Update on cardiac imaging: A critical analysis

Imaging is instrumental in diagnosing and directing the management of atherosclerosis. In 1958 the first diagnostic coronary angiography (CA) was performed, and since then further development has led to new methods such as coronary CT angiography (CTA), optical coherence tomography (OCT), positron tomography (PET), and intravascular ultrasound (IVUS). Currently, CA remains powerful for visualizing coronary arteries; however, recent studies show the benefits of using other non-invasive techniques. This review identifies optimum imaging techniques for diagnosing and monitoring plaque stability. This becomes even direr now, given the rapidly rising incidence of atherosclerosis in society today. Many acute coronary events, including acute myocardial infarctions and sudden deaths, are attributable to plaque rupture. Although fatal, these events can be preventable. We discuss the factors affecting plaque integrity, such as increased inflammation, medications like statins, and increased lipid content. Some of these precipitating factors are identifiable through imaging. However, we also highlight significant complications arising in some modalities; in CA this can include ventricular arrhythmia and even death. Extending this, we elucidated from the literature that risk can also vary based on the location of arteries and their plaques. Promisingly, there are less invasive methods being trialled for assessing plaque stability, such as Cardiac Magnetic Resonance Imaging (CMR), which is already in use for other cardiac diseases like cardiomyopathies. Therefore, future research focusing on using imaging modalities in conjunction may be sensible, to bridge between the effectiveness of modalities, at the expense of increased complications, and vice versa.

High Resting Coronary Flow Velocity by Echocardiography Is Associated With Worse Survival in Patients With Chronic Coronary Syndromes

BACKGROUND

Resting coronary flow velocity (CFV) in the mid-distal left anterior descending coronary artery can be easily assessed with transthoracic echocardiography. In this observational study, the authors sought to assess the relationship between resting CFV, CFV reserve (CFVR), and outcome in patients with chronic coronary syndromes.

METHODS AND RESULTS

In a prospective multicenter study design, the authors retrospectively analyzed 7576 patients (age, 66±11 years; 4312 men) with chronic coronary syndromes and left ventricular ejection fraction ≥50% referred for dipyridamole stress echocardiography. Recruitment (years 2003-2021) involved 7 accredited laboratories, with interobserver variability <10% for CFV measurement at study entry. Baseline peak diastolic CFV was obtained by pulsed-wave Doppler in the mid-distal left anterior descending coronary artery. CFVR (abnormal value ≤2.0) was assessed with dipyridamole. All-cause death was the only end point. The mean CFV of the left anterior descending coronary artery was 31±12 cm/s. The mean CFVR was 2.32±0.60. During a median follow-up of 5.9±4.3 years, 1121 (15%) patients died. At multivariable analysis, resting CFV ≥32 cm/s was identified by a receiver operating curve as the best cutoff and was independently associated with mortality (hazard ratio [HR], 1.24 [95% CI, 1.10-1.40]; P<0.0001) together with CFVR ≤2.0 (HR, 1.78 [95% CI, 1.57-2.02]; P<0.0001), age, diabetes, history of coronary surgery, and left ventricular ejection fraction. When both CFV and CFVR were considered, the mortality rate was highest in patients with resting CFV ≥32 cm/s and CFVR ≤2.0 and lowest in patients with resting CFV <32 cm/s and CFVR >2.0.

CONCLUSIONS

High resting CFV is associated with worse survival in patients with chronic coronary syndromes and left ventricular ejection fraction ≥50%. The value is independent and additive to CFVR. The combination of high resting CFV and low CFVR is associated with the worst survival.

Health economic consequences of optimal vs. observed guideline adherence of coronary angiography in patients with suspected obstructive stable coronary artery in Germany: a microsimulation model

AIMS

While the number of patients with stable coronary artery disease (SCAD) is similar across European countries, Germany has the highest per capita volume of coronary angiographies (CA). This study evaluated the health economic consequences of guideline-non-adherent use of CA in patients with SCAD.

METHODS AND RESULTS

As part of the ENLIGHT-KHK trial, a prospective observational study, this microsimulation model compared the number of major adverse cardiac events (MACE) and the costs of real-world use of CA with those of (assumed) complete guideline-adherent use (according to the German National Disease Management Guideline 2019). The model considered non-invasive testing, CA, revascularization, MACE (30 days after CA), and medical costs. Model inputs were obtained from the ENLIGHT-KHK trial (i.e. patients' records, a patient questionnaire, and claims data). Incremental cost-effectiveness ratios were calculated by comparing the differences in costs and MACE avoided from the perspective of the Statutory Health Insurance (SHI). Independent on pre-test probability (PTP) of SCAD, complete guideline adherence for usage of CA would result in a slightly lower rate of MACE (-0.0017) and less cost (€-807) per person compared with real-world guideline adherence. While cost savings were shown for moderate and low PTP (€901 and €502, respectively), for a high PTP, a guideline-adherent process results in slightly higher costs (€78) compared with real-world guideline adherence. Sensitivity analyses confirmed the results.

CONCLUSION

Our analysis indicates that improving guideline adherence in clinical practice by reducing the amount of CAs in patients with SCAD would lead to cost savings for the German SHI.

Artificial intelligence-based full aortic CT angiography imaging with ultra-low-dose contrast medium: a preliminary study

OBJECTIVES

To further reduce the contrast medium (CM) dose of full aortic CT angiography (ACTA) imaging using the augmented cycle-consistent adversarial framework (Au-CycleGAN) algorithm.

METHODS

We prospectively enrolled 150 consecutive patients with suspected aortic disease. All received ACTA scans of ultra-low-dose CM (ULDCM) protocol and low-dose CM (LDCM) protocol. These data were randomly assigned to the training datasets (n = 100) and the validation datasets (n = 50). The ULDCM images were reconstructed by the Au-CycleGAN algorithm. Then, the AI-based ULDCM images were compared with LDCM images in terms of image quality and diagnostic accuracy.

RESULTS

The mean image quality score of each location in the AI-based ULDCM group was higher than that in the ULDCM group but a little lower than that in the LDCM group (all p < 0.05). All AI-based ULDCM images met the diagnostic requirements (score ≥ 3). Except for the image noise, the AI-based ULDCM images had higher attenuation value than the ULDCM and LDCM images as well as higher SNR and CNR in all locations of the aorta analyzed (all p < 0.05). Similar results were also seen in obese patients (BMI > 25, all p < 0.05). Using the findings of LDCM images as the reference, the AI-based ULDCM images showed good diagnostic parameters and no significant differences in any of the analyzed aortic disease diagnoses (all K-values > 0.80, p < 0.05).

