Inter-study reproducibility of left ventricular torsion and torsion rate quantification using MR myocardial feature tracking.

BACKGROUND: To determine the inter-study reproducibility of MR feature tracking (MR-FT) derived left ventricular (LV) torsion and torsion rates for a combined assessment of systolic and diastolic myocardial function. METHODS: Steady-state free precession (SSFP) cine LV short-axis stacks were acquired at 9:00 (Exam A), 9:30 (Exam B), and 14:00 (Exam C) in 16 healthy volunteers at 3 Tesla. SSFP images were analyzed offline using MR-FT to assess rotational displacement in apical and basal slices. Global peak torsion, peak systolic and peak diastolic torsion rates were calculated using different definitions ("twist", "normalized twist" and "circumferential-longitudinal (CL) shear angle"). Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation. RESULTS: The different methods showed good inter-study reproducibility for global peak torsion (intraclass correlation coefficient [ICC]: 0.90-0.92; coefficient of variation [CoV]: 19.0-20.3%) and global peak systolic torsion rate (ICC: 0.82-0.84; CoV: 25.9-29.0%). Conversely, global peak diastolic torsion rate showed little inter-study reproducibility (ICC: 0.34-0.47; CoV: 40.8-45.5%). Global peak torsion as determined by the CL shear angle showed the best inter-study reproducibility (ICC: 0.90;CoV: 19.0%). MR-FT results were not measurably affected by diurnal variation between morning and afternoon scans (CL shear angle: 4.8 ± 1.4°, 4.8 ± 1.5°, and 4.1 ± 1.6° for Exam A, B, and C, respectively; P = 0.21). CONCLUSION: MR-FT based derivation of myocardial peak torsion and peak systolic torsion rate has high inter-study reproducibility as opposed to peak diastolic torsion rate. The CL shear angle was the most reproducible parameter independently of cardiac anatomy and may develop into a robust tool to quantify cardiac rotational mechanics in longitudinal MR-FT patient studies.

Perfusion cardiovascular magnetic resonance and fractional flow reserve in patients with angiographic multi-vessel coronary artery disease.

BACKGROUND: Perfusion cardiovascular magnetic resonance (CMR) and fractional flow reserve (FFR) are emerging as the most accurate tools for the assessment of myocardial ischemia noninvasively or in the catheter laboratory. However, there is limited data comparing CMR and FFR in patients with multi-vessel disease. This study aims to evaluate the correlation between myocardial ischemia detected by CMR with FFR in patients with multivessel coronary disease at angiography. METHODS AND RESULTS: Forty-one patients (123 vascular territories) with angiographic 2- or 3-vessel coronary artery disease (visual stenosis >50 %) underwent high-resolution adenosine stress perfusion CMR at 1.5 T and FFR measurement. An FFR value of <0.75 was considered significant. On a per patient basis, CMR and FFR detected identical ischemic territories in 19 patients (46 %) (mean number of territories 0.7+/-0.7 in both (p = 1.0)). On a per vessel basis, 89 out of 123 territories demonstrated concordance between the CMR and FFR results (72 %). In 34 % of the study population, CMR resulted in fewer ischemic territories than FFR; in 12 % CMR resulted in more ischemic territories than FFR. There was good concordance between the two methods to detect myocardial ischemia on a per-patient (k =0.658 95 % CI 0.383-0.933) level and moderate concordance on a per-vessel (k = 0.453 95 % CI 0.294-0.612) basis. CONCLUSIONS: There is good concordance between perfusion CMR and FFR for the identification of myocardial ischemia in patients with multi-vessel disease. However, some discrepancy remains and at this stage it is unclear whether CMR underestimates or FFR overestimates the number of ischemic segments in multi-vessel disease.

Feasibility of high-resolution quantitative perfusion analysis in patients with heart failure.

BACKGROUND: Cardiac magnetic resonance (CMR) is playing an expanding role in the assessment of patients with heart failure (HF). The assessment of myocardial perfusion status in HF can be challenging due to left ventricular (LV) remodelling and wall thinning, coexistent scar and respiratory artefacts. The aim of this study was to assess the feasibility of quantitative CMR myocardial perfusion analysis in patients with HF. METHODS: A group of 58 patients with heart failure (HF; left ventricular ejection fraction, LVEF ≤ 50%) and 33 patients with normal LVEF (LVEF >50%), referred for suspected coronary artery disease, were studied. All subjects underwent quantitative first-pass stress perfusion imaging using adenosine according to standard acquisition protocols. The feasibility of quantitative perfusion analysis was then assessed using high-resolution, 3 T kt perfusion and voxel-wise Fermi deconvolution. RESULTS: 30/58 (52%) subjects in the HF group had underlying ischaemic aetiology. Perfusion abnormalities were seen amongst patients with ischaemic HF and patients with normal LV function. No regional perfusion defect was observed in the non-ischaemic HF group. Good agreement was found between visual and quantitative analysis across all groups. Absolute stress perfusion rate, myocardial perfusion reserve (MPR) and endocardial-epicardial MPR ratio identified areas with abnormal perfusion in the ischaemic HF group (p = 0.02; p = 0.04; p = 0.02, respectively). In the Normal LV group, MPR and endocardial-epicardial MPR ratio were able to distinguish between normal and abnormal segments (p = 0.04; p = 0.02 respectively). No significant differences of absolute stress perfusion rate or MPR were observed comparing visually normal segments amongst groups. CONCLUSIONS: Our results demonstrate the feasibility of high-resolution voxel-wise perfusion assessment in patients with HF.

