Effects of Ivabradine on Myocardial Perfusion in Chronic Angina: A Prospective, Preliminary, Open-Label, Single-Arm Study

INTRODUCTION

Ivabradine reduces heart rate (HR), episodes of angina, and nitrate consumption, and increases exercise capacity in patients with chronic angina (CA). In this exploratory study, myocardial perfusion scintigraphy (MPS) was used to evaluate changes in the percentage of myocardial ischemia after ivabradine therapy in patients with CA.

METHODS

This prospective, open-label, single-arm study included patients with CA receiving maximum tolerated doses of beta blockers, who had a resting HR ≥ 70 bpm and had experienced ischemia according to MPS during an exercise test at baseline. Participants received ivabradine 5 mg twice daily (titrated according to HR) concomitant with beta blockers. A second MPS was performed after 3 months, without interruption of treatment with beta blockers or ivabradine. The primary outcome was change in the percentage of myocardial ischemia from baseline to 3 months. Time to ischemia during the exercise test, the proportion of patients presenting angina during the exercise test, and health status, assessed using the seven-item Seattle Angina Questionnaire-7 (SAQ-7), were also evaluated.

RESULTS

Twenty patients (3 females) with a mean (± standard deviation [SD]) age of 62.2 ± 6.5 years were included in the study, of whom 55% had diabetes, 70% had previous myocardial revascularization, and 45% had previous myocardial infarction. The percentage of patients with myocardial ischemia significantly decreased from baseline to 3 months after initiation of treatment with ivabradine (- 2.9%; 95% confidence interval [CI] - 0.3 to - 5.5; p = 0.031). Mean time to appearance of ischemia increased from 403 ± 176 s at baseline to 466 ± 136 s at 3 months after initiation of ivabradine (Δ62 s; 95% CI 18-106 s; p = 0.008), and the proportion of patients experiencing angina during the exercise test decreased from 40% at baseline to 5% also at 3 months (p = 0.016). Mean resting HR decreased from 76 ± 7 bpm at baseline to 55 ± 8 bpm at 3 months (p < 0.001). The mean SAQ-7 summary score improved from 69 ± 21 at baseline to 83 ± 12 at 3 months (p = 0.001). No serious adverse effects were reported.

CONCLUSION

Ivabradine added to beta blockers was associated with a reduction in detectable myocardial ischemia by MPS in patients with CA. Infographic available for this article.

TRIAL REGISTRATION

The trial has been retrospectively registered with the Brazilian Registry of Clinical Trials (REBEC) under the following number RBR-5fysqrh (date of registration: 30 November 2023).

Temporal trends in the contribution of modifiable cardiovascular risk factors to cardiovascular and all-cause mortality in patients undergoing myocardial perfusion imaging in a large city in Brazil

BACKGROUND

Most cardiovascular (CV) events stem from modifiable risk factors, but it remains uncertain whether their impact on mortality has decreased in recent years as a result of treatment, particularly in low- and middle-income countries. We evaluated the temporal trends in the population attributable fraction (PAF) of modifiable risk factors to CV mortality in patients undergoing myocardial perfusion imaging (MPI) for suspected coronary artery disease in a large city in Brazil.

METHODS

The cohort comprised 25,127 patients without established CV disease undergoing MPI in a referral center in Curitiba, Brazil, from 2010 to 2018. Baseline demographic, clinical and risk factors were prospectively collected. Modifiable risk factors encompassed hypertension, dyslipidemia, diabetes mellitus, sedentary lifestyle, obesity, and smoking. The primary outcome was CV death occurring up to 4 years of follow-up. The PAF of each risk factor was calculated for each triennium using multivariable Cox proportional regression models, adjusting for age, sex and family history of premature coronary disease.

RESULTS

Over 9 years, there were 1438 deaths, 444 due to CV causes. In the first triennium, sedentary lifestyle exhibited the highest PAF (49%) for CV death, followed by hypertension (17%), diabetes mellitus (8%) and smoking habit (6%). The PAF for all risk factors combined remained relatively stable thorough the triennia (2010-2012: 57% vs 2013-2015: 64% vs 2016-2018: 47%, p = NS).

CONCLUSION

In this large cohort of patients referred to MPI, the PAF of modifiable CV risk factors did not diminish in the last decade, with sedentary lifestyle having the largest contribution for CV mortality.

CONDENSED ABSTRACT

This study examinated temporal trends in the impact of modifiable cardiovascular (CV) risk factors on CV and overall mortality in a cohort of 25,127 patients undergoing myocardial perfusion imaging from 2010 to 2018. Sedentary behavior consistently had the greatest impact on both CV and overall mortality, followed by hypertension and diabetes. Smoking had a lesser effect, while obesity showed no independent association with the outcomes. The contributions of these modifiable CV risk factors remained stable over the study period, suggesting that interventions promoting physical activity may be essential in mitigating the burden of CV disease.

Cardiovascular Testing in the United States during the COVID-19 Pandemic: Volume Recovery and Worldwide Comparison

Purpose

To characterize the recovery of diagnostic cardiovascular procedure volumes in U.S. and non-U.S. facilities in the year following the initial COVID-19 outbreak.

Materials and Methods

The International Atomic Energy Agency (IAEA) coordinated a worldwide study called the IAEA Noninvasive Cardiology Protocols Study of COVID-19 2 (INCAPS COVID 2), collecting data from 669 facilities in 107 countries, including 93 facilities in 34 U.S. states, to determine the impact of the pandemic on diagnostic cardiovascular procedure volumes. Participants reported volumes for each diagnostic imaging modality used at their facility for March 2019 (baseline), April 2020, and April 2021. This secondary analysis of INCAPS COVID 2 evaluated differences in changes in procedure volume between U.S. and non-U.S. facilities and among U.S. regions. Factors associated with return to prepandemic volumes in the United States were also analyzed in a multivariable regression analysis.

Results

Reduction in procedure volumes in April 2020 compared with baseline was similar for U.S. and non-U.S. facilities (-66% vs -71%, P = .27). U.S. facilities reported greater return to baseline in April 2021 than did all non-U.S. facilities (4% vs -6%, P = .008), but there was no evidence of a difference when comparing U.S. facilities with non-U.S. high-income country (NUHIC) facilities (4% vs 0%, P = .18). U.S. regional differences in return to baseline were observed between the Midwest (11%), Northeast (9%), South (1%), and West (-7%, P = .03), but no studied factors were significant predictors of 2021 change from prepandemic baseline.