CONCLUSIONS

The required dose of CM for full ACTA imaging can be reduced to one-third of the CM dose of the LDCM protocol while maintaining image quality and diagnostic accuracy using the Au-CycleGAN algorithm.

KEY POINTS

• The required dose of contrast medium (CM) for full ACTA imaging can be reduced to one-third of the CM dose of the low-dose contrast medium (LDCM) protocol using the Au-CycleGAN algorithm. • Except for the image noise, the AI-based ultra-low-dose contrast medium (ULDCM) images had better quantitative image quality parameters than the ULDCM and LDCM images. • No significant diagnostic differences were noted between the AI-based ULDCM and LDCM images regarding all the analyzed aortic disease diagnoses.

Coronary Artery Disease Detected by Low Frequency Heart Sounds

OBJECTIVES

Previous studies have observed an increase in low frequency diastolic heart sounds in patients with coronary artery disease (CAD). The aim was to develop and validate a diagnostic, computerized acoustic CAD-score based on heart sounds for the non-invasive detection of CAD.

METHODS

Prospective study enrolling 463 patients referred for elective coronary angiography. Pre-procedure non-invasive recordings of heart sounds were obtained using a novel acoustic sensor. A CAD-score was defined as the power ratio between the 10-90 Hz frequency spectrum and the 90-300 Hz frequency spectrum of the mid-diastolic heart sound. Quantitative coronary angiography analysis was performed by a blinded core laboratory and patients grouped according to the results: obstructive CAD defined by the presence of at least one ≥ 50% stenosis, non-obstructive CAD as patients with a maximal stenosis in the 25-50% interval and non-CAD as no coronary lesions exceeding 25%. We excluded patients with potential confounders or incomplete data (n = 245). To avoid over-fitting the final cohort of 218 patients was randomly divided into to a training group for development (n = 127) and a validation group (n = 91).

RESULTS

In both the training and the validation group the CAD-score was significantly increased in CAD patients compared to non-CAD patients (p < 0.0001). In the validation group the area under the receiver-operating curve was 77% (95% CI 63-91%). Sensitivity was 71% (95% CI 59-82%) and specificity 64% (95% CI 45-83%).

CONCLUSION

The acoustic CAD-score is a new, inexpensive, non-invasive method to detect CAD, which may supplement clinical risk stratification and reduce the need for subsequent non-invasive and invasive testing.

Cardiac functional imaging

During the last 20 years, cardiac imaging has drastically evolved. Positron emission tomography (PET), fast three-dimensional (3D) imaging with the latest generations of echocardiography & multi-detector computed tomography (CT), stress perfusion assessed by magnetic resonance imaging (MRI), blood flow analysis using four-dimensional (4D) flow MRI, all these techniques offer new trends for optimal noninvasive functional cardiac imaging. Dynamic functional imaging is obtained by acquiring images of the heart at different phases of the cardiac cycle, allowing assessment of cardiac motion, function, and perfusion. Between CT and Cardiac MRI (CMR), CMR has the best temporal resolution, which is suitable for functional imaging while cardiac CT provides higher spatial resolution with isotropic data that have an identical resolution in the three dimensions of the space. The latest generations of CT scanners enable whole heart assessment in one beat, offering also an acceptable temporal resolution with the possibility to display the images in a dynamic mode. Another rapidly growing technique using functional and molecular imaging for the assessment of biological and metabolic pathways is the PET using radio-labeled tracers. Meanwhile, the oldest cardiac imaging tool with doppler ultrasound technology has never stopped evolving. Echocardiography today performs 3D imaging, stress perfusion, and myocardial strain assessment, with high temporal resolution. It still is the first line and more accessible exam for the patient. These different modalities are complementary and may be even combined into PET-CT or PET-MRI. The ability to combine the functional/molecular data with anatomical images may implement a new dimension to our diagnostic tools.

Recommendations for cardiovascular magnetic resonance and computed tomography in congenital heart disease: a consensus paper from the CMR/CCT working group of the Italian Society of Pediatric Cardiology (SICP) and the Italian College of Cardiac Radiology endorsed by the Italian Society of Medical and Interventional Radiology (SIRM) Part I

Cardiovascular magnetic resonance (CMR) and computed tomography (CCT) are advanced imaging modalities that recently revolutionized the conventional diagnostic approach to congenital heart diseases (CHD), supporting echocardiography and often replacing cardiac catheterization. Nevertheless, correct execution and interpretation require in-depth knowledge of all technical and clinical aspects of CHD, a careful assessment of risks and benefits before each exam, proper imaging protocols to maximize diagnostic information, minimizing harm. This position paper, written by experts from the Working Group of the Italian Society of Pediatric Cardiology and from the Italian College of Cardiac Radiology of the Italian Society of Medical and Interventional Radiology, is intended as a practical guide for applying CCT and CMR in children and adults with CHD, wishing to support Radiologists, Pediatricians, Cardiologists and Cardiac Surgeons in the multimodality diagnostic approach to these patients. The first part provides a review of the most relevant literature in the field, describes each modality's advantage and drawback, making considerations on the main applications, image quality, and safety issues. The second part focuses on clinical indications and appropriateness criteria for CMR and CCT, considering the level of CHD complexity, the clinical and logistic setting and the operator expertise.

Cardiovascular/Stroke Risk Assessment in Patients with Erectile Dysfunction-A Role of Carotid Wall Arterial Imaging and Plaque Tissue Characterization Using Artificial Intelligence Paradigm: A Narrative Review

PURPOSE

The role of erectile dysfunction (ED) has recently shown an association with the risk of stroke and coronary heart disease (CHD) via the atherosclerotic pathway. Cardiovascular disease (CVD)/stroke risk has been widely understood with the help of carotid artery disease (CTAD), a surrogate biomarker for CHD. The proposed study emphasizes artificial intelligence-based frameworks such as machine learning (ML) and deep learning (DL) that can accurately predict the severity of CVD/stroke risk using carotid wall arterial imaging in ED patients.