Quantification of atrial dynamics using cardiovascular magnetic resonance: inter-study reproducibility.

BACKGROUND: Cardiovascular magnetic resonance (CMR) offers quantification of phasic atrial functions based on volumetric assessment and more recently, on CMR feature tracking (CMR-FT) quantitative strain and strain rate (SR) deformation imaging. Inter-study reproducibility is a key requirement for longitudinal studies but has not been defined for CMR-based quantification of left atrial (LA) and right atrial (RA) dynamics. METHODS: Long-axis 2- and 4-chamber cine images were acquired at 9:00 (Exam A), 9:30 (Exam B) and 14:00 (Exam C) in 16 healthy volunteers. LA and RA reservoir, conduit and contractile booster pump functions were quantified by volumetric indexes as derived from fractional volume changes and by strain and SR as derived from CMR-FT. Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation of atrial function. RESULTS: Inter-study reproducibility was within acceptable limits for all LA and RA volumetric, strain and SR parameters. Inter-study reproducibility was better for volumetric indexes and strain than for SR parameters and better for LA than for RA dynamics. For the LA, reservoir function showed the best reproducibility (intraclass correlation coefficient (ICC) 0.94-0.97, coefficient of variation (CoV) 4.5-8.2%), followed by conduit (ICC 0.78-0.97, CoV 8.2-18.5%) and booster pump function (ICC 0.71-0.95, CoV 18.3-22.7). Similarly, for the RA, reproducibility was best for reservoir function (ICC 0.76-0.96, CoV 7.5-24.0%) followed by conduit (ICC 0.67-0.91, CoV 13.9-35.9) and booster pump function (ICC 0.73-0.90, CoV 19.4-32.3). Atrial dynamics were not measurably affected by diurnal variation between morning and afternoon scans. CONCLUSIONS: Inter-study reproducibility for CMR-based derivation of LA and RA functions is acceptable using either volumetric, strain or SR parameters with LA function showing higher reproducibility than RA function assessment. Amongst the different functional components, reservoir function is most reproducibly assessed by either technique followed by conduit and booster pump function, which needs to be considered in future longitudinal research studies.

Quantitative assessment of magnetic resonance derived myocardial perfusion measurements using advanced techniques: microsphere validation in an explanted pig heart system.

BACKGROUND: Cardiovascular Magnetic Resonance (CMR) myocardial perfusion imaging has the potential to evolve into a method allowing full quantification of myocardial blood flow (MBF) in clinical routine. Multiple quantification pathways have been proposed. However at present it remains unclear which algorithm is the most accurate. An isolated perfused, magnetic resonance (MR) compatible pig heart model allows very accurate titration of MBF and in combination with high-resolution assessment of fluorescently-labeled microspheres represents a near optimal platform for validation. We sought to investigate which algorithm is most suited to quantify myocardial perfusion by CMR at 1.5 and 3 Tesla using state of the art CMR perfusion techniques and quantification algorithms. METHODS: First-pass perfusion CMR was performed in an MR compatible blood perfused pig heart model. We acquired perfusion images at physiological flow ("rest"), reduced flow ("ischaemia") and during adenosine-induced hyperaemia ("hyperaemia") as well as during coronary occlusion. Perfusion CMR was performed at 1.5 Tesla (n = 4 animals) and at 3 Tesla (n = 4 animals). Fluorescently-labeled microspheres and externally controlled coronary blood flow served as reference standards for comparison of different quantification strategies, namely Fermi function deconvolution (Fermi), autoregressive moving average modelling (ARMA), exponential basis deconvolution (Exponential) and B-spline basis deconvolution (B-spline). RESULTS: All CMR derived MBF estimates significantly correlated with microsphere results. The best correlation was achieved with Fermi function deconvolution both at 1.5 Tesla (r = 0.93, p < 0.001) and at 3 Tesla (r = 0.9, p < 0.001). Fermi correlated significantly better with the microspheres than all other methods at 3 Tesla (p < 0.002). B-spline performed worse than Fermi and Exponential at 1.5 Tesla and showed the weakest correlation to microspheres (r = 0.74, p < 0.001). All other comparisons were not significant. At 3 Tesla exponential deconvolution performed worst (r = 0.49, p < 0.001). CONCLUSIONS: CMR derived quantitative blood flow estimates correlate with true myocardial blood flow in a controlled animal model. Amongst the different techniques, Fermi function deconvolution was the most accurate technique at both field strengths. Perfusion CMR based on Fermi function deconvolution may therefore emerge as a useful clinical tool providing accurate quantitative blood flow assessment.

