Quantitative thallium-201 single-photon emission computed tomography during maximal pharmacologic coronary vasodilation with adenosine for assessing coronary artery disease

The prognostic value of non-perfusion variables obtained during vasodilator stress myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is an established diagnostic test that provides useful prognostic data in patients with known or suspected coronary artery disease. In more than half of the patients referred for stress testing, vasodilator stress is used in lieu of exercise. Unlike exercise, vasodilator stress does not provide information on exercise and functional capacity, heart rate recovery, and chronotropy, and ECG changes are less frequent. These non-perfusion data provide important prognostic and patient management information. Further, event rates in patients undergoing vasodilator MPI are higher than in those undergoing exercise MPI and even in those with normal images probably due to higher pretest risk. However, there are a number of non-perfusion variables that are obtained during vasodilator stress testing, which have prognostic relevance but their use has not been well emphasized. The purpose of this review is to summarize the prognostic values of these non-perfusion data obtained during vasodilator MPI.

Angina Relief by Ranolazine Identifies False-Negative SPECT Myocardial Perfusion Scans in Patients with Coronary Disease Demonstrated by Coronary Angiography

Normal myocardial perfusion imaging (MPI) reduces intermediate- or high-risk pretest probability patients to low- or intermediate-risk posttest probability, respectively, for coronary disease (CD). Since ranolazine (RAN) relieves only angina, anginal patients with normal MPI whose angina is relieved by RAN present a significant dilemma. The purpose of this retrospective chart review was to confirm the impression that coronary angiography (CA) is indicated in patients whose class 3 to 4 angina is relieved by RAN, but have normal myocardial single-photon emission computed tomography (SPECT) MPIs. Charts of patients with stable class 3 to 4 angina (typical and atypical) and normal MPIs (left ventricular ejection fraction [LVEF] ≥50% and segmental score = 0) were reviewed. CA was done on all the patients with complete angina relief taking RAN, as well as nonresponders whose anginal etiology could not be explained. Stenoses were considered flow-restrictive when more than 70% diameter stenosis is observed by quantitative CA, or, when 50 to 70%, fractional flow reserve (FFR) measured ≤0.80. RAN relieved angina in 36 of 54 (67%) patients. Of the known cases, 25 of these 36 (69%) had 43 stenoses ≥50% (mean = 66%): 15 (60%) had 1 vessel disease; 9 (36%) had multivessel disease; 18 (72%) had left anterior descending (LAD) disease; 1 (4%) had left main disease. Twenty one of 43 (49%) stenosis were > 70%; 22 (51%) stenoses were 50 to 70% and required FFR measurement. Twenty nine of 43 stenoses (67%) were considered flow-restrictive in 18 of these 25 (72%) patients. Eight RAN nonresponders with no explanation for angina had no CD at CA. RAN angina relief is invaluable in identifying falsely negative SPECT MPI, and 50% of these patients have flow-restrictive stenoses.

Patterns of late gadolinium enhancement in Duchenne muscular dystrophy carriers

BACKGROUND

This study was designed to assess whether cardiovascular magnetic resonance imaging (CMR) in Duchenne muscular dystrophy carriers (DMDc) may index any cell milieu elements of LV dysfunction and whether this cardiac phenotype may be related to genotype. The null hypothesis was that myocardial fibrosis, assessed by late gadolinium enhancement (LGE), might be similarly accounted for in DMDc and gender and age-matched controls.

METHODS

Thirty DMDc patients had CMR and genotyping with 37 gender and age-matched controls. Systolic and diastolic LV function was assessed by 2D-echocardiography.

RESULTS

Absolute and percent LGE were higher in muscular symptomatic (sym) than asymptomatic (asy) DMDc (1.77 ± 0.27 vs 0.76 ± 0.17 ml; F = 19.6, p < 0.0001 and 1.86 ± 0.26% vs 0.68 ± 0.17%, F = 22.1, p < 0.0001, respectively). There was no correlation between LGE and age. LGE was seen most frequently in segments 5 and 6; segment 5 was involved in all asy-DMDc. Subepicardial LGE predominated, compared to the mid-myocardial one (11 out of 14 DMDc). LGE was absent in the subendocardium. No correlations were seen between genotyping (type of mutation, gene region and protein domain), confined to the exon's study, and cardiac phenotype.

CONCLUSIONS

A typical myocardial LGE-pattern location (LV segments 5 and 6) was a common finding in DMDc. LGE was more frequently subepicardial plus midmyocardial in sym-DMDc, with normal LV systolic and diastolic function. No genotype-phenothype correlation was found.

A combination of anatomical and functional evaluations improves the prediction of cardiac event in patients with coronary artery bypass

OBJECTIVE

To study the usefulness of combined risk stratification of coronary CT angiography (CTA) and myocardial perfusion imaging (MPI) in patients with previous coronary-artery-bypass grafting (CABG).

DESIGN

A retrospective, observational, single centre study.

SETTING AND PATIENTS

204 patients (84.3% men, mean age 68.7±7.6) undergoing CTA and MPI.

MAIN OUTCOME MEASURES

CTA defined unprotected coronary territories (UCT; 0, 1, 2 or 3) by evaluating the number of significant stenoses which were defined as the left main trunk ≥50% diameter stenosis, other native vessel stenosis ≥70% or graft stenosis ≥70%. Using a cut-off value with receiver-operating characteristics analysis, all patients were divided into four groups: group A (UCT=0, summed stress score (SSS)<4), group B (UCT≥1, SSS<4), group C (UCT=0, SSS≥4) and group D (UCT≥1, SSS≥4).

RESULTS

Cardiac events, as a composite end point including cardiac death, non-fatal myocardial infarction, unstable angina requiring revascularisation and heart-failure hospitalisation, were observed in 27 patients for a median follow-up of 27.5 months. The annual event rates were 1.1%, 2%, 5.7% and 12.9% of patients in groups A, B, C and D, respectively (log rank p value <0.0001). Adding UCT or SSS to a model with significant clinical factors including left ventricular ejection fraction, time since CABG and Euro SCORE II improved the prediction of events, while adding UCT and SSS to the model improved it greatly with increasing C-index, net reclassification improvement and integrated discrimination improvement.

CONCLUSIONS

The combination of anatomical and functional evaluations non-invasively enhances the predictive accuracy of cardiac events in patients with CABG.