METHODS

Using the PRISMA model, 231 of the best studies were selected. The proposed study mainly consists of two components: (i) the pathophysiology of ED and its link with coronary artery disease (COAD) and CHD in the ED framework and (ii) the ultrasonic-image morphological changes in the carotid arterial walls by quantifying the wall parameters and the characterization of the wall tissue by adapting the ML/DL-based methods, both for the prediction of the severity of CVD risk. The proposed study analyzes the hypothesis that ML/DL can lead to an accurate and early diagnosis of the CVD/stroke risk in ED patients. Our finding suggests that the routine ED patient practice can be amended for ML/DL-based CVD/stroke risk assessment using carotid wall arterial imaging leading to fast, reliable, and accurate CVD/stroke risk stratification.

SUMMARY

We conclude that ML and DL methods are very powerful tools for the characterization of CVD/stroke in patients with varying ED conditions. We anticipate a rapid growth of these tools for early and better CVD/stroke risk management in ED patients.

[Clinical use of Cardiac Nuclear Medicine in Germany]

Cardiac nuclear medicine comprises various diagnostic techniques using radiopharmaceuticals for functional imaging in vivo. This article provides an overview of current clinical use of cardiac imaging in nuclear medicine in Germany: Myocardial perfusion imaging using SPECT is a well-established noninvasive tool to semi-quantitatively measure left ventricular myocardial perfusion. Ischemia and chronic myocardial scars can be idenified with a high diagnostic accuracy. Gated SPECT enables measuring left ventricular function. With new dedicated solid-state camera systems examinations have become faster and better while radiation exposure has been minimized. These new camera systems allow quantitative calculations of myocardial blood flow, which will further improve diagnostic accuracy.For patients with severe chronic coronary artery disease and myocardial dysfunction analyzing myocardial viability is crucial for guiding therpeutic decisions. For detection of hibernating myocardium and its differentiation from scar tissue, two nuclear cardiac methods are combined: Rest myocardial perfusion imaging detects perfusion defects and cardiac 18F-FDG-PET/CT detects glucose metabolism in the hypoperfused area. As long as glucose metabolism is intact therapeutic interventions can be beneficial.In general 18F-FDG-PET/CT allows visualization and quantification of celluar glucose metabolism in oncologic and inflammatory processes. For analysis of cardiac inflammation (e. g. endocarditis or sarcoidosis) a no-carb and high-protein diet is needed at leat 24 hours prior to imaging in order to suppress the physiologic myocardial glucose metabolism. Then, specific inflammatory tracer uptake can be assessed.Cardiac amyloidosis is a rare but dangerous condition. With a specific amyloidosis scintigraphy (bone scintigraphy), cardiac ATTR-amyloidosis can be diagnosed with high accuracy. A potenitally harmful myocardial biopsy often is not needed any more and specific therapy can be initiated.In summary, diagnostic methods in cardiac nuclear medicine non-invasively allow visualization and function analysis of biological processes and are essential for diagnosis finding and therapy guidance. The continuous advancement of diagnostic tools makes nuclear cardiology a highly relevant and interesting field.

Assessment of fluid unresponsiveness guided by lung ultrasound in abdominal surgery: a prospective cohort study

A fluid challenge can generate an infraclinical interstitial syndrome that may be detected by the appearance of B-lines by lung ultrasound. Our objective was to evaluate the appearance of B-lines as a diagnostic marker of preload unresponsiveness and postoperative complications in the operating theater. We conducted a prospective, bicentric, observational study. Adult patients undergoing abdominal surgery were included. Stroke volume (SV) was determined before and after a fluid challenge with 250 mL crystalloids (Delta-SV) using esophageal Doppler monitoring. Responders were defined by an increase of Delta-SV > 10% after fluid challenge. B-lines were collected at four bilateral predefined zones (right and left anterior and lateral). Delta-B-line was defined as the number of newly appearing B-lines after a fluid challenge. Postoperative pulmonary complications were prospectively recorded according to European guidelines. In total, 197 patients were analyzed. After a first fluid challenge, 67% of patients were responders and 33% were non-responders. Delta-B-line was significantly higher in non-responders than responders [4 (2–7) vs 1 (0–3), p < 0.0001]. Delta-B-line was able to diagnose fluid non-responders with an area under the curve of 0.74 (95% CI 0.67–0.80, p < 0.0001). The best threshold was two B-lines with a sensitivity of 80% and a specificity of 57%. The final Delta-B-line could predict postoperative pulmonary complications with an area under the curve of 0.74 (95% CI 0.67–0.80, p = 0.0004). Delta-B-line of two or more detected in four lung ultrasound zones can be considered to be a marker of preload unresponsiveness after a fluid challenge in abdominal surgery.

The objectives and procedures of the study were registered at Clinicaltrials.gov (NCT03502460; Principal investigator: Stéphane BAR, date of registration: April 18, 2018).

Non-invasive Imaging in Coronary Syndromes - Recommendations of the European Association of Cardiovascular Imaging and the American Society of Echocardiography, in Collaboration with the American Society of Nuclear Cardiology, Society of Cardiovascular Computed Tomography and Society for Cardiovascular Magnetic Resonance

Coronary artery disease (CAD) is one of the major causes of mortality and morbidity worldwide, with a high socioeconomic impact.(1) Non-invasive imaging modalities play a fundamental role in the evaluation and management of patients with known or suspected CAD. Imaging end-points have served as surrogate markers in many observational studies and randomized clinical trials that evaluated the benefits of specific therapies for CAD.(2) A number of guidelines and recommendations have been published about coronary syndromes by cardiology societies and associations, but have not focused on the excellent opportunities with cardiac imaging. The recent European Society of Cardiology (ESC) 2019 guideline on chronic coronary syndromes (CCS) and 2020 guideline on acute coronary syndromes in patients presenting with non-ST-segment elevation (NSTE-ACS) highlight the importance of non-invasive imaging in the diagnosis, treatment, and risk assessment of the disease.(3)(4) The purpose of the current recommendations is to present the significant role of non-invasive imaging in coronary syndromes in more detail. These recommendations have been developed by the European Association of Cardiovascular Imaging (EACVI) and the American Society of Echocardiography (ASE), in collaboration with the American Society of Nuclear Cardiology, the Society of Cardiovascular Computed Tomography, and the Society for Cardiovascular Magnetic Resonance, all of which have approved the final document.

