Diagnosis of coronary artery disease using exercise echocardiography and positron emission tomography: comparison and analysis of discrepant results

Diagnostic accuracy of 13N-ammonia myocardial perfusion imaging with PET-CT in the detection of coronary artery disease

Background

¹³N-ammonia positron emission tomography-computed tomography (PET-CT) is being increasingly used as a non-invasive imaging modality for evaluating patients with known or suspected coronary artery disease (CAD), but information about the diagnostic accuracy of PET-MPI is sparse. Objectives: Our objective was to determine the accuracy of ¹³N-ammonia PET-CT myocardial perfusion imaging (MPI) for detecting CAD.

Methods

We retrospectively evaluated 383 patients with suspected CAD who underwent rest-stress ¹³N- ammonia PET-CT MPI. Invasive coronary angiography (ICA) was performed within 60 days for all patients with abnormal PET-MPI findings and for selected patients with normal PET-MPI findings.

Results

The mean age of the patients was 64±11 years, and the mean body mass index was 32±7 kg/m². Stress perfusion defects were identified in 147 (34%) out of a total of 383 patients. ICA was performed in 213 patients (145 patients with abnormal PET and 68 patients with normal PET). The sensitivity of PET-MPI for detection of obstructive CAD based on ≥50% stenosis was 90%; specificity, 90%; positive predictive value, 96%; negative predictive value, 76%; and diagnostic accuracy, 80%.

Conclusions

PET-MPI with ¹³N-ammonia affords high sensitivity and overall accuracy for detecting CAD. The addition of coronary artery calcium score (CACS) can improve CAD risk stratification.

Cardiac applications of PET

Routine use of cardiac positron emission tomography (PET) applications has been increasing but has not replaced cardiac single-photon emission computerized tomography (SPECT) studies yet. The majority of cardiac PET tracers, with the exception of fluorine-18 fluorodeoxyglucose (18F-FDG), are not widely available, as they require either an onsite cyclotron or a costly generator for their production. 18F-FDG PET imaging has high sensitivity for the detection of hibernating/viable myocardium and has replaced Tl-201 SPECT imaging in centers equipped with a PET/CT camera. PET myocardial perfusion imaging with various tracers such as Rb-82, N-13 ammonia, and O-15 H2O has higher sensitivity and specificity than myocardial perfusion SPECT for the detection of coronary artery disease (CAD). In particular, quantitative PET measurements of myocardial perfusion help identify subclinical coronary stenosis, better define the extent and severity of CAD, and detect ischemia when there is balanced reduction in myocardial perfusion due to three-vessel or main stem CAD. Fusion images of PET perfusion and CT coronary artery calcium scoring or CT coronary angiography provide additional complementary information and improve the detection of CAD. PET studies with novel 18F-labeled perfusion tracers such as 18F-flurpiridaz and 18F-FBnTP have yielded high sensitivity and specificity in the diagnosis of CAD. These tracers are still being tested in humans, and, if approved for clinical use, they will be commercially and widely available. In addition to viability studies, 18F-FDG PET can also be utilized to detect inflammation/infection in various conditions such as endocarditis, sarcoidosis, and atherosclerosis. Some recent series have obtained encouraging results for the detection of endocarditis in patients with intracardiac devices and prosthetic valves. PET tracers for cardiac neuronal imaging, such as C-11 HED, help assess the severity of heart failure and post-transplant cardiac reinnervation, and understand the pathogenesis of arrhytmias. The other uncommon applications of cardiac PET include NaF imaging to identify calcium deposition in atherosclerotic plaques and β-amyloid imaging to diagnose cardiac amyloid involvement. 18F-FDG imaging with a novel PET/MR camera has been reported to be very sensitive and specific for the differentiation between malignant and nonmalignant cardiac masses. The other potential applications of PET/MR are cardiac infectious/inflammatory conditions such as endocarditis.

