EACVI survey on radiation exposure in interventional echocardiography

AIMS

The European Association of Cardiovascular Imaging (EACVI) Scientific Initiatives Committee performed a global survey on radiation exposure in interventional echocardiography. The survey aimed to collect data on local practices for radioprotection in interventional echocardiography and to assess the awareness of echocardiography operators about radiation-related risks.

METHODS AND RESULTS

A total of 258 interventional echocardiographers from 52 different countries (48% European) responded to the survey. One hundred twenty-two (47%) participants were women. Two-thirds (76%) of interventional echocardiographers worked in tertiary care/university hospitals. Interventional echocardiography was the main clinical activity for 34% of the survey participants. The median time spent in the cath-lab for the echocardiographic monitoring of structural heart procedures was 10 (5-20) hours/month. Despite this, only 28% of interventional echocardiographers received periodic training and certification in radioprotection and 72% of them did not know their annual radiation dose. The main adopted personal protection devices were lead aprons and thyroid collars (95% and 92% of use, respectively). Dedicated architectural protective shielding was not available for 33% of interventional echocardiographers. Nearly two-thirds of responders thought that the radiation exposure of interventional echocardiographers was higher than that of interventional cardiologists and 72% claimed for an improvement in the radioprotection measures.

CONCLUSION

Radioprotection measures for interventional echocardiographers are widely variable across centres. Radioprotection devices are often underused by interventional echocardiographers, portending an increased radiation-related risk. International scientific societies working in the field should collaborate to endorse radioprotection training, promote reliable radiation dose assessment, and support the adoption of radioprotection shielding dedicated to interventional echocardiographers.

Translational molecular imaging: Thrombosis imaging with positron emission tomography

A key focus of cardiovascular medicine is the detection, treatment, and prevention of disease, with a move towards more personalized and patient-centred treatments. To achieve this goal, novel imaging approaches that allow for early and accurate detection of disease and risk stratification are needed. At present, the diagnosis, monitoring, and prognostication of thrombotic cardiovascular diseases are based on imaging techniques that measure changes in structural anatomy and biological function. Molecular imaging is emerging as a new tool for the non-invasive detection of biological processes, such as thrombosis, that can improve identification of these events above and beyond current imaging modalities. At the forefront of these evolving techniques is the use of high-sensitivity radiotracers in conjunction with positron emission tomography imaging that could revolutionise current diagnostic paradigms by improving our understanding of the role and origin of thrombosis in a range of cardiovascular diseases.

18F-sodium fluoride positron emission tomography and coronary plaque radiomics derived from computed tomography angiography for prediction of myocardial infarction

Background

Assessments of coronary disease activity with 18F-sodium fluoride positron emission tomography (18F-NaF PET) and radiomics-based precision coronary plaque phenotyping derived from contrast-enhanced computed tomography (CT) have both been shown to enhance risk stratification in patients with coronary artery disease (CAD). To date, no study has investigated whether these two promising methods (which can be obtained during a single imaging session on a hybrid PET/CT scanner) are interchangeable or can provide superior predictive performance when used in combination.

Purpose

We sought to investigate whether the prognostic information provided by latent morphological radiomic coronary plaque features and assessments of disease activity by 18F-NaF PET are complementary in prediction of myocardial infarction.

Methods

Patients with known CAD underwent coronary 18F-NaF PET and CT angiography on a hybrid PET/CT scanner. Coronary 18F-NaF uptake was determined by the coronary microcalcification activity (CMA). We performed quantitative plaque analysis of coronary CT angiography datasets. Additionally, coronary plaque segmentations on CT angiography were used to extract 1103 radiomic features. Using weighted correlation network analysis we derived latent morphological features of coronary plaques which were aggregated to patient-level radiomic normograms to predict myocardial infarction using univariate and multivariate Cox proportional hazard models.

Results

The study cohort comprised of 260 patients with established CAD (age: 65±9 years; 84% men); 179 (69%) participants showed increased coronary 18F-NaF activity (CMA >0). Over 53 [40–59] months of follow-up 18 patients had a myocardial infarction. Using weighted correlation network analysis, from the 1103 radiomic features we derived 15 distinct eigen radiomic features representing latent morphological coronary plaque patterns. On univariate cox modelling 7 of these emerged as predictors of myocardial infarction (Figure). Following adjustments for calcified, noncalcified and low-density noncalcified plaque volumes and 18F-NaF CMA 4 radiomic features (related to texture and geometry) remained independent predictors of myocardial infarction (Figure).

Conclusion(s)

In patients with established CAD latent morphological features of coronary plaques are predictors of myocardial infarction above and beyond plaque volumes and 18F-NaF uptake. Comprehensive plaque analysis with radiomics may enhance risk stratification of CAD patients.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIH, Wellcome Trust

Manganese enhanced magnetic resonance imaging in type 1 and type 2 diabetes mellitus

Background

The pathophysiology of diabetic cardiomyopathy has yet to be established although pre-clinical studies suggest a role for altered myocardial calcium handling. Manganese-enhanced magnetic resonance imaging (MEMRI) is a novel non-invasive method of assessing in vivo myocardial calcium handling.

Purpose

To investigate whether myocardial calcium handling is impaired in patients with either type 1 or type 2 diabetes mellitus in the absence of underlying heart disease.

Methods

In a prospective case-control study, patients with type 1 (n=19) or type 2 (n=10) diabetes mellitus and healthy volunteers (n=15) underwent MEMRI. Participants with prior coronary artery disease, cardiomyopathy or an abnormal electrocardiogram were excluded. Manganese dipyridoxyl diphosphate (0.1 mL/kg) was administered over 10 min and myocardial T1 mapping was performed prior to and every 2.5 min for 30 min after contrast infusion (Figure 1). Quantitative manganese uptake analysis was performed by measuring T1 relaxation times in a region of interest within the interventricular septum and compared to the left ventricular blood pool. The rate of myocardial manganese uptake was determined by Patlak modelling [1].

Results

Participants with type 1 and type 2 diabetes mellitus were older (50±13 and 55±15.3 years) than the healthy volunteers (32±10 years). All participants had preserved left ventricular ejection fraction (type 1 diabetes mellitus, 67.7±6.1%; type 2 diabetes mellitus, 66.8±3.2%; healthy volunteers, 65±3.5%). Mean myocardial manganese uptake was reduced in participants with both type 1 (6.4±0.6 mL/100 g of tissue/min) and type 2 (6.4±0.5 mL/100 g of tissue/min) diabetes mellitus compared with healthy volunteers (8.3±0.5 mL/100 g of tissue/min; p<0.0001 for both, Figure 2). There were no differences in myocardial manganese uptake between those with type 1 or type 2 diabetes mellitus (p=0.22). There was no statistically significant correlation between myocardial manganese uptake and age in the study population (r=−0.28, p=0.07).

Conclusion

Using MEMRI, we have demonstrated that myocardial calcium handling is impaired in patients with either type 1 or type 2 diabetes mellitus even in the absence of left ventricular systolic dysfunction. This suggests altered myocardial calcium handling may underlie, or contribute to, diabetic cardiomyopathy which has implications developing novel therapeutic targets for the prevention and treatment of diabetic cardiomyopathy.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation - Clinical Research Training Fellowship (FS/CRTF/20/24087)AstraZeneca - Investigator initiated award (ESR-19-20118)

Manganese-enhanced magnetic resonance imaging in Takotsubo syndrome

Background

Takotsubo syndrome is an increasingly common acute cardiac emergency characterised by profound transient left ventricular systolic dysfunction following a stressful event. Its pathophysiology remains poorly understood and a third of patients will have a major adverse cardiac or cerebrovascular event by 5 years [1]. Defective myocardial calcium homeostasis is central to contractile dysfunction and may be implicated in its pathophysiology. Manganese-enhanced magnetic resonance imaging is a novel non-invasive imaging technique that assesses myocardial manganese uptake as a measure of myocardial calcium handling [2]. Our aim was to investigate myocardial calcium handling using manganese-enhanced magnetic resonance imaging during the acute and recovery phase of takotsubo syndrome.

