Oliver Tann

Systemic to pulmonary collateral blood flow influences early outcomes following the total cavopulmonary connection

Background Systemic to pulmonary collaterals (SPCs) represent an additional and unpredictable source of pulmonary blood flow in patients with single ventricle physiology following bidirectional superior cavopulmonary connection (BCPC). Understanding their influence on patient outcomes has been hampered by uncertainty about the optimal method of quantifying SPC flow. Objective To quantify SPC flow by cardiac magnetic resonance (CMR) prior to total cavopulmonary connection (TCPC) in order to identify preoperative risk factors and determine influence on postoperative outcomes. Design Single centre prospective cohort study. Setting Tertiary referral centre. Patients 65 patients with single ventricle physiology undergoing CMR for preoperative assessment of TCPC completion underwent quantification of SPC flow. Clinical outcomes of 41 patients in whom TCPC was completed were obtained. Main outcome measures Early post-TCPC clinical outcomes associated with SPC flow were assessed, including postoperative chest drainage volume, postoperative chest drainage duration and length of intensive care and hospital stays. Additionally preoperative covariates associated with SPC flow were assessed including age at BCPC and CMR, SpO2 at BCPC and CMR, ventricle type, pulmonary artery (PA) cross-sectional area and PA pulsatility. Different methods of CMR SPC flow quantification were compared. Results Higher SPC flow was associated with increased postoperative chest drain volume (r=0.51, p=0.001), chest drain duration (r=0.43, p=0.005), and intensive care unit (r=0.32, p=0.04) and log-transformed hospital stays (r=0.31, p=0.048). The effect of SPC flow on outcome was independent of fenestration, ventricle type and function. Preoperative covariates associated with SPC flow included age at BCPC (β=−0.34, p=0.008), SpO2 at time of CMR (β=0.34, p=0.004) and branch PA cross-sectional area (β=−0.26, p=0.036), model R2=0.34. Moreover, patients with pulsatile pulmonary blood flow had lower SPC flow than those without (0.8 vs 1.3 l/min/m2 p=0.012). SPC flow calculated by the difference between pulmonary venous return and pulmonary artery flow (l/min/m2) showed greatest association with preoperative covariates and strongest correlation with postoperative outcomes compared with other methods of quantification. Conclusions CMR can provide an effective measurement of SPC flow prior to TCPC. Young age at BCPC, high preoperative oxygen saturation and smaller PAs are associated with increased SPC flow, which may promote increased postoperative pleural drainage and lengthen recovery.

Cardiovascular magnetic resonance findings in repaired anomalous left coronary artery to pulmonary artery connection (ALCAPA)

BackgroundAnomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare coronary artery anomaly. This study shows the role of cardiovascular magnetic resonance (CMR) in assessing young patients following surgical repair of ALCAPA.Methods6 patients, aged 9-21 years, with repaired ALCAPA (2 Tackeuchi method, 4 direct re-implantation) underwent CMR because of clinical suspicion of myocardial ischemia. Imaging used short and long axis cine images (assess ventricular function), late-gadolinium enhancement (LGE) (detect segmental myocardial fibrosis), adenosine stress perfusion (detect reversible ischaemia) and 3D whole-heart imaging (visualize proximal coronary arteries).ResultsThe left ventricular (LV) global systolic function was preserved in all patients (mean LV ejection fraction = 62.7% ± 4.23%). The LV volumes were within the normal ranges, (mean indexed LVEDV = 75.4 ± 3.5 ml/m2, LVESV = 31.6 ± 9.4 ml/m2). In 1 patient, hypokinesia of the anterior segments was visualized. Five patients showed sub-endocardial LGE involving the basal, antero-lateral wall and the anterior papillary muscle. Three patients had areas of reversible ischemia. In these 3, 3D whole-heart MRA showed that the proximal course of the left coronary artery was occluded (confirmed with cardiac catheterisation).ConclusionsCMR is a good, non-invasive, radiation-free investigation in the post-surgical evaluation of ALCAPA. In referred patients we show that basal, antero-lateral sub-endocardial myocardial fibrosis is a characteristic finding. Furthermore, stress adenosine CMR perfusion, can identify reversible ischemia in this group, and was indicative of left coronary artery occlusion.

