Optimal stage duration in dobutamine stress echocardiography

Inotropic and lusitropic effects of incremental doses of dobutamine in dogs with right ventricular apical pacing-induced cardiac dysfunction

This study aimed to assess the effects of incremental doses of dobutamine on diastolic function in healthy and rapid ventricular apical pacing (RVAP)-induced cardiac dysfunction anesthetized dogs. Inotropic and lusitropic effects of dobutamine (2, 4, 8, and 12 μg kg^-1  min^-1 ) were assessed through left ventricle (LV) pressure-volume relation and Doppler echocardiography in six female dogs before and after 8 weeks of RVAP. Peak rate of LV pressure fall (-dP/dt_min ) improved with doses >4 μg kg^-1  min^-1 in healthy (4,490 ± 970 vs. 3,265 ± 471 mmHg/s, p < 0.05) and >8 μg kg^-1  min^-1 in RVAP dogs (3,385 ± 1,122 vs. 1,864 ± 849 mmHg/s, p < 0.05) while the time constant of relaxation (tau) reduced with doses >4 μg kg^-1  min^-1 in both groups (healthy: 24.0 ± 3.7 vs. 28.2 ± 4.9 ms; RVAP: 32.6 ± 8.5 vs. 37.5 ± 11.4 ms, p < 0.05) comparing with baseline. Indices of relaxation (-dP/dt_min and tau) suggested preserved lusitropic response in contrast with markedly reduced indices of contractility in the RVAP group compared with healthy group at same infusion rates. Doppler echocardiography showed significant reduction of elastic recoil in failing hearts. The results of this study demonstrated maximal positive lusitropic effects of dobutamine at a dose of 8 μg kg^-1  min^-1 in ventricular pacing-induced cardiac dysfunction without further impairment of ventricular filling.

Accelerated dobutamine stress testing: safety and feasibility in patients with known or suspected coronary artery disease

BACKGROUND

Dobutamine pharmodynamics require approximately 10 min to reach steady state. Despite this, standard dobutamine stress echo typically uses 3-min stages of advancing dobutamine doses because of safety concerns.

HYPOTHESIS

In patients with a high pretest probability of coronary artery disease (CAD), a continuous infusion of high-dose dobutamine is a feasible and safe method for performing a dobutamine stress test.

METHODS

Forty-seven consecutive patients (mean age 64 +/- 11 years) with 3.0 +/- 1.4 cardiac risk factors underwent dobutamine stress testing utilizing a single, high-dose (40 mcg/kg/min), continuous dobutamine infusion. The 40 mcg/kg/min infusion was continued for up to 10 min or until a test endpoint had been reached. If a test endpoint was not achieved, atropine (up to 1.0 mg) was added.

RESULTS

Heart rate rose from 71 +/- 12 to 137 +/- 18 beats/min at peak (p<0.0001) with a concomitant change in systolic blood pressure (143 +/- 35 vs. 167 +/- 38 mmHg; p = 0.001) but no change in diastolic blood pressure (74 +/- 19 vs. 75 +/- 18 mmHg; p = NS). Target heart rate was achieved in 20 of 47 (43%) patients with accelerated dobutamine alone and in 34 of 47 (72%) with the addition of atropine. An average of 11.6 +/- 3.7 min was required to obtain target heart rate. Subjective sensations from the dobutamine occurred in 49% of patients (palpitations 21%, nausea 6%, chest pain 6%, headache 6%, dizziness 13%), mild arrhythmia in 48% of patients (ventricular premature beats 38%, supraventricular tachycardia 10%), and one patient had nonsustained ventricular tachycardia.

CONCLUSION

A single, high-dose (40 mcg/kg/min) dobutamine-atropine protocol provides an efficient means of performing dobutamine stress echocardiography with a similar symptom profile as conventional dobutamine infusion protocols in patients with a high pretest probability of CAD. Randomized, controlled studies will be necessary to assess the sensitivity and specificity of this accelerated dobutamine echo protocol.