Qualitative score of systemic arteriosclerosis by vascular ultrasonography as a predictor of coronary artery disease in type 2 diabetes

OBJECTIVE

Patients with type 2 diabetes mellitus (T2DM) are at risk of polyvascular comorbidities and poor prognosis. Non-invasive techniques for early prediction of coronary artery disease (CAD) are desirable to prevent cardiovascular events in these patients. The aim of the present study was to investigate the association between CAD and systemic arteriosclerosis by qualitative vascular ultrasonography.

METHODS

The study subjects were 102 consecutive outpatients with T2DM [males/females = 60/42, age: mean ± SD 67 ± 9 (range, 40-85) years] evaluated by vascular ultrasonography for arteriosclerosis in the abdominal aorta, carotid, renal, and common iliac arteries. The total number of detected arteriosclerotic vascular lesions in the four arteries was determined. CAD was diagnosed by two cardiologists using either stress electrocardiography, myocardial scintigraphy, multi-detector row computed tomography or coronary angiography.

RESULTS

Multiple arteriosclerotic vascular lesions (>1) were detected in 64 (63%) patients. The total systemic vascular score was significantly higher in patients with CAD than those without (average score 2.7 versus 1.0, p < 0.0001). None of the CAD patients had a total score of 0. Age- and sex-adjusted multiple logistic regression analysis identified total score of ≥ 2 as the only predictor of CAD (p < 0.001). The sensitivity, specificity, positive and negative predictive values for total systemic vascular score in the prediction of CAD were 98%, 77%, 83%, and 97%, respectively, which were better than those for carotid mean and maximum intima-media thickness.

CONCLUSION

Non-invasive qualitative evaluation of systemic arteriosclerosis by the total systemic vascular score is potentially useful for the early prediction of CAD in T2DM patients.

Non-invasive evaluation of internal thoracic artery anastomosed to the left anterior descending artery with 320-detector row computed tomography and adenosine thallium-201 myocardial perfusion scintigraphy

PURPOSE

We evaluated the relationship between internal thoracic artery (ITA) stenosis anastomosed to the left anterior descending artery (LAD) and the degree of LAD stenosis using 320-detector row computed tomography (320-ADCT) and adenosine thallium-201 myocardial perfusion scintigraphy (Tl-201-MPS).

METHODS

We included 101 patients who underwent coronary artery bypass grafting (CABG) using ITA grafts; 320-ADCT and adenosine Tl-201-MPS were performed 2-3 months after CABG. Clinical parameters, degree of LAD stenosis, and regional myocardial ischemia of the LAD territory were compared between patients without ITA stenosis (Group A) and with ITA stenosis (Group B).

RESULTS

Thirty patients (30%) had ≤75% LAD stenosis, and 9 patients (30%) showed significant ITA stenosis. Regional ischemia was noted in 23 patients (23%). There were no differences in clinical parameters between the 2 groups. Twenty-two patients (24%) in Group A and 8 patients (89%) in Group B had ≤75% LAD stenosis (P <0.002). No Group B patients had regional myocardial ischemia of the LAD territory.

CONCLUSION

We concluded that ≤75% LAD stenosis significantly influences ITA stenosis, without associated regional myocardial ischemia of the LAD territory. Non-invasive 320-ADCT and adenosine Tl-201-MPS for ITA evaluation may be useful for long-term follow-up of patients after CABG.

Functional assessment of coronary artery flow using adenosine stress dual-energy CT: a preliminary study

We attempted to assess coronary artery flow using adenosine-stress and dual-energy mode with dual-source CT (DE-CT). Data of 18 patients with suspected coronary arteries disease who had undergone cardiac DE-CT were retrospectively analyzed. The patients were divided into two groups: 10 patients who performed adenosine stress CT, and 8 patients who performed rest CT as controls. We reconstructed an iodine map and composite images at 120 kV (120 kV images) using raw data with scan parameters of 100 and 140 kV. We measured mean attenuation in the coronary artery proximal to the distal portion on both the iodine map and 120 kV images. Coronary enhancement ratio (CER) was calculated by dividing mean attenuation in the coronary artery by attenuation in the aortic root, and was used as an estimate of coronary enhancement. Coronary stenosis was identified as a reduction in diameter of >50% on CT angiogram, and myocardial ischemia was diagnosed by adenosine-stress myocardial perfusion scintigraphy. The iodine map showed that CER was significantly lower for ischemic territories (0.76 ± 0.06) or stenosed coronary arteries (0.77 ± 0.06) than for non-ischemic territories (0.95 ± 0.21, P = 0.02) or non-stenosed coronary arteries (1.07 ± 0.33, P < 0.001). The 120 kV images showed no difference in CER between these two groups. Use of CER on the iodine map separated ischemic territories from non-ischemic territories with a sensitivity of 86% and a specificity of 75%. Our quantification is the first non-invasive analytical technique for assessment of coronary artery flow using cardiac CT. CER on the iodine map is a candidate method for demonstration of alteration in coronary artery flow under adenosine stress, which is related to the physiological significance of coronary artery disease.

Quantitative imaging of coronary blood flow

Positron emission tomography (PET) is a nuclear medicine imaging modality based on the administration of a positron-emitting radiotracer, the imaging of the distribution and kinetics of the tracer, and the interpretation of the physiological events and their meaning with respect to health and disease. PET imaging was introduced in the 1970s and numerous advances in radiotracers and detection systems have enabled this modality to address a wide variety of clinical tasks, such as the detection of cancer, staging of Alzheimer's disease, and assessment of coronary artery disease (CAD). This review provides a description of the logic and the logistics of the processes required for PET imaging and a discussion of its use in guiding the treatment of CAD. Finally, we outline prospects and limitations of nanoparticles as agents for PET imaging.

Regional myocardial perfusion reserve determined using myocardial perfusion magnetic resonance imaging showed a direct correlation with coronary flow velocity reserve by Doppler flow wire

AIMS

Quantitative analysis of rest-stress myocardial perfusion magnetic resonance imaging (MRI) can provide assessments of regional myocardial perfusion reserve (MPR). The purpose of this study was to compare regional MPR determined by myocardial perfusion MRI with coronary flow reserve (CFR) by intracoronary Doppler flow wire.

