Virtual 3D Modeling of Airways in Congenital Heart Defects

Cardiac and pulmonary pathophysiologies are closely interdependent, which makes the management of patients with congenital heart disease (CHD) all the more complex. Pulmonary complications of CHD can be structural due to compression causing airway malacia or atelectasis of the lung. Surgical repair of CHD can also result in structural trauma to the respiratory system, e.g., chylothorax, subglottic stenosis, or diaphragmatic paralysis. Disruption of the Starling forces in the pulmonary vascular system in certain types of CHD lead to alveolar-capillary membrane damage and pulmonary oedema. This in turn results in poorly compliant lungs with a restrictive lung function pattern that can deteriorate to cause hypoxemia. The circulation post single ventricle palliative surgery (the so called "Fontan circulation") poses a unique spectrum of pulmonary pathophysiology with restrictive lung function and a low pulmonary blood flow state that predisposes to thromboembolic complications and plastic bronchitis. As the population of patients surviving post CHD repair increases, the incidence of pulmonary complications has also increased and presents a unique cohort in both the paediatric and adult clinics.

The method of cardiac magnetic resonance (CMR) three-dimensional (3D) image acquisition and post-processing which should be used to create optimal virtual models for 3D printing has not been studied systematically. Patients (n = 19) who had undergone CMR including both 3D balanced steady-state free precession (bSSFP) imaging and contrast-enhanced magnetic resonance angiography (MRA) were retrospectively identified. Post-processing for the creation of virtual 3D models involved using both myocardial (MS) and blood pool (BP) segmentation, resulting in four groups: Group 1-bSSFP/MS, Group 2-bSSFP/BP, Group 3-MRA/MS and Group 4-MRA/BP. The models created were assessed by two raters for overall quality (1-poor; 2-good; 3-excellent) and ability to identify predefined vessels (1-5: superior vena cava, inferior vena cava, main pulmonary artery, ascending aorta and at least one pulmonary vein). A total of 76 virtual models were created from 19 patient CMR datasets. The mean overall quality scores for Raters 1/2 were 1.63 ± 0.50/1.26 ± 0.45 for Group 1, 2.12 ± 0.50/2.26 ± 0.73 for Group 2, 1.74 ± 0.56/1.53 ± 0.61 for Group 3 and 2.26 ± 0.65/2.68 ± 0.48 for Group 4. The numbers of identified vessels for Raters 1/2 were 4.11 ± 1.32/4.05 ± 1.31 for Group 1, 4.90 ± 0.46/4.95 ± 0.23 for Group 2, 4.32 ± 1.00/4.47 ± 0.84 for Group 3 and 4.74 ± 0.56/4.63 ± 0.49 for Group 4. Models created using BP segmentation (Groups 2 and 4) received significantly higher ratings than those created using MS for both overall quality and number of vessels visualized (p < 0.05), regardless of the acquisition technique. There were no significant differences between Groups 1 and 3. The ratings for Raters 1 and 2 had good correlation for overall quality (ICC = 0.63) and excellent correlation for the total number of vessels visualized (ICC = 0.77). The intra-rater reliability was good for Rater A (ICC = 0.65). Three models were successfully printed on desktop 3D printers with good quality and accurate representation of the virtual 3D models. We recommend using BP segmentation with either MRA or bSSFP source datasets to create virtual 3D models for 3D printing. Desktop 3D printers can offer good quality printed models with accurate representation of anatomic detail.

Long-segment tracheal stenosis is rare, life-threatening, difficult, and expensive to treat. Management remains controversial. A multidisciplinary tracheal team was formed in 2000 to deal with a large number of children with airway problems referred for management. We review the effect of that service, comparing the era before and after the establishment of the multidisciplinary tracheal team. From January 1998 through January 2004, 34 patients with long-segment tracheal stenosis (21 patients with cardiovascular anomalies) underwent surgical intervention. Cardiopulmonary bypass was used in all operations. Before the multidisciplinary tracheal team, pericardial patch tracheoplasty with or without an autograft technique was the preferred method of repair. After the multidisciplinary tracheal team, an integrated care plan preferring slide tracheoplasty was initiated, correcting cardiac lesions simultaneously. Before the establishment of the multidisciplinary tracheal team, pericardial patch tracheoplasty was performed in 15 of 19 patients. Twelve patients had a suspended pericardial patch tracheoplasty, 2 (17%) of whom died late after the operation. Of 3 patients who had had a simple unsuspended patch, 2 (67%) died early after the operation. Four patients were operated on with the tracheal autograft technique, 2 (50%) dying early in the postoperative period. After multidisciplinary tracheal team formation, in the era between 2001 and 2004, 15 patients were operated on with slide tracheoplasty, and there were 2 (13%) early postoperative deaths. A significant reduction in cost and duration of stay has been shown both in the intensive care unit and the hospital. Our data suggest that a formalized multidisciplinary team approach and a policy of primary slide tracheoplasty are beneficial in the management of children with long-segment tracheal stenosis.