Large-bore Mechanical Thrombectomy Versus Catheter-directed Thrombolysis in the Management of Intermediate-risk Pulmonary Embolism: Primary Results of the PEERLESS Randomized Controlled Trial.

BACKGROUND: There is a lack of randomized controlled trial (RCT) data comparing outcomes of different catheter-based interventions for intermediate-risk pulmonary embolism (PE). METHODS: PEERLESS is a prospective, multicenter, RCT that enrolled 550 intermediate-risk PE patients with right ventricular dilatation and additional clinical risk factors randomized 1:1 to treatment with large-bore mechanical thrombectomy (LBMT) or catheter-directed thrombolysis (CDT). The primary endpoint was a hierarchal win ratio (WR) composite of the following: 1) all-cause mortality, 2) intracranial hemorrhage, 3) major bleeding, 4) clinical deterioration and/or escalation to bailout, and 5) postprocedural intensive care unit (ICU) admission and length of stay, assessed at the sooner of hospital discharge or 7 days post-procedure. Assessments at the 24-hour visit included respiratory rate, mMRC dyspnea score, NYHA classification, right ventricle (RV)/left ventricle (LV) ratio reduction, and RV function. Endpoints through 30 days included total hospital stay, all-cause readmission, and all-cause mortality. RESULTS: The primary endpoint occurred significantly less frequently with LBMT vs CDT (WR 5.01 [95% CI: 3.68-6.97]; P<0.001). There were significantly fewer episodes of clinical deterioration and/or bailout (1.8% vs 5.4%; P=0.04) with LBMT vs CDT and less postprocedural ICU utilization (P<0.001), including admissions (41.6% vs 98.6%) and stays >24 hours (19.3% vs 64.5%). There was no significant difference in mortality, intracranial hemorrhage, or major bleeding between strategies, nor in a secondary WR endpoint including the first 4 components (WR 1.34 [95% CI: 0.78-2.35]; P=0.30). At the 24-hour visit, respiratory rate was lower for LBMT patients (18.3±3.3 vs 20.1±5.1; P<0.001) and fewer had moderate to severe mMRC dyspnea scores (13.5% vs 26.4%; P<0.001), NYHA classifications (16.3% vs 27.4%; P=0.002), and RV dysfunction (42.1% vs 57.9%; P=0.004). RV/LV ratio reduction was similar (0.32±0.24 vs 0.30±0.26; P=0.55). LBMT patients had shorter total hospital stays (4.5±2.8 vs 5.3±3.9 overnights; P=0.002) and fewer all-cause readmissions (3.2% vs 7.9%; P=0.03), while 30-day mortality was similar (0.4% vs 0.8%; P=0.62). CONCLUSIONS: PEERLESS met its primary endpoint in favor of LBMT vs CDT in treatment of intermediate-risk PE. LBMT had lower rates of clinical deterioration and/or bailout and postprocedural ICU utilization compared with CDT, with no difference in mortality or bleeding.

Rates and impact of vascular complications in mechanical circulatory support.

BACKGROUND: Mechanical circulatory support (MCS) devices are increasingly used for hemodynamic support in cardiogenic shock or high-risk percutaneous coronary interventions. Vascular complications remain a major source of morbidity and mortality despite technological advances with percutaneous techniques. Little is known about the rates and predictors of vascular complications with large-bore access MCS in the contemporary era. METHODS: The study cohort was derived from National Inpatient Sample using data from 2015 to 2019 for cardiac hospitalizations with the use of: intra-aortic balloon pump (IABP) Impella, and/or extracorporeal membrane oxygenation (ECMO). The rates of vascular complications and in-hospital outcomes were analyzed using multivariable logistic regression. RESULTS: Of 221,700 hospitalizations with MCS use, the majority had only IABP (68%). The rates of vascular complications were greatest with ECMO (15.8%) when compared with IABP (3.0%) and Impella (5.6%). Among patients with vascular complications, in-hospital mortality was higher with ECMO (56.3%) when compared with IABP (26.2%) and Impella (33.8%). Peripheral arterial disease (PAD) was the strongest predictor of vascular complications, with 10 times higher odds when present (adjusted odds ratio [aOR] 10.96, p < 0.001). In risk-adjusted models, when compared with IABP, the use of Impella (aOR: 1.73, p < 0.001), ECMO (aOR: 5.35, p < 0.001), or a combination of MCS devices (aOR: 3.47, p < 0.001) was associated with higher odds of vascular complications. CONCLUSIONS: In contemporary practice, the use of MCS is associated with significant vascular complications and in-hospital mortality. Predictors of vascular complications include larger arteriotomy size, female gender, and peripheral arterial disease. Vascular access management remains essential to prevent major complications.

