Recommendations for cardiovascular magnetic resonance and computed tomography in congenital heart disease: a consensus paper from the CMR/CCT Working Group of the Italian Society of Pediatric Cardiology and the Italian College of Cardiac Radiology endorsed by the Italian Society of Medical and Interventional Radiology (Part II).

Cardiovascular magnetic resonance (CMR) and computed tomography (CCT) are advanced imaging modalities that recently revolutionized the conventional diagnostic approach to congenital heart diseases (CHD), supporting echocardiography and often replacing cardiac catheterization. This is the second of two complementary documents, endorsed by experts from the Working Group of the Italian Society of Pediatric Cardiology and the Italian College of Cardiac Radiology of the Italian Society of Medical and Interventional Radiology, aimed at giving updated indications on the appropriate use of CMR and CCT in different clinical CHD settings, in both pediatrics and adults. In this article, support is also given to radiologists, pediatricians, cardiologists, and cardiac surgeons for indications and appropriateness criteria for CMR and CCT in the most referred CHD, following the proposed new criteria presented and discussed in the first document. This second document also examines the impact of devices and prostheses for CMR and CCT in CHD and additionally presents some indications for CMR and CCT exams when sedation or narcosis is needed.

The impact of native Fallot anatomy on future therapeutic requirements and outcomes at follow-up.

BACKGROUND: In patients with repaired Fallot, subsequent surgical or interventional procedures and adverse cardiac events are frequent. We aimed to evaluate the impact of a simple pre-operative anatomic classification based on the size of the pulmonary valve (PV) annulus and branches on future therapeutic requirements and outcomes. METHOD: This is a single-center retrospective analysis of patients operated for Fallot before the age of 2 years, from January 1990. Pre-operative anatomy, surgical and interventional procedures and adverse events were extrapolated from clinical records. RESULTS: Among the 312 patients, a description of the PV and pulmonary arteries (PAs) native anatomy was known in 239 patients (male:147, 61.5%), which were divided in the following 3 groups: group 1 (65 patients) with normal size of both PV and PAs; group 2 (108 patients) with PV hypoplasia but normal size PAs; group 3 (66 patients) with concomitant hypoplasia of the PV and PAs. During the 12.7 years (IQR 6.7-17) follow-up time, 23% of patients required at least one surgical or interventional procedure. At Kaplan-Meier analysis, there was a significant difference in requirement of future surgical or interventional procedures among the 3 groups (p < 0,001). At multivariate Cox regression analysis, hypoplasia of PV and PAs was an independent predictor of subsequent procedures (HR:3.1,CI:1.06-9.1, p = 0.03). CONCLUSION: Native anatomy in Tetralogy of Fallot patients affects surgical strategy and follow-up. It would be therefore advisable to tailor patient's counseling and follow-up according to native anatomy, rather than following a standardized protocol.

Implications of atrial volumes in surgical corrected Tetralogy of Fallot on clinical adverse events.

BACKGROUND: While left atrial (LA) size has been shown as a strong predictor of cardiovascular diseases in various studies, the role of right atrial (RA) enlargement, especially in the growing population of patients with congenital heart diseases (CHD) is largely unknown. We sought to evaluate (1) RA and LA volumes in patients with repaired Tetralogy of Fallot (TOF) and assess correlations to (2) functional parameters and (3) clinical adverse events. METHODS: 169 patients with repaired TOF were enrolled following a targeted protocol for Cardiovascular magnetic resonance imaging (CMR), Cardiopulmonary exercise tests (CPET), Echocardiography and Measurement of NT-proBNP. Clinical history was assessed at enrollment and during a median Follow-up of 23 months (IQR 9-40). The primary clinical endpoint was a composite of all cause mortality, aborted sudden cardiac death and sustained VT. Prespecified secondary surrogate endpoint included worsening heart failure (NYHA III-IV), non-sustained VT and sustained supraventricular tachycardia. RESULTS: RA Systolic indexed volume (RASVi) correlated with LA Systolic indexed volume (LASVi) (r = 0.59, p < 0.001) and both correlated with the patient age (r = 0.52, p < 0.001; r = 0.59, p < 0.001 respectively). Patients in the upper tertil of RASVi (>58 ml/m2) had higher NT-proBNP levels, longer QRS duration, larger ventricle diameters, higher RV mass and lower peak oxygen uptake. RASVi was associated with the primary composite adverse event at univariate Cox-regression analysis (HR: 1.044, CI: 1.008-1.08, p = 0.01). Bayesian Multivariate model averaging revealed RASVi as predictor of secondary surrogate adverse outcome (HR: 1.06, CI: 1.053-1.068, Pb = 0,889). CONCLUSION: Among patients with repaired TOF, RA dilatation is an independent predictor for adverse clinical events. As such, routine assessment of RA volumes could be useful to further improve decision-making and management of these patients in the future.