Perfusion phantom: An efficient and reproducible method to simulate myocardial first-pass perfusion measurements with cardiovascular magnetic resonance.

The aim of this article is to describe a novel hardware perfusion phantom that simulates myocardial first-pass perfusion allowing comparisons between different MR techniques and validation of the results against a true gold standard. MR perfusion images were acquired at different myocardial perfusion rates and variable doses of gadolinium and cardiac output. The system proved to be sensitive to controlled variations of myocardial perfusion rate, contrast agent dose, and cardiac output. It produced distinct signal intensity curves for perfusion rates ranging from 1 to 10 mL/mL/min. Quantification of myocardial blood flow by signal deconvolution techniques provided accurate measurements of perfusion. The phantom also proved to be very reproducible between different sessions and different operators. This novel hardware perfusion phantom system allows reliable, reproducible, and efficient simulation of myocardial first-pass MR perfusion. Direct comparison between the results of image-based quantification and reference values of flow and myocardial perfusion will allow development and validation of accurate quantification methods.

Onyx Cast Migration to the Right Ventricle Following Trans-arterial Embolization of a Cranial Dural Arteriovenous Fistula.

We report a case of a middle-aged man who presented to the cardiology clinic with an incidental finding of a hyperdense lesion in the right ventricle (RV). He is an ex-smoker and had a low-dose CT chest as part of a screening program for early lung malignancy. His medical history included a cerebellar hemorrhage in 2021 due to a ruptured dural arteriovenous fistula (dAVF). He was treated as an emergency with trans-arterial embolization using Onyx liquid embolic material (Medtronic, Fridley, MN). The high-flow dAVF embolization was straightforward, with Onyx filling the arteriovenous (AV) shunt and draining the vein. The patient made a good recovery, and routine cerebral digital subtraction angiography (DSA) at three months confirmed the occlusion of the dAVF. Cardiac migration of liquid embolic material used to treat AV shunts is uncommon and probably underreported as it can be asymptomatic, as in this case. Cardiac embolization should be suspected in patients with dense material in the RV and prior treatment with trans-arterial embolization.

Dual inversion-recovery mr imaging sequence for reduced blood signal on late gadolinium-enhanced images of myocardial scar.

PURPOSE: To investigate whether a dual inversion-recovery (IR) prepulse improves scar-to-blood contrast and expert confidence and consistency at late gadolinium-enhanced magnetic resonance (MR) imaging of myocardial scar compared with the standard IR technique at 3.0 T. MATERIALS AND METHODS: The study was approved by the local ethics committee, and all patients provided written informed consent. Twelve men (mean age±standard deviation, 63 years±8) with known myocardial scar underwent MR imaging 10, 20, and 30 minutes after administration of 0.2 mmol/kg gadobutrol with a standard and dual IR sequence. Contrast-to-noise ratios (CNRs) were measured by using region-of-interest analysis, and data were compared with the analysis of variance test. Two experts measured scar size and transmurality, and data were compared with the Student t test and Bland-Altman test. Experts assigned confidence scores for scar detection and transmurality, which were compared with a Wilcoxon matched-pairs signed rank test. RESULTS: Patient data showed improved scar-to-blood CNR for the dual IR technique compared with the standard IR technique at all time points (P<.05). For images obtained 20 minutes after contrast material administration, the dual IR sequence provided higher confidence scores for scar detection and transmurality assessment (P<.05) and resulted in more consistent assessment of scar size and transmurality between readers compared with the IR sequence (P<.05). CONCLUSION: In this preliminary patient study, the dual IR prepulse improved contrast, scar visualization, and expert confidence and reduced expert differences in transmurality and scar size assessment compared with the standard IR technique.

Perfusion cardiovascular magnetic resonance: Comparison of an advanced, high-resolution and a standard sequence.

