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

Absence of long-term incremental prognostic value of inducible wall motion abnormalities on dipyridamole stress CMR in patients with suspected or known coronary artery disease

OBJECTIVES

This single-center retrospective study evaluated the long-term (~5 years) prognostic value of dipyridamole stress cardiac magnetic resonance (CMR) in patients with known or suspected coronary artery disease (CAD), assessing the impact of both key phases of the ischemic cascade (perfusion and wall motion).

MATERIAL AND METHODS

We considered 322 consecutive patients who underwent dipyridamole stress CMR. Abnormal wall motion at rest and after dipyridamole, perfusion at stress and at rest, and late gadolinium enhancement (LGE) were analyzed. End-points were non-fatal myocardial infarction, unplanned late revascularization (60 days after CMR), and cardiac death.

RESULTS

Forty-four patients were excluded because they underwent early revascularization (within 60 days after stress CMR), leading to a final population of 278 patients (73 females, 62.42 ± 10.50 years). A positive stress CMR was found in 78 (28.1%) patients; 50 patients had a reversible stress perfusion defect in at least one myocardial segment and 28 had a reversible stress perfusion defect plus worsening of stress wall motion in comparison with the rest. During a mean follow-up time of 59.34 ± 31.72 months, 37 (13.3%) cardiac events were recorded: 10 cardiac deaths, one non-fatal myocardial infarction, and 26 late revascularization after unstable angina or myocardial infarction. According to the Cox regression analysis, age, diabetes mellitus, previous revascularization, left ventricular ejection fraction (LVEF), reversible perfusion and perfusion + motion defect, and LGE were significant univariate prognosticators. The presence of associated wall motion abnormality (WMA) did not provide additional prognostic stratification in comparison to the only perfusion defect. In the multivariate Cox regression, the independent predictive factors were diabetes (hazard-ratio-HR = 5.64, p < 0.0001), reversible perfusion defect and reversible perfusion + motion defect vs normal stress CMR (HR = 6.43, p < 0.0001, and HR = 4.57, p = 0.004; respectively), and LVEF (HR = 0.96, p = 0.010).

CONCLUSION

A positive dipyridamole stress CMR predicted a higher long-term risk of cardiovascular events, but the presence of inducible WMA did not show any additional prognostic value over the reversible perfusion defect.

KEY POINTS

Question The long-term incremental prognostic value of inducible wall motion abnormalities by stress cardiac MR in patients with known or suspected CAD requires investigation. Findings The presence of inducible wall motion abnormalities did not offer additional prognostic value in comparison to the only reversible perfusion defect. Clinical relevance Independent from the presence of wall motion abnormalities, more aggressive management may be appropriate in patients with reversible perfusion defects to reduce the long-term risk of cardiovascular events.

Diagnostic Approach to Patients with Stable Angina and No Obstructive Coronary Arteries

The diagnosis of microvascular angina (MVA) is usually considered in patients presenting with angina symptoms and evidence of MI on non-invasive stress tests but normal coronary arteries at angiography. A definitive diagnosis of MVA, however, would require the presence of coronary microvascular dysfunction. Several invasive (e.g. intracoronary Doppler wire recording and thermodilution) and non-invasive (e.g. PET, cardiac MRI, transthoracic Doppler echocardiography) methods can be applied to obtain a diagnosis. Both endothelium-dependent and -independent coronary microvascular dilator function, as well as increased microvascular constrictor activity, should be investigated. The main issues in the assessment of clinical and diagnostic findings in patients with suspected MVA are discussed and a diagnostic approach is suggested.

Cardiac stress imaging for the prediction of very long-term outcomes: Dobutamine stress echocardiography or dobutamine 99mTc-sestamibi SPECT?

BACKGROUND

Both dobutamine stress echocardiography (DSE) and myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) are frequently used for cardiac risk stratification. The long-term relative prognostic value of these modalities has not been studied. Therefore, this study evaluated the long-term prognostic value of DSE compared to MPI in patients unable to perform exercise testing.

METHODS

This prospective, single center study included 301 patients (mean age 59 ± 12 years, 56% men) unable to perform exercise tests who underwent DSE and dobutamine stress 99mTc-sestamibi MPI. End points during follow-up were all-cause mortality, cardiac mortality, and nonfatal myocardial infarction (MI). Univariable and multivariable Cox proportional hazards regression models were used to identify independent predictors of outcome. The probability of survival was calculated using the Kaplan-Meier method.

RESULTS

A total of 182 patients (60%) had an abnormal DSE and 198 (66%) patients had an abnormal MPI. The agreement between DSE and MPI was 82% (κ = 0.62). During a median follow-up of 14 years (range 5-18), 172 deaths (57%) occurred, of which 72 (24%) were due to cardiac causes. Nonfatal MI occurred in 46 patients (15%). The multivariable analysis demonstrated that an abnormal DSE was a significant predictor of cardiac mortality (HR 2.35, 95% CI [1.17-4.73]) and hard cardiac events (HR 2.11, 95% CI [1.25-3.57]). Also, an abnormal MPI result was a significant predictor of cardiac mortality (HR 3.03, 95% CI [1.33-6.95]) and hard cardiac events (HR 2.06, 95% CI [1.12-3.79]).

CONCLUSIONS

DSE and MPI are comparable in predicting long-term cardiac mortality and hard cardiac events in patients unable to perform exercise testing.

Prognostic value of dipyridamole stress cardiac magnetic resonance in patients with known or suspected coronary artery disease: a mid-term follow-up study

OBJECTIVES

Dipyridamole stress cardiac magnetic resonance (CMR) evaluates the key phases (perfusion and wall motion) of the ischemic cascade. We sought to determine the prognostic value of dipyridamole stress-CMR in consecutive patients symptomatic for chest pain.

METHODS

Seven hundred and ninety-three consecutive patients symptomatic for chest pain underwent dipyridamole stress-CMR and were followed up for 810 ± 665 days. Patients were classified in group 1 (no- reversible ischemia), group 2 (stress perfusion defect alone), and group 3 [stress perfusion defect plus abnormal wall motion (AWM)]. End points were "all cardiac events" (myocardial infarction, cardiac death and revascularization) and "hard cardiac events" (all cardiac events excluding revascularization).

