Out of the blue: inflammatory myofibroblastic tumour identified during repair of tetralogy of Fallot with absent pulmonary valve.

Inflammatory myofibroblastic tumour of the heart is an exceedingly rare benign neoplasm. While benign, without prompt management its impact can be devastating. Tetralogy of Fallot with absent pulmonary valve is a rare form of CHD. We present the first documented case of inflammatory myofibroblastic tumour of the heart in the presence of tetralogy of Fallot with absent pulmonary valve.

Goal-directed resuscitation following cardiac surgery reduces acute kidney injury: A quality initiative pre-post analysis.

OBJECTIVE: Acute kidney injury (AKI) occurs in 20% of patients following cardiac surgery. To reduce AKI in our institution, we instituted a quality improvement (QI) initiative using a goal-directed volume resuscitation protocol. Our protocol was designed to achieve quantifiable physiologic goals (eg, cardiac index > 2.5 L/min/m2, mean arterial pressure > 65 mm Hg) using fluid and vasoactive agents. The objective of this study was to evaluate AKI in the pre- and post-QI eras, hypothesizing that AKI incidence would decrease in the post-QI era. METHODS: In this observational retrospective cohort study, we identified patients who underwent cardiac operations from July 2011 to July 2015 with a risk score available. Kidney injury was determined using the lowest postoperative GFR within 7 days of surgery and standard Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Kidney Disease (RIFLE) classification criteria. The primary outcome was the rate of AKI, as defined by glomerular filtration rate-based RIFLE classification criteria injury, in the post- versus pre-QI eras. RESULTS: A total of 1979 patients were included, of whom 725 were in the pre-QI cohort, and 1254 in the post-QI cohort. Overall, rates of RIFLE classification criteria risk, injury and failure were 27.5%, 5.9%, and 3.6%, respectively. RIFLE classification criteria injury saw the largest decrease in the post-QI cohort (8.1% vs 4.6%; P = .001). Multivariable analysis demonstrated a 37% reduction in the odds of AKI in the post-QI cohort (adjusted odds ratio, 0.63; 95% confidence interval, 0.43-0.90). CONCLUSIONS: A goal-directed volume resuscitation protocol centered on patient fluid responsiveness is associated with significantly reduced risk for AKI after cardiac surgery. Protocol-driven approaches should be employed in intensive care units to improve outcomes.

Good at One or Good at All? Variability of Coronary and Valve Operation Outcomes Within Centers.

BACKGROUND: The technical expertise required for treatment of coronary and structural heart valve disease differs. Correlation between center-specific mortality rates after coronary artery bypass grafting (CABG) and valve operations has not been demonstrated. This study tested the hypothesis that risk-adjusted outcomes between coronary and valve procedures do not correlate within centers. METHODS: Records of patients undergoing isolated CABG, isolated aortic valve replacement (AVR), or isolated mitral valve replacement (MVR) procedures from 2008 to 2015 in a multi-institutional Society of Thoracic Surgeons (STS) database were used to generate observed-to-expected (O/E) ratios for morbidity and death. Ratios were based on the STS predicted risks of morbidity and death and were calculated by procedure for each institution. Linear regression models evaluated the relationship between institutional performance in CABG and valve operations. RESULTS: A total of 22,258 records from 18 institutions were analyzed: 17,026 CABG, 3,238 isolated AVR, and 1,994 MVR procedures. With respect to deaths, the correlation coefficients were weak; for AVR and CABG, it was 0.22 and was 0.26 for MVR and CABG. With respect to morbidity, a strong relationship was seen between the morbidity O/E ratios, with coefficients of 1.03 for AVR and 0.97 for MVR, suggesting a nearly 1:1 relationship between morbidities observed in an institution's CABG and valve operations. CONCLUSIONS: Sites that perform CABG with low mortality rates may not have similarly low mortality rates with valve operations. Most striking, however, is the nearly identical O/E ratio for morbidity for CABG and valve operations at each center. These findings suggest postoperative care as a major determinant for morbidity after cardiac operation.