Methods

This single centre case-controlled observational longitudinal cohort study was conducted in accordance with the Declaration of Helsinki and ethical committee approval with written informed consent. Twenty patients with takotsubo syndrome and 20 age, sex and cardiovascular risk factor matched volunteers were recruited between March 2020 and September 2021. Patients underwent gadolinium and manganese-enhanced magnetic resonance imaging during the index event with repeat manganese-enhanced magnetic resonance imaging after 3 months. Myocardial manganese uptake was characterised by Patlak modelling.

Results

During the acute presentation, most patients had an “apical” pattern of takotsubo syndrome with reduced left ventricular ejection fraction (51±11 versus 67±8%, P<0.001, Figure 1), elevated left ventricular mass (89±11 versus 57±14 g/m2, P<0.01) and native T1 (1358±49 versus 1211±28 ms, P<0.001) and T2 (60±7 versus 38±3 ms, P<0.001) values compared to matched volunteers. Patlak modelling demonstrated reduced myocardial manganese uptake (5.1±0.5 versus 8.0±1.0 mL/100g of tissue/min, P<0.0001) consistent with a major abnormality of myocardial calcium handling. Reduced myocardial manganese uptake attributable to apical takotsubo syndrome could be seen in one patient, scanned 18 days after symptom onset despite apparent resolution of cardiac function. Beyond 3 months of convalescence, left ventricular mass, ejection fraction, native T1 and T2 values were comparable to matched volunteers. Despite this, myocardial calcium handling remained abnormal compared to matched volunteers (6.7±0.7 versus 8.0±1.0 mL/100 g of tissue/min, P<0.001, Figure 2).

Conclusions

In patients with takotsubo syndrome, there is a profound perturbation of myocardial calcium handling which is most marked acutely but persists after apparent recovery of left ventricular ejection fraction and resolution of myocardial oedema. Abnormal myocardial calcium handling is implicated in the pathophysiology of takotsubo syndrome and manganese-enhanced magnetic resonance imaging could play a major role in the diagnosis and risk stratification of patients with takotsubo syndrome.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Medical Research CouncilBritish Heart Foundation

Imaging of post-infarct myocardial inflammation with 68Ga-DOTATATE PET/MRI

Background

After myocardial infarction (MI), inflammation and its resolution modulate the extent of myocardial damage. 68Ga-DOTATATE is a PET tracer that binds to somatostatin receptor 2 (SST2), which is up-regulated in pro-inflammatory macrophages [1].

Purpose

We investigated 68Ga-DOTATATE PET/MRI for quantifying post-infarct myocardial inflammation.

Methods

In this prospective observational cohort study, participants with MI underwent 68Ga-DOTATATE PET/MRI at baseline (t0: <2 weeks post-MI) and 3 months (t3M). Patients with prior MI, heart failure, coronary revascularisation, or contraindication to PET/MRI, were excluded. Blood samples were taken at the time of imaging for high sensitivity CRP (hsCRP), high sensitivity troponin I (hsTnI), NTproBNP and peripheral blood monocyte subset counts measured by mass cytometry. 68Ga-DOTATATE maximum Standardised Uptake Values (SUV) and Tissue-to-Background Ratios (TBR) adjusted for blood pool activity were compared in the infarct defined by late gadolinium enhancement (LGE) MRI to remote myocardium at t0 and t3M.

Results

Thirty-two patients (mean age 59 [SD 9] years; 26 [81%] male and 6 [19%] female), comprised of 18 (56%) patients with ST elevation MI and 14 (44%) with non-ST elevation MI, were enrolled. Mean peak troponin was 16,953ng/L (range 408 to >25,000ng/L), and 16 (52%) patients had left ventricular impairment (ejection fraction <50%).

68Ga-DOTATATE PET signal co-localised with myocardial LGE and focal oedema (arrows) on T2-weighted MRI (Fig. 1; asterisk: culprit artery) and had excellent ability to discriminate infarct from remote regions (t0: infarct SUV 2.41 vs. remote 1.58, p<0.0001; t0: infarct TBR 5.08 vs. 3.35, p<0.0001; Fig. 2a).

At 100 (SD 13) days after MI (n=23 patients), residual 68Ga-DOTATATE uptake in the infarct remained higher than remote myocardium (t3M: infarct SUV 1.88 vs. remote 1.27, p<0.0001; t3M: infarct TBR 3.96 vs. remote 2.73, p<0.0001), but was reduced compared to baseline (SUV −22%, p<0.0001; TBR −22%, p=0.002; Fig. 2b).

Reduction in infarct 68Ga-DOTATATE uptake was consistent with overall decreases in hsCRP (2.16 vs. 8.76 mg/L), hsTnI (19 vs. 1365 ng/L) and NTproBNP (372 vs. 959 pg/mL) at t3M vs. t0 (n=23, all p<0.05). Focal oedema on MRI was resolved in 17 (74%) patients at t3M. Infarct-to-remote TBR ratio at t0 was correlated with hsTnI (r=0.35, p<0.05). At t3M (n=9 samples) vs t0 (n=20 samples), there was a reduction in % classical-to-non-classical ratio of peripheral monocytes (mean 6.5 [SD 3.8] vs. 14.4 [SD 11.2], p=0.005).

Conclusions

This is the first prospective study of serial 68Ga-DOTATATE PET/MRI in patients after MI. Here we show that 68Ga-DOTATATE tracks resolving myocardial inflammation. Ongoing work as part of this study seeks to confirm the cellular origin of infarct-related 68Ga-DOTATATE PET signal and SST2 expression within inflamed myocardial tissue, and test its longer-term association with ischaemic myocardial remodelling.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Wellcome TrustBritish Heart Foundation

Impaired myocardial calcium handling in people with type 2 diabetes: an in vivo manganese-enhanced magnetic resonance imaging study

Background

There is a high prevalence of subclinical cardiac dysfunction in people with type 2 diabetes (T2D) which is associated with subsequent development of heart failure. Dysregulated myocardial calcium handling has been demonstrated in animal models of T2D and may be a key mechanism driving the development of heart failure. Manganese-enhanced cardiac magnetic resonance imaging (MEMRI) provides a unique method to assess in vivo myocardial calcium handling.

Purpose

To determine whether myocardial calcium handling is perturbed in people with T2D with no history of cardiovascular disease. We hypothesised that myocardial manganese uptake would be reduced in people with T2D compared with healthy volunteers.

Methods

Cross-sectional case-control study, adults with (n=20) and without (n=9) T2D underwent both gadolinium-enhanced MRI and MEMRI. Standard gadolinium-enhanced MRI was used to assess cardiac structure, function and tissue characteristics. MEMRI scans were performed within two weeks of the initial scan. Native T1 maps were obtained in the mid-short axis slice position using a Modified Look-Locker Inversion recovery sequence. An intravenous infusion of manganese dipyridoxyl diphosphate (5 μmol/kg (0.1 mL/kg) at 1 mL/min) was administered and T1 maps at the same location were repetitively acquired every 2.5 min for 30 min. Regions of interest were drawn in the inferoseptal segment and blood pool for all T1 maps from 0 to 30 min by a single observer. The primary outcome was the rate of manganese uptake which was assessed by Patlak modelling as a measure of myocardial calcium handling. Manganese uptake constants were compared using analysis of co-variance, with age, sex and body mass index as co-variates.

Results

Subjects with T2D were older (62±7 vs. 57±5 years, p=0.046) but body mass index (29.0±4.5 vs. 26.2±3.4 kg/m2, p=0.106), systolic (135±16 vs. 134±17 mmHg, p=0.809) and diastolic (81±10 vs. 83±9 mmHg, p=0.736) blood pressures were similar. Compared to control subjects, participants with T2D had normal systolic function but more concentric left ventricular remodelling (mass/volume ratio 0.90±0.14 vs. 0.71±0.06 g/mL, p<0.001) and reduced peak early diastolic strain rate (0.64±0.17 vs. 0.91±0.26 s–1, p=0.002). Myocardial manganese uptake was substantially reduced in people with T2D compared with controls (6.51±1.46 vs. 8.45±2.52 ml/100 g of tissue/min, p=0.003) (Figure 1).