Feasibility, safety and tolerability of accelerated dobutamine stress echocardiography

A continuous infusion of a single high dose of dobutamine has been, recently, suggested as a simple and effective protocol of stress echocardiography. The present study assesses the feasibility, safety, and tolerability of an accelerated dobutamine stress protocol performed in patients with suspected or known coronary artery disease. Two hundred sixty five consecutive patients underwent accelerated dobutamine stress echocardiography: the dobutamine was administered at a constant dose of 50 μg/kg/min for up to 10 minutes. The mean weight-adjusted cumulative dose of dobutamine used was 330 ± 105.24 μg/kg. Total duration of dobutamine infusion was 6.6 ± 2.1 min. Heart rate rose from 69.9 ± 12.1 to 123.1 ± 22.1 beats/min at peak with a concomitant change in systolic blood pressure (127.6 ± 18.1 vs. 167.6 ± 45.0 mmHg). Dobutamine administration produced a rapid increase in heart rate (9.4 ± 5.9 beats/min²). The side effects were similar to those described with the standard protocol; the most common were frequent premature ventricular complexes (21.5%), frequent premature atrial complexes (1.5%) and non sustained ventricular tachycardia (1.5%); among non cardiac symptoms the most frequent were nausea (3.4%), headache (1.1%) and symptomatic hypotension (1.1%). No major side effects were observed during the test. Our data demonstrate that a continous infusion of a single high dose of dobutamine is a safe and well tolerated method of performing stress echocardiography in patients with suspected or known coronary artery disease. This new protocol requires the administration of lower cumulative dobutamine dose than standard protocol and results in a significant reduction in test time.

Determining myocardial viability in chronic ischemic left ventricular dysfunction: a prospective comparison of rest-redistribution thallium 201 single-photon emission computed tomography, nitroglycerin-dobutamine echocardiography, and intracoronary myocardial contrast echocardiography

BACKGROUND

Detection of viable myocardium (VM) has important therapeutic implications for chronic ischemic left ventricular (LV) systolic dysfunction. We compared the ability of nitroglycerin-dobutamine echocardiography (NTG-DE), intracoronary myocardial contrast echocardiography (MCE), and rest-redistribution thallium 201 single-photon emission computed tomography (RRT-SPECT) to detect VM in this setting.

METHODS

Patients with LV ejection fraction (LVEF) <40% and multivessel coronary disease suitable for revascularization underwent NTG-DE, MCE, RRT-SPECT, and radionuclide ventriculography to determine baseline LVEF. Myocardial contrast echocardiography was performed using intracoronary injection of Albunex. Patients who underwent revascularization had 3-month postprocedural radionuclide ventriculography and transthoracic echocardiography to assess functional recovery.

RESULTS

Of 512 myocardial segments in the 32 patients studied, 309 were akinetic or dyskinetic at baseline. Nitroglycerin alone increased regional thickening in 20% of segments with contractile reserve. By RRT-SPECT, 93% of nitroglycerin-responsive segments were viable. Myocardial contrast echocardiography had up to 85% sensitivity and 74% specificity for detection of VM diagnosed by RRT-SPECT. In the 23 patients who underwent revascularization, 54% of akinetic segments showed improved contractility, and mean LVEF increased from 32% to 37% (P = .04). Sensitivities and specificities for detecting functional recovery were 95% and 37% for RRT-SPECT, up to 87% and 48% for MCE, and 63% and 83% for a biphasic response during NTG-DE.

CONCLUSIONS

In patients with chronic ischemic LV dysfunction, RRT-SPECT had the highest sensitivity, and NTG-DE, the best specificity for detection of VM. Nitroglycerin facilitated detection of VM and may be a useful adjunct to dobutamine stimulation.

Prognostic usefulness of echocardiographic dobutamine in younger (14 to 25 years) and older (40 to 55 years) patients with idiopathic dilated cardiomyopathy

We studied 16 younger patients (<25 years old) and 16 older patients (>40 years old) to investigate the prognostic value of echocardiographic dobutamine-induced changes. The results of this study showed that although the percent achieved of predicted oxygen consumption was lower in the younger group, no prognostic information was given regarding the outcome of this particular group. In contrast, echocardiographic dobutamine-induced changes can distinguish high-risk younger patients.