Cardiac imaging in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) carry a high cardiovascular risk. In this patient group, cardiac structure and function are frequently abnormal and 74% of patients with CKD stage 5 have left ventricular hypertrophy (LVH) at the initiation of renal replacement therapy. Cardiac changes, such as LVH and impaired left ventricular systolic function, have been associated with an unfavourable prognosis. Despite the prevalence of underlying cardiac abnormalities, symptoms may not manifest in many patients. Fortunately, a range of available and emerging cardiac imaging tools may assist with diagnosing and stratifying the risk and severity of heart disease in patients with CKD. Moreover, many of these techniques provide a better understanding of the pathophysiology of cardiac abnormalities in patients with renal disease. Knowledge of the currently available cardiac imaging modalities might help nephrologists to choose the most appropriate investigative tool based on individual patient circumstances. This Review describes established and emerging cardiac imaging modalities in this context, and compares their use in CKD patients with their use in the general population.

Myocardial blood flow quantification for evaluation of coronary artery disease by positron emission tomography, cardiac magnetic resonance imaging, and computed tomography

The noninvasive detection of the presence and functional significance of coronary artery stenosis is important in the diagnosis, risk assessment, and management of patients with known or suspected coronary artery disease. Quantitative assessment of myocardial perfusion can provide an objective and reproducible estimate of myocardial ischemia and risk prediction. Positron emission tomography, cardiac magnetic resonance, and cardiac computed tomography perfusion are modalities capable of measuring myocardial blood flow and coronary flow reserve. In this review, we will discuss the technical aspects of quantitative myocardial perfusion imaging with positron emission tomography, cardiac magnetic resonance imaging, and computed tomography, and its emerging clinical applications.

Diagnosing coronary artery disease with hybrid PET/CT: it takes two to tango

The noninvasive diagnosis of coronary artery disease (CAD) is a challenging task. Although a large armamentarium of imaging modalities is available to evaluate the functional consequences of the extent and severity of CAD, cardiac perfusion positron emission tomography (PET) is considered the gold standard for this purpose. Alternatively, noninvasive anatomical imaging of coronary atherosclerosis with coronary computed tomography angiography (CCTA) has recently been successfully implemented in clinical practice. Although each of these diagnostic approaches has its own merits and caveats, functional and morphological imaging techniques provide fundamentally different insights into the disease process and should be considered to be complementary rather than overlapping. Hybrid imaging with PET/CT offers the possibility to evaluate both aspects nearly simultaneously, and studies have demonstrated that such a comprehensive assessment results in superior diagnostic accuracy, better prognostication, and helps in guiding clinical patient management. The aim of this review is to discuss the value of stand-alone CCTA and PET in CAD, and to summarize the available data on the surplus value of hybrid PET/CT including its strengths and limitations.

Characterizing the normal range of myocardial blood flow with ⁸²rubidium and ¹³N-ammonia PET imaging

BACKGROUND

Diagnosis of coronary disease and microvascular dysfunction may be improved by comparing myocardial perfusion scans with a database defining the lower limit of normal myocardial blood flow and flow reserve (MFR). To maximize disease detection sensitivity, a small normal range is desirable. Both (13)N-ammonia and (82)Rb tracers are used to quantify blood flow and MFR using positron emission tomography (PET). The goal of this study was to investigate the trade-off between noise and accuracy in both (82)Rb and (13)N-ammonia normal databases formed using a net retention model.

METHODS

Fourteen subjects with <5% risk of CAD underwent rest and stress (82)Rb and (13)N-ammonia dynamic PET imaging in a randomized order within 2 weeks. Myocardial blood flow was quantified using a one-compartment model for (82)Rb, and a two-compartment model for (13)N-ammonia. A simplified model was used to estimate tracer retention, with tracer-specific net extraction functions derived to obtain flow estimates.

RESULTS

Normal variability of retention reserve was equivalent for both tracers (±15% globally, ±16% regionally) and was lower in comparison to compartment model results (P < .05). The two-compartment model for (13)N-ammonia had the smallest normal range of global blood flow resulting in a lower limit of normal MFR = 2.2 (mean - 2 SD).

