Procedure guidelines for radionuclide myocardial perfusion imaging

Predicting long-term time to cardiovascular incidents using myocardial perfusion imaging and deep convolutional neural networks

Myocardial perfusion imaging (MPI) is a clinical tool which can assess the heart's perfusion status, thereby revealing impairments in patients' cardiac function. Within the MPI modality, the acquired three-dimensional signals are typically represented as a sequence of two-dimensional grayscale tomographic images. Here, we proposed an end-to-end survival training approach for processing gray-scale MPI tomograms to generate a risk score which reflects subsequent time to cardiovascular incidents, including cardiovascular death, non-fatal myocardial infarction, and non-fatal ischemic stroke (collectively known as Major Adverse Cardiovascular Events; MACE) as well as Congestive Heart Failure (CHF). We recruited a total of 1928 patients who had undergone MPI followed by coronary interventions. Among them, 80% (n = 1540) were randomly reserved for the training and 5- fold cross-validation stage, while 20% (n = 388) were set aside for the testing stage. The end-to-end survival training can converge well in generating effective AI models via the fivefold cross-validation approach with 1540 patients. When a candidate model is evaluated using independent images, the model can stratify patients into below-median-risk (n = 194) and above-median-risk (n = 194) groups, the corresponding survival curves of the two groups have significant difference (P < 0.0001). We further stratify the above-median-risk group to the quartile 3 and 4 group (n = 97 each), and the three patient strata, referred to as the high, intermediate and low risk groups respectively, manifest statistically significant difference. Notably, the 5-year cardiovascular incident rate is less than 5% in the low-risk group (accounting for 50% of all patients), while the rate is nearly 40% in the high-risk group (accounting for 25% of all patients). Evaluation of patient subgroups revealed stronger effect size in patients with three blocked arteries (Hazard ratio [HR]: 18.377, 95% CI 3.719-90.801, p < 0.001), followed by those with two blocked vessels at HR 7.484 (95% CI 1.858-30.150; p = 0.005). Regarding stent placement, patients with a single stent displayed a HR of 4.410 (95% CI 1.399-13.904; p = 0.011). Patients with two stents show a HR of 10.699 (95% CI 2.262-50.601; p = 0.003), escalating notably to a HR of 57.446 (95% CI 1.922-1717.207; p = 0.019) for patients with three or more stents, indicating a substantial relationship between the disease severity and the predictive capability of the AI for subsequent cardiovascular inciidents. The success of the MPI AI model in stratifying patients into subgroups with distinct time-to-cardiovascular incidents demonstrated the feasibility of proposed end-to-end survival training approach.

By discontinuing beta-blockers before an exercise test we may precipitate a rebound phenomenon

BACKGROUND

There is a need to analyse the current approach to beta-blocker (BB) use in relation to exercise-based stress tests.

OBJECTIVE

We compared various guidelines regarding recommending abrupt vs gradual discontinuation of BB prior to exercise tests. We also analyse the shortcomings of the currently recommended approach and suggest a new approach to avoid BB rebound.

METHODS

A narrative review is used to analyse this topic due to lack of valid randomized clinical trials.

RESULTS

Omitting the BB therapy prior to exercise-based test has been recommended in guidelines for many years. Although reasonable, this approach has potential disadvantages since sudden BB withdrawal may induce a rebound phenomenon, which is, also, acknowledged in several guidelines.

CONCLUSIONS

We observed inconsistency among relevant guidelines; there is no homogenous approach regarding BB use before exercise tests. Most guidelines recommend BB withdrawal for a couple of days before the test; they do not advise BB dose tapering. This approach is not standardised and raises the risk of BB rebound phenomenon both before and during the test. Therefore, we suggest using the half the prescribed BB dose at the usual time of administration (in the morning, prior to the exercise test).

Variation of Contrast Values for Myocardial Perfusion Imaging in Single-photon Emission Computed Tomography/Computed Tomography Hybrid Systems with Different Correction Methods

Objectives:

Single-photon emission computed tomography/computed tomography (SPECT/CT) hybrid systems have the advantage of performing various scans using the same imaging setting. Absorption and scattering of the gamma rays by the patient’s body significantly affect images obtained from scintigraphy, especially in myocardial perfusion imaging. An important parameter for image quality in SPECT is image contrast which is defined as the difference in density between regions of the image corresponding to different levels of radioactive uptake in the patient. The objective of the study was to evaluate the influence of applying different correction methods on image contrast of myocardial SPECT/CT images.

Material and Methods:

A total of 114 patients, 43 females and 71 males, patient’s raw data were processed and analyzed using attenuation correction (AC), scatter correction (SC), both attenuation and scatter correction together (ACSC), and no correction (NC). The short axis (coronal) slices resulted from the raw data reconstruction were chosen to perform the processing for hot and cold spheres for contrast values measurement. Statistical analysis was made for the measured contrast values for AC, SC, ACSC, and NC to determine the best image contrast.