METHODS AND RESULTS

Twenty patients with suspected coronary artery disease (CAD) were studied. Average peak velocity was measured by Doppler flow wire in the resting state and during adenosine triphosphate (ATP) stress in 36 coronary arteries. CFR measurements for each patient were performed in the culprit and one non-culprit non-stenotic artery. First-pass, contrast-enhanced myocardial perfusion MR images were obtained in the resting state and during ATP stress within the week before the Doppler wire procedure. Regional myocardial blood flow (MBF) was quantified in 16 myocardial segments by analysing arterial input and myocardial output using a Patlak plot method. MPR was calculated as stress MBF divided by rest MBF. CFR measured by Doppler flow wire was compared with MPR in the myocardial segments corresponding to vessel territories. The average MPR measured by perfusion MRI was 1.77 +/- 0.62 for the culprit arteries and 3.45 +/- 0.78 for the non-culprit arteries, respectively (P < 0.001). The averaged CFR by Doppler flow wire was 1.72 +/- 0.44 in the culprit arteries and 3.14 +/- 0.74 in the non-culprit arteries, respectively (P < 0.001). For both culprit and non-culprit vessel groups, significant direct correlations were observed between MR assessments of MPR and Doppler assessments of CFR (culprit artery: R = 0.87, Non-culprit artery: R = 0.86) On Bland-Altman analysis, the mean differences between MPR determined by myocardial perfusion MRI and CFR measured by Doppler wire were 0.05 in culprit arteries (95% limit of agreement; -0.65 to 0.56) and 0.36 in non-culprit arteries (95% limit of agreement; -1.24 to 0.44). The sensitivity and specificity of MR measurement of MPR for predicting physiologically significant reduction of Doppler CFR (<2) was 88% (95% CI 61.7-98.5) and 90% (95% CI 68.3-98.8), respectively.

CONCLUSION

The current results using Doppler flow wire as a reference method demonstrated that quantitative analysis of stress-rest myocardial perfusion MRI can provide a non-invasive assessment of reduced MPR in patients with CAD.

Quantification of myocardial perfusion by contrast-enhanced 64-MDCT: characterization of ischemic myocardium

OBJECTIVE

Assessment of hemodynamic changes in ischemic cardiac segments at rest using CT has yet to be performed. We hypothesized that variations in subendocardial perfusion during the cardiac cycle might be related to the appearances of ischemia. The purpose of this study was to investigate myocardial perfusion in ischemic segments using contrast-enhanced 64-MDCT.

SUBJECTS AND METHODS

We performed cardiac MDCT at rest and stress/rest (201)Tl myocardial perfusion scintigraphy (MPS) in 34 patients with suspected coronary artery disease. We reconstructed 2D long- and short-axis cardiac images in diastolic and systolic phases using raw data from coronary CT angiography. The attenuation value (in Hounsfield units) in the myocardium was used as an estimate of myocardial perfusion. We measured the subendocardial intensity of 17 segments according to the American Heart Association classification. Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardial intensity at systole or diastole, respectively, for each segment by the mean value across all segments for each patient. We used stress/rest MPS to evaluate the variation in myocardial perfusion at systole and diastole for the segments diagnosed as ischemic or nonischemic.

RESULTS

Systolic perfusion for ischemic segments was significantly lower than that for nonischemic segments in 15 of 17 segments. The difference between systolic perfusion and diastolic perfusion in ischemic segments was significantly lower than that in nonischemic segments (14 of 17 segments). There was no significant difference in diastolic perfusion between ischemic and nonischemic segments (15 of 17 segments).

CONCLUSION

Our results suggest that a pattern of subendocardial hypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.

Direct comparison between pharmacological stress with adenosine triphosphate disodium and exercise stress myocardial perfusion imagings

To clarify the significance of adenosine triphosphate disodium stress myocardial perfusion imaging (ATP-MPI), we directly compared the findings of ATP-MPI with those of exercise stress myocardial perfusion imaging (Ex-MPI). ATP-MPI, Ex-MPI, and coronary angiography (CAG) were performed within 60 days in 17 coronary artery disease patients with mean age of 62.1+/-7.9 years. CAG revealed single-vessel disease (SVD) in 10 patients and multivessel disease (MVD) in seven patients. The summed stress score (SSS) of ATP-MPI was significantly higher than that of Ex-MPI (10.0 [7.8-14.3] vs. 8.0 [4-18], P<0.05). No difference in the SSS was observed between ATP-MPI and Ex-MPI in patients with SVD (8.0 [6.0-9.0] vs. 8.0 [6.0-10.0], NS), whereas this difference was significant in patients with MVD (15.0 [14.0-22.8] vs.9 [7.3-16.3], P<0.05). There was no difference in the summed rest score between ATP-MPI and Ex-MPI. The univariate logistic analysis showed that "MVD" was the significant factor influencing to the overt discrepancy between ATP-MPI and Ex-MPI (odds ratio: 9.0, 95% confidence interval: 1.07-75.84, P=0.043). The accuracy of ATP-MPI and Ex-MPI in detecting the territory of stenotic coronary vessel or previous myocardial infarction was 98.0% and 92.1% (NS), respectively. In conclusion, ATP-MPI is useful for detecting potential ischemic areas that cannot be detected by Ex-MPI, particularly in patients with MVD.

Diagnostic accuracy of stress first-pass contrast-enhanced myocardial perfusion MRI compared with stress myocardial perfusion scintigraphy

OBJECTIVE

The purpose of this study was to determine the diagnostic accuracy of stress perfusion MRI acquired with saturation-recovery prepared turbo fast low-angle shot (turbo FLASH) compared with stress myocardial perfusion scintigraphy. Recent studies show that first-pass contrast-enhanced myocardial perfusion MRI can provide noninvasive detection of low-limiting stenosis in the coronary artery.

MATERIALS AND METHODS

First-pass contrast-enhanced MR images were acquired at rest and during stress in 40 patients with suspected coronary artery disease. All patients underwent thallium-201 SPECT without attenuation correction and coronary angiography. Two reviewers independently assigned one of five confidence grades without knowing the results of coronary angiography for receiver operating characteristic (ROC) analysis. Luminal stenosis >70% on coronary angiography was used as a reference standard.

RESULTS

On coronary angiography, 70% or greater diameter stenosis of the coronary artery was observed in 21 (52.5%) of 40 patients. The areas under the ROC curve for detection of significant stenosis in the individual coronary artery were 0.86 (observer 1) and 0.84 (observer 2) for MRI. These values were 0.79 (observer 1, p = not significant) and 0.72 (observer 2, p = not significant) for 201Tl SPECT.