RESULTS

One hundred and ninety-five (24 %) all cardiac events and 53 (7 %) hard cardiac events were observed. All and hard cardiac event rates in groups 1, 2, and 3 were 11 %, 49 %, 69 % and 4 %, 8 %, 21 %, respectively, with a higher rate in group 2 vs. group 1 (p<0.01) and group 3 vs. groups 1 and 2 (p<0.01). Multivariate analysis showed the presence of late gadolinium enhancement and stress perfusion defect plus AWM as independent predictors of all and hard cardiac events.

CONCLUSIONS

Dipyridamole stress-CMR improves prognostic stratification of patients through differentiation between the different components of the ischemic cascade.

KEY POINTS

• Dipyridamole stress cardiac magnetic resonance helps to assess coronary artery disease. • Novel technique to study the key phases of myocardial ischemia. • Combined assessment of perfusion and motion defects. • Dipyridamole stress imaging has additional value for predicting cardiac events.

Detection of subendocardial ischemia in the left anterior descending coronary artery territory with real-time myocardial contrast echocardiography during dobutamine stress echocardiography

OBJECTIVES

The purpose of this study was to test whether the transmural delineation of myocardial perfusion during dobutamine stress imaging with real-time myocardial contrast echocardiography (RTMCE) might permit visualization of dobutamine-induced subendocardial ischemia.

BACKGROUND

Significant coronary artery disease can be present despite normal transmural wall thickening (WT) responses during dobutamine stress echocardiography (DSE). One potential reason is dobutamine-induced recruitment of epicardial WT in the presence of subendocardial ischemia.

METHODS

Myocardial perfusion and WT were examined with RTMCE during DSE with a continuous infusion of ultrasound contrast in 94 patients with normal resting WT. Fifty-five of the patients had a >50% diameter stenosis in the left anterior descending coronary artery (LAD). The WT was visually assessed by a blinded reviewer at 2 time periods: initially after a high mechanical index impulse before myocardial contrast replenishment (MCR), and again during MCR. Subendocardial %WT was measured during MCR, if a subendocardial perfusion defect was visually evident, whereas transmural WT was quantified on the pre-MCR images.

RESULTS

Fifty patients (91%) with LAD stenoses exhibited a myocardial contrast defect at peak stress, with 45 defects being subendocardial. Transmural WT pre-MCR appeared normal in 35 of the 45 patients with subendocardial perfusion defects (78%). However, a subendocardial WT abnormality was apparent during MCR in 18 of these 35 patients, even though transmural WT was not different from the 17 patients with normal subendocardial WT (33 +/- 15% vs. 36 +/- 14%). Quantitative measurements of WT within the subendocardium were significantly less in the patients with visually evident subendocardial WT abnormalities, when compared with those who seemed to have normal WT during MCR (17 +/- 8% vs. 25 +/- 10%, p < 0.01).

CONCLUSIONS

In patients with significant LAD disease, RTMCE during DSE detects subendocardial ischemia even when transmural WT appears normal. Real-time myocardial contrast echocardiography should be the preferred ultrasound imaging method when using contrast to detect coronary artery disease during DSE.

Emerging cardiovascular imaging techniques to non-invasively detect coronary artery disease

The current reference standard for the non-invasive detection of coronary artery disease (CAD) in patients who present with symptoms suggestive of CAD is either an exercise or pharmacologic stress radionuclide examination. Although useful, this test is limited by its relatively poor spatial resolution, high cost and need for ionizing radiation. Alternative non-invasive tests that are now clinically available include rest or pharmacologic stress echocardiography, pharmacologic stress during magnetic resonance perfusion imaging and multislice computed tomographic coronary angiography. This paper will present the advantages and disadvantages of stress techniques, and new developments that will further improve the accuracy of these tests.

High thoracic epidural blockade increases myocardial oxygen availability in coronary surgery patients

BACKGROUND

High thoracic epidural techniques are increasingly being used in patients scheduled for cardiothoracic surgery, including coronary artery bypass grafting. In the present study, we evaluated the acute effects of the epidural blockade on myocardial oxygen availability by means of tissue oxygen pressure monitoring in patients submitted for surgical revascularization.

METHODS

Fifty adult patients were included in a prospective, randomized, double-blind study. After placement of an epidural catheter in thoracic space T1-T2, and under general anesthesia, 5-10 ml of either normal saline or 0.3% ropivacaine was injected through the epidural catheter. Hemodynamic parameters and the intramyocardial oxygen partial pressure were recorded before and 20 min after the epidural injection.

RESULTS

There were no demographic or hemodynamic differences between the groups before intervention. A significant increase in intramyocardial partial oxygen pressure was observed in the ropivacaine group (14.6 mmHg vs. 25.1 mmHg, P < 0.0005).

CONCLUSION

High thoracic epidural blockade with 5-10 ml of 0.3% ropivacaine increases myocardial oxygen availability in coronary diseased patients prior to surgical revascularization without deleterious hemodynamic disturbances.

New technologies applied to stress echocardiography: myocardial contrast echocardiography

The development of new echocardiographic contrast agents that can be injected intravenously and can opacify left-sided cardiac chambers has offered a contribution in the field of stress-echocardiography for two main reasons: (1) the improvement of visualization of the endocardial border and thus facilitating recognition of wall motion abnormalities during pharmacological stress or physical exercise; and (2) the obtaining of information on myocardial perfusion during stress examinations. This review will consider: (1) the improvement of diagnostic accuracy during pharmacological stress or physical exercise obtained with the administration of echo-contrast agents; (2) the results of major studies for comparison of the myocardial contrast echocardiography technique versus single-photon emission computed tomography (SPECT) and coronary angiography; (3) the added value for studying perfusion other than wall motion analysis during stress echo; and (4) the advantages and limitations of different stress modalities. New multicenter studies should now definitively clarify the choice of the best contrast agents and create protocols for myocardial contrast echocardiography using different methods of image acquisition in order to unify the diagnostic process before a 'label approved' for perfusion of contrast echocardiographic agents. Finally, caution should be considered when contrast agents are used in the acute phase of myocardial infarction or ischemia.