Vasopressors independently associated with mortality in acute myocardial infarction and cardiogenic shock.

BACKGROUND: Increasing vasopressor dose is associated with increasing mortality in patients presenting with acute myocardial infarction and cardiogenic shock (AMICS). It is unknown whether the use of vasopressors is independently harmful or if their use is secondary to decreasing intrinsic cardiac power output (CPO). Mechanical circulatory support (MCS) devices enhance CPO. We sought to evaluate the independent impact of increasing vasopressor dose on survival in the National Cardiogenic Shock Initiative (NCSI). METHODS: The NCSI is a single arm prospective trial evaluating outcomes associated with the use of MCS using Impella in patients with AMICS. Early initiation of MCS placement before percutaneous coronary intervention (PCI) and rapid de-escalation of vasopressors guided by systematic use of invasive hemodynamic measures led to 70% in-hospital survival for the first 300 patients enrolled from July 2016 to December 2019 in 57 U.S. sites. RESULTS: Hemodynamic measures were obtained immediately after MCS and PCI. Survival curves were constructed based on CPO and use of vasopressors. For patients with CPO ≤0.6 W, survival was 77.3%, 45.0%, and 35.3% when 0, 1, or ≥ 2 vasopressors were used (p = 0.02). Similarly, for patients with CPO >0.6 W survival was 81.7%, 72.6%, and 56.8%, respectively (p = 0.01). Logistic regression analysis demonstrated that increasing vasopressor requirements were independently associated with increasing mortality (p = 0.02). CONCLUSION: Increasing vasopressor requirement is associated with increased mortality in AMICS independent of underlying CPO. Methods to decrease the need for vasopressors may enhance survival in AMICS.

Endovascular Removal of Thrombus and Right Heart Masses Using the AngioVac System: Results of 234 Patients from the Prospective, Multicenter Registry of AngioVac Procedures in Detail (RAPID).

PURPOSE: To assess device and procedural safety and technical success associated with the use of the AngioVac System to remove vascular thrombi and cardiac masses. MATERIALS AND METHODS: The Registry of AngioVac Procedures in Detail (RAPID) study prospectively collected data for 234 patients receiving treatment with AngioVac at 21 sites between March 2016 and August 2019: 84 (35.9%) with caval thromboemboli (CTEs), 113 (48.3%) with right heart masses (RHMs), 20 (8.5%) with catheter-related thrombi (CRTs), and 4 (1.7%) with pulmonary emboli (PEs). Thirteen patients had a combination of procedures during the same admission. RESULTS: Using the AngioVac system, 70%-100% thrombus or mass removal was achieved in 73.6% of patients with CTEs, 58.5% of patients with RHMs, 60% of patients with CRTs, and 57.1% of patients with PEs. Extracorporeal bypass time was < 1 hour for 176 (75.2%) procedures. Estimated blood loss was < 250 mL for 179 procedures (76.5%). Mean hemoglobin decreased from 10.4 g/dL ± 2.9 preoperatively to 9.4 g/dL ± 2.6 postoperatively. Transfusions were administered in 59 procedures (25.2%) with 47 transfusions (78.2%) being ≤ 2 U. There were 36 procedure-related complications, including 1 death. CONCLUSIONS: The RAPID registry data demonstrate that the AngioVac System can be safely and effectively used to remove vascular thrombi and cardiac masses across a broad range of patient populations. The limited use of the device to remove pulmonary emboli in the present series precludes recommending the use of the AngioVac device for this indication.