Regional Practice Patterns and Outcomes of Surgery for Acute Type A Aortic Dissection.

BACKGROUND: The surgical management of acute type A aortic dissection is evolving, and many aortic centers of excellence are reporting superior outcomes. We hypothesize that similar trends exist in a multiinstitutional regional consortium. METHODS: Records for 884 consecutive patients who underwent aortic operations (2003 to 2015) for acute type A aortic dissection were extracted from a regional The Society of Thoracic Surgeons database. Patients were stratified into three equal operative eras. Differences in outcomes and risk factors for morbidity and mortality were determined. RESULTS: Surgical procedures for type A aortic dissection are increasing in extent and complexity. Aortic root repair was performed in 16% of early era cases compared with 67% currently (p < 0.0001). Similarly, aortic arch repair increased from 27% to 37% cases (p < 0.0001). Cerebral perfusion is currently used in 85% of circulatory arrest cases, most frequently antegrade (57%). Total circulatory arrest times increased (29 minutes vs 31 minutes vs 36 minutes; p = 0.005), but times without cerebral perfusion were stable (12 minutes vs 6 minutes; p = 0.68). Although the operative mortality rate remained stable at 18.9% during the 3 operative eras, there were significant decreases in pneumonia and reoperations (p < 0.05). Predictors of operative mortality and major morbidity are age (odds ratio [OR], 1.04; p < 0.0001), previous stroke (OR, 2.09; p = 0.03), and elevated creatinine (OR, 1.31; p = 0.01). Importantly, the extent of aortic operation did not increase risk for morbidity or mortality. CONCLUSIONS: Operative morbidity and mortality remain significant for type A aortic dissection, but lower than historical outcomes. The extent of aortic surgery has increased, resulting in adaptive cerebral protection changes in contemporary "real-world" practice.

Outcomes for Low-Risk Surgical Aortic Valve Replacement: A Benchmark for Aortic Valve Technology.

BACKGROUND: Two large, randomized trials are underway evaluating transcatheter aortic valve replacement (AVR) against conventional surgical AVR. We analyzed contemporary, real-world outcomes of surgical AVR in low-risk patients to provide a practical benchmark of outcomes and cost for evaluating current and future transapical AVR technology. METHODS: From 2010 to 2015, 2,505 isolated AVR operations were performed for severe aortic stenosis at 18 statewide cardiac institutions. Of these, 2,138 patients had a Society of Thoracic Surgeons predicted risk of mortality of less than 4%, and 1,119 met other clinical and hemodynamic criteria as outlined in the PARTNER 3 (The Placement of Transcatheter Aortic Valves) protocol. Patients with endocarditis, end-stage renal disease, ejection fraction of less than 0.45, bicuspid valves, and previous valve replacements were excluded. Outcomes of interest included operative death and postoperative adverse events. RESULTS: The median Society of Thoracic Surgeons predicted risk of mortality for the study-eligible patients was 1.44%, with a median age of 72 years (interquartile range [IQR], 65 to 78 years). Operative mortality was 1.3%, permanent stroke was 1.3%, and pacemaker requirement was 4.2%. The most common adverse events were transfusion of 2 or more units of red blood cells (18%) and atrial fibrillation (28%). The median length of stay was 6 days (IQR, 5 to 8 days). Median total hospital cost was $37,999 (IQR, $30,671 to $46,138). Examination of complications by age younger than 65 vs 65 or older demonstrated a significantly lower need for transfusion (11.2%, p < 0.001) and incidence of atrial fibrillation (17.1%, p < 0.001) but no difference in operative mortality (2.2% vs 0.9%, p = 0.1), major morbidity (10.4% vs 12.6%, p = 0.3), or total hospital costs. CONCLUSIONS: Low-risk patients undergoing surgical AVR in the current era have excellent results. The most common complications were atrial fibrillation and bleeding. These real-world results should provide additional context for upcoming transcatheter clinical trial data.