Impact of percutaneous pulmonary valve implantation for right ventricular outflow tract dysfunction on exercise recovery kinetics.

The recovery of cardiopulmonary variables from peak exercise in patients with pulmonary stenosis (PS) or regurgitation (PR) is delayed, but the impact of treating PS or PR on exercise recovery kinetics is unknown. 43 patients (median age 14 years) with PS (n = 23) or PR (n = 20) after repair of congenital heart disease underwent successful percutaneous pulmonary valve implantation (PPVI). Cardiopulmonary exercise tests (CPET) were performed both before and within 1 month after PPVI. Apart from peak oxygen uptake (VO2), the constant decay of VO2, CO2 output (VCO2), minute ventilation (VE), and heart rate (HR) and oxygen pulse were calculated for the first minute of recovery as the first-degree slope of a single linear relation. PPVI led to a significant improvement in NYHA functional class in the PS and PR groups (p<0.001 and p=0.0015, respectively). On CPET, peak VO2 improved post-PPVI only in the PS (25.6 ± 6.2 vs. 27.8 ± 7.9 ml/kg/min; p = 0.01) but not PR group (29.0 ± 9.8 vs. 28.6 ± 8.9 ml/kg/min; p = 0.6). However, VO2 slope improved in the PS (0.40 ± 0.23 vs. 0.65 ± 0.27, p < 0.001) as well as in the PR group (0.56 ± 0.37 vs. 0.67 ± 0.37, p = 0.003) as did VCO2 slope (0.39 ± 0.2 vs. 0.55 ± 0.24, p = 0.002 and 0.42 ± 0.33 vs. 0.53 ± 0.35, p = 0.02: for the PS and PR groups, respectively). The VE and HR slopes did not change after PPVI. Despite the lack of improvement in exercise capacity in the PR group, treatment of PS and PR by PPVI induces significant and similar improvements in the ability of recovering from maximal exercise in the 2 groups.

Measurement of in vitro and in vivo stent geometry and deformation by means of 3D imaging and stereo-photogrammetry.

PURPOSE: To quantify variability of in vitro and in vivo measurement of 3D device geometry using 3D and biplanar imaging. METHODS: Comparison of stent reconstruction is reported for in vitro coronary stent deployment (using micro-CT and optical stereo-photogrammetry) and in vivo pulmonary valve stent deformation (using 4DCT and biplanar fluoroscopy). Coronary stent strut length and inter-strut angle were compared in the fully deployed configuration. Local (inter-strut angle) and global (dog-boning ratio) measures of stent deformation were reported during stent deployment. Pulmonary valve stent geometry was assessed throughout the cardiac cycle by reconstruction of stent geometry and measurement of stent diameter. RESULTS: Good agreement was obtained between methods for assessment of coronary stent geometry with maximum disagreement of +/- 0.03 mm (length) and +/- 3 degrees (angle). The stent underwent large, non-uniform, local deformations during balloon inflation, which did not always correlate with changes in stent diameter. Three-dimensional reconstruction of the pulmonary valve stent was feasible for all frames of the fluoroscopy and for 4DCT images, with good correlation between the diameters calculated from the two methods. The largest compression of the stent during the cardiac cycle was 6.98% measured from fluoroscopy and 7.92% from 4DCT, both in the most distal ring. CONCLUSIONS: Quantitative assessment of stent geometry reconstructed from biplanar imaging methods in vitro and in vivo has shown good agreement with geometry reconstructed from 3D techniques. As a result of their short image acquisition time, biplanar methods may have significant advantages in the measurement of dynamic 3D stent deformation.

Geometrical and stress analysis of factors associated with stent fracture after melody percutaneous pulmonary valve implantation.

