Microaxial Flow Pump or Standard Care in Infarct-Related Cardiogenic Shock.

BACKGROUND: The effects of temporary mechanical circulatory support with a microaxial flow pump on mortality among patients with ST-segment elevation myocardial infarction (STEMI) complicated by cardiogenic shock remains unclear. METHODS: In an international, multicenter, randomized trial, we assigned patients with STEMI and cardiogenic shock to receive a microaxial flow pump (Impella CP) plus standard care or standard care alone. The primary end point was death from any cause at 180 days. A composite safety end point was severe bleeding, limb ischemia, hemolysis, device failure, or worsening aortic regurgitation. RESULTS: A total of 360 patients underwent randomization, of whom 355 were included in the final analysis (179 in the microaxial-flow-pump group and 176 in the standard-care group). The median age of the patients was 67 years, and 79.2% were men. Death from any cause occurred in 82 of 179 patients (45.8%) in the microaxial-flow-pump group and in 103 of 176 patients (58.5%) in the standard-care group (hazard ratio, 0.74; 95% confidence interval [CI], 0.55 to 0.99; P = 0.04). A composite safety end-point event occurred in 43 patients (24.0%) in the microaxial-flow-pump group and in 11 (6.2%) in the standard-care group (relative risk, 4.74; 95% CI, 2.36 to 9.55). Renal-replacement therapy was administered to 75 patients (41.9%) in the microaxial-flow-pump group and to 47 patients (26.7%) in the standard-care group (relative risk, 1.98; 95% CI, 1.27 to 3.09). CONCLUSIONS: The routine use of a microaxial flow pump with standard care in the treatment of patients with STEMI-related cardiogenic shock led to a lower risk of death from any cause at 180 days than standard care alone. The incidence of a composite of adverse events was higher with the use of the microaxial flow pump. (Funded by the Danish Heart Foundation and Abiomed; DanGer Shock ClinicalTrials.gov number, NCT01633502.).

Revisiting Pulmonary Hypertension in the Era of Temporary Mechanical Circulatory Support - Literature Review and Case-Based Discussion.

BACKGROUND: Pulmonary arterial hypertension (PAH) is characterized by persistently increased pressure in the pulmonary arteries. New defining criteria for the different hemodynamic types of pulmonary hypertension (PH) that occur with left heart disease have been proposed by the task force on PH. After consideration of the changes in the general definition of PH in left heart disease, the proposed hemodynamic definition was: (1) isolated postcapillary PH: pulmonary artery wedge pressure >15 mm Hg and mean pulmonary arterial pressure (mPAP) >20 mm Hg and pulmonary vascular resistance (PVR) <3 Woods units (WU); and (2) combined post- and precapillary PH: pulmonary artery wedge pressure >15 mm Hg, mPAP >20 mm Hg, and PVR ≥3 WU. Secondary PH is initially reversible, but eventually, it can become fixed because of the remodeling process of the pulmonary vascular system. Limitations in defining both the time for and amount of reversibility lack clarity. We discuss a case of PH as a framework to better understand these key principles in addressing patients' candidacy for heart or heart-lung transplantation. METHODS: We performed a literature search for all available contemporary data with the following terms: "pulmonary hypertension," "reversal," "Impella 5.5," "temporary mechanical support," and "LVAD" using the National Library of Medicine - PubMed and PubMed Central between 2019 and 2023. A total of 14 published papers were found with these search. From these, 3 addressed the issue of PH and reversibility in the setting of LHD after durable LVAD placement. No papers were found using Impella 5.5 and PH during this timeframe. Given the paucity of data in the field regarding temporary mechanical circulatory support and pulmonary hypertension, we present a case-based discussion to guide the reader in understanding the potential impact of this method in patients with WHO Class 2 Pulmonary hypertension. CASE: A 49-year-old woman with a medical history of acute on chronic biventricular systolic and diastolic heart failure, American College of Cardiology stage D, Stevenson profile C, New York Heart Association class IV (ejection fraction 18%) secondary to nonischemic cardiomyopathy after cardiac resynchronization therapy, pulmonary hypertension, bilateral deep vein thrombosis, and segmental pulmonary embolism presented for heart transplant evaluation. Her cardiac output and central hemodynamics were measured, and she was found to have a pulmonary artery (PA) pressure of 78/38 with a mean PA pressure of 51, pulmonary capillary wedge pressure (PCWP) 30, transpulmonary pressure gradient (TPG) 21, thermodilution cardiac output (CO) 3.35 L/min, and cardiac input (CI) 1.75 L/min/m2. Her PVR was 6.2 WU. Provocative pharmacologic testing for reversibility of PH was performed using sodium nitroprusside, which resulted in a blood pressure of 83/57 (92), heart rate 92/min, and PA pressure of 71/31, with a mean PA pressure of 44 PCWP 22, TPG 22, CO 4.8 L/min, and CI of 2.48 L/min/m2 with a PVR of 4.5 WU. Following this, the patient underwent Impella 5.5 placement through the right axillary artery to optimize afterload reduction and improve end-organ perfusion. Post-Impella hemodynamics on milrinone 0.5 mcg/kg/min demonstrated the following: blood pressure 90/66 (74), heart rate 53/min, and PA pressure of 56/29, with a mean PA pressure of 38, PCWP 24, TPG 14, CO 6 L/min, and CI of 2.9 L/min/m2 with a PVR of 2.3 WU. CONCLUSION: Left ventricular assist device support with Impella 5.5 is associated with a reduction in mPAP and PVR over weeks to months and thus plays a crucial role as a bridge to transplant. Our case and this review highlights the characteristics of PH resulting from heart failure with reduced ejection fraction and discusses the important clinical issues related to the treatment of these patients. We have shown that left ventricular assist device therapy with Impella 5.5 can effectively reduce left-sided filling pressures and lead to PH improvement. We demonstrate the potential benefits of Impella 5.5 in the management of patients with WHO 2 PH and cardiogenic shock with impaired hemodynamics.