Impact of Transcatheter Technology on Surgical Aortic Valve Replacement Volume, Outcomes, and Cost.

BACKGROUND: Transcatheter aortic valve replacement (TAVR) represents a disruptive technology that is rapidly expanding in use. We evaluated the effect on surgical aortic valve replacement (SAVR) patient selection, outcomes, volume, and cost. METHODS: A total of 11,565 patients who underwent SAVR, with or without coronary artery bypass grafting (2002 to 2015), were evaluated from the Virginia Cardiac Services Quality Initiative database. Patients were stratified by surgical era: pre-TAVR era (2002 to 2008, n = 5,113), early-TAVR era (2009 to 2011, n = 2,709), and commercial-TAVR era (2012 to 2015, n = 3,743). Patient characteristics, outcomes, and resource utilization were analyzed by univariate analyses. RESULTS: Throughout the study period, statewide SAVR volumes increased with median volumes of pre-TAVR: 722 cases/year, early-TAVR: 892 cases/year, and commercial-TAVR: 940 cases/year (p = 0.005). Implementation of TAVR was associated with declining Society of Thoracic Surgeons predicted risk of mortality among SAVR patients (3.7%, 2.6%, and 2.4%; p < 0.0001), despite increasing rates of comorbid disease. The mortality rate was lowest in the current commercial-TAVR era (3.9%, 4.3%, and 3.2%; p = 0.05), and major morbidity decreased throughout the time period (21.2%, 20.5%, and 15.2%; p < 0.0001). The lowest observed-to-expected ratios for both occurred in the commercial-TAVR era (0.9 and 0.9, respectively). Resource utilization increased generally, including total cost increases from $42,835 to $51,923 to $54,710 (p < 0.0001). CONCLUSIONS: At present, SAVR volumes have not been affected by the introduction of TAVR. The outcomes for SAVR continue to improve, potentially due to availability of transcatheter options for high-risk patients. Despite rising costs for SAVR, open approaches still provide a significant cost advantage over TAVR.

Postoperative Hypoglycemia Is Associated With Worse Outcomes After Cardiac Operations.

BACKGROUND: Hypoglycemia is a known risk of intensive postoperative glucose control in patients undergoing cardiac operations. However, neither the consequences of hypoglycemia relative to hyperglycemia, nor the possible interaction effects, have been well described. We examined the effects of postoperative hypoglycemia, hyperglycemia, and their interaction on short-term morbidity and mortality. METHODS: Single-institution Society of Thoracic Surgeons (STS) database patient records from 2010 to 2014 were merged with clinical data, including blood glucose values measured in the intensive care unit (ICU). Exclusion criteria included fewer than three glucose measurements and absence of an STS predicted risk of morbidity or mortality score. Primary outcomes were operative mortality and composite major morbidity (permanent stroke, renal failure, prolonged ventilation, pneumonia, or myocardial infarction). Secondary outcomes included ICU and postoperative length of stay. Hypoglycemia was defined as below 70 mg/dL, and hyperglycemia as above 180 mg/dL. Simple and multivariable regression models were used to evaluate the outcomes. RESULTS: A total of 2,285 patient records met the selection criteria for analysis. The mean postoperative glucose level was 140.8 ± 18.8 mg/dL. Overall, 21.4% of patients experienced a hypoglycemic episode (n = 488), and 1.05% (n = 24) had a severe hypoglycemic episode (<40 mg/dL). The unadjusted odds ratio (UOR) for operative mortality for patients with any hypoglycemic episode compared with those without was 5.47 (95% confidence interval [CI] 3.14 to 9.54), and the UOR for major morbidity was 4.66 (95% CI 3.55 to 6.11). After adjustment for predicted risk of morbidity or mortality and other significant covariates, the adjusted odds (AOR) of operative mortality were significant for patients with any hypoglycemia (AOR 4.88, 95% CI 2.67 to 8.92) and patients with both events (AOR 8.29, 95% CI 1.83 to 37.5) but not hyperglycemia alone (AOR 1.62, 95% CI 0.56 to 4.69). The AOR of major morbidity for patients with both hypoglycemic and hyperglycemic events was 14.3 (95% CI 6.50 to 31.4). CONCLUSIONS: Postoperative hypoglycemia is associated with both mortality and major morbidity after cardiac operations. The combination of both hyperglycemia and hypoglycemia represents a substantial increase in risk. Although it remains unclear whether hypoglycemia is a cause, an early warning sign, or a result of adverse events, this study suggests that hypoglycemia may be an important event in the postoperative period after cardiac operations.