Conclusions

For the first time, we have demonstrated in vivo that despite no history of cardiovascular disease and normal systolic function, patients with T2D have marked impairment of myocardial calcium handling. This has potential major implications for the pathogenesis, diagnosis and treatment of diabetic cardiomyopathy.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation and National Institute for Health Research

Novel contrast-computed tomography method based on a Gaussian Mixture Model for assessment of fibrocalcific volume in aortic valve stenosis

Background

Discordant echocardiography is observed in up to one third of patients with aortic stenosis (AS), in whom computed tomography (CT) derived aortic valve calcium scoring is now recommended. However, CT calcium scoring only assesses calcific valve thickening and ignores non-calcific fibrotic thickening, which could be an important contributor of AS.

Purpose

To generate a quick and robust contrast-CT method based on a gaussian mixture model (GMM) for assessment of fibro-calcific aortic valve thickening in patients with AS, and to investigate its reproducibility and associations with echo parameters of AS severity and disease progression.

Methods

A post-hoc analysis of 136 patients with calcific AS (24 with severe, 81 moderate and 31 mild AS) enrolled in the SALTIRE2 trial (NCT-02132026) was performed. Aortic valve fibrocalcific volume was calculated using a GMM applied on contrast-CT at baseline and at 1-year follow up. The software estimated the Hounsfield Units (HU) distribution of 3 compartments (blood pool, non-calcific and calcific tissue) within the aortic valve volume of interest, automatically generating thresholds for non-calcific and calcific tissue, respectively computed as the lower 99.7 and the upper 99.7 percentile of the blood pool HU distribution (Figure 1). Fibrocalcific volume was measured as the sum of calcific and non-calcific volumes, indexed for CT annulus area and compared to echo parameters of AS severity. Evaluation of scan-rescan reproducibility and AS progression were also assessed.

Results

Image analysis took 5.8±1.0 minutes per scan and showed excellent scan-rescan reproducibility (mean difference −1%, limits of agreement −9% to 7%). Indexed-fibrocalcific volume correlated well with echocardiographic aortic peak velocity (rho=0.70, p<0.0001), better than non-calcific and calcific volumes alone (rho=0.30 and rho=0.61 respectively, both p<0.0001) and Agatston calcium score (rho=0.63, p<0.0001). Baseline indexed-fibrocalcific volume was also the strongest predictor of subsequent AS progression in terms of change in aortic valve peak velocity (rho=0.29, p=0.006) and mean gradient (rho=0.39, p<0.0001). Progression-to-noise ratio for fibrocalcific volume was favourable (Cohen's statistic d=0.62), indicating that groups sizes of 21, 46 and 170 participants would be required to demonstrate 30%, 20% and 10% reductions in fibro-calcific volume progression with a novel drug respectively (alpha=0.05, power=80%).

Conclusions

This novel contrast CT-based approach can provide robust and rapid assessment of fibrocalcific thickening in AS patients. Fibrocalcific volume measured using this technique, correlates well with other markers of AS severity, predicts disease progression and holds promise in tracking disease progression and response to novel therapies.

Funding Acknowledgement

Type of funding sources: None.

Let there be light! The meteoric rise of cardiac imaging

Imaging plays a central role in modern cardiovascular practice. It is a field characterised by exciting technological advances that have shaped our understanding of pathology and led to major improvements in patient diagnosis and care. The UK has played a key international role in the development of this subspecialty and is the current home to many of the leading global centres in multimodality cardiovascular imaging. In this short review, we will outline some of the key contributions of the British Cardiovascular Society and its members to this rapidly evolving field and look at how this relationship may continue to shape future cardiovascular practice.

In vivo coronary artery thrombus imaging with 18F-GP1 PET-CT

Background

Coronary artery thrombus is typically present in type 1 myocardial infarction, but small volumes in the setting of an uncertain culprit lesion may be beyond the detection limit of current imaging modalities.

Purpose

Using a novel glycoprotein IIb/IIIa-receptor radiotracer, 18F-GP1, we investigated whether positron emission tomography-computed tomography (PET-CT) could detect thrombus formation in coronary arteries.

Methods

In a single centre cross-sectional study, patients over 40 years of age with myocardial infarction were recruited after myocardial infarction and underwent underwent CT angiography and 18F-GP1 PET-CT. Stable patients with and without coronary artery disease formed a control cohort. Coronary artery 18F-GP1 uptake was visually assessed and quantified using maximum target-to-background ratios (TBRmax).

Results

Ninety-four (44 post-myocardial infarction and 50 control patients) were included in the cross-sectional analysis. The mean age of the post-myocardial infarction group was 61±9 years, three-quarters were male and two thirds had presented with ST elevation on electrocardiography. 34 (80%) patients post-myocardial infarction, but none of the control patients, demonstrated focal 18F-GP1 uptake in the coronary arteries.

Of 42 vessels with an angiographic culprit lesion, 35 (83%) had 18F-GP1 uptake which was significantly higher than non-culprit vessels (p<0.0001) as well as control vessels (p<0.0001), while non-culprit vessel uptake was similar to control vessel uptake (p=0.567): culprit vessel median TBRmax 1.2 [interquartile range 0.96–1.44], non-culprit vessel TBRmax 0.96 [0.84–1.03] and control vessel TBRmax 0.9 [0.76 to 0.94]. Linear regression models demonstrated univariable associations between coronary 18F-GP1 TBRmax and time from myocardial infarction, male sex and presence of culprit vessel. On multivariable analysis, only culprit vessel status was associated with TBRmax (adjusted R2= 0.22, P<0.001). Based on the Youden's index of the ROC curves, the optimal cut-off of predicting the presence of a culprit vessel was 1.20 with a specificity of 97%, accuracy of 83%, sensitivity (60%) and c-statictic of 0.74.

A patient with ectatic vessel and visual thrombus demonstrated the most intense 18F-GP1 uptake (TBRmax 2.0, highest in the cohort) in the region of heaviest thrombus burden (Figure 2). Extra-coronary uptake was seen in regions of left ventricular thrombus, left atrial appendage thrombus, pulmonary thromboembolism and intramyocardial microvascular obstruction.

Conclusions

18F-GP1 PET-CT is able to detect coronary artery thrombus in culprit lesions following myocardial infarction, as well as extra-coronary thrombotic pathologies that may be important in guiding patient management. 18F-GP1 is highly specific in recognising a culprit lesion from a non-culprit lesion both visually as well as quantitatively.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Figure 1Figure 2

18F-Sodium fluoride positron emission tomography, aortic disease activity and ischaemic stroke risk

Background

Arterial 18F-sodium fluoride (18F-NaF) activity on positron emission tomography (PET) is a marker of active microcalcification and atherosclerosis. Coronary 18F-NaF activity (CMA) predicts coronary artery disease progression and subsequent myocardial infarction.

Objective

To investigate whether aortic 18F-NaF activity (AMA) predicts thoracic aortic atherosclerotic disease progression and subsequent ischaemic stroke or myocardial infarction in patients with established cardiovascular disease.

Methods

In a post-hoc observational cohort study, we evaluated AMA and CMA in patients with stable coronary artery disease (n=239) or aortic stenosis (n=158) who had underwent thoracic 18F-NaF PET and computed tomography (CT). We assessed the associations between AMA or CMA and progression of calcified atherosclerotic plaque in both thoracic aortic and coronary territories on follow up CT, as well as subsequent ischaemic stroke or myocardial infarction.

Results

In 141 and 231 patients with repeat aortic and coronary CT imaging respectively at 12.7±2.7 months, AMA correlated with log progression of thoracic aortic calcium scores (r=0.21, p=0.011), volume (r=0.29, p<0.01) and mass (r=0.29, P<0.01) as well as log coronary calcium score progression (r=0.21, p=0.03). CMA correlated with log coronary (r=0.42, p<0.01), but not log aortic (p>0.80) calcium score progression. In 397 patients, 16 had an ischaemic stroke and 25 had a myocardial infarction after 4.7±1.6 years. After adjusting for clinical risk factors, CMA and calcium scoring, AMA was associated with stroke (hazard ratio, 1.71 [95% confidence interval 1.00–2.90], p=0.048]). AMA was superior to clinical risk and calcium scores in identifying patients with stroke (c-statistic 0.76 versus 0.58 versus 0.63 respectively, p<0.05). Survival analysis demonstrated that AMA was associated with ischaemic stroke (p<0.001) but not myocardial infarction (p=0.45), whereas CMA was associated with myocardial infarction (p<0.001) but not stroke (p=0.39).