Results:

When applying SC alone, it yields better contrast value (0.834), compared to AC (0.677) and ACSC (0.739). Both ACSC and AC had better image contrast compared to NC (0.592).

Conclusion:

The intercomparison study between the correction conditions indicates that the counts in SPECT/ CT are highly affected by all correction methods. The image contrast has been significantly improved by using SC, AC, and ACSC when compared with the NC image. Furthermore, SC is superior in the image contrast than the other correction conditions in the reconstruction of SPECT/CT MPI.

Health Locus of Control Is Associated With Physical Activity and Other Health Behaviors in Cardiac Patients

PURPOSE

Physical inactivity, smoking, and excessive alcohol use are well-recognized modifiable risk factors for cardiovascular disease (CVD), yet uptake of strategies to mitigate these poor health behaviors varies widely among patients with cardiovascular disease. Part of this variation may be explained by health locus of control (HLOC), defined as the extent to which individuals believe their health is a consequence of their own actions, chance, or the influence of others (eg, physicians).

METHODS

A total of 599 cardiac outpatients (30% female, 61.4 ± 9.4 y of age) completed the Multidimensional Health Locus of Control questionnaire and a structured health behavior questionnaire assessing physical activity, smoking, and alcohol use, at baseline and a 4-y follow-up. Relationships between health behaviors and HLOC were assessed cross-sectionally and longitudinally using general linear models and logistic regression models adjusting for medical and sociodemographic factors.

RESULTS

Higher Internal HLOC was found to be associated with higher levels of leisure time physical activity (LTPA) (β = .21, P = .0008), while lower Internal HLOC was associated with decreasing levels of alcohol consumption over time (β = .26, P = .03). Increasing Chance HLOC was related to lower levels of leisure time physical activity (β = -.15, P = .047) and increased likelihood of being a smoker (β = .10, P = .01), and increasing physician HLOC was associated with decreased likelihood of being a smoker (β = -.17, P = .01).

CONCLUSIONS

Associations between HLOC and multiple health behaviors were observed in a large sample of cardiac outpatients. Results suggest that assessing and targeting HLOC beliefs of cardiac patients may be clinically relevant for behavior change in settings, such as in rehabilitation programs where behavior change is a goal.

Detecting Myocardial Ischemia With 99mTechnetium-Tetrofosmin Myocardial Perfusion Imaging in Ischemic Stroke

BACKGROUND

To assess the myocardial status in patients with stroke, employing myocardial perfusion imaging (MPI) with ^99mTechnetium-tetrofosmin (^99mTc-TF)-single-photon emission computed tomography (SPECT).

METHODS

Fifty-two patients with ischemic stroke were subjected to ^99mTc-TF-SPECT MPI within 1 month after stroke occurrence. None of the patients had any history or symptoms of coronary artery disease or other heart disease. Myocardial perfusion imaging was evaluated visually using a 17-segment polar map. Myocardial ischemia (MIS) was defined as present when the summed stress score (SSS) was >4; MIS was defined as mild when SSS was 4 to 8, and moderate/severe with SSS ≥9. Patients with SSS >4 were compared to patients with SSS <4. Parameters such as age, body mass index, waist perimeter, smoking habits, and medical history (diabetes mellitus, dyslipidemia, etc) were evaluated according to MPI results.

RESULTS

Myocardial ischemia was present in 32 (62%) of 52 patients with stroke. Among them, 20 (62%) of 32 patients had mild abnormalities and 12 (38%) of 32 had moderate/severe. The age and waist perimeter showed a tendency to relate to severe MIS when patients with SSS >9 were compared to patients with SSS <4. In MPI-positive patients, an age was to be association with SSS, with the oldest age exhibiting the highest SSS (P = .01). The association of age with SSS remained statistically significant in the multivariate analysis (P = .04).

CONCLUSION

The study suggested that more than half of patients with stroke without a history of cardiac disease have MIS. Although most of them have mild MIS, we suggest a thorough cardiological evaluation in this group of patients for future prevention of severe myocardial outcome.

Do Women With Anxiety or Depression Have Higher Rates of Myocardial Ischemia During Exercise Testing Than Men?

BACKGROUND

Women diagnosed with coronary artery disease (CAD) typically experience worse outcomes relative to men, possibly through diagnosis and treatment delays. Reasons for these delays may be influenced by mood and anxiety disorders, which are more prevalent in women and have symptoms (eg, palpitations and fatigue) that may be confounded with CAD. Our study examined sex differences in the association between mood and anxiety disorders and myocardial ischemia in patients with and without a CAD history presenting for exercise stress tests.

METHODS AND RESULTS

A total of 2342 patients (women n=760) completed a single photon emission computed tomographic exercise stress test (standard Bruce Protocol) and underwent a psychiatric interview (The Primary Care Evaluation of Mental Disorders) to assess mood and anxiety disorders. Ischemia was assessed using single photon emission computed tomography, with odds ratio used to calculate the effect of sex and mood/anxiety on the presence of ischemia during stress testing by CAD history in a stratified analyses, adjusted for relevant covariates. There was a sex by anxiety interaction with ischemia in those without a CAD history (P=0.015): women with anxiety were more likely to exhibit ischemia during exercise than women without anxiety (odds ratio, 1.75; 95% confidence interval, 1.05-2.89). No significant effects were observed for men nor mood.