The ethical dilemma of emergency department patients with low-risk chest pain

Millions of patients present to US EDs each year with symptoms concerning for acute coronary syndrome (ACS), but fewer than 10% are ultimately diagnosed with ACS. Well-tested and externally validated accelerated diagnostic protocols were developed to aid providers in risk stratifying patients with possible ACS and have become central components of current ED practice guidelines. Nevertheless, the fear of missing ACS continues to be a strong motivator for ED providers to pursue further testing for their patients. An ethical dilemma arises when the provider must balance the risk of ACS if the patient is discharged compared with the potential harms caused by a cardiac workup. Providers should be familiar with the ethical principles relevant to this dilemma in order to determine what is in the best interests of the patient.

Mitral annular calcification and valvular dysfunction: multimodality imaging evaluation, grading, and management

Mitral annular calcification (MAC) refers to calcium deposition in the fibrous skeleton of the mitral valve. It has many cardiovascular associations, including mitral valve dysfunction, elevated cardiovascular risk, arrhythmias, and endocarditis. Echocardiography conventionally is the first-line imaging modality for anatomic assessment, and evaluation of mitral valve function. Cardiac computed tomography (CT) has demonstrated importance as an imaging modality for the evaluation and planning of related procedures. It also holds promise in quantitative grading of MAC. Currently, there is no universally accepted definition or classification system of MAC severity. We review the multimodality imaging evaluation of MAC and associated valvular dysfunction and propose a novel classification system based on qualitative and quantitative measurements derived from echocardiography and cardiac CT.

Added value of computed tomography fractional flow reserve in the diagnosis of coronary artery disease

Multiple non-invasive tests are performed to diagnose coronary artery disease (CAD), but all are limited to either anatomical or functional assessments. Computed tomography derived Fractional Flow Reserve (CT-FFR) based on patient-specific lumped parameter models is a new test combining both characteristics simulating invasive FFR. This study aims to evaluate the added value of CT-FFR over other non-invasive tests to diagnose CAD. Patients with clinical suspicion of angina pectoris between 2010 and 2011 were included in this cross-sectional study. All underwent stress electrocardiography (X-ECG), SPECT, CT coronary angiography (CCTA) and CT-FFR. Invasive coronary angiography (ICA) and FFR were used as reference standard. Five models mimicking the clinical workflow were fitted and the area under receiver operating characteristic (AUROC) curve was used for comparison. 44% of the patients included in the analysis had a FFR of ≤ 0.80. The basic model including pre-test-likelihood and X-ECG had an AUROC of 0.79. The SPECT-strategy had an AUROC of 0.90 (p = 0.008), CCTA-strategy of 0.88 (p < 0.001), 0.93 when adding CT-FFR (p = 0.40) compared to 0.94 when combining CCTA and SPECT. This study shows adding on-site CT-FFR based on patient-specific lumped parameter models leads to an increased AUROC compared to the basic model. It improves the diagnostic work-up beyond SPECT or CCTA and is non-inferior to the combined strategy of SPECT and CCTA in the diagnosis of hemodynamically relevant CAD.

[Computed tomography or cardiovascular magnetic resonance imaging for diagnosis of chronic coronary syndrome?]

BACKGROUND

Noninvasive imaging modalities are of central importance in the diagnosis of chronic coronary syndrome (CCS) in the current guidelines of the European Society of Cardiology (ESC), while the role of primary invasive coronary angiography in this context is increasingly being questioned. This review provides a summary of the most important diagnostic strategies from the radiology perspective.

METHODOLOGICAL ISSUE

The diagnostic algorithm is guided by the pretest probability (PTP) for the presence of CCS, which can be estimated based on age, sex, and symptoms. It is important to note that PTP in the current guidelines has decreased significantly compared to older recommendations and this change has an impact on the selection of the most appropriate imaging technique.

STANDARD RADIOLOGICAL METHODS

In patients with low PTP (>5% and <15%) and without prediagnosed coronary artery disease (CAD), CCS can be safely ruled out with inconspicuous computed tomography angiogram (CTA) of the coronary vessels. In patients with increased PTP (>15%) or prediagnosed CAD, noninvasive functional imaging should be primarily used to detect ischemia.

PERFORMANCE AND METHODICAL INNOVATIONS

The excellent sensitivity (89%), specificity (87%) and high prognostic relevance make stress perfusion cardiovascular magnetic resonance (CMR) imaging the functional method of first choice. Technical innovations and the use of artificial intelligence-based methods for image analysis could contribute to further improve its accuracy in the future.

PRACTICAL RECOMMENDATIONS

Radiologists should be aware of the recommendations of the current guidelines and work towards the establishment of coronary CTA and stress perfusion CMR in clinical routine.

Relative clinical value of coronary computed tomography and stress echocardiography-guided management of stable chest pain patients: a propensity-matched analysis

AIMS

The European Society of Cardiology recommends coronary computed tomography (CCT) for the assessment of low-risk patients with suspected stable angina. We aimed to assess in a real-life setting the relative clinical value of stress echocardiography (SE)- and CCT-guided management in this population.

METHODS AND RESULTS

Patients with stable chest pain and no prior history of coronary artery disease (CAD) who underwent CCT or SE as the initial investigative strategy were propensity-matched (990 patients each group-age: 59 ± 13.2 years, males: 47.9%) to account for baseline differences in cardiovascular risk factors. Inconclusive tests were 6% vs. 3% (P < 0.005) in CCT vs. SE. Severe (≥70% stenosis) on CCT and inducible ischaemia on SE detected obstructive CAD by invasive coronary angiography in 63% vs. 57% patients (P = 0.33). Over the follow-up period (median 717, interquartile range 93-1069 days) more patients underwent invasive coronary angiography (21.5% vs. 7.3%, P < 0.005), revascularization (7.3% vs. 3.5%, P < 0.005), further functional testing 33.4% vs. 8.7% (P < 0.005), but more patients were prescribed statins 8.8% vs. 3.8% (P < 0.005) in the CCT vs. the SE arm, respectively. Combined all-cause mortality and acute myocardial infarction was low-CCT-2.3% and SE-3.3%-with no significant difference (P = 0.16).

