Chris B Lawton

Quantification of infarct size and myocardium at risk

Aims The aim of this study was to evaluate seven methods for quantifying myocardial oedema [2 standard deviation (SD), 3 SD, 5 SD, full width at half maximum (FWHM), Otsu method, manual thresholding, and manual contouring] from T2-weighted short tau inversion recovery (T2w STIR) and also to reassess these same seven methods for quantifying acute infarct size following ST-segment myocardial infarction (STEMI). This study focuses on test–retest repeatability while assessing inter- and intraobserver variability. T2w STIR and late gadolinium enhancement (LGE) are the most widely used cardiovascular magnetic resonance (CMR) techniques to image oedema and infarction, respectively. However, no consensus exists on the best quantification method to be used to analyse these images. This has potential important implications in the research setting where both myocardial oedema and infarct size are increasingly used and measured as surrogate endpoints in clinical trials. Methods and results Forty patients day 2 following acute reperfused STEMI were scanned for myocardial oedema and infarction (LGE). All patients had a second CMR scan on the same day >6 h apart from the first one. Images were analysed offline by two independent observers using the semi-automated software. Both oedema and LGE were quantified using seven techniques (2 SD, 3 SD, 5 SD, Otsu, FWHM, manual threshold, and manual contouring). Interobserver, intraobserver and test–retest agreement and variability for both infarct size and oedema quantification were assessed. Infarct size and myocardial quantification vary depending on the quantification method used. Overall, manual contouring provided the lowest inter-, intraobserver, and interscan variability for both infarct size and oedema quantification. The FWHM method for infarct size quantification and the Otsu method for myocardial oedema quantification are acceptable alternatives. Conclusions This study determines that, in acute myocardial infarction (MI), manual contouring has the lowest overall variability for quantification of both myocardial oedema and MI when analysed by experienced observers.

Isolated Anomalous Right Coronary Artery From the Pulmonary Artery in Adulthood Anatomical Features and Ischemic Burden

A 51-year-old woman was admitted via the acute medical take after a prolonged episode of sharp central chest pain radiating to her neck and shoulder. The ECG was normal (Figure 1), as were subsequent consecutive troponin I measurements. Additional risk stratification with an exercise tolerance test was performed in consideration of her heavy smoking habit. At 85% of maximal predicted heart rate she developed chest pain and breathlessness with associated 2-mm inferolateral ST-segment depression (Figure 2). Figure 1. Presentation ECG. Figure 2. Exercise ECG with inferolateral ST-segment depression. Her coronary angiogram demonstrated unobstructed vessels but an unexpected anomalous origin of the right coronary artery (RCA) from the pulmonary artery (ARCAPA) with retrograde filling from …

134 Incremental Value of Cardiovascular Magnetic Resonance Imaging in Patients Surviving non Traumatic out of Hospital Cardiac Arrest: A Tertiary UK Centre Experience

Background Non-traumatic out of hospital cardiac arrest (OOHCA) is one of the leading causes of death in western world. Acute coronary syndrome (ACS) is the most common aetiology of OOHCA with a culprit artery lesion identified on invasive angiography. However, 1/3rd of patients with OOHCA have unobstructed coronaries on angiography. Non-invasive tissue characterisation by cardiovascular magnetic resonance (CMR) has the potential to establish the final diagnosis in patients with OOHCA with obstructed coronaries as well as with unobstructed coronary arteries. Methods We retrospectively reviewed the database in our tertiary cardiothoracic centre from October 2009 to November 2013. We identified 54 consecutive patients who were referred for a CMR following an OOHCA. A comprehensive CMR protocol with cine, oedema and scar imaging was used. All scans were done within 6–8 weeks of the index event and was reported by a consultant with >10years of experience in CMR. Results Out of the 54 patients (16 female, age range 21–84 years), 29 (54%) had coronary artery disease, in which the culprit was treated by primary angioplasty and 25 (46%) patients had unobstructed coronaries. Of the latter, 3 had hypertrophic cardiomyopathy, 4 had myocarditis or cardiac sarcoid, 2 had non-ischaemic dilated cardiomyopathy, 2 had LV non-compaction (LVNC) cardiomyopathy, 7 had nonspecific abnormalities and 9 had completely normal CMR scan. In all patients (n = 29) with significant CAD on angiography CMR identified a myocardial infarction (100%). So in total, 40/54 (74%) of OOHCA, a cause was found on CMR. In 11/25 (44%) of OOHCA with unobstructed coronaries a diagnosis was made whereas in 9/25 (36%), a normal CMR was suggestive of a primary arrhythmic cause, thereby guiding further therapy (ICD). Conclusions In adults surviving a non-traumatic OOHCA with unobstructed coronaries on angiogram, CMR could identify the underlying aetiology in the large majority of cases. This has potential implications for treatment and prognosis.