BACKGROUND: Patients treated with the Melody device (Medtronic) for percutaneous pulmonary valve implantation experience stent fractures in ≈25% of the cases. The aim of this study is to identify the risk factors associated with fracture using 3-dimensional (3D) analyses. METHODS AND RESULTS: In situ 3D shape of the Melody stent was reconstructed from 42 patients using procedural biplane fluoroscopy images, after balloon inflation, at systole and diastole. Four geometric parameters at systole and their variation during balloon deflation and cardiac cycles were measured to describe the 3D strut, cell, section, and stent configuration. Furthermore, patient-specific computer simulations were set up to replicate the history of stent deformations for each patient. Maximum and minimum principal stresses resulting from these analyses were monitored during balloon deflation and cardiac cycle. Univariate logistic regression analyses of 21 geometric parameters and of 4 stress parameters respectively, identified the decreased stent circularity after balloon deflation (odds ratio 0.98; 95% confidence interval, 0.96-0.99; P=0.006) and large compressive stresses during balloon deflation (odds ratio, 0.98; 0.96-0.997; P=0.03), as associated with the risk of fracture. In a multivariable logistic regression model, the 2 covariates identified on univariate analysis (1 geometric and 1 stress) were found to be independently associated with the risk of fracture. The resultant statistical model correctly identified fracture/no fracture in 93% of patients. CONCLUSIONS: Changes in stent section shape after balloon deflation are important variables influencing fracture. This methodology could help design tailored follow-up for patients after percutaneous pulmonary valve implantation.

Percutaneous pulmonary valve replacement after different duration of free pulmonary regurgitation in a porcine model: effects on the right ventricle.

BACKGROUND: Free pulmonary regurgitation (PR) after surgical correction of Tetralogy of Fallot (ToF) with transannular patching can lead to irreversible right ventricular (RV) failure. However, the optimal timing of valve replacement is still debated. METHODS AND RESULTS: Thirty six pigs were included in the study. Twenty one pigs had a bare metal stent placed in the pulmonary annulus inducing free PR and 9 animals served as control. Six animals died prematurely due to procedural complications. The 21 animals were divided into 3 groups with differential duration of PR (1, 2, 3 months, respectively) after which PPVR was performed. After 1 month with competent valve the animals were euthanized. Cardiac magnetic resonance (CMR) and right heart catheterization were performed serially. Free PR led to severe dilation of the RV in all three groups compared to matched controls (p<0.001). Final RV volume after one month with competent pulmonary valve was modeled. Increase in RV volume from baseline to valve replacement (ΔRV) was the only predictor of RV recovery (p<0.001) and increases in ΔRV beyond 120 mL/m2 were predictive of very low probability of recovery. A total of 5 animals did not recover. CONCLUSIONS: Recovery of right ventricular function after free PR by treatment with PPVR was successful in the majority of animals. Increases in RV volume during PR were the only predictor of non-recovery after PPVR and duration of PR did not in itself predict treatment success.

Finite element strategies to satisfy clinical and engineering requirements in the field of percutaneous valves.

Finite element (FE) modelling can be a very resourceful tool in the field of cardiovascular devices. To ensure result reliability, FE models must be validated experimentally against physical data. Their clinical application (e.g., patients' suitability, morphological evaluation) also requires fast simulation process and access to results, while engineering applications need highly accurate results. This study shows how FE models with different mesh discretisations can suit clinical and engineering requirements for studying a novel device designed for percutaneous valve implantation. Following sensitivity analysis and experimental characterisation of the materials, the stent-graft was first studied in a simplified geometry (i.e., compliant cylinder) and validated against in vitro data, and then in a patient-specific implantation site (i.e., distensible right ventricular outflow tract). Different meshing strategies using solid, beam and shell elements were tested. Results showed excellent agreement between computational and experimental data in the simplified implantation site. Beam elements were found to be convenient for clinical applications, providing reliable results in less than one hour in a patient-specific anatomical model. Solid elements remain the FE choice for engineering applications, albeit more computationally expensive (>100 times). This work also showed how information on device mechanical behaviour differs when acquired in a simplified model as opposed to a patient-specific model.

Impact of reduction in right ventricular pressure and/or volume overload by percutaneous pulmonary valve implantation on biventricular response to exercise: an exercise stress real-time CMR study.