Effects of dobutamine on left ventricular shape and geometry: an easy way to detect the functional status of chronic heart failure in patients with dilated cardiomyopathy

OBJECTIVE

Changes in left ventricular geometry and shape are prominent characteristics of cardiomyopathy. The aim of this study was to investigate left ventricular geometry and shape changes after inotropic stimulation in patients with chronic nonischemic dilated cardiomyopathy.

METHODS

A low infusion rate echocardiography-dobutamine study was performed in 35 consecutive patients (age: 50 +/- 8 years) with known dilated cardiomyopathy. Peak exercise oxygen consumption was measured the day before. Overall left ventricular chamber shape was assessed by using the long-/minor-axis dimension ratio obtained at end-diastole and end-systole.

RESULTS

After dobutamine infusion, in the entire study group an increase in systolic long-/minor-axis dimension ratio (0.11 +/- 0.13 mm, P <.001) was observed. The study population was further divided according to whether peak exercise oxygen consumption was less (group I) or more (group II) than 14 mL/kg/min. Although at baseline systolic long-/minor-axis dimension ratio was similar between groups, after dobutamine infusion it was higher in group II (1.51 +/- 0.19) than in group I (1.31 +/- 0.2, P <.01) indicating the abnormal response of systolic sphericity index to inotropic stimulation in patients with advanced functional class heart failure.

CONCLUSION

The response of systolic sphericity index to dobutamine infusion might be an alternative index of the functional status of the failing heart in patients with nonischemic dilated cardiomyopathy.

Left atrial functional reserve in patients with nonischemic dilated cardiomyopathy: an echocardiographic dobutamine study

OBJECTIVE

To evaluate left atrial functional reserve in patients with chronic heart failure and nonischemic dilated cardiomyopathy (DCM).

BACKGROUND

Left ventricular functional status has been investigated using echocardiographic dobutamine.

METHODS

In 35 consecutive patients (29 men and 6 women; mean +/- SD age, 42.37 +/- 13.5 years), peak oxygen consumption (O(2)max) was measured; the day after, a low-dose dobutamine (5 to 10 micro g/kg/min, of 5 min each step) study was performed. Left atrial volumes at mitral valve opening, onset of left atrial systole, and mitral valve closure were measured by using two-dimensional echocardiography. Left atrial active emptying volume (LAEV) [volume at onset of atrial systole - minimal volume] was calculated, as was left atrial active emptying fraction (LAEF): [(volume at onset of atrial systole - minimal volume)/volume at onset of atrial systole] x 100. The changes (values obtained after inotropic stimulation minus those obtained at baseline) of the above-mentioned echocardiographic variables were considered as left atrial functional reserve.

RESULTS

In the entire study group after dobutamine infusion, increases in LAEV (3.34 +/- 7.54 mL, p = 0.01) and LAEF (6 +/- 13.2%, p = 0.01) were observed. The changes in the above-mentioned parameters were correlated with O(2)max values (r = 0.73 and r = 0.71, respectively; p < 0.001). After inotropic stimulation, LAEV and LAEF were increased in patients with O(2)max values > 14 mL/kg/min (5.62 +/- 7.28 mL and 10.04 +/- 13.13%, respectively) and decreased in patients with O(2)max values < 14 mL/kg/min (- 1.08 +/- 6.13 mL and - 1.6 +/- 9.9%, respectively; p = 0.01 for both).

CONCLUSION

Echocardiographic dobutamine can evaluate left atrial functional reserve in patients with nonischemic DCM.