CONCLUSION

Initial SE-guided management was similar for the detection of obstructive CAD, demonstrated better resource utilization, but was associated with reduced prescription of statins although with no difference in medium-term outcome compared to CCT in this very low-risk population. However, a randomized study with longer follow-up is needed to confirm the clinical value of our findings.

Noninvasive Imaging Risk Stratification with Computed Tomography Angiography for Coronary Artery Disease

The recent technological evolution of coronary computed tomography angiography (CTA) with improved sensitivity and high negative predictive value has extended its potential applications as a gatekeeper test before invasive coronary angiography. However, the definition of the most accurate diagnostic algorithms comprising CTA as a first-line strategy for ruling out coronary artery disease and the correct management of the patients according to the results of imaging tests still warrant better definition.

ESC 2019 guidelines for the diagnosis and management of chronic coronary syndromes : Recommendations for cardiovascular imaging

The European Society of Cardiology (ESC) has recently published new guidelines on the diagnosis and management of chronic coronary syndromes (CCS). Due to variable symptoms, objective tests are often necessary to confirm the diagnosis, exclude alternative diagnoses, and assess the severity of underlying disease. This review provides a summary of the main diagnostic strategies listed in the guidelines for evaluation of patients suspected of having obstructive coronary artery disease (CAD). Based on data from contemporary cohorts of patients referred for diagnostic testing, the pre-test probabilities of obstructive CAD based on age, sex, and symptoms have been adjusted substantially downward compared with the previous guidelines. Further, a new concept of “clinical likelihood of CAD” was introduced accounting for the impact of various risk factors and modifiers on the pre-test probability. Noninvasive functional imaging for myocardial ischemia, coronary computed tomography angiography, or invasive coronary angiography combined with functional evaluation is recommended as the initial strategy to diagnose CAD in symptomatic patients, unless obstructive CAD can be excluded by clinical assessment alone. When available, imaging tests are recommended as noninvasive modalities instead of exercise electrocardiograms.

Cardiac PET/MRI: Current Clinical Status and Future Perspectives

Combined PET/MRI has now been in clinical routine for almost 10 years. Since then, it has not only had to face validation, comparison and research questions, it has also been increasingly used in clinical routine. A number of cardiovascular applications have become established here, whereby viability imaging and assessment of inflammatory and infiltrative processes in the heart are to be emphasized. However, further interesting applications are expected in the near future. This review summarizes the most important clinical applications on the one hand and mentions interesting areas of application in research on the other.

Imaging in ESC clinical guidelines: chronic coronary syndromes

The European Society of Cardiology (ESC) has recently published new guidelines on the diagnosis and management of chronic coronary syndromes (CCS). The 2019 guideline identified six common clinical scenarios of CCS defined by the different evolutionary phases of coronary artery disease (CAD), excluding the situations in which an acute coronary event, often with coronary thrombus formation, dominates the clinical presentation. This review aims at providing a summary of novel or revised concepts in the guidelines together with the recent data underlying the major changes on the use of cardiac imaging in patients with suspected or known CCS.

Based on data from contemporary cohorts of patients referred for diagnostic testing, the pre-test probabilities of CAD based on age, sex and symptoms have been adjusted substantially downward as compared with 2013 ESC guidelines. Further, the impact of various risk factors and modifiers on the pre-test probability was highlighted and a new concept of ‘Clinical likelihood of CAD’ was introduced. Recommendations regarding diagnostic tests to establish or rule-out obstructive CAD have been updated with recent data on their diagnostic performance in different patient groups and impact on patient outcome. As the initial strategy to diagnose CAD in symptomatic patients, non-invasive functional imaging for myocardial ischaemia, coronary computed tomography angiography or invasive coronary angiography combined with functional evaluation may be used, unless obstructive CAD can be excluded by clinical assessment alone. When available, imaging tests instead of the exercise electrocardiogram are recommended when following the non-invasive diagnostic strategy.

Cardiac stress testing review for the primary care provider

Various modes of cardiac stress testing are conducted in outpatient practices today. This article presents information on the current methods of testing to help primary care providers gain confidence in test selection, the testing process, and interpreting results.

Head-to-head comparison of adaptive statistical and model-based iterative reconstruction algorithms for submillisievert coronary CT angiography

Aims

Iterative reconstruction (IR) algorithms allow for a significant reduction in radiation dose of coronary computed tomography angiography (CCTA). We performed a head-to-head comparison of adaptive statistical IR (ASiR) and model-based IR (MBIR) algorithms to assess their impact on quantitative image parameters and diagnostic accuracy for submillisievert CCTA.

Methods and results

CCTA datasets of 91 patients were reconstructed using filtered back projection (FBP), increasing contributions of ASiR (20, 40, 60, 80, and 100%), and MBIR. Signal and noise were measured in the aortic root to calculate signal-to-noise ratio (SNR). In a subgroup of 36 patients, diagnostic accuracy of ASiR 40%, ASiR 100%, and MBIR for diagnosis of coronary artery disease (CAD) was compared with invasive coronary angiography. Median radiation dose was 0.21 mSv for CCTA. While increasing levels of ASiR gradually reduced image noise compared with FBP (up to - 48%, P < 0.001), MBIR provided largest noise reduction (-79% compared with FBP) outperforming ASiR (-59% compared with ASiR 100%; P < 0.001). Increased noise and lower SNR with ASiR 40% and ASiR 100% resulted in substantially lower diagnostic accuracy to detect CAD as diagnosed by invasive coronary angiography compared with MBIR: sensitivity and specificity were 100 and 37%, 100 and 57%, and 100 and 74% for ASiR 40%, ASiR 100%, and MBIR, respectively.

Conclusion

MBIR offers substantial noise reduction with increased SNR, paving the way for implementation of submillisievert CCTA protocols in clinical routine. In contrast, inferior noise reduction by ASiR negatively affects diagnostic accuracy of submillisievert CCTA for CAD detection.