B-Cell Depletion Promotes Aortic Infiltration of Immunosuppressive Cells and Is Protective of Experimental Aortic Aneurysm.

OBJECTIVE: B-cell depletion therapy is widely used for treatment of cancers and autoimmune diseases. B cells are abundant in abdominal aortic aneurysms (AAA); however, it is unknown whether B-cell depletion therapy affects AAA growth. Using experimental models of murine AAA, we aim to examine the effect of B-cell depletion on AAA formation. APPROACH AND RESULTS: Wild-type or apolipoprotein E-knockout mice were treated with mouse monoclonal anti-CD20 or control antibodies and subjected to an elastase perfusion or angiotensin II infusion model to induce AAA, respectively. Anti-CD20 antibody treatment significantly depleted B1 and B2 cells, and strikingly suppressed AAA growth in both models. B-cell depletion resulted in lower circulating IgM levels, but did not affect the levels of IgG or cytokine/chemokine levels. Although the total number of leukocyte remained unchanged in elastase-perfused aortas after anti-CD20 antibody treatment, the number of B-cell subtypes was significantly lower. Interestingly, plasmacytoid dendritic cells expressing the immunomodulatory enzyme indole 2,3-dioxygenase were detected in the aortas of B-cell-depleted mice. In accordance with an increase in indole 2,3-dioxygenase+ plasmacytoid dendritic cells, the number of regulatory T cells was higher, whereas the expression of proinflammatory genes was lower in aortas of B-cell-depleted mice. In a coculture model, the presence of B cells significantly lowered the number of indole 2,3-dioxygenase+ plasmacytoid dendritic cells without affecting total plasmacytoid dendritic cell number. CONCLUSIONS: The present results demonstrate that B-cell depletion protects mice from experimental AAA formation and promotes emergence of an immunosuppressive environment in aorta.

Enteral Access is not Required for Esophageal Cancer Patients Undergoing Neoadjuvant Therapy.

BACKGROUND: The nutritional status of esophageal cancer patients during neoadjuvant therapy remains a challenging problem. The objective of this study was to determine whether routine enteral feeding tube placement improved nutritional status and perioperative outcomes for patients undergoing neoadjuvant therapy for esophageal cancer. METHODS: The Society of Thoracic Surgeons database was used to identify patients who underwent neoadjuvant therapy and esophagectomy at our institution between 2010 and 2014. Nutritional status before and after neoadjuvant therapy was determined through standardized nutrition consultations. Predictors of change in nutrition and adverse events were evaluated with multivariable and univariate logistic regressions. RESULTS: Two hundred thirty-four esophagectomy patients were identified, and 127 (54%) received neoadjuvant therapy. Of those receiving neoadjuvant therapy, 80% (102/127) presented with dysphagia, and 48% (61/127) received enteral feeding access (EA). Multivariable regression revealed that high initial albumin level, high initial body mass index, and presence of EA were associated with nutritional stability during neoadjuvant therapy. However, 27.9% (17/61) of patients who received EA did not use their access at all or did not use it consistently during the course of preoperative treatment. The preoperative grades of malnutrition and esophagectomy outcomes were similar between groups (EA vs no EA). CONCLUSIONS: EA is associated with improved nutritional status for patients undergoing neoadjuvant therapy for esophageal cancer. However, adverse events and suboptimal use are common. Esophagectomy outcomes were similar for patients with and without EA. These results support judicious patient selection for EA, expedited neoadjuvant therapy, and close collaboration with nutritionists.