Conclusions

In patients with established cardiovascular disease, AMA is associated with progression of aortic atherosclerosis and future ischaemic stroke. Arterial 18F-NaF identifies localised areas of atherosclerotic disease activity that relate to regional atherothrombotic events.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation AMA, disease progression and outcomesVariables associated with stroke

Plasma desmosine as a biomarker in acute aortic syndrome

Introduction

Acute aortic syndromes (AAS) include aortic dissection, intramural haematoma and penetrating aortic ulcer, all of which are caused by aortic wall failure and associated with significant mortality. Although, treatment options currently include early surgical intervention or aggressive medical management, disease progression and devastating complications remain commonplace. Early diagnosis of AAS as well as ability to predict those at the highest risk of disease progression would represent significant progress in the care these patients receive. Desmosine is the cross-link component in the elastin molecule and is exclusively released from mature elastin breakdown, thus is a physiologically relevant biomarker of aortic elastin degradation. The aim of the study was to test the hypothesis that plasma desmosine (pDES) concentrations are elevated in AAS and has prognostic value in indentifying those at risk of significant disease progression.

Method

Patients over 25 years old with radiologically confirmed acute aortic syndrome were recruited as part of a prospective observational study (NCT03647566). Demographic details, AAS sub-category, time from index acute aortic syndrome event and pDES concentrations measured by stable isotope dilution LC-MS/MS were recorded at baseline. Baseline and follow up maximal aortic diameters were measured on contrast-enhanced computed tomography (CT) and change in aortic diameter over time was calculated. Control plasma desmosine samples were obtained at a 2:1 ratio control subjects participating in the United Kingdom Aneurysm Growth Study. Data presented as mean±standard deviation or median [interquartile range].

Results

Plasma desmosine concentrations were measured in 53 patients (64 [53 to 71] years) with acute aortic syndromes and 106 control subjects (53 [44 to 60] years). In patients with AAS, pDES concentrations were almost twice those of control subjects (0.58±0.26 vs 0.27±0.07, p<0.001). In those with AAS, plasma desmosine concentrations were seen to be highest at presentation, and reduced over time from the aortic syndrome event (R=0.51, p=0.003). Plasma desmosine concentration was the only variable associated with increasing aortic diameter over time (R=0.34, p=0.014).

Conclusion

Plasma desmosine concentrations are elevated in patients with AAS, peak at the time of presentation and represents a promising biomarker for early identification and risk stratification in patients with AAS.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): British Heart FoundationTenovus Scotland Major Research GrantChief Scientist Office Catalytic Grant Plasma desmosine, time and expansionBaseline characteristics

Mechanisms of myocardial injury and clinical outcomes in patients hospitalised with suspected COVID-19

Background

Myocardial injury is associated with adverse outcomes in patients with COVID-19. However, the prognostic role of myocardial injury in COVID-19 compared to other acute illnesses and the underlying mechanisms of injury are poorly understood.

Methods

In a prospective, multi-centre, cohort study conducted in secondary and tertiary care hospitals in Scotland, all consecutive patients with suspected COVID-19 underwent cardiac troponin (ARCHITECTSTAT high-sensitive troponin I (hs-cTnI) assay; Abbott Laboratories) testing in plasma that was surplus to clinical requirements. The results were not reported unless required by the attending clinician. We evaluated the prevalence of myocardial injury, mechanisms and outcomes in all patients. In those with any hs-cTnI concentration above the sex-specific 99th centile the diagnosis was adjudicated according to the 4th Universal Definition of Myocardial Infarction. The primary outcome of all-cause mortality was compared in those with and without myocardial injury and COVID-19 by cox regression adjusted for age, sex, renal function and co-morbidities.

Results

A total of 2,916 (median age 69 [interquartile range, IQR 54–79] years, 53% women) consecutive patients with suspected COVID-19 were followed up for 228 [IQR 203–249] days. Myocardial injury occurred in 26% (750/2,916) with a median troponin concentration of 66 [35–178] ng/L; the prevalence was 41% (46/112) and 25% (704/2,804) in those with and without COVID-19, respectively. The most common mechanism was acute non-ischaemic myocardial injury occurring in 80% (37/46) and 71% (502/704) of patients with and without COVID-19, respectively. Type 1 myocardial infarction (2% and 4%), type 2 myocardial infarction (7% and 14%) and chronic myocardial injury (11% and 11%) were less common and only one patient had confirmed myocarditis. In patients with myocardial injury mortality was increased compared to those without (P<0.001 log rank), whether they had COVID-19 (54% [25/46] versus 26% [17/66]) or not (35% [248/704] versus 14% [294/2100]). Myocardial injury was an independent predictor of death in all patients (adjusted hazard ratio [aHR] 2.04, 95% confidence interval [CI] 1.71 to 2.43), but this excess risk was not higher in patients with COVID-19 (aHR 1.58, 95% CI 0.75 to 3.15) compared to those without the condition (aHR 2.01, 95% CI 1.81 to 2.49).

Conclusion

Myocardial injury is common in hospitalised patients with suspected COVID-19 whether or not COVID-19 was the cause of their presentation. The majority of patients had acute non-ischaemic myocardial injury rather than a defined cardiac condition. Despite this the presence of myocardial injury was an independent predictor of death in all hospitalised patients.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation Kaplan-Meier curve for all-cause death

Pericoronary adipose tissue attenuation, low-attenuation plaque burden and 5-year risk of myocardial infarction

Introduction

Pericoronary adipose tissue (PCAT) attenuation has emerged as a surrogate marker of pericoronary inflammation. To date, no studies have compared the impact of pericoronary adipose tissue (PCAT) attenuation and quantitative plaque burden on cardiac outcomes.

Purpose

We aimed to establish the relative merits of these approaches to risk prediction and hypothesised that the combination of PCAT attenuation and quantitative plaque burden measures could provide additive and improved prediction of myocardial infarction in patients with stable chest pain.

Methods

In a post-hoc analysis of a randomized controlled trial, we investigated the association between the future risk of fatal or non-fatal myocardial infarction and PCAT attenuation measured from CT coronary angiography using multivariable Cox regression models including plaque burden, obstructive coronary disease and cardiac risk score (incorporating age, sex, diabetes, smoking, hypertension, hyperlipidaemia and family history of cardiovascular disease).

Results

In 1697 evaluable participants (mean age 58±10 years), there were 37 myocardial infarctions after a median follow-up of 4.7 [interquartile interval, 4.0–5.7] years. Median low-attenuation plaque burden was 4.20 [0–6.86] % and mean PCAT −76±8 Hounsfield units (HU).

PCAT attenuation of the right coronary artery (RCA) was predictive of myocardial infarction (hazard ratio [HR] 1.55, 95% CI 1.08–2.22; p=0.017, per 1 standard deviation increment) with an optimum threshold of −70.5 HU [Hazards ratio (HR) 2.45, 95% CI 1.2–4.9; p=0.01]. Univariable analysis also identified the burden of non-calcified, low-attenuation and calcified plaque as well as Agatston coronary calcium score, presence of obstructive coronary artery disease and cardiovascular risk score were predictors of myocardial infarction (Figure 1). In multivariable analysis, only the low-attenuation plaque burden (HR 1.80, 95% CI 1.16 to 2.81, p=0.011, per doubling) and PCAT-RCA (HR 1.47 95%1.02 to 2.13, p=0.040, per standard deviation increment) remained predictors of myocardial infarction (Figure 1).

In multivariable analysis, adding PCAT-RCA ≥-70.5 HU to low-attenuation plaque burden >4% (optimum threshold for future myocardial infarction; HR = 4.87, 95% CI 2.03–11.78; p<0.0001) led to improved prediction of future myocardial infarction (HR 11.7, 95% CI 3.3–40.9; p<0.0001); Figure 2. In ROC analysis, integration of PCAT-RCA attenuation and LAP burden, increased the prediction for myocardial infarction compared to LAP alone (ΔAUC=0.04; p=0.01).

Conclusion

CT coronary angiography defined PCAT attenuation and low-attenuation plaque have marked and additive predictive value for the risk of fatal or non-fatal myocardial infarction.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Chief Scientist Office of the Scottish Government Health and Social Care Directorates, British Heart Foundation, National Institute of Health/National Heart, Lung, and Blood Institute grant

Association of coronary artery calcium score groups with qualitative and quantitatively assessed adverse plaque

Introduction

Coronary artery calcification is a marker of cardiovascular risk, but its association with qualitatively and quantitatively assessed plaque subtypes on coronary computed tomography (CT) angiography (CCTA) is unknown.

