Matthew A. Harris

Noninvasive quantification of systemic-to-pulmonary collateral flow: a major source of inefficiency in patients with superior cavopulmonary connections.

Background—Systemic-to-pulmonary collateral flow (SPCF) is common in single-ventricle patients with superior cavopulmonary connections (SCPC). Because no validated method to quantify that SPCF exists, neither its hemodynamic burden nor its clinical impact can be systematically evaluated. We hypothesize that (1) the difference in total ascending aortic (Ao) and caval flow (superior vena cava [SVC]+inferior vena cava [IVC]) and (2) the difference between pulmonary vein and pulmonary artery flow (PV−PA) provide 2 independent estimators of SPCF. Methods and Results—We measured Ao, SVC, IVC, right (RPA) and left (LPA) PA, and left (LPV) and right (RPV) PV flows in 17 patients with SCPC during routine cardiac MRI studies using through-plane phase-contrast velocity mapping. Two independent measures of SPCF were obtained: model 1, Ao−(SVC+IVC); and model 2, (LPV−LPA)+(RPV−RPA). Values were normalized to body surface area, Ao, and PV, and comparisons were made using linear regression and Bland-Altman analysis. SPCF ranged from 0.2 to 1.4 L/min for model 1 and 0.2 to 1.6 L/min for model 2, for an average indexed SPCF of 0.5 to 2.8 L/min/m2: 11% to 53% (mean, 37%) of Ao and 19% to 77% (mean, 54%) of PV. The mean difference between model 1 and model 2 was 0.01 L/min (P=0.40; 2-SD range, −0.45 to 0.47 L/min). Conclusions—We present a noninvasive method for SPCF quantification in patients with SCPC. It should provide an important clinical tool in treating these patients. Furthermore, we show that SPCF is a significant hemodynamic burden in many patients with bidirectional Glenn shunt physiology. Future investigations will allow objective study of the impact of collateral flow on outcome.Background— Systemic-to-pulmonary collateral flow (SPCF) is common in single-ventricle patients with superior cavopulmonary connections (SCPC). Because no validated method to quantify SPCF exists, neither its hemodynamic burden nor its clinical impact can be systematically evaluated. We hypothesize that (1) the difference in total ascending aortic (Ao) and caval flow (superior vena cava [SVC]+inferior vena cava [IVC]) and (2) the difference between pulmonary vein and pulmonary artery flow (PV−PA) provide 2 independent estimators of SPCF. Methods and Results— We measured Ao, SVC, IVC, right (RPA) and left (LPA) PA, and left (LPV) and right (RPV) PV flows in 17 patients with SCPC during routine cardiac MRI studies using through-plane phase-contrast velocity mapping. Two independent measures of SPCF were obtained: model 1, Ao−(SVC+IVC); and model 2, (LPV−LPA)+(RPV−RPA). Values were normalized to body surface area, Ao, and PV, and comparisons were made using linear regression and Bland-Altman analysis. SPCF ranged from 0.2 to 1.4 L/min for model 1 and 0.2 to 1.6 L/min for model 2, for an average indexed SPCF of 0.5 to 2.8 L/min/m2: 11% to 53% (mean, 37%) of Ao and 19% to 77% (mean, 54%) of PV. The mean difference between model 1 and model 2 was 0.01 L/min ( P =0.40; 2-SD range, −0.45 to 0.47 L/min). Conclusions— We present a noninvasive method for SPCF quantification in patients with SCPC. It should provide an important clinical tool in treating these patients. Furthermore, we show that SPCF is a significant hemodynamic burden in many patients with bidirectional Glenn shunt physiology. Future investigations will allow objective study of the impact of collateral flow on outcome. Received November 10, 2008; accepted July 7, 2009. # CLINICAL PERSPECTIVE {#article-title-2}

Systemic-to-Pulmonary Collateral Flow, as Measured by Cardiac Magnetic Resonance Imaging, Is Associated With Acute Post-Fontan Clinical Outcomes