Value of dobutamine stress myocardial contrast perfusion echocardiography in patients with advanced liver disease

Although dobutamine stress echocardiography has been used for the preoperative evaluation of patients with advanced liver disease (ALD), no data exist regarding the value of myocardial perfusion imaging (MPI) with real-time myocardial contrast echocardiography (RTMCE) in this patient population. We sought to determine the value of MPI during dobutamine stress RTMCE for predicting prognosis in patients with ALD. We examined both wall motion and MPI in 230 patients with ALD who underwent dobutamine stress RTMCE using intravenous commercially available contrast agents (Optison, GE-Amersham, Princeton, NJ; or Definity, Bristol-Myers Squibb Medical Imaging, North Billerica, MA). The prognostic value of clinical variables, including the Model for End-Stage Liver Disease (MELD) score, and echocardiographic data were examined using a Cox Hazard model. The primary endpoint was mortality of all causes. Among the 85 patients who underwent orthotopic liver transplantation, 4 had abnormal MPI and 81 had normal perfusion. The hospital mortality rate was 50% (2/4) in patients with abnormal MPI and 2% (2/81) in patients with normal MPI (P = 0.01). Among patients with abnormal MPI, 1 died from myocardial infarction in the first postoperative day and the second 1 from hemorrhagic shock. During a median follow-up of 15 months, 53 (23%) patients died. The independent predictors of death were an age of > or = 65 yr (RR = 2.2; 95% confidence interval (CI) = 1.1-4.4; P = 0.03), MELD score of > or = 25 (RR = 3.2; 95% CI = 1.8-5.5; P < 0.0001), and abnormal MPI (RR = 2.4; 95% CI = 1.1-5.2; P = 0.02). The 2-yr mortality was 24% for patients with normal MPI and 45% for those with inducible MPI abnormalities (P = 0.003). In conclusion, MPI obtained by RTMCE appears to be a useful tool in predicting mortality in patients with ALD. Further studies are required to verify its independent value.

Assessment of myocardial perfusion with real-time myocardial contrast echocardiography: methodology and clinical applications

Real-time myocardial contrast perfusion imaging (RTMCI) with echocardiography is a promising technique for evaluation of patients with known or suspected coronary artery disease. The technique is based on the utilization of small (<10 mum) microbubbles, which are capable of crossing the pulmonary circulation after intravenous injection. Unlike radioactive isotopes, which are taken actively or diffuse passively in the myocytes, myocardial contrast agents remain extracellularly in the capillaries and present a measure of the myocardial capillary blood volume and microvascular integrity. RTMCI has been shown to be a safe and feasible method for the assessment of myocardial perfusion at rest and with pharmacologic stress. Recent studies have shown the value of RTMCI with dobutamine stress in improving overall and regional detection of coronary artery disease and detecting of abnormalities at submaximal stress, therefore improving sensitivity in patients who are unable to achieve the target heart rate. The advantages of the technique include the ability to assess perfusion at bedside in one setting, simultaneous assessment of myocardial function, shorter imaging time, no need for ionizing irradiation, immediate availability of the results, and the ability to determine the ischemic threshold. Recent studies have shown that RTMCI improves the prognostic utility of standard dobutamine stress in addition to wall motion analysis. Patients with normal perfusion had a better outcome than those with normal wall motion. The combination of abnormal wall motion and perfusion identified patients at greatest risk of death and nonfatal myocardial infarction. Perfusion abnormalities were also shown to predict short-term cardiac events in patients presenting to the emergency department with chest pain and no ST-segment elevation. Refinement of imaging techniques is expected to improve the specificity of RTMCI, particularly in differentiating true perfusion defects from artifacts. This review will discuss the physiologic basis, methodology, clinical utility, and limitations of RTMCI in the assessment of patients with known or suspected coronary artery disease.

Clinical and prognostic implications of angina pectoris developing during dobutamine stress echocardiography in the absence of inducible wall motion abnormalities

This study assessed the incidence, clinical correlates, and prognostic significance of angina during dobutamine stress echocardiography (DSE) in patients who did not have inducible wall motion abnormalities. We studied 2,117 patients (61 +/- 13 years of age; 1,149 men) who underwent large-dose DSE and had no new or worsening wall motion abnormalities during DSE. Follow-up events were hard cardiac events (cardiac death or nonfatal myocardial infarction) and myocardial revascularization. Angina was induced in 217 patients (10%) during stress. DSE was normal in 1,198 patients (57%), whereas 919 patients (43%) had fixed wall motion abnormalities. During a mean follow-up of 5.5 +/- 3.7 years, 143 patients (7%) died of cardiac causes and 78 (4%) had nonfatal myocardial infarction. Patients who developed angina during DSE were more likely to have a history of exertional angina (64% vs 16%, p <0.001) and had a higher wall motion score index at rest (1.29 +/- 0.5 vs 1.17 +/- 0.4, p = 0.01) compared with patients who did not have angina. Annual hard cardiac event rates were 2.2% in patients who had dobutamine-induced angina (DIA) and 2.1% in patients who did not (p = NS). Myocardial revascularization was performed more frequently in patients who had DIA than in those who did not (39% vs 14%, p <0.0001). In Cox's regression model, independent predictors of hard events were age (RR 1.03, 95% confidence interval [CI] 1.02 to 1.04), male gender (RR 1.6, 95% CI 1.1 to 2.2), smoking (RR 1.5, 95% CI 1.1 to 2.9), and wall motion score index at rest (RR 2.6, 95% CI 1.8 to 3.8). In conclusion, in patients who do not have ischemia by echocardiographic criteria during DSE, inducible angina pectoris is associated with a high incidence of revascularization during follow-up. However, the hard cardiac event rate does not differ in patients who develop DIA from those who do not.

Diagnostic Accuracy and Prognostic Value of Dobutamine Stress Myocardial Contrast Echocardiography in Patients with Suspected Acute Coronary Syndromes

BACKGROUND

Both early stress testing and cardiac troponin I (cTnI) measurements are useful in assessing the prognosis of patients with acute coronary syndrome (ACS). We sought to determine the accuracy and prognostic value of wall motion analysis (WMA) and myocardial perfusion analysis (MPA) with real-time myocardial contrast echocardiography (RTMCE) during dobutamine stress in this patient population.