Methods

In this post-hoc analysis, CT images and clinical outcomes were assessed in SCOT-HEART trial participants. Agatston coronary artery calcium score (CACS) was measured on non-contrast CT and was stratified as zero (0 Agatston units, AU), minimal (1 to 9AU), low (10 to 99AU), moderate (100 to 399AU), high (400 to 999AU) and very high (≥1000AU). Adverse plaques were investigated with qualitative (visual categorisation of positive remodelling, low-attenuation plaque, spotty calcification, napkin ring sign) and quantitative (calcified, non-calcified, low-attenuation and total plaque burden) methods.

Results

Images of 1769 patients were assessed (mean age 58±9 years, 56% male, median Agatston score 21 [interquartile range 0 to 230] AU). Of these 36% had a zero, 9% minimal, 20% low, 17% moderate, 10% high and 8% very high CACS. Amongst patients with a zero CACS, 14% had nonobstructive disease, 2% had obstructive disease, 2% had visually assessed adverse plaques and 13% had quantitative low-attenuation plaque (LAP) burden >4% (Figure 1). Non-calcified and low-attenuation plaque burden increased between patients with zero, minimal and low CACS (p<0.001), but there was no difference between those with medium, high and very high CACS. Over a median follow-up of 4.8 [4.1 to 5.7] years, fatal or non-fatal myocardial infarction occurred in 41 patients, 10% of whom had zero CACS. CACS ≥1000AU (Hazard ratio (HR) 4.55 [1.20 to 17.3], p=0.026) and low-attenuation plaque burden (HR 1.74 [1.19 to 2.54], p=0.004) were the only predictors of myocardial infarction, independent of obstructive disease and cardiovascular risk score. Figure 2 shows example CCTA images in a patient with zero CACS, non-calcified plaque (red), low attenuation plaque (orange) burden >4% and obstructive disease in the left anterior descending coronary artery.

Conclusions

In patients with stable chest pain, a zero CACS is associated with a good prognosis, but 1 in 6 have coronary artery disease, including the presence of adverse plaques.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): British Heart Foundation, National Institute of Health/National Heart, Lung, and Blood Institute

Long-term cardiac risk in individuals with low calcium score on coronary computed tomography angiography can be stratified by the pericoronary fat radiomic profile (FRP)

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): UKRI, British Heart Foundation

Background

Inflammation in the coronaries induces macroscopic changes in perivascular adipose tissue composition, detectable by the pericoronary Fat Radiomic Profile (FRP) on coronary computed tomography angiography (CCTA).

Purpose

To assess the ability of FRP to stratify cardiac risk in patients with Coronary Artery Calcium (CAC) score below 100 following routine CCTA.

Methods

1,575 participants from the CCTA arm of the SCOT-HEART trial (NCT01149590) eligible for image analysis were included. Pericoronary FRP mapping was performed in perivascular adipose tissue segmentations around the proximal sites of the right and left coronary arteries, as previously validated. We first tested the prognostic value of FRP in the sub-cohort of patients with CAC < 100. We further analysed a sub-group based on the absence of high risk plaque (HRP) features and obstructive coronary artery disease (CAD). The association with future incidence of major adverse cardiac events (MACE: cardiac mortality or non-fatal myocardial infarction) or a composite endpoint of MACE ± late revascularization (MACE-ReVasc) was assessed using adjusted Cox regression models [adjusted for age, sex, systolic blood pressure (SBP), diabetes mellitus (DM), body mass index (BMI), smoking, CAD (≥50% stenosis), total cholesterol, high-density lipoprotein (HDL), and HRP features].

Results

In total, 1,032 patients (53.9% female sex) were found with low CAC score (CAC < 100), with a median age of 55 years. Over a mean follow-up of 4.87 ± 1.06 years, 12 MACE and 47 MACE-ReVasc were recorded. High FRP was associated with a 14.4-fold (95% CI: 3.80-54.78, p < 0.001) higher adjusted risk of MACE and a 2.8-fold (95% CI: 1.49-5.36, p = 0.001) higher adjusted risk of MACE-ReVasc (A). Addition of high FRP to a baseline model consisting of traditional risk factors (age, sex, systolic blood pressure, diabetes mellitus, BMI, smoking, CAD (≥50% stenosis), total cholesterol, HDL, HRP) significantly enhanced (deltaAUC at 5 years:0.15, p = 0.03) the model’s performance and reclassified individuals (NRI = 0.59, p = 0.02, B). Interestingly, after more rigorous filtering of the population by absence of HRP features and obstructive CAD, high FRP remained an independent predictor of MACE (n = 756, Adj.HR = 28.1, p = 0.003).

Conclusion

In individuals with low CAC scores the Fat Radiomic Profile biormarker significantly improves risk prediction for adverse clinical events beyond the current state-of-the-art. Non-invasive profiling of pericoronary adipose tissue using CCTA-derived FRP captures irreversible changes in perivascular adipose tissue composition associated with chronic vascular inflammation and atherosclerotic disease, and can supplement the traditional anatomical assessment of the coronary vasculature with a functional marker of disease activity.

Hybrid 18f-sodium fluoride PET/CT of the thoracic aorta identifies patients at increased risk of stroke

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): British Heart Foundation Clinical Research Training Fellowship

Background

Calcification of the thoracic aorta is associated with poor vessel wall health. Early detection of this disease process may highlight those at risk of future cardiovascular events.

Purpose

To investigate the potential of hybrid 18F-sodium fluoride (18F-NaF, a marker of vascular disease and microcalcification activity) positron emission tomography/computed tomography (PET/CT) to predict aortic disease progression and adverse cardiovascular events in patients with established risk factors.

Methods

Between 2015 and 2017, 197 patients underwent 18F-NaF PET/CT of the thoracic aorta as part of a randomised controlled trial.  Baseline 18F-NaF aortic microcalcification activity (AMA) was calculated as the cumulative uptake in a standardised volume of interest of the arch and ascending aorta.  Thirty-seven patients underwent follow up CT enabling aortic calcium score progression calculation.  Fatal/non-fatal stroke (primary endpoint) and fatal/non-fatal myocardial infarction (MI, secondary endpoint) were recorded up to May 2020.  The association between baseline AMA and both the progression of aortic calcium score and defined endpoints was analysed.  AMA was stratified into tertiles (low, moderate or high). Data is presented as mean(SD) or median [IQR].

Results

18F-NaF AMA correlated with the progression of aortic calcium score (R = 0.42, P = 0.01).  During 3.8 (0.9) years of follow up, 14 patients experienced the primary (stroke, n = 5) or secondary (MI, n = 9) endpoint.  Patients who experienced stroke had higher AMA (171 [162-176] vs 150 [141 - 157], P = 0.0015). Increased cumulative incidence of stroke was seen in the highest AMA tertile (Figure, P = 0.019).  There was no association between AMA and MI (P > 0.05).

Conclusion

Aortic microcalcification activity, as measured using 18F-NaF PET/CT, predicts the progression of aortic wall calcification and is associated with an increased risk of stroke but not MI.  Consolidating these findings in further studies will improve stroke risk prediction using 18F-NaF PET/CT.

Table Baseline characteristics Overall n = 197 Low AMA (<144) n = 66 Moderate AMA (144-155) n = 66 High AMA (>155) n = 65 p-value (ANOVA / X2) Age (±sd) 65.17 (8.30) 64.02 (9.43) 65.47 (7.40) 66.03 (7.95) 0.364 Male Sex (%) 157 (80.5) 54 (83.1) 52 (78.8) 51 (79.7) 0.808 Ever Smoked (%) 101 (60.5) 37 (71.2) 32 (56.1) 32 (55.2) 0.164 Hypertension (%) 110 (56.4) 31 (47.7) 35 (53.0) 44 (68.8) 0.043 High Cholesterol (%) 188 (96.4) 60 (92.3) 65 (98.5) 63 (98.4) 0.093 Type II Diabetes (%) 37 (19.0) 16 (24.6) 9 (13.6) 12 (18.8) 0.277 AMA = aortic microcalcification activity, MI = myocardial infarction, sd = standard deviation, TIA = transient ischaemic attack, X2 = Chi squared Abstract Figure: AMA and Stroke

18F-Sodium fluoride PET/CT detects transcatheter aortic valve degeneration

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by the British Heart Foundation, London, United Kingdom

Background

Early detection of transcatheter aortic valve implantation (TAVI) degeneration is challenging and only feasible when advanced haemodynamic valve dysfunction is apparent. 

