Raoul Arnold

Time-resolved three-dimensional magnetic resonance velocity mapping of cardiovascular flow paths in volunteers and patients with Fontan circulation

OBJECTIVE To apply flow-sensitive magnetic resonance imaging for the evaluation of whole-heart flow characteristics in healthy volunteers and patients with Fontan circulation. METHODS Time-resolved three-dimensional magnetic resonance velocity mapping (spatial resolution = 2.5 × 2.8 × 2.8mm(3), temporal resolution = 38.4 ms) was acquired in normal controls and in four Fontan patients with extracardiac total cavopulmonary connection. Data analysis included flow connectivity mapping and flow quantification of arterial and venous blood flow. Haemodynamics in four patients with Fontan circulation were individually evaluated in the aorta, caval veins and left and right pulmonary arteries. RESULTS In four controls, nine distinct flow features were consistently identified with good feature clarity (median = 2 in 80.6% of readings) and image quality (median = 2 in 75.0% of readings). In patients, a marked variability of flow from the caval veins towards the left and right pulmonary arteries (flow ratio = 1.7 ± 0.6, range 1.2-2.6 vs 1.1 ± 0.1 in controls) was found. Increased offset of the caval venous connection resulted in enhanced pulmonary flow asymmetry. Compared with controls, reduced pulsatility in pulmonary arteries (1.4 ± 0.6 vs 4.1 ± 0.6 in controls) and caval veins (1.2 ± 0.4 vs 2.8 ± 1.1 in controls) were observed. Peak flow was reduced in both superior (22 ± 14 mls(-1) vs 76 ± 7 mls(-1) in controls) and inferior vena cava (61 ± 28 mls(-1) vs 187 ± 42 mls(-1) in controls). CONCLUSIONS This feasibility study demonstrated the potential of whole-heart three-dimensional magnetic resonance velocity mapping to reveal overt haemodynamic differences in surgically palliated congenital heart with similar extracardiac cavopulmonary connection geometry. Future studies are warranted to evaluate its diagnostic impact for improved evaluation of the pre- and postoperative status in the individual patient.

Multidirectional flow analysis by cardiovascular magnetic resonance in aneurysm development following repair of aortic coarctation

Aneurysm formation is a life-threatening complication after operative therapy in coarctation. The identification of patients at risk for the development of such secondary pathologies is of high interest and requires a detailed understanding of the link between vascular malformation and altered hemodynamics. The routine morphometric follow-up by magnetic resonance angiography is a well-established technique. However, the intrinsic sensitivity of magnetic resonance (MR) towards motion offers the possibility to additionally investigate hemodynamic consequences of morphological changes of the aorta.We demonstrate two cases of aneurysm formation 13 and 35 years after coarctation surgery based on a Waldhausen repair with a subclavian patch and a Vosschulte repair with a Dacron patch, respectively. Comprehensive flow visualization by cardiovascular MR (CMR) was performed using a flow-sensitive, 3-dimensional, and 3-directional time-resolved gradient echo sequence at 3T. Subsequent analysis included the calculation of a phase contrast MR angiography and color-coded streamline and particle trace 3D visualization. Additional quantitative evaluation provided regional physiological information on blood flow and derived vessel wall parameters such as wall shear stress and oscillatory shear index.The results highlight the individual 3D blood-flow patterns associated with the different vascular pathologies following repair of aortic coarctation. In addition to known factors predisposing for aneurysm formation after surgical repair of coarctation these findings indicate the importance of flow sensitive CMR to follow up hemodynamic changes with respect to the development of vascular disease.

Aortic Hemodynamics in Patients With and Without Repair of Aortic Coarctation In Vivo Analysis by 4D Flow-Sensitive Magnetic Resonance Imaging