CONCLUSIONS

Women with anxiety and no CAD history had higher rates of ischemia than women without anxiety. Results suggest that anxiety symptoms, many of which overlap with those of CAD, might mask CAD symptoms among women (but not men) and contribute to referral and diagnostic delays. Further research is needed to confirm this hypothesis.

The role of pharmacological stress testing in women

Pharmacological stress is an alternative method to dynamic exercise that combined with noninvasive imaging allows the detection of flow-limiting coronary artery disease (CAD). It represents the stress procedure of choice in patients who cannot exercise appropriately. In women, pharmacological stress combined with myocardial perfusion scintigraphy (MPS) has demonstrated to be highly accurate for the detection of obstructive CAD and a valuable tool that helps separate patients at low cardiac risk from those with an adverse prognosis. Pharmacological stress with positron emission tomographic (PET) imaging is increasingly used in the investigation of suspected obstructive CAD; available evidence shows that the diagnostic profile and prognostic value of stress PET imaging is similar to that of stress MPS in women.

Relative associations between depression and anxiety on adverse cardiovascular events: does a history of coronary artery disease matter? A prospective observational study

OBJECTIVES

To assess whether depression and anxiety increase the risk of mortality and major adverse cardiovascular events (MACE), among patients with and without coronary artery disease (CAD).

DESIGN AND SETTING, AND PATIENTS

DECADE (Depression Effects on Coronary Artery Disease Events) is a prospective observational study of 2390 patients referred at the Montreal Heart Institute. Patients were followed for 8.8 years, between 1998 and 2009. Depression and anxiety were assessed using a psychiatric interview (Primary Care Evaluation of Mental Disorders, PRIME-MD). Outcomes data were obtained from Quebec provincial databases.

MAIN OUTCOME MEASURES

All-cause mortality and MACE.

RESULTS

After adjustment for covariates, patients with depression were at increased risks of all-cause mortality (relative risk (RR)=2.84; 95% CI 1.25 to 6.49) compared with patients without depression. Anxiety was not associated with increased mortality risks (RR=0.86; 95% CI 0.31 to 2.36). When patients were stratified according to CAD status, depression increased the risk of mortality among patients with no CAD (RR=4.39; 95% CI 1.12 to 17.21), but not among patients with CAD (RR=2.32; 95% CI 0.78 to 6.88). Neither depression nor anxiety was associated with MACE among patients with or without CAD.

CONCLUSIONS AND RELEVANCE

Depression, but not anxiety, was an independent risk factor for all-cause mortality in patients without CAD. The present study contributes to a better understanding of the relative and unique role of depression versus anxiety among patients with versus without CAD.

Comparison of clinical efficacy and cost of a cardiac imaging strategy versus a traditional exercise test strategy for the investigation of patients with suspected stable coronary artery disease

We evaluated the clinical efficacy and cost of a cardiac imaging strategy versus a traditional exercise tolerance test (ETT) strategy for the investigation of suspected stable coronary artery disease (CAD). We retrospectively collected data of consecutive patients seen in rapid access chest pain clinics at 2 UK hospitals for a period of 12 months. Hospital A investigated patients by performing ETT. Hospital B investigated patients using cardiac imaging test; 483 patients from hospital A and 295 from hospital B were included. In hospital A, 209 patients (43.3%) had contraindication to ETT. Of those who had ETT, 151 (55.1%) had negative ETT, 68 (24.8%) had equivocal ETT, and 55 (20.1%) had positive ETT, of which 53 (96.4%) had invasive coronary angiography (ICA), and of these 23 (43.4%) had obstructive CAD. In hospital B, 26 patients (8.8%) with low pretest probability had calcium score and 3 (11.5%) were positive leading to computed tomography coronary angiography; 98 patients (33.2%) with intermediate pretest probability had computed tomography coronary angiography and 5 (5.1%) were positive; 77 patients (26.1%) had stress echocardiogram and 6 (7.8%) were positive; and 57 patients (19.3%) had myocardial perfusion scintigraphy and 11 (19.3%) were positive. Hospital A performed 127 ICA (26.3% of population) and 52 (40.9%) had obstructive CAD. Hospital B performed 63 ICA (21.4% of population) and 32 (50.8%) had obstructive CAD. The average cost per patient in hospital A was £566.6 ± 490.0 ($875 ± 758) and in hospital B was £487.9 ± 469.6 ($750 ± 725) (p <0.001). In conclusion, our results suggest that a cardiac imaging pathway leads to fewer ICA and a higher yield of obstructive CAD at lower cost per patient.