Background— Systemic-pulmonary collateral (SPC) flow occurs commonly in single ventricle patients after superior cavo-pulmonary connection, with unclear clinical significance. We sought to evaluate the association between SPC flow and acute post-Fontan clinical outcomes using a novel method of quantifying SPC flow by cardiac magnetic resonance (CMR) imaging. Methods and Results— All patients who had SPC flow quantified by CMR imaging before Fontan were retrospectively reviewed to assess for acute clinical outcomes after Fontan completion. Forty-four subjects were included who had Fontan completion between May 2008 and September 2010. SPC flow prior to Fontan measured 1.5±0.9 L/min/m2, accounting for 31±11% of total aortic flow and 44±15% of total pulmonary venous flow. There was a significant linear association between natural log-transformed duration of hospitalization and SPC flow as a proportion of total aortic (rho=0.31, P=0.04) and total pulmonary venous flow (rho=0.29, P=0.05). After adjustment for Fontan type and presence of a fenestration, absolute SPC flow was significantly associated with hospital duration ≥7 days (odds ratio [OR]=9.2, P=0.02) and chest tube duration ≥10 days (OR=22.7, P=0.009). Similar associations exist for SPC flow as a percentage of total aortic (OR=1.09, P=0.048 for hospitalization ≥7 days; OR=1.24, P=0.007 for chest tube duration ≥10 days) and total pulmonary venous flow (OR=1.07, P=0.048 for hospitalization ≥7 days; OR=1.18, P=0.006 for chest tube duration ≥10 days). Conclusions— Increasing SPC flow before Fontan, as measured by CMR imaging, is associated with increased duration of hospitalization and chest tube following Fontan completion.

Blood flow distribution in a large series of patients having the Fontan operation: A cardiac magnetic resonance velocity mapping study

OBJECTIVES Our goal was to determine flow distribution in the cavopulmonary connections of patients with and without bilateral superior venae cavae who had the Fontan procedure. No large series exists that establishes the flow distributions in Fontan patients, which would be an important resource for everyday clinical use and may affect future surgical reconstruction. METHODS We studied 105 Fontan patients (aged 2-24 years) with through-plane phase contrast velocity mapping to determine flow rates in the inferior and superior venae cavae and left and right pulmonary arteries. Superior caval anastomosis type included 40 bidirectional Glenn shunts (of which 15 were bilateral) and 53 hemi-Fontan anastomoses; Fontan type included 69 intra-atrial baffles, 28 extracardiac conduits, and 4 atriopulmonary connections. RESULTS Total caval flow was 2.9 +/- 1.0 L x min(-1) x m(-2), with an inferior vena cava contribution of 59% +/- 15%. Total pulmonary flow was 2.5 +/- 0.8 L x min(-1) x m(-2), statistically less than caval flow and not explained by fenestration presence. The right pulmonary artery contribution (55% +/- 13%) was statistically greater than the left. In patients with bilateral superior cavae, the right cava accounted for 52% +/- 14% of the flow, with no difference in pulmonary flow splits (50% +/- 16% to the right). Age and body surface area correlated with percent inferior caval contribution (r = 0.60 and 0.74, respectively). Superior vena cava anastomosis and Fontan type did not significantly affect pulmonary flow splits. CONCLUSIONS Total Fontan cardiac index was 2.9 L x min(-1) x m(-2), with normal pulmonary flow splits (55% to the right lung). Inferior vena caval contribution to total flow increases with body surface area and age, consistent with data from healthy children.

X-Ray Magnetic Resonance Fusion to Internal Markers and Utility in Congenital Heart Disease Catheterization

Background—X-ray magnetic resonance fusion (XMRF) allows for use of 3D data during cardiac catheterization. However, to date, technical requirements have limited the use of this modality in clinical practice. We report on a new internal-marker XMRF method that we have developed and describe how we used XMRF during cardiac catheterization in congenital heart disease. Methods and Results—XMRF was performed in a phantom and in 23 patients presenting for cardiac catheterization who also needed cardiac MRI for clinical reasons. The registration process was performed in <5 minutes per patient, with minimal radiation (0.004 to 0.024 mSv) and without contrast. Registration error was calculated in a phantom and in 8 patients using the maximum distance between angiographic and 3D model boundaries. In the phantom, the measured error in the anteroposterior projection had a mean of 1.15 mm (standard deviation, 0.73). The measured error in patients had a median of 2.15 mm (interquartile range, 1.65 to 2.56 mm). Internal markers included bones, airway, image artifact, calcifications, and the heart and vessel borders. The MRI data were used for road mapping in 17 of 23 (74%) cases and camera angle selection in 11 of 23 (48%) cases. Conclusions—Internal marker–based registration can be performed quickly, with minimal radiation, without the need for contrast, and with clinically acceptable accuracy using commercially available software. We have also demonstrated several potential uses for XMRF in routine clinical practice. This modality has the potential to reduce radiation exposure and improve catheterization outcomes.