Objectives:The purpose of this study was to characterize hemodynamic alterations and flow-derived vessel wall parameters in aortic coarctation (CoA) patients with and without operative repair by time-resolved, 3-dimensional, and 3-directional velocity sensitive, phase-contrast magnetic resonance imaging (4D PC MRI) in comparison with healthy subjects. Methods and Material:Twenty-four patients, 12.5 ± 6.4 years after CoA repair, 4 patients without treatment for CoA, and 19 healthy subjects were examined. The study was approved by the institutional review board and signature of written informed consent was obtained from the participants. Echocardiography was performed in patients before participation. MRI studies were conducted by applying flow-sensitive 4D phase-contrast MRI at either 1.5 T (n = 5 patients) or 3 T (all 19 healthy subjects, n = 23 patients). Blood flow visualization was used to evaluate overall aortic helicity, presence of pronounced or additional localized helix flow, and vortex development. Quantitative evaluation comprised the calculation of regional time-averaged absolute wall shear stress (WSSmag), peak velocities, and oscillatory shear index at 8 locations distributed along the thoracic aorta and additionally at the site of CoA. Inter- and intraobserver variabilities of calculations were determined. Results:Volunteers and patients demonstrated the same amount of overall aortic helicity. In contrast, the number of additional localized helix flow or vortex formation was significantly increased in patients (25/28 patients vs. 5/19 normal controls, Fisher exact test: P < 0.001). Vortices in the orifices of the supra-aortic branches were detected in 64.3% (18/28) of patients but in only 11.8% (2/19) of controls (P < 0.001). Quantitative analyses revealed a significant increase in overall aortic WSSmag (0.44 ± 0.17 N/m2 in patients vs. 0.27 ± 0.08 N/m2 in volunteers, P < 0.005) and a decrease in overall oscillatory shear index. Repeated quantitative analysis showed moderate interobserver and low intraobserver variability. Correlation with echocardiography showed good agreement with MRI which tended to underestimate peak velocities (r = 0.76; Bland-Altman analysis, limits of agreement = −0.57–2.16 m/s, mean = 0.79 m/s). Conclusion:Alterations in aortic hemodynamics after CoA repair are not limited to the specific region of repair, but can be found in the entire aorta. The presented findings highlight the systemic nature of the disease and the need for a systemic diagnostic approach which can be provided by flow-sensitive 4D PC MRI. Furthermore, valuable additional insights on the hemodynamic consequences of coarctation have been shown that may help understanding secondary complications such as restenosis, aneurysm formation, and arterial hypertension.

Prospective electrocardiography-triggered CT angiography of the great thoracic vessels in infants and toddlers with congenital heart disease: Feasibility and image quality

PURPOSE To investigate feasibility and image quality and to calculate radiation dose estimates for computed tomography angiography (CTA) of the great thoracic vessels in infants and toddlers with congenital heart disease (CHD) using end-systolic prospective electrocardiography-triggered sequential dual-source data acquisition. METHODS This study was institutional review board approved; informed consent was obtained. Twenty children (age 1.2±1.1 years) underwent 22 prospective ECG-triggered sequential dual-source CTA examinations (Somatom Definition, Siemens) with tube current (250 mAs/rot) centered at 250 ms past the R-peak in the cardiac cycle (end-systole). Tube voltage was set to 80 kV. Image quality was evaluated by two readers independently using a four-point grading scale (4=excellent, 1=non-diagnostic). Radiation dose estimates were calculated from the dose-length-product (DLP). RESULTS All CT images showed diagnostic image quality (mean score 3.67±0.67, κ=0.85). Stair-step artifacts were present in one and breathing artifacts in 4 patients, with neither impairing diagnostic image quality. Mean heart rate (bpm) was 107.6±12.1 (76-130), mean heart rate variability (bpm) was 2.5±2.0 (1-9). Mean scan length (mm) was 90.7±22.7 (50-134). Mean estimated effective dose was 0.32±0.11 mSv. CONCLUSION Prospective ECG-triggered sequential dual source CTA is feasible in infants and toddlers with CHD, thereby allowing almost motion-free imaging of the great thoracic vessels with the benefit of a low radiation dose.

Chylothorax after surgery on congenital heart disease in newborns and infants -risk factors and efficacy of MCT-diet.

ObjectivesTo analyze risk factors for chylothorax in infants after congenital heart surgery and the efficacy of median chain triglyceride diet (MCT). To develop our therapeutic pathway for the management of chylothorax.Patients and methodsRetrospective review of the institutional surgical database and patient charts including detailed perioperative informations between 1/2000 and 10/2006. Data analyzing with an elimination regression analysis.ResultsTwenty six out of 282 patients had chylothorax (=9.2%). Secondary chest closure, low body weight, small size, longer cardiopulmonary bypass (242 ± 30 versus 129 ± 5 min) and x-clamp times (111 ± 15 versus 62 ± 3 min) were significantly associated with chylothorax (p < 0.05). One patient was cured with total parenteral nutrition (TPN) and one without any treatment. 24 patients received MCT-diet alone, which was successful in 17 patients within 10 days. After conversion to regular alimentation within one week only one chylothorax relapsed. Out of 7 patients primarily not responsive to MCT-diet, 2 were successfully treated by lysis of a caval vein thrombosis, 2 by TPN + pleurodesis + supradiaphragmatic thoracic duct ligation, one by octreotide treatment, and two patients finally died.ConclusionsChylothorax may appear due to injury of the thoracic duct, due to venous or lymphatic congestion, central vein thrombosis, or diffuse injury of mediastinal lymphatic tissue in association with secondary chest closure. Application of MCT alone was effective in 71%, and more invasive treatments like TPN should not be used in primary routine. After resolution of chylothorax, MCT-diet can be converted to regular milk formula within one week and with very low risk of relapse.

Aortic flow patterns in patients with Marfan syndrome assessed by flow-sensitive four-dimensional MRI

To apply time‐resolved three‐dimensional (3D) phase contrast MRI with three‐directional velocity encoding (flow‐sensitive 4D MRI) for the characterization of flow pattern changes in patients with Marfan syndrome (MFS) compared with normal controls.