AIMS: To assess the impact of relief of pulmonary stenosis (PS) and pulmonary regurgitation (PR) by percutaneous pulmonary valve implantation (PPVI) on biventricular function during exercise stress. METHODS AND RESULTS: Seventeen patients, who underwent PPVI for PS or PR, were included. Magnetic resonance imaging was performed at rest and during supine exercise stress pre- and within 1-month post-PPVI, using a radial k - t SENSE real-time sequence. In patients with PS (n = 9), there was no reserve in right ventricular (RV) ejection fraction (EF) in response to exercise prior to PPVI (48.2 ± 12.1% at rest vs. 48.4 ± 14.8% during exercise, P = 0.87). Post-PPVI, reserve in RVEF in response to exercise was re-established (53.4 ± 15.0% at rest vs. 59.6 ± 17.3% during exercise, P = 0.003) with improvement in left ventricular stroke volume (LVSV) (45.4 ± 6.2 mL/m(2) at rest vs. 52.8 ± 8.8 mL/m(2) during exercise, P = 0.001). In patients with PR prior to PPVI (n = 8), LVSV during exercise increased (43.0 ± 8.5 vs. 54.3 ± 6.6 mL/m(2), P < 0.001) due to reduction in PR fraction during exercise (29.2 ± 5.2 vs. 13.6 ± 6.1%, P < 0.001). After PPVI, LVSV increased from rest to exercise (48.4 ± 8.8 vs. 57.2 ± 8.1 mL/m(2), P < 0.001) due to improved RVEF (45.5 ± 8.3 vs. 50.4 ± 6.9%, P = 0.001). There was a significantly higher increase in LVSV at exercise from pre- to post-PPVI in PS patients than in PR patients (ΔLVSV 8.2 ± 4.1 vs. Δ2.9 ± 4.1 mL/m(2), P = 0.01). The reduction in the RV outflow tract gradient correlated significantly with the improvement in LVSV during exercise (r = -0.73, P < 0.001). CONCLUSION: Percutaneous pulmonary valve implantation in patients with PS leads to restoration of reserve in RVEF during exercise stress. In patients with PR, SV augmentation improves only mildly post-PPVI. Improvement in SV augmentation during exercise stress after PPVI is dependent mainly on afterload reduction.

Virtual and real bench testing of a new percutaneous valve device: a case study.

AIMS: To validate patient-specific computational testing of a second-generation device for percutaneous pulmonary valve implantation (PPVI), against realistic in vitro data. METHODS AND RESULTS: Tests were initially carried out in a simple loading mode, performing a compliance test on a rapid prototyped cylinder. This model was reproduced computationally and validated against the experimental data. A second-generation PPVI stent-graft, with no valve mounted, was then deployed in a simplified cylindrical geometry, measuring its displacement when subjected to a pressure pulse. Experimental and computational measurements were in good agreement. Finally, having selected a patient regarded as unsuitable for first-generation PPVI, but potentially suitable for a second-generation device, the stent-graft was studied in the rapidly prototyped patient-specific right ventricular outflow tract (RVOT). Stent positioning and radial displacements with pulsatile flow were observed in a mock circuit using fluoroscopy imaging. Stent deformation and anchoring were measured both in vitro and computationally. Both tests indicated that the stent was well anchored in the RVOT, especially in the distal position, and its central region was rounded, ensuring, were a valve present, optimal valve function. CONCLUSION: We suggest that an experimentally validated computational model can be used for preclinical device characterisation and patient selection.

Echocardiographic assessment of diastolic biventricular properties in patients operated for severe pulmonary regurgitation and association with exercise capacity.