Conclusion

The reductions in cardiac testing during the early pandemic have recovered within a year to prepandemic baselines in the United States and NUHICs, while procedure volumes remain depressed in lower-income countries.Keywords: SPECT, Cardiac, Epidemiology, Angiography, CT Angiography, CT, Echocardiography, SPECT/CT, MR Imaging, Radionuclide Studies, COVID-19, Cardiovascular Imaging, Diagnostic Cardiovascular Procedure, Cardiovascular Disease, Cardiac Testing Supplemental material is available for this article. © RSNA, 2023.

Health Status and Clinical Outcomes in Older Adults With Chronic Coronary Disease: The ISCHEMIA Trial

BACKGROUND

Whether initial invasive management in older vs younger adults with chronic coronary disease and moderate or severe ischemia improves health status or clinical outcomes is unknown.

OBJECTIVES

The goal of this study was to examine the impact of age on health status and clinical outcomes with invasive vs conservative management in the ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches) trial.

METHODS

One-year angina-specific health status was assessed with the 7-item Seattle Angina Questionnaire (SAQ) (score range 0-100; higher scores indicate better health status). Cox proportional hazards models estimated the treatment effect of invasive vs conservative management as a function of age on the composite clinical outcome of cardiovascular death, myocardial infarction, or hospitalization for resuscitated cardiac arrest, unstable angina, or heart failure.

RESULTS

Among 4,617 participants, 2,239 (48.5%) were aged <65 years, 1,713 (37.1%) were aged 65 to 74 years, and 665 (14.4%) were aged ≥75 years. Baseline SAQ summary scores were lower in participants aged <65 years. Fully adjusted differences in 1-year SAQ summary scores (invasive minus conservative) were 4.90 (95% CI: 3.56-6.24) at age 55 years, 3.48 (95% CI: 2.40-4.57) at age 65 years, and 2.13 (95% CI: 0.75-3.51) at age 75 years (Pinteraction = 0.008). Improvement in SAQ Angina Frequency was less dependent on age (Pinteraction = 0.08). There were no age differences between invasive vs conservative management on the composite clinical outcome (Pinteraction = 0.29).

CONCLUSIONS

Older patients with chronic coronary disease and moderate or severe ischemia had consistent improvement in angina frequency but less improvement in angina-related health status with invasive management compared with younger patients. Invasive management was not associated with improved clinical outcomes in older or younger patients. (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches [ISCHEMIA]; NCT01471522).

Impact of COVID-19 Pandemic on Cardiovascular Testing in Asia

Background

The coronavirus disease-2019 (COVID-19) pandemic significantly affected management of cardiovascular disease around the world. The effect of the pandemic on volume of cardiovascular diagnostic procedures is not known.

Objectives

This study sought to evaluate the effects of the early phase of the COVID-19 pandemic on cardiovascular diagnostic procedures and safety practices in Asia.

Methods

The International Atomic Energy Agency conducted a worldwide survey to assess changes in cardiovascular procedure volume and safety practices caused by COVID-19. Testing volumes were reported for March 2020 and April 2020 and were compared to those from March 2019. Data from 180 centers across 33 Asian countries were grouped into 4 subregions for comparison.

Results

Procedure volumes decreased by 47% from March 2019 to March 2020, showing recovery from March 2020 to April 2020 in Eastern Asia, particularly in China. The majority of centers cancelled outpatient activities and increased time per study. Practice changes included implementing physical distancing and restricting visitors. Although COVID testing was not commonly performed, it was conducted in one-third of facilities in Eastern Asia. The most severe reductions in procedure volumes were observed in lower-income countries, where volumes decreased 81% from March 2019 to April 2020.

Conclusions

The COVID-19 pandemic in Asia caused significant reductions in cardiovascular diagnostic procedures, particularly in low-income countries. Further studies on effects of COVID-19 on cardiovascular outcomes and changes in care delivery are warranted.

Worldwide Variation in the Use of Nuclear Cardiology Camera Technology, Reconstruction Software, and Imaging Protocols

OBJECTIVES

This study sought to describe worldwide variations in the use of myocardial perfusion imaging hardware, software, and imaging protocols and their impact on radiation effective dose (ED).

BACKGROUND

Concerns about long-term effects of ionizing radiation have prompted efforts to identify strategies for dose optimization in myocardial perfusion scintigraphy. Studies have increasingly shown opportunities for dose reduction using newer technologies and optimized protocols.

METHODS

Data were submitted voluntarily to the INCAPS (International Atomic Energy Agency Nuclear Cardiology Protocols Study) registry, a multinational, cross-sectional study comprising 7,911 imaging studies from 308 labs in 65 countries. The study compared regional use of camera technologies, advanced post-processing software, and protocol characteristics and analyzed the influence of each factor on ED.

RESULTS

Cadmium-zinc-telluride and positron emission tomography (PET) cameras were used in 10% (regional range 0% to 26%) and 6% (regional range 0% to 17%) of studies worldwide. Attenuation correction was used in 26% of cases (range 10% to 57%), and advanced post-processing software was used in 38% of cases (range 26% to 64%). Stress-first single-photon emission computed tomography (SPECT) imaging comprised nearly 20% of cases from all world regions, except North America, where it was used in just 7% of cases. Factors associated with lower ED and odds ratio for achieving radiation dose ≤9 mSv included use of cadmium-zinc-telluride, PET, advanced post-processing software, and stress- or rest-only imaging. Overall, 39% of all studies (97% PET and 35% SPECT) were ≤9 mSv, while just 6% of all studies (32% PET and 4% SPECT) achieved a dose ≤3 mSv.

CONCLUSIONS

Newer-technology cameras, advanced software, and stress-only protocols were associated with reduced ED, but worldwide adoption of these practices was generally low and varied significantly between regions. The implementation of dose-optimizing technologies and protocols offers an opportunity to reduce patient radiation exposure across all world regions.