BACKGROUND: Technical advances in perfusion cardiovascular magnetic resonance (CMR), particularly accelerated data acquisition methods, allow myocardial perfusion imaging with unprecedented spatial resolution. However, it is not clear how implementation of these recent advances affects perfusion image quality, signal and contrast to noise ratios (SNR & CNR) and the occurrence of important artefacts in routine clinical imaging. The objective of this study was therefore to compare a standard and an advanced, high-resolution perfusion sequence. METHODS: A standard ultrafast gradient echo perfusion sequence (st-GrE) was compared with an advanced kt-accelerated steady state free precession sequence (ktBLAST-SSFP) at 1.5 T in healthy volunteers (n = 16) and in patients (n = 32) with known or suspected coronary artery disease. Volunteers were imaged with both sequences at rest and patients underwent stress and rest imaging with either st-GrE or ktBLAST-SSFP prior to X-ray coronary angiography.A blinded expert scored image quality and respiratory artefact severity and also classified patients for the presence of CAD. The extent, transmurality and duration of dark rim artefacts (DRA) as well as signal to noise (SNR) and contrast to noise (CNR) were quantified. RESULTS: In normal hearts ktBLAST-SSFP imaging resulted in significantly improved image quality (p = 0.003), SNR (21.0 ± 6.7 vs. 18.8 ± 6.6; p = 0.009), CNR (15.4 ± 6.1 vs. 14.0 ± 6.0; p = 0.034) and a reduced extent (p = <0.0001) and transmurality (p = 0.0001) of DRA. In patients ktBLAST-SSFP imaging resulted in significantly improved image quality (p = 0.012), and a reduced extent (p = <0.0001), duration (p = 0.004) and transmurality (p = <0.0001) of DRA. Sensitivity and specificity for the detection of CAD against X-ray angiography was comparable with both sequences. There was a non-significant trend towards increased respiratory artefacts with ktBLAST-SSFP in both patients and volunteers. CONCLUSIONS: Advanced high resolution perfusion CMR using a k-t-accelerated SSFP technique results in significantly improved image quality, SNR and CNR and a reduction in the extent and transmurality of DRA compared to a standard sequence. These findings support the use of advanced perfusion sequences for clinical perfusion imaging however further studies exploring whether this results in improved diagnostic accuracy are required.

Inter-study reproducibility of cardiovascular magnetic resonance myocardial feature tracking.

BACKGROUND: Cardiovascular magnetic resonance myocardial feature tracking (CMR-FT) is a recently described method of post processing routine cine acquisitions which aims to provide quantitative measurements of circumferentially and radially directed ventricular wall strain. Inter-study reproducibility is important for serial assessments however has not been defined for CMR-FT. METHODS: 16 healthy volunteers were imaged 3 times within a single day. The first examination was performed at 0900 after fasting and was immediately followed by the second. The third, non-fasting scan, was performed at 1400.CMR-FT measures of segmental and global strain parameters were calculated. Left ventricular (LV) circumferential and radial strain were determined in the short axis orientation (Ecc(SAX) and Err(SAX) respectively). LV and right ventricular longitudinal strain and LV radial strain were determined from the 4-chamber orientation (Ell(LV), Ell(RV), and Err(LAX) respectively). LV volumes and function were also analysed.Inter-study reproducibility and study sample sizes required to demonstrate 5% changes in absolute strain were determined by comparison of the first and second exams. The third exam was used to determine whether diurnal variation affected reproducibility. RESULTS: CMR-FT strain analysis inter-study reproducibility was variable. Global strain assessment was more reproducible than segmental analysis. Overall Ecc(SAX) was the most reproducible measure of strain: coefficient of variation (CV) 38% and 20.3% and intraclass correlation coefficient (ICC) 0.68 (0.55-0.78) and 0.7 (0.32-0.89) for segmental and global analysis respectively. The least reproducible segmental measure was Ell(RV): CV 60% and ICC 0.56 (0.41-0.69) whilst the least reproducible global measure was Err(LAX): CV 33.3% and ICC 0.44 (0-0.77). Variable reproducibility was also reflected in the calculated sample sizes, which ranged from 11 (global Ecc(SAX)) to 156 subjects (segmental Ell(RV)). The reproducibility of LV volumes and function was excellent. There was no diurnal variation in global strain or LV volumetric measurements. CONCLUSIONS: Inter-study reproducibility of CMR-FT varied between different parameters, as summarized above and was better for global rather than segmental analysis. It was not measurably affected by diurnal variation. CMR-FT may have potential for quantitative wall motion analysis with applications in patient management and clinical trials. However, inter-study reproducibility was relatively poor for segmental and long axis analyses of strain, which have yet to be validated, and may benefit from further development.

Design and rationale of the MR-INFORM study: stress perfusion cardiovascular magnetic resonance imaging to guide the management of patients with stable coronary artery disease.