Purpose

We tested whether 18F-sodium fluoride (18F-NaF) positron emission tomography and computed tomography (PET/CT) could detect structural TAVI degeneration and haemodynamic valve dysfunction. 

Methods

After TAVI implantation, patients underwent baseline echocardiography, CT angiography and 18F-NaF PET/CT (Figure). We assessed for morphological changes, stenosis or regurgitation on Doppler echocardiography, CT (hypoattenuated leaflet thickening [HALT] or spotty calcification) and PET (18F-NaF uptake; maximum target-to-background ratio, TBRmax). We categorised structural valve degeneration (SVD) according to the standardised definition for surgical and transcatheter bioprosthetic valves, as proposed in a recent consensus statement. 

Results

We recruited 47 patients (81 ± 6 years old, 79% male) 1 month (n = 9), 2 years (n = 22) or 5 years (n = 16) after TAVI: 25 (53%) had received a balloon expanded bioprosthesis and 22 (47%) a self-expanding valve. There was moderate valve dysfunction on Doppler echocardiography in 3 (6%) patients, HALT on CT in 6 (13%) patients, spotty calcification in one patient and 18F-NaF uptake in 7 patients (15%) (TBRmax range: 1.59-5.88); all enrolled 5 years post-TAVI.

All patients with increased 18F-NaF uptake (TBRmax ≥1.59) demonstrated either SVD without haemodynamic valve dysfunction (stage 1, n = 4) or structural valve dysfunction with moderate valve dysfunction and mean transprosthetic pressure gradients >20 mmHg (stage 2, n = 3). In patients without increased 18F-NaF uptake there was no evidence of structural valve degeneration (n = 40).

Within the increased 18F-NaF uptake (n = 7) group, patients with stage 2 SVD (n = 3) demonstrated higher uptake compared to patients with stage 1 SVD (TBRmax 4.3 [3.02-5.88] versus 1.8 [1.59-2.28]). Patients with stage 2 SVD (n = 3) had over 3 times higher TBRmax than those without SVD (n = 40) (4.30 [3.02, 5.88] versus 1.31 [1.21, 1.46]; p < 0.001); Figure).

Conclusion

18F-NaF PET/CT detects patients with SVD and potentially identifies those at risk of valve failure.

Abstract Figure.

Manganese-enhanced magnetic resonance imaging in dilated cardiomyopathy and hypertrophic cardiomyopathy

AIMS

The aim of this study is to quantify altered myocardial calcium handling in non-ischaemic cardiomyopathy using magnetic resonance imaging.

METHODS AND RESULTS

Patients with dilated cardiomyopathy (n = 10) or hypertrophic cardiomyopathy (n = 17) underwent both gadolinium and manganese contrast-enhanced magnetic resonance imaging and were compared with healthy volunteers (n = 20). Differential manganese uptake (Ki) was assessed using a two-compartment Patlak model. Compared with healthy volunteers, reduction in T1 with manganese-enhanced magnetic resonance imaging was lower in patients with dilated cardiomyopathy [mean reduction 257 ± 45 (21%) vs. 288 ± 34 (26%) ms, P < 0.001], with higher T1 at 40 min (948 ± 57 vs. 834 ± 28 ms, P < 0.0001). In patients with hypertrophic cardiomyopathy, reductions in T1 were less than healthy volunteers [mean reduction 251 ± 86 (18%) and 277 ± 34 (23%) vs. 288 ± 34 (26%) ms, with and without fibrosis respectively, P < 0.001]. Myocardial manganese uptake was modelled, rate of uptake was reduced in both dilated and hypertrophic cardiomyopathy in comparison with healthy volunteers (mean Ki 19 ± 4, 19 ± 3, and 23 ± 4 mL/100 g/min, respectively; P = 0.0068). In patients with dilated cardiomyopathy, manganese uptake rate correlated with left ventricular ejection fraction (r2 = 0.61, P = 0.009). Rate of myocardial manganese uptake demonstrated stepwise reductions across healthy myocardium, hypertrophic cardiomyopathy without fibrosis and hypertrophic cardiomyopathy with fibrosis providing absolute discrimination between the healthy myocardium and fibrosed myocardium (mean Ki 23 ± 4, 19 ± 3, and 13 ± 4 mL/100 g/min, respectively; P < 0.0001).

CONCLUSION

The rate of manganese uptake in both dilated and hypertrophic cardiomyopathy provides a measure of altered myocardial calcium handling. This holds major promise for the detection and monitoring of dysfunctional myocardium, with the potential for early intervention and prognostication.

Imaging aortic valve calcification: significance, approach and implications

Aortic stenosis is the most prevalent valvular heart disease worldwide, and rates are increasing with the growing and more elderly population. Although the precise mechanisms that underpin aortic valve stenosis are incompletely understood, pathological valvular calcification has emerged as a key instigator in mediating the biomechanical stiffening that can lead to symptoms, the need for aortic valve replacement, and death if left untreated. Here, we review the currently understood processes leading to aortic valve calcification, summarise the contemporary imaging assessments of valve calcification, and highlight how these might improve patient care and accelerate our pathological understanding and the development of an effective medical therapy.

Sex differences in left ventricular remodelling, myocardial fibrosis and mortality after aortic valve replacement

OBJECTIVES

To investigate sex differences in left ventricular remodelling and outcome in patients undergoing surgical or transcatheter aortic valve replacement (SAVR/TAVR).

METHODS

In this multicentre, observational, outcome study with imaging core-lab analysis, patients with severe aortic stenosis (AS) listed for intervention at one of six UK centres were prospectively recruited and underwent cardiovascular magnetic resonance imaging. The primary endpoint was all-cause mortality and secondary endpoint was cardiovascular mortality.

RESULTS

674 patients (425 men, 249 women, age 75±14 years) were included: 399 SAVR, 275 TAVR. Women were older, had higher surgical risk scores and underwent TAVR more frequently (53% vs 33.6%, p<0.001). More men had bicuspid aortic valves (BAVs) (26.7% vs 14.9%, p<0.001) and demonstrated more advanced remodelling than women. During a median follow-up of 3.6 years, 145 (21.5%) patients died, with no significant sex difference in all-cause mortality (23.3% vs 20.5%, p=0.114), but higher cardiovascular mortality in women (13.7% vs 8.5%, p=0.012). There were no significant sex-related differences in outcome in the SAVR or TAVR subgroups, or after excluding those with BAV. Factors independently associated with all-cause mortality were age, left ventricular ejection fraction (LVEF), BAV (better) and myocardial fibrosis detected with late gadolinium enhancement (LGE) in men, and age, LVEF and LGE in women. Age and LGE were independently associated with cardiovascular mortality in both sexes.

CONCLUSIONS

Men demonstrate more advanced remodelling in response to a similar severity of AS. The higher cardiovascular mortality observed in women following AVR is accounted for by women having less BAV and higher risk scores resulting in more TAVR. LGE is associated with a worse prognosis in both sexes.

Ferumoxytol-enhanced MRI in patients with prior cardiac transplantation

Objectives

Ultra-small superparamagnetic particles of iron oxide (USPIO)-enhanced MRI can detect cellular inflammation within tissues and may help non-invasively identify cardiac transplant rejection. Here, we aimed to determine the normal reference values for USPIO-enhanced MRI in patients with a prior cardiac transplant and examine whether USPIO-enhanced MRI could detect myocardial inflammation in patients with transplant rejection.

Methods

Ten volunteers and 11 patients with cardiac transplant underwent T2, T2* and late gadolinium enhancement 1.5T MRI, with further T2* imaging at 24 hours after USPIO (ferumoxytol, 4 mg/kg) infusion, at baseline and 3 months.

