Quantification and Analysis of the Geometric Parameters of the Total Cavo Pulmonary Connection Using a Skeletonization Approach

The Fontan repair is a three-stage palliative surgical procedure for single ventricle congenital heart diseases, ultimately resulting in the right heart bypass. This is accomplished by routing the systemic venous return directly to the lungs. Although this procedure reduces the mortality rate, its long-term outcome is still considered far from optimal. Over the years several modifications have been suggested, ultimately leading to the total cavopulmonary connection (TCPC), which is the current procedure of choice. A better understanding of the hemodynamics in the TCPC is critical for further optimization of the TCPC design and surgical planning, which may lead to improved surgical outcome. Recent experimental and numerical studies have focused on characterizing the fluid dynamics of the TCPC but to date no study has attempted to relate the geometry of the TCPC anatomies with their hemodynamic parameters. The present study therefore proposes to quantify the complex geometrical characteristics of patient-specific TCPC anatomies and correlate these characteristics with their hemodynamic efficiency. A technique using skeletonization approach is thus developed to achieve this goal. The centerline approximation of the TCPC geometry is used to extract main geometric parameters such as vessel area, curvature and offset. The developed methodology is then applied to characterize the shape of various TCPC templates including extra-cardiac (EC) and intra-atrial (IA) TCPCs, TCPCs with bilateral Superior Vena Cavae and geometries before the third stage. The obtained geometric parameters are then related to the TCPC hemodynamics, particularly to the power loss.M.S.Committee Chair: Yoganathan Ajit; Committee Member: Oshinski, John; Committee Member: Sharma, Shiv

CARDIOVASCULAR Quantitative Analysis of Extracardiac Versus Intraatrial Fontan Anatomic Geometries

Background. There exists large geometric variability among total cavopulmonary connections (TCPC) because of the patient-specific anatomies and the chosen surgical procedure. In this study we present quantitative comparison of the geometric characteristics of the extracardiac and intraatrial Fontan anatomies, the two commonly used TCPC procedures. Methods. A method of centerline approximation of the three-dimensional geometries (skeletonization) was used to quantify the TCPC geometric parameters such as vessel areas, curvature, and collinearity. The TCPC anatomies of 26 patients, 13 extracardiac and 13 intraatrial, were analyzed in this study. Results. There was no significant difference in the vessel dimensions between extracardiac and intraatrial TCPCs, with the overall magnitudes agreeing well with that seen in normal children except for the inferior vena cava. Intraatrial baffles had significant fluctuations in cross-sectional area along the length of the baffle as opposed to extracardiacs (p < 0.05). Patients with hypoplastic left heart syndrome had significant narrowing of the left pulmonary artery (p < 0.05), suggesting a possible physical constriction from the reconstructed aorta. Conclusions. This study benchmarks the anatomic variability of patient-specific TCPCs. Intraatrial Fontan geometries have significant difference in the area variations across the vessel length compared with the extracardiac geometry. Also, patients with hypoplastic left heart are at a higher risk of left pulmonary artery narrowing

Hemodynamic Energy Dissipation in the Cardiovascular System: Generalized Theoretical Analysis on Disease States

Background We present a fundamental theoretical framework for analysis of energy dissipation in any component of the circulatory system and formulate the full energy budget for both venous and arterial circulations. New indices allowing disease-specific subject-to-subject comparisons and disease-to-disease hemodynamic evaluation (quantifying the hemodynamic severity of one vascular disease type to the other) are presented based on this formalism. Methods and ResultsDimensional analysis of energy dissipation rate with respect to the human circulation shows that the rate of energy dissipation is inversely proportional to the square of the patient body surface area and directly proportional to the cube of cardiac output. This result verified the established formulae for energy loss in aortic stenosis that was solely derived through empirical clinical experience. Three new indices are introduced to evaluate more complex disease states: (1) circulation energy dissipation index (CEDI), (2) aortic valve energy dissipation index (AV-EDI), and (3) total cavopulmonary connection energy dissipation index (TCPCEDI). CEDI is based on the full energy budget of the circulation and is the proper measure of the work performed by the ventricle relative to the net energy spent in overcoming frictional forces. It is shown to be 4.01 ± 0.16 for healthy individuals and above 7.0 for patients with severe aortic stenosis. Application of CEDI index on single-ventricle venous physiology reveals that the surgically created Fontan circulation, which is indeed palliative, progressively degrades in hemodynamic efficiency with growth (p Conclusions Energy dissipation in the human circulation has been analyzed theoretically to derive the proper scaling (indexing) factor. CEDI, AV-EDI, and TCPC-EDI are proper measures of the dissipative characteristics of the circulatory system, aortic valve, and the Fontan connection, respectively

Fontan Hemodynamics: Importance of Pulmonary Artery Diameter

We quantify the geometric and hemodynamic characteristics of extracardiac and lateral tunnel Fontan surgical options and correlate certain anatomic characteristics with their hemodynamic efficiency and patient cardiac index. The study was conducted retrospectively on 22 patients undergoing Fontan operations (11 extracardiac and 11 lateral tunnel operations). Total cavopulmonary connection geometric parameters such as vessel areas, curvature, and offsets were quantified using a skeletonization method. Energy loss at the total cavopulmonary connection junction was available from previous in vitro experiments and computational fluid dynamic simulations for 5 and 9 patients, respectively. Cardiac index data were available for all patients. There was no significant difference in the mean and minimum cross-sectional vessel areas of the pulmonary artery between the extracardiac and lateral tunnel groups. The indexed energy dissipation within the total cavopulmonary connection was strongly correlated to minimum cross-sectional area of the pulmonary arteries (R2 value of 0.90 and P \u3c .0002), whereas all other geometric features, including shape characteristics, had no significant correlation. Finally, cardiac index significantly correlated with the minimum pulmonary artery area (P = .006), suggesting that total cavopulmonary connection energy losses significantly affect resting cardiac output. The minimum outlet size of the total cavopulmonary connection (ie, minimum cross section of pulmonary artery) governs the energy loss characteristics of the total cavopulmonary connection more strongly than variations in the shapes corresponding to extracardiac and lateral tunnel configurations. Differences in pulmonary artery sizes must be accounted for when comparing energy losses between extracardiac and lateral tunnel geometries