Aortic wall shear stress in Marfan syndrome

The aim of this study was to quantify changes in thoracic aortic wall shear stress (WSS) in asymptomatic patients with Marfan syndrome (MFS) compared with healthy controls. WSS in the thoracic aorta was quantified based on time‐resolved 3D phase contrast MRI with three‐directional velocity encoding (4D flow MRI, temporal resolution ∼44 ms, spatial resolution ∼2.5 mm) in 24 patients with confirmed MFS (age = 18 ± 12 years) and in 12 older healthy volunteers (age = 25 ± 3 years). Diameters of the thoracic aorta normalized to body surface area were similar for both groups. Peak systolic velocity, absolute WSS, time‐averaged WSS, circumferential WSS, peak systolic WSS, and WSS eccentricity were calculated in eight analysis planes distributed along the thoracic aorta. Plane‐wise comparison revealed significant differences between MFS patients and volunteers in the proximal ascending aorta for peak systolic velocities (1.11 ± 0.23 m/s vs. 1.34 ± 0.18 m/s, P = 0.004) and circumferential WSS (0.14 ± 0.03 N/m2 vs. 0.11 ± 0.02 N/m2, P = 0.007). WSS eccentricity was altered in most of the ascending aorta and proximal arch (P = 0.009–0.020). MFS patients demonstrated segmental differences in peak systolic WSS with a significantly higher WSS at the inner curvature in the proximal ascending aorta and at the anterior part in the more distal ascending aorta (P < 0.01). These findings indicate differences in WSS associated with MFS despite similar aortic dimensions compared to controls. Magn Reson Med, 70:1137–1144, 2013.

Three-dimensional flow characteristics in aortic coarctation and poststenotic dilatation.

The authors present findings from a scientific study in a 36-year-old male patient who was transferred for the evaluation of a restenosis in aortic coarctation that was initially treated by surgical repair. Contrast-enhanced magnetic resonance angiography and comprehensive flow-sensitive 4-dimensional magnetic resonance imaging for the evaluation of 3-dimensional blood flow in the entire thoracic aorta demonstrated distinct flow pattern changes associated with the disease, demonstrating a potential link between altered vascular hemodynamics and the development of vascular disease.

In Vivo 3-Dimensional Flow Connectivity Mapping After Extracardiac Total Cavopulmonary Connection

We present findings in an 18-year-old female patient with a double-inlet single ventricle 12 years after extracardic total cavopulmonary connection (TCPC)1 who also presented with a Waldhausen repair of aortic coarctation. To evaluate arterial and venous anatomy and to assess time-resolved 3-dimensional (3D) blood flow in the venous and pulmonary system, flow-sensitive 4-dimensional magnetic resonance (MR) imaging was performed on a routine 3T MR system (Magnetom TRIO, Siemens, Germany; flip angle=15°, velocity sensitivity=150 cm/s, spatial resolution 2.4×1.8×2.8 mm3, echo time (TE)=2.5 ms, repetition time (TR)=5.0 ms, temporal resolution=40.0 ms, prospective ECG gating, respiratory navigator gating).2 Flow-sensitive 4D MR imaging cannot only be used for the analysis of blood flow but also to derive additional information on vascular geometry by the calculation of a 3D phase contrast (PC) MR angiography. In contrast to conventional contrast-enhanced arterial MR angiography, …

Kawasaki Disease in Germany: A Prospective, Population-based Study Adjusted for Underreporting.

Background: National estimates of Kawasaki disease (KD) incidence often do not include incomplete cases (diagnosed based on only laboratory or echocardiographic criteria), and/or they rely on retrospective case reports and data registries where underreporting is known to be a problem. Methods: We conducted a prospective nationwide KD surveillance study in children younger than 5 years through the hospital-based German Pediatric Surveillance Unit (ESPED). We accounted for underreporting through applying capture–recapture methodology in 2 federal states using hospital discharge records with KD International Statistical Classification of Diseases and Related Health Problems 10th revision code (ie, M30.3). KD diagnosis (complete and incomplete) was established according to the American Heart Association criteria, 2004. Results: Incidence of KD, corrected for underreporting, was 7.2 of 100,000 in children younger than 5 years in Germany. Underreporting to ESPED was estimated at 37%–44%. Overall, 315 validated KD cases were reported. Of the 64 (20%) incomplete cases, 58% (37/64) were detected through echocardiographic findings and 42% (27/64) through laboratory criteria alone. Incomplete cases were younger than complete cases (1.2 vs. 2.0 years, P = 0.0001) and had more coronary aneurysms (43% vs. 11%, P = 0.0001). Conclusions: A substantial number of incomplete KD cases were diagnosed based on the laboratory and echocardiographic criteria only. This was particularly the case in relation to infants younger than 1 year—an age group known to have an increased risk of developing coronary aneurysms. In addition, we found a high rate of underreporting to national Pediatric Surveillance Units. We suggest that improved surveillance and development of better diagnostic tests remain a high priority.