CONCLUSION

These results suggest that the retention model may have higher sensitivity for detection and localization of abnormal flow and MFR using (82)Rb and (13)N-ammonia, whereas the (13)N-ammonia two-compartment model has higher precision for absolute flow quantification.

Clinical applications of exercise stress echocardiography in the treadmill with upright evaluation during and after exercise

Exercise stress echocardiography is the most frequently used stress test in our laboratory. Exercise echocardiography is used mainly in the study of patients with coronary artery disease. However, the technique is increasingly being used to study other diseases. In our centre, we use an original methodology, published by us in 2000, in which we evaluate heart function during exercise in the treadmill. After the exercise, patients are maintained in orthostatic position when appropriate or lying down in left lateral decubitus for further evaluation. Since this method seems to increase the quality and the quantity of information obtained in so many clinical arenas, we now present a detailed review of this methodology and its applications.

Cardiac PET/CT for the evaluation of known or suspected coronary artery disease

Positron emission tomography (PET) is increasingly being applied in the evaluation of myocardial perfusion. Cardiac PET can be performed with an increasing variety of cyclotron- and generator-produced radiotracers. Compared with single photon emission computed tomography, PET offers lower radiation exposure, fewer artifacts, improved spatial resolution, and, most important, improved diagnostic performance. With its capacity to quantify rest-peak stress left ventricular systolic function as well as coronary flow reserve, PET is superior to other methods for the detection of multivessel coronary artery disease and, potentially, for risk stratification. Coronary artery calcium scoring may be included for further risk stratification in patients with normal perfusion imaging findings. Furthermore, PET allows quantification of absolute myocardial perfusion, which also carries substantial prognostic value. Hybrid PET-computed tomography scanners allow functional evaluation of myocardial perfusion combined with anatomic characterization of the epicardial coronary arteries, thereby offering great potential for both diagnosis and management. Additional studies to further validate the prognostic value and cost effectiveness of PET are warranted.

PET and PET/CT in cardiovascular disease

The present review provides an overview of the role of cardiac positron emission tomography in the diagnosis and management of cardiovascular disease. It expands on the relative advantages and disadvantages over other imaging modalities as well as the available evidence supporting its value in the diagnosis and management of patients with coronary artery disease, the assessment of myocardial viability, and evaluation of the cardiac sympathetic nervous system. Furthermore, the recent developments, such as the implementation of high-end computed tomography devices to form hybrid systems, and the advances of molecular imaging probes in experimental applications are briefly discussed.

Diagnostic value of SPECT, PET and PET/CT in the diagnosis of coronary artery disease: A systematic review

PURPOSE

The purpose of the study was to investigate the diagnostic value of SPECT, PET and PET/CT in the diagnosis of coronary artery disease, based on a systematic review.

MATERIAL AND METHODS

A search of PubMed/Medline and Sciencedirect databases in the English-language literature published over the last 24 years was performed. Only studies with at least 10 patients comparing SPECT, PET or combined PET/CT with invasive coronary angiography in the diagnosis of coronary artery disease (50% stenosis) were included for analysis. Sensitivities and specificities estimates pooled across studies were analysed using a Chi-square test.

RESULTS

Twenty-five studies met the selection criteria and were included for the analysis. Ten studies were performed with SPECT alone; while another six studies were performed with PET alone. Five studies were carried out with both PET and SPECT modalities, and the remaining four studies were investigated with integrated PET-CT. The mean value of sensitivity, specificity and accuracy of these imaging modalities for the diagnosis of coronary artery disease was 82% (95%CI: 76 to 88), 76% (95%CI: 70 to 82) and 83% (95%CI: 77 to 89) for SPECT; 91% (95%CI: 85 to 97), 89% (95%CI: 83 to 95) and 89% (95%CI: 83 to 95) for PET; and 85% (95%CI: 79 to 90), 83% (95%CI: 77 to 89) and 88% (95%CI: 82 to 94) for PET/CT, respectively. The diagnostic accuracy of these imaging modalities was dependent on the radiotracers used in these studies, with ammonia resulting in the highest diagnostic value.