Myocardial texture analysis in idiopathic dilated cardiomyopathy: prediction of contractile reserve on dobutamine echocardiography

Conventional resting echocardiography is not able to predict contractile reserve (CR) of patients with idiopathic dilated cardiomyopathy. The aim of this study was to investigate whether the videodensitometric myocardial texture analysis could predict the CR of these patients. Myocardial texture analysis was performed on echocardiographic digitized images of 27 patients with IDC through a calibrated 256 gray level digitization system. Cyclic variation (CV) index of myocardial mean gray level (MGL) was calculated according to the formula: (MGL(diast) - MGL(syst))/ MGL(diast) x 100. CR was defined as the %-change of ejection fraction by 10 microg/kg per minute dobutamine infusion. A clinical follow-up was also performed for all patients for an average of 8 +/- 3 months. CR ranged from -1.8% to 50.3%. CV index of both septum and posterior wall (PW) was the single parameter significantly correlated to CR (r = 0.69 and r = 0.77, respectively, P <.0001 for both). The mean resting CV index of septum and PW were significantly lower in patients with CR less than 17%-median value of all subjects-(5.7 +/- 5.6 vs 16.9 +/- 7.9 and 5.4 +/- 5.9 vs 16.1 +/- 6.4, respectively, P <.0001 for both). A CV index of 10% for both septum and PW yielded a sensitivity of 77% and 84%, and a specificity of 84% and 84% for predicting diminished CR, respectively. The event-free survival rate was significantly lower in patients with CR less than 17% (61.5% vs 92.8%, P <.05). The CV index of both septum and PW were also significantly lower in patients with cardiac events (13.6 +/- 8 vs 4.3 +/- 6, P <.05 and 14.7 +/- 7 vs 4.1 +/- 7, P <.01, respectively). Ultrasonic myocardial texture analysis in idiopathic dilated cardiomyopathy has a high ability to discriminate the patients with and without preserved CR, and patients with unfavorable outcome as well.

Dobutamine echocardiographic study in patients with nonischemic dilated cardiomyopathy and prognostically borderline values of peak exercise oxygen consumption: 18-month follow-up study

OBJECTIVES

We sought to study the prognostic value of dobutamine echocardiography in patients with nonischemic dilated cardiomyopathy (DCM) and prognostically borderline values of peak oxygen consumption (VO2max) during exercise.

BACKGROUND

Changes in echocardiographic variables assessed by dobutamine echocardiography can be used to evaluate the functional status of patients with chronic heart failure (CHF) and DCM.

METHODS

In 27 consecutive patients (mean age 55 +/- 15 years) with VO2max values between 10 and 14 ml/kg body weight per min, a low infusion rate (10 microg/kg per min) dobutamine echocardiographic test was performed. The induced changes in echocardiographic variables were measured, and an 18-month follow-up study was done.

RESULTS

At the end of the protocol, 9 patients (group I) had died from cardiac reasons, whereas the remaining 18 patients (group II) survived. After dobutamine infusion, the left ventricular end-systolic diameter (LVESD) was smaller in group II (6.22 +/- 0.94 cm) than in group I (6.99 +/- 0.76 cm; p < 0.05), whereas end-systolic wall stress (ESWS) was higher in group I (1030.66 +/- 193.98 g/cm2) than in group II (691.57 +/- 297.06 g/cm2; p < 0.05). The changes in LVESD and ESWS were greater in group I (0.75 +/- 0.36 cm and 463.11 +/- 159.87 g/cm2, respectively) than in group II (-0.04 +/- 0.36 cm and 83.16 +/- 291.74 g/cm2, respectively; p < 0.01 for both).

CONCLUSIONS

In the "gray" zone of VO2max, dobutamine echocardiography seems to be a valuable prognostic indicator in patients with CHF and DCM.

Safety and efficacy of an accelerated dobutamine stress echocardiography protocol in the evaluation of coronary artery disease