BACKGROUND: In patients with stable coronary artery disease (CAD), decisions regarding revascularisation are primarily driven by the severity and extent of coronary luminal stenoses as determined by invasive coronary angiography. More recently, revascularisation decisions based on invasive fractional flow reserve (FFR) have shown improved event free survival. Cardiovascular magnetic resonance (CMR) perfusion imaging has been shown to be non-inferior to nuclear perfusion imaging in a multi-centre setting and superior in a single centre trial. In addition, it is similar to invasively determined FFR and therefore has the potential to become the non-invasive test of choice to determine need for revascularisation. TRIAL DESIGN: The MR-INFORM study is a prospective, multi-centre, randomised controlled non-inferiority, outcome trial. The objective is to compare the efficacy of two investigative strategies for the management of patients with suspected CAD. Patients presenting with stable angina are randomised into two groups: 1) The FFR-INFORMED group has subsequent management decisions guided by coronary angiography and fractional flow reserve measurements. 2) The MR-INFORMED group has decisions guided by stress perfusion CMR. The primary end-point will be the occurrence of major adverse cardiac events (death, myocardial infarction and repeat revascularisation) at one year. Clinical trials.gov identifier NCT01236807. CONCLUSION: MR INFORM will assess whether an initial strategy of CMR perfusion is non-inferior to invasive angiography supplemented by FFR measurements to guide the management of patients with stable coronary artery disease. Non-inferiority of CMR perfusion imaging to the current invasive reference standard (FFR) would establish CMR perfusion imaging as an attractive non-invasive alternative to current diagnostic pathways.

ST-elevation myocardial infarction in a young patient with Duchenne's muscular dystrophy: a case report.

Background: Duchenne's muscular dystrophy (DMD) is an X-linked muscular disease which is caused by the absence of dystrophin. This results in the death of muscle cells and cardiomyocytes and consequent substitution by fat and fibrous tissue. The clinical translation of this is muscle weakness and cardiomyopathy. We report on the case of a young patient with dilated cardiomyopathy on a background of DMD who developed ST-elevation myocardial infarction (STEMI). Case summary: A 19-year-old male patient with DMD, known dilated cardiomyopathy, and no risk factors for ischaemic heart disease presented with central crushing chest pain. His electrocardiogram revealed anterior ST elevation. His angiogram revealed distally occluded left anterior descending and second diagonal branch with no evidence of underlying coronary artery disease. He was treated with balloon angioplasty. An echocardiogram raised the suspicion of a left ventricular thrombus, and the mechanism of STEMI was felt to be embolism from the left ventricular thrombus on a background of dilated cardiomyopathy in the context of DMD. The patient was treated with anticoagulants (warfarin). On a repeat echocardiogram a few months later, the thrombus had resolved. At 3 years of follow-up, the patient did not present any more embolic events. Discussion: To our knowledge, this is the first case of STEMI secondary to thrombotic coronary occlusion that has been described in a patient with DMD. This case highlights an unusual complication of DMD. Based on this case, we discuss the dilemmas in the management and follow-up of this complex patient population.

Impact of an abdominal belt on breathing patterns and scan efficiency in whole-heart coronary magnetic resonance angiography: comparison between the UK and Japan.

BACKGROUND: Long acquisition times and complex breathing motion patterns lead to suboptimal image quality in whole heart coronary magnetic resonance angiography (WHCMRA). To overcome this problem, an abdominal belt (BELT) has been suggested by a Japanese group. However, its applicability in a Western population has not been previously demonstrated. The purpose of this study was to investigate 1) how the application of a BELT alters breathing patterns during MR scanning and 2) whether the BELT has a similar impact on breathing patterns in UK and Japanese patient populations. METHODS: 30 patients (15 in the UK and 15 in Japan) were studied at 1.5 Tesla (Achieva, Philips Healthcare). Real time navigator positioned through the right diaphragm in cranio-caudal direction was evaluated. Measurements were performed in the supine position with free breathing for one minute before and after a tight-fitting BELT was positioned around the patient's abdomen. End expiratory position (EEP), end inspiratory position (EIP), end expiratory duration (EED) for the right diaphragm and respiratory rate (RR) were obtained. Scan efficiency (SE) was calculated as follows; SE = [the duration within 5 mm gating window per minutes]/[RR interval]/[heart rate]. RESULTS: Height and weight of UK patients were significantly larger than in the Japanese population (171.2 ± 10.8 cm vs 160.8 ± 8.5 cm, p = 0.007; 80.5 ± 22.5 kg vs 59.9 ± 7.7 kg, p = 0.004). After fitting the BELT, EEP-EIP decreased (all patients, 14.9 ± 6.2 mm to 9.4 ± 3.8 mm, p < 0.001; UK patients, 15.9 ± 6.0 mm to 9.7 ± 3.1 mm, p = 0.001; Japanese patients, 14.0 ± 6.4 mm to 9.1 ± 4.6 mm, p = 0.001), RR increased (all patients, 10.0 ± 3.1 min(-1) to 11.2 ± 3.0 min(-1), p = 0.003; UK patients, 9.5 ± 2.8 min(-1) to 10.7 ± 2.8 min(-1), p = 0.038; Japanese patients, 10.4 ± 3.5 min(-1) to 11.8 ± 3.1 min(-1), p = 0.036), and calculated scan efficiency increased (all patients, 45.3 ± 11.4% to 58.6 ± 17.0%, p < 0.001; UK patients, 44.2 ± 10.8% to 55.7 ± 16.7%, p = 0.004; Japanese patients, 46.3 ± 32.2% to 61.0 ± 17.6%, p = 0.001). No significant differences were found between UK and Japanese patients before and after administration of the BELT. CONCLUSION: Using a BELT significantly increases whole-heart coronary MR angiography scan efficiency in both UK and Japanese patients.