CONCLUSION

Our review shows that PET has high diagnostic value for diagnosing coronary artery disease, and this indicates that it is a valuable technique for both detection and prediction of coronary artery disease.

Prompt-gamma compensation in Rb-82 myocardial perfusion 3D PET/CT

OBJECTIVE

To compare the diagnostic accuracy of Rb-82 myocardial perfusion three-dimensional (3D) PET with and without prompt-gamma compensation (PGC).

METHODS AND RESULTS

Retrospective, single center study of 76 patients who had rest and adenosine stress Rb-82 myocardial perfusion 3D PET. All studies were acquired using a Siemens Biograph-40 PET/CT scanner and were reconstructed with and without PGC. Fifty-seven patients (mean age 63 +/- 11 years, 26 men) had coronary angiography within 40 days of Rb-82 imaging. Nineteen patients (mean age 43 +/- 7 years, 10 men) had low likelihood of coronary artery disease (CAD). All PET images were scored by consensus of two blinded readers on a standard 5-point scale using a 17-segment left ventricular model. A normal PET test was defined as a summed stress score of less than four. Obstructive CAD at coronary angiography was used as the gold-standard and was defined as luminal stenoses > or =50% in one or more major coronary arteries. The prevalence of obstructive disease at coronary angiography was 68% (39/57). The mean summed stress score was 12 +/- 12 for PGC images and was 18 +/- 14 for non-PGC images. Sensitivity and specificity for obstructive CAD were 90% (95% CI 88-99) and 72% (95% CI 52-93) for PGC images and 95% (95% CI 88-100) and 22% (95% CI 3-41) for non-PGC images.

CONCLUSION

PGC in Rb-82 3D PET improves the specificity for obstructive CAD at coronary angiography with no significant loss in sensitivity.

PET/CT challenge for the non-invasive diagnosis of coronary artery disease

This review will focus on the clinical potential of PET/CT for the characterization of cardiovascular diseases. We describe the technical challenges of combining instrumentation with very different imaging performance and discuss the clinical applications in the field of cardiology.

Cardiac positron emission tomography: current clinical practice

In the last two decades, the field of nuclear cardiology has experienced significant progress. The introduction of positron emission tomography (PET) imaging represented a major breakthrough that has significantly contributed to a better understanding of physiology and pathophysiology of several heart diseases. Currently, PET imaging is recognized as a well-established method to assess cardiac perfusion, function, metabolism, and viability. This article summarizes the main clinical applications of state-of-the art cardiac PET technology.

Diagnostic performance of positron emission tomography in the detection of coronary artery disease: a meta-analysis

RATIONALE AND OBJECTIVES

Although myocardial perfusion positron emission tomography (PET), using either cyclotron-produced ammonia or generator-produced rubidium 82, has reported excellent diagnostic capabilities in the detection of coronary artery disease (CAD) in individual studies, the technique is not widely used in practice. This may be driven by cost and availability or by unawareness of performance. The purpose of our study was to conduct an evidence-based evaluation of PET in the diagnosis of CAD.

MATERIALS AND METHODS

We examined studies from January 1977 to July 2007 using MEDLINE and EMBASE. A study was included if it (1) used PET as a diagnostic test for CAD and (2) used catheter x-ray angiography as the reference standard (> or =50% diameter stenosis). Analysis was performed on a subject and coronary territory level.

RESULTS

Nineteen studies (1442 patients) met the inclusion criteria. On a patient level, PET demonstrated a sensitivity of 0.92 (95% confidence interval [CI]: 0.90-0.94) and specificity of 0.85 (CI: 0.79-0.90), with a positive likelihood ratio (LR+) of 6.2 (CI: 3.3-11.8) and negative likelihood ratio (LR-) of 0.11 (CI: 0.08-0.14). On a coronary territory level (n = 1130), PET showed a sensitivity of 0.81 (CI: 0.77-0.84) and specificity of 0.87 (CI: 0.84-0.90), with an LR+ of 5.9 (CI: 4.5-7.9) and an LR- of 0.19 (CI: 0.09-0.38).