Although dobutamine requires up to 10 minutes to achieve steady state, dobutamine stress echocardiography is routinely performed using stepwise increments at 3-minute intervals. Consequently, the full effect of any infusion rate is not attained before the dobutamine dose is advanced to the next level. This study sought to test the safety and efficiency of high-dose continuous dobutamine infusion. One hundred consecutive patients underwent an accelerated protocol using a constant infusion of 50 microg/kg/min. In the absence of a stress echocardiographic end point (>/=85% of maximal predicted heart rate, new wall motion abnormalities, hypotension, arrhythmia, or intolerable symptoms), dobutamine infusion was discontinued at 10 minutes. Hemodynamic responses and adverse effect profile were compared with 100 patients who underwent a standard stepwise dobutamine stress protocol. Peak heart rate (140 +/- 16 vs 140 +/- 19 beats/min, p = 0.95) and systolic blood pressure (169 +/- 32 vs 162 +/- 31 mm Hg, p = 0.08) were similar in both protocols. Accelerated dobutamine administration produced a rapid increase in heart rate (12.5 +/- 6.2 vs 5.7 +/- 2.6 beats/min, p <0.001), and a substantial reduction in test duration (6.4 +/- 2.4 vs 12.9 +/- 3.0 minutes, p <0.001). The mean weight-adjusted cumulative dobutamine dose was lower in the accelerated protocol group (320 +/- 111 vs 353 +/- 133 microg/kg, p = 0.016). No significant differences were noted between the 2 groups with respect to various side effects. These data demonstrate that a high-dose, single-stage dobutamine echocardiographic stress protocol is a feasible, well-tolerated alternative to standard dobutamine stress echocardiography, and results in a substantial reduction in test time while maintaining a low complication rate.

Diagnostic and prognostic value of serial dobutamine stress echocardiography for noninvasive assessment of cardiac allograft vasculopathy: a comparison with coronary angiography and intravascular ultrasound

BACKGROUND

Routine methods for surveillance of cardiac allograft vasculopathy (CAV) are coronary angiography and intravascular ultrasound (IVUS). This study analyzed the diagnostic and prognostic value of dobutamine stress echocardiography (DSE) for noninvasive assessment of CAV.

METHODS AND RESULTS

In 109 heart transplant recipients, 333 DSEs were compared with 285 coronary angiograms and 199 IVUS analyses. Studies were repeated after 1, 2, 3, 4, and >/=5 years in 88, 74, 37, 18, and 7 patients, respectively. Resting 2D echocardiography detected CAV defined by IVUS and angiography with a sensitivity of 57% (specificity 88%). DSE increased the sensitivity to 72% (P=0.002). M-mode analysis increased the sensitivity of 2D rest and stress analysis (P=0.001, 0.004). Cardiac events occurred after 1.9% of normal stress tests by 2D analysis (combined 2D and M-mode: 0%), compared with 6.3% (3.8%) of normal resting studies. Worsening of serial DSE indicated an increased risk of events compared with no deterioration (relative risk 7.26, P=0.0014). Serial deterioration detected by stress only was associated with a higher risk of events than changes evident from resting studies (relative risk 3.06, P=0.0374).

CONCLUSIONS

DSE identifies patients at risk for events and facilitates monitoring of CAV. A normal DSE predicts an uneventful clinical course and justifies postponement of invasive studies. The prognostic value of DSE is comparable to that of IVUS and angiography.

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.

Usefulness of low-dose dobutamine stress echocardiography in predicting recovery of poor left ventricular function in atrial fibrillation dilated cardiomyopathy

Assessment of contractile reserve was performed in 16 patients with dilated cardiomyopathy and chronic atrial fibrillation. In this prospective study, low-dose dobutamine echocardiography could predict recovery of left ventricular dysfunction and could identify tachycardiomyopathy before restoration of sinus rhythm.

Breath-hold dobutamine magnetic resonance myocardial tagging: normal left ventricular response