Results

Ten patients with clinically stable cardiac transplantation were retained for analysis. Myocardial T2 values were higher in patients with cardiac transplant versus healthy volunteers (53.8±5.2 vs 48.6±1.9 ms, respectively; p=0.003). There were no differences in the magnitude of USPIO-induced change in R2* in patients with transplantation (change in R2*, 26.6±7.3 vs 22.0±10.4 s^-1 in healthy volunteers; p=0.28). After 3 months, patients with transplantation (n=5) had unaltered T2 values (52.7±2.8 vs 52.12±3.4 ms; p=0.80) and changes in R2* following USPIO (29.42±8.14 vs 25.8±7.8 s^-1; p=0.43).

Conclusion

Stable patients with cardiac transplantation have increased myocardial T2 values, consistent with resting myocardial oedema or fibrosis. In contrast, USPIO-enhanced MRI is normal and stable over time suggesting the absence of chronic macrophage-driven cellular inflammation. It remains to be determined whether USPIO-enhanced MRI may be able to identify acute cardiac transplant rejection.

Trial registration number

NCT02319278349 (https://clinicaltrials.gov/ct2/show/NCT02319278) Registered 03.12.2014 EUDraCT 2013-002336-24.

5966Whole-vessel coronary 18F-sodium fluoride coronary microcalfication activity is associated with Low density plaque

Background

18F-sodium fluoride (18F-NaF) showed promise in imaging vulnerable coronary plaques. To date reporting of the highest per patient target to background ratio (TBR), total number of lesions with visual uptake and whole-heart tracer activity have been proposed. Unfortunately, each of these approaches has limitations which become especially prominent in patients with multiple foci of uptake, where reproducible global per-vessel measures are required. In oncology, the total metabolic active tumor volume has been found to be a significant prognostic factor for disease progression, recurrence and death. We evaluated if such methodology could be applied to coronary PET imaging.

Purpose

To quantify whole-vessel coronary 18F-NaF PET activity by utilizing automatically derived coronary vessel regions of interest (ROI) from CT angiography and assess the relationship between coronary microcalcification activity (CMA) and per vessel quantitative plaque characteristics on coronary CT angiography (CTA).

Methods

Twenty patients (68±6 years old, 70% males) with multivessel coronary artery disease underwent a 30 min single bed position PET 1h after a 250mB injection of 18F-NaF and CTA on a hybrid PET/CT scanner. We assessed coronary 18F-NaF uptake using novel whole-vessel tubular and tortuous 3D ROIs which were automatically extracted from CTA datasets. Within such ROIs we measured mean standard uptake value (SUV), maximum TBR (TBRmax) and the activity of voxels (CMA) above 1.25 the background SUV (left atrium activity). We used a previously established 1.25 TBRmax threshold to distinguish vessels positive and negative for 18F-NaF uptake. Coronary CTA datasets were analyzed by semi-automated software to quantify volumes and percentage lesion content of non-calcified plaque (NCP), low-density non-calcified plaque (LD-NCP, attenuation <30 Hounsfield units) and calcified plaque (CP).

Results

13 (65%) patients and 24 (40%) out of 60 main epicardial vessels presented with 18F-NaF uptake exceeding the 1.25 TBRmax threshold. While coronaries positive for uptake had higher CMA 0.92 [0.17, 2.03] vs 0.0, p<0.001 and TBRmax 1.42 [1.35, 1.74] vs 1.09 [1.0, 1.19], there was no difference in whole-vessel SUVmean 0.90 [0.77, 1.17] vs 0.87 [0.78, 0.96], p=0.33 compared to 18F-NaF negative arteries. Of the quantitative plaque characteristics vessels positive for uptake had higher NCP 278.4 [145.6, 576.9] vs 184.6 [63.8, 367.0]mm3, p=0.030; and LD-NCP 8.4 [0.3, 11.0] vs 2.7 [12.1, 43.5]mm3, p=0.01. CMA showed a stronger correlation with LD-NCP (r=0.70, p<0.001) than TBRmax (r=0.52, p<0.001). On regression analysis LD-NCP acted as an independent predictor of CMA after adjustments for CP and vessel SUVmean (p<0.001).

Figure 1

Conclusions

Whole-vessel 18F-NaF coronary microcalcification activity assessment with CT angiography automatically derived 3-dimensional ROIs is feasible and the measured coronary microcalcification burden correlates well with low density plaque.

Acknowledgement/Funding

This research was supported by grants R01HL135557 and R01HL133616 from the NHLBI/NIH and a grant from the Dr. Miriam & Sheldon G. Adelson MRF

172Coronary 18F-sodium fluoride uptake predicts progression of coronary arterial calcification

Background

Combined positron emission tomography and computed tomography (PET-CT) using 18F-sodium fluoride (18F-NaF) to detect microcalcification provides the opportunity to gain important insights into disease activity in coronary atherosclerosis. However, the relationship between 18F-NaF uptake and progression of coronary calcification has not been determined.

Purpose

To determine the relationship between 18F-NaF uptake and progression of coronary calcification in patients with clinically stable coronary artery disease (CAD).

Methods

Patients with established, multivessel CAD underwent 18F-NaF PET-CT and CT coronary calcium scoring at baseline, with repeat CT calcium scoring at one year. Coronary arterial PET uptake was analysed qualitatively and semi-quantitatively in diseased vessels by measuring maximum tissue-to-background ratio (TBRmax) – defined as the maximum standardised uptake value in a plaque divided by mean blood pool activity measured in the right atrium. Coronary calcification was quantified by measuring calcium mass, volume, average calcium density and total Agatston score (AU).

Results

In total, 185 patients underwent baseline and repeat imaging (median age 66 years, 80% men), and 118 (64%) had increased 18F-NaF uptake in at least one vessel. Median total calcium score, volume, mass and average density were higher in patients with compared to those without increased 18F-NaF uptake (Table 1). At one year, patients with evidence of increased 18F-NaF uptake demonstrated more rapid progression of coronary calcification (97 [39–166] AU) versus those without uptake (35 [7–93] AU; p<0.0001). Amongst 18F-NaF-positive patients, the calcium score increased only in coronary segments with 18F-NaF uptake (baseline 90.5 [27.5–202] AU versus one year 135.5 [59.3–281.8] AU; p<0.0001) and not in 18F-NaF-negative segments (baseline 44.5 [16–110.5] AU versus one year 46.5 [18.25–114] AU; p=0.446). There was a moderate correlation between TBRmax and change in total calcium score, volume and mass at 1 year (Spearman's Rho = 0.37, 0.38, 0.46 respectively; p<0.0001 for all).

Coronary calcification at baseline in PET-negative and PET-positive patients All patients (n=185) 18F-NaF Positive (n=118) 18F-NaF Negative (n=67) P value Agatston Score (AU) 381 [107–892] 541 [245–1130] 136 [55–361] p<0.0001 Calcium Volume (mm3) 358 [131–787] 506 [251–1014] 131 [64–343] p<0.0001 Calcium Mass (mg) 71 [23–155] 100 [48–222] 24 [11–69] p<0.0001 Average Density (mg/mm3) 0.19 [0.17–0.22] 0.20 [0.18–0.23] 0.18 [0.16–0.20] p<0.0001

Conclusions

Coronary 18F-NaF uptake identifies both patients and individual coronary segments with greater disease and more rapid progression of coronary calcification over one year.

Acknowledgement/Funding

AstraZeneca (unrestricted educational grant). British Heart Foundation (CH/09/002, RE/13/3/30183, FS/17/79/33226) Wellcome Trust (WT103782AIA).

1269Dual antiplatelet therapy to inhibit myocardial injury in patients with high-risk coronary artery plaque: a randomized controlled trial

Background

High-risk coronary atherosclerotic plaque is associated with higher plasma troponin concentrations suggesting ongoing myocardial injury that may be a target for dual antiplatelet therapy.

Purpose

To determine whether ticagrelor reduces high-sensitivity troponin I concentrations in patients with established coronary artery disease and high-risk coronary plaque with 18F-fluoride uptake.

Methods

In a randomized double-blind placebo-controlled trial, patients with multivessel coronary artery disease underwent coronary 18F-fluoride positron emission tomography-computed tomography and measurement of high-sensitivity cardiac troponin I and were randomized (1:1) to ticagrelor 90 mg twice daily or matched placebo. The primary endpoint was troponin I concentration at 30 days in patients with increased coronary 18F-fluoride uptake.