PET/CT-Guided Biopsy of Suspected Lung Lesions Requires Less Rebiopsy Than CT-Guided Biopsy Due to Inconclusive Results

The purpose of this study was to compare ¹⁸F-FDG PET/CT and CT performance in guiding percutaneous biopsies with histologic confirmation of lung lesions. Methods: We prospectively evaluated 341 patients, of whom 216 underwent ¹⁸F-FDG PET/CT-guided biopsy and 125 underwent CT-guided biopsy. The pathology results, lesion size, complications, and rebiopsy rate in the 2 groups were evaluated. Results: Of the 216 biopsies with PET/CT guidance, histology demonstrated 170 lesions (78.7%) to be malignant and 46 (21.3%) to be benign. In the CT-guided group, of 125 lesions, 77 (61.6%) were malignant and 48 (38.4%) were benign (P = 0.001). Inconclusive results prompted the need for a second biopsy in 18 patients: 13 of 125 (10.4%) in the CT group and 5 of 216 (2.3%) in PET group (P = 0.001). Complications were pneumothorax (13.2%), hemothorax (0.8%), and hemoptysis (0.6%). No life-threatening adverse events or fatalities were reported. The difference in complication rates between the 2 groups was not significant (P = 0.6). Malignant lesions showed a greater mean size than benign lesions regardless of the group (P = 0.015). Conclusion: PET/CT-guided biopsy of lung lesions led to fewer inconclusive biopsies than CT-guided biopsy, with similar complication rates.

P3353Safety and performance of stress testing: results from 78220 nuclear cardiology studies performed over 15 years in Brazil

Background

Stress testing for nuclear cardiology (NC) is safe for evaluating suspected or known coronary heart disease (CHD). Rates of serious adverse events (SAE) are low, roughly 1 death/myocardial infarction: 10,000 studies. However, this may vary depending on patient characteristics using different stress modalities.

Purpose

To describe the rates of SAE using different stress modalities in patients referred to NC.

Methods

We included all patients undergoing NC at Quanta in Curitiba, Brazil from 2003 to 2018. Stress modalities were categorized as: exercise (Ex), dipyridamole (Dip), a hybrid protocol of dypiridamole and low workload exercise (DipEx), and dobutamine (Dob). SAE during/after stress were recorded: cardiac arrest or ST segment elevation myocardial acute infarction (STEMI). Development of second or third degree atrial ventricular block (AVB) during stress and recovery were also recorded.

Results

From 78220 studies in 61984 patients (47% women, mean age 63 years-old), Ex was the most frequent stress modality (67%), followed by Dip (24%), DipEx (7%) and Dob (1,7%). Patients undergoing Ex were the youngest (mean age 60 vs 70 vs 65 vs 71 years old), the least likely of having hypertension (62 vs 78 vs 76 vs 75%) and diabetes (22 vs 35 vs 32 vs 32%) and had the lowest prevalence of known CHD (26 vs 35 vs 41 vs 30%, for Ex vs Dip vs DipEx vs Dob respectively, p<0.001 for all comparisons). Six patients had cardiac arrest and one STEMI, results in SAE rate of 1:11.144 studies. There was important differences among stress modalities, being higher for pharmacological stress, particularly DipEx (Table). This group had the highest prevalence of known CHD and higher baseline risk. AVB rates were higher when dipyridamole was used. All patients who arrested in the laboratory recovered with treatment.

Serious adverse events and stress in NC Adverse event Ex Dip DipEx Dob N=52,237 N=18,848 N=5,824 N=1,311 Cardiac Arrest or MI 1 : 17,412 1 : 9,424 1 : 2,912 None 2nd or 3rd Degree AVb 1 : 4,353 1 : 1,885 1 : 1,941 None Observe how adverse event rates different importantly in patients undergoing different stress modalities in NC.

Conclusion

In this large 15-year registry, rates of SAE related to stress testing in NC were low, albeit the SAE were much higher with pharmacological stress modalities, particularly with DipEx, which had the highest rate of patients with known CHD. Our findings suggest that the well-known 1:10,000 event rate does not necessarily apply to all stress modalities in NC. Physicians should take patient's baseline risk into account, particularly those requiring pharmacologic stress.

4223Income level and the prevalence of ischemic coronary heart disease in a low-mid-income country with high social inequalities. Influence of neighborhood walkability

Background

The greater burden of coronary heart disease (CHD) comes from low-middle income countries (LMIC). Socioeconomic status, environmental factors, poor access to healthcare, physical inactivity and excess consumption of carbohydrates, have explained part of this burden. However, the association between income level and CHD in LMIC with marked social inequalities is not fully understood, and whether there is influence of neighborhood walkability (walking-promoting potential of the residential built environment for daily activities) in this association requires further investigation.

Purpose

To investigate to what level income is associated with ischemic CHD in a LMIC with great social inequalities and to explore the potential role of neighborhood walkability in this association.

Methods

We evaluated patients referred for myocardial perfusion imaging with SPECT (SPECT-MPI) from February 2010 to August 2017 at a reference imaging center in our city, Brazil. Each patient was georeferenced and the exposure variable was the average income in Brazilian currency (Real) per month, from the patient's residential census block. Ischemic CHD was defined by an abnormal myocardial perfusion (summed stress score >3) during a SPECT-MPI study. Walkability was measured by a score combining street connectivity, residential density, commercial density and mixed land use. We used mixed effects models to evaluate the association between income level and ischemic CHD, adjusted for potential confounders, and performed a mediation analysis to measure the percentage of this association mediated by walkability.

Results

From 26,810 participants, those living in the lowest tertile income neighborhoods were younger (61±12 vs 63±13 vs 65±12 yrs old); with higher body mass index (28.4±5 vs 27.7±5 vs 27.4±4 kg/m2); more likely to be women (52 vs 49 vs 47%), current smokers (10 vs 9 vs 8%), sedentary (79 vs 76 vs 73%), having diabetes (27 vs 24 vs 23%), hypertension (65 vs 62 vs 60%) and with known CHD (21 vs 20 vs 19%) when compared to the second and the highest tertiles respectively, all with p<0.001. After adjusting for these potential confounders, income level was inversely associated with ischemic CAD (Figure). Neighborhoods with higher income levels were associated with better walkability scores (R = 0.34eta; p<0.001), but walkability did not mediate the association between income level and ischemic CHD (percent mediated = −0.3%).

Figure 1. Association of income and CHD

Conclusions

In this large registry from a LMIC population, living in a lower-income neighborhood was associated with higher prevalence of ischemic CHD. Even though neighborhood walkability was directly associated with neighborhood income, it did not explain the association between income level and ischemic CHD.

A need to reduce premature CV mortality in the developing world: How could appropriate use of non-invasive imaging help?