Analysis of the changes in myocardial deformation produced by adrenergic stress has been limited by the imaging techniques used. We used rapid magnetic resonance imaging (MRI) myocardial tagging to map the dose-dependent response to incremental dobutamine in the normal human left ventricle. Thirteen volunteers underwent breath-hold tagged cine MRI during dobutamine infusion. Images were acquired throughout systole to a peak dose of 20 microg/kg/min. End-systolic percent circumferential shortening (%S) was measured at 3 transmural locations and 4 circumferential locations at 3 long-axis positions. Mean circumferential shortening velocity (CSV) was also calculated at each location and dose. Mean %S reached a maximum of 26 +/- 3% at 10 microg/kg/min compared with 21 +/- 4% at baseline (p <0.003). Peak %S was reached by 10 microg/kg/min before a significant increase in heart rate or blood pressure and was unchanged at higher doses. In contrast, CSV increased linearly with dobutamine dose from 4.4 +/- 0.9 mm/s at baseline to 9.8 +/- 1.4 mm/s at 20 microg/kg/min (p <0.0001). Breath-hold tagged dobutamine MRI is safe and effective in detecting regional and transmural changes in function during incremental dobutamine. CSV increased continuously across the dobutamine dose range. At low dose (< or =10 microg/kg/min) %S increased without any change in blood pressure or heart rate. Maintenance of peak %S beyond 10 microg/kg/min in the presence of decreasing systolic intervals resulted from a continued increase in CSV. Thus, CSV may be the preferred measure of contractile function during dobutamine stimulation in human myocardium.

Hemodynamic changes, plasma catecholamine responses, and echocardiographically detected contractile reserve during two different dobutamine-infusion protocols

We studied hemodynamic changes, catecholamine responses, and the occurrence of improved wall thickening by echocardiography during two different dobutamine-infusion protocols. Forty-three patients were studied by using a stepwise incremental dobutamine dose-infusion protocol (10-40 microg/kg/min, 3-min intervals); a subgroup of 11 patients also underwent a continuous dobutamine-infusion protocol (10 microg/kg/min for 12 min) in random order. No patient used beta-blockers. At 3-min intervals, blood pressure, heart rate, and plasma concentrations of dobutamine, epinephrine, and norepinephrine were measured. The echocardiographic improvement of wall thickening was analyzed only in paired protocols by visual assessment in left ventricular regions with normal wall motion at rest. The mean heart rate increased in the continuous and stepwise protocols from 73 to 99 and 74 to 132 beats/min. There was no significant change in blood pressure response between the two protocols. The mean plasma dobutamine concentrations during the continuous and stepwise protocols at 0, 3, 6, 9, and 12 min were 0/0; 31/38; 80/203; 106/448; and 120/692 ng/ml, respectively. In each patient, a response curve was constructed for the plasma dobutamine concentration versus heart rate. The heart rate increment and dobutamine concentration at which wall thickening was detected were similar with both protocols (14 +/- 5 vs. 12 +/- 7 beats/min) and (80 +/- 40 vs. 92 +/- 48 ng/ml; mean +/- SD). Wall thickening was noted in two of 11 patients between 0 and 3 min and 11 of 11 patients between 3 and 6 min in both protocols. Catecholamine responses during the continuous and stepwise protocols were epinephrine, 23 versus 28/28 versus 36, and norepinephrine 301 versus 323/347 versus 519. Only norepinephrine plasma concentrations increased significantly during the stepwise protocol. A 6-min dobutamine infusion was sufficient during both protocols to reach an adequate plasma dobutamine concentration, which induced a detectable increase of wall thickening in all patients. There is a significant differences between the two protocols with regard to the plasma catecholamine changes, so some of the hemodynamic effects during the stepwise dobutamine-infusion protocol may be mediated through release of endogenous catecholamines.

Effects of prolonging peak dobutamine dose during stress echocardiography

OBJECTIVES

This study sought to test whether the physiologic advantage of a prolonged dobutamine stage during stress echocardiography can be effectively combined with a clinically practical infusion protocol.

BACKGROUND

Dobutamine has a half-life of 2 min and requires up to 10 min to achieve steady state. Despite these known pharmacodynamics, dobutamine stress echocardiography is routinely performed by advancing doses at 3-min intervals. Canine studies have shown that dobutamine stress echocardiography end points will occur at a lower dose if each stage is prolonged, but these findings have yet to be used in the clinical setting.

METHODS

The standard 3-min dobutamine dose stage during stress echocardiography was modified by extending the peak dose (40 micrograms/kg body weight per min) for an additional 2 min. Consecutive patients underwent this modified protocol to test whether the requirement for atropine could be reduced. According to this modified protocol, if a dobutamine stress echocardiographic end point (85% of maximal predicted heart rate, new wall motion abnormalities, hypotension, arrhythmia or intolerable symptoms) was not reached at 3 min of the peak dose, this dose was prolonged for an additional 2 min. If a doubtamine stress echocardiographic end point was still not attained, atropine (up to 1.0 mg intravenously) was administered.

