the detection of coronary artery disease. Transesophageal echocardiographic assessment of left ventricular function was performed in 81 adult patients aged 62 +/- 12 years during stepwise infusion of dobutamine from 5.0 to 40 micrograms/kg/min. Ischemia was diagnosed by the development of severe hypokinesis, akinesis, or dyskinesis of a previously contractile left ventricular segment. Coronary artery disease was defined by angiography as a reduction in luminal diameter of > or = 70% of an epicardial or > or = 50% of the left main coronary artery. In patients who had undergone coronary artery bypass graft surgery, a stenotic bypass graft was defined as a reduction in luminal diameter of > or = 70%. In patients without previous CABG, significant coronary artery disease was present in 21 patients: 5 with single-vessel disease, 7 double-vessel disease, 8 triple-vessel disease, and 1 left main coronary disease. Dobutamine transesophageal echocardiography had a sensitivity of 90% (19 of 21) and specificity of 94% (49 of 52) for the detection of coronary artery disease. In patients with previous CABG (n = 8), the sensitivity and specificity for the detection of bypass graft stenosis were 100% (4 of 4) and 75% (3 of 4), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine 99mTc-MIBI single-photon emission tomography: non-exercise-dependent detection of haemodynamically significant coronary artery stenoses

Dobutamine pharmacological stress testing in conjunction with technetium-99m methoxyisobutylisonitrile single-photon emission tomography (MIBI SPET) may be a useful alternative to convential exercise stress MIBI SPET for the detection and localisation of coronary artery stenoses. Therefore, 35 patients with stenoses (> or = 50% diameter reduction) of one or more coronary arteries were selected for dobutamine MIBI SPET. Each patient underwent MIBI injection at rest and during dobutamine infusion with incremental doses (5, 10, 15 and 20 micrograms kg-1 min-1). A conventional exercise stress test (EST) was performed in all patients. Peak double product during steady-state dobutamine infusion (18,200 +/- 4200 mmHg min-1) was lower (P = 0.0001) than during EST (21,700 +/- 4900 mmHg min-1). Image quality was good in all but one patient, who had to be excluded from data analysis due to excessive hepatobiliary MIBI activity. Dobutamine-induced perfusion abnormalities were observed in 30/34 MIBI SPET studies, resulting in an overall detection rate for coronary artery disease of 88%. A pathological EST was observed in 23/34 patients (68%). The detection rate of individual coronary artery stenoses was 85% (28/33) for stenosess with a severe diameter reduction (> 70%) and 50% (12/24) for stenoses with a moderate diameter reduction (> or = 50-70%). In particular, sensitivity and specificity for the detection of moderate and severe stenoses (> or = 50%) were 75%/100% for left anterior descending, 67%/95% for left circumflex and 67%/69% for right coronary artery stenoses. Dobutamine MIBI SPET is a well-tolerated, non-exercise-dependent test for detection and localisation of haemodynamically significant coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Dobutamine stress echocardiography: sensitivity, specificity, and predictive value for future cardiac events

We conducted a retrospective study to determine whether dobutamine stress echocardiography (DE) can be used for risk stratification of patients with known or suspected coronary artery disease (CAD). The study population consisted of 77 patients who underwent DE at our institution. The protocol consisted of an echocardiogram at baseline followed by imaging during intravenous dobutamine infusion starting at 10 micrograms/kg/min with increments of 10 micrograms/kg/min every 3 minutes to a maximum dose of 40 micrograms/kg/min. The reasons for performing DE included preoperative cardiac evaluation (30), chest pain (23), assessment of ischemia (18), and suspected restenosis (6). DE was classified according to wall motion response as normal (before and during DE), fixed abnormal (abnormal before with no change during DE), or ischemic (new wall-motion abnormality during DE). Mean duration of follow-up was 10 months. Cardiac events occurred in 14 patients. These included congestive heart failure in seven patients, myocardial infarction in six, and cardiac death in one. A normal wall-motion response (n = 40) was associated with a low incidence of cardiac events (5%), whereas 5 of 10 patients (50%) with an ischemic response had events. The risk of cardiac events was intermediate (26%) in patients with fixed abnormal wall motion. Overall sensitivity of DE for predicting future cardiac events was 85%. In 45 patients who underwent coronary angiography within 2 months of DE, the test detected CAD with a sensitivity of 71%. In conclusion, the wall-motion response during DE may be used for identifying patients at high risk for future cardiac events.

Comparison of dobutamine infusion and exercise during radionuclide ventriculography in the risk stratification after acute myocardial infarction

Forty-eight patients with acute myocardial infarction were subjected to radionuclide ventriculography during exercise and dobutamine infusion after a mean duration of 25 +/- 18 days following acute myocardial infarction. The results were compared and correlated with coronary angiography. Two patterns of abnormal response of radionuclide ventriculography were identified: (1) a worsening of the baseline wall motion abnormality confined to the infarcted area, and (2) fresh regional wall motion abnormalities in areas with normal motion at rest. Of 44 patients with significant coronary artery lesions (> or = 70% diameter stenosis), 18 had single vessel disease and 26 had multivessel disease. Dobutamine and exercise radionuclide ventriculography identified 23 and 21, respectively, of 26 multivessel disease patients yielding sensitivities of 88% and 80%. Seven of 18 single vessel disease patients showed a worsening of baseline wall motion abnormality of infarct area on dobutamine infusion radionuclide ventriculography. Subgroup analysis of coronary angiograms of single vessel disease revealed that 10 of 18 patients had subtotal occlusion of infarct-related artery supplying a hypokinetic area and the rest had a totally occluded coronary artery supplying an akinetic area. Dobutamine infusion and exercise radionuclide ventriculography detected 7 and 6 of these 10 patients implying the presence of jeopardized myocardium in infarcted/peri-infarct area. Dobutamine stress radionuclide ventriculography is an acceptable alternative to exercise testing to stratify risk following acute myocardial infarction.