Adenosine versus regadenoson comparative evaluation in myocardial perfusion imaging: Results of the ADVANCE phase 3 multicenter international trial

BACKGROUND

Earlier phase 1 and 2 studies have shown that regadenoson has desirable features as a stress agent for myocardial perfusion imaging.

METHODS AND RESULTS

This multicenter, double-blinded phase 3 trial involved 784 patients at 54 sites. Each patient underwent 2 sets of gated single photon emission computed tomography myocardial perfusion imaging studies: an initial qualifying study with adenosine and a subsequent randomized study with either regadenoson (2/3 of patients) or adenosine. Regadenoson was administered as a rapid bolus (<10 seconds) of 400 mug. The primary endpoint was to demonstrate noninferiority by showing that the difference in the strength of agreement in detecting reversible defects, based on blinded reading, between sequential adenosine-regadenoson images and adenosine-adenosine images, lay above a prespecified noninferiority margin. Other prospectively defined safety and tolerability comparisons and supporting analyses were also performed. The average agreement rate based on the median of 3 independent blinded readers was 0.63 +/- 0.03 for regadenoson-adenosine and 0.64 +/- 0.04 for adenosine-adenosine-a 1% absolute difference with the lower limit of the 95% confidence interval lying above the prespecified noninferiority margin. Side-by-side interpretation of regadenoson and adenosine images provided comparable results for detecting reversible defects. The peak increase in heart rate was greater with regadenoson than adenosine, but the blood pressure nadir was similar. A summed symptom score of flushing, chest pain, and dyspnea was less with regadenoson than adenosine (P = .013).

CONCLUSIONS

This phase 3 trial shows that regadenoson provides diagnostic information comparable to a standard adenosine infusion. There were no serious drug-related side effects, and regadenoson was better tolerated than adenosine.

A comparison of Tl-201, Tc-99m sestamibi, and Tc-99m tetrofosmin myocardial perfusion scintigraphy in patients with mild to moderate coronary stenosis

BACKGROUND

Thallium 201, technetium 99m sestamibi (MIBI), and Tc-99m tetrofosmin differ in their myocardial uptake characteristics. This may make the technetium tracers less sensitive for detecting mild to moderate coronary stenosis.

METHODS AND RESULTS

We identified 163 patients with angiographic mild to moderate stenosis (50%-89%) and coexistent severe disease (88/163 patients) from a previous study of patients who received either thallium, MIBI, or tetrofosmin for myocardial perfusion scintigraphy. Summed segmental uptake scores were used to assess myocardial perfusion of territories supplied by the mildly to moderately stenotic vessels. Mean (+/- SD) summed stress uptake scores in the left anterior descending artery territory were 21.4 +/- 3.8, 21.6 +/- 4.2, and 22.1 +/- 2.3 for thallium, MIBI, and tetrofosmin, respectively (P = .7); mean summed difference uptake scores were 1.2 +/- 1.8, 1.1 +/- 1.9, and 1.0 +/- 1.1, respectively (P = .8). In the non-left anterior descending artery territory, mean summed stress uptake scores were 32.5 +/- 6.3, 34.0 +/- 6.3, and 34.5 +/- 4.7 for thallium, MIBI, and tetrofosmin, respectively (P = .4), whereas mean summed difference scores were 1.9 +/- 2.6, 1.7 +/- 2.2, and 1.7 +/- 2.3, respectively (P = .9).

CONCLUSION

There were no significant differences between the tracers for the summed uptake scores. This suggests that the 3 tracers are comparable in clinical practice for assessing the extent and severity of perfusion abnormalities arising from mild to moderate coronary artery stenosis, especially in the presence of coexistent severe disease.

Patient gender and radiopharmaceutical tracer is of minor importance for the interpretation of myocardial perfusion images using an artificial neural network

The purpose of this study was to assess the influence of patient gender and choice of perfusion tracer on computer-based interpretation of myocardial perfusion images. For the image interpretation, an automated method was used based on image processing and artificial neural network techniques. A total of 1000 patients were studied, all referred to the Royal Brompton Hospital in London for myocardial perfusion scintigraphy over a period of 1 year. The patients were randomized to receive either thallium or one of the two technetium tracers, methoxyisobutylisonitrile or tetrofosmin. Artificial neural networks were trained with either mixed gender or gender-specific and mixed tracer or tracer-specific training sets of different sizes. The performance of the networks was assessed in separate test sets, with the interpretation of experienced physicians regarding the presence or absence of fixed or reversible defects in the images as the gold standard. The neural networks trained with large mixed gender training sets were as good as the networks trained with gender-specific data sets. In addition, the neural networks trained with large mixed tracer training sets were as good as or better than the networks trained with tracer-specific data sets. Our results indicate that the influence of patient gender and perfusion tracer are of minor importance for the computer-based interpretation of the myocardial perfusion images. The differences that occur can be compensated for by larger training sets.