METHODS

We performed dobutamine stress RTMCE to assess perfusion in 158 consecutive patients (mean age: 61 +/- 13 years) with chest pain and possible ACS. Of these, 119 had normal cTnI, while 39 had isolated elevations of cTnI (range: 0.5-9.0 ng/ml). Quantitative angiography was performed within 1 month of RTMCE in 61 patients. Patients were followed for 16 months (range: 6-46 months). Cardiac events included death, nonfatal myocardial infarction, recurrent unstable angina, or need for urgent revascularization.

RESULTS

The sensitivity, specificity, and accuracy of MPA for detecting a >50% coronary stenosis were 92%, 77%, and 88%, respectively, while they were 62%, 85%, and 67% for WMA. Three-year event-free survival was 87% in patients with negative WMA and MPA, 49% in those with positive WMA and MPA, and 51% in patients with negative WMA but positive MPA. Age-adjusted multivariate analysis demonstrated that the only independent predictors of cardiac events were a positive MPA (hazard ratio = 3.23; 95% CI = 1.23-8.49) and male sex (hazard ratio = 3.29; 95% CI = 1.21-8.97).

CONCLUSIONS

In patients suspected of having an ACS, RTMCE improved the accuracy of dobutamine stress echocardiography for detecting coronary artery disease, and was an independent predictor of outcome.

Comparative accuracy of real-time myocardial contrast perfusion imaging and wall motion analysis during dobutamine stress echocardiography for the diagnosis of coronary artery disease

OBJECTIVE

This study sought to compare the accuracy of myocardial contrast echocardiography (MCE) and wall motion analysis (WMA) during submaximal and peak dobutamine stress echocardiography (DSE) for the diagnosis of coronary artery disease (CAD).

BACKGROUND

The relative merits of MCE and WMA for the detection of CAD during DSE have not been studied in a large number of patients.

METHODS

We studied 170 patients who underwent dobutamine (up to 50 microg/kg/min)-atropine stress testing and coronary angiography. The WMA and MCE (using repeated boluses of Optison [Mallinckrodt, St. Louis, Missouri] or Definity [Bristol-Myers Squibb, New York, New York]) were performed at rest, at intermediate stress (65% to 75% of maximal heart rate), and at peak stress. The diagnosis of CAD (>/=50% stenosis in >/=1 coronary artery) was based on reversible wall motion and perfusion abnormalities.

RESULTS

Coronary artery disease was detected in 127 (75%) patients. Sensitivity of MCE was higher than that of WMA at maximal stress (91% vs. 70%; p = 0.001) and at intermediate stress (84% vs. 20%; p = 0.0001). Specificity was lower for MCE compared with WMA (51% vs. 74%; p = 0.01). Overall accuracy was higher for MCE than for WMA (81% vs. 71%; p = 0.01). Sensitivity for detection of CAD based on abnormalities in >/=2 vascular regions was higher for MCE than for WMA (67% vs. 28%; p < 0.01).

CONCLUSIONS

The majority of inducible perfusion abnormalities occur at an intermediate phase of the stress test, without wall motion abnormalities. Myocardial contrast echocardiography provides better sensitivity than WMA, particularly in patients with submaximal stress and in identifying patients with multivessel CAD.

Long-term prognostic value of dobutamine stress echocardiography compared with myocardial perfusion scanning in patients unable to perform exercise tests

PURPOSE

To compare the long-term prognostic value of dobutamine stress echocardiography and dobutamine stress single photon emission computed tomography (SPECT) in patients unable to perform an exercise test.

METHODS

We assessed the prognostic value of dobutamine stress technetium 99m ((99m)Tc)-sestamibi SPECT and dobutamine stress echocardiography in 301 patients who were unable to perform exercise tests. Outcomes during a mean (+/- SD) follow-up of 7.3 +/- 2.8 years were overall death, cardiac death, nonfatal myocardial infarction, and late (>60 days) coronary revascularization.

RESULTS

Abnormal myocardial perfusion was detected in 66% of patients (n = 198), while 60% (n = 182) had an abnormal stress echocardiogram; agreement was 82% (kappa = 0.62). During the follow-up period, 100 deaths (33%) occurred, of which 43% were due to cardiac causes. Nonfatal myocardial infarction occurred in 23 patients (8%), and 29 (10%) underwent late revascularization. With stress SPECT, annual event rates were 0.7% for cardiac death and 3.6% for all cardiac events after a normal scan, and 2.6% for cardiac death and 6.5% for all cardiac events after an abnormal scan (P <0.0001). For stress echocardiography, annual event rates were 0.6% for cardiac death and 3.3% for all cardiac events after a normal test, and 2.8% for cardiac death and 6.9% for all cardiac events after an abnormal test (P <0.0001).

CONCLUSION

Dobutamine stress (99m)Tc-sestamibi SPECT and dobutamine stress echocardiography provide comparable long-term prognostic information in addition to that afforded by clinical data.

Long-term prognosis after normal dobutamine stress echocardiography

Patients with normal dobutamine stress echocardiography (DSE) were shown to have a favorable outcome at an intermediate-term follow-up. However, there are scarce data regarding long-term survival after normal DSE. This study sought to assess the long-term outcome after normal DSE. We studied 401 patients (age 62 +/- 10 years, 264 men) who had a normal echocardiogram at rest and with high-dose dobutamine stress. End points during a mean follow-up of 5 +/- 1.7 years (minimum 3.5) were all-cause mortality and hard cardiac events (cardiac death and nonfatal myocardial infarction). During follow-up, 45 patients (11%) died due to various causes (cardiac death in 10 patients). Thirteen patients had nonfatal myocardial infarction (a total of 23 hard cardiac events). The annual mortality rate was 2% in the first 3 years and 2.4% between the fourth and sixth years. The annual hard cardiac event rate was 0.8% in the first 3 years and 1.7% between the fourth and sixth years. Predictors of mortality in a multivariate analysis model were advanced age (hazard ratio 1.2, 95% confidence interval CI 1.1 to 1.4) and higher heart rate at rest (hazard ratio 0.92, 95% confidence interval 0.85 to 0.99). Patients with normal DSE had excellent outcomes during the 3 years after the study. The cardiac event rate was higher between the fourth and sixth year; therefore, it may be useful to repeat the study after 3 years to reassess risk status.