CONCLUSION

PET demonstrates excellent diagnostic properties in the diagnosis of CAD, especially at the patient level. The capabilities appear superior to those reported in meta-analyses for perfusion imaging with Tl-201 and sestamibi, or anatomical imaging with coronary MDCT angiography or MRA. Given that previous studies have found PET to be cost-effective and the current findings of excellent sensitivity and specificity, the modality should be more widely considered as an initial test in the diagnosis of CAD.

Comparison of computed tomographic angiography versus rubidium-82 positron emission tomography for the detection of patients with anatomical coronary artery disease

BACKGROUND

The present study compared computed tomographic coronary angiography (CTA) and positron emission tomography (PET) for the detection of significant anatomical coronary artery stenosis as defined by conventional invasive coronary angiography (CICA).

METHODS

The study protocol was approved by the local ethics board, and informed consent was obtained from all patients. Of the 26 patients (mean age 57+/-9 years, 18 men) who prospectively underwent CTA and rubidium-82 PET before CICA, 24 patients had a history of chest pain. Images were interpreted by expert readers and assessed for the presence of anatomically significant coronary stenosis (50% luminal diameter stenosis or greater) or myocardial perfusion defects. Diagnostic test characteristics were analyzed using patient-based, territory-based, vessel-based and segment-based analyses.

RESULTS

In the 24 patients referred for chest pain, CTA had similar sensitivity to PET, but was more specific (sensitivity 95% [95% CI 72% to 100%] versus 95% [95% CI 72% to 100%], respectively; specificity 100% [95% CI 46% to 100%] versus 60% [95% CI 17% to 93%], respectively) in the detection of patients with anatomical coronary artery stenosis of 50% or greater. On a per-segment basis of all 26 patients, CTA had a sensitivity, specificity, positive predictive value and negative predictive value of 72%, 99%, 91% and 95%, respectively, in all coronary segments.

CONCLUSIONS

Coronary CTA has a similar sensitivity and specificity to rubidium-82 PET for the identification of patients with significant anatomical coronary artery disease.

Diagnostic accuracy of rubidium-82 myocardial perfusion imaging with hybrid positron emission tomography/computed tomography in the detection of coronary artery disease

OBJECTIVES

Our objective was to determine the accuracy of rubidium-82 myocardial perfusion positron emission tomography-computed tomography (PET-CT) imaging for detecting obstructive coronary artery disease (CAD).

BACKGROUND

Hybrid PET-CT is a new noninvasive imaging modality for evaluating patients with known or suspected CAD.

METHODS

We evaluated 64 consecutive patients with suspected CAD undergoing rest-stress rubidium-82 cardiac PET-CT (CT was only used for attenuation correction) and coronary angiography within 7 days (range 1 to 180 days). Patients with known CAD, previous myocardial infarction, or revascularization were excluded. Thirty-eight patients with a low likelihood for CAD were also studied. Obstructive CAD was defined as > or =70% diameter stenosis on angiography.

RESULTS

The mean age of the patients was 62 +/- 15 years, with a body mass index of 31 +/- 8 kg/m2. Chest pain and/or dyspnea were the predominant reasons for evaluation. Stress perfusion defects were detected in 41 of 44 patients with obstructive CAD (sensitivity 93%, 95% confidence interval [CI] 87 to 99). The specificity of PET-CT was 83% (48 of 58, 95% CI 71 to 91), and its overall diagnostic accuracy was 87% (95% CI 79 to 93). All patients with a low likelihood for CAD showed normal scans, for a normalcy rate of 100% (38 of 38, 95% CI 91 to 100). The sensitivity for detecting CAD in patients with single and multivessel (> or =2 vessels) disease was 92% (22 of 24, 95% CI 74 to 99) and 95% (19 of 20, 95% CI 74 to 99), respectively.