Mechanical Circulatory Support in COVID-19.

Despite aggressive care, patients with cardiopulmonary failure and COVID-19 experience unacceptably high mortality rates. The use of mechanical circulatory support devices in this population offers potential benefits but confers significant morbidity and novel challenges for the clinician. Thoughtful application of this complex technology is of the utmost importance and should be done in a multidisciplinary fashion by teams familiar with mechanical support devices and aware of the particular challenges provided by this complex patient population.

Mechanical stress-induced hemolysis of bovine blood is donor-dependent.

INTRODUCTION: In vitro hemolysis testing is an essential method for assessing the hemolytic potential of blood pumps, but has poor reproducibility. Further investigations are needed to determine the sources and extent of variability and to find a practical way to reduce the variation. METHODS: A small volume blood circulating loop driven by a Centrimag pump was established to provide relatively higher hemolysis readouts within a short run time and to be able to sequentially perform multiple repeated hemolysis tests in a working day. RESULTS: The repeatability with this system was demonstrated as the %RSD at 4.3% for the NIH or MIH from three repeated tests using the same blood. The bovine blood from different randomly selected donors was tested and gave more than a two-fold difference in NIH results (0.077 vs. 0.032 g/100 L) under the same testing conditions and same pump. This wide variation in hemolysis using bovine blood from different donors happened repeatedly. More importantly, it was observed that the difference in hemolysis test results using the blood drawn from the same donor on multiple days was narrow although the native hematocrits varied. The %RSD of NIH values obtained on five different days were 6.8%, 8.4%, 11.5%, and 7.8% for donor-specific blood from donors 1 to 4, respectively. CONCLUSION: The study results indicate that the mechanical stress-induced hemolysis behavior is donor-dependent. It has been also demonstrated that the reproducibility of in vitro hemolysis testing can be improved when the blood drawn from same donor is used.

In vitro thrombogenicity evaluation of rotary blood pumps by thromboelastometry.

In vitro thrombogenicity tests for rotary blood pumps (RBPs) could benefit from assessing coagulation kinematics, as RBP design improves. In this feasibility study, we investigated if the method of thromboelastometry (TEM) is able to assess coagulation kinematics under the in vitro conditions of RBP tests. We conducted in vitro thrombogenicity tests (n=4) by placing Deltastream® DP3 pumps into test loops that were filled with 150 mL of slightly anti-coagulated porcine blood, adjusted to an activated clotting time (ACT) well below clinically recommended levels. Blood samples were taken at certain time points during the experiment until a continuous decrease in pump flow indicated major thrombus formation. Blood samples were analyzed for ACT, platelet count (PLT), and several TEM parameters. While visible thrombus formation was observed in three pumps, ACT indicated an ongoing activation of coagulation, PLT might have indicated platelet consumption. Unexpectedly, most TEM results gave no clear indications. Nonetheless, TEM clotting time obtained by non-anticoagulated and chemically non-activated whole blood (HEPNATEM-CT) appeared to be more sensitive for the activation of coagulation in vitro than ACT, which might be of interest for future pump tests. However, more research regarding standardization of thrombogenicity pump tests is urgently required.