CONCLUSION

The diagnostic accuracy of stress perfusion MRI acquired with saturation-recovery-prepared turbo FLASH was comparable with that of stress 201Tl SPECT. Stress first-pass contrast-enhanced MRI is a noninvasive technique that can be used as an alternative to stress myocardial perfusion scintigraphy.

Noninvasive detection of coronary allograft vasculopathy by myocardial contrast echocardiography

BACKGROUND

Noninvasive detection of coronary allograft vasculopathy is still challenging. To determine the accuracy of myocardial contrast echocardiography (MCE) in detecting coronary allograft vasculopathy after heart transplantation, we studied 35 asymptomatic patients (30 men, aged 46 +/- 12.7 years) with normal left ventricular function.

METHODS

Patients underwent MCE with continuous contrast (perfluorocarbon-exposed sonicated dextrose albumin) administration. Images were obtained at baseline and during peak dobutamine (up to 40 mg/kg/min) with intermittent harmonic imaging. Areas failing to increase contrast enhancement during peak stress were regarded as abnormal. Coronary artery obstructions greater than 50% at angiography were considered significant.

RESULTS

Seven out of 10 patients with coronary artery disease had a positive MCE and one patient with a positive MCE had no angiographically detected disease (sensitivity = 70%, specificity = 96%, accuracy = 88.6%). Agreement between the vascular territory and perfusion defects was good for the left anterior descending coronary artery (kappa = 0.56), but not for other arteries. Although 5 patients had multivessel disease, multiple perfusion defects were detected in only one patient.

CONCLUSION

MCE showed good accuracy in detecting the presence of coronary allograft vasculopathy after heart transplantation; however, it failed to identify the extent of the disease.

Cardiac positron emission tomography imaging

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. The combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification. Evaluation of the clinical role of these creative new possibilities warrants investigation.

Myocardial perfusion scintigraphy: the evidence

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by comparison with the numbers of revascularisations and coronary angiograms performed. Furthermore, MPS activity levels in this country fall far short of those in comparable European countries, with about half as many scans being undertaken per year. Currently, the number of MPS studies performed annually in the UK is 1,200/million population/year. We estimate the real need to be 4,000/million/year. The current average waiting time is 20 weeks and we recommend that clinically appropriate upper limits of waiting time are 6 weeks for routine studies and 1 week for urgent studies.

Noninfarcted myocardium: correlation between dynamic first-pass contrast-enhanced myocardial MR imaging and quantitative coronary angiography

PURPOSE

To determine the accuracy of first-pass contrast material-enhanced stress myocardial magnetic resonance (MR) imaging for depiction of myocardial ischemia in patients without myocardial infarction.

MATERIALS AND METHODS

First-pass contrast-enhanced MR images of the entire left ventricle were acquired in 104 patients at rest and during dipyridamole-induced stress by using an interleaved notched saturation technique. Coronary angiography was performed in all patients, and stress perfusion single photon emission computed tomography (SPECT) was performed in 69 patients. Receiver operating characteristic curve analysis was performed to compare the diagnostic accuracies of first-pass contrast-enhanced stress MR imaging and stress SPECT, with coronary angiography as the reference standard.

RESULTS

The overall sensitivity of MR imaging for depicting at least one coronary artery with significant stenosis was 90% (69 of 77 patients). The sensitivities of MR imaging for depiction of single-, double-, and triple-vessel stenoses were 85% (33 of 39 patients), 96% (22 of 23 patients), and 100% (15 of 15 patients), respectively. The specificity of MR imaging for identification of patients with significant coronary artery stenoses was 85% (23 of 27 patients). The areas under the receiver operating characteristic curve for detection of significant stenosis in individual coronary arteries were 0.888 (observer 1) and 0.911 (observer 2) for MR imaging and 0.707 (observer 1, P <.001) and 0.750 (observer 2, P <.001) for SPECT.

CONCLUSION

In patients without myocardial infarction, stress enhancement at dynamic MR imaging correlates more closely with quantitative coronary angiography results than does stress enhancement at SPECT.

Correct spatial normalization of myocardial perfusion SPECT improves detection of multivessel coronary artery disease

BACKGROUND

This study sought to improve the detection of multivessel coronary artery disease (CAD) with the use of rest and exercise single photon emission computed tomography (SPECT) perfusion scintigraphy by developing a processing scheme, which provides proper regional normalization of the images for interpretation. When SPECT perfusion images are interpreted, one area of myocardium serves as "normal." We hypothesized that if this "normal" region changes location from rest to stress, the stress images must be adjusted for proper interpretation. By taking into account the level of tracer activity in this "normal" area on the resting images, we could more accurately identify patients with multivessel CAD. Methods and results Dual-isotope rest (thallium 201) and exercise dobutamine or adenosine stress (technetium 99m sestamibi) perfusion SPECT studies were examined in 258 patients with 2- or 3-vessel CAD on coronary arteriography performed within 6 months of each other (mean interval, 19 days). If a shift in regional location of the "normal" segment from rest to stress was present, the images were (1) interpreted in the usual fashion for the number of vessels with ischemia (PRE-NORM) and (2) reinterpreted after quantitative normalization (ie, adjusting the display window until the intensity of the "normal" segment was matched at rest and stress [POST-NORM]). Interpretation was performed with blinding to arteriographic results. An angiographic stenosis was defined as luminal diameter stenosis greater than 50%. Three control groups comprising (1) single-vessel CAD (n = 119), (2) no significant angiographic CAD (n = 118), and (3) a normalcy group of low pre- and post-test probability of CAD (n = 44) were also studied to determine the incidence of false-positive results induced by the renormalization technique. A shift in the "normal" segment occurred in 81 studies of 258 patients (31%), 80 of which were read as abnormal PRE-NORM (sensitivity, 99%); however, for their 216 stenosed vessels, only 143 were detected PRE-NORM (vessel sensitivity, 66%; accuracy, 65%). The mean POST-NORM change in the display was 11%. POST-NORM, all 82 patients' studies were interpreted as abnormal (sensitivity, 100%), and 196 of 216 vascular territories were abnormal (vessel sensitivity, 91%; accuracy, 83%; both P <.0001 vs PRE-NORM). In the single-vessel disease, no significant disease, and normalcy groups, 19 of 119, 15 of 118, and 11 of 44 patients, respectively, demonstrated a shift in the peak pixel location. However, there were no significant changes in single-vessel sensitivity, angiographic specificity, or normalcy in these patients.