Results

In total, 202 patients were randomized and 191 met the pre-specified criteria for inclusion in the primary analysis. In patients with increased coronary 18F-fluoride uptake (n=120/191) there was no evidence that ticagrelor had an effect on plasma troponin concentrationsat 30 days (ratio of geometric means for ticagrelor versusplacebo, 1.11, [95% confidence interval 0.90 to 1.36], p=0.32) (Table 1). Over 1 year, ticagrelor had no effect on troponin concentrations in patients with increased coronary 18F-fluoride uptake (ratio of geometric means, 0.86, 95% confidence interval 0.63 to 1.17, p=0.33).

Table 1 Adjusted Geometric Mean (GSE) Ratio of Geometric Means p-value Ticagrelor Placebo (95% CI) Cardiac troponin I, ng/L (18F-fluoride activity) 3.8 (1.1) 3.4 (1.1) 1.11 (0.90 to 1.36) 0.32 Cardiac Troponin I, ng/L (No 18F-fluoride activity) 2.4 (1.1) 2.3 (1.1) 1.02 (0.80 to 1.31) 0.87 Plasma high-sensitivity cardiac troponin I concentration (ng/L) at 30 days for the per-protocol population.Estimates are back transformed estimates from analysis of log transformed values at 30 days adjusting for age, sex and log transformed baseline troponin. Ratio of geometric means is Ticagrelor divided by Placebo. GSE, geometric standard error.

Conclusions

Dual antiplatelet therapy with ticagrelor does not reduce plasma troponin concentrations in patients with coronary 18F-fluoride uptake. This suggests that subclinical plaque thrombosis does not contribute to ongoing myocardial injury in this setting.

Clinical Trials Study ID: NCT02110303Study ID: NCT02110303

Acknowledgement/Funding

Wellcome Trust Senior Investigator Award WT103782AIA

4087Functional assessment of the myocardium in non-ischaemic cardiomyopathy using manganese-enhanced T1 mapping

Background

Delayed-enhancement magnetic resonance imaging (DEMRI) with gadolinium detects macroscopic myocardial fibrosis, but does not directly assess myocardial function. Manganese, a paramagnetic calcium-analogue, enables direct dynamic assessment myocyte calcium handling and is a potential early marker of myocardial dysfunction. We have previously demonstrated manganese-enhanced MRI (MEMRI) can detect altered calcium-handling in remote remodelling myocardium in a rodent infarct model.

Purpose

To evaluate MEMRI as a marker of altered myocardial calcium handling in patients with non-ischaemic cardiomyopathy (NCT03607669).

Methods

Healthy volunteers (HV, n=20, 13 male, 42±11 years) and patients with hypertrophic (HCM, n=11, 5 male, 57±15 years) or dilated (DCM, n=5, 3 male, 56±14 years) cardiomyopathies underwent both DEMRI and MEMRI. Myocardial T1 was measured for 40 min after intravenous manganese dipyridoxyl diphosphate (Mn-DPDP, 5 μmol/kg) administration. Images were acquired at 3T with T1 imaging performed using Shortened Modified Look-Locker Inversion recovery [Figure A] (WIP #1048 Siemens Healthcare Ltd).

Results

No adverse effects were observed. In HV, the myocardialT1 profile following Mn-DPDP administration demonstrated a rapid initial descent (perfusion phase) followed by a slower, more gradual decrease which continued throughout the 40 min imaging period (mean reduction 25.2%, 283±9ms).

In patients with HCM, T1 values followed a different pattern following Mn-DPDP administration. In areas of focal myocardial fibrosis (defined by DEMRI) there was again a sharp initial shortening of T1 but this was followed by a steady increase towards baseline, which eventually recovered to >40% of its initial value at 40 minutes. In areas of diffuse myocardial fibrosis, the initial shortening in the perfusion phase was followed by a more gradual recovery which then plateaued, remaining stable at 21% of native T1 by 40 min [Figure B]. Hypertrophied non-fibrosed myocardium had higher native T1 than HV (1178±45 vs 1133±36 ms P=0.005) and the rate of T1 reduction following the perfusion phase was slower (P=0.0005), leading to less overall T1 shortening at 40 min (880±40 vs 841±28 ms, P=0.004, [Figure C]).

No patient with DCM had fibrosis by DEMRI. Native T1 was higher than HV (1234±26 vs 1133±36 ms, P<0.0001) and the rate of T1 reduction following the perfusion phase was lower in DCM myocardium (P<0.0001) resulting in less overall T1 shortening at 40 min (914±60 vs 841±28 ms, P=0.0006, [Figure D]).

MEMRI in non-ischaemic cardiomyopathy

Conclusion

MEMRI identifies altered calcium-handling in pathological myocardium of non-ischaemic cardiomyopathy, irrespective of fibrosis by DEMRI. This feasible, safe and novel method of functional myocardial tissue characterisation has exciting potential for future diagnostic, functional and clinical applications.

Acknowledgement/Funding

British Heart Foundation

1337Myocardial extracellular volume in patients with aortic stenosis undergoing valve intervention - A multicentre T1 mapping study

Background

The development of myocardial fibrosis is a key mechanism in the transition from compensated hypertrophy to heart failure in aortic stenosis (AS). Focal and diffuse fibrosis can be quantified using cardiac magnetic resonance (CMR) imaging late gadolinium-enhanced (LGE) and T1 mapping techniques.

Purpose

To assess T1 mapping measures of fibrosis in patients with severe AS referred for aortic valve intervention, and determine their associations with clinical characteristics, disease severity and long-term clinical outcome.

Methods

In this international prospective cohort study, patients with severe AS underwent contrast enhanced CMR with T1 mapping and LGE prior to aortic valve intervention. Image analysis was performed by a single core laboratory and the extracellular volume fraction [ECV%] calculated from T1 mapping images. The presence of LGE was determined visually and quantified using the full-width-at-half-maximum technique.

Results

Four-hundred and forty patients (70±10 years, 59% male) from ten international centres were enrolled. Aortic valve intervention was performed 15 [4 to 58] days following CMR. Within a follow-up of 3.8 [2.8 to 4.6] years, 52 patients died.

ECV% (mean 27.7±3.6%) correlated with increasing age, Society of Thoracic Surgeons Predicted Risk of Mortality score, known coronary artery disease, lower peak aortic-jet velocity, larger left ventricular (LV) mass, lower LV ejection fraction, and presence of LGE (P<0.05 for all). Following adjustment for all demographic and clinical variables, ECV% remained associated with age (P=0.028), LV ejection fraction (P<0.001) and presence of LGE (P=0.035).

Univariable predictors of all-cause mortality included age, male sex, impaired LV ejection fraction and presence of LGE (all P<0.05). A progressive increase in all-cause mortality was seen across tertiles of ECV% (17.3, 31.6 and 52.7 deaths per 1000 patient-years; log-rank test, P=0.009). ECV% was independently associated with all-cause mortality following adjustment for age, sex, impaired LV ejection fraction and presence of LGE (HR per unit increase in ECV: 1.10, 95%, (1.02–1.19), P=0.013).

ECV440 abstract iamge

Conclusion

In patients with severe aortic stenosis scheduled for aortic valve intervention, extracellular volume-based T1 mapping correlates with LV decompensation. ECV% is a strong independent predictor of late all-cause mortality and is a potential therapeutic target.

Incidental finding of large pneumothorax on Cardiac MR scan

BACKGROUND

We believe this is the first case report of a pneumothorax being identified using cardiac magnetic resonance imaging. This case also illustrates the haemodynamic effect a large pneumothorax can have on right ventricular filling in diastole.

CASE PRESENTATION

A 26-year-old attended for an interval follow up Cardiac Magnetic Resonance (CMR) of his thoracic aorta after a thoracic co-arctation repair aged 3. He was found to have an incidental large pneumothorax by the reporting cardiology fellow which was confirmed by the on-call radiologist. The pneumothorax was most notable for its compression of the right ventricle in diastole. Although the patient had worrying features on CMR imaging, he remained clinically stable and a conservative approach to management saw the pneumothorax resolve after a 3 week period.

CONCLUSIONS

Pneumothoraces are important, potentially life threatening conditions. Although very rarely identified on MR imaging, radiographers and reporting doctors should be aware of their key features. This case serves to identify not only the abnormal lung parenchymal features but also the striking compressional effect of the pneumothorax on the right ventricle in diastole. Indeed we believe this is the first case report of a pneumothorax identified on CMR imaging.