AIMS: We aimed to assess the impact of surgical pulmonary valve replacement (PVR) for severe pulmonary regurgitation (PR) on biventricular function and its effect on exercise capacity. METHODS AND RESULTS: Seventy-three patients (mean age 23.6±11.5 years, 47 females) underwent surgical PVR for PR. Echocardiogram and magnetic resonance imaging to assess ventricular size and function, and a cardiopulmonary exercise test were performed before, and 1-year post-surgery. Median New York Heart Association class improved from 2 to 1 but peak oxygen uptake (VO2) did not change. Left ventricular (LV) cardiac output increased from 3.2±0.9 to 3.5±0.7 L/min (P=0.003). However, this was not associated with increased trans-mitral velocities (▵E=-0.13, P=0.004; ▵A=0.03, P=0.395), or increased heart rate (-0.002%, P=0.993). Trans-tricuspid rapid right ventricular (RV) filling increased significantly, whereas early diastolic myocardial velocity in RV wall decreased (E velocity: 0.57±0.14-0.65±0.21, P=0.034; and E/e' from 6.7±1.9 to 14.8±7.0, P<0.0001). RV and LV late diastolic velocities and their ratio to early velocities (A, a', E/A, and e'/a') correlated with pre- and/or post-PVR peak VO2. No correlations were found between indexes of systolic function and peak VO2, either before or after surgery. Doppler evidence of restrictive RV physiology resolved after elimination of PR. CONCLUSION: Surgical PVR for PR improves RV filling and increases left ventricular stroke volume, however, this could not be demonstrated by conventional Doppler echocardiography. Diastolic ventricular function was associated with exercise capacity. Because of its load dependency, E/e' ratio failed in assessing diastolic function. Pre-systolic flow in pulmonary trunk in presence of severe PR does not determine intrinsic myocardial stiffness.

Early versus late functional outcome after successful percutaneous pulmonary valve implantation: are the acute effects of altered right ventricular loading all we can expect?

OBJECTIVES: The purpose of this study was to assess the potential of late positive functional remodeling after percutaneous pulmonary valve implantation (PPVI) in right ventricular outflow tract dysfunction. BACKGROUND: PPVI has been shown to impact acutely on biventricular function and exercise performance, but the potential for further late functional remodeling remains unknown. METHODS: Sixty-five patients with sustained hemodynamic effects of PPVI at 1 year were included. Patients were divided into 2 subgroups based on pre-procedural predominant pulmonary stenosis (PS) (n = 35) or predominant pulmonary regurgitation (PR) (n = 30). Data from magnetic resonance imaging and cardiopulmonary exercise testing were compared at 3 time points: before PPVI, within 1 month (early) and at 12 months (late) after PPVI. RESULTS: There was a significant decrease in right ventricle end-diastolic volume early after PPVI in both subgroups of patients. Right ventricle ejection fraction improved early only in the PS group (51 ± 11% vs. 58 ± 11% and 51 ± 12% vs. 50 ± 11%, p < 0.001 for PS, p = 0.13 for PR). Late after intervention, there were no further changes in magnetic resonance parameters in either group (right ventricle ejection fraction, 58 ± 11% in the PS group and 52 ± 11% in the PR group, p = 1.00 and p = 0.13, respectively). In the PS group at cardiopulmonary exercise testing, there was a significant improvement in peak oxygen uptake early (24 ± 8 ml/kg/min vs. 27 ± 9 ml/kg/min, p = 0.008), with no further significant change late (27 ± 9 ml/kg/min, p = 1.00). In the PR group, no significant changes in peak oxygen uptake from early to late could be demonstrated (25 ± 8 ml/kg/min vs. 25 ± 8 ml/kg/min vs. 26 ± 9 ml/kg/min, p = 0.48). CONCLUSIONS: In patients with a sustained hemodynamic result 1 year after PPVI, a prolonged phase of maintained cardiac function is observed. However, there is no evidence for further positive functional remodeling beyond the acute effects of PPVI.

An assessment of the cost of percutaneous pulmonary valve implantation (PPVI) versus surgical pulmonary valve replacement (PVR) in patients with right ventricular outflow tract dysfunction.

BACKGROUND: Percutaneous pulmonary valve implantation (PPVI) using the Melody * transcatheter pulmonary valve is a new procedure introduced in 2000 as a less invasive treatment for right ventricular outflow tract (RVOT) dysfunction. The aim of this new procedure is to restore pulmonary valve competence without the need of open-chest operation. By prolonging the conduit lifespan, it delays surgical pulmonary valve replacement (PVR) and it can therefore potentially reduce the number of open-chest interventions over a patient's lifetime. PPVI has been shown to be feasible and safe and can be performed with a low complication rate. OBJECTIVES AND METHODS: The aim of this study is to assess the cost of PPVI and the cost of surgical pulmonary valve replacement (PVR) in patients with right ventricular outflow tract dysfunction using a cohort simulation model applied to the UK population. RESULTS: The model resulted in an estimate of mean cost per patient of £5,791 when PPVI is unavailable as a treatment option and in an estimate of mean cost per patient of £8,734 when PPVI is available over the 25-year period of analysis. After sensitivity analysis was undertaken the results showed that the mean per patient cost difference in implementing PPVI over 25 years as compared to surgical PVR lies somewhere between £2,041 and £3,913. LIMITATIONS: Given the lack of long-term data on treatment progression, the cost estimates derived here are subject to considerable uncertainty, and extensive sensitivity analysis has been used to counter this. Consequently this study is merely indicative of the levels of cost which can be expected in a cohort of 1,000 patients faced with a choice of treatment with PPVI or surgery. It is not a cost-effectiveness study but it helps place current knowledge on short-term benefits into context. CONCLUSIONS: As this analysis shows PPVI is associated with a relatively small increase in treatment management costs over a long time period. It is left entirely to the reader to value whether this inferred increase in long-term cost is worthwhile given the known short-term benefits and any personal judgement formed over long-term benefit.

