Total cavopulmonary connection is the result of a series of palliative surgical repairs performed on patients with single ventricle heart defects. The resulting anatomy has complex and unsteady hemodynamics characterized by flow mixing and flow separation. Although varying degrees of flow pulsatility have been observed in vivo, non-pulsatile (time-averaged) boundary conditions have traditionally been assumed in hemodynamic modeling, and only recently have pulsatile conditions been incorporated without completely characterizing their effect or importance. In this study, 3D numerical simulations with both pulsatile and non-pulsatile boundary conditions were performed for 24 patients with different anatomies and flow boundary conditions from Georgia Tech database. Flow structures, energy dissipation rates and pressure drops were compared under rest and simulated exercise conditions. It was found that flow pulsatility is the primary factor in determining the appropriate choice of boundary conditions, whereas the anatomic configuration and cardiac output had secondary effects. Results show that the hemodynamics can be strongly influenced by the presence of pulsatile flow. However, there was a minimum pulsatility threshold, identified by defining a weighted pulsatility index (wPI), above which the influence was significant. It was shown that when wPI < 30%, the relative error in hemodynamic predictions using time-averaged boundary conditions was less than 10% compared to pulsatile simulations. In addition, when wPI < 50, the relative error was less than 20%. A correlation was introduced to relate wPI to the relative error in predicting the flow metrics with non-pulsatile flow conditions.
Background
It is known that respiration modulates cavopulmonary flows, but little data compare mean flows under breath-holding and free-breathing conditions to isolate the respiratory effects and effects of exercise on the respiratory modulation. Methods Real-time phase-contrast magnetic resonance combined with a novel method to track respiration on the same image acquisition was used to investigate respiratory effects on Fontan caval and aortic flows under breath-holding, free-breathing, and exercise conditions. Respiratory phasicity indices that were based on beat-averaged flow were used to quantify the respiratory effect. Results Flow during inspiration was substantially higher than expiration under the free-breathing and exercise conditions for both inferior vena cava (inspiration/expiration: 1.6 ± 0.5 and 1.8 ± 0.5, respectively) and superior vena cava (inspiration/expiration: 1.9 ± 0.6 and 2.6 ± 2.0, respectively). Changes from rest to exercise in the respiratory phasicity index for these vessels further showed the impact of respiration. Total systemic venous flow showed no significant statistical difference between the breath-holding and free-breathing conditions. In addition, no substantial difference was found between the descending aorta and inferior vena cava mean flows under either resting or exercise conditions. Conclusions This study demonstrated that inferior vena cava and superior vena cava flow time variance is dominated by respiratory effects, which can be detected by the respiratory phasicity index. However, the minimal respiration influence on net flow validates the routine use of breath-holding techniques to measure mean flows in Fontan patients. Moreover, the mean flows in the inferior vena cava and descending aorta are interchangeable.
by
Steven M. Schwartz;
Minmin Lu;
Richard G. Ohye;
Kevin D. Hill;
Andrew M. Atz;
Maryam Y. Naim;
Ismee A. Williams;
Caren S. Goldberg;
Alan Lewis;
Frank Pigula;
Peter Manning;
Christian Pizarro;
Paul Chai;
Rachel McCandless;
Carolyn Dunbar-Masterson;
Jonathan R. Kaltman;
Kirk Kanter;
Lynn A. Sleeper;
Julie V. Schonbeck;
Nancy Ghanayem
Background: The single-ventricle reconstruction trial randomized patients with single right ventricle lesions to a modified Blalock-Taussig or right ventricle-to-pulmonary artery shunt at the Norwood. This analysis describes outcomes at the stage 2 procedure and factors associated with a longer hospital length of stay (LOS).
Methods: We examined the association of shunt type with stage 2 hospital outcomes. Cox regression and bootstrapping were used to evaluate risk factors for longer LOS. We also examined characteristics associated with in-hospital death.
Results: There were 393 subjects in the analytic cohort. Median stage 2 procedure hospital LOS (8 days; interquartile range [IQR], 6-14 days), hospital mortality (4.3%), transplantation (0.8%), median ventilator time (2 days; IQR, 1-3 days), median intensive care unit LOS (4 days; IQR, 3-7 days), number of additional cardiac procedures or complications, and serious adverse events did not differ by shunt type. Longer LOS was associated (R2 = 0.26) with center, longer post-Norwood LOS (hazard ratio [HR], 1.93 per log day; P <.001), nonelective timing of the stage 2 procedure (HR, 1.78; P <.001), and pulmonary artery (PA) stenosis (HR, 1.56; P <.001). By univariate analysis, nonelective stage 2 (65% vs 32%; P =.009), moderate or greater atrioventricular valve (AVV) regurgitation (75% vs 24%; P <.001), and AVV repair (53% vs 9%; P <.001) were among the risk factors associated with in-hospital death.
Conclusions: Norwood LOS, PA stenoses, and nonelective stage 2 procedure, but not shunt type, are independently associated with longer LOS. Nonelective stage 2 procedure, moderate or greater AVV regurgitation, and need for AVV repair are among the risk factors for death.