Continued axillary sampling is unnecessary and provides no further information to sentinel node biopsy in staging breast cancer

INTRODUCTION

Sentinel lymph node biopsy (SLNB) has become increasingly accepted as a diagnostic method to stage the axilla in breast cancer, selecting women with a positive sentinel node for completion axillary clearance. As SLNB became established, many surgeons supplemented SLNB to sample a minimum of four lymph nodes, on the assumption that the four-node technique is supported by randomised trial data. We hypothesised that the practice of undirected sampling to supplement SLNB adds little information to the status of the residual axilla.

METHODS

One hundred and sixty-five patients with early breast cancer were studied. Following successful identification of the sentinel node, 84 women had completion axillary dissection and 81 women had an axillary sample with at least four nodes available for pathological assessment.

RESULTS

Following successful identification of the sentinel node in 165 patients, the false negative rate (FNR) was 2/44=4.5% (95% CI 0.6-15.5), sensitivity 42/44=95.5% (84.5-99.4) and negative predictive value (NPV) 121/123=98.4% (94.2-99.8). In the axillary dissection cohort, the FNR was 2/26=7.7% (0.9-25.1), sensitivity 24/26=92.3% (74.9-99.1) and NPV 58/60=96.7% (88.5-100). In the axillary sample group, the FNR was 0/18=0% (0-18.5), sensitivity 18/18=100% (81.5-100) and NPV 63/63=100% (94.3-100). The SLNB was the only positive node in 12/26 (46.2%) in the axillary dissection group and 10/18 (55.6%) in the axillary sampling group. There was no patient in the axillary sampling group where the sample node was positive and the sentinel node negative.

CONCLUSION

Once SLNB is validated within the multidisciplinary unit, undirected sampling of the axilla following identification of the sentinel node(s) is unnecessary. The additional sampling of non-sentinel nodes has no role to play either in the assessment of a potential false negative SLNB nor as predictive information on the status of the residual axillary nodes.

Myocardial perfusion scintigraphy in the UK: insights from the British Nuclear Cardiology Society Survey 2000

BACKGROUND

The National Institute for Health and Clinical Excellence (NICE) has recently published a very positive technology appraisal of myocardial perfusion scintigraphy (MPS). This has important implications for service provision within the National Health Service, and an accurate knowledge of the current level of MPS activity is necessary.

METHODS

A postal questionnaire was sent to 207 nuclear medicine departments in the UK, requesting information about nuclear cardiology facilities, activity, and practice. Non-responding departments were sent a second questionnaire, followed where necessary by a telephone call.

RESULTS

A response rate of 61% was achieved; 52% of departments performed MPS, and these tended to have more gamma cameras than those which did not (median (25th-75th centile) 2.0, 1.5-2.5 v 1.0, 0.5-1.5; p = 0.02). The median number of studies performed was 256 (144-460). The estimated rate of MPS in the UK for the year 2000 was 1200 per million population. The median (25th-75th centile) waiting time for MPS was 16 (9-24) weeks. Pharmacological stress was used in 77% of studies, and a technetium-99m based radiopharmaceutical in 60% (two day protocol in 75%). Tomographic rather than planar imaging was performed in 88% of studies, of which 22% were ECG gated. A cardiologist was involved in reporting in 35% of studies.

CONCLUSIONS

MPS activity in the UK remains low, and it tends to be provided as a low volume service with unacceptably long waiting times and a lack of involvement by cardiologists. The recent NICE appraisal may provide an impetus for further resourcing and development.

Adjunctive role of cardiovascular magnetic resonance in the assessment of patients with inferior attenuation on myocardial perfusion SPECT

PURPOSE

Inferior attenuation is a common problem in the interpretation of myocardial perfusion SPECT. We explored whether cardiovascular magnetic resonance (CMR) was a useful adjunct in differentiating between artifactual attenuation of the inferior wall and the presence of myocardial infarction and/or ischemia.