Electrical remodeling following percutaneous pulmonary valve implantation.

Sudden cardiac death in congenital heart disease is related to increased right ventricular end-diastolic volume (RVEDV), abnormalities of QRS duration, and QRS, JT, and QT dispersions. Surgical pulmonary valve replacement and percutaneous pulmonary valve implantation (PPVI) decrease RVEDV, but the effects of PPVI on surface electrocardiographic parameters are unknown. PPVI represents a pure model of RV mechanical and electrophysiologic changes after replacement. This prospective study sought to determine the effects of PPVI on surface electrocardiographic parameters: Ninety-nine PPVI procedures in patients with congenital heart disease (23.1 ± 10 years of age) were studied before, after, and 1 year after PPVI with serial electrocardiograms and echocardiogram/magnetic resonance images. Forty-three percent had pulmonary stenosis, 27% pulmonary regurgitation (PR), and 29% mixed lesions. In those with predominantly PR (n = 26), QRS duration decreased significantly (135 ± 27 to 128 ± 29 ms, p = 0.007). However, in the total cohort no significant change in QRS duration at 1 year was observed (137 ± 29 to 134 ± 29 ms). Corrected QT interval and QRS, QT, and JT dispersions significantly decreased at 1 year (p ≤0.001). RVEDV correlated with preprocedure QRS duration (r = 0.34, p <0.002) but there was no correlation after PPVI. In conclusion, this is the first study reporting electrical remodeling after isolated PPVI and it confirms that decreases in QRS duration occur after PPVI in PR, as reported for equivalent surgical cohorts. Further, increased homogeneity of repolarization in combination with improved conduction may decrease arrhythmic events in congenital cardiac patients with pulmonary valvular disease.

Pre-stenting with a bare metal stent before percutaneous pulmonary valve implantation: acute and 1-year outcomes.

OBJECTIVES: To determine the feasibility and safety of pre-stenting with a bare metal stent (BMS) before percutaneous pulmonary valve implantation (PPVI), and to analyse whether this approach improves haemodynamic outcomes and impacts on the incidence of PPVI stent fractures. DESIGN: Retrospective analysis of prospectively collected data. SETTING: Tertiary paediatric and adult congenital heart cardiac centre. PATIENTS AND INTERVENTIONS: 108 consecutive patients with congenital heart disease underwent PPVI between September 2005 and June 2008 (54 with PPVI alone, 54 with BMS pre-stenting before PPVI). RESULTS: There were no significant differences in procedural complication rates. Acutely, there was no difference in haemodynamic outcomes. Serial echocardiography revealed that in the subgroups of 'moderate' (26-40 mm Hg) and 'severe' (>40 mm Hg) right ventricular outflow tract (RVOT) obstruction, patients with pre-stenting showed a tendency towards lower peak RVOT velocities compared to patients after PPVI alone (p=0.01 and p=0.045, respectively). The incidence of PPVI stent fractures was not statistically different between treatment groups at 1 year (PPVI 31% vs BMS+PPVI 18%; p=0.16). However, pre-stenting with BMS was associated with a lower risk of developing PPVI stent fractures (HR 0.35, 95% CI 0.14 to 0.87, p=0.024). The probability of freedom from serious adverse follow-up events (death, device explantation, repeat PPVI) was not statistically different at 1 year (PPVI 92% vs BMS+PPVI 94%; p=0.44). CONCLUSIONS: Pre-stenting with BMS before PPVI is a feasible and safe modification of the established implantation protocol. Pre-stenting is associated with a reduced risk of developing PPVI stent fractures.