We discuss premature deaths due to coronary heart disease (CHD) in developing countries and the importance of a comprehensive approach, involving clinical judgement, prevention, appropriate use of technology to diagnose and guide CHD treatment. Healthcare policies and levels of knowledge vary tremendously resulting heterogeneous utilization of diagnostic strategies and treatments worldwide. Many countries with high mortality have low utilization of non-invasive cardiac imaging. Appropriate use coupled with guideline-based management could help to improve care in the developing world and potentially result in better life expectancy already experienced by most high-income countries. In a scenario of increasing costs, a rational utilization of resources is imperative for all nations. A stepwise approach to suspected CHD is necessary, starting from good judgement, adding tests only as needed, preferably filtering patients who might benefit from advanced imaging. In stable patients, non-invasive tests should be used as filters to invasive procedure, preventing stable patients from undergoing revascularizations of questionable benefit. In this article, we review the relative role of exercise testing, myocardial perfusion imaging, and coronary computed tomography angiography to evaluate CHD and how these can be utilized as ways to help guide management that could impact premature mortality in developing nations.

Value of gated-SPECT MPI for ischemia-guided PCI of non-culprit vessels in STEMI patients with multivessel disease after primary PCI

There remains a clinical question of which patients benefit from revascularization of non-culprit coronary artery stenosis in the setting of acute ST-segment elevation myocardial infraction (STEMI). This is a large population of patients with prior studies showing 40 to 70% of patients with STEMI having non-culprit stenosis. This article reviews the current state of the literature evaluating outcomes of those previously randomized to revascularization of non-culprit stenosis around the time of the STEMI. We propose a new study design to utilize gated-SPECT in the decision process by using an ischemic burden of > 5% as a cut-off for revascularization vs. complete revascularization without ischemia assessment.

Nuclear cardiology practices and radiation exposure in Africa: results from the IAEA Nuclear Cardiology Protocols Study (INCAPS)

Objective:

While nuclear myocardial perfusion imaging (MPI) offers many benefits to patients with known or suspected cardiovascular disease, concerns exist regarding radiationassociated health effects. Little is known regarding MPI practice in Africa. We sought to characterise radiation doses and the use of MPI best practices that could minimise radiation in African nuclear cardiology laboratories, and compare these to practice worldwide.

Methods:

Demographics and clinical characteristics were collected for a consecutive sample of 348 patients from 12 laboratories in six African countries over a one-week period from March to April 2013. Radiation effective dose (ED) was estimated for each patient. A quality index (QI) enumerating adherence to eight best practices, identified a priori by an IAEA expert panel, was calculated for each laboratory. We compared these metrics with those from 7 563 patients from 296 laboratories outside Africa.

Results:

to that of the rest of the world [9.1 (5.1–15.6) vs 10.3 mSv (6.8–12.6), p = 0.14], although a larger proportion of African patients received a low ED, ≤ 9 mSv targeted in societal recommendations (49.7 vs 38.2%, p < 0.001). Bestpractice adherence was higher among African laboratories (QI score: 6.3 ± 1.2 vs 5.4 ± 1.3, p = 0.013). However, median ED varied significantly among African laboratories (range: 2.0–16.3 mSv; p < 0.0001) and QI range was 4–8.

Conclusion:

Patient radiation dose from MPI in Africa was similar to that in the rest of the world, and adherence to best practices was relatively high in African laboratories. Nevertheless there remain opportunities to further reduce radiation exposure to African patients from MPI.

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.

Cardiac sympathetic nervous system imaging with 123I-meta-iodobenzylguanidine: Perspectives from Japan and Europe

Cardiac sympathetic nervous system dysfunction is closely associated with risk of serious cardiac events in patients with heart failure (HF), including HF progression, pump-failure death, and sudden cardiac death by lethal ventricular arrhythmia. For cardiac sympathetic nervous system imaging, 123I-meta-iodobenzylguanidine (123I-MIBG) was approved by the Japanese Ministry of Health, Labour and Welfare in 1992 and has therefore been widely used since in clinical settings. 123I-MIBG was also later approved by the Food and Drug Administration (FDA) in the United States of America (USA) and it was expected to achieve broad acceptance. In Europe, 123I-MIBG is currently used only for clinical research. This review article is based on a joint symposium of the Japanese Society of Nuclear Cardiology (JSNC) and the American Society of Nuclear Cardiology (ASNC), which was held in the annual meeting of JSNC in July 2016. JSNC members and a member of ASNC discussed the standardization of 123I-MIBG parameters, and clinical aspects of 123I-MIBG with a view to further promoting 123I-MIBG imaging in Asia, the USA, Europe, and the rest of the world.

Opportunities for improvement on current nuclear cardiology practices and radiation exposure in Latin America: Findings from the 65-country IAEA Nuclear Cardiology Protocols cross-sectional Study (INCAPS)

BACKGROUND

Comparison of Latin American (LA) nuclear cardiology (NC) practice with that in the rest of the world (RoW) will identify areas for improvement and lead to educational activities to reduce radiation exposure from NC.

METHODS AND RESULTS

INCAPS collected data on all SPECT and PET procedures performed during a single week in March-April 2013 in 36 laboratories in 10 LA countries (n = 1139), and 272 laboratories in 55 countries in RoW (n = 6772). Eight "best practices" were identified a priori and a radiation-related Quality Index (QI) was devised indicating the number used. Mean radiation effective dose (ED) in LA was higher than in RoW (11.8 vs 9.1 mSv, p < 0.001). Within a populous country like Brazil, a wide variation in laboratory mean ED was found, ranging from 8.4 to 17.8 mSv. Only 11% of LA laboratories achieved median ED <9 mSv, compared to 32% in RoW (p < 0.001). QIs ranged from 2 in a laboratory in Mexico to 7 in a laboratory in Cuba. Three major opportunities to reduce ED for LA patients were identified: (1) more laboratories could implement stress-only imaging, (2) camera-based methods of ED reduction, including prone imaging, could be more frequently used, and (3) injected activity of 99mTc could be adjusted reflecting patient weight/habitus.

CONCLUSIONS

On average, radiation dose from NC is higher in LA compared to RoW, with median laboratory ED <9 mSv achieved only one third as frequently as in RoW. Opportunities to reduce radiation exposure in LA have been identified and guideline-based recommendations made to optimize protocols and adhere to the "as low as reasonably achievable" (ALARA) principle.

Gender Differences in Radiation Dose From Nuclear Cardiology Studies Across the World: Findings From the INCAPS Registry

OBJECTIVES

The aim of this study was to investigate gender-based differences in nuclear cardiology practice globally, with a particular focus on laboratory volume, radiation dose, protocols, and best practices.

BACKGROUND

It is unclear whether gender-based differences exist in radiation exposure for nuclear cardiology procedures.