Development of a universal dual-bolus injection scheme for the quantitative assessment of myocardial perfusion cardiovascular magnetic resonance.

BACKGROUND: The dual-bolus protocol enables accurate quantification of myocardial blood flow (MBF) by first-pass perfusion cardiovascular magnetic resonance (CMR). However, despite the advantages and increasing demand for the dual-bolus method for accurate quantification of MBF, thus far, it has not been widely used in the field of quantitative perfusion CMR. The main reasons for this are that the setup for the dual-bolus method is complex and requires a state-of-the-art injector and there is also a lack of post processing software. As a solution to one of these problems, we have devised a universal dual-bolus injection scheme for use in a clinical setting. The purpose of this study is to show the setup and feasibility of the universal dual-bolus injection scheme. METHODS: The universal dual-bolus injection scheme was tested using multiple combinations of different contrast agents, contrast agent dose, power injectors, perfusion sequences, and CMR scanners. This included 3 different contrast agents (Gd-DO3A-butrol, Gd-DTPA and Gd-DOTA), 4 different doses (0.025 mmol/kg, 0.05 mmol/kg, 0.075 mmol/kg and 0.1 mmol/kg), 2 different types of injectors (with and without "pause" function), 5 different sequences (turbo field echo (TFE), balanced TFE, k-space and time (k-t) accelerated TFE, k-t accelerated balanced TFE, turbo fast low-angle shot) and 3 different CMR scanners from 2 different manufacturers. The relation between the time width of dilute contrast agent bolus curve and cardiac output was obtained to determine the optimal predefined pause duration between dilute and neat contrast agent injection. RESULTS: 161 dual-bolus perfusion scans were performed. Three non-injector-related technical errors were observed (1.9%). No injector-related errors were observed. The dual-bolus scheme worked well in all the combinations of parameters if the optimal predefined pause was used. Linear regression analysis showed that the optimal duration for the predefined pause is 25s to separate the dilute and neat contrast agent bolus curves if 0.1 mmol/kg dose of Gd-DO3A-butrol is used. CONCLUSION: The universal dual-bolus injection scheme does not require sophisticated double-head power injector function and is a feasible technique to obtain reasonable arterial input function curves for absolute MBF quantification.

Cardiac magnetic resonance imaging to guide complex revascularization in stable coronary artery disease.

Coronary revascularization has been a cornerstone of the management of patients with coronary artery disease (CAD) for many years. Both coronary artery bypass grafting and percutaneous coronary intervention have evolved and improved over time such that increasingly complex and challenging cases can now be tackled with a high degree of procedural success. In parallel with this, there have been major advances in medical therapy for CAD. Consequently, one of the main decisions in the contemporary management of stable CAD concerns which patients and lesions should be revascularized. This is particularly true for patients with complex disease such as multivessel disease or those with left ventricular impairment. Such patients will potentially benefit the most but are also at highest risk of complications and it is therefore important that they are carefully selected. Recent major trials have challenged the conventional view that consideration of coronary anatomy alone is sufficient in this decision-making. An accumulating body of evidence underscores the importance of functional investigations when assessing the potential benefits of revascularization in these complex patients. In parallel with these developments, cardiac magnetic resonance (CMR) has matured into a robust technology that is able to measure many of the parameters required to accurately characterize these patients. This article will review the importance of myocardial viability and ischaemia when selecting patients with stable CAD for revascularization, the use of CMR imaging for assessing this pathophysiology, and planning complex revascularization, and finally give an outlook on how CMR may help address some important outstanding clinical questions.

NICE diagnostic heart failure pathway: screening referrals identifies patients better served by community-based management.