Evaluation of 7 techniques for the quantification of myocardial oedema in STEMI

Background Myocardial oedema is a consequence of injury during ST segment elevation myocardial infarction (STEMI). T2 weighted short tau inversion recovery (T2w STIR) is widely used for oedema assessment on CMR. No consensus exits for which threshold/ contouring method should be used for the quantification of the area of myocardial oedema as a surrogate endpoint in clinical trials. This study investigates the inter- and intra- observer and interscan reproducibility of 7 techniques in use for oedema assessment (2 SD, 3S D, 5S D, FWHM, Otsu, manual threshold and manual contouring). The aim was to determine the most robust method for the quantification of myocardial oedema STEMI. Methods 20 patients day 2 following acute reperfused STEMI were assessed. All patients had 2 CMR scans on the same day at least 6 hours apart. These CMRs included a full short axis stack (8mm slice thickness) of T2w STIR. Images were analysed offline using CMR 42 software (Circle CVI). The endocardium and epicardium were delineated on each slice. For 2, 3 and 5 SD a region of interest was drawn in the remote myocardium, deemed unaffected with the absence of RWMA or LGE. In addition a ROI was drawn in the high signal intensity myocardium in the affected myocardium for the FWHM technique. Manual thresholding was subjective as was manual contouring. The myocardial oedema was expressed as a % of LV. The difference between techniques was assessed using a 1 way ANOVA. The inter-, intra-observer and inter-scan agreement was assessed using the Bland Altman method. Variability was calculated as 1- intraclass correlation coefficient (ICC). Results There is a significant difference in the % of LV with myocardial oedema between all 7 techniques used (p<0.001). 5SD produced the smallest volume of myocardial oedema (8.7 % LV +/- 6.6), FWHM the largest (59.8 % LV +/- 15.9). Manual contouring provided the best inter-, intra- observer and best inter-scan agreement using Bland Altman, with lowest variability (Figure 2). Manual thresholding had the worst agreement. Conclusions This study supports the manual contouring method as the most robust for quantification of myocardial oedema as a surrogate endpoint in clinical trials. The Otsu method provided good agreement between observers

Cardiac magnetic resonance imaging (CMR) characteristics in apical versus non-apical hypertrophic cardiomyopathy (HCM)