Real-time perfusion imaging: a new echocardiographic technique for simultaneous evaluation of myocardial perfusion and contraction

Myocardial contrast echocardiography (MCE) with high acoustic energy and triggered harmonic imaging is the best established ultrasound technique to date for the assessment of myocardial perfusion. With this technique, however, the ultimate goal of MCE (noninvasive real-time simultaneous assessment of myocardial perfusion and function after an intravenous injection of microbubbles) is not met. Recently, technologic advances have enabled myocardial opacification to be visualized during low-energy real-time imaging. During real-time perfusion imaging, wall motion and myocardial perfusion may be assessed simultaneously, obviating the need of the presently time-consuming combination of different imaging modalities. When high-energy ultrasound bursts are periodically transmitted to produce bubble destruction during low-power imaging, the consecutive frames after destruction delineate the restoration of contrast intensity. Microbubble replenishment rate and peak intensity may be determined subsequently, and provide reliable quantitative parameters of regional microcirculatory flow. This review will introduce the modalities used for real-time perfusion imaging with focus on power pulse inversion imaging and quantitative analysis. Furthermore, we will describe the clinical role the technique may have in the identification of coronary artery disease, quantification of coronary stenosis severity, assessment of myocardial viability, determination of infarction size, and evaluation of reflow and no- or low-reflow after acute myocardial infarction.

Can CK-MB and cTn-I be detected in the peripheral circulation within the first 10 min of acute coronary ischemia?

There are approximately 4 million patients hospitalized with suspected acute coronary syndromes (ACS) annually. However, the current standard tools for assessing ACS in the Emergency Department are felt to have insufficient sensitivity and specificity. Animal studies have demonstrated that CK-MB and troponin-I are released in a biphasic pattern with an initial transient release which peaks and falls within the first 10 min of ischemia. We hypothesize that transient elevations of CK-MB and troponin-I can be detected in the peripheral circulation within the first 10 min of ischemia in a human model of brief coronary ischemia. We also present results from our pilot study that failed to confirm this hypothesis; however, this pilot studied was insufficiently powered to detect potentially clinically important results.

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.

Analysis of systolic and diastolic time intervals during dobutamine-atropine stress echocardiography: diagnostic potential of the Doppler myocardial performance index

Systolic and especially diastolic Doppler time intervals may be early markers of myocardial ischemia inducible by dobutamine-atropine stress echocardiography (DASE). We postulated that the Doppler myocardial performance index (MPI) may help differentiate ischemic from nonischemic responses. Hemodynamic and Doppler echocardiography variables were measured prospectively at every stress level of DASE in 32 patients (mean age 67 +/- 13 years). Adequate recordings were obtained in 27 patients; 13 had an ischemic response (group I) and 14 a nonischemic response (group II). Heart rate differed between groups at baseline. At equivalent peak stress, left ventricular wall motion score index was significantly greater and ejection fraction lower in group I patients. Of the Doppler variables, only the MPI consistently differed between groups, irrespective of the number of stress levels compared. The Doppler MPI may be a useful adjunct to wall motion analysis in the detection of myocardial ischemia during DASE.

Functional and prognostic significance of silent ischemia during dobutamine stress echocardiography in the elderly

BACKGROUND

The functional and prognostic significance of silent ischemia relative to symptomatic ischemia during non-invasive testing remains controversial.

DESIGN

The aim of this prospective study was to assess whether the presence of dobutamine-induced silent ischemia was associated with the amount of myocardial ischemic burden and to determine the prognostic significance of painless ischemia in elderly people with stable coronary artery disease.

METHODS

A cohort of 289 patients > or =70 years of age with positive dobutamine stress echocardiography result and significant coronary artery disease proven by coronary arteriography, were followed up during a 35 +/- 13 month period for the development of cardiac events.

RESULTS

The prevalence of silent ischemia during dobutamine infusion was 63%. Patients with painful ischemia were more likely to have lower peak heart rate (P < 0.01) and showed ST segment depression more frequently during the dobutamine stress test than did patients with painless ischemia (52 versus 31%, P < 0.05). There was no significant difference between the patients with and without angina according to wall motion score index at rest (1.35 +/- 0.29 versus 1.32 +/- 0.37) and at peak stress (1.61 +/- 0.35 versus 1.58 +/- 0.44), stress-rest wall motion index difference (0.27 +/- 0.09 versus 0.25 +/- 0.08), the presence of dyskinesia at peak stress (36 versus 31%), the number of segments with regional > or =2 point change from rest to peak stress (38 versus 29%) and the decrease of left ventricular end systolic volume at peak stress (89 versus 86%). During the follow-up period a total of 269 patients developed 153 (57%) cardiac events: 15 cardiac deaths, 19 non-fatal myocardial infarctions, 119 episodes of unstable angina. No significant difference in cardiac mortality and in total cardiac event rate was observed between patients with or without angina (6 versus 5% and 60 versus 55%, respectively).

CONCLUSIONS

Our data demonstrate that the magnitude of myocardial dysfunction assessed by dobutamine stress echocardiography is comparable in elderly patients with or without anginal chest pain. The presence of painful ischemia is not accompanied by an increased risk for subsequent cardiac events in this cohort of patients.

Real-time perfusion imaging with low mechanical index pulse inversion Doppler imaging

OBJECTIVES

We sought to determine how successful pulse inversion Doppler (PID) imaging would be in detecting myocardial perfusion defects during dobutamine stress echocardiography.

BACKGROUND

By transmitting multiple pulses of alternating polarity (PID) at a low mechanical index, myocardial contrast enhancement from intravenously injected microbubbles can be detected using real-time frame rates. Pulse inversion Doppler imaging was performed in 117 patients during dobutamine stress echocardiography by using an intravenous bolus of a perfluorocarbon-filled, albumin-(Optison: n = 98) or liposome- (Definity: n = 19) encapsulated microbubble and a mechanical index of <0.3. The visual identification of myocardial contrast defects and wall motion abnormalities was determined by blinded review. Forty of the patients had quantitative angiography (QA) performed to correlate territorial contrast defects with stenosis diameter >50%.