RESULTS

The study included 84 patients, 22 of whom (26.2%) achieved a dobutamine stress echocardiographic end point using the standard 3-min stage. Of the 62 patients who did not reach an end point in the initial 3 min of peak dobutamine dose, the additional 2 min of dobutamine increased heart rate (from 99.6 +/- 23.8 to 107.2 +/- 23.2 beats/min, p < 0.01) and allowed 20 patients (32.3%, p < 0.01) to attain an end point. Of the remaining 42 patients, 23 never achieved a stress echocardiographic end point, despite 1.0 mg of atropine. One patient developed supraventricular tachycardia during the additional 2 min of dobutamine, and one developed nonsustained ventricular tachycardia after receiving atropine.

CONCLUSIONS

These data demonstrate that a significant number of patients (32%) who do not reach a dobutamine stress echocardiographic end point with the standard protocol can safely attain an end point solely by extending the duration of the peak dose. Adoption of this strategy may reduce the need for supplemental atropine and its potential adverse effects.

Factors influencing regional myocardial contractile response to inotropic stimulation. Analysis in humans with stable ischemic heart disease

BACKGROUND

We hypothesized that the response of a myocardial segment to maximal dobutamine reflects not only maximal blood flow but also tethering, metabolic, and beta-blocker status.

METHODS AND RESULTS

Patients with stable ischemic heart disease (n = 27) had positron emission tomographic measurement of blood flow at rest and with adenosine, and echocardiography at rest and with dobutamine. Positron emission tomographic measurement of [18F]fluorodeoxyglucose myocardial distribution also was made. Adenosine blood flow in segments that contracted normally at peak dobutamine was similar to that of segments that became hypokinetic (1.06 +/- 0.72 versus 1.02 +/- 0.77 mL.g-1.min-1). Segments that became akinetic failed to augment blood flow (0.68 +/- 0.30 mL.g-1.min-1). Fluorodeoxyglucose-blood flow mismatch was more common in segments with abnormal wall motion at peak dobutamine (24 of 59, 41%) versus those that contracted normally (63 of 269, 23%; chi 2, 7.40; P < .01). In patients off beta-blockers, segments that contracted normally at peak dobutamine increased blood flow with adenosine (0.70 +/- 0.31 to 0.86 +/- 0.46 mL.g-1.min-1; P < .05), whereas those that became abnormal did not (0.63 +/- 0.24 to 0.65 +/- 0.19 mL.g-1.min-1; P = NS). Segments of patients on beta-blockers that contracted normally at peak dobutamine increased blood flow with adenosine (0.78 +/- 0.31 to 1.10 +/- 0.70 mL.g-1.min-1; P < .05), as did segments that became abnormal (0.74 +/- 0.34 to 1.06 +/- 0.82 mL.g-1.min-1; P = NS). However, segments adjacent to ones with abnormal wall motion at rest had higher frequency of abnormal response at peak dobutamine in groups on (48% versus 16%; chi 2, 14.1; P < .001) and off (51% versus 21%; chi 2, 10.9; P < .01) beta-blockers.

CONCLUSIONS

Augmented contraction at maximal dobutamine depends not only on increased myocardial blood flow but also on tethering, metabolic, and beta-blocker status. Furthermore, impaired flow reserve does not preclude a normal response to maximal dobutamine, since blood flow need not increase greatly to meet demand.