CONCLUSIONS

With multivessel CAD, the "normal" region on SPECT often changes in location from rest to stress, potentially masking the extent and severity of multivessel ischemia. Renormalization of the images to match their resting level before image interpretation allows diagnosis of contralateral ischemia and strikingly improves the detection of multivessel CAD, without a substantive loss in specificity.

Pharmacologic stress testing for coronary disease diagnosis: A meta-analysis

BACKGROUND

Although noninvasive pharmacologic stress tests are widely used, their relative performance is not clear. We compared the performance of pharmacologic stress tests combined with echocardiography or nuclear imaging for the diagnosis of coronary disease.

METHODS

We performed a regression meta-analysis of published data. We included studies published between January 1975 and June 1999 in which subjects underwent echocardiographic or single-photon emission computed tomography (SPECT) stress testing with adenosine, dipyridamole, or dobutamine for diagnosis of coronary artery disease. All subjects also underwent coronary angiography. Two independent reviewers abstracted population characteristics, technical factors, methodologic factors, and results and calculated test sensitivity and specificity.

RESULTS

Eighty-two studies met the inclusion criteria. The sensitivity of dipyridamole SPECT imaging, 89% (95% CI, 84%-93%), was higher than that of dipyridamole echocardiography, but the specificity of dipyridamole SPECT imaging, 65% (95% CI, 54%-74%), was lower than that of dipyridamole echocardiography. Dipyridamole and adenosine tests had similar sensitivities and specificities. The sensitivity of dobutamine echocardiography, 80% (95% CI, 77%-83%) was similar to that of dobutamine SPECT imaging, but dobutamine echocardiography had a higher specificity, 84% (95% CI, 80%-86%) than dobutamine SPECT imaging did.

CONCLUSIONS

The findings of our study can be used to guide the selection of the optimal pharmacologic stress test for each patient. Maximum sensitivity can be attained by use of a vasodilator combined with SPECT imaging. Maximum specificity can be attained by use of a vasodilator with echocardiography. The highest combination of sensitivity and specificity can be attained with dobutamine echocardiography.

Tolerance and diagnostic accuracy of an abbreviated adenosine infusion for myocardial scintigraphy: a randomized, prospective study

BACKGROUND

The objectives of this study were 2-fold: (1) to determine the tolerance of adenosine perfusion tomography with the use of an abbreviated (3-minute) infusion in comparison to the standard (6-minute) infusion, and (2) to assess the relative diagnostic accuracy of a 3-minute adenosine infusion in patients referred for arteriography. An abbreviated adenosine infusion may decrease the frequency and duration of side effects and be a more cost-effective alternative.

METHODS AND RESULTS

We prospectively randomized 599 patients undergoing adenosine myocardial perfusion tomography to either a 3-minute or 6-minute adenosine infusion at 140 microg/kg per minute. Among the 599 enrolled patients, 142 subsequently underwent coronary angiography. Patients randomized to the 3-minute adenosine infusion tolerated the procedure better than those randomized to the standard infusion (P <.01). Flushing, headache, neck pain, and atrioventricular block were all significantly less frequent (P <.01) with the abbreviated infusion. Moreover, patients receiving the abbreviated infusion had less hypotension and tachycardia (P <.05). The sensitivity of the test for detection of coronary artery disease was 88% for both the 3- and 6-minute infusions. In patients with abnormal scan results, perfusion defect size was slightly larger in those receiving a 6-minute infusion versus those receiving a 3-minute infusion (P =.05).

CONCLUSIONS

An abbreviated 3-minute adenosine infusion, in combination with perfusion tomography, has similar sensitivity for detection of coronary artery disease and is better tolerated than the standard 6-minute infusion.

Exercise myocardial perfusion scintigraphy is useful for evaluating myocardial ischemia even in the elderly

Pharmacologic stress testing is recommended to elderly patients as a valuable alternative to exercise testing. We examined whether exercise testing is as useful for evaluating myocardial ischemia in the elderly as in the young. The consecutive 1,508 patients who underwent exercise 201Tl single-photon emission computed tomography (SPECT) were divided into six age groups: 6-29 years (n = 56), 30-44 (n = 143), 45-54 (n = 311), 55-64 (n = 498), 65-74 (n = 402), and 75-88 (n = 98). Both heart rate and rate-pressure product at peak exercise were significantly lower in patients aged 75-88 than in the other five groups. The frequency of ischemic ST depression was higher in patients aged 75-88 than in those aged 6-74, although the difference was not significant. Moreover, the frequency of 201Tl transient defect was significantly higher in patients aged 75-88 than in those aged 6-74. On the other hand, the sensitivity of ischemic ST depression for 201Tl transient defect was similar among the six groups, but the specificity was significantly lower in patients aged 75-88 than in those aged 6-74. In conclusion, exercise 201Tl SPECT is useful for evaluating myocardial ischemia even in the elderly, but exercise electrocardiography has limitations such as lower specificity in the elderly than 201Tl SPECT.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Severity of coronary artery calcification by electron beam computed tomography predicts silent myocardial ischemia

BACKGROUND

Detection of subclinical coronary artery disease (CAD) before the development of life-threatening cardiac complications has great potential clinical relevance. Electron beam computed tomography (EBCT) is currently the only noninvasive test that can detect CAD in all stages of its development and thus has the potential to be an excellent screening technique for identifying asymptomatic subjects with underlying myocardial ischemia.

METHODS AND RESULTS

Over 2.5 years, we prospectively studied 3895 generally asymptomatic subjects with EBCT, 411 of whom had stress myocardial perfusion tomography (SPECT) within a close (median, 17 days) time period. SPECT and exercise treadmill results were compared with the coronary artery calcium score (CACS) as assessed by EBCT. The total CACS identified a population at high risk for having myocardial ischemia by SPECT although only a minority of subjects (22%) with an abnormal EBCT had an abnormal SPECT. No subject with CACS <10 had an abnormal SPECT compared with 2.6% of those with scores from 11 to 100, 11.3% of those with scores from 101 to 399, and 46% of those with scores >/=400 (P<0.0001). CACS predicted an abnormal SPECT regardless of subject age or sex.