Complicaciones infecciosas relacionadas con la asistencia circulatoria mecánica de corta duración en candidatos a trasplante cardiaco urgente / Infectious complications associated with short-term mechanical circulatory support in urgent heart transplant candidates

Introducción y objetivos: El uso de dispositivos de asistencia circulatoria mecánica de corta duración como puente a trasplante es frecuente en España. Se desconocen la epidemiología y la repercusión de las complicaciones infecciosas en estos pacientes. Métodos: Descripción sistemática de la epidemiología y análisis de la repercusión pronóstica de las complicaciones infecciosas en un registro multicéntrico retrospectivo de pacientes tratados con dispositivos de asistencia circulatoria mecánica de corta duración como puente a trasplante cardiaco urgente entre 2010 y 2015 en 16 hospitales españoles. Resultados: Se estudió a 249 pacientes; 87 (34,9%) de ellos tuvieron un total de 102 infecciones. La vía respiratoria fue la localización más frecuente (n=47; 46,1%). En 78 casos (76,5%) se obtuvo confirmación microbiológica; se aislaron en total 100 gérmenes causales, con predominio de bacterias gramnegativas (n=58, 58%). Los pacientes con complicaciones infecciosas presentaron mayor mortalidad durante el periodo de asistencia circulatoria mecánica (el 25,3 frente al 12,3%; p=0,009) y menor probabilidad de recibir un trasplante (el 73,6 frente al 85,2%; p=0,025) que los pacientes sin infección. La mortalidad posoperatoria tras el trasplante fue similar en ambos grupos (con infección, el 28,3%; sin infección, el 23,4%; p=0,471). Conclusiones: Los pacientes tratados con dispositivos de asistencia circulatoria mecánica de corta duración como puente al trasplante cardiaco están expuestos a un alto riesgo de complicaciones infecciosas, las cuales se asocian con una mayor mortalidad en espera del órgano (AU)

Introduction and objectives: Short-term mechanical circulatory support is frequently used as a bridge to heart transplant in Spain. The epidemiology and prognostic impact of infectious complications in these patients are unknown. Methods: Systematic description of the epidemiology of infectious complications and analysis of their prognostic impact in a multicenter, retrospective registry of patients treated with short-term mechanical devices as a bridge to urgent heart transplant from 2010 to 2015 in 16 Spanish hospitals. Results: We studied 249 patients, of which 87 (34.9%) had a total of 102 infections. The most frequent site was the respiratory tract (n=47; 46.1%). Microbiological confirmation was obtained in 78 (76.5%) episodes, with a total of 100 causative agents, showing a predominance of gram-negative bacteria (n=58, 58%). Compared with patients without infection, those with infectious complications showed higher mortality during the support period (25.3% vs 12.3%, P=.009) and a lower probability of receiving a transplant (73.6% vs 85.2%, P=.025). In-hospital posttransplant mortality was similar in the 2 groups (with infection: 28.3%; without infection: 23.4%; P=.471). Conclusions: Patients supported with temporary devices as a bridge to heart transplant are exposed to a high risk of infectious complications, which are associated with higher mortality during the organ waiting period (AU)

Impact of gap size and groove design of hydrodynamic bearing on plasma skimming effect for use in rotary blood pump.

Plasma skimming can exclude red blood cells from high shear regions in the gaps formed by hydrodynamic bearings in rotary blood pumps. We investigated the effect of the gap size and groove design on the plasma skimming efficiency. Spiral groove bearings (SGBs) were installed into a specially designed test rig for in vitro experiments performed using human blood. The measured gap between the ridges of the bearing and the rotor surface was 17-26 µm at a flow rate of 150 ml/min and a rotor speed of 2400 rpm. Three different patterns of SGBs were designed (SGB-0, SGB-30, and SGB-60) with various degrees of the circumferential component. The hematocrit measured by a high-speed camera was compared with the hematocrit in the circuit, and the plasma skimming efficiency for the three bearing patterns was evaluated at hematocrits of 20%, 25%, and 30%. SGB-60, which had the strongest circumferential component, provided the best plasma skimming efficiency. When the gap size was less than 20 µm, the red blood cells in the gaps between the ridges of the bearing and rotor surface reduced significantly and the efficiency became higher than 90%. The gap size had the strongest effect on producing a significant plasma skimming. The plasma skimming efficiency can be significantly improved by optimizing the bearing gap size and groove design, which facilitates the further development of SGBs for use in applications such as rotary blood pumps.

Venoarterial extracorporeal membrane oxygenation is a viable option as a bridge to heart transplant.