AIMS: Evaluate whether UK National Institute for Health & Care Excellence (NICE) chronic heart failure (HF) guidelines can be safely and effectively refined through specialist referral management. METHODS AND RESULTS: All referrals to a UK centre 1/3/2019-30/5/2019 and 1/6/2020-31/7/2020 were reviewed by HF specialists. Patients were triaged to specialist assessment in HF clinic, according to the NICE HF diagnostic pathway [urgency based on N-terminal pro brain natriuretic peptide (NTproBNP) levels], or the referrer given remote Advice & Guidance (A&G), to aid primary care management. Standardized triage criteria for recommending primary care management were (i) presentation inconsistent with HF, (ii) competing comorbidity/frailty meant specialist assessment in clinic not in patient's best interests, (iii) recent assessment for same condition, or (iv) patient had known HF. Following triage patients managed in the primary care were categorized as low or high risk of adverse outcomes. Outcome measures were 90 day all-cause and HF hospital admission and mortality rates. Four hundred and eighty-six patients had the median age of 80 (74-86) years, and 253 (52%) were male. Two hundred and six (42%) had NTproBNP > 2000 pg/mL. Primary care management was recommended for 128 patients (26%): 105 (22%) A&G alone and 23 input from community HF nurse specialists. Primary care management was recommended due to the following: presentation inconsistent with HF 53 (42%), more important competing comorbidity/frailty 35 (27%), recent assessment 17 (13%), and known HF 23 (18%). Patients managed in primary care had higher rates of all-cause hospitalization (30% vs. 19%; P = 0.018) and death (7% vs. 2%; P = 0.0054) than those seen in HF clinic. Of those managed in primary care, 50 (39%) were determined to be at low risk and 78 (61%) at high risk. High-risk patients were older (87 vs. 80 years; P = 0.0026), had much higher NTproBNP (2666 vs. 697 pg/mL; P < 0.0001), and were managed in the primary care due to severe comorbidity (45%) or known HF (31%). They had extremely high rates of adverse outcomes: 35 all-cause hospitalization (45%), 12 HF hospitalization (15%), and 9 deaths (12%). Low-risk patients were usually felt not to have HF (86%) and confirmed to have low rates of adverse outcomes: three all-cause hospitalizations (6%; P < 0.0001 compared with high risk) and zero HF hospitalization (P = 0.0033) or death (P = <0.012). CONCLUSIONS: Incorporating specialist referral management into NICE HF diagnostic pathway reduces the demand on HF clinics and may improve the patient experience by facilitating community care. However, many of the patients identified for primary care management are at very high risk of adverse outcomes in the short term and are frequently hospitalized. Urgent implementation of alternative pathways and community-based care packages in parallel for these high-risk patients is extremely important.

An isolated perfused pig heart model for the development, validation and translation of novel cardiovascular magnetic resonance techniques.

BACKGROUND: Novel cardiovascular magnetic resonance (CMR) techniques and imaging biomarkers are often validated in small animal models or empirically in patients. Direct translation of small animal CMR protocols to humans is rarely possible, while validation in humans is often difficult, slow and occasionally not possible due to ethical considerations. The aim of this study is to overcome these limitations by introducing an MR-compatible, free beating, blood-perfused, isolated pig heart model for the development of novel CMR methodology. METHODS: 6 hearts were perfused outside of the MR environment to establish preparation stability. Coronary perfusion pressure (CPP), coronary blood flow (CBF), left ventricular pressure (LVP), arterial blood gas and electrolyte composition were monitored over 4 hours. Further hearts were perfused within 3T (n = 3) and 1.5T (n = 3) clinical MR scanners, and characterised using functional (CINE), perfusion and late gadolinium enhancement (LGE) imaging. Perfusion imaging was performed globally and selectively for the right (RCA) and left coronary artery (LCA). In one heart the RCA perfusion territory was determined and compared to infarct size after coronary occlusion. RESULTS: All physiological parameters measured remained stable and within normal ranges. The model proved amenable to CMR at both field strengths using typical clinical acquisitions. There was good agreement between the RCA perfusion territory measured by selective first pass perfusion and LGE after coronary occlusion (37% versus 36% of the LV respectively). CONCLUSIONS: This flexible model allows imaging of cardiac function in a controllable, beating, human-sized heart using clinical MR systems. It should aid further development, validation and clinical translation of novel CMR methodologies, and imaging sequences.

Characteristics and outcomes of patients with suspected heart failure referred in line with National Institute for Health and Care Excellence guidance.