METHODS

In a large, multicenter, observational, cross-sectional study encompassing 7,911 patients in 65 countries, radiation effective dose was estimated for each examination. Patient-level best practices relating to radiation exposure were compared between genders. Analysis of covariance was used to determine any difference in radiation exposure according to gender, region, and the interaction between gender and region. Linear, logistic, and hierarchical regression models were developed to evaluate gender-based differences in radiation exposure and laboratory adherence to best practices. The study also included the United Nations Gender Inequality Index and Human Development Index as covariates in multivariable models.

RESULTS

The proportion of myocardial perfusion imaging studies performed in women varied among countries; however, there was no significant correlation with the Gender Inequality Index. Globally, mean effective dose for nuclear cardiology procedures was only slightly lower in women (9.6 ± 4.5 mSv) than in men (10.3 ± 4.5 mSv; p < 0.001), with a difference of only 0.3 mSv in a multivariable model adjusting for patients' age and weight. Stress-only imaging was performed more frequently in women (12.5% vs. 8.4%; p < 0.001); however, camera-based dose reduction strategies were used less frequently in women (58.6% vs. 65.5%; p < 0.001).

CONCLUSIONS

Despite significant worldwide variation in best practice use and radiation doses from nuclear cardiology procedures, only small differences were observed between genders worldwide. Regional variations noted in myocardial perfusion imaging use and radiation dose offer potential opportunities to address gender-related differences in delivery of nuclear cardiology care.

Nuclear cardiology and CVD in the developing world: Are we applying our scarce resources appropriately? Why is our mortality rate so high?

While mortality rates from cardiovascular diseases have progressively decreased in developed nations, this has not been observed to the same extent in the developing world. Nuclear Cardiology utilization remains low or non-existent for most of those living in the low-to-middle-income countries. How much of the decline in mortality observed in the developed world has to do with advanced cardiac imaging? Are we applying our scarce resources appropriately for myocardial perfusion imaging? Are myocardial revascularizations being guided by appropriate use criteria? Is more imaging necessary to reduce the mortality rates further in the developing world?

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.

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.

Assessing the need for nuclear cardiology and other advanced cardiac imaging modalities in the developing world

BACKGROUND

In 2005, 80% of cardiovascular disease (CVD) deaths occurred in low- to middle-income countries (i.e., developing nations). Cardiovascular imaging, such as myocardial perfusion SPECT, is one method that may be applied to detect and foster improved detection of at-risk patients. This document will review the availability and utilization for nuclear cardiology procedures worldwide and propose strategies to devise regional centers of excellence to achieve quality imaging around the world.

METHODS

As a means to establish the current state of nuclear cardiology, International Atomic Energy Agency member and non-member states were queried as to annual utilization of nuclear cardiology procedures. Other sources for imaging statistics included data from medical societies (American Society of Nuclear Cardiology, European Society of Cardiology, and the European Association of Nuclear Medicine) and nuclear cardiology working groups within several nations. Utilization was calculated by dividing annual procedural volume by 2007 population statistics (/100,000) and categorized as high (>1,000/100,000), moderate-high (250-999/100,000), moderate (100-249/100,000), low-moderate (50-99/100,000) and low (<50/100,000).

RESULTS

High nuclear cardiology utilization was reported in the United States, Canada, and Israel. Most Western European countries, Australia, and Japan reported moderate-high utilization. With the exception of Argentina, Brazil, Colombia and Uruguay, South America had low usage. This was also noted across Eastern Europe, Russia, and Asia. Utilization patterns generally mirrored each country's gross domestic product. However, nuclear cardiology utilization was higher for developing countries neighboring moderate-high "user" countries (e.g., Algeria and Egypt); perhaps the result of accessible high-quality training programs.

CONCLUSIONS

Worldwide utilization patterns for nuclear cardiology vary substantially and may be influenced by physician access to training and education programs. Development of regional training centers of excellence can guide utilization of nuclear cardiology through the application of guideline- and appropriateness-driven testing, training, continuing education, and quality assurance programs aiding developing nations to confront the epidemics of CVD.

Takotsubo or stress cardiomyopathy: role of nuclear cardiology using (123)I-MIBG

Takotsubo cardiomyopathy, also known as broken heart syndrome or stress cardiomyopathy, is a very interesting syndrome of acute transient left ventricular dysfunction, usually following significant emotional stress. It was first described in Japan nearly two decades ago and many aspects of its pathogenesis still remain poorly understood. The incidence of out-of-hospital sudden death related to Takotsubo is currently unknown. Excess catecholamines following stress seem to trigger Takotsubo and play an important role. The clinical presentation resembles acute myocardial infarction, including chest tightness and/or dyspnea, ECG changes and elevated cardiac enzymes. However, in contrast to a typical acute myocardial infarction, no significant coronary lesions or thrombi are found on coronary angiography. Differentiating Takotsubo from acute myocardial infarction is important to avoid the unnecessary risks of thrombolytic therapy. Typically, left ventriculography shows marked abnormalities with akinesia in the mid-distal anterior wall and apex (occasionally involving other heart regions), giving a balloon shape to the left ventricle. The name Takotsubo originates from the shape of the left ventricle, which resembles a Japanese octopus-trapping pot. Hospital mortality is low but death can be caused by severe acute heart failure and/or ventricular arrhythmias. Typically, a stressful life event is reported preceding the acute symptoms. Takotsubo is most common in menopausal women although young individuals, including men, can also be affected. The autonomic nervous system has a defined role in the process. In this article, we will review the role of imaging the heart using (123)I-meta-iodobenzylguanidine, a radioactive marker allowing mapping of the autonomic nervous system of the heart, in cases of suspected Takotsubo.

Baseline glucose and left ventricular remodeling after acute myocardial infarction

In patients with acute myocardial infarction (AMI), the mechanisms behind the increased mortality related to glucose levels (GL) are poorly understood. The main purpose of this study is to analyze the relationship between baseline glucose and left ventricular enlargement (LVE). We analyzed 52 patients with a first ST-elevation AMI <24 h of evolution. Glucose levels were obtained upon admission (median time, 3 h after the beginning of chest pain). The median GL was 123.5 mg/dl, and patients above this limit were considered hyperglycemic (n=26). Left ventricular enlargement was analyzed comparing two radionuclide ventriculographies, the first obtained within 4 days post-AMI (median, 55 h) and the second 6 months later (median, 188.5 days), taking into account the difference in the obtained end-systolic volumes. Myocardial reperfusion was evaluated comparing ST resolution between a first ECG done immediately upon hospital arrival with a second ECG performed 2 h after treatment. By univariate analysis, LVE correlated significantly with baseline hyperglycemia (P<.001), failed reperfusion by ECG criteria (P<.001), and no use of ACE inhibitors or AT1 blockers (P=.046) and aspirin (P=.046). A history of previous diabetes did not correlate significantly with LVE at 6 months. In the adjusted model, basal hyperglycemia (P<.001) and failed reperfusion (P=.001) were the only variables independently correlated with LVE. In conclusion, baseline glucose is a powerful and independent predictor of LVE after AMI, which reinforces the importance of a tight glucose control during the initial phase of the disease.