RESULTS

There was a virtual absence of signal from the myocardium before contrast injections in all patients. Bright myocardial opacification at peak stress was observed in at least one coronary artery territory at frame rates up to 25 Hz in 114 of the 117 patients during dobutamine stress echocardiography. Regional myocardial contrast defects at peak stress were observed in all 30 patients with >50% stenosis in at least one vessel (13 with single-vessel and 17 with multivessel disease). Contrast defects were observed in 17 territories subtended by >50% diameter stenosis that had normal wall motion at peak stress. Overall agreement between QA and myocardial contrast enhancement on a territorial basis was 83%, as compared with 72% for wall motion.

CONCLUSIONS

Pulse inversion Doppler imaging allows the detection of myocardial perfusion abnormalities in real-time during stress echocardiography and will further add to the quality and sensitivity of this test.

Detection of angiographically significant coronary artery disease with accelerated intermittent imaging after intravenous administration of ultrasound contrast material

BACKGROUND

Accelerated intermittent harmonic imaging (AII) is used to detect myocardial perfusion abnormalities after intravenous injection of ultrasound contrast medium. A low mechanical index and frame rates of 10 to 20 Hz are used to allow simultaneous wall motion analysis. The purpose of this study was to determine whether the myocardial contrast enhancement achieved with AII can be used to detect angiographically significant coronary artery disease during stress echocardiography.

METHODS

We gave intravenous perfluorocarbon containing microbubbles to 45 patients (total of 270 regions) during dobutamine (n = 27) or exercise (n = 18) stress testing with AII. Quantitative angiography was performed on all patients after the stress echocardiograms were interpreted.

RESULTS

Quantitative angiography showed >50% diameter stenosis of at least 1 vessel in 32 patients (total of 118 regions). There were visually evident contrast defects in 100 (85%) of these regions, and wall motion was abnormal in 64 (54%). Overall, there was agreement between regional perfusion and quantitative angiographic findings in 217 of the 270 regions (kappa = 0.61; 80% agreement). Agreement with findings at quantitative angiography was good for both dobutamine stress (kappa = 0.66; 83% agreement) and exercise (kappa = 0.53; 77% agreement). The greatest incremental benefit of AII versus wall motion was gained during dobutamine stress. The contrast studies depicted 90% of the regions supplied by a vessel with >50% stenosis, whereas wall motion depicted only 32% (P =.001).

CONCLUSIONS

The results of this study indicated that accelerated intermittent perfusion imaging during stress echocardiography can improve the sensitivity of the study in detecting angiographically significant coronary artery disease, especially during dobutamine stress.

Safety of dobutamine-atropine stress echocardiography: A prospective experience of 4,033 consecutive studies

Dobutamine-atropine stress echocardiography (DASE) is an established method and has been shown to be accurate for the detection of coronary artery disease. Still, there are few large clinical studies that analyze the safety of DASE in general or the safety of performing it on an ambulatory basis. Most studies use a target heart rate as the primary end point regardless of whether asymptomatic ischemia occurs. Such studies have shown a serious cardiac event rate of approximately 0.3%. We prospectively studied 4,033 consecutive patients on an ambulatory basis and in the hospital with the use of DASE from July 1991 to December 1998. All tests were performed by an experienced physician, and all clinical and DASE data were stored in a large database organized at the beginning of the study. Dobutamine was infused in scalar doses of 5, 10, 20, 30, and 40 microg/kg per minute in 3-minute stages. Development of a new wall motion abnormality, achievement of 85% of target heart, and end of the DASE infusion protocol were used as an end point. If 85% of the target heart rate was not achieved, atropine was infused up to 1 mg in the absence of myocardial ischemia, which was used in 1,280 studies. There were 3,645 diagnostic tests, and 388 (10%) were found to be nondiagnostic. This result was due to poor image quality in 115 (3%), end of protocol in negative-submaximal examinations in 124 (3%), and limiting side effects in 149 (4%). Thirty-seven percent of the tests showed positive results for myocardial ischemia. Major test-related cardiac complications occurred in 10 (0.25%) patients and included 1 ventricular fibrillation, 1 case of myocardial infarction, and 8 cases of sustained ventricular tachycardia. Atropine poisoning was observed in 5 (0.12%) patients. No deaths occurred as a direct or indirect consequence of DASE. We conclude that dobutamine-atropine stress echocardiography is a reasonably safe method for detection of coronary artery disease in the hospital or in an ambulatory basis. The use of new wall motion abnormality as 1 of the end points may prevent further ischemia-related complications.

The functional significance of chronotropic incompetence during dobutamine stress test

OBJECTIVE

To investigate the functional significance of chronotropic incompetence during dobutamine stress echocardiography.

PATIENTS AND METHODS

The functional significance of chronotropic incompetence was evaluated during dobutamine stress echocardiography in 512 patients without beta blocker treatment who underwent dobutamine stress echocardiography (up to 40 microg/kg/min) and completed the protocol or reached the target heart rate. Mean (SD) age was 60 (12) years (313 men, 199 women). Chronotropic incompetence was defined as failure to achieve 85% of the maximum exercise heart rate predicted for age and sex (220 - age in men; 200 - age in women) at maximum dobutamine dose.

RESULTS

Chronotropic incompetence occurred in 196 patients (38%). Affected patients were significantly younger, more likely to be men (both p << 0.001) and smokers (p < 0.05), had a higher prevalence of previous myocardial infarction (p < 0.005) and resting wall motion abnormalities (p < 0. 05), and had a lower resting heart rate (p << 0.001) and systolic blood pressure (p << 0.001) than patients without chronotropic incompetence, but there was no difference in the overall prevalence of ischaemia and significant coronary artery disease. By multivariate analysis, independent predictors of chronotropic incompetence were a lower resting heart rate (p << 0.001), younger age (p << 0.001), and male sex (p << 0.001).

CONCLUSIONS

The relations among sex, age, and chronotropic incompetence show the need to titrate the dobutamine dose using specific data based on age and sex related heart rate responses to dobutamine rather than to an exercise stress test. Obtaining specific heart rate criteria is necessary to determine whether chronotropic incompetence represents a real failure to achieve a normal response or is the result of applying an inappropriate gold standard.