The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.
by
Kartik S. Sundareswaran;
Christopher M. Haggerty;
Diane de Zelicourt;
Lakshmi P. Dasi;
Kerem Pekkan;
David H. Frakes;
Andrew J. Powell;
Kirk R Kanter;
Mark A. Fogel;
Ajit Yoganathan
Objective: Our objective was to analyze 3-dimensional (3D) blood flow patterns within the total cavopulmonary connection (TCPC) using in vivo phase contrast magnetic resonance imaging (PC MRI).
Methods: Sixteen single-ventricle patients were prospectively recruited at 2 leading pediatric institutions for PC MRI evaluation of their Fontan pathway. Patients were divided into 2 groups. Group 1 comprised 8 patients with an extracardiac (EC) TCPC, and group 2 comprised 8 patients with a lateral tunnel (LT) TCPC. A coronal stack of 5 to 10 contiguous PC MRI slices with 3D velocity encoding (5-9 ms resolution) was acquired and a volumetric flow field was reconstructed.
Results: Analysis revealed large vortices in LT TCPCs and helical flow structures in EC TCPCs. On average, there was no difference between LT and EC TCPCs in the proportion of inferior vena cava flow going to the left pulmonary artery (43% ± 7% vs 46% ± 5%; P = .34). However, for EC TCPCs, the presence of a caval offset was a primary determinant of inferior vena caval flow distribution to the pulmonary arteries with a significant bias to the offset side.
Conclusions: 3D flow structures within LT and EC TCPCs were reconstructed and analyzed for the first time using PC MRI. TCPC flow patterns were shown to be different, not only on the basis of LT or EC considerations, but with significant influence from the superior vena cava connection as well. This work adds to the ongoing body of research demonstrating the impact of TCPC geometry on the overall hemodynamic profile.
by
Christopher M. Haggerty;
Maria Restrepo;
Elaine Tang;
Diane A. de Zelicourt;
Kartik S. Sundareswaran;
Lucia Mirabella;
James Bethel;
Kevin K. Whitehead;
Mark A. Fogel;
Ajit Yoganathan
Objectives: This study sought to quantify average hemodynamic metrics of the Fontan connection as reference for future investigations, compare connection types (intra-atrial vs extracardiac), and identify functional correlates using computational fluid dynamics in a large patient-specific cohort. Fontan hemodynamics, particularly power losses, are hypothesized to vary considerably among patients with a single ventricle and adversely affect systemic hemodynamics and ventricular function if suboptimal.
Methods: Fontan connection models were created from cardiac magnetic resonance scans for 100 patients. Phase velocity cardiac magnetic resonance in the aorta, vena cavae, and pulmonary arteries was used to prescribe patient-specific time-averaged flow boundary conditions for computational fluid dynamics with a customized, validated solver. Comparison with 4-dimensional cardiac magnetic resonance velocity data from selected patients was used to provide additional verification of simulations. Indexed Fontan power loss, connection resistance, and hepatic flow distribution were quantified and correlated with systemic patient characteristics.
Results: Indexed power loss varied by 2 orders of magnitude, whereas, on average, Fontan resistance was 15% to 20%of published values of pulmonary vascular resistance in single ventricles. A significant inverse relationship was observed between indexed power loss and both systemic venous flow and cardiac index. Comparison by connection type showed no differences between intra-atrial and extracardiac connections. Instead, the least efficient connections revealed adverse consequences from localized Fontan pathway stenosis.
Conclusions: Fontan power loss varies from patient to patient, and elevated levels are correlated with lower systemic flow and cardiac index. Fontan connection type does not influence hemodynamic efficiency, but an undersized or stenosed Fontan pathway or pulmonary arteries can be highly dissipative.
by
Fred Rodriguez III;
Alexander C Egbe;
William R Miranda;
Janaki Devara;
Likhita Shaik;
Momina Iftikhar;
Ahmed Goda Sakr;
Anitha John;
Ari Cedars;
Fred, III Rodriguez;
Jeremy P Moore;
Matthew Russell;
Jasmine Grewal;
Salil Ginde;
Adam M Lubert;
Heidi M Connolly
Background: Total cavopulmonary connection (TCPC) is associated with a lower risk of incident atrial arrhythmias as compared to atriopulmonary Fontan, but the risk of recurrent atrial arrhythmias is unknown in this population. The purpose of this study was to determine the incidence and risk factors for recurrent atrial arrhythmias and thromboembolic complications in patients with TCPC. Methods: This is a retrospective multicenter study conducted by the Alliance for Adult Research in Congenital Cardiology (AARCC), 2000–2018. The inclusion criteria were TCPC patients (age > 15 years) with prior history of atrial arrhythmia. Results: A total of 103 patients (age 26 ± 7 years; male 58 [56%]) met inclusion criteria. The mean age at initial arrhythmia diagnosis was 13 ± 5 years, and atrial arrhythmias were classified as atrial flutter/tachycardia in 85 (83%) and atrial fibrillation in 18 (17%). The median duration of follow-up from the first episode of atrial arrhythmia was 14.9 (12.1–17.3) years, and during this period 64 (62%) patients had recurrent atrial arrhythmias (atrial flutter/tachycardia 51 [80%] and atrial fibrillation 13 [20%]) with annual incidence of 4.4%. Older age was a risk factor for arrhythmia recurrence while the use of a class III anti-arrhythmic drug was associated with a lower risk of recurrent arrhythmias. The incidence of thromboembolic complication was 0.6% per year, and the cumulative incidence was 4% and 7% at 5 and 10 years respectively from the time of first atrial arrhythmia diagnosis. There were no identifiable risk factors for thromboembolic complications in this cohort. Conclusions: Although TCPC provides superior flow dynamics and lower risk of incident atrial arrhythmias, there is a significant risk of recurrent arrhythmias among TCPC patients with a prior history of atrial arrhythmias. These patients may require more intensive arrhythmia surveillance as compared to other TCPC patients.