MRI May Be Sufficient for Noninvasive Assessment of Great Vessel Stents: An In Vitro Comparison of MRI, CT, and Conventional Angiography

OBJECTIVE The purpose of this study was to compare the diagnostic performance of MRI and CT assessment of great vessel stents in an in vitro model. MATERIALS AND METHODS Three contemporary great vessel stent materials (nitinol, platinum-iridium, and stainless steel) were assessed with three luminal conditions: no stenosis, internal stenosis, and external stenosis. Stents of the same material were implanted into an aorta model that was attached to an animal bypass pump with pulsatile flow. Each stent was imaged with conventional angiography as reference standard, 10 different MRI sequences, and CT. The sensitivity and specificity for the identification of stent stenosis was determined and stent lumen measurements compared. RESULTS Of the investigated MRI sequences, three had the highest overall sensitivity and specificity for the identification of stent stenosis in all studied materials: through-plane gradientrecalled echo (GRE) with 75° flip angle (100% and 95%, respectively), in- and through-plane steady-state free precession (SSFP) (99% and 90%) and MR angiography (MRA) with 75° flip angle (93% and 85%). Comparable sensitivity and specificity were achieved with CT (98% and 93%). GRE, SSFP, and MRA sequences tended to underestimate stent lumen diameter in externally nonstenosed stents and overestimate diameter in internally stenosed stents (p < 0.05). CT slightly underestimated external stenoses in all stent types (p < 0.05). CONCLUSION Defined MRI sequences are feasible to assess nitinol, platinum-iridium, and stainless steel great vessel stents with diagnostic performance comparable with CT.

Update of the European Association of Cardiovascular Imaging (EACVI) Core Syllabus for the European Cardiovascular Magnetic Resonance Certification Exam

An updated version of the European Association of Cardiovascular Imaging (EACVI) Core Syllabus for the European Cardiovascular Magnetic Resonance (CMR) Certification Exam is now available online. The syllabus lists key elements of knowledge in CMR. It represents a framework for the development of training curricula and provides expected knowledge-based learning outcomes to the CMR trainees, in particular those intending to demonstrate CMR knowledge in the European CMR exam, a core requirement in the CMR certification process.

Assessment of cardiac time intervals using high temporal resolution real‐time spiral phase contrast with UNFOLDed‐SENSE

To develop a real‐time phase contrast MR sequence with high enough temporal resolution to assess cardiac time intervals.

Utility of adenosine stress perfusion CMR to assess paediatric coronary artery disease

Aims Cardiovascular magnetic resonance (CMR), using adenosine stress perfusion and late-gadolinium enhancement (LGE), is becoming the ‘gold standard’ non-invasive imaging modality in the assessment of adults with coronary artery disease (CAD). However, despite its proved feasibility in paediatric patients, clinical utility has not been demonstrated. Therefore, this study aims to establish the role of adenosine stress perfusion CMR as a screening test in paediatric patients with acquired or congenital CAD. Methods and results A total of 58 paediatric patients underwent 61 consecutive clinically indicated coronary artery assessments for diagnostic and clinical decision-making purposes. The diagnosis was based on X-ray or computed tomography coronary angiography for anatomy, adenosine stress CMR imaging for myocardial perfusion and LGE for tissue characterization. Two studies were aborted because of unwanted side effects of adenosine stress, thus 59 studies were completed in 56 patients [median age 14.1 years (interquartile range 10.9–16.2)]. When compared with coronary anatomical imaging, adenosine stress perfusion CMR performed as follows: sensitivity 100% (95% confidence interval, CI: 71.6–100%), specificity 98% (95% CI: 86.7–99.9%), positive predictive value (PPV) 92.9% (95% CI: 64.2–99.6%), and negative predictive value 100% (95% CI: 89.9–100%). Conclusion In paediatric CAD, adenosine stress perfusion CMR imaging is adequate as an initial, non-invasive screening test for the identification of significant coronary artery lesions, with anatomical imaging used to confirm the extent of the culprit lesion.

Free breathing contrast-enhanced time-resolved magnetic resonance angiography in pediatric and adult congenital heart disease

BackgroundContrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its utility in infants and small children. This study proposes a free-breathing (FB) time resolved MRA (TRA) technique for use in pediatric and adult congenital heart disease (CHD).MethodsA TRA sequence was developed by combining spiral trajectories with sensitivity encoding (SENSE, x4 kx-ky and x2 kz) and partial Fourier (75% in kz). As no temporal data sharing is used, an independent 3D data set was acquired every ~1.3s, with acceptable spatial resolution (~2.3x2.3x2.3mm). The technique was tested during FB over 50 consecutive volumes. Conventional BH-MRA and FB-TRA data was acquired in 45 adults and children with CHD. We calculated quantitative image quality for both sequences. Diagnostic accuracy was assessed in all patients from both sequences. Additionally, vessel measurements were made at the sinotubular junction (N = 43), proximal descending aorta (N = 43), descending aorta at the level of the diaphragm (N = 43), main pulmonary artery (N = 35), left pulmonary artery (N = 35) and the right pulmonary artery (N = 35). Intra and inter observer variability was assessed in a subset of 10 patients.ResultsBH-MRA had significantly higher homogeneity in non-contrast enhancing tissue (coefficient of variance, P <0.0001), signal-to-noise ratio (P <0.0001), contrast-to-noise ratio (P <0.0001) and relative contrast (P = 0.02) compared to the FB-TRA images. However, homogeneity in the vessels was similar in both techniques (P = 0.52) and edge sharpness was significantly (P <0.0001) higher in FB-TRA compared to BH-MRA. BH-MRA provided overall diagnostic accuracy of 82%, and FB-TRA of 87%, with no statistical difference between the two sequences (P = 0.77). Vessel diameter measurements showed excellent agreement between the two techniques (r = 0.98, P <0.05), with no bias (0.0mm, P = 0.71), and clinically acceptable limits of agreement (-2.7 to +2.8mm). Inter and intra observer reproducibility showed good agreement of vessel diameters (r>0.988, P<0.0001), with negligible biases (between -0.2 and +0.1mm) and small limits of agreement (between -2.4 and +2.5mm).ConclusionsWe have described a FB-TRA technique that is shown to enable accurate diagnosis and vessel measures compared to conventional BH-MRA. This simplifies the MRA technique and will enable angiography to be performed in children and adults whom find breath-holding difficult.