Selection of the optimal stress test for the diagnosis of coronary artery disease

OBJECTIVE

To compare the value and limitations of exercise testing, dipyridamole echocardiography, dobutamine-atropine echocardiography, and MIBI-SPECT (technetium-99m methoxyisobutyl nitrile single photon emission computed tomography) during dobutamine infusion in the diagnosis of coronary artery disease.

DESIGN

The performance of these four tests was assessed in random order on a consecutive cohort of patients. The presence or absence of coronary artery disease was confirmed by coronary angiography.

SETTING

Two tertiary care and university centres.

PATIENTS

102 consecutive patients with chest pain and no previous history of coronary artery disease. Ten patients with left bundle branch block were excluded for further analysis of exercise testing and scintigraphy results.

RESULTS

MIBI-SPECT was the most sensitive (87%) but the least specific test (70%). Exercise stress testing had a sensitivity of 66%, which increased to 80% when patients with inconclusive results were excluded. Dipyridamole and dobutamine echocardiography had similar sensitivity (81%, 78%) and specificity (94%, 88%). All four tests had similar accuracy and positive and negative predictive values. Agreement between the echocardiographic techniques was excellent (detection of coronary artery disease 87%, kappa = 0.72; regional analysis 93%, kappa = 0.72; diagnosis of the "culprit" vessel 95%, kappa = 0.92), and it was good between echocardiographic techniques and MIBI-SPECT (diagnosis of the culprit vessel 90%, kappa = 0.84 with dobutamine and 92%, kappa = 0.85 with dipyridamole).

CONCLUSIONS

Exercise stress testing has a sensitivity comparable to other tests in patients capable of exercising and with no basal electrical abnormalities. The greatest sensitivity is offered by MIBI-SPECT and the greatest specificity is obtained with stress echocardiography. Redundant information is obtained with dipyridamole echocardiography, dobutamine echocardiography, and MIBI-SPECT.

Noninvasive diagnosis of coronary artery stenosis in women with limited exercise capacity: comparison of dobutamine stress echocardiography and 99mTc sestamibi single-photon emission CT

OBJECTIVES

To compare the accuracy of dobutamine stress echocardiography (DSE) and simultaneous 99mTc sestamibi (MIBI) single-photon emission CT (SPECT) imaging for the diagnosis of coronary artery stenosis in women.

PATIENTS

Seventy women with limited exercise capacity referred for evaluation of myocardial ischemia.

METHODS

DSE (up to 40 microg/kg/min) was performed in conjunction with stress MIBI SPECT. Resting MIBI images were acquired 24 h after the stress test. Ischemia was defined as new or worsened wall motion abnormalities confirmed by DSE and as reversible perfusion defects confirmed by MIBI. Significant coronary artery disease was defined as > or = 50% luminal diameter stenosis.

RESULTS

DSE was positive for ischemia in 35 of 45 patients with coronary artery stenosis and in 2 of 25 patients without coronary artery stenosis (sensitivity = 78% CI, 68 to 88; specificity = 92% CI, 85 to 99; and accuracy = 83% CI, 74 to 92). A positive MIBI study for ischemia occurred in 29 patients with coronary artery stenosis and in 7 patients without coronary artery stenosis (sensitivity = 64% CI, 53 to 76; specificity = 72% CI, 61 to 83; and accuracy = 67% CI, 56 to 78 [p < 0.05 vs DSE]). In the 59 vascular regions with coronary artery stenosis, the regional sensitivity of DSE was higher than MIBI (69% CI, 62 to 77 vs 51% CI, 42 to 59, p < 0.05), whereas specificity in the 81 vascular regions without significant stenosis was similar (89% CI, 84 to 94 vs 88% CI, 82 to 93, respectively).

CONCLUSION

DSE is a useful noninvasive method for the diagnosis of coronary artery stenosis in women and provides a higher overall and regional diagnostic accuracy than dobutamine MIBI SPECT in this particular population.

Usefulness of isometric hand grip exercise in detecting coronary artery disease during dobutamine atropine stress echocardiography in patients with either stable angina pectoris or another type of positive stress test

Dobutamine atropine stress echocardiography (DASE) detects coronary artery disease (CAD) by increasing myocardial oxygen demand causing ischemia. The sensitivity of the test for detection of CAD is reduced in patients with submaximal stress. We hypothesized that increasing cardiac work load by adding isometric exercise would improve the detection of ischemia during DASE. We studied 31 patients, mean age 57+/-11 years, with angiographically documented CAD. Patients underwent DASE using incremental dobutamine doses from 5 to 40 microg/kg/min, followed by atropine if peak heart rate was <85% of predicted maximal. Hand grip was then performed for 2 minutes at 33% of maximal voluntary contraction, while dobutamine infusion was maintained at the peak dose. The addition of hand grip during dobutamine stress was associated with a significant increase in systolic blood pressure (143+/-21 vs 164+/-24 mm Hg, p = 0.001) and left ventricular end-systolic circumferential wall stress (72+/-30 x 10(3) dynes/cm2 vs 132+/-34 x 10(3) dynes/cm2, p = 0.004). Wall motion score index increased from 1.0 at rest to 1.15+/-0.18 with dobutamine (p = 0.0004 vs rest), and increased further to 1.29+/-0.22 with the addition of hand grip (p = 0.004 vs dobutamine). Ischemia was detected in 19 patients (62%) with dobutamine-atropine stress alone and in 25 (83%) after the addition of hand grip (p <0.05). The addition of hand grip during DASE is feasible, and improves the detection of myocardial ischemia.