Development of Coronary Vasospasm during Adenosine-Stress Myocardial Perfusion CT Imaging

Adenosine is a short-acting coronary vasodilator, and it is widely used during pharmacological stress myocardial perfusion imaging. It has a well-established safety profile, and most of its side effects are known to be mild and transient. Until now, coronary vasospasm has been rarely reported as a side effect of adenosine during or after adenosine stress test. This study reports a case of coronary vasospasm which was documented on stress myocardial perfusion CT imaging during adenosine stress test.

Reporting nuclear cardiology: a joint position paper by the European Association of Nuclear Medicine (EANM) and the European Association of Cardiovascular Imaging (EACVI)

The report of an imaging procedure is a critical component of an examination, being the final and often the only communication from the interpreting physician to the referring or treating physician. Very limited evidence and few recommendations or guidelines on reporting imaging studies are available; therefore, an European position statement on how to report nuclear cardiology might be useful. The current paper combines the limited existing evidence with expert consensus, previously published recommendations as well as current clinical practices. For all the applications discussed in this paper (myocardial perfusion, viability, innervation, and function as acquired by single photon emission computed tomography and positron emission tomography or hybrid imaging), headings cover laboratory and patient demographics, clinical indication, tracer administration and image acquisition, findings, and conclusion of the report. The statement also discusses recommended terminology in nuclear cardiology, image display, and preliminary reports. It is hoped that this statement may lead to more attention to create well-written and standardized nuclear cardiology reports and eventually lead to improved clinical outcome.

Rationale and design of the Clinical Evaluation of Magnetic Resonance Imaging in Coronary heart disease 2 trial (CE-MARC 2): a prospective, multicenter, randomized trial of diagnostic strategies in suspected coronary heart disease

Background

A number of investigative strategies exist for the diagnosis of coronary heart disease (CHD). Despite the widespread availability of noninvasive imaging, invasive angiography is commonly used early in the diagnostic pathway. Consequently, approximately 60% of angiograms reveal no evidence of obstructive coronary disease. Reducing unnecessary angiography has potential financial savings and avoids exposing the patient to unnecessary risk. There are no large-scale comparative effectiveness trials of the different diagnostic strategies recommended in international guidelines and none that have evaluated the safety and efficacy of cardiovascular magnetic resonance.

Trial Design

CE-MARC 2 is a prospective, multicenter, 3-arm parallel group, randomized controlled trial of patients with suspected CHD (pretest likelihood 10%-90%) requiring further investigation. A total of 1,200 patients will be randomized on a 2:2:1 basis to receive 3.0-T cardiovascular magnetic resonance–guided care, single-photon emission computed tomography–guided care (according to American College of Cardiology/American Heart Association appropriate-use criteria), or National Institute for Health and Care Excellence guidelines–based management. The primary (efficacy) end point is the occurrence of unnecessary angiography as defined by a normal (>0.8) invasive fractional flow reserve. Safety of each strategy will be assessed by 3-year major adverse cardiovascular event rates. Cost-effectiveness and health-related quality-of-life measures will be performed.

Conclusions

The CE-MARC 2 trial will provide comparative efficacy and safety evidence for 3 different strategies of investigating patients with suspected CHD, with the intension of reducing unnecessary invasive angiography rates. Evaluation of these management strategies has the potential to improve patient care, health-related quality of life, and the cost-effectiveness of CHD investigation.

The interaction between anxiety and depressive symptoms on brachial artery reactivity in cardiac patients

The association between anxiety, depression, and endothelial function (EF) was assessed in a sample of 295 cardiac outpatients (n=222 men; mean age=59). Patients were administered the Beck Depression Inventory-II and the State-Trait Anxiety Inventory, trait scale. EF was assessed through forearm hyperemic reactivity, a nuclear medicine variation of the flow-mediated dilatation technique, which calculates the rate of uptake ratio (RUR) between hyperaemic and non-hyperaemic arms. Neither effect of anxiety (F=1.40, p=.24) nor depression (F=2.66, p=.10) was found in a model predicting EF, however there was an interaction (F=4.11, p=.04). Higher anxiety and lower depressive symptoms were associated with superior RUR compared to lower anxiety and lower depressive symptoms. Anxiety had no influence on RUR in those patients with higher depressive symptoms, who generally displayed the lowest levels of RUR, i.e., poor function. It is speculative whether this potential protective role of anxiety may be guided by behavioral or physiological mechanisms.

Ischemic burden by 3-dimensional myocardial perfusion cardiovascular magnetic resonance: comparison with myocardial perfusion scintigraphy

BACKGROUND

The extent and severity of ischemia on myocardial perfusion scintigraphy (MPS) is commonly used to risk-stratify patients with coronary artery disease. Estimation of ischemic burden by cardiovascular magnetic resonance (CMR) with conventional 2-dimensional myocardial perfusion methods is limited by incomplete cardiac coverage. More recently developed 3-dimensional (3D) myocardial perfusion CMR, however, provides whole-heart coverage. The aim of this study was to compare ischemic burden on 3D myocardial perfusion CMR with (99m)Tc-tetrofosmin MPS.