3D Morphometric Analysis of the Arterial Switch Operation Using In Vivo MRI Data

The arterial switch operation (ASO) is widely used nowadays as the surgical strategy of choice to repair transposition of the great arteries (TGA). Residual morphological and geometrical abnormalities of the aorta, pulmonary arteries and coronary arteries, however, have not been fully studied in a three‐dimensional (3D) domain. These morphometric complications might have implications on long‐term outcomes of ASO patients, hence the need to explore them in detail and study them with reference to healthy controls of comparable age and body surface area. These anatomical characteristics were examined using 3D patient‐specific anatomical models reconstructed from cardiovascular magnetic resonance (CMR) images of 20 ASO patients (mean age 14.4 ± 2.4 years, 16 males and 4 females) compared with healthy controls (mean age 15.2 ± 2.0 years, 17 males and 3 females). It was found that the aorta, pulmonary arteries and re‐implanted coronary arteries of ASO patients were significantly different morphologically and geometrically to those of healthy controls. In particular, the aortic root was dilated, with abnormal 3D angulation and additional acute angulation of the curvature of the aortic arch in the ASO group compared with controls. This could theoretically impinge on aortic flow profiles and physiological stresses, which can act as a primer for the development of early atherosclerotic disease in the ASO population. Clin. Anat. 27:1212–1222, 2014.

Trends in pediatric cardiovascular magnetic resonance imaging.

Cardiac magnetic resonance (CMR) imaging has significantly evolved over the last decade, becoming an integral part of the contemporary assessment of both congenital and acquired pediatric heart disease. Recent trends show that there is a growing interest in clinical applications and research in this field. An attempt to discuss the evolving technologies, techniques, and applications of CMR in pediatrics is not complete without understanding the current strengths of the modality. CMR complements readily available echocardiography, in many cases information from CMR can remove the need for invasive angiographic catheterization, and in other cases can be used to augment cardiac catheterisation.

Echocardiographic arterial measurements in complex congenital diseases before bidirectional Glenn: comparison with cardiovascular magnetic resonance imaging.

Aims This study sought to investigate diagnostic accuracy of echocardiographic measures of great vessels in patients before bidirectional cavopulmonary connection (BCPC) compared with cardiovascular magnetic resonance (CMR). Methods and results Seventy‐two patients (61% after Norwood operation) undergoing BCPC between 2007 and 2012 were assessed pre‐operatively using echocardiography and CMR. Bland–Altman analysis and correlation coefficients were used for comparison of echocardiography and CMR measurements. Sensitivity, specificity, and positive and negative predictive values were calculated to assess the ability of echocardiography to detect vessel stenosis. Twenty‐four percent of all vessel measurements could not be made by echocardiography due to poor image quality. Acquisition of unsatisfactory images was higher in non‐sedated patients. Although there was a reasonable correlation (0.68–0.90) and low bias (−0.8 to 0.5), there were wide limits of agreement between echocardiography and CMR demonstrating poor agreement. Sensitivity and specificity for pulmonary branches were moderate [sensitivity for right pulmonary artery (RPA) 67%, left pulmonary artery (LPA) 54%, specificity for RPA 65%, LPA 72%] with low levels of accuracy (RPA and LPA 42%). Sensitivity, specificity, and accuracy were better for aorta (82, 86, and 63%, respectively). Conclusion This study demonstrates modest agreement between echocardiographic and CMR measures of vessel diameter and stenosis detection. Approximately a quarter of all vessel segments could not be measured using echocardiography due to poor image quality, which was significantly lower in non‐sedated patients. These findings show that echocardiography cannot substitute CMR for reliable identification of great vessel stenoses in complex patients prior to the BCPC, particularly those with Blalock–Taussig shunts.