Diagnostic yield and accuracy of coronary CT angiography after abnormal nuclear myocardial perfusion imaging

We aimed to determine the diagnostic yield and accuracy of coronary CT angiography (CCTA) in patients referred for invasive coronary angiography (ICA) based on clinical concern for coronary artery disease (CAD) and an abnormal nuclear stress myocardial perfusion imaging (MPI) study. We enrolled 100 patients (84 male, mean age 59.6 ± 8.9 years) with an abnormal MPI study and subsequent referral for ICA. Each patient underwent CCTA prior to ICA. We analyzed the prevalence of potentially obstructive CAD (≥50% stenosis) on CCTA and calculated the diagnostic accuracy of ≥50% stenosis on CCTA for the detection of clinically significant CAD on ICA (defined as any ≥70% stenosis or ≥50% left main stenosis). On CCTA, 54 patients had at least one ≥50% stenosis. With ICA, 45 patients demonstrated clinically significant CAD. A positive CCTA had 100% sensitivity and 84% specificity with a 100% negative predictive value and 83% positive predictive value for clinically significant CAD on a per patient basis in MPI positive symptomatic patients. In conclusion, almost half (48%) of patients with suspected CAD and an abnormal MPI study demonstrate no obstructive CAD on CCTA.

Impact of age on the selection of nuclear cardiology stress protocols: The INCAPS (IAEA nuclear cardiology protocols) study

BACKGROUND

There is growing concern about radiation exposure from nuclear myocardial perfusion imaging (MPI), particularly among younger patients who are more prone to develop untoward effects of ionizing radiation, and hence US and European professional society guidelines recommend age as a consideration in weighing radiation risk from MPI. We aimed to determine how patient radiation doses from MPI vary across age groups in a large contemporary international cohort.

METHODS

Data were collected as part of a global cross-sectional study of centers performing MPI coordinated by the International Atomic Energy Agency (IAEA). Sites provided information on each MPI study completed during a single week in March-April 2013. We compared across age groups laboratory adherence to pre-specified radiation-related best practices, radiation effective dose (ED; a whole-body measure reflecting the amount of radiation to each organ and its relative sensitivity to radiation's deleterious effects), and the proportion of patients with ED ≤ 9 mSv, a target level specified in guidelines.

RESULTS

Among 7911 patients undergoing MPI in 308 laboratories in 65 countries, mean ED was 10.0 ± 4.5 mSv with slightly higher exposure among younger age groups (trend p value < 0.001). There was no difference in the proportion of patients with ED ≤ 9 mSv across age groups, or in adherence to best practices based on the median age of patients in a laboratory.

CONCLUSIONS

In contemporary nuclear cardiology practice, the age of the patient appears not to impact protocol selection and radiation dose, contrary to professional society guidelines.

DNA double-strand breaks in blood lymphocytes induced by two-day 99mTc-MIBI myocardial perfusion scintigraphy

OBJECTIVES

To investigate DNA double-strand breaks (DSBs) in blood lymphocytes induced by two-day ^99mTc-MIBI myocardial perfusion scintigraphy (MPS) using y-H2AX immunofluorescence microscopy and to correlate the results with ^99mTc activity in blood samples.

METHODS

Eleven patients who underwent two-day MPS were included. DSB blood sampling was performed before and 5min, 1h and 24h after the first and second radiotracer injections. ^99mTc activity was measured in each blood sample. For immunofluorescence microscopy, distinct foci representing DSBs were quantified in lymphocytes after staining for the phosphorylated histone variant y-H2AX.

RESULTS

The ^99mTc-MIBI activity measured on days one and two was similar (254±25 and 258±27 MBq; p=0.594). Compared with baseline DSB foci (0.09±0.05/cell), a significant increase was found at 5min (0.19±0.04/cell) and 1h (0.18±0.04/cell) after the first injection and at 5min and 1h after the second injection (0.21±0.03 and 0.19±0.04/cell, respectively; p=0.003 for both). At 24h after the first and second injections, the number of DSB foci had returned to baseline (0.06±0.02 and 0.12±0.05/cell, respectively). ^99mTc activity levels in peripheral blood samples correlated well with DSB counts (r=0.451).

CONCLUSIONS

DSB counts reflect ^99mTc-MIBI activity after injection for two-day MPS, and might allow individual monitoring of biological effects of cardiac nuclear imaging.

KEY POINTS

• Myocardial perfusion scintigraphy using ^99mTc induces time-dependent double-strand breaks (DSBs) • γ-H2AX immunofluorescence microscopy shows DSB as an early response to radiotracer injection • Activity measurements of ^99mTc correlate well with detected DSB • DSB foci induced by ^99mTc return to baseline 24h after radiotracer injection.

Myokard-Perfusions-SPECT

Die S1-Leitlinie Myokard-Perfusions-SPECT wurde überarbeitet und bei der Arbeitsgemeinschaft der wissenschaftlichen Fachgesellschaften (AWMF) online publiziert. Sie ist in ihrer aktuellen Fassung bis 2/2022 gültig. Dieser Beitrag gibt in gekürzter Form und mit Kommentaren versehen die Kapitel und Unterkapitel wieder, in denen Änderungen und Ergänzungen vorgenommen wurden.

A low-dose and an ultra-low-dose contrast agent protocol for coronary CT angiography in a clinical setting: quantitative and qualitative comparison to a standard dose protocol

OBJECTIVE

To evaluate the impact of a low-dose (LD) and an ultra-LD (ULD) contrast protocol for coronary CT angiography on qualitative and quantitative image parameters in a clinical setting.

METHODS

We scanned 120 consecutive patients with a 256-slice CT scanner applying a LD (60 patients, 35-55 ml) or ULD (60 patients, 25-45 ml) contrast protocol adapted to the body mass index. Visually assessed image quality and attenuation measured in each coronary segment were retrospectively compared in 20 consecutive patients scanned with a normal-dose (ND, 40-105 ml) contrast protocol.

RESULTS

Visually assessed image quality did not differ significantly among protocols. By contrast, attenuation obtained from the ULD protocol (median contrast volume 35 ml) differed significantly from the LD (median 45 ml) and ND (median 70 ml) protocols in the coronary segments (316 ± 52 vs 363 ± 60 and 359 ± 52 HU, p < 0.001). Attenuation did not differ significantly between the LD and ND protocol. The proportion of patients with inadequate coronary vessel attenuation was significantly higher (p < 0.001) in the ULD protocol (37%) than in the ND (5%) and LD (10%) protocols but did not differ significantly between the ND and LD protocols.

CONCLUSION

In a clinical setting, a LD contrast protocol with a median volume of 45 ml is feasible for the latest generation 256-slice coronary CT angiography as it yields attenuation comparable to a ND protocol. By contrast, the implementation of an ULD protocol remains challenging. Advances in knowledge: Although not perceived by the naked eye, an ULD contrast protocol in a clinical setting yields attenuation below a threshold for diagnostic image quality.