CONCLUSIONS

Myocardial perfusion PET-CT affords high sensitivity and overall accuracy for detecting CAD, including patients with single-vessel disease, women, and obese patients.

Cardiac PET-CT

Integrated positron emission tomography computed tomography (PET/CT) scanners allow a true integration of the structure and function of the heart. Myocardial perfusion PET provides a high sensitivity (91%) and specificity (89%) for the diagnosis of obstructive coronary artery disease (CAD). But, as with single photon emission CT, relative perfusion PET often uncovers only the territory subtended by the most severe coronary stenosis, leading to underestimation of the extent of CAD. In contrast, quantitative PET provides a noninvasive assessment of myocardial blood flow and coronary flow reserve and improves detection of preclinical and multivessel coronary atherosclerosis. Similarly, CT coronary angiography is an accurate means to image the entire continuum of anatomic coronary atherosclerosis from nonobstructive to obstructive CAD. However, not all coronary stenoses are hemodynamically significant and <50% of the patients with obstructive CAD on CT angiography demonstrate stress induced perfusion defects. Stress PET data complement the anatomic information on the CT angiogram by providing instant readings about the ischemic burden of coronary stenoses. Thus, combined PET/CT may be potentially superior to CT angiography alone for the guiding revascularization decisions. Further, fusion of the PET and CT angiogram images allows identification of the culprit stenosis in patients presenting with chest pain. Finally, the advances in molecular imaging and image fusion may soon make noninvasive detection of vulnerable coronary plaques a clinical reality. In summary, integrated PET/CT is a powerful new noninvasive modality that offers the potential for refined diagnosis and management of the entire spectrum of coronary atherosclerosis.

A meta-analytic comparison of echocardiographic stressors

BACKGROUND

The relative performance of alternative stressors for stress echocardiography for the diagnosis of coronary artery disease (CAD) is not well established.

METHODS

All studies published between 1981 to December 2001 who met inclusion criteria were included in this analysis. We performed a summary receiver operator characteristic (SROC) analysis and calculated weighted mean of the likelihood ratio and sensitivity/specificity. A covariate analysis using meta-regression methods was also performed.

RESULTS

Forty-four studies presented data on Exercise, 11 on Adenosine, 80 on Dobutamine, 40 on Dipyridamole, 16 on transatrial pacing transesophageal echocardiography (Tap-TEE), and 7 on transatrial pacing transthorasic echocardiography (Tap-TTE). SROC analysis showed that the following order of most discriminatory to least: Tap-TEE, Exercise, Dipyridamole, Dobutamine and Adenosine. Weighted means sensitivity/specificity were Exercise: 82.6/84.4%, Adenosine: 68.4/80.9%, Dobutamine: 79.6/85.1%, Dipyridamole: 71.0/92.2%, Tap-TTE: 90.7/86.1%, and Tap-TEE: 86.2/91.3%. Covariate analysis showed that the discriminatory power of Exercise decreased with increasing mean age.

CONCLUSIONS

Tap-TEE is a very accurate test for both ruling in and ruling out CAD although its invasiveness may limit its clinical acceptability. Exercise is a well-balanced satisfactory test for both ruling in and ruling out but performance might be lower for the elderly. Dobutamine offers a reasonable compromise for Exercise. Dipyridamole might be good for ruling in but not for ruling out CAD. The incapability in ruling-out CAD was a major problem in clinical application of the stress. Adenosine was the least useful stressor in diagnosing CAD.

Stress Echocardiography: A Review of the Principles and Practice

Stress echocardiography, both pharmacologic and physiological, is an established noninvasive diagnostic method of detecting coronary artery disease. It also has a role in the assessment of patients with chest pain, the assessment of cardiovascular risk before noncardiac surgery, the assessment of patients after a myocardial infarction, the detection of viability in dysfunctional myocardium, and the prediction of functional recovery. The prognostic value of stress echocardiography is emerging. In this article, we discuss the methodology, diagnostic accuracy, and various clinical applications of stress echocardiography. We also review its limitations and compared it with other noninvasive methods of assessing patients with coronary artery disease.