CONCLUSIONS

CACS identifies a high-risk group of asymptomatic subjects who have clinically important silent myocardial ischemia. Our results support the role of EBCT as the initial screening tool for identifying individuals at various stages of CAD development for whom therapeutic decision making may differ considerably.

Adenosine as an adjunct to thrombolytic therapy for acute myocardial infarction: results of a multicenter, randomized, placebo-controlled trial: the Acute Myocardial Infarction STudy of ADenosine (AMISTAD) trial

OBJECTIVES

The Acute Myocardial Infarction STudy of ADenosine (AMISTAD) trial was designed to test the hypothesis that adenosine as an adjunct to thrombolysis would reduce myocardial infarct size.

BACKGROUND

Reperfusion therapy for acute myocardial infarction (MI) has been shown to reduce mortality, but reperfusion itself also may have deleterious effects.

METHODS

The AMISTAD trial was a prospective, open-label trial of thrombolysis with randomization to adenosine or placebo in 236 patients within 6 h of infarction onset. The primary end point was infarct size as determined by Tc-99 m sestamibi single-photon emission computed tomography (SPECT) imaging 6+/-1 days after enrollment based on multivariable regression modeling to adjust for covariates. Secondary end points were myocardial salvage index and a composite of in-hospital clinical outcomes (death, reinfarction, shock, congestive heart failure or stroke).

RESULTS

In all, 236 patients were enrolled. Final infarct size was assessed in 197 (83%) patients. There was a 33% relative reduction in infarct size (p = 0.03) with adenosine. There was a 67% relative reduction in infarct size in patients with anterior infarction (15% in the adenosine group vs. 45.5% in the placebo group) but no reduction in patients with infarcts located elsewhere (11.5% for both groups). Patients randomized to adenosine tended to reach the composite clinical end point more often than those assigned to placebo (22% vs. 16%; odds ratio, 1.43; 95% confidence interval, 0.71 to 2.89).

CONCLUSIONS

Many agents thought to attenuate reperfusion injury have been unsuccessful in clinical investigation. In this study, adenosine resulted in a significant reduction in infarct size. These data support the need for a large clinical outcome trial.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Pharmacological stress testing

Pharmacological stress in conjunction with radionuclide myocardial perfusion imaging has become a widely used noninvasive method of assessing patients with known or suspected coronary artery disease. In the United States, over one third of perfusion imaging studies are performed with pharmacological stress. Pharmacological stress agents fall into two categories: coronary vasodilating agents such as dipyridamole and adenosine, and cardiac positive inotropic agents such as dobutamine and arbutamine. For both, in the presence of coronary artery disease (CAD), perfusion image abnormalities result from heterogeneity of coronary blood flow reserve. Vasodilating agents work directly on the coronary vessels to increase blood flow, whereas inotropic agents work indirectly by increasing myocardial work load, which then leads to an increase in coronary blood flow. Both classes of agents have high accuracies for diagnosing coronary artery disease, and they have excellent safety records with acceptably low occurrences of side effects. For dipyridamole planar thallium imaging, pooled analysis yields a sensitivity of 85% and a specificity of 87% for diagnosis of coronary disease, but there is a large variation in reported values depending on various factors, such as the extent of postcatheterization referral bias, the type of imaging (planar versus single photon emission computed tomography [SPECT]), the types of patients being studied (single versus multivessel disease, men versus women), and the imaging agent used (thallium versus one of the technetium-based agents). Diagnostic accuracies for adenosine are similar to those of dipyridamole, with reported overall sensitivities ranging from 83% to 97%, and specificities ranging from 38% to 94%. For dobutamine, pooled analyses yield a sensitivity of 82% and a specificity of 75%. There is some concern that dobutamine may interfere with uptake of technetium-99m sestamibi, lowering the sensitivity for detection of disease, and thus the vasdodilating agents are generally preferred. Pharmacological stress testing has high clinical use for risk stratifying patients with known or suspected CAD, in patients after myocardial infarction, and in patients needing noncardiac surgery. Vasodilating agents are particularly advantageous in assessing post-myocardial infarction patients, allowing testing as soon as 2 days after the event. Like patients undergoing exercise stress testing, patients with normal perfusion images by pharmacological stress have a <1% annual incidence of cardiac events. The likelihood of an event increases with the extent and severity of perfusion abnormalities. However, it is important to consider clinical variables when using perfusion imaging for risk stratification, particularly in the presurgery patients. As with exercise testing, adjunct markers such as ST segment depression during testing, lung uptake of radiotracer (if thallium is used), and ventricular cavity dilatation add additional prognostic information to that available from the perfusion images alone. The aim of current research is to find better agents that are easier to use and that have fewer side effects. MRE-0470 is an experimental vasodilating agent that is more receptor selective than adenosine and promises a lower incidence of hypotension. Arbutamine more closely simulates exercise than dobutamine, and it can be administered by a closed-loop computerized delivery device. Work is also underway to look at novel uses of pharmacological stress agents, such as acquiring gated SPECT images during dobutamine infusion to enhance detection of myocardial viability. With increasing use of noninvasive testing in elderly patients and in patients with comorbidities that preclude adequate exercise, pharmacological stress testing has become an indispensable tool for radionuclide myocardial perfusion imaging studies. A good understanding of pharmacological stress testing is essential for performing high-quality nuclear cardiology

Stress myocardial perfusion imaging versus echocardiography for the diagnosis and risk stratification of patients with known or suspected coronary artery disease

Stress perfusion imaging and stress echocardiography (ECHO) are both very useful for assessment of diagnosis and risk stratification of patients with coronary artery disease (CAD). Both techniques have been well validated during exercise and inotropic stress, but coronary vasodilation stress is better used in combination with perfusion imaging. The overall sensitivity for detection of CAD is slightly higher by single photon emission computed tomography (SPECT) than by two-dimensional (2D) ECHO during all stress modalities, whereas the specificity is slightly higher by ECHO, although the differences in general are not statistically significant. SPECT, however, appears to be superior to ECHO in the diagnosis of isolated circumflex stenosis, as well as for the correct identification of multivessel CAD. A substantially greater amount of information is available regarding risk stratification with SPECT than with 2D ECHO. Although the data suggest that both techniques are very useful for risk stratification of patients with stable CAD, after myocardial infarction, and for preoperative risk stratification, the risk for cardiac events is lower in the presence of a normal stress SPECT study than of a normal stress ECHO.