Minimally Invasive Mitral Valve Surgery Provides Excellent Outcomes Without Increased Cost: A Multi-Institutional Analysis.

BACKGROUND: Minimally invasive mitral valve surgery (mini-MVR) has grown in popularity. Although single centers have reported excellent outcomes, data on real-world outcomes and costs of mini-MVR are limited. Moreover, mini-MVR has been criticized as adding additional cost without clear benefit. We hypothesized that mini-MVR provides superior outcomes with incremental increased costs in a multi-institutional cohort. METHODS: Records for patients undergoing mitral valve surgical procedures with or without atrial ablation from 2011 to 2014 were extracted from a multi-institutional, regional Society of Thoracic Surgeons database and stratified according to right chest approach/minimally invasive or conventional sternotomy. Patients undergoing coronary artery bypass grafting or other concomitant procedures were excluded. Patients undergoing isolated mitral surgical procedure were propensity matched according to factors, including age, comorbidities, and preoperative laboratory values; clinical outcomes and cost differences were assessed by approach. RESULTS: A total of 1,304 patients underwent mitral operations, including 425 (32.6%) by minimally invasive approach. In the propensity-matched analysis (n = 355 per group), patients undergoing mini-MVR had similar rates of mortality, stroke, and other complications compared with conventional MVR. Meanwhile, patients with mini-MVR experienced shorter intensive care unit and hospital lengths of stay and fewer transfusions. Importantly, total hospital costs were no different between the two matched groups. CONCLUSIONS: Compared with conventional sternotomy, mini-MVR in the "real world" demonstrated no differences in rates of major morbidity, but it was associated with shorter length of stay and fewer transfusions. Contrary to our hypothesis, mini-MVR can be performed with similar total hospital costs as conventional sternotomy. In summary, minimally invasive mitral surgical procedure in select patients can provide superior outcomes without increased cost.

Minimally Invasive Atrial Fibrillation Surgery: Hybrid Approach.

Atrial fibrillation is a challenging pathologic process. There continues to be a great need for the development of a reproducible, durable cure when medical management has failed. An effective, minimally invasive, sternal-sparing intervention without the need for cardiopulmonary bypass is a promising treatment approach. In this article, we describe a hybrid technique being refined at our center that combines a thoracoscopic epicardial surgical approach with an endocardial catheter-based procedure. We also discuss our results and review the literature describing this unique treatment approach.

Current state of transcatheter mitral valve repair with the MitraClip.

BACKGROUND: Many patients affected with mitral valve regurgitation suffer from multiple comorbidities. The MitraClip device provides a safe means of transcatheter valve repair in patients with suitable mitral valve anatomy who are at prohibitive risk for surgery. We describe our early procedural outcomes and present a summary of the current state of MitraClip technology in the United States. METHODS: We performed a retrospective chart review of initial high-risk or inoperable patients who underwent MitraClip placement at our institution after completion of the EVEREST II study. We examined the primary outcome of 30-day mortality, and secondary outcomes included extent of reduction of mitral regurgitation (MR), New York Heart Association (NYHA) functional class improvement, length of stay, and major complications. RESULTS: A total of 115 high-risk patients (mean Society of Thoracic Surgeons predicted risk of mortality 9.4%±6.1%) underwent the MitraClip procedure at our institution between March 2009 and April 2014. Co-morbidities including coronary artery disease (67.8%), pulmonary disease (39.1%) and previous cardiac surgery (44.3%) were common. The device was placed successfully in all patients with a 30-day mortality of 2.6%. All patients demonstrated 3+ or 4+ MR on preoperative imaging, and 80.7% of patients had trace or 1+ MR at hospital discharge. NYHA class improved substantially, with 79% of patients exhibiting class III or IV symptoms pre-procedure and 81% reporting class I or II symptoms at one month follow-up. CONCLUSIONS: The MitraClip procedure provides a safe alternative to surgical or medical management for high-risk patients with MR and suitable valve anatomy. A comprehensive heart team approach is essential, with surgeons providing critical assessment of patient suitability for surgery versus percutaneous therapy as well as performance of the valve procedure.