Improved Outcomes Associated with the use of Shock Protocols: Updates from the National Cardiogenic Shock Initiative.

BACKGROUND: The National Cardiogenic Shock Initiative is a single-arm, prospective, multicenter study to assess outcomes associated with early mechanical circulatory support (MCS) in patients presenting with acute myocardial infarction and cardiogenic shock (AMICS) treated with percutaneous coronary intervention (PCI). METHODS: Between July 2016 and February 2019, 35 sites participated and enrolled into the study. All centers agreed to treat patients with AMICS using a standard protocol emphasizing invasive hemodynamic monitoring and rapid initiation of MCS. Inclusion and exclusion criteria mimicked those of the "SHOCK" trial with an additional exclusion criteria of intra-aortic balloon pump counter-pulsation prior to MCS. RESULTS: A total of 171 consecutive patients were enrolled. Patients had an average age of 63 years, 77% were male, and 68% were admitted with AMICS. About 83% of patients were on vasopressors or inotropes, 20% had a witnessed out of hospital cardiac arrest, 29% had in-hospital cardiac arrest, and 10% were under active cardiopulmonary resuscitation during MCS implantation. In accordance with the protocol, 74% of patients had MCS implanted prior to PCI. Right heart catheterization was performed in 92%. About 78% of patients presented with ST-elevation myocardial infarction with average door to support times of 85 ± 63 min and door to balloon times of 87 ± 58 min. Survival to discharge was 72%. Creatinine ≥2, lactate >4, cardiac power output (CPO) <0.6 W, and age ≥ 70 years were predictors of mortality. Lactate and CPO measurements at 12-24 hr reliably predicted overall mortality postindex procedure. CONCLUSION: In contemporary practice, use of a shock protocol emphasizing best practices is associated with improved outcomes.

Combined carotid endarterectomy and transcatheter aortic valve replacement: Technique and outcomes.

BACKGROUND: Stroke and transient ischemic attack after transcatheter aortic valve replacement results in significantly higher morbidity and mortality. Severe carotid artery disease may be a contributing factor to this increased risk. We report our technique and outcomes of combined carotid endarterectomy (CEA) with transcatheter aortic valve replacement (TAVR). METHODS: From March 2013 to November 2017 a total of 753 TAVRs were performed at our institution for symptomatic severe aortic stenosis. Of this group, 16 patients underwent concomitant TAVR and CEA. A retrospective review was performed to assess risk, outcomes, and short-term survival. RESULTS: Sixteen patients underwent concomitant CEA/TAVR procedures for severe carotid and severe aortic stenosis. The mean Society of Thoracic Surgeons (STS) Risk Score was 7.0 ± 4.7. All patients had severe carotid artery stenosis and aortic stenosis. Nine patients had a transfemoral TAVR approach and eight patients had a transapical TAVR approach. The mean length of stay was 6.4 ± 3.7 days. At 30 days there were no cerebrovascular events and no mortalities. CONCLUSIONS: The use of concomitant CEA and TAVR in patients with severe aortic stenosis and severe carotid stenosis can be done safely without increased risk of complications. This approach may reduce the risk of stroke associated with TAVR in appropriately selected patients.

Early Utilization of Mechanical Circulatory Support in Acute Myocardial Infarction Complicated by Cardiogenic Shock: The National Cardiogenic Shock Initiative.