OBJECTIVE: Venoarterial extracorporeal membrane oxygenation is a rescue therapy for patients in cardiogenic shock. We hypothesize that patients bridged to heart transplant with extracorporeal membrane oxygenation have decreased survival. METHODS: The United Network of Organ Sharing database was retrospectively reviewed from January 1, 1999, to March 31, 2018, for heart transplant recipients. Recipients bridged with any form of mechanical support and those without support were compared with recipients bridged with extracorporeal membrane oxygenation. The primary end point was restricted mean survival time through 16.7 years. RESULTS: Of 26,918 recipients, 15,076 required no pretransplant mechanical support (56.0%). Support patients included 9321 with left ventricular assist devices (34.6%), 53 with right ventricular assist devices (0.2%), 258 with total artificial hearts (1.0%), 686 with biventricular assist devices (2.6%), 1378 with intra-aortic balloon pumps (5.1%), and 146 who required extracorporeal membrane oxygenation (0.5%). In the first 16.7 years post-transplant, compared with recipients bridged with extracorporeal membrane oxygenation, estimated adjusted restricted mean survival time was higher in patients who required no mechanical support (16.6 months [14.0-19.4]) and patients with a left ventricular assist device (16.5 months [99% confidence interval, 13.9-19.2]), an intra-aortic balloon pump (11.2 months [8.3-14.7]), or a biventricular assist device (6.6 months [3.6-10.3]). Restricted mean survival time in patients with a right ventricular assist device or a total artificial heart was similar to patients with extracorporeal membrane oxygenation. CONCLUSIONS: Recipients bridged with extracorporeal membrane oxygenation were estimated to survive 16.6 months less than nonmechanical circulatory support recipients. Bridge to heart transplant with extracorporeal membrane oxygenation is a viable option, and these patients should be considered transplant candidates.

Blood Pumps for Extracorporeal Membrane Oxygenation: Platelet Activation During Different Operating Conditions.

Extracorporeal membrane oxygenation (ECMO) is a therapy used in severe cardiopulmonary failure. Blood is pumped through an artificial circuit exposing it to nonphysiologic conditions, which promote platelet activation and coagulation. Centrifugal pumps used at lower flow rates than their design point may lose pump efficiency and increase the risk of hemolysis. In this study, thrombogenic properties of two ECMO pumps designed for adult and neonatal use were evaluated using simulations in different flow scenarios. Three scenarios, adult pump in adult mode (4 L/min), adult pump in baby mode (300 ml/min), and neonatal pump used in its design point (300 ml/min), were simulated using computational fluid dynamics. The flow was numerically seeded with platelets, whose activation state was computed considering the stress history that acted along their respective path lines. Statistical distributions of activation state and residence time were drawn. The results showed that using the adult pump in baby mode increased the fraction of platelets with higher activation state confirming that low-pump flow rate impacts thrombogenicity. The neonatal pump showed a backflow at the inlet, which carried platelets in a retrograde motion contributing to an increased thrombogenic potential compared with the adult mode scenario.

Post-transplantation outcomes of sensitized patients receiving durable mechanical circulatory support.

BACKGROUND: Sensitization, defined as the presence of circulating antibodies, presents challenges, particularly in patients undergoing heart transplantation (HTx) bridged with durable mechanical circulatory support (MCS). We aimed to investigate the post-transplantation outcomes of sensitized MCS patients. METHODS: Among 889 consecutively enrolled heart transplant (HTx) recipients between 2010 and 2018, 86 (9.7%) sensitized MCS patients (Group A) were compared with sensitized non-MCS patients (Group B, n = 189), non-sensitized MCS patients (Group C, n = 162), and non-sensitized non-MCS patients (Group D, n = 452) regarding post-HTx outcomes, including the incidence of primary graft dysfunction (PGD), 1-year survival, and 1-year freedom from antibody-mediated rejection (AMR). RESULTS: Sensitized MCS patients (Group A) showed comparable rates of PGD, 1-year survival, and 1-year freedom from AMR with Groups C and D. However, Group A showed significantly higher rates of 1-year freedom from AMR (95.3% vs 85.7%, p = 0.02) and an earlier decline in panel-reactive antibody (PRA) levels (p < 0.01) than sensitized non-MCS patients (Group B). Desensitization therapy effectively reduced the levels of PRA in both Groups A and B. When Group A was further divided according to the presence of preformed donor-specific antibodies (DSA), patients with preformed DSA showed significantly lower rates of 1-year freedom from AMR than those without (84.2% vs 98.5%, p = 0.01). CONCLUSIONS: Sensitized MCS patients showed significantly lower rates of AMR and an earlier decline in PRA levels following HTx than sensitized non-MCS patients. Removal of MCS at the time of transplantation might underlie these observations.