Exercise supplementation to dipyridamole prevents hypotension, improves electrocardiogram sensitivity, and increases heart-to-liver activity ratio on Tc-99m sestamibi imaging

BACKGROUND

Myocardial perfusion imaging with dipyridamole is an alternative with which to evaluate patients who are unable to exercise. Many patients who undergo dipyridamole testing are limited in their ability, but are not completely unable, to exercise. There are benefits from adding low workload exercise to dipyridamole testing, including a reduction of thallium 201 concentration in the liver, leading to a higher heart-to-liver activity ratio and better image quality. This prospective study was designed to evaluate a protocol of exercise supplementation during dipyridamole technetium 99m sestamibi imaging and to verify whether a higher heart-to-liver activity ratio could be obtained. We also evaluated the potential of this combined protocol to prevent hypotension and induce ischemic changes on the electrocardiogram (ECG).

METHODS AND RESULTS

Ninety consecutive patients who were not completely disabled for exercise underwent dipyridamole Tc-99m sestamibi cardiac single photon emission computed tomography with a protocol of exercise supplementation (DipEx). The heart-to-liver activity ratio, hemodynamics, and electrocardiographic changes were studied. The findings were compared with those of a control group (Dip) composed of 99 patients who underwent dipyridamole infusion alone. Patients with left bundle branch block, pacemaker, and atrial fibrillation were excluded. The DipEx patients tolerated the protocol, exercising 4.2 +/- 1.3 minutes on the treadmill (Bruce protocol). Compared with Dip, patients in the DipEx group had a higher heart-to-liver activity ratio (1.3 +/- 0.4 vs 1.6 +/- 0.5, respectively; P =.00001), had no incidence of hypotension (6% vs 0%, respectively; P =.03), and had a higher sensitivity of the ECG to detect ischemia (6% vs 34%, respectively; P =.003). The increase in sensitivity seen in the DipEx group was accompanied by a significant decrease in specificity compared with the Dip group (67% vs 100%, P =.000001).

CONCLUSIONS

Our data show that the addition of limited exercise to dipyridamole results in benefits during Tc-99m sestamibi imaging, increasing heart-to-liver activity ratio, preventing vasodilator-induced hypotension, and improving ECG sensitivity for the detection of ischemia. Furthermore, this protocol also provides an estimation of the patient's physical capacity and could be used as an alternative for patients undergoing dipyridamole infusion who are not completely unable to exercise.

Sustained reduction in myocardial reperfusion injury with an adenosine receptor antagonist: possible role of the neutrophil chemoattractant response

Recent studies have demonstrated that three membrane-permeant A(1) receptor antagonists reduced infarct size in a model of ischemia followed by brief reperfusion. However, it was not determined whether cardioprotection was mediated by nonspecific intracellular effects of these highly lipophilic drugs and whether the antagonists only delayed myocardial necrosis without affecting the ultimate infarct size. In the present study, closed-chest dogs were subjected to 90 min of left anterior descending coronary artery occlusion and 72 h of reperfusion and received either a nonmembrane-permeant adenosine receptor blocker that is devoid of direct intracellular effects and is 6-fold selective for the A(1) receptor [1, 3-dipropyl-8-p-sulfophenylxanthine (DPSPX); n = 11] or vehicle (n = 12). DPSPX was administered as three 200-mg boluses 60 min before and 30 and 120 min after reperfusion. The area of necrosis was determined histologically and expressed as a percentage of the area at risk. Baseline predictors of infarct size were similar in the two groups. The ratio of the area of necrosis to the area at risk was less in the DPSPX group (17.8 +/- 4.3% versus 35.0 +/- 1.9%; P =. 012), and DPSPX improved regional ventricular function. Under both basal and stimulated (formyl-Met-Leu-Phe) conditions, suspensions of human neutrophils generated extracellular adenosine levels (approximately 50 nM) sufficient to activate A(1) receptors. Moreover, both DPSPX and 1,3-dipropyl-8-cyclopentylxanthine, a selective A(1) receptor antagonist, significantly reduced the chemoattractant response of neutrophils to formyl-Met-Leu-Phe. We conclude that blockade of A(1) adenosine receptors attenuates myocardial ischemic/reperfusion injury, possibly in part by decreasing the chemoattractant response of neutrophils.

Losartan improves diastolic ventricular filling of hypertensive patients with diastolic dysfunction

To evaluate the role of losartan on left ventricular (LV) function of hypertensive patients. Hypertensive patients (n = 19) underwent evaluation of systolic and diastolic LV function, using radionuclide ventriculography (RVG), before and at 3 mo into the treatment with the angiotensin II antagonist losartan. All patients underwent a baseline 12 lead ECG and an echocardiogram (ECHO), which was also repeated at 3 mo into treatment. Results are expressed as mean +/- SEM and statistics were performed using paired t-test. A p value < or = 0.05 was considered significant. Treatment with losartan for 3 mo had no effect on LV mass measured by echo (141+/-5 vs. 139+/-6 g/m2). The LV ejection fraction, measured by RVG, was unchanged by treatment when compared to the baseline study (58+/-2% vs. 57+/-2%, respectivelly, p = 0.49). Considering all patients involved in the study (n = 19), the LV "Peak Filling Rate" (PFR), a parameter of diastolic function measured by RVG, was also unchanged by treatment when compared to baseline (2.5+/-0.2 EDV/s vs. 2.5+/-0.3 EDV/s, respectively, p = 0.9). However the analysis of those patients with evidence of diastolic dysfunction (n = 12) on the baseline RVG (PFR < 2.5 EVD/s), demonstrated significant improvement of LV filling after therapy with losartan (PFR = 1.8+/-0.1 EDV/s vs. 2.3 +/-0.2 EDV/s, respectively, p = 0.05). This change was associated with improvement of symptoms. Our results demonstrated that hypertensive patients with diastolic dysfunction on radionuclide ventriculography have significant improvement of ventricular filling at 3 mo into treatment with losartan.