Dobutamine positron emission tomography: absolute quantitation of rest and dobutamine myocardial blood flow and correlation with cardiac work and percent diameter stenosis in patients with and without coronary artery disease

OBJECTIVES

This study sought to measure myocardial blood flow at rest and during dobutamine infusion and to correlate flow with cardiac work and severity of coronary artery disease.

BACKGROUND

Dobutamine is used with cardiac imaging to induce possible ischemia in patients with known or suspected coronary artery disease. Positron emission tomography permits noninvasive quantitation of myocardial blood flow.

METHODS

Fifteen patients with quantitative coronary arteriography were studied at rest and during dobutamine infusion using nitrogen-13 ammonia flow imaging with positron emission tomography. Myocardial blood flow was determined in regions corresponding to the three major coronary arteries for myocardium with and without dobutamine flow defects and with and without a > 50% diameter stenosis.

RESULTS

Eight patients had at least one dobutamine flow defect; four of whom had a previous myocardial infarction. One patient with > 50% diameter stenosis had no flow defects, and one with < 50% diameter stenosis (48%) had one defect. Dobutamine significantly increased myocardial blood flow in regions with and without a dobutamine flow defect or > 50% diameter stenosis, with a greater increase when a defect or > 50% diameter stenosis was not present. Rest and dobutamine flows in regions without > 50% diameter stenosis were 0.93 +/- 0.20 (mean +/- SD) and 2.16 +/- 0.52 ml/min per g (p < 0.01), respectively. The corresponding flows in regions without a defect were 0.94 +/- 0.21 and 2.17 +/- 0.53 ml/min per g (p < 0.01), respectively. This 2, 4-fold increase in flow was significantly correlated (p < 0.001) with a 2.2-fold increase in rate-pressure product induced by dobutamine. The rest and dobutamine flows for regions subtended by a vessel with > 50% diameter stenosis were 0.70 +/- 0.33 and 1.20 +/- 0.54 ml/min per g (p < 0.05), respectively, whereas the corresponding values for regions with a dobutamine flow defect were 0.69 +/- 0.33 ml/min per g at rest and 1.23 +/- 0.54 ml/min per g during dobutamine (p < 0.05). Dobutamine increased flow inversely proportional to percent diameter stenosis. The rest flow for regions with a dobutamine flow defect were not significantly different from that in regions without defects.

CONCLUSIONS

Dobutamine resulted in a significant increase in myocardial blood flow that correlated significantly with both increased cardiac work and degree of stenosis.

Comparison of dobutamine and exercise echocardiography for detecting coronary artery disease

There has been no study comparing the efficacy of dobutamine and exercise echocardiography in detecting coronary artery disease (CAD) or their physiologic effects at ischemic threshold in the same group of patients. To accomplish this, 52 patients presenting for coronary angiography underwent supine ergometer exercise and dobutamine echocardiography. Compared with angiography, the overall sensitivity of detecting CAD was 78% for exercise and 86% for dobutamine echocardiography (p = NS). The sensitivities of detecting patients with 1-, 2-, 3- and multivessel CAD with exercise echocardiography were 63, 80, 100 and 90%, respectively, and with dobutamine echocardiography 75, 90, 100 and 95%, respectively (p = NS, exercise vs dobutamine). The specificity of both tests was 87%. At ischemic threshold, heart rate was significantly lower with dobutamine than with exercise echocardiography (91 +/- 3 vs 114 +/- 3 beats/min; p < 0.001), systolic blood pressure was significantly lower with dobutamine testing (155 +/- 5 vs 176 +/- 6 mm Hg; p < 0.01), and rate-pressure product was significantly lower with dobutamine stress (14.1 +/- 0.7 vs 19.8 +/- 0.8 x 10(3) beats/min x mm Hg; p < 0.001). It is concluded that the efficacy of detecting CAD by exercise and dobutamine echocardiography is comparable, and the physiology at ischemic threshold of the 2 methods is significantly different and suggests a different means of inducing myocardial ischemia.