Analysis of Plasma Skimming within a Hydrodynamic Bearing Gap for Designing Spiral Groove Bearings in Rotary Blood Pumps.

The blood damage problem inside the narrow hydrodynamic bearing is potentially considered to be solved by applying plasma skimming. However, the consideration of improving plasma skimming has not been included in the design of hydrodynamic bearings. The absence of experimental investigation on revealing the relationship between blood flow and plasma skimming in the bearing gap impedes the design of groove shape for plasma skimming. Thus, the present study was undertaken to evaluate how the blood flow direction and the groove shape affect plasma skimming in the bearing gap. To this end, blood tests using porcine blood were repeated three times with a hematocrit of 0.8%. The bearing gap during the tests was adjusted to 25 µm and the rotational speed was adjusted from 50 rpm to 2500 rpm. The blood flow and plasma skimming effect was evaluated based on image analysis utilizing a high-speed microscope. Results of three tests indicated that the flow direction of RBCs was dominated by the rotating surface in the bearing gap when the rotational speed increased over 1200 rpm. The best plasma skimming effect was observed when the angle between the flow direction of RBCs and the tangent line of the groove was within -10 degrees to 10 degrees. The future study will be conducted with including the consideration of plasma skimming in the bearing shape design. The findings in this study aid the future design and development of hydrodynamic bearing for use in rotary blood pumps.

Applicability of Narrow Groove Theory in Designing Washout Features for Rotary Blood Pumps.

High and low shear regions in rotary blood pumps require sufficient washout flow to minimize blood residence time, thereby preventing hemolysis or regions of stasis that can lead to pump thrombosis. Spiral groove bearings (SGBs) both enhance pump washout and reduce erythrocyte exposure to high shear. Narrow groove theory (NGT) has been used as an analytical tool to estimate the flow performance of a flat SGB during the design stage. However, NGT cannot accurately predict the performance of a conical SGB. In this study, we formulated an analytical model from the established NGT by adding an inertia correction term to incorporate variations in centrifugal force, which improved washout prediction in a conical SGB. The modified NGT model was then validated by comparison with experimental results. The results show that the modified NFT analytical model can reasonably predict washout rate when the spiral groove geometry favors creep flow conditions. The conical half angle of the SGB had the most significant impact on washout, with a decrease in half angle leading to large increases in wash-out flow. Small half angles also maintained viscous pumping at larger Reynolds numbers. In summary, the modified NGT can be a useful tool for designing conical SGBs for rotary blood pump washout within the creep flow regime.

Predicting Major Adverse Cardiovascular Events in Children With Age-Adjusted NT-proBNP.

BACKGROUND: N-terminal pro-B-type natriuretic peptide (NT-proBNP) is frequently used as a valuable prognostic biomarker in cardiac diseases. In children, however, it has not been established because of its strong age dependency. To overcome this obstacle, we recently introduced the zlog value of N-terminal pro-B-type natriuretic peptide (zlog-proBNP) as an age-adjusted reference. OBJECTIVES: This study evaluates the prognostic power of zlog-proBNP for the occurrence of major adverse cardiovascular events (MACE) throughout childhood in patients with congenital heart diseases (CHD). METHODS: A total of 910 children with CHD (median age 5 months; range 0.0-18.0 years) were included. MACE was defined as death, resuscitation, mechanical circulatory support, or hospitalization caused by cardiac decompensation. Because the physiological NT-proBNP concentration decreases significantly during childhood, zlog values were applied for an age-independent evaluation. RESULTS: MACE occurred in 138 children during a median follow-up of 6 months (range 1 day to 7.6 years). High zlog-proBNP values (>+3.0) were most strongly associated with adverse events (n = 93; adjusted HR: 21.1; 95% CI: 2.9-154.2; P < 0.001). Among all evaluated indicators, zlog-proBNP was the best predictor for MACE (adjusted HR: 1.52; 95% CI: 1.31-1.76; P < 0.001) along with age and predictively superior to absolute NT-proBNP values. A cutoff value of +1.96 (age-independent upper limit of the physiological NT-proBNP concentration) achieved a negative predictive value of >96%. CONCLUSIONS: Zlog-proBNP overcomes the strong age dependency of NT-proBNP and is a powerful prognostic marker for age-independent exclusion and prediction of MACE in children with CHD. We therefore expect zlog-proBNP to play a pivotal role in the future management of children with heart diseases.