Effect of beta-blockade on dobutamine stress echocardiography

Dobutamine is an effective pharmacologic stress used in conjunction with echocardiography because of its beta-agonist properties. Concurrent beta-blockade might alter this effectiveness; however, current clinical experience has been variable. The purpose of this study is to determine whether concurrent beta-blockade alters the ability of a dobutamine stress echocardiogram to detect a fixed coronary stenosis by preventing the onset of a wall motion abnormality or by altering the dose at which the wall motion abnormality appears. Paired dobutamine stress tests with and without beta-blockade (esmolol 500 microgram/kg initial bolus, 100 microg/kg/min infusion) were performed in a canine model (n = 8) with a fixed single-vessel coronary stenosis. Heart rate, systolic pressure, proximal left anterior descending coronary flow, myocardial thickening (by sonomicrometry), and left ventricular area change (by epicardial echocardiography) were monitored. Simultaneous beta-blockade resulted in (1) a delayed and diminished increase in hemodynamic parameters (peak heart rate 164.1 +/- 22.3 without beta-blockade vs 110.1 +/- 28.9 beats/min with beta-blockade, p < 0.001, and peak systolic blood pressure 137.9 +/- 26.8 mm Hg without beta-blockade vs 107.3 +/- 15.3 mm Hg with beta-blockade, p = 0.01), (2) an elimination of the physiologic effects of low-dose (5 and 10 microg/kg/min) dobutamine (-0.7 percent +/- 16.7 percent change in myocardial thickening from baseline with beta-blockade, p = NS), and (3) an elimination or alteration in timing of inducible wall motion abnormalities caused by severe coronary artery stenoses (mean termination dose 28.8 +/- 9.9 with beta-blockade vs 15.6 +/- 6.1 microg/kg/min without beta-blocker, p < 0.01). The findings in this canine model suggest that the competitive antagonist markedly attenuates the ability of dobutamine stress echocardiography to detect a significant coronary lesion and may alter its ability to detect viable myocardium at low-dose testing. Further clinical studies to determine the sensitivity of dobutamine stress echocardiography in the presence of beta-blockers and to establish protocol standards are necessary.

Dobutamine-induced hypoperfusion without transient wall motion abnormalities: less severe ischemia or less severe stress?

OBJECTIVES

This study sought to compare the clinical characteristics, hemodynamic response and severity of ischemia in patients with coronary artery disease and reversible perfusion defects on dobutamine 2-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography (SPECT) with or without transient wall motion abnormalities.

BACKGROUND

The occurrence of reversible perfusion defects without concomitant wall motion abnormalities in patients with coronary artery disease was attributed to less severe ischemia. However, little data are available to support this observation.

METHODS

Fifty-four consecutive patients with significant coronary artery disease and reversible perfusion defects on dobutamine (up to 40 micrograms/kg body weight per min) MIBI SPECT were studied (mean [+/- SD] age 59 +/- 11 years; 38 men, 16 women). All patients underwent simultaneous echocardiography. The myocardium was divided into six matched segments, and ischemic perfusion score was quantitatively derived in myocardial segments with reversible defects.

RESULTS

New or worsening wall motion abnormalities occurred in 40 patients (74%) (group A) and were absent in 14 (26%) (group B). There was no significant difference between the two groups with respect to age, previous myocardial infarction, number of abnormal coronary arteries (1.8 +/- 0.8 vs. 1.6 +/- 0.9), number of reversible perfusion defects (1.6 +/- 0.9 vs. 1.8 +/- 0.7) or ischemic perfusion score (412 +/- 750 vs. 526 +/- 553). Patients in group A had a higher prevalence of male gender (80% vs. 43%, p < 0.01), higher peak systolic blood pressure (147 +/- 30 vs. 127 +/- 31 mm Hg, p < 0.05), higher peak rate-pressure product (19,632 +/- 4,081 vs. 16,939 +/- 4,344, p < 0.01) and a higher prevalence of angina (53% vs. 14%) and ST segment depression (55% vs. 14%) than group B (p < 0.05 for both).

CONCLUSIONS

In patients with coronary artery disease and ischemia on dobutamine MIBI SPECT, the absence of transient wall motion abnormalities is associated with a similar extent and severity of reversible perfusion defects, a lower stress rate-pressure product and a higher prevalence of female gender than patients with transient wall motion abnormalities. Mechanically silent ischemia should not be regarded as a marker of less severe ischemia on myocardial perfusion scintigraphy.