Occult breast carcinoma presenting as an axillary mass

Breast carcinoma presents rarely (<5% of cases) as an axillary mass without an obvious primary tumor. The value of mammography in detecting an occult breast carcinoma is low, with a sensitivity of 29 per cent and specificity of 73 per cent. MRI and positron emission tomography (PET) are potentially more sensitive in this setting. We present a case recently seen at the Vanderbilt University Hospital, a 63-year-old woman with a 2-cm painless mass in the right axilla. Mammography was negative, and fine needle aspiration revealed atypical cells suspicious for malignancy. An excisional biopsy of the right axillary lymph node revealed metastatic adenocarcinoma, most likely breast primary. A PET showed increased uptake of 18-fluorodeoxyglucose and 99m Technetium in the right axilla and the right lateral breast. The patient underwent right modified radical mastectomy. The final pathological report revealed a 0.9-cm primary tumor in the upper inner quadrant of the breast and 1 of 41 nodes positive for tumor. This case confirms that mammography has low sensitivity in identifying the primary tumor in occult breast carcinoma and illustrates the usefulness of PET in identifying the primary tumor. We advocate an aggressive approach to evaluation of the breast in women presenting with metastatic adenocarcinoma in the axillary nodes. This evaluation should include clinical examination and mammography in all cases, and PET and MRI in selected cases. PET and MRI may be particularly useful when considering a breast-conserving surgical procedure.

Staging recurrent metastatic colorectal carcinoma with PET

Accurate detection of recurrent colorectal carcinoma remains a diagnostic challenge. The purposes of this study were to assess the accuracy of 18FDG-PET in patients with recurrent colorectal carcinoma in detecting liver metastases compared with computed tomography (CT) and CT portography, detecting extrahepatic metastases compared with CT and evaluating the impact on patient management.

METHODS

Fifty-two patients previously treated for colorectal carcinoma presented on 61 occasions with suspected recurrence and underwent 18FDG-PET of the entire body. PET, CT and CT portography images were analyzed visually. The final diagnosis was obtained by pathology (n = 44) or clinical and radiological follow-up (n = 17). The impact on management was reviewed retrospectively.

RESULTS

A total of 166 suspicious lesions were identified. Of the 127 intrahepatic lesions, 104 were malignant, and of the 39 extrahepatic lesions, 34 were malignant. Fluorine-18-fluorodeoxyglucose imaging was more accurate (92%) than CT and CT portography (78% and 80%, respectively) in detecting liver metastases and more accurate than CT for extrahepatic metastases (92% and 71%, respectively). Fluorine-18-fluorodeoxyglucose detected unsuspected metastases in 17 patients and altered surgical management in 28% of patients.

CONCLUSION

These data identify that 18FDG-PET is the most accurate noninvasive method for staging patients with recurrent metastatic colorectal carcinoma and plays an important role in management decisions in this setting.

Recurrent gallbladder carcinoma at laparoscopy port sites diagnosed by positron emission tomography: implications for primary and radical second operations

Inapparent gallbladder carcinoma discovered by histologic examination following 1 per cent of cholecystectomies generates a difficult clinical problem. There is evidence that radical resection can prolong survival, especially for locally advanced (> or = PT2, according to the Union International Centre Cancer pathologic T classification) lesions. Case reports of recurrence at port sites after laparoscopic cholecystectomy add another aspect to the management difficulty. A 64-year-old woman underwent laparoscopic cholecystectomy for biliary colic. Histologic evaluation revealed an incidental adenocarcinoma, stage pT3. Radical resection with curative intent occurred 11 days later, including mesohepatectomy, skeletonization resection of the common bile duct with en bloc lymph node dissection, and bilateral Roux-en-Y hepaticojejunostomies. There was no tumor identified in the re-excision specimen (T3N0M0). At 7-month follow-up, the patient presented with nodules in the right subcostal area and in the periumbilical incision. Positron emission tomography demonstrated carcinoma at both sites. Biopsy confirmed metastatic gallbladder carcinoma. This case emphasizes the significance of tumor seeding at port sites during laparoscopy. An open technique is indicated if carcinoma is suspected. To avoid dissemination of unsuspected carcinoma during routine laparoscopic procedures, isolation techniques must be applied. The benefit of radical resection was clearly thwarted in this case, and resection of port sites at the time of reoperation is warranted. Finally, positron emission tomography scan is useful in delineating the recurrence of gallbladder carcinoma and its extent.

Reduction of myocardial infarct size in rabbits and inhibition of activation of rabbit and human neutrophils by lidocaine

Myocardial reperfusion is associated with increased influx of activated neutrophils and intracellular accumulation of sodium in the ischemic zone. Lidocaine is a sodium channel blocker that also inhibits several neutrophil functions. We investigated the effect of lidocaine on infarct size in rabbits undergoing 30 minutes of ischemia and 48 hours of reperfusion. Animals randomly received lidocaine (10 mg/kg, n = 11) or saline (n = 11) during occlusion. The area of necrosis (AN) was measured histologically and expressed as a percentage of the area at risk (AR). Myocardial oxygen consumption and the perfusion bed at risk were similar in the two groups. Lidocaine reduced infarct size compared with control (AN/AR = 30% +/- 4% vs 61% +/- 5%, respectively; p = 0.0001). This reduction was associated with a significant decrease in neutrophil infiltration and in the degree of hemorrhage in the reperfused myocardium. Lidocaine also significantly inhibited superoxide anion production by rabbit and human neutrophils in whole blood. Therefore, lidocaine treatment results in a significant reduction in infarct size in the rabbit model, partly through reduction of neutrophil-mediated injury to viable cells, suggesting that lidocaine may be useful to enhance myocardial salvage in patients undergoing pharmacologic or mechanical reperfusion.

Role of endothelin in a rabbit model of acute myocardial infarction: effects of receptor antagonists