Prognostic implications of a normal dobutamine-atropine stress echocardiogram in patients with chest pain

To assess the prognostic significance of a normal dobutamine-atropine stress echocardiogram in relation to the pretest probability of coronary artery disease (CAD), 200 consecutive patients (86 men and 114 women, mean [SD] age 59 [13] years) with a stable chest pain syndrome and a normal dobutamine-atropine stress echocardiogram were followed-up for 21 +/- 16 months. Outcome events were cardiac death, non-fatal myocardial infarction, and coronary revascularization procedures. Low (<10%), intermediate (10% to 80%), and high (>80%) pretest probabilities of CAD were present in 27 (14%), 108 (54%), and 65 (33%) patients, respectively. During follow-up, 2 patients (annual event rate 0.6%) had cardiac death, none had nonfatal myocardial infarction, and 4 patients (annual event rate 1.1%) underwent a coronary revascularization procedure. All patients with cardiac events had high pretest probabilities of CAD. Patients with cardiac death (but unproven significant CAD) had maximal tests without angina or ischemic electrocardiographic changes. In contrast, all patients with subsequent coronary revascularization had dobutamine-induced angina or ischemic electrocardiographic changes, and all except one study were submaximal. We conclude that patients with a stable chest pain syndrome and normal findings on dobutamine-atropine stress echocardiograms have an excellent cardiac prognosis. However, patients with typical angina, high pre-test probabilities of CAD, and stress-induced angina or ischemic electrocardiographic changes, and in particular those with submaximal stress, still appear to be at risk for functionally important CAD despite a normal dobutamine-atropine stress echocardiogram.

Dobutamine stress echocardiography in the detection of coronary artery disease in a clinical practice setting

In this prospective study, patients referred for coronary angiography for detection of disease underwent dobutamine stress echocardiography to define its value in a clinical practice setting.

RESULTS

Of 219 patients studied, 170 (78%) had significant coronary artery disease. The overall sensitivity and specificity of dobutamine stress echocardiography for coronary artery disease were 82 and 65%, respectively. The sensitivity was 88% for detection of triple-vessel disease, 83% for double-vessel disease, and 74% for single-vessel disease. Positive and negative predictive values for coronary artery disease were 89 and 51%, respectively. Dobutamine stress echocardiography correctly identified only 72 of 138 patients with significant stenosis of the left anterior descending coronary artery. In 219 patients, 345 of 657 major epicardial vessels had significant disease. Dobutamine stress echocardiography could only correctly identify the vessel involved in 188. Triple-vessel disease was present in 65 patients. Dobutamine stress echocardiography correctly categorised 18% (n = 12) of these. The remainder were incorrectly classified as having double-vessel disease or single-vessel disease (n = 45), or no disease at all (n = 8).

CONCLUSION

Dobutamine stress echocardiography performs well. However, lower specificity may lead to unwarranted referrals for coronary angiography, and the low NPV give false reassurance as to the absence of disease.

Comparison of dobutamine stress echocardiography and 99m-technetium sestamibi SPECT myocardial perfusion scintigraphy for predicting extent of coronary artery disease in patients with healed myocardial infarction

This study compares the value of dobutamine stress echocardiography and 99m-technetium methoxyisobutyl-isonitrile (MIBI) single-photon emission computed tomography (SPECT) in the assessment of extent and location of coronary narrowing in patients with healed myocardial infarction. Dobutamine (up to 40 microg/kg/ min)-atropine (up to 1 mg) stress echocardiography (DSE) in conjunction with MIBI SPECT was performed in 72 patients (52 men, mean age 57 +/- 11 years) with healed myocardial infarction referred for evaluation of myocardial ischemia. Ischemia was defined as new or worsened wall motion abnormalities at DSE and reversible perfusion defects at MIBI SPECT. Significant stenosis (> or = 50% luminal diameter stenosis) of the infarct-related artery was detected in 45 patients and of other coronary arteries in 22 patients. Sensitivity and specificity of remote ischemia for diagnosis of remote coronary stenosis were 68% (95% confidence interval [CI] 57 to 80) and 93% (CI 86 to 99) for DSE, and 64% (CI 52 to 76), and 90% (CI 83 to 98) for MIBI SPECT, respectively. The positive predictive value and specificity of peri-infarction ischemia for the diagnosis of infarct-related artery stenosis were 89% (CI 81 to 97) and 82% (CI 73 to 92) for DSE, and 87% (CI 79 to 95) and 82% (CI 73 to 92) for SPECT, respectively. The agreement between both techniques was higher for the diagnosis of remote than peri-infarction ischemia (84% vs 66%, p = 0.02). It is concluded that in patients with myocardial infarction undergoing dobutamine stress testing, both echocardiography and MIBI SPECT are clinically useful methods for the diagnosis of remote and infarct-related coronary artery stenosis.

Altered myocardial perfusion during dobutamine stress testing in silent versus symptomatic myocardial ischaemia assessed by quantitative MIBI SPET imaging

The aim of the study was to compare the extent and severity of reversible underperfusion in silent versus painful myocardial ischaemia during the dobutamine stress test. A consecutive series of 85 patients with significant coronary artery disease and reversible perfusion defects on technetium-99m methoxyisobutylisonitrile single-photon emission tomography performed at rest and during high-dose dobutamine stress (up to 40 microg kg-1 min-1) were studied. The left ventricle was divided into six segments. An ischaemic perfusion score was derived quantitatively by subtracting the rest from the stress defect score. Patients with multivessel disease had a higher ischaemic score (610+/-762 vs 310+/-411, P<0. 05) and a higher number of reversible perfusion defects (2.1+/-1.2 vs 1.1+/-0.8, P<0.01) than patients with single-vessel disease. Typical angina occurred in 37 patients (44%) during the test. There was no significant difference between patients with and patients without angina with respect to age, gender, peak rate-pressure product, prevalence of previous myocardial infarction, diabetes mellitus, multivessel disease or number of stenotic coronary arteries. Stress, rest and ischaemic scores as well as the number and distribution of reversible defects were not different in patients with and patients without angina. Patients with angina more frequently had a history of typical angina before the test (43% vs 17%, P<0.01) and ST-segment depression during the test (54% vs 25%, P<0.01). It is concluded that in patients with coronary artery disease and ischaemia detected by dobutamine scintigraphy, the extent and severity of coronary artery disease and myocardial perfusion abnormalities are similar with or without angina during stress testing.

Assessment of patients after coronary artery bypass grafting by dobutamine stress echocardiography

Dobutamine stress echocardiography is an accurate method for the diagnosis and localization of vascular compromise in patients evaluated after coronary artery bypass graft surgery. The test provides useful data for selection of patients for whom coronary angiography may be indicated.