MRI of Lymphatic Abnormalities After Functional Single-Ventricle Palliation Surgery

OBJECTIVE Protein-losing enteropathy (PLE) and plastic bronchitis are serious complications that occur after single-ventricle surgery. A lymphatic cause for these conditions has been proposed, but imaging correlation has not been reported. The objective of this study was to evaluate lymphatic abnormalities in patients after functional single-ventricle palliation compared with patients with non-single-ventricle congenital heart conditions using T2-weighted MR lymphangiography. MATERIALS AND METHODS We retrospectively reviewed imaging data from 48 patients who underwent T2-weighted MR lymphangiography in our institution between May 1, 2012, and October 24, 2012. The patients were divided into four groups: patients who underwent superior cavopulmonary connection, patients who underwent total cavopulmonary connection, patients with total cavopulmonary connection and lymphatic complications, and patients with non-single-ventricle cardiac anomalies. RESULTS There were 38 patients with single ventricles in this study. The lymphatic abnormalities observed in these patients included thoracic duct dilation greater than 3 mm (31%), lymphangiectasia and lymphatic collateralization (78%), and tissue edema (86%). There were five patients with PLE, one patient with plastic bronchitis, and one patient with chronic chylous effusions and superior cavopulmonary connection. The patients with PLE and plastic bronchitis had statistically significant larger thoracic duct maximal diameters (median, 3.9 mm; range, 3-7.2 mm) than did the other patients with total cavopulmonary connection (p < 0.01). In the two-ventricle patient group, there were no abnormal lymphatic findings. CONCLUSION Lymphatic abnormalities are found in many patients after functional single-ventricle palliation. T2-weighted unenhanced MRI is capable of anatomic assessment of the lymphatic system in this patient population and has promise for guiding treatment in the future.

Deep sedation for cardiac magnetic resonance imaging: a comparison with cardiac anesthesia.

OBJECTIVE To test the hypothesis that safety, efficacy, and image quality in pediatric patients who undergo deep sedation for cardiac magnetic resonance imaging (CMR) for congenital heart disease (CHD) is similar to general anesthesia (GA). STUDY DESIGN Retrospective review of all CMR records from 1997-2006. Six hundred sixty patients underwent deep sedation (DS) and 161 underwent GA. Statistics included analysis of variance, chi(2) analysis, and the coefficient of variation. RESULTS Diagnoses included a broad spectrum of CHD. No serious adverse events (AE) including mortalities and hospitalizations occurred because of DS. There were 18 (2.8%) self-limited events in the DS group with a success rate of 97.9%. The AE rate for patients undergoing GA was 3.9% (n = 6), including 2 overnight hospital stays with a success rate of 100%. AE and success rates did not differ between the 2 groups. Observers blinded to the patients group found no difference in image quality. Even in young infants, excellent image quality was obtained. CONCLUSIONS Sedation of appropriately screened pediatric patients with CHD undergoing CMR is safe and well tolerated and yields high-quality images similar to GA. GA should be considered for patients with CHD with hemodynamic or airway compromise, in whom sedation has failed, or who have special circumstances.

Cardiac Magnetic Resonance and the Need for Routine Cardiac Catheterization in Single Ventricle Patients Prior to Fontan: A Comparison of 3 Groups: Pre-Fontan CMR Versus Cath Evaluation

OBJECTIVES This study investigated whether cardiac magnetic resonance (CMR) and echocardiography (echo) can replace catheterization (cath) for routine evaluation prior to Fontan and under what circumstances CMR and cath are used together. BACKGROUND Routine cath prior to Fontan has been utilized for years; noninvasive methods, however, may be sufficient. METHODS This study reviews clinical data in 119 consecutive patients investigating 3 groups: those who underwent CMR alone (MR; n = 41), cath alone (C; n = 41), or both cath and CMR (C+M; n = 37) prior to Fontan. RESULTS No clinically significant differences were noted in patient characteristics, hemodynamics, or clinical status prior to or after surgery between the C and MR groups. CMR added information in 82%. There were no discrepant findings between CMR and cath data in the C+M group. Diagnostic success was ≥95% in all groups. Of those undergoing Fontan completion, the C+M group had similar outcomes to C and MR; C and CMR were utilized in combination to assess aortopulmonary collaterals or the need for an intervention or evaluate its success. Echo could not delineate pulmonary arterial anatomy in 46% to 53% of patients. The C+M and C groups were exposed to 6.8 ± 4.1 mSv of radiation. CONCLUSIONS Single ventricle patients not requiring an intervention can undergo successful Fontan completion with CMR and echo alone with similar short-term outcomes to C, which was used as a control, preventing an invasive test and exposure to radiation. CMR can add information in a significant number of patients. Cath and CMR are utilized together for interventions and assessment of aortopulmonary collaterals.