METHODS

We used CMR to assess resting wall motion, myocardial perfusion, and the presence of infarction with late gadolinium enhancement in 30 patients with presumed inferior attenuation on ungated myocardial perfusion SPECT, but where uncertainty was present over interpretation of the inferior wall. Perfusion CMR was analyzed visually and quantitatively.

RESULTS

In 23 patients (77%), CMR excluded infarction or ischemia in the inferior wall. The myocardial perfusion reserve index (MPR1) was the same in the inferior and remote myocardium (1.74 +/- 0.43 vs. 1.77 +/- 0.50, p = 0.61). Coronary angiography was performed in 11 of these patients, and was normal in all cases. In the remaining seven subjects (23%), significant abnormality was detected by CMR (infarction, 5; wall motion abnormality, 3; perfusion defect, 5). In these patients, the MPR1 was reduced in the inferior myocardium compared with remote (1.07 +/- 0.19 vs. 1.74 +/- 0.49, p = 0.04). Coronary angiography was performed in three of these patients, revealing significant coronary disease in the artery supplying the inferior territory in all patients.

CONCLUSION

Approximately one-quarter of patients with inferior attenuation on ungated, nonattenuation corrected myocardial perfusion SPECT have abnormalities on CMR. CMR can readily distinguish between artifact, ischemia, and infarction in these cases and in some cases might obviate the need for diagnostic coronary angiography.

Procedure guidelines for radionuclide myocardial perfusion imaging

Radionuclide myocardial perfusion imaging (MPI) is an established and non-invasive imaging technique with diagnostic and prognostic efficacy in the investigation of coronary artery disease. It is the only widely available test for assessing myocardial perfusion directly but there are variations in the way it is performed in different centres. Harmonization of practice, at least at a national level, is therefore essential, and clinical governance now makes it mandatory for practice to be based upon evidence whenever possible [ 1]. This is best achieved by expert analysis of the evidence and to this end the British Nuclear Cardiology Society (BNCS) in association with the British Cardiac Society (BCS) and the British Nuclear Medicine Society (BNMS) have developed procedure guidelines for tomographic myocardial perfusion imaging. A systematic literature search was performed and every effort was made to conform with the AGREE recommendations [ 2]. All recommendations are therefore based on either evidence from clinical studies, previous published guidelines or expert consensus of the writing and advisory groups. The guidelines cover the clinical indications of MPI, the methods used for stress testing, the radiopharmaceuticals and the injected activities and also issues related to acquisition, processing and interpretation of images. They do not cover the benefits or drawbacks of the technique in specific circumstances; neither do they address its cost effectiveness in clinical diagnosis and management nor its potential impact on clinical outcomes. The guidelines aim to assist medical practitioners and other health care professionals in recommending, performing, interpreting and reporting single photon emission computed tomography (SPECT) of myocardial perfusion.

Imaging techniques for the assessment of myocardial hibernation Report of a Study Group of the European Society of Cardiology

This report of an ESC Study Group reviews current knowledge on myocardial hibernation and relevant imaging techniques, and provides an algorithm for investigation and management when a patient presents with ischaemic left ventricular dysfunction. It covers the definitions of myocardial viability, stunning and hibernation, it reviews the morphological findings in hibernation and it describes relevant clinical settings. The imaging and other techniques that are reviewed are electrocardiography, positron-emitting and single photon-emitting scintigraphic imaging, echocardiography, radionuclide angiocardiography, magnetic resonance imaging, X-ray transmission tomography, invasive X-ray angiocardiography and electromechanical mapping. The evidence for the techniques to predict improvement of regional and global function after revascularisation is summarised and patient symptoms and clinical outcome are also considered. Each technique is classified in its ability to assess myocardial viability, function and perfusion and also for their roles in the assessment of the patient with ischaemic left ventricular dysfunction who is asymptomatic or who has angina or heart failure. A simplified clinical algorithm describes the initial assessment of left ventricular function, then viability and then perfusion reserve allowing regions of myocardium to be characterised as transmural scar, intramural scar, hibernation or ischaemia.

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.