by
Catherine M Avitabile;
David J Goldberg;
Mary B Leonard;
Zhenglun A Wei;
Elaine Tang;
Stephen M Paridon;
Ajit Yoganathan;
Mark A Fogel;
Kevin K Whitehead
Objective We previously described lower leg lean mass Z-scores (LLMZ) in Fontan patients associated with worse peak oxygen consumption on metabolic exercise testing. We hypothesised that LLMZ correlates with indexed systemic flow (Qsi) and cardiac index (CI) on exercise cardiac magnetic resonance (eCMR). Methods Thirteen patients had LLM measured by dual-energy X-ray absorptiometry within mean 40 (range 0-258) days of eCMR. LLM was converted to sex and race-specific Z-scores based on healthy reference data. Ventricular volumes and flow measurements of the ascending and descending (DAO) aorta and superior vena cava (SVC) were obtained by CMR at rest and just after supine ergometer exercise to a heart rate associated with anaerobic threshold on prior exercise test. Baseline and peak exercise measures of Qsi (SVC+DAO/BSA) and CI, as well as change in Qsi and CI with exercise, were compared with LLMZ by linear regression. Results LLMZ was not correlated with resting flows, stroke volume or CI. There was a strong linear correlation between LLMZ and change in both CI (r=0.77, p=0.002) and Qsi (r=0.73, p=0.005) from rest to exercise. There was also a significant correlation between LLMZ and Qsi at exercise (r=0.70, p=0.008). The correlation between LLMZ and CI at exercise did not reach significance (r=0.3, p=0.07). Conclusions In our cohort, there was a strong linear correlation between LLMZ and change in both CI and Qsi from rest to exercise, suggesting that Fontan patients with higher LLMZ may be better able to augment systemic output during exercise, improving performance.
by
Sarah T. Plummer;
Christoph P. Hornik;
Hamilton Baker;
Gregory A. Fleming;
Susan Foerster;
Matthew Ferguson;
Andrew C. Glatz;
Russel Hirsch;
Jeffrey P. Jacobs;
Kyong-Jin Lee;
Alan B. Lewis;
Jennifer S. Li;
Mary Martin;
Diego Porras;
Wolfgang A. K. Radtke;
John F. Rhodes;
Julie A. Vincent;
Jeffrey D. Zampi;
Kevin D. Hill
Objectives: Aortic arch reconstruction in children with single ventricle lesions may predispose to circulatory inefficiency and maladaptive physiology leading to increased myocardial workload. We sought to describe neoaortic anatomy and physiology, risk factors for abnormalities, and impact on right ventricular function in patients with single right ventricle lesions after arch reconstruction. Methods: Prestage II aortic angiograms from the Pediatric Heart Network Single Ventricle Reconstruction trial were analyzed to define arch geometry (Romanesque [normal], crenel [elongated] , or gothic [angular]), indexed neoaortic dimensions, and distensibility. Comparisons were made with 50 single-ventricle controls without prior arch reconstruction. Factors associated with ascending neoaortic dilation, reduced distensibility, and decreased ventricular function on the 14-month echocardiogram were evaluated using univariate and multivariable logistic regression. Results: Interpretable angiograms were available for 326 of 389 subjects (84%). Compared with controls, study subjects more often demonstrated abnormal arch geometry (67% vs 22%, P < .01) and had increased ascending neoaortic dilation (Z score 3.8 ± 2.2 vs 2.6 ± 2.0, P < .01) and reduced distensibility index (2.2 ± 1.9 vs 8.0 ± 3.8, P < .01). Adjusted odds of neoaortic dilation were increased in subjects with gothic arch geometry (odds ratio [OR], 3.2 vs crenel geometry, P < .01) and a right ventricle-pulmonary artery shunt (OR, 3.4 vs Blalock–Taussig shunt, P < .01) but were decreased in subjects with aortic atresia (OR, 0.7 vs stenosis, P < .01) and those with recoarctation (OR, 0.3 vs no recoarctation, P = .04). No demographic, anatomic, or surgical factors predicted reduced distensibility. Neither dilation nor distensibility predicted reduced right ventricular function. Conclusions: After Norwood surgery, the reconstructed neoaorta demonstrates abnormal anatomy and physiology. Further study is needed to evaluate the longer-term impact of these features.