BACKGROUND: Acute myocardial infarction complicated by cardiogenic shock (AMI-CS) is associated with significant morbidity and mortality. Mechanical circulatory support (MCS) devices increase systemic blood pressure and end organ perfusion while reducing cardiac filling pressures. METHODS AND RESULTS: The National Cardiogenic Shock Initiative (NCT03677180) is a single-arm, multicenter study. The purpose of this study was to assess the feasibility and effectiveness of utilizing early MCS with Impella in patients presenting with AMI-CS. The primary end point was in-hospital mortality. A total of 406 patients were enrolled at 80 sites between 2016 and 2020. Average age was 64±12 years, 24% were female, 17% had a witnessed out-of-hospital cardiac arrest, 27% had in-hospital cardiac arrest, and 9% were under active cardiopulmonary resuscitation during MCS implantation. Patients presented with a mean systolic blood pressure of 77.2±19.2 mm Hg, 85% of patients were on vasopressors or inotropes, mean lactate was 4.8±3.9 mmol/L and cardiac power output was 0.67±0.29 watts. At 24 hours, mean systolic blood pressure improved to 103.9±17.8 mm Hg, lactate to 2.7±2.8 mmol/L, and cardiac power output to 1.0±1.3 watts. Procedural survival, survival to discharge, survival to 30 days, and survival to 1 year were 99%, 71%, 68%, and 53%, respectively. CONCLUSIONS: Early use of MCS in AMI-CS is feasible across varying health care settings and resulted in improvements to early hemodynamics and perfusion. Survival rates to hospital discharge were high. Given the encouraging results from our analysis, randomized clinical trials are warranted to assess the role of utilizing early MCS, using a standardized, multidisciplinary approach.

Balloon aortic valvuloplasty for aortic stenosis using a novel percutaneous dilation catheter and power injector.

Calcific aortic stenosis is the most common valvular heart disease in the Western world. Although definitive treatment is valve replacement, many patients are not replacement candidates due to high surgical risk from older age and comorbid illness or lack of desire for a surgical or replacement procedure. Percutaneous balloon aortic valvuloplasty (BAV) is an option for palliative treatment in nonsurgical patients, although this procedure is complicated during the immediate postprocedure period by bleeding requiring transfusion for about 1 in 5 patients and subsequent restenosis. This report describes BAV using a smaller profile balloon designed to withstand higher pressures, rapidly inflated with a power injector. Twenty consecutive high-risk patients with severe aortic stenosis were treated. In all cases, New York Heart Association (NYHA) class improved from IV before BAV to I or II at 30 days follow-up. Six-month posttreatment follow-up data were available for 19 of 20 patients: 15 patients were either NYHA class I or II, 1 patient was class III, and 3 deaths occurred unrelated to aortic stenosis. One patient was lost to follow-up. Average systolic gradient peak-to-peak pressure decreased by 40.0% (range 18.0-70.0%) and mean gradient decreased by 30.0% (range 13.7-70.8%). Aortic valve area increased from 0.59 ± 0.16 cm(2) to 0.92 ± 0.23 cm(2), representing a mean increase of 30.0% (range 7.8%-58.2%). There were no significant bleeding complications. The only procedural complication was a single case of pericardial tamponade. There were no other complications during the first 24 hours post-BAV. These data support that the reported BAV technique may offer an effective alternative for patients with severe aortic stenosis who are not surgical candidates or prefer to avoid aortic valve replacement.

Impact of transcatheter aortic valve replacement on left ventricular hypertrophy, diastolic dysfunction and quality of life in patients with preserved left ventricular function.

Severe aortic stenosis (AS) is associated with left ventricular (LV) hypertrophy and diastolic dysfunction (LVDD). Due to positive impact on transvalvular hemodynamics, transcatheter aortic valve replacement (TAVR) is expected to improve LV remodeling, LVDD and heart failure (HF)-related quality-of-life (QoL). We identified patients with severe AS and LV ejection fraction (LVEF) ≥ 50% who underwent TAVR. We reviewed pre-procedure, 1-month and 1-year post-TAVR transthoracic echocardiograms to assess LV volumetric changes and diastolic function. QoL was assessed by the Kansas City Cardiomyopathy Questionnaire (KCCQ). In 171 patients studied, we found significant improvement in LV mass index (LVMI), LV end-systolic diameter and LV end-diastolic diameter from baseline to 1-month to 1-year post-TAVR. Predictors of LVMI regression included greater change from baseline in mean aortic valve (AV) gradient, peak AV velocity, and improvements in septal and lateral e' velocities and E/e' post-TAVR. The percentage of patients with ≥ grade 2 LVDD decreased from 65% to 53% at 1-month and 49% at 1-year. A significant improvement in symptomatology, as reported by KCCQ score was also noted. There is conceivable reverse LV remodeling post-TAVR, impacted by improvements in mean AV gradient, peak AV velocity, E/e', medial and lateral e' velocities, which occurs immediately post-TAVR and persists up to 1-year post-operatively. This is associated with concomitant improvement in LVDD and HF-related QoL as demonstrated by KCCQ scores.