Hybrid thoracoscopic epicardial and catheter-based endocardial ablation for atrial fibrillation.

Treatment of atrial fibrillation (AF) has evolved substantially, from open surgical 'cut-and-sew' procedures to catheter ablations to minimally invasive ablation with novel energy sources. Recurrences present a significant challenge, both to clinicians and to patients who seek a durable result and freedom from antiarrhythmic medications. Our centre performs a minimally invasive bilateral thoracoscopic epicardial ablation and atrial appendage exclusion, followed by a catheter-based endocardial electrophysiology study and ablation. Results demonstrate favourable outcomes with improvement over catheter-based ablation alone or thoracoscopic ablation alone. We will describe our surgical approach, mid-term results and a brief review of the literature surrounding this dual-modality approach to AF ablation.

Three-dimensional laser flow measurements of a patient-specific fontan physiology with mechanical circulatory assistance.

Mechanical assistance of the Fontan circulation is hypothesized to enhance ventricular preload and improve cardiac output; however, little is known about the fluid dynamics. This study is the first to investigate the three-dimensional flow conditions of a blood pump in an anatomic Fontan. Laser measurements were conducted having an axial flow impeller in the inferior vena cava. Experiments were performed for a physiologic cardiac output, pulmonary arterial flows, and pump speeds of 1000-4000 rpm. The impeller had a modest effect on the flow conditions entering the total cavopulmonary connection at low pump speeds, but a substantial impact on the velocity at higher speeds. The higher speeds of the pump disrupted the recirculation region in the center of the anastomosis, which could be advantageous for washout purposes. No retrograde velocities in the superior vena cava were measured. These findings indicate that mechanical assistance is a viable therapeutic option for patients having dysfunctional single ventricle physiology.

Impact of hemodynamic monitoring on clinical outcomes.

In recent years, there has been a tremendous growth in available hemodynamic monitoring devices to support clinical decision-making in the operating room and intensive care unit. In addition to the "tried and true" heart rate and blood pressure monitors, there are several newer applications of existing technologies including arterial waveform analysis, intraoperative and bedside critical care echocardiography, esophageal Doppler, and tissue oximetry, among others. Several monitoring devices demonstrate positive effect on outcomes, especially when used in conjunction with specific goal-directed therapy protocols to achieve a desired clinical effect. Other devices remain in the validation stage, awaiting comprehensive comparison to established techniques. While these new technologies offer promising advances in intraoperative and critical care, they are often quite costly and many devices lack strong evidence for widespread adoption into clinical practice. In this review, we highlight the current data on clinical outcomes with the use of available hemodynamic monitoring devices.

A viable therapeutic option: mechanical circulatory support of the failing Fontan physiology.

A blood pump specifically designed to augment flow from the great veins through the lungs would ameliorate the poor physiology of the failing univentricular circulation and result in a paradigm shift in the treatment strategy for Fontan patients. This study is the first to examine mechanical cavopulmonary assistance with a blood pump in the inferior vena cava (IVC) and hepatic blood flow. Five numerical models of mechanical cavopulmonary assistance were investigated using a three-dimensional, reconstructed, patient-specific Fontan circulation from magnetic resonance imaging data. Pressure flow characteristics of the axial blood pump, energy augmentation calculations for the cavopulmonary circulation with and without pump support, and hemolysis estimations were determined. In all of the pump-supported scenarios, a pressure increase of 7-9.5 mm Hg was achieved. The fluid power of the cavopulmonary circulation was also positive over the range of flow rates. No retrograde flow from the IVC into the hepatic circulation was evident during support cases. Vessel suction risk, however, was found for greater operating rotational speeds. Fluid shear stresses and hemolysis predictions remained at acceptable levels with normalized index of hemolysis estimations at 0.0001 g/100 L. The findings of this study support the continued design and development of this blood pump technology for Fontan patients with progressive cardiovascular insufficiency. Validation of these flow and performance predictions will be completed in the next round of experimental testing with blood bag evaluation.