METHODS AND RESULTS

Forty-five patients who had undergone clinically indicated MPS underwent rest and adenosine stress 3D myocardial perfusion and late gadolinium enhancement CMR. Summed stress and rest scores were calculated for MPS and CMR using a 17-segment model and expressed as a percentage of the maximal possible score. Ischemic burden was defined as the difference between stress and rest scores. 3D myocardial perfusion CMR and MPS agreed in 38 of the 45 patients for the detection of any inducible ischemia. The mean ischemic burden for MPS and CMR was similar (7.5±8.9% versus 6.8±9.5%, respectively, P=0.82) with a strong correlation between techniques (rs=0.70, P<0.001). In a subset of 33 patients who underwent clinically indicated invasive coronary angiography, sensitivities and specificities of the 2 techniques to detect angiographic coronary artery disease were similar (McNemar P=0.45).

CONCLUSIONS

3D myocardial perfusion CMR is an alternative to MPS for detecting the presence and rating the severity of ischemia.

A study of myocardial perfusion in patients with panic disorder and low risk coronary artery disease after 35% CO2 challenge

BACKGROUND

We have previously reported that 35% CO2 challenge induced myocardial ischemia in 81% of coronary artery disease (CAD) patients with comorbid panic disorder (PD) and previous positive nuclear exercise stress tests. However, it is yet unclear whether this is the case among CAD patients with PD and normal nuclear exercise stress test results. We hypothesized that a potent mental stressor such as a panic challenge among CAD patients with PD would also induce ischemia in patients with normal exercise stress tests.

METHODS

Forty-one coronary artery disease patients with normal nuclear exercise stress tests (21 patients with PD and 20 without PD) were submitted to a well-established panic challenge test (with 1 vital capacity inhalation of a gas mixture containing 35% CO2 and 65% O2) and injected with Tc-99m-tetrofosmin (Myoview), upon inhalation. Single photon emission computed tomography imaging was used to assess per-panic challenge reversible myocardial ischemia and HR, BP, and a 12 lead ECG was continuously measured during the procedure.

RESULTS

Fifty-eight percent of panic disorder patients (12/21) had a panic attack during the panic challenge vs 15% (3/20) of controls (p=0.005). Only 10% of patients in each group displayed myocardial ischemia per panic challenge.

CONCLUSIONS

These findings suggest that panic attacks among panic disorder patients with lower-risk coronary artery disease may not confer a risk for myocardial ischemia.

Myocardial perfusion scintigraphy: past, present and future

During the last two decades, radionuclide myocardial perfusion scintigraphy (MPS) has become established as the main functional cardiac imaging technique for the assessment of ischaemic heart disease (IHD). Despite a growing number of alternative functional imaging techniques, MPS still remains the most widely used technique, with a wealth of literature supporting its usefulness in assessing IHD and predicting prognosis. The technique itself has evolved, making it more reliable and robust, with additional ventricular functional information that further defines the prognosis in these patients. With the advent of hybrid single photon emission with CT and positron emission tomography with CT cameras together with the development of new camera technology that enables faster images with less radiation and better resolution, MPS will remain an essential part of IHD investigation. There are new promising radiopharmacological developments and applications such as radiolabelled fatty acids and meta-iodobenzylguanidine. These will widen the scope of nuclear medicine imaging to include patients with cardiac failure and acute chest pain presenting to accident and emergency departments. Nuclear medicine cardiac investigations will continue to have an essential role in the diagnosis, stratification and prognosis of patients with cardiac disease, complementing the new developing cardiac modalities such as CT coronary angiography and MRI.

The Relationship between Multiple Health Behaviours and Brachial Artery Reactivity

Background. The effects of smoking, alcohol consumption, obesity, and a sedentary lifestyle on endothelial function (EF) have only been examined separately. The relative contributions of these behaviours on EF have therefore not been compared. Purpose. To compare the relative associations between these four risk factors and brachial artery reactivity in the same sample. Methods. 328 patients referred for single-photon emission computed tomography (SPECT) exercise stress tests completed a nuclear-medicine-based forearm hyperaemic reactivity test. Self-reported exercise behaviour, smoking habits, and alcohol consumption were collected and waist circumference was measured. Results. Adjusting for relevant covariates, logistic regression analyses revealed that waist circumference, abstinence from alcohol, and past smoking significantly predicted poor brachial artery reactivity while physical activity did not. Only waist circumference predicted continuous variations in EF. Conclusions. Central adiposity, alcohol consumption, and smoking habits but not physical activity are each independent predictors of poor brachial artery reactivity in patients with or at high risk for cardiovascular disease.

Myocardial perfusion GSPECT imaging in patients with myocardial bridging

BACKGROUND

The aim of this study was to investigate the incidence, reversibility, and severity of LV perfusion abnormalities in patients with isolated myocardial bridges using a gated myocardial perfusion SPECT study (GSPECT).