Tip-to-Base LAMPOON for Transcatheter Mitral Valve Replacement With a Protected Mitral Annulus.

OBJECTIVES: The purpose of this study was to evaluate tip-to-base intentional laceration of the anterior mitral leaflet to prevent left ventricular outflow tract obstruction (LAMPOON) in patients undergoing transcatheter mitral valve replacement (TMVR) in annuloplasty rings or surgical mitral valves. BACKGROUND: LAMPOON is an effective adjunct to TMVR that prevents left ventricular outflow tract obstruction (LVOTO). Laceration is typically performed from the base to the tip of the anterior mitral leaflet. A modified laceration technique from leaflet tip to base may be effective in patients with a prosthesis that protects the aortomitral curtain. METHODS: This is a multicenter, 21-patient, consecutive retrospective observational cohort. Patients underwent tip-to-base LAMPOON to prevent LVOTO and leaflet overhang, or therapeutically to lacerate a long anterior mitral leaflet risking or causing LVOTO. Outcomes were compared with findings from patients in the LAMPOON investigational device exemption trial with a prior mitral annuloplasty. RESULTS: Twenty-one patients with a annuloplasty or valve prosthesis-protected mitral annulus underwent tip-to-base LAMPOON (19 preventive, 2 rescue). Leaflet laceration was successful in all and successfully prevented or treated LVOTO in all patients. No patients had significant LVOTO upon discharge. There were 2 cases of unintentional aortic valve injury (1 patient underwent emergency transcatheter aortic valve replacement and 1 patient underwent urgent surgical aortic valve replacement). In both cases, the patients had a supra-annular ring annuloplasty, and the retrograde aortic guiding catheter failed to insulate the guidewire lacerating surface from the aortic root. All patients survived to 30 days. Compared with classic retrograde LAMPOON, there was a trend toward shorter procedure time. CONCLUSIONS: Tip-to-base laceration is a simple, effective, and safe LAMPOON variant applicable to patients with an appropriately positioned mitral annular ring or bioprosthetic valve. Operators should take care to insulate the lacerating surface from adjacent structures.

Multivessel Versus Culprit-Vessel Percutaneous Coronary Intervention in Cardiogenic Shock.

OBJECTIVES: This study sought to compare outcomes of patients enrolled in the NCSI (National Cardiogenic Shock Initiative) trial who were treated using a revascularization strategy of percutaneous coronary intervention (PCI) of multivessel PCI (MV-PCI) versus culprit-vessel PCI (CV-PCI). BACKGROUND: In patients with multivessel disease who present with acute myocardial infarction and cardiogenic shock (AMICS), intervening on the nonculprit vessel is controversial. There are conflicting published reports and lack of evidence, particularly in patients treated with early mechanical circulatory support (MCS). METHODS: From July 2016 to December 2019, patients who presented with AMICS to 57 participating hospitals were included in this analysis. All patients were treated using a standard shock protocol emphasizing early MCS, revascularization, and invasive hemodynamic monitoring. Patients with multivessel coronary artery disease (MVCAD) were analyzed according to whether CV-PCI or MV-PCI was undertaken during the index procedure. RESULTS: Of 198 patients with MVCAD, 126 underwent MV-PCI (64%) and 72 underwent CV-PCI (36%). Demographics between the cohorts were similar with respect to age, sex, history of diabetes, prior PCI or coronary artery bypass grafting, and prior history of myocardial infarction. Patients who underwent MV-PCI had a trend toward more severe impairment of cardiac output and worse lactate clearance on presentation, and cardiac performance was significantly worse at 12 h. However, 24 h from PCI, the hemometabolic derangements were similar. Survival and rates of acute kidney injury were not significantly different between groups (69.8% MV-PCI vs. 65.3% CV-PCI; p = 0.51; and 29.9% vs. 34.2%; p = 0.64, respectively). CONCLUSIONS: In patients with MVCAD presenting with AMICS treated with early MCS, revascularization of nonculprit lesions was associated with similar hospital survival and acute kidney injury when compared with culprit-only PCI. Selective nonculprit PCI can be safety performed in AMICS in patients supported with mechanical circulatory support.