Four-dimensional computed tomography: a method of assessing right ventricular outflow tract and pulmonary artery deformations throughout the cardiac cycle.

OBJECTIVE: To characterise 3D deformations of the right ventricular outflow tract (RVOT)/pulmonary arteries (PAs) during the cardiac cycle and estimate the errors of conventional 2D assessments. METHODS: Contrast-enhanced, ECG-gated cardiovascular computed tomography (CT) findings were retrospectively analysed from 12 patients. The acquisition of 3D images over 10 phases of the cardiac cycle created a four-dimensional CT (4DCT) dataset. The datasets were reconstructed and deformation measured at various levels of the RVOT/PAs in both space and time. Section planes were either static or dynamic relative to the motion of the structures. RESULTS: 4DCT enabled measurement and characterisation of in vivo 3D changes of patients' RVOT/PA during the cardiac cycle. The studied patient population showed a wide range of RVOT/PA morphologies, sizes and dynamics that develop late after surgical repair of congenital heart disease. There were also significant differences in the measured cross-sectional areas of the structures between static and dynamic section planes (up to 150%, p<0.05) secondary to large 3D displacements and rotations. CONCLUSIONS: 4DCT imaging data suggest high variability in RVOT/PA dynamics and significant errors in deformation measurements if 3D analysis is not carried out. These findings play an important role for the development of novel percutaneous approaches to pulmonary valve intervention.

How do angioplasty balloons work: a computational study on balloon expansion forces.

AIMS: To investigate the impact of balloon inflation pressure and balloon diameter on the expansion forces exerted in a stenosed vessel (congenital heart disease applications) using computational models. METHODS AND RESULTS: A simplified three-dimensional model of a vessel with a cylindrical stenosis was created. Two low-compliance balloons with different inflation diameters (10 vs. 16 mm) were modelled. Finite element simulations of balloon expansions were performed. To dilate the stenosis from 4 to 10 mm lumen diameter, the large balloon needed less inflation pressure than the small balloon (0.55 vs. 1.00 MPa). Under these circumstances, the large balloon also achieved higher stresses at the stenotic vessel site (5.23 ± 0.10 vs. 3.97 ± 0.04 MPa, p<0.001). When using inflation pressures that led to equal surface stresses of both balloons, the large balloon could exert higher expansion forces onto the stenotic site, achieving higher stresses (5.18 ± 0.09 vs. 3.38 ± 0.01 MPa, p<0.001) and greater lumen diameter (9.73 vs. 8.68 mm). CONCLUSIONS: In a computerised model of balloon dilatation, balloon diameter had a greater impact on the expansion force than inflation pressure. This finding emphasises the importance of choosing an appropriate balloon diameter to achieve optimal haemodynamic outcomes.

Patient-specific reconstructed anatomies and computer simulations are fundamental for selecting medical device treatment: application to a new percutaneous pulmonary valve.

Nowadays, percutaneous pulmonary valve implantation is a successful alternative to surgery for patients requiring treatment of pulmonary valve dysfunction. However, owing to the wide variety of implantation site morphology, size and dynamics, only about 15 per cent of cases are suitable for current devices. In order to increase the number of patients who could benefit from minimally invasive procedures, a new valved stent graft for percutaneous implantation has been designed recently. In this study, patient-specific computational analyses have been applied to investigate the suitability of new device designs, using real data from 62 patients who had undergone surgical pulmonary valve replacement. Magnetic resonance images of these patients before surgery were elaborated using imaging post-processing software to reconstruct the three-dimensional volume of each patient's implantation site. Three stent designs were created and tested in these patient outflow tracts using finite-element simulations: stent graft SG1 resembles the first device tested in animals; stent graft SG2 is a custom device tailored for a specific patient morphology; and stent graft SG3 represents a hypothetical larger device. The three devices showed an implantation success rate of 37 per cent, 42 per cent and 63 per cent, respectively. Using patient-specific simulations, we have shown that a percutaneous approach with these new devices may be possible for many patients who are currently referred for surgery. Furthermore, when the new devices become available, the methodologies described may help clinicians in the decision-making process, by enabling virtual implantation prior to the actual procedure.