METHODS

A retrospective study involved 42 patients without history of myocardial infarction, with isolated myocardial bridges detected in coronary angiography and no substantial evidence of atherosclerotic changes in coronary arteries. In all patients a gated SPECT study was performed at both rest and stress, after intravenous administration of (99m)Tc MIBI. Reconstructed slices were analyzed using a 20-segment model of the left ventricle.

RESULTS

Incidence and severity of stress-induced ischemia were related to degree of artery constriction (P = .002 and .00014, respectively). Perfusion abnormalities were detected only in patients with critical narrowing (≥ 50%) of artery (in 12 out of 28, i.e., 43% of patients). Summed stress scores (SSS) ranged from 4 to 11 (mean 7), indicating slight or moderate defect intensity. Only 1 patient presented with a SSS value of 31 (severe defect). Perfusion defects were stress induced in 70 out of 72 (97%) segments with abnormal perfusion.

CONCLUSION

Perfusion abnormalities were observed in ab. 40% of patients with critical (≥ 50%) narrowing of artery affected by bridging and were mild, stress induced.

Myocardial perfusion imaging with (99 m)Tc-tetrofosmin SPECT in breast cancer patients that received postoperative radiotherapy: a case-control study

Purpose

To evaluate the cardiac toxicity of radiotherapy (RT) in breast cancer (BC) patients employing myocardial perfusion imaging (MPI) with Tc-99 m Tetrofosmin - single photon emission computer tomography (T-SPECT).

Materials and methods

We studied 46 BC female patients (28 patients with left and 18 patients with right BC) treated with postoperative RT compared to a control group of 85 age-matched females. The median time of RT to SPECT was 40 months (6-263).

Results

Abnormalities in the summed stress score (SSS) were found in 54% of left BC patients, 44.4% of right BC patients, and 32.9% of controls. In left BC patients there were significantly more SSS abnormalities compared to controls (4.0 ± 3.5 vs 2.6 ± 2.0, p = 0.05) and possible trend of increased abnormalities of right BC patients (3.7 ± 3.0 vs 2.6 ± 2.0, p = 0.14). Multiple regression analysis showed more abnormalities in the MPI of left BC patients compared to controls (SSS, p = 0.0001); Marginal toxicity was also noted in right BC patients (SSS, p = 0.045). No additional toxicity was found in patients that received adjuvant cardiotoxic chemotherapy. All T-SPECT abnormalities were clinically silent.

Conclusion

The study suggests that radiation therapy to BC patients result in MPI abnormalities but without apparent clinical consequences.

Myocardial perfusion scintigraphy in Europe 2007: a survey of the European Council of Nuclear Cardiology

PURPOSE

This is the second of a series of surveys designed to assess myocardial perfusion scintigraphy (MPS) practice in Europe.

METHODS

Data were collected from 258 centres in 18 countries. The number of MPS studies per million population (pmp) was estimated assuming that the nonresponding centres performed either no studies (lower estimate) or the same number as the responding centres (upper estimate).

RESULTS

The responding centres served 24% of the population of their countries. The total number of noncardiac nuclear medicine studies was between 2,160 and 8,000 studies pmp. The total number of MPS studies was between 529 and 2,293 pmp. The median number of MPS studies per centre was 571 per year with 57% performing fewer than 500 studies per year and 23% of centres performing fewer than 250 studies per year. There was significant variation between countries, with higher numbers of MPS studies (lower limit of estimate above the mid-range of all countries combined) in Austria, Denmark, Hungary, Portugal and Slovenia, and lower numbers (upper limit of estimate below the mid-range of all countries) in Finland, Norway, Spain and Switzerland. The ratio of MPS to coronary angiography to revascularization procedures was 0.9 to 2.2 to 1. Pharmacological stress was used in 57% and technetium-99m-labelled tracers in 88% of studies. ECG gating was performed in 74% of studies and attenuation correction in 22%.

CONCLUSION

MPS utilization in Europe remains low compared with coronary angiography although there has been a 21% increase in the number of studies pmp in centres that reported in both 2005 and 2007. Pharmacological agents continue to be the predominant form of stress. Despite the widespread use of technetium-99m-labelled tracers, ECG gating is not universally performed. As in the 2005 survey, imaging aids such as attenuation and motion correction and prone imaging are not commonly used.

The central role of the nurse in process improvement relating to pharmacologic stress testing

Pharmacologic stress myocardial perfusion imaging is a noninvasive method for evaluating coronary artery disease in patients unable to exercise sufficiently to achieve a heart rate high enough to facilitate satisfactory imaging. The nuclear cardiology nurse is an invaluable member of the laboratory team that performs these tests. In this specialist role, the nurse must have a thorough knowledge of the different pharmacologic stress agents (dipyridamole, adenosine, regadenoson, and dobutamine) that can be used. This should comprise an understanding of their mechanisms of action, contraindications, drug-drug interactions, adverse effects, and administration protocols. By drawing on this knowledge, the nurse is able to verify that the right agent has been selected for each patient based on his/her medical history. The nurse also can help patients follow pretest instructions (such as withholding caffeine and certain medications) by explaining that the measures are necessary for a safe and successful procedure and that violation may result in test cancellation or postponement. On the day of the stress test, the nurse has an important role in safeguarding the patient as well as providing support and reassurance throughout the different stages of the examination. Responsibilities include explaining the entire procedure to the patients, notably, what they will be asked to do, the effect of the stress agent, the timing of each step, the adverse effects that they may experience, how any adverse events will be managed, and the importance of remaining still during imaging. This central role of the nuclear cardiology nurse in overseeing the practical aspects of the pharmacologic stress test has important implications in terms of optimizing the productivity and efficiency of their noninvasive cardiology laboratory and nuclear medicine department.