Re-access complication with a Starclose device.

Diagnostic cardiac catheterizations are predominantly performed using access through the femoral artery. To improve patient comfort and early mobilization, a number of percutaneous closure devices have been developed. One such device using the nitinol clip was developed by Abbott Vascular Devices and was approved for use on the basis of the results of the Clip Closure In Percutaneous Procedures (CLIP) study. The safety of repuncture through a previously deployed device has not been established in humans. We present the case of a patient who had an arterial line placed for post-operative monitoring after cardiac surgery at the site of a previous arteriotomy closed with the Starclose device. The catheter traversed through the central portion, tethered to the periphery of the ninitol clip, and required surgery for extraction.

Monitoring Pulmonary Arterial Hypertension Using an Implantable Hemodynamic Sensor.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a chronic disease that ultimately progresses to right-sided heart failure (HF) and death. Close monitoring of pulmonary artery pressure (PAP) and right ventricular (RV) function allows clinicians to appropriately guide therapy. However, the burden of commonly used methods to assess RV hemodynamics, such as right heart catheterization, precludes frequent monitoring. The CardioMEMS HF System (Abbott) is an ambulatory implantable hemodynamic monitor, previously only used in patients with New York Heart Association (NYHA) class III HF. In this study, we evaluate the feasibility and early safety of monitoring patients with PAH and right-sided HF using the CardioMEMS HF System. METHODS: The CardioMEMS HF sensors were implanted in 26 patients with PAH with NYHA class III or IV right-sided HF (51.3 ± 18.3 years of age, 92% women, 81% NYHA class III). PAH therapy was tracked using a minimum of weekly reviews of CardioMEMS HF daily hemodynamic measurements. Safety, functional response, and hemodynamic response were tracked up to 4 years with in-clinic follow-ups. RESULTS: The CardioMEMS HF System was safely used to monitor PAH therapy, with no device-related serious adverse events observed and a single preimplant serious adverse event. Significant PAP reduction and cardiac output elevation were observed as early as 1 month postimplant using trends of CardioMEMS HF data, coupled with significant NYHA class and quality of life improvements within 1 year. CONCLUSIONS: The CardioMEMS HF System provided useful information to monitor PAH therapy, and demonstrated short- and long-term safety. Larger clinical trials are needed before its widespread use to guide therapy in patients with severe PAH with right-sided HF.

Prolonged duration of transbrachial intra-aortic balloon pump as bridge to heart transplantation.

We describe a case demonstrating the quality of life (QOL) benefit and safety of using a transbrachial approach for insertion of an intra-aortic balloon pump (IABP) in a patient awaiting cardiac transplantation. A 68-year-old man with ischaemic cardiomyopathy was admitted to our cardiac intensive care unit to await the availability of a suitable donor organ for orthotopic heart transplant. An IABP was needed for haemodynamic support due to cardiogenic shock. Since the patient did not want to be committed to lying supine in bed for multiple days, as would have been the case had the IABP been placed using the conventional femoral route, we inserted a 7.5 Fr 'sheathless' IABP via the transbrachial approach. The patient's haemodynamics improved and the device was left in place for 240 h without vascular compromise. He was subsequently successfully transplanted and is doing well on follow-up.

Successful treatment of acute left ventricular assist device thrombosis and cardiogenic shock with intraventricular thrombolysis and a tandem heart.