Intracoronary flow velocity measurements in adjacent stenotic and normal coronary arteries during incremental intravenous dobutamine stress and intracoronary adenosine injection

To investigate the concomitant coronary flow and hemodynamic changes induced by dobutamine and adenosine in the catheterization laboratory, we studied stenotic and adjacent normal coronary arteries in 20 patients using paired Doppler Flowires. Coronary flow velocity and hemodynamics were measured sequentially after intracoronary (ic) adenosine, during incremental iv dobutamine infusion, and after the addition of ic adenosine during sustained peak dobutamine stress (adenosine on dobutamine). Distal to stenotic arteries, average peak velocity (APV) increased significantly (from 11 +/- 5 to 16 +/- 7 cm/sec, P < 0.001) at an intermediate dose of dobutamine (20 microg/kg/min, Dobutamine20) but did not change further thereafter to peak dobutamine stress (17 +/- 7 cm/sec), despite the significant further increase in rate-pressure product (RPP). Peak stress APV did not change with adenosine on dobutamine (to 18 +/- 7 cm/sec). In normal arteries, APV increased at Dobutamine20 (from 20 +/- 7.5 to 30 +/- 12 cm/sec, P < 0.01) and further at peak dobutamine stress (to 42 +/- 10 cm/sec, P < 0.0001) always exceeding the concomitant significant increases in RPP. Peak stress APV increased further with adenosine on dobutamine (to 53 +/- 13 cm/sec, P < 0.001). Our data demonstrate that at peak dobutamine stress there is supply/demand mismatch only in stenotic arteries where coronary flow reserve is exhausted at an intermediate dobutamine dose. Furthermore, adenosine on dobutamine potentiates coronary flow heterogeneity between stenotic and normal adjacent arteries. Cathet. Cardiovasc. Intervent. 48:1-9, 1999.

Assessment of the severity of coronary artery stenosis by the ratio of the regional washout rate determined by adenosine triphosphate stress Tl-201 SPECT

BACKGROUND

Adenosine triphosphate stress thallium-201 single-photon emission computed tomography (ATP SPECT) is useful for diagnosis of coronary artery disease, but its usefulness for evaluating the severity of coronary artery stenosis has not been established.

METHODS AND RESULTS

We performed region-of-interest analysis of short-axis images obtained by ATP SPECT in 31 patients with single-vessel disease (>50% stenosis of the luminal diameter). We selected the lowest and highest washout rates (WR) among the anterior, lateral, and inferior WRs and calculated the ratio of the lowest WR to the highest WR (WR ratio = 0.925+/-0.027 in 14 control subjects). ATP SPECT showed positive results in 29 (94%) of 31 patients. The severity of coronary artery stenosis was inversely correlated with the WR ratio (r = -0.703, P < .0001). The sensitivity and specificity of a WR ratio < or = 0.660 for the diagnosis of severe coronary stenosis (> or =80% stenosis) were 83% and 80%, respectively.

CONCLUSIONS

Results suggest that ATP SPECT may be useful for assessment of the severity of coronary artery stenosis in patients with single-vessel disease.

Combined Tc-99m sestamibi first-pass radionuclide angiography and cardiac SPECT imaging during arbutamine infusion delivered by a computerized closed-loop system

PURPOSE

This study evaluated the feasibility, hemodynamic responses, and relation of combined Tc-99m sestamibi SPECT imaging and first-pass radionuclide angiography during the infusion of a new beta agonist arbutamine.

METHODS

Arbutamine was administered to 15 patients and constantly adjusted by a closed-loop computerized system. Rest and arbutamine Tc-99m sestamibi radionuclide angiography was performed with a multicrystal gamma camera followed by SPECT imaging with a rotating triple-head, single-crystal gamma camera.

RESULTS

The mean differences (paired t-test) between rest and arbutamine studies for heart rate (HR), end-diastolic volume (EDV), stroke volume (SV), cardiac output (CO), and ejection fraction (EF) were as follows: 55 bpm for HR (P < 0.001), 5 ml for EDV (P=ns), 7.5 ml for SV (P=0.04), 4.4 l/min for CO (P < 0.001), and 6.4% for EF (P < 0.001), respectively. The results of SPECT studies were abnormal in six patients and normal in nine. Findings of radionuclide angiography were normal in 12 patients and abnormal in three. Interpretation of the perfusion and functional studies were concordant in 10 and discordant in five patients.

CONCLUSIONS

Simultaneous cardiac radionuclide angiography and SPECT imaging are feasible during arbutamine infusion. This potent beta agonist increases cardiac output through a chronotropic effect with no significant changes in EDV. The discordance in SPECT and radionuclide angiography results may represent incremental diagnostic and prognostic information provided by both studies.

Clinical review of attenuation-corrected cardiac SPECT

Rather than the introduction of a heralded technologic advancement in cardiac SPECT imaging challenging the accuracy of PET perfusion imaging, the commercial introduction of attenuation correction has been met with at least as many negative as positive reports. Some studies have reported significant improvements in specificity or specificity and sensitivity, especially for high-risk patterns of coronary artery disease; others have reported no improvement or a decrease in accuracy resulting from the introduction of troublesome artifacts. Although this review has attempted to emphasize the positive aspects of attenuation-corrected cardiac SPECT perfusion imaging and the potential for improved patient care it may provide, several negative reports continue to appear. Still there has been sufficient positive data reported to suggest that with fully developed, accurate, and robust correction methods, significant gains in SPECT assessments of the presence and extent of CHD, patient risk, and myocardial viability can be anticipated. Ultimately attenuation correction for cardiac SPECT should have a positive impact on the management of patients with coronary artery disease with important savings in lives and health care dollars.

Underestimation of extent and severity of coronary artery disease by dipyridamole stress thallium-201 single-photon emission computed tomographic myocardial perfusion imaging in patients taking antianginal drugs

OBJECTIVES

This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 single-photon emission computed tomography (SPECT) in patients taking antianginal drugs.

BACKGROUND

Dipyridamole stress is the major substitute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exercise, dipyridamole stress is usually performed without discontinuing these drugs.

METHODS

Twenty-six patients underwent two dipyridamole perfusion studies: the first without (SPECT-1) and the second with (SPECT-2) antianginal treatment. Twenty-one patients (81%) received calcium antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-blockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD.