The role of endothelin (ET) in acute myocardial infarction and proarrhythmic potential was investigated in a rabbit model. One group of rabbits underwent 30 min of circumflex occlusion and 3 h of reperfusion with measurements of myocardial blood flow and myocardial levels of ET-1 messenger RNA (mRNA). In a second group, the systemic and coronary effects of exogenous ET were studied in animals pretreated with either saline, FR139317, an ETA-receptor antagonist, or PD145065, an ETA-and ETB-receptor antagonist. In a third study, animals undergoing 30 min of circumflex occlusion followed by 48 h of reperfusion were treated with exogenous ET-1, FR139317, PD145065, or saline. Arrhythmias were recorded and infarct size measured at 48 h. These studies revealed that ischemia and reperfusion was followed by a progressive microcirculatory failure ("no-reflow phenomenon") in rabbits. This was associated with a 2.6-fold elevation in levels of myocardial ET-1 mRNA in the ischemic zone in comparison to the nonischemic zone (p = 0.04). Exogenous ET-1 caused elevation in coronary and systemic vascular resistance that was significantly blocked by antagonism of the ETA receptor. In rabbits subjected to myocardial ischemia and reperfusion, ET-1 infusion led to a higher incidence of ventricular arrhythmias, whereas ET-receptor antagonism with PD145065 significantly reduced ventricular arrhythmias. Exogenous ET-1 and FR139317 failed to alter infarct size (AN) of the area at risk (AR) compared with control [AN/AR(%) was 46 +/- 8, 55 +/- 9, and 47 +/- 7, respectively]. However, PD145065 significantly decreased AN/AR (22 +/- 7; p < or = 0.02). The increased production of ET-1, resulting from increased levels of mRNA after reperfusion, may contribute to the no-reflow phenomenon. Although the vasoconstrictor effects of ET-1 can be blocked by ETA-receptor antagonism alone, only blockade of both the ETA and ETB receptors significantly reduced infarct size. These data suggest that production of ET increases in the heart during ischemia and is deleterious to the reperfused myocardium.

Positron emission tomography with F-18-fluorodeoxyglucose to evaluate the results of hepatic chemoembolization

BACKGROUND

Positron emission tomography (PET) using F-18-flurodeoxyglucose (18FDG) is an imaging modality allowing direct evaluation of cellular glucose metabolism. The purpose of this study was to examine the role of 18FDG-PET in monitoring chemoembolization therapy of patients with liver metastases from adenocarcinoma.

METHODS

Thirty-four hepatic lesions in 4 patients were evaluated with 18FDG-PET before and 2-3 months after interventional therapy. All patients underwent transcatheter arterial chemoembolization. A total of nine PET studies were performed. Semiquantitative measurement of the metabolic activity of the lesions was performed using the standard uptake value (SUV) of 18FDG. Comparison was performed between sequential PET scans using Student's t test for paired data analysis. The PET findings were also compared with tumor marker levels measured at the time of the PET scans.

RESULTS

Twenty-five of 34 lesions had decreased 18FDG uptake (SUV = 8 +/- 2 vs. 3 +/- 1; P < 0.00001), as expected in successful tumor chemoembolization. These findings were associated with a significant decrease in serum tumor marker levels (86 +/- 4%; P < 0.05) after treatment. However, there were 3 new lesions, and 6 of the 34 lesions demonstrated persistent or increased 18FDG uptake after treatment (SUV = 8 +/- 2 vs. 13 +/- 3; P < 0.05), consistent with the presence of residual viable tumor. These findings led to further interventional therapy in all patients.

CONCLUSIONS

18FDG-PET allows monitoring of response to treatment with hepatic chemoembolization in patients with liver metastases from adenocarcinoma. PET is a useful diagnostic tool and has the potential to be used to guide further interventional therapy.

Positron emission tomography to stage suspected metastatic colorectal carcinoma to the liver

BACKGROUND

Accurate detection of recurrent colorectal carcinoma remains a clinical challenge. Positron emission tomography (PET) using 18F-fluorodeoxyglucose (18FDG) is an imaging technique that allows direct evaluation of cellular metabolism. 18F-fluorodeoxyglucose PET was compared to computed tomography (CT) and CT portography for staging metastatic colorectal carcinoma.

PATIENTS AND METHODS

Twenty-four patients previously treated for colorectal carcinoma who had suspected recurrence to the liver underwent an 18FDG PET scan of the entire body. All patients had either a CT scan of the abdomen (n = 17), a CT portogram (n = 18), or both (n = 11). The final diagnosis was obtained by tissue pathology in 19 patients and clinical follow-up in 5 patients.

RESULTS

A total of 60 suspicious lesions were identified. Of the 55 intrahepatic lesions, 39 were malignant and 16 were benign. Of the 5 extra-hepatic lesions, 4 were malignant. The 18FDG PET imaging had a higher accuracy (93%) than CT and CT portography (both 76%) in detecting metastatic disease to the liver, and detected unsuspected extrahepatic recurrence in 4 patients. Although the sensitivity of 18FDG PET (90%) was slightly lower than that of CT portography (97%), the specificity was much higher (100% versus 9%), including postsurgical sites. 18FDG PET altered surgical plans in 6 (25%) of 24 patients.

CONCLUSIONS

18FDG PET is extremely useful in staging patients with suspected metastatic colorectal carcinoma to the liver.

Intravenous adenosine suppresses cardiac release of endothelin after myocardial ischaemia and reperfusion

OBJECTIVE

Intravenous adenosine decreases infarct size in experimental models of myocardial ischaemia/reperfusion. Ischaemia/reperfusion is associated with a significant increase in cardiac release of endothelin. The effect of cardioprotective doses of adenosine on endothelin release was explored in dogs undergoing 90 min coronary occlusion and 210 min reperfusion.

METHODS

Dogs were assigned to intravenous adenosine in a dose of 0.15 mg.kg-1.min-1 (n = 12) or control (n = 11) during the first 150 min reperfusion. Serial endothelin levels were obtained from the coronary sinus and aortic blood and measured by radioimmunoassay.

RESULTS

Adenosine significantly reduced infarct size expressed as a percent of the risk region (28.8 6% v 14.4 2%; p = 0.03). A similar increase in aortic and coronary sinus blood endothelin was observed in both groups during temporary occlusion. A significant transcardiac increase in endothelin levels was present in the control group 60 min after reperfusion whereas no increase occurred in the adenosine treated group [control 5.6(SEM 1.9) v adenosine -0.2(1.4) pg.ml-1; p = 0.02]. Similarly, intravenous adenosine tended to prevent the increase in myocardial endothelin production seen in control animals during the early reperfusion period [control 280(146) v adenosine -57(55) pg.min-1; p = 0.05]. Endocardial blood flow in the ischaemic zone 210 min after reperfusion was significantly higher in the adenosine group, at 0.60(0.02) v 0.38(0.02) ml.min-1.g-1; p < 0.05. A significant correlation between endothelin levels, endocardial flow and infarct size was observed in the control group 3 h after reperfusion: r = 0.73, p = 0.02; r = 0.62, p = 0.03 respectively. This relationship was absent in animals treated with adenosine.

CONCLUSIONS

Intravenous adenosine suppresses the release of endothelin from the previously ischaemic myocardium during the early reperfusion period. This effect may in part contribute to the improvement by adenosine in postischaemic microcirculatory flow resulting in attenuation of the "no reflow" phenomenon.