Characterization of the generation of radiolabeled monodisperse albuterol particles using the spinning-top aerosol generator

Inhaled radiolabeled aerosols provide invaluable information about in vivo drug deposition. Here, we report our methodology for radiolabeling and imaging monodisperse pharmacologic aerosols in order to study basic aerosol science concepts of drug delivery within the human airways.

METHODS

We used a spinning-top aerosol generator to produce (99m)Tc-labeled monodisperse albuterol sulfate aerosols of 1.5-, 3-, and 6- micro m mass median aerodynamic diameter.

RESULTS

In vitro Andersen cascade validation data showed that technetium and albuterol were coassociated on each impactor stage for all 3 aerosols, and the radiolabeling process itself did not affect their particle size distributions. Good-quality gamma-camera scintigraphic images of lung and extrathoracic deposition were obtained within an asthmatic patient.

CONCLUSION

We have successfully radiolabeled and imaged monodisperse albuterol aerosols within the human lungs. This novel technique provides an important tool to relate fundamental concepts of aerosol particle behavior, in vivo deposition, and therapeutic clinical response.

Effects of bronchodilator particle size in asthmatic patients using monodisperse aerosols

Aerosol particle size influences airway drug deposition. Current inhaler devices are inefficient, delivering a heterodisperse distribution of drug particle sizes where, at best, 20% reaches the lungs. Monodisperse aerosols are the appropriate research tools to investigate basic aerosol science concepts within the human airways. We hypothesized that engineering such aerosols of albuterol would identify the ideal bronchodilator particle size, thereby optimizing inhaled therapeutic drug delivery. Eighteen stable mildly to moderately asthmatic patients [mean forced expiratory volume in 1 s (FEV1) 74.3% of predicted] participated in a randomized, double-blind, crossover study design. A spinning-top aerosol generator was used to produce monodisperse albuterol aerosols that were 1.5, 3, and 6 microm in size, and also a placebo, which were inhaled at cumulative doses of 10, 20, 40, and 100 microg. Lung function changes and tolerability effects were determined. The larger particles, 6 and 3 microm, were significantly more potent bronchodilators than the 1.5-microm and placebo aerosols for FEV1 and for the forced expiratory flow between exhalation of 25 and 75% of forced vital capacity. A 20-microg dose of the 6- and 3-microm aerosols produced FEV1 bronchodilation comparable to that produced by 200 microg from a metered-dose inhaler. No adverse effects were observed in heart rate and plasma potassium. The data suggest that in mildly to moderately asthmatic patients there is more than one optimal beta2-agonist bronchodilator particle size and that these are larger particles in the higher part of the respirable range. Aerosols delivered in monodisperse form can enable large reductions of the inhaled dose without loss of clinical efficacy.

Comparison of equilibrium radionuclide ventriculography with cardiovascular magnetic resonance for assessing the systemic right ventricle after Mustard or Senning procedures for complete transposition of the great arteries

We assessed the utility of equilibrium radionuclide ventriculography for assessing function of the systemic right ventricle by comparing it with cardiovascular magnetic resonance (CMR) in subjects who had undergone the Mustard or Senning operations for complete transposition of the great arteries. The 95% limits of agreement for right ventricular ejection fraction by the 2 techniques were 15.8% to -16.0%, demonstrating that equilibrium radionuclide ventriculography has good agreement with CMR and provides a good alternative in cases in which CMR is not available or appropriate.

Coronary calcification and predicted risk of coronary heart disease in asymptomatic men with hypercholesterolaemia

OBJECTIVE

To document the relationship between coronary calcification and coronary risk assessed clinically in asymptomatic patients with hypercholesterolaemia.

DESIGN

Prospective observational study.

SETTING

Health screening clinic.

PATIENTS

A total of 286 asymptomatic men aged 45-64 with plasma cholesterol >or= 6.5 mmol/l.

INTERVENTIONS

Electron beam computed tomography to measure coronary calcium score.

MAIN OUTCOME MEASURES

The Framingham equation was used to separate subjects into groups with either low 10-year risk of coronary artery disease (<or= 10%) or high 10-year risk (>or= 20%). Coronary calcium score was assessed in each group.

RESULTS

The mean log calcium score was significantly higher in the 97 high-risk men than in the 189 low-risk men (1.58 +/- 0.84 versus 1.00 +/- 0.85, < 0.001). Arithmetic means (158 versus 55), and the proportion with a score > 400 (11% versus 2%, p < 0.01) were also greater. However, 27% of the high-risk group had a low calcium score (<or= 10), which is known to be associated with minimal coronary artery disease assessed by angiography.