OBJECTIVE: To describe the population, heart failure (HF) diagnosis rate, and 1-year hospitalisation and mortality of patients with suspected HF and elevated N-terminal pro B-type natriuretic peptide (NTproBNP) investigated according to UK National Institute for Health and Care Excellence (NICE) guidelines. METHODS: NICE recommends patients with suspected HF, based on clinical presentation and elevated NTproBNP, are referred for specialist assessment and echocardiography. Patients should be seen within 2 weeks when NTproBNP is >2000 pg/mL (2-week pathway: 2WP) or within 6 weeks when NTproBNP is 400-2000 pg/mL (6-week pathway: 6WP). This is a retrospective, multicentre, observational study of consecutive patients with suspected HF referred from primary care between 2014 and 2016 to dedicated secondary care HF clinics based on the NICE 2WP and 6WP. Data were obtained from hospital records and episode statistics. Mortality and hospitalisation rates were calculated 1 year from NTproBNP measurement. RESULTS: 1271 patients (median age 80; IQR 73-85) were assessed, 680 (53%) of whom were female. 667 (53%) were referred on the 2WP and 604 (47%) on the 6WP. 698 (55%) were diagnosed with HF (369 HF with reduced ejection fraction) and 566 (45%) as not HF (NHF). 1-year mortality was 10% (n=129) and hospitalisation was 33% (n=413). Patients on the 2WP had higher mortality and hospitalisation rates than those on the 6WP, 14% vs 6% (p<0.001) and 38% vs 27% (p<0.001), respectively. All-cause mortality (11% vs 9%; p=0.306) and hospitalisation rates (35% vs 29%; p=0.128) did not differ between HF and NHF patients, respectively. CONCLUSIONS: Outcomes using the NICE approach of short waiting time targets for specialist assessment of patients with suspected HF and raised NTproBNP are not known. The model identifies an elderly population a high proportion of whom have HF. Irrespective of diagnosis, patients have high rates of adverse outcomes. These contemporary real-world data provide a platform for discussions with patients and shaping HF services.

Distractions in the cardiac catheterisation laboratory: impact for cardiologists and patient safety.

OBJECTIVE: To understand human factors (HF) contributing to disturbances during invasive cardiac procedures, including frequency and nature of distractions, and assessment of operator workload. METHODS: Single centre prospective observational evaluation of 194 cardiac procedures in three adult cardiac catheterisation laboratories over 6 weeks. A proforma including frequency, nature, magnitude and level of procedural risk at the time of each distraction/interruption was completed for each case. The primary operator completed a National Aeronautical and Space Administration (NASA) task load questionnaire rating mental/physical effort, level of frustration, time-urgency, and overall effort and performance. RESULTS: 264 distractions occurred in 106 (55%) out of 194 procedures observed; 80% were not relevant to the case being undertaken; 14% were urgent including discussions of potential ST-elevation myocardial infarction requiring emergency angioplasty. In procedures where distractions were observed, frequency per case ranged from 1 to 16 (mean 2.5, SD ±2.2); 43 were documented during high-risk stages of the procedure. Operator rating of NASA task load parameters demonstrated higher levels of mental and physical workload and effort during cases in which distractions occurred. CONCLUSIONS: In this first description of HF in adult cardiac catheter laboratories, we found that fewer than half of all procedures were completed without interruption/distraction. The majority were unnecessary and without relation to the case or list. We propose the introduction of a 'sterile cockpit' environment within catheter laboratories, as adapted from aviation and used in surgical operating theatres, to minimise non-emergent interruptions and disturbances, to improve operator conditions and overall patient safety.

Point-of-care platelet function assays demonstrate reduced responsiveness to clopidogrel, but not aspirin, in patients with Drug-Eluting Stent Thrombosis whilst on dual antiplatelet therapy.

BACKGROUND: To test the hypothesis that point-of-care assays of platelet reactivity would demonstrate reduced response to antiplatelet therapy in patients who experienced Drug Eluting Stent (DES) ST whilst on dual antiplatelet therapy compared to matched DES controls. Whilst the aetiology of stent thrombosis (ST) is multifactorial there is increasing evidence from laboratory-based assays that hyporesponsiveness to antiplatelet therapy is a factor in some cases. METHODS: From 3004 PCI patients, seven survivors of DES ST whilst on dual antiplatelet therapy were identified and each matched with two patients without ST. Analysis was performed using (a) short Thrombelastogram PlateletMappingtrade mark (TEG) and (b) VerifyNow Aspirin and P2Y12 assays. TEG analysis was performed using the Area Under the Curve at 15 minutes (AUC15) as previously described. RESULTS: There were no differences in responses to aspirin. There was significantly greater platelet reactivity on clopidogrel in the ST group using the Accumetrics P2Y12 assay (183 +/- 51 vs. 108 +/- 31, p = 0.02) and a trend towards greater reactivity using TEG AUC15 (910 +/- 328 vs. 618 +/- 129, p = 0.07). 57% of the ST group by TEG and 43% of the ST cases by Accumetrics PRU had results > two standard deviations above the expected mean in the control group. CONCLUSION: This study demonstrates reduced platelet response to clopidogrel in some patients with DES ST compared to matched controls. The availability of point-of-care assays that can detect these responses raises the possibility of prospectively identifying DES patients at risk of ST and manipulating their subsequent risk.