Effect of caffeine on SPECT myocardial perfusion imaging during regadenoson pharmacologic stress: rationale and design of a prospective, randomized, multicenter study

BACKGROUND

Caffeine attenuates the coronary hyperemic response to adenosine by competitive A₂(A) receptor blockade. This study aims to determine whether oral caffeine administration compromises diagnostic accuracy in patients undergoing vasodilator stress myocardial perfusion imaging (MPI) with regadenoson, a selective adenosine A(2A) agonist.

METHODS

This multicenter, randomized, double-blind, placebo-controlled, parallel-group study includes patients with suspected coronary artery disease who regularly consume caffeine. Each participant undergoes three SPECT MPI studies: a rest study on day 1 (MPI-1); a regadenoson stress study on day 3 (MPI-2), and a regadenoson stress study on day 5 with double-blind administration of oral caffeine 200 or 400 mg or placebo capsules (MPI-3; n = 90 per arm). Only participants with ≥ 1 reversible defect on the second MPI study undergo the subsequent stress MPI test. The primary endpoint is the difference in the number of reversible defects on the two stress tests using a 17-segment model. Pharmacokinetic/pharmacodynamic analyses will evaluate the effect of caffeine on the regadenoson exposure-response relationship. Safety will also be assessed.

CONCLUSION

The results of this study will show whether the consumption of caffeine equivalent to 2-4 cups of coffee prior to an MPI study with regadenoson affects the diagnostic validity of stress testing (ClinicalTrials.gov number, NCT00826280).

Nuclear scan studies in critical care

The field of nuclear cardiology has grown significantly over the past decade. This is a reflection of the value seen by providers in these safe and effective procedures. Nuclear scan studies are noninvasive and versatile in their usefulness. These studies assist in determining the likelihood of future cardiac events, guide approaches to revascularization, and assist in evaluation of the adequacy of revascularization procedures. Critical thinking and decision-making abilities are two key requirements for nurses in the critical care environment. Knowledge and understanding of the nuclear scan studies indicated for patients help nurses advocate for those in their care.

Myocardial perfusion scintigraphy in Europe 2005: a survey of the European Council on Nuclear Cardiology

PURPOSE

We have conducted a survey of myocardial perfusion scintigraphy (MPS) in 2005 in Europe with the intention of initiating a regular series of surveys to track usage of the technique.

METHODS

Information was obtained from 234 centres in 18 counties. The returning centres served 27% of the population of their countries, and estimates of the numbers of MPS per million of population (pmp) were made assuming that the population not reported either performed no studies (lower estimate) or the same number pmp as the reporting centres (upper estimate).

RESULTS

Estimates of MPS for the countries surveyed ranged from a lower limit of 373 pmp to an upper limit of 1,388 pmp. There were marked variations between countries with higher numbers (lower limit of estimate above the mid range of all countries combined) in Austria, Greece, Hungary, The Netherlands, Sweden and Slovenia, and lower numbers (upper limit of estimate below the mid range of all countries) in Finland, Germany and Poland. The ratio of MPS to coronary angiography to revascularisation procedures was 0.6 to 1.5 to 1. The median number of studies per centre was 496, with 32% of centres performing fewer than 250 studies in the year. The median waiting time for routine studies was 21 days and for urgent studies 3.4 days. Fifty-three percent of studies used pharmacological stress, with roughly equal numbers of adenosine and dipyridamole. Eighty-two percent of studies used (99m)Tc-based tracers. Tomographic acquisition was almost universal with 65% of studies being ECG-gated and 20% attenuation-corrected. Eighteen percent of studies were reported from hard copy alone, and 60% of studies were reported without viewing the rotating planar data.

CONCLUSION

We conclude that relatively low numbers of MPS studies are being performed in the surveyed centres, particularly when compared with coronary angiography and revascularisation. The use of (99m)Tc-based tracers is high, but ECG-gated studies are less common. Some reporting practices are not ideal. These data will serve as a valuable baseline for future surveys, which are likely to be more complete.