Management for continuous flow left ventricular assist device (LVAD) thrombosis often relies on speculation of individual clinical risk factors and integration of indirect evidence for device dysfunction. There are no comprehensive guidelines for treatment of this serious complication, and most of our current knowledge comes from anecdotal experience or observational study. More data on effective treatment, both with aggressive pharmacologic and device-based interventions, are needed for improving our understanding of mechanisms driving device thrombosis and for preventing future events. We present a case of LVAD thrombosis with emphasis on recognition and treatment of acute pump thrombosis, and discuss a potentially novel strategy using percutaneous mechanical circulatory support for pump salvage.

Patient-specific computational modeling of blood flow in the pulmonary arterial circulation.

Computational fluid dynamics (CFD) modeling of the pulmonary vasculature has the potential to reveal continuum metrics associated with the hemodynamic stress acting on the vascular endothelium. It is widely accepted that the endothelium responds to flow-induced stress by releasing vasoactive substances that can dilate and constrict blood vessels locally. The objectives of this study are to examine the extent of patient specificity required to obtain a significant association of CFD output metrics and clinical measures in models of the pulmonary arterial circulation, and to evaluate the potential correlation of wall shear stress (WSS) with established metrics indicative of right ventricular (RV) afterload in pulmonary hypertension (PH). Right Heart Catheterization (RHC) hemodynamic data and contrast-enhanced computed tomography (CT) imaging were retrospectively acquired for 10 PH patients and processed to simulate blood flow in the pulmonary arteries. While conducting CFD modeling of the reconstructed patient-specific vasculatures, we experimented with three different outflow boundary conditions to investigate the potential for using computationally derived spatially averaged wall shear stress (SAWSS) as a metric of RV afterload. SAWSS was correlated with both pulmonary vascular resistance (PVR) (R(2)=0.77, P<0.05) and arterial compliance (C) (R(2)=0.63, P<0.05), but the extent of the correlation was affected by the degree of patient specificity incorporated in the fluid flow boundary conditions. We found that decreasing the distal PVR alters the flow distribution and changes the local velocity profile in the distal vessels, thereby increasing the local WSS. Nevertheless, implementing generic outflow boundary conditions still resulted in statistically significant SAWSS correlations with respect to both metrics of RV afterload, suggesting that the CFD model could be executed without the need for complex outflow boundary conditions that require invasively obtained patient-specific data. A preliminary study investigating the relationship between outlet diameter and flow distribution in the pulmonary tree offers a potential computationally inexpensive alternative to pressure based outflow boundary conditions.

The role of wall shear stress in the assessment of right ventricle hydraulic workload.

Pulmonary hypertension (PH) is a devastating disease affecting approximately 15-50 people per million, with a higher incidence in women. PH mortality is mostly attributed to right ventricle (RV) failure, which results from RV hypotrophy due to an overburdened hydraulic workload. The objective of this study is to correlate wall shear stress (WSS) with hemodynamic metrics that are generally accepted as clinical indicators of RV workload and are well correlated with disease outcome. Retrospective right heart catheterization data for 20 PH patients were analyzed to derive pulmonary vascular resistance (PVR), arterial compliance (C), and an index of wave reflections (Γ). Patient-specific contrast-enhanced computed tomography chest images were used to reconstruct the individual pulmonary arterial trees up to the seventh generation. Computational fluid dynamics analyses simulating blood flow at peak systole were conducted for each vascular model to calculate WSS distributions on the endothelial surface of the pulmonary arteries. WSS was found to be decreased proportionally with elevated PVR and reduced C. Spatially averaged WSS (SAWSS) was positively correlated with PVR (R (2) = 0.66), C (R (2) = 0.73), and Γ (R (2) = 0.5) and also showed promising preliminary correlations with RV geometric characteristics. Evaluating WSS at random cross sections in the proximal vasculature (main, right, and left pulmonary arteries), the type of data that can be acquired from phase-contrast magnetic resonance imaging, did not reveal the same correlations. In conclusion, we found that WSS has the potential to be a viable and clinically useful noninvasive metric of PH disease progression and RV health. Future work should be focused on evaluating whether SAWSS has prognostic value in the management of PH and whether it can be used as a rapid reactivity assessment tool, which would aid in selection of appropriate therapies.