Methods Approximately 3,100 CMR scans were reviewed from our CMR registry (Jan 2014 to Mar 2015). comprehensive CMR protocol was used including cines, early and late gadolinium enhancement imaging. 114 consecutive HCM patients were identified. A Asymmetric HCM was defined as: septal to free wall thickness ratio of > 1.3; apical HCM as apical wall thickness of > 15 mm or apical to basal LV wall thicknesses ≥ 1.3-1.5; and concentric HCM as symmetrical hypertrophy of ventricular wall without any regional preferences. Non-apical HCM group (comprising of asymmetric and concentric phenotypes) were compared with apical HCM. Fisher’s exact t-test and unpaired t-test were performed for statistical significance. P-value < 0.05 was statistically significant. Univariate and multivariate logistic regression analyses were performed to determine the CMR predictors of apical HCM. Results The final study sample consisted of 104 patients with HCM with median age 60years (IQR = 54-70) and 70% male, (10 patients excluded due to uncertain diagnosis) 70% non-apical HCM; the remainder 30% apical HCM. In the non-apical HCM group, 5 patients had concentric HCM and the rest had asymmetric HCM. The. The mean maximum LV wall thickness, mean indexed LV mass, mean indexed stroke volume, prevalence of LVOTO and SAM were significantly greater in nonapical group. Table 1 The presence of LGE was high in both groups (>85%) and was not statistically different. The univariate predictors of apical HCM included maximum LV wall thickness, indexed stroke volume, LVOT obstruction whereas in the multivariate model maximum LV wall thickness remained the only significant predictor.

Remote myocardium is also affected in acute myocardial infarction: evidence from advanced CMR relaxometry

Methods 30 patients (mean age 61 ± 10years and 70% males) with STEMI and successful revascularisation by percutaneous coronary intervention were included. Each subject underwent clinical CMR at 1.5 T with T2 and T1 mapping (MOLLI) pre and post contrast (equilibrium contrast technique for extracellular volume (ECV) quantification) within 48hours of presentation. The T2 and pre and post contrast T1 values were evaluated in each of the 16 AHA myocardial segments.

Acute Detection of VENtricular Thrombus by Technologists (ADVENTT study) and the impact of an image interpretation teaching intervention

Background The detection of a ventricular thrombus requires immediate anti-coagulation to prevent the risk for stroke. Prompt diagnosis is of pivotal importance. Excluding a ventricular thrombus is part of the routine assessment of reporting viability studies. We aimed to determine the detection rate of ventricular thrombus by CMR technologists before and after a teaching intervention by CMR doctors.

TWIST-MR-Angiography to aid central venous access in challenging patients. A single centre experience

Background Obtaining adequate venous access is a recurrent problem in patients where long term access is required for the intravenous administration of prolonged antibiotics or parenteral nutrition. Assessment of vein adequacy and patency is clinically important in these patients. Time Resolved Angiography with interleaved stochastic trajectories (TWIST) is a technique that creates a sequential series of multiplanar images during passage of intravenous contrast (Figure 1). TWIST has proven to be very useful in the assessment of vascular haemodynamics such as in arteriovenous malformations (AVMs), fistulas and shunts as well as the investigation of central thoracic veins. Our centre routinely uses TWIST MRA in patients with complex congenital heart disease, particularly for the assessment of complex cardiac connections such as repaired Tetralogy of Fallot, and demonstration of the Fontan circulation.

Aortic flow changes during free breathing exercise, measured with real time MRI

Background Measuring flow with MRI is well established. It is challenging, however, to detect beat-to-beat blood flow response to exercise. We used a new real-time sequence to measure aortic flow during exercise. This phase contrast echo planar imaging (EPI) sequence was previously validated against flow phantoms, and we have recently validated it against the clinical standard sequence in vivo at rest. We set out to establish a methodology of measuring ascending aortic flow during free breathing exercise.

Incremental diagnostic role of cardiac MRI in young-middle aged patients with high-grade atrio-ventricular block

Background Atrio-ventricular (AV) block is a common bradyarrhythmia in the elderly, but is a rare event in young or middle-aged adults, often leading to pacemaker implantation without further investigation, though underlying aetiology influences both treatment strategies and prognosis. Cardiovascular magnetic resonance (CMR) has the potential to identify an underlying aetiology for AV block, over and above transthoracic echocardiogram (TTE), which is offered as the first imaging technique. We sought to assess the diagnostic additive role of CMR in young and middle aged adults (18-60 years) with high-grade AV block and to determine which findings on CMR best predict clinical impact.