EANM/ESC guidelines for radionuclide imaging of cardiac function

Radionuclide imaging of cardiac function represents a number of well-validated techniques for accurate determination of right (RV) and left ventricular (LV) ejection fraction (EF) and LV volumes. These first European guidelines give recommendations for how and when to use first-pass and equilibrium radionuclide ventriculography, gated myocardial perfusion scintigraphy, gated PET, and studies with non-imaging devices for the evaluation of cardiac function. The items covered are presented in 11 sections: clinical indications, radiopharmaceuticals and dosimetry, study acquisition, RV EF, LV EF, LV volumes, LV regional function, LV diastolic function, reports and image display and reference values from the literature of RVEF, LVEF and LV volumes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "prevailing or general consensus". The guidelines are designed to assist in the practice of referral to, performance, interpretation and reporting of nuclear cardiology studies for the evaluation of cardiac performance.

Side effect profile and tolerability of adenosine myocardial perfusion scintigraphy in patients with mild asthma or chronic obstructive pulmonary disease

BACKGROUND

Adenosine may cause bronchoconstriction in subjects with asthma or chronic obstructive pulmonary disease (COPD). Recent evidence suggests that this effect may be dependent on the severity of disease. This study investigates the tolerability of adenosine stress in patients with mild asthma or COPD undergoing myocardial perfusion scintigraphy.

METHODS AND RESULTS

In this case-control study patients with known or suspected mild asthma or COPD were pretreated with an inhaled beta(2)-adrenergic agonist and adenosine titrated up to the maximal dose of 140 microg x kg(-1) x min(-1) over a period of 6 minutes. The occurrence of side effects and test tolerability were compared between the airway disease group and 72 control subjects. Of 1261 patients, 124 had known or suspected airway disease; of these, 72 (58%) were suitable for adenosine stress. The proportion of tests completed as per protocol in the asthma/COPD group was similar to that of control subjects (93% vs 100%, P = .06). Dyspnea (n = 38 [53%] in asthma/COPD group vs n = 25 [35%] in control group, P = .03) and chest pain (n = 14 [19%] in asthma/COPD group vs n = 16 [22%] in control group, P = .7) were the most common side effects, and these were mostly mild and well tolerated. Bronchospasm occurred in 5 patients with asthma/COPD but reverted shortly after discontinuation of the adenosine infusion. Aminophylline was not required in any case.

CONCLUSIONS

A stepwise 6-minute adenosine infusion with prophylactic beta(2)-adrenergic agonist is safe and well tolerated in patients with mild asthma or COPD.

Myocardial perfusion imaging with adenosine triphosphate predicts the rate of cardiovascular events

BACKGROUND

Adenosine triphosphate (ATP) has effects similar to adenosine, including a very short half-life, with the advantage of a much lower cost. Our aim was to evaluate whether myocardial single photon emission computed tomography (SPECT) with ATP can predict the rate of hard events.

METHODS AND RESULTS

We studied 299 patients (188 men; mean age, 64 +/- 10 years) with known or suspected coronary disease with thallium 201 SPECT during ATP infusion and at rest. Perfusion defects were divided into the following: absent/mild reversible, moderate/severe reversible, and mixed/fixed. During a maximum follow-up of 87 months (mean, 32.7 +/- 20.3 months), the rate of cardiovascular events was studied. The prognostic value of different variables that can influence survival was calculated with the Cox proportional hazards model. The total number of cardiovascular events was 115 (43 hard events). The annual rate of hard events according to type of perfusion defect was 3.44% (95% confidence interval [CI], 2.12-5.26) for absent/mild reversible, 6.06% (95% CI, 2.23-13.20) for moderate/severe reversible, and 15.12% (95% CI, 8.64-24.55) for mixed/fixed. In the Cox model the variables that significantly predicted hard events were age greater than 55 years (P = .0293), diabetes (P = .0036), and severe perfusion defects (P = .0008).

CONCLUSION

ATP can be used for pharmacologic stress testing. SPECT with ATP has a stronger correlation with the rate of hard events than clinical variables.

EANM/ESC procedural guidelines for myocardial perfusion imaging in nuclear cardiology

The European procedural guidelines for radionuclide imaging of myocardial perfusion and viability are presented in 13 sections covering patient information, radiopharmaceuticals, injected activities and dosimetry, stress tests, imaging protocols and acquisition, quality control and reconstruction methods, gated studies and attenuation-scatter compensation, data analysis, reports and image display, and positron emission tomography. If the specific recommendations given could not be based on evidence from original, scientific studies, we tried to express this state-of-art. The guidelines are designed to assist in the practice of performing, interpreting and reporting myocardial perfusion SPET. The guidelines do not discuss clinical indications, benefits or drawbacks of radionuclide myocardial imaging compared to non-nuclear techniques, nor do they cover cost benefit or cost effectiveness.

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.

Cardiac imaging using nuclear medicine and postitron emission tomography

This article concentrates on specific issues that are of current interest in mainstream nuclear cardiology. These include developments in myocardial perfusion technique, the potential diagnostic benefits of ECG-gating and attenuation correction, nuclear imaging in the diagnosis of hibernating myocardium, and the cost-effectiveness of perfusion imaging in patients with suspected angina.