CONCLUSIONS

Approximately one quarter of asymptomatic hypercholesterolaemic men aged 45 to 64 who have an estimated risk of coronary heart disease of >or= 20% in 10 years have minimal coronary calcification. They may therefore represent a subset at lower risk of disease. However, uncertainties about the predictive power of coronary calcification for coronary events must be resolved before electron beam computed tomography can be used to select high-risk patients for primary prevention.

A comparison of three radionuclide myocardial perfusion tracers in clinical practice: the ROBUST study

There are no large studies available to guide the selection of thallium (Tl), methoxyisobutylisonitrile (MIBI) or tetrofosmin (Tf) for myocardial perfusion imaging. Our objective was to compare the technical and clinical performance of the three in routine clinical practice. We randomised 2,560 patients to receive Tl, MIBI or Tf. A 1-day stress/rest protocol was used for MIBI and Tf. Tracer uptake was scored using a 17-segment model, quality and artefact scores were assigned, and ratios of heart (H), liver (L), subdiaphragmatic (S) and lung activity were measured. Mean quality scores (stress/rest) were Tl 2.13/2.16, MIBI 2.18/2.39, Tf 2.18/2.42 ( P=ns stress and <0.00001 rest). For attenuation artefact, Tl>MIBI=Tf ( P<0.05) and for low-count artefact Tl>MIBI>Tf ( P<0.001). For H/S, Tl>MIBI=Tf, for H/L Tl>MIBI=Tf, and for H/lung Tl<MIBI=Tf. Stress defects in the patients with reversible or mixed perfusion defects were more severe for Tl than for the other tracers (mean summed score out of 68: Tl 52.3, MIBI 55.7, Tf 54.4, P<0.01), but mean rest scores were more similar (Tl 58.7, MIBI 60.7, Tf 59.4, P=0.02). In the subset of 137 patients undergoing diagnostic perfusion studies without prior infarction, angiography or revascularisation, overall sensitivity for the detection of coronary disease defined by subsequent angiography was 91% with a specificity of 87%. There were no significant differences between the tracers with regard to sensitivity and specificity.

IN CONCLUSION

There are technical differences between the tracers. Overall image quality score is superior using technetium, with less low-count artefact and less attenuation. Stress defect depth and extent are slightly greater using thallium, with no difference between MIBI and tetrofosmin. All three tracers perform well in clinical terms, with high sensitivity and specificity for angiographic stenosis and no differences in accuracy between the tracers.

Detection of defects in myocardial perfusion imaging in patients with early breast cancer treated with radiotherapy

BACKGROUND AND PURPOSE

To evaluate radiation-induced defects in myocardial perfusion imaging in early breast cancer patients treated with modern technique radiotherapy.

PATIENTS AND METHODS

Twenty-four patients with left-breast tumours and 12 control patients with right-breast tumours, relapse-free since treatment for primary disease, who had undergone radiotherapy at least 5 years previously and with no history of ischaemic heart disease prior to radiotherapy underwent study. In left-breast patients, at least 1 cm of heart was required to have been in the treatment field. Patients underwent cardiac assessment and single photon emission computerized tomography myocardial perfusion imaging.

RESULTS

Myocardial perfusion tracer uptake was abnormal in 17 (70.8%) left-breast and two (16.7%) right-breast patients (P = 0.002). Of the 17 abnormal scans in left-breast patients, abnormalities were confined to the cardiac apex in 16 patients, and perfusion defects were reversible (n = 7), fixed (n = 7) or mixed (n = 3). Reversible perfusion defects that were not confined to the cardiac apex were observed in two right-breast patients. Left ventricular ejection fraction was normal in all 33 patients in whom it was measured, and no myocardial perfusion abnormalities were judged to require treatment or follow-up.

CONCLUSIONS

In this selected study population modern technique radiotherapy to the left breast was associated with a significantly greater number of myocardial perfusion abnormalities than radiotherapy to the right breast. These abnormalities were both reversible and irreversible, suggesting that radiotherapy can lead to both myocardial damage and to epicardial coronary disease. With a minimum of 5 years follow-up since treatment, no abnormalities were considered to be clinically significant.