Steady flow analysis of mechanical cavopulmonary assistance in MRI-derived patient-specific fontan configurations.

This numerical study examined the performance of an intravascular axial flow blood pump for mechanical hemodynamic support of patients in the setting of Fontan failure, which presently has few treatment options. Three anatomically accurate geometries of the total cavopulmonary connection (TCPC) were generated using patients' magnetic resonance imaging data. These patient-specific geometries, as well as an idealized version with cylindrical vessels, were computationally analyzed with and without a pump in the inferior vena cava. Pressure flow characteristics, energy gain calculations, and blood damage analyses were performed for each model. The pump produced pressures of 1-14 mm Hg for 1500-4000 revolutions per minute, flow rates of 1-4 L/min, and pulmonary artery pressures of 8-24 mm Hg. Comparison of pump performance among the four models showed minimal intermodel differences (<5% deviation) in the pressure rise generated by the pump, the IVC pressure, and the energy imparted to the system by the pump. Blood damage analysis showed maximum fluid scalar stress values of 372 Pa or less, and the blood damage index was less than 2% in all of the models. These results suggest that this axial flow blood pump performs consistently in a variety of TCPC vessel geometries with low risk of blood trauma.

Controlled pitch-adjustment of impeller blades for an intravascular blood pump.

Thousands of mechanical blood pumps are currently providing circulatory support, and the incidence of their use continues to increase each year. As the use of blood pumps becomes more pervasive in the treatment of those patients with congestive heart failure, critical advances in design features to address known limitations and the integration of novel technologies become more imperative. To advance the current state-of-the-art in blood pump design, this study investigates the inclusion of pitch-adjusting blade features in intravascular blood pumps as a means to increase energy transfer; an approach not explored to date. A flexible impeller prototype was constructed with a configuration to allow for a variable range of twisted blade geometries of 60-250°. Hydraulic experiments using a blood analog fluid were conducted to characterize the pressure-flow performance for each of these twisted positions. The flexible, twisted impeller was able to produce 1-25 mmHg for 0.5-4 L/min at rotational speeds of 5,000-8,000 RPM. For a given twisted position, the pressure rise was found to decrease as a function of increasing flow rate, as expected. Generally, a steady increase in the pressure rise was observed as a function of higher twisted degrees for a constant rotational speed. Higher rotational speeds for a specific twisted impeller configuration resulted in a more substantial pressure generation. The findings of this study support the continued exploration of this unique design approach in the development of intravascular blood pumps.

Twisted cardiovascular cages for intravascular axial flow blood pumps to support the Fontan physiology.

Failing single ventricle physiology represents an ongoing challenge in mechanical assist device development, requiring pressure augmentation in the cavopulmonary circuit, reduction of systemic venous pressure, and increased cardiac output to achieve hemodynamic stabilization. To meet these requirements, we are developing a percutaneously-placed, axial flow blood pump to support ailing single ventricle physiology in adolescents and adults. We have modified the outer cage of the device to serve as both a protective and functional design component. This study examined the performance of 3 cage geometries with varying directions of filament twist using numerical simulations and hydraulic experiments. All 3 cage and pump models performed in acceptable ranges to support Fontan patients. The cage design employing filaments that are twisted in the opposite direction to the impeller blades and in the direction of the diffuser blades (against-with) demonstrated superior performance by generating a pressure rise range of 5-38 mmHg of flow rates of 0.5-6 l/min at rotational speeds of 5000-7000 rpm. The blood damage indices for all of the cages were found to be well below 2%, and the scalar stress levels were below 200 Pa. This study represents ongoing progress in the development of the impeller and cage assembly. Validation of the results will continue in experiments with blood bag evaluation as well as by particle image velocimetry measurements.