RESULTS

Visual scoring yielded significantly larger and more severe reversible perfusion defects for SPECT-1 than for SPECT-2. Quantitative analysis showed larger perfusion defects on stress images of SPECT-1 in the left anterior descending coronary artery (LAD) (25 +/- 21% vs. 17 +/- 15%, p = 0.003), left circumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and RCA territories were 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% for SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall individual vessel sensitivity of SPECT-1 was significantly higher than that of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not significantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0.33).

CONCLUSIONS

Continued use of antianginal drugs before dipyridamole plus low level treadmill exercise thallium-201 SPECT may reduce the extent and severity of myocardial perfusion defects, resulting in underestimation of coronary artery disease.

Diagnostic accuracy of stress thallium-201 tomography in patients with left ventricular hypertrophy

Two hundred patients with echocardiographically proven left ventricular hypertrophy underwent quantitative stress thallium tomography. The overall sensitivity and specificity were high (84% and 82%, respectively).

Adenosine technetium-99m sestamibi single-photon emission tomography for the assessment of jeopardized myocardium early after acute myocardial infarction. Paradoxical scintigraphic underestimation of jeopardized myocardium in patients with a severe infarct-related stenosis

This study investigated the value of technetium-99m sestamibi scintigraphy in identifying patients at risk for post-infarct ischaemia (=jeopardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (<1 month) myocardial infarction, adenosine 99mTc-sestamibi single-photon emission tomography (SPET) and dobutamine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter stenosis (DS) >50%] on quantitative coronary angiography. Regional perfusion activity was analysed semi-quantitatively (score 0-4) on a 13-segment left ventricular model. DSE was used for the estimation of the infarct size (low-dose DSE) and for concomitant evaluation of ischaemia (high-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-related lesion (sensitivity of 54%) and only in one patient without a significant infarct-related lesion (specificity of 93%). Further analysis revealed that the scintigraphic assessment of jeopardized myocardium was fairly good in patients with a moderate (DS 51%-64%) infarct-related stenosis but was inadequate in patients with a severe (DS>/=65%) infarct-related stenosis (sensitivity of 80% vs 36%, P<0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups). This scintigraphic underestimation of jeopardized myocardium was mainly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perfusion score in the infarct region in patients with a severe stenosis as compared to those with a moderate stenosis (average score: 1.5+/-0.7 vs 2.1+/-0.6, P<0.01), while infarct size on echocardiography was similar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine 99mTc-sestamibi SPET may underestimate reperfused but still jeopardized myocardium, particularly in patients with a severe infarct-related stenosis. In these patients the evaluation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in resting conditions.

Adenosine thallium-201 tomography in evaluation of graft patency late after coronary artery bypass graft surgery

OBJECTIVES

We sought to ascertain the utility of adenosine thallium-201 tomography for assessing graft stenoses late after coronary artery bypass graft surgery.

BACKGROUND

Although pharmacologic perfusion imaging has been increasingly used in the assessment of patients with coronary artery disease, the value of this stress modality for detecting coronary artery bypass graft stenosis late after surgery is unknown.

METHODS

We studied 109 patients who underwent both adenosine thallium-201 tomography and coronary angiography at 6.7 +/- 4.8 (mean +/- SD) years after coronary artery bypass graft surgery. Adenosine thallium-201 tomography was assessed quantitatively by computer-generated polar maps of the myocardial thallium-201 activity.

RESULTS

On coronary angiography, significant graft stenoses were present in 68 patients, 65 of whom had a corresponding perfusion defect as shown by thallium-201 tomography (sensitivity 96%). Significant stenoses were present in 107 (37.8%) of 283 grafts. The overall specificity by quantitative tomography was 61%. Seventy percent of the apparently false positive perfusion defects could be explained on the basis of unbypassed native disease or by the presence of fixed defects in patients with previous myocardial infarction.

CONCLUSIONS

Thus, results of adenosine thallium-201 tomography are nearly always abnormal in patients with late coronary graft stenosis. Most of the false positive defects appear to be due to either unbypassed native disease or a previous myocardial infarction.

Relation between ambulatory electrocardiographic monitoring and myocardial perfusion imaging to detect coronary artery disease and myocardial ischemia: an ACIP ancillary study. The Asymptomatic Cardiac Ischemia Pilot (ACIP) Investigators

OBJECTIVES

This study sought to explore the relation between markers of ischemia detected by ambulatory electrocardiographic (AECG) monitoring and stress myocardial perfusion single-photon emission computed tomography (SPECT).

BACKGROUND

Stress myocardial SPECT and AECG monitoring are both utilized in evaluating patients with coronary artery disease. However, information is limited regarding the relation between the presence and extent of ischemia as detected by these two modalities.

METHODS

This was an ancillary study of the Asymptomatic Cardiac Ischemia Pilot (ACIP) trial. One hundred six patients with previous coronary angiography underwent AECG monitoring and stress SPECT within a close temporal time period. The frequency and duration of ischemia as assessed by AECG monitoring and the total and ischemic stress-induced myocardial perfusion defect sizes as assessed by SPECT were quantified in separate core laboratories. Multivariate logistic regression and linear regression analysis were used to determine associations between AECG and SPECT abnormalities with regard to angiographic, demographic and treadmill exercise variables.

RESULTS

Seventy-four percent of patients with significant (> or = 50%) coronary artery stenosis had SPECT abnormalities, whereas 61% had ischemia by AECG monitoring. The most important predictors of SPECT abnormalities were severity (p < 0.001) of coronary artery stenosis, followed by total exercise duration (p = 0.016) and patient age (p = 0.04). The only predictor of AECG abnormalities was the presence of ST segment depression on the initial exercise treadmill test (p = 0.021). Only a 50% concordance for normalcy or abnormalcy was observed between the SPECT and AECG results, and no relation was observed between the frequency or duration of AECG ischemia and the quantified total or ischemic myocardial perfusion defect size as assessed by SPECT.

CONCLUSIONS

Ischemia as detected by AECG monitoring does not correlate with the presence and extent of ischemia as quantified by stress SPECT. Because these techniques appear to detect different pathophysiologic manifestations of ischemia, they may be complementary in more fully defining the functional significance of coronary artery disease and, in particular, which patients are at highest risk for adverse cardiac events.