Chest pain for coronary heart disease in general practice: clinical judgement and a clinical decision rule

BACKGROUND

The Marburg Heart Score (MHS) is a simple, valid, and robust clinical decision rule assisting GPs in ruling out coronary heart disease (CHD) in patients presenting with chest pain.

AIM

To investigate whether using the rule adds to the GP's clinical judgement.

DESIGN AND SETTING

A comparative diagnostic accuracy study was conducted using data from 832 consecutive patients with chest pain in general practice.

METHOD

Three diagnostic strategies were defined using the MHS: diagnosis based solely on the MHS; using the MHS as a triage test; and GP's clinical judgement aided by the MHS. Their accuracy was compared with the GPs' unaided clinical judgement.

RESULTS

Sensitivity and specificity of the GPs' unaided clinical judgement was 82.9% (95% confidence interval [CI] = 72.4 to 89.9) and 61.0% (95% CI = 56.7 to 65.2), respectively. In comparison, the sensitivity of the MHS was higher (difference 8.5%, 95% CI = -2.4 to 19.6) and the specificity was similar (difference -0.4%, 95% CI = -5.3 to 4.5); the sensitivity of the triage was similar (difference -1.5%, 95% CI = -9.8 to 7.0) and the specificity was higher (difference 11.6%, 95% CI = 7.8 to 15.4); and both the sensitivity and specificity of the aided clinical judgement were higher (difference 8.0%, 95% CI = -6.9 to 23.0 and 5.8%, 95% CI = -1.6 to 13.2, respectively).

CONCLUSION

Using the Marburg Heart Score for initial triage can improve the clinical diagnosis of CHD in general practice.

Elevation of cardiac troponin T in patients with amyotrophic lateral sclerosis

Limited evidence suggests that specificity of cardiac troponin T (cTnT), a highly sensitive biomarker of myocardial injury, is reduced in patients with skeletal myopathies. Whether amyotrophic lateral sclerosis (ALS)-the most common motor neuron disease-could be also associated with abnormal plasma or serum cTnT levels remains unclear. Our objective was to assess cTnT levels in patients with ALS without known cTnT elevating conditions. Among ALS patients seen at our institution until 2012 we identified those who had their cTnT measured. Patients who suffered from conditions known to elevate cTnT were excluded. A case-control analysis comparing cTnT levels of these ALS patients to matched non-ALS controls fulfilling the same inclusion criteria was performed. We included 40 ALS patients of whom 27 (68 %) patients had a positive cTnT. In the control group (n = 40), 2 (5 %) tested as cTnT positive (p < 0.001). Among the ALS patients who underwent cTnT evaluation on more occasions (n = 7; median follow-up = 1.08 years), 2 (29 %) patients tested positive during the initial measurement while 6 (86 %) of them had positive cTnT at the subsequent evaluations. ALS patients with increased cTnT had been diagnosed with ALS significantly earlier than those without the elevation. Our findings raise the possibility that ALS may cause cTnT elevations. Further studies are needed to confirm these findings, clarify the pathophysiological mechanism, and establish the significance of cTnT elevations in patients with ALS.

The Role of Cardiovascular Magnetic Resonance Imaging in Heart Failure

Cardiovascular imaging is key for the assessment of patients with heart failure. Today, cardiovascular magnetic resonance imaging plays an established role in the assessment of patients with suspected and confirmed heart failure syndromes, in particular identifying aetiology. Its role in informing prognosis and guiding decisions around therapy are evolving. Key strengths include its accuracy; reproducibility; unrestricted field of view; lack of radiation; multiple abilities to characterise myocardial tissue, thrombus and scar; as well as unparalleled assessment of left and right ventricular volumes. T2* has an established role in the assessment and follow-up of iron overload cardiomyopathy and a role for T1 in specific therapies for cardiac amyloid and Anderson-Fabry disease is emerging.

The declining frequency of inducible myocardial ischemia during stress echocardiography over 27 consecutive years (1983-2009)

BACKGROUND

Previous studies have suggested a decline in positivity of stress cardiac imaging, suggesting the need for developing better strategies for test selection to achieve acceptable cost-effectiveness balance. The aim of this retrospective study was to assess the rate of positivity of stress echocardiography (SE) over 27 consecutive years.

METHODS

We assessed the rate of SE positivity in 2007 patients without previous myocardial infarction or coronary revascularization who performed SE in a tertiary care referral center from 1983 to 2009. SE was performed with dipyridamole (1427), dobutamine (136) or exercise (444).

RESULTS

There was a progressive decline over time in the rate of SE positivity from 42% (1983-1991) to 22% (2001-2009), with a relative increase of patients with low pre-test probability of disease (from 5% to 27%). The percentage of patients studied with SE under anti-ischemic therapy increased markedly (from 8% in the first to 61% in the last nine years).

CONCLUSION

Over 27 consecutive years, we observed a steady decline in SE positivity rate (with >5-fold increase of low probability patients), with almost 8-fold increase in anti-ischemic therapy at testing. We probably need refined criteria of referral for testing and/or better ways to titrate the negative response beyond wall motion abnormalities during SE.

Minimized Radiation and Contrast Agent Exposure for Coronary Computed Tomography Angiography: First Clinical Experience on a Latest Generation 256-slice Scanner

RATIONALE AND OBJECTIVES

The aim of the study was to evaluate the impact of the latest coronary computed tomography angiography (CCTA) techniques allowing a radiation- and contrast-sparing protocol on image quality in unselected patients referred for exclusion of suspected coronary artery disease (CAD).

MATERIALS AND METHODS

This prospective study was approved by the local ethics committee, and all patients provided written informed consent. Between March and June 2015, 89 consecutive patients (61% male; mean age 55 ± 11 years) referred for exclusion of CAD by 256-slice CCTA using prospective electrocardiogram triggering were included. Tube voltage (80-120 kVp), tube current (180-310 mA) as well contrast agent volume (25-45 mL) and flow rate (3.5-5 mL/s) were adapted to body mass index. Signal intensity was measured by placing a region of interest in the aortic root, the left main artery, and the proximal right coronary artery. Image noise was measured in the aortic root. Two independent blinded readers semi-quantitatively assessed the image quality regarding motion, noise, and contrast on a 4-point scale.