Bilateral Branch Pulmonary Artery Melody Valve Implantation for Treatment of Complex Right Ventricular Outflow Tract Dysfunction in a High-Risk Patient

Percutaneous pulmonary valve replacement is one of the most important advancements in the field of interventional cardiology in the past decade.1,2 However, currently available technologies are not applicable to patients with oversized right ventricular outflow tracts (RVOTs), especially when there is concomitant proximal branch pulmonary artery (PA) stenosis. This combination commonly is encountered in clinical practice. Our group has a longstanding interest in these complex patients, and we have recently published preclinical studies describing the feasibility and short-term effects of implanting 2 Melody valves—1 into each proximal branch PA—in an ovine model of postoperative pulmonary insufficiency and dilated RVOT.3 This report describes bilateral branch PA Melody valve implantation to treat complex RVOT dysfunction in a high-risk patient. At presentation, the patient was a 27-year-old woman with a complex medical history. Her cardiac condition was double-outlet RV with pulmonary stenosis and interrupted inferior vena cava with azygos continuation to a left-sided superior vena cava. She was status post-Waterston shunt as an infant, with subsequent closure of the ventricular septal defect and patch augmentation of the RVOT. Three months before catheterization, the patient presented to her cardiologist with symptoms of progressive activity intolerance over the past year. She was oxygen dependent and on long-term continuous positive airway pressure therapy. Comorbidities included VATER and Klippel-Feil syndromes, renal agenesis, Mullerian agenesis, gout, and obesity. The patient had undergone multiple spinal fusion and Harrington rod procedures as well as repair of tracheoesophageal …

Clinical ResearchCongenital Heart DiseaseCardiac Magnetic Resonance and the Need for Routine Cardiac Catheterization in Single Ventricle Patients Prior to Fontan: A Comparison of 3 Groups: Pre-Fontan CMR Versus Cath Evaluation

OBJECTIVES This study investigated whether cardiac magnetic resonance (CMR) and echocardiography (echo) can replace catheterization (cath) for routine evaluation prior to Fontan and under what circumstances CMR and cath are used together. BACKGROUND Routine cath prior to Fontan has been utilized for years; noninvasive methods, however, may be sufficient. METHODS This study reviews clinical data in 119 consecutive patients investigating 3 groups: those who underwent CMR alone (MR; n = 41), cath alone (C; n = 41), or both cath and CMR (C+M; n = 37) prior to Fontan. RESULTS No clinically significant differences were noted in patient characteristics, hemodynamics, or clinical status prior to or after surgery between the C and MR groups. CMR added information in 82%. There were no discrepant findings between CMR and cath data in the C+M group. Diagnostic success was ≥95% in all groups. Of those undergoing Fontan completion, the C+M group had similar outcomes to C and MR; C and CMR were utilized in combination to assess aortopulmonary collaterals or the need for an intervention or evaluate its success. Echo could not delineate pulmonary arterial anatomy in 46% to 53% of patients. The C+M and C groups were exposed to 6.8 ± 4.1 mSv of radiation. CONCLUSIONS Single ventricle patients not requiring an intervention can undergo successful Fontan completion with CMR and echo alone with similar short-term outcomes to C, which was used as a control, preventing an invasive test and exposure to radiation. CMR can add information in a significant number of patients. Cath and CMR are utilized together for interventions and assessment of aortopulmonary collaterals.

Melody Valve Implantation Into the Branch Pulmonary Arteries for Treatment of Pulmonary Insufficiency in an Ovine Model of Right Ventricular Outflow Tract Dysfunction Following Tetralogy of Fallot Repair

Background—Transannular patch (TAP) repair of tetralogy of Fallot often results in significant right ventricular outflow tract (RVOT) dilation and distortion. We hypothesized that insertion of Melody valves into the proximal right and left branch pulmonary arteries (PAs) would reduce pulmonary regurgitation fraction (PRF) in an ovine model of pulmonary insufficiency and dilated RVOT. Methods and Results—Ten sheep underwent baseline cardiac catheterization, surgical pulmonary valvectomy, and TAP placement. A subset (n=5) had Melody valves (2 devices per animal) inserted into the proximal right and left PAs during the surgical procedure. Melody valves were placed distal to the right-upper-lobe (RUL) artery branch, leaving the RUL “unprotected.” Preoperative MRIs (n=5) were used to determine baseline RV ejection fraction (RVEF) and left ventricular (LV) EF. All surviving animals (n=9) underwent MRI and catheterization 6 weeks postsurgery.Mean PRF was lower in the Melody valve group (15±6% versus 37±3%; P=0.014). The unprotected RUL was responsible for 64% of the PRF measured in the Melody valve group. In the non-Melody group, the RVEF was lower than baseline (P=0.003) and than in the Melody group (P=0.05). The LVEF was also lower in the non-Melody group versus baseline (P=0.004) and versus Melody (P=0.01). Conclusions—Bilateral branch PA Melody valve implantation significantly reduced PRF and altered RV and LV function favorably in a model of TAP for tetralogy of Fallot. This novel intervention may offer potential benefit in treating patients with anatomically heterogeneous disease of the RVOT.