RESULTS

Median contrast agent volume and median effective radiation dose were 35 mL (interquartile range, 30-40 mL) and 0.5 mSv (interquartile range, 0.4-0.6 mSv), respectively. Mean attenuation in the aortic root was 412 ± 89 Hounsfield units. Diagnostic image quality was obtained in 1050 of 1067 (98.4%) coronary segments and, on an intention-to-diagnosis basis, in 85 of 89 (95.5%) patients. Below a cut-off heart rate of 67 beats/min, only 1 of 974 (0.1%) coronary segments was nondiagnostic.

CONCLUSION

A radiation- and contrast-sparing protocol for CCTA on a latest generation 256-slice computed tomography scanner yields diagnostic image quality in patients referred for CAD exclusion in daily clinical routine.

Occult coronary artery disease in middle-aged sportsmen with a low cardiovascular risk score: The Measuring Athlete's Risk of Cardiovascular Events (MARC) study

BACKGROUND

Most exercise-related cardiac arrests in men aged ≥45 years are due to coronary artery disease (CAD). The current sports medical evaluation (SME) of middle-aged sportsmen includes medical history, physical examination and resting and exercise electrocardiography (ECG). We investigated the added value of low-dose cardiac computed tomography (CCT) - both non-contrast CT for coronary artery calcium scoring (CACS) and contrast-enhanced coronary CT angiography (CCTA) - in order to detect occult CAD in asymptomatic recreational sportsmen aged ≥45 years without known cardiovascular disease.

METHODS

Following a normal SME (with resting and bicycle exercise ECG), 318 asymptomatic sportsmen underwent CCT and 300 (94%) had a low European Society of Cardiology Systematic Coronary Risk Evaluation (SCORE) risk. Occult CAD was defined as a CACS ≥100 Agatston units (AU) or obstructive (≥50%) luminal stenosis on CCTA. The number needed to screen (NNS) in order to prevent one cardiovascular event within 5 years with statin treatment was estimated.

RESULTS

Fifty-two (16.4%, 95% confidence interval (CI): 12.7-20.8%) of 318 participants had a CACS ≥100 AU. The CCTA identified an additional eight participants with luminal narrowing ≥50% (and a CACS <100 AU). Taken together, CCT identified CAD in 60 (18.9%, 95% CI: 14.9-23.5%) of 318 participants. The 5-year estimated NNS was 183 (95% CI: 144-236) for CACS and 159 (95% CI: 128-201) for CACS combined with CCTA.

CONCLUSIONS

Coronary CT detects occult CAD in almost one in five asymptomatic sportsmen aged ≥45 years after a normal SME that included resting and bicycle exercise ECG. CACS reveals most of the relevant CAD with limited additional value of contrast-enhanced CCTA. The NNS in order to prevent one cardiovascular event compares favourably to that of other screening tests.

Nuclear cardiology practice and associated radiation doses in Europe: results of the IAEA Nuclear Cardiology Protocols Study (INCAPS) for the 27 European countries

Purpose

Nuclear cardiology is widely used to diagnose coronary artery disease and to guide patient management, but data on current practices, radiation dose-related best practices, and radiation doses are scarce. To address these issues, the IAEA conducted a worldwide study of nuclear cardiology practice. We present the European subanalysis.

Methods

In March 2013, the IAEA invited laboratories across the world to document all SPECT and PET studies performed in one week. The data included age, gender, weight, radiopharmaceuticals, injected activities, camera type, positioning, hardware and software. Radiation effective dose was calculated for each patient. A quality score was defined for each laboratory as the number followed of eight predefined best practices with a bearing on radiation exposure (range of quality score 0 – 8). The participating European countries were assigned to regions (North, East, South, and West). Comparisons were performed between the four European regions and between Europe and the rest-of-the-world (RoW).

Results

Data on 2,381 European patients undergoing nuclear cardiology procedures in 102 laboratories in 27 countries were collected. A cardiac SPECT study was performed in 97.9 % of the patients, and a PET study in 2.1 %. The average effective dose of SPECT was 8.0 ± 3.4 mSv (RoW 11.4 ± 4.3 mSv; P < 0.001) and of PET was 2.6 ± 1.5 mSv (RoW 3.8 ± 2.5 mSv; P < 0.001). The mean effective doses of SPECT and PET differed between European regions (P < 0.001 and P = 0.002, respectively). The mean quality score was 6.2 ± 1.2, which was higher than the RoW score (5.0 ± 1.1; P < 0.001). Adherence to best practices did not differ significantly among the European regions (range 6 to 6.4; P = 0.73). Of the best practices, stress-only imaging and weight-adjusted dosing were the least commonly used.

Conclusion

In Europe, the mean effective dose from nuclear cardiology is lower and the average quality score is higher than in the RoW. There is regional variation in effective dose in relation to the best practice quality score. A possible reason for the differences between Europe and the RoW could be the safety culture fostered by actions under the Euratom directives and the implementation of diagnostic reference levels. Stress-only imaging and weight-adjusted activity might be targets for optimization of European nuclear cardiology practice.

Indications for cardiovascular magnetic resonance in children with congenital and acquired heart disease: an expert consensus paper of the Imaging Working Group of the AEPC and the Cardiovascular Magnetic Resonance Section of the EACVI

This article provides expert opinion on the use of cardiovascular magnetic resonance (CMR) in young patients with congenital heart disease (CHD) and in specific clinical situations. As peculiar challenges apply to imaging children, paediatric aspects are repeatedly discussed. The first section of the paper addresses settings and techniques, including the basic sequences used in paediatric CMR, safety, and sedation. In the second section, the indication, application, and clinical relevance of CMR in the most frequent CHD are discussed in detail. In the current era of multimodality imaging, the strengths of CMR are compared with other imaging modalities. At the end of each chapter, a brief summary with expert consensus key points is provided. The recommendations provided are strongly clinically oriented. The paper addresses not only imagers performing CMR, but also clinical cardiologists who want to know which information can be obtained by CMR and how to integrate it in clinical decision-making.

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS)

Aims

To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing ‘best practices’ worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose.

Methods and results

We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March–April 2013. Eight ‘best practices’ relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more ‘best practices’